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SMT/Solder Paste Question

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  • jstockma
    I am planning the build of an Ensemble RX and I am thinking of trying the griddle-heat gun reflow method to install the SMT parts. As far as blocking out time
    Message 1 of 18 , Apr 17, 2014
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      I am planning the build of an Ensemble RX and I am thinking of trying the griddle-heat gun reflow method to install the SMT parts. As far as blocking out time to apply the solder paste and place individual parts, how long can one let the applied parts stand without reflow? I would like to break the placement process up over several days but I am worried that the solder paste will separate or otherwise degrade if I don't place all the parts and reflow them in the same session. Can the process be broken up over a period of days or even a couple of weeks without ruining the already placed parts? 
      John Stockman, KC2THY

    • Silverfox
      It can be done but it requires a temperature controlled heat source so that the solder only melts enough to maintain the colloidal effect to keep the
      Message 2 of 18 , Apr 17, 2014
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        It can be done but it requires a temperature controlled heat source so that the solder only melts enough to maintain the colloidal effect to keep the previously soldered parts from moving.  This is not so difficult with all the parts on one side of the PCB.  Doing both sides requires more attention to the details.

        73,

        Alan - W6ARH

        This is based on a couple of attempts with a simple inexpensive board.

         

         

        From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of jcs1@...
        Sent: Thursday, April 17, 2014 6:54 PM
        To: softrock40@yahoogroups.com
        Subject: [softrock40] SMT/Solder Paste Question

         

         

        I am planning the build of an Ensemble RX and I am thinking of trying the griddle-heat gun reflow method to install the SMT parts. As far as blocking out time to apply the solder paste and place individual parts, how long can one let the applied parts stand without reflow? I would like to break the placement process up over several days but I am worried that the solder paste will separate or otherwise degrade if I don't place all the parts and reflow them in the same session. Can the process be broken up over a period of days or even a couple of weeks without ruining the already placed parts? 

        John Stockman, KC2THY

         

      • Cecil Bayona
        From personal experience I ve had no problems with putting the paste and parts and then soldering a few days later, what happened was that some of the binding
        Message 3 of 18 , Apr 17, 2014
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          From personal experience I've had no problems with putting the
          paste and parts and then soldering a few days later, what happened
          was that some of the binding oil evaporated but the parts were held
          in place by the dried out paste. When placed in the oven the parts
          were soldered OK.

          It would not be OK if you put the paste but not the parts, when you
          go to put in the parts later they would not stick to the pad.

          At 08:53 PM 4/17/2014, you wrote:
          >
          >
          >I am planning the build of an Ensemble RX and I am thinking of
          >trying the griddle-heat gun reflow method to install the SMT parts.
          >As far as blocking out time to apply the solder paste and place
          >individual parts, how long can one let the applied parts stand
          >without reflow? I would like to break the placement process up over
          >several days but I am worried that the solder paste will separate or
          >otherwise degrade if I don't place all the parts and reflow them in
          >the same session. Can the process be broken up over a period of days
          >or even a couple of weeks without ruining the already placed parts?
          >John Stockman, KC2THY

          --
          Cecil - k5nwa
          < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

          Never take life seriously. Nobody gets out alive anyway.
        • w2bvh
          At work they sometimes put boards with paste, without parts, in a small closed plastic box overnight (end of shift to start of shift) and it works out ok. They
          Message 4 of 18 , Apr 17, 2014
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            At work they sometimes put boards with paste, without parts, in a small closed plastic box overnight (end of shift to start of shift) and it works out ok. They usually store it in a dry nitrogen box, but I don't think that really matters too much.

            GL & 73,
            Lenny W2BVH


            On 4/17/2014 9:53 PM, jcs1@... wrote:
             

            I am planning the build of an Ensemble RX and I am thinking of trying the griddle-heat gun reflow method to install the SMT parts. As far as blocking out time to apply the solder paste and place individual parts, how long can one let the applied parts stand without reflow? I would like to break the placement process up over several days but I am worried that the solder paste will separate or otherwise degrade if I don't place all the parts and reflow them in the same session. Can the process be broken up over a period of days or even a couple of weeks without ruining the already placed parts? 

            John Stockman, KC2THY


          • Jean-Paul Louis
            Cecil, YouÆre playing with fire when you wait for reflow, The solder paste is VERY sensitive to moisture, and the flux evaporate fairly fast. So, you end up
            Message 5 of 18 , Apr 17, 2014
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              Cecil,

              You’re playing with fire when you wait for reflow,
              The solder paste is VERY sensitive to moisture, and the flux evaporate fairly fast.
              So, you end up with crusty paste that might hold the parts a bit, but you are
              almost certain to create cold solder joints, and tons of solder balls.
              At all the places I have worked, 6 hours was the shelf life of a board with solder paste and parts.
              Past that time, the PCB was washed and recycled because it was the most expensive part.
              The paste and the inexpensive parts were trashed. Some (very few) very expensive ICs were recycled.

              I understand the hobbyist viewpoint, but please don’t suggest that it is an acceptable practice.

              I would suggest to place a few parts and reflow them, then you can wait, then add fresh solder paste, place parts
              and reflow those.
              Too many reflows are not good for ICs, but 3 to 4 is OK.
              So you can limit the number of reflows by adding heat screens on your board for the parts already soldered
              (aluminum foil makes a good screen)

              My $0.02

              Jean-Paul (AC9GH)


              On Apr 17, 2014, at 11:03 PM, Cecil Bayona <cbayona@...> wrote:

              From personal experience I've had no problems with putting the 
              paste and parts and then soldering a few days later, what happened 
              was that some of the binding oil evaporated but the parts were held 
              in place by the dried out paste. When placed in the oven the parts 
              were soldered OK.

              It would not be OK if you put the paste but not the parts, when you 
              go to put in the parts later they would not stick to the pad.

              At 08:53 PM 4/17/2014, you wrote:
              >
              >
              >I am planning the build of an Ensemble RX and I am thinking of 
              >trying the griddle-heat gun reflow method to install the SMT parts. 
              >As far as blocking out time to apply the solder paste and place 
              >individual parts, how long can one let the applied parts stand 
              >without reflow? I would like to break the placement process up over 
              >several days but I am worried that the solder paste will separate or 
              >otherwise degrade if I don't place all the parts and reflow them in 
              >the same session. Can the process be broken up over a period of days 
              >or even a couple of weeks without ruining the already placed parts?
              >John Stockman, KC2THY

              -- 
              Cecil - k5nwa
              < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

              Never take life seriously. Nobody gets out alive anyway. 


            • Jean-Paul Louis
              Lenny, While I was working, I spent a lot of money in studies of the reflow process, and what you suggest is not as bad as what Cecil suggest, but it is not
              Message 6 of 18 , Apr 17, 2014
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                Lenny,

                While I was working, I spent a lot of money in studies of the reflow process, and
                what you suggest is not as bad as what Cecil suggest, but it is not good unless
                you wash the moisture of the boards with nitrogen, and seal the bags. 
                then you might be ok for overnight wait, but it is still risky.
                I do not understand why they would want to keep PSB with paste and no parts.
                It is cheaper to just clean the PCB with a Isopropyl Alcohol, then you can wait overnight
                without any dry pack and nitrogen, and recycle it on the next morning.

                I suggest that any paste on the board be reflowed in the next two hours.
                So for hobby work, paste a few areas, add the parts, reflow, let cool, then you can wait
                a bit for the next batch of parts. See my reply to Cecil for heat screen.

                Jean-Paul

                On Apr 18, 2014, at 12:03 AM, w2bvh <w2bvh@...> wrote:


                At work they sometimes put boards with paste, without parts, in a small closed plastic box overnight (end of shift to start of shift) and it works out ok. They usually store it in a dry nitrogen box, but I don't think that really matters too much.

                GL & 73,
                Lenny W2BVH


                On 4/17/2014 9:53 PM, jcs1@... wrote:
                 

                I am planning the build of an Ensemble RX and I am thinking of trying the griddle-heat gun reflow method to install the SMT parts. As far as blocking out time to apply the solder paste and place individual parts, how long can one let the applied parts stand without reflow? I would like to break the placement process up over several days but I am worried that the solder paste will separate or otherwise degrade if I don't place all the parts and reflow them in the same session. Can the process be broken up over a period of days or even a couple of weeks without ruining the already placed parts? 

                John Stockman, KC2THY




              • Cecil Bayona
                I have never experienced the results you mentioned, but I keep your information in mind, I don t postpone the soldering phase often. I did it a couple of times
                Message 7 of 18 , Apr 17, 2014
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                  I have never experienced the results you mentioned, but I keep your
                  information in mind, I don't postpone the soldering phase often.

                  I did it a couple of times because after putting some of the parts
                  and emergency came up and had to abort. I placed the board in a zip
                  locked bag in the refrigerator and continued the next day. As a norm
                  I very slowly ramp the preheat temperature precisely to get rid of
                  moisture. On those boards I did a very long and slow warm up cycle
                  since the boards were cold, all the joints were soldered just fine.

                  Soldering paste doesn't have a very long life in commercial outfits
                  but using manual paste application I have solder paste that work
                  quite well after two years, the commercial environment requires the
                  paste density to be in a very strict range in order to be
                  automatically applied, manual procedures can accept a larger variance.

                  I did one experiment where I place a partial parts count and
                  re-flowed the board, I then did it an additional two times and was
                  surprised that the components were all fine after some of them were
                  re-flowed three times, since then I've read some have done as many as
                  six times but I think you are pushing your luck doing it that many times.

                  I've bought the components to make an automatic controller for my
                  Infrawave Oven once that is done then repeatability will improve, and
                  I can work on other boards while the first batch is proceeding on
                  auto pilot. I'm thinking of using it for commercial projects.

                  At 11:35 PM 4/17/2014, you wrote:
                  >Cecil,
                  >
                  >You're playing with fire when you wait for reflow,
                  >The solder paste is VERY sensitive to moisture, and the flux
                  >evaporate fairly fast.
                  >So, you end up with crusty paste that might hold the parts a bit, but you are
                  >almost certain to create cold solder joints, and tons of solder balls.
                  >At all the places I have worked, 6 hours was the shelf life of a
                  >board with solder paste and parts.
                  >Past that time, the PCB was washed and recycled because it was the
                  >most expensive part.
                  >The paste and the inexpensive parts were trashed. Some (very few)
                  >very expensive ICs were recycled.
                  >
                  >I understand the hobbyist viewpoint, but please don't suggest that
                  >it is an acceptable practice.
                  >
                  >I would suggest to place a few parts and reflow them, then you can
                  >wait, then add fresh solder paste, place parts
                  >and reflow those.
                  >Too many reflows are not good for ICs, but 3 to 4 is OK.
                  >So you can limit the number of reflows by adding heat screens on
                  >your board for the parts already soldered
                  >(aluminum foil makes a good screen)
                  >
                  >My $0.02
                  >
                  >Jean-Paul (AC9GH)
                  >
                  >
                  >On Apr 17, 2014, at 11:03 PM, Cecil Bayona
                  ><<mailto:cbayona@...>cbayona@...> wrote:
                  >
                  >> From personal experience I've had no problems with putting the
                  >>paste and parts and then soldering a few days later, what happened
                  >>was that some of the binding oil evaporated but the parts were held
                  >>in place by the dried out paste. When placed in the oven the parts
                  >>were soldered OK.
                  >>
                  >>It would not be OK if you put the paste but not the parts, when you
                  >>go to put in the parts later they would not stick to the pad.
                  >>
                  >>At 08:53 PM 4/17/2014, you wrote:
                  >> >
                  >> >
                  >> >I am planning the build of an Ensemble RX and I am thinking of
                  >> >trying the griddle-heat gun reflow method to install the SMT parts.
                  >> >As far as blocking out time to apply the solder paste and place
                  >> >individual parts, how long can one let the applied parts stand
                  >> >without reflow? I would like to break the placement process up over
                  >> >several days but I am worried that the solder paste will separate or
                  >> >otherwise degrade if I don't place all the parts and reflow them in
                  >> >the same session. Can the process be broken up over a period of days
                  >> >or even a couple of weeks without ruining the already placed parts?
                  >> >John Stockman, KC2THY
                  >>
                  >>--
                  >>Cecil - k5nwa
                  >><
                  >><http://thepartsplace.k5nwa.com/>http://thepartsplace.k5nwa.com/ >
                  >>< http://www.softrockradio.org/ >
                  >>
                  >>Never take life seriously. Nobody gets out alive anyway.
                  >

                  --
                  Cecil - k5nwa
                  < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

                  Never take life seriously. Nobody gets out alive anyway.
                • John Greusel
                  John, It doesn t take that long- maybe an hour to do all the parts. I wouldn t bother with spreading it out over days. John KC9OJV  
                  Message 8 of 18 , Apr 18, 2014
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                    John,

                    It doesn't take that long- maybe an hour to do all the parts. I wouldn't bother with spreading it out over days.

                    John
                    KC9OJV
                     



                    From: Jean-Paul Louis <louijp@...>
                    To: softrock40@yahoogroups.com
                    Sent: Thursday, April 17, 2014 11:49 PM
                    Subject: Re: [softrock40] SMT/Solder Paste Question

                    Lenny,

                    While I was working, I spent a lot of money in studies of the reflow process, and
                    what you suggest is not as bad as what Cecil suggest, but it is not good unless
                    you wash the moisture of the boards with nitrogen, and seal the bags. 
                    then you might be ok for overnight wait, but it is still risky.
                    I do not understand why they would want to keep PSB with paste and no parts.
                    It is cheaper to just clean the PCB with a Isopropyl Alcohol, then you can wait overnight
                    without any dry pack and nitrogen, and recycle it on the next morning.

                    I suggest that any paste on the board be reflowed in the next two hours.
                    So for hobby work, paste a few areas, add the parts, reflow, let cool, then you can wait
                    a bit for the next batch of parts. See my reply to Cecil for heat screen.

                    Jean-Paul

                    On Apr 18, 2014, at 12:03 AM, w2bvh <w2bvh@...> wrote:


                    At work they sometimes put boards with paste, without parts, in a small closed plastic box overnight (end of shift to start of shift) and it works out ok. They usually store it in a dry nitrogen box, but I don't think that really matters too much.

                    GL & 73,
                    Lenny W2BVH


                    On 4/17/2014 9:53 PM, jcs1@... wrote:
                     
                    I am planning the build of an Ensemble RX and I am thinking of trying the griddle-heat gun reflow method to install the SMT parts. As far as blocking out time to apply the solder paste and place individual parts, how long can one let the applied parts stand without reflow? I would like to break the placement process up over several days but I am worried that the solder paste will separate or otherwise degrade if I don't place all the parts and reflow them in the same session. Can the process be broken up over a period of days or even a couple of weeks without ruining the already placed parts? 
                    John Stockman, KC2THY






                  • John Stockman
                    Thank you all, I will plan to do it all in one session. Solder paste is new to me. John Stockman, KC2THY Sent from my Verizon Wireless 4G LTE DROID Jean-Paul
                    Message 9 of 18 , Apr 18, 2014
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                      Thank you all, I will plan to do it all in one session. Solder paste is new to me.
                      John Stockman, KC2THY

                      Sent from my Verizon Wireless 4G LTE DROID


                      Jean-Paul Louis <louijp@...> wrote:

                      Cecil,

                      You’re playing with fire when you wait for reflow,
                      The solder paste is VERY sensitive to moisture, and the flux evaporate fairly fast.
                      So, you end up with crusty paste that might hold the parts a bit, but you are
                      almost certain to create cold solder joints, and tons of solder balls.
                      At all the places I have worked, 6 hours was the shelf life of a board with solder paste and parts.
                      Past that time, the PCB was washed and recycled because it was the most expensive part.
                      The paste and the inexpensive parts were trashed. Some (very few) very expensive ICs were recycled.

                      I understand the hobbyist viewpoint, but please don’t suggest that it is an acceptable practice.

                      I would suggest to place a few parts and reflow them, then you can wait, then add fresh solder paste, place parts
                      and reflow those.
                      Too many reflows are not good for ICs, but 3 to 4 is OK.
                      So you can limit the number of reflows by adding heat screens on your board for the parts already soldered
                      (aluminum foil makes a good screen)

                      My $0.02

                      Jean-Paul (AC9GH)


                      On Apr 17, 2014, at 11:03 PM, Cecil Bayona <cbayona@...> wrote:

                      From personal experience I've had no problems with putting the 
                      paste and parts and then soldering a few days later, what happened 
                      was that some of the binding oil evaporated but the parts were held 
                      in place by the dried out paste. When placed in the oven the parts 
                      were soldered OK.

                      It would not be OK if you put the paste but not the parts, when you 
                      go to put in the parts later they would not stick to the pad.

                      At 08:53 PM 4/17/2014, you wrote:
                      >
                      >
                      >I am planning the build of an Ensemble RX and I am thinking of 
                      >trying the griddle-heat gun reflow method to install the SMT parts. 
                      >As far as blocking out time to apply the solder paste and place 
                      >individual parts, how long can one let the applied parts stand 
                      >without reflow? I would like to break the placement process up over 
                      >several days but I am worried that the solder paste will separate or 
                      >otherwise degrade if I don't place all the parts and reflow them in 
                      >the same session. Can the process be broken up over a period of days 
                      >or even a couple of weeks without ruining the already placed parts?
                      >John Stockman, KC2THY

                      -- 
                      Cecil - k5nwa
                      < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

                      Never take life seriously. Nobody gets out alive anyway. 


                    • William H. Fite
                      Lots of voodoo surrounding solder paste. Experienced industry people give madly conflicting advice including the sacrifice of a live chicken to assure good
                      Message 10 of 18 , Apr 18, 2014
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                        Lots of voodoo surrounding solder paste.  Experienced industry people give madly conflicting advice including the sacrifice of a live chicken to assure good joints. 
                         
                        John's advice is best.  Do it all at once.
                         
                        Have a whimsical weekend, everyone!
                         
                        Bill
                        KJ4SLP


                        On Fri, Apr 18, 2014 at 8:33 AM, John Stockman <jcs1@...> wrote:
                         

                        Thank you all, I will plan to do it all in one session. Solder paste is new to me.
                        John Stockman, KC2THY

                        Sent from my Verizon Wireless 4G LTE DROID


                        Jean-Paul Louis <louijp@...> wrote:

                        Cecil,

                        You’re playing with fire when you wait for reflow,
                        The solder paste is VERY sensitive to moisture, and the flux evaporate fairly fast.
                        So, you end up with crusty paste that might hold the parts a bit, but you are
                        almost certain to create cold solder joints, and tons of solder balls.
                        At all the places I have worked, 6 hours was the shelf life of a board with solder paste and parts.
                        Past that time, the PCB was washed and recycled because it was the most expensive part.
                        The paste and the inexpensive parts were trashed. Some (very few) very expensive ICs were recycled.

                        I understand the hobbyist viewpoint, but please don’t suggest that it is an acceptable practice.

                        I would suggest to place a few parts and reflow them, then you can wait, then add fresh solder paste, place parts
                        and reflow those.
                        Too many reflows are not good for ICs, but 3 to 4 is OK.
                        So you can limit the number of reflows by adding heat screens on your board for the parts already soldered
                        (aluminum foil makes a good screen)

                        My $0.02

                        Jean-Paul (AC9GH)


                        On Apr 17, 2014, at 11:03 PM, Cecil Bayona <cbayona@...> wrote:

                        From personal experience I've had no problems with putting the 
                        paste and parts and then soldering a few days later, what happened 
                        was that some of the binding oil evaporated but the parts were held 
                        in place by the dried out paste. When placed in the oven the parts 
                        were soldered OK.

                        It would not be OK if you put the paste but not the parts, when you 
                        go to put in the parts later they would not stick to the pad.

                        At 08:53 PM 4/17/2014, you wrote:
                        >
                        >
                        >I am planning the build of an Ensemble RX and I am thinking of 
                        >trying the griddle-heat gun reflow method to install the SMT parts. 
                        >As far as blocking out time to apply the solder paste and place 
                        >individual parts, how long can one let the applied parts stand 
                        >without reflow? I would like to break the placement process up over 
                        >several days but I am worried that the solder paste will separate or 
                        >otherwise degrade if I don't place all the parts and reflow them in 
                        >the same session. Can the process be broken up over a period of days 
                        >or even a couple of weeks without ruining the already placed parts?
                        >John Stockman, KC2THY

                        -- 
                        Cecil - k5nwa
                        < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

                        Never take life seriously. Nobody gets out alive anyway. 





                        --
                        I can explain it for you, but I can't comprehend it for you.
                      • Jean-Paul Louis
                        Hi Cecil, I see that you were very careful andtook precautions that were not mentioned in your previous email. The ziplock bag in the fridge probably saved
                        Message 11 of 18 , Apr 18, 2014
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                          Hi Cecil,

                          I see that you were very careful andtook precautions that were not mentioned in your previous
                          email. The ziplock bag in the fridge probably saved your day, as well as the
                          temperature soaking time.
                          At work, we used solder paste in 500g jars, and any open jar that was not used in a shift was trashed.
                          But that was Telecom manufacturing were reliability and quality are a few of prime requirements.
                          I agree with you, six reflows is pushing your luck.

                          But we need also to be positive about SMT. This technology is way easier and way better than the now
                          very old thus mature TH technology.

                          Hams need not to be scared by those tiny parts. With simple care, they solder easily, and make DIY a
                          lot of fun. That’s why, since I retired, I design SDR stuff, and in a not too distant future, I will introduce
                          what I see as the next wave in term of SDR Rx/Tx and Test instruments.

                          73 de
                          Jean-Paul
                          AC9GH @ EN61vr99





                          On Apr 18, 2014, at 1:16 AM, Cecil Bayona <cbayona@...> wrote:

                          I have never experienced the results you mentioned, but I keep your 
                          information in mind, I don't postpone the soldering phase often.

                          I did it a couple of times because after putting some of the parts 
                          and emergency came up and had to abort. I placed the board in a zip 
                          locked bag in the refrigerator and continued the next day. As a norm 
                          I very slowly ramp the preheat temperature precisely to get rid of 
                          moisture. On those boards I did a very long and slow warm up cycle 
                          since the boards were cold, all the joints were soldered just fine.

                          Soldering paste doesn't have a very long life in commercial outfits 
                          but using manual paste application I have solder paste that work 
                          quite well after two years, the commercial environment requires the 
                          paste density to be in a very strict range in order to be 
                          automatically applied, manual procedures can accept a larger variance.

                          I did one experiment where I place a partial parts count and 
                          re-flowed the board, I then did it an additional two times and was 
                          surprised that the components were all fine after some of them were 
                          re-flowed three times, since then I've read some have done as many as 
                          six times but I think you are pushing your luck doing it that many times.

                          I've bought the components to make an automatic controller for my 
                          Infrawave Oven once that is done then repeatability will improve, and 
                          I can work on other boards while the first batch is proceeding on 
                          auto pilot. I'm thinking of using it for commercial projects.

                          At 11:35 PM 4/17/2014, you wrote:
                          >Cecil,
                          >
                          >You're playing with fire when you wait for reflow,
                          >The solder paste is VERY sensitive to moisture, and the flux 
                          >evaporate fairly fast.
                          >So, you end up with crusty paste that might hold the parts a bit, but you are
                          >almost certain to create cold solder joints, and tons of solder balls.
                          >At all the places I have worked, 6 hours was the shelf life of a 
                          >board with solder paste and parts.
                          >Past that time, the PCB was washed and recycled because it was the 
                          >most expensive part.
                          >The paste and the inexpensive parts were trashed. Some (very few) 
                          >very expensive ICs were recycled.
                          >
                          >I understand the hobbyist viewpoint, but please don't suggest that 
                          >it is an acceptable practice.
                          >
                          >I would suggest to place a few parts and reflow them, then you can 
                          >wait, then add fresh solder paste, place parts
                          >and reflow those.
                          >Too many reflows are not good for ICs, but 3 to 4 is OK.
                          >So you can limit the number of reflows by adding heat screens on 
                          >your board for the parts already soldered
                          >(aluminum foil makes a good screen)
                          >
                          >My $0.02
                          >
                          >Jean-Paul (AC9GH)
                          >
                          >
                          >On Apr 17, 2014, at 11:03 PM, Cecil Bayona 
                          ><<mailto:cbayona@...>cbayona@...> wrote:
                          >
                          >> From personal experience I've had no problems with putting the
                          >>paste and parts and then soldering a few days later, what happened
                          >>was that some of the binding oil evaporated but the parts were held
                          >>in place by the dried out paste. When placed in the oven the parts
                          >>were soldered OK.
                          >>
                          >>It would not be OK if you put the paste but not the parts, when you
                          >>go to put in the parts later they would not stick to the pad.
                          >>
                          >>At 08:53 PM 4/17/2014, you wrote:
                          >> >
                          >> >
                          >> >I am planning the build of an Ensemble RX and I am thinking of
                          >> >trying the griddle-heat gun reflow method to install the SMT parts.
                          >> >As far as blocking out time to apply the solder paste and place
                          >> >individual parts, how long can one let the applied parts stand
                          >> >without reflow? I would like to break the placement process up over
                          >> >several days but I am worried that the solder paste will separate or
                          >> >otherwise degrade if I don't place all the parts and reflow them in
                          >> >the same session. Can the process be broken up over a period of days
                          >> >or even a couple of weeks without ruining the already placed parts?
                          >> >John Stockman, KC2THY
                          >>
                          >>--
                          >>Cecil - k5nwa
                          >>< 
                          >><http://thepartsplace.k5nwa.com/>http://thepartsplace.k5nwa.com/ > 
                          >>< http://www.softrockradio.org/ >
                          >>
                          >>Never take life seriously. Nobody gets out alive anyway.
                          >

                          -- 
                          Cecil - k5nwa
                          < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

                          Never take life seriously. Nobody gets out alive anyway. 


                        • Doug Luurs
                          So that s what I m doing wrong .. I m forgetting the live chicken sacrifice *Snickers* Doug / W8ZUU From: softrock40@yahoogroups.com
                          Message 12 of 18 , Apr 18, 2014
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                            So that’s what I’m doing wrong .. I’m forgetting the live chicken sacrifice *Snickers*

                             

                            Doug / W8ZUU

                             

                            From: softrock40@yahoogroups.com [mailto:softrock40@yahoogroups.com] On Behalf Of William H. Fite
                            Sent: Friday, April 18, 2014 10:11 AM
                            To: softrock40@yahoogroups.com
                            Subject: Re: [softrock40] SMT/Solder Paste Question

                             

                             

                            Lots of voodoo surrounding solder paste.  Experienced industry people give madly conflicting advice including the sacrifice of a live chicken to assure good joints. 

                             

                            John's advice is best.  Do it all at once.

                             

                            Have a whimsical weekend, everyone!

                             

                            Bill

                            KJ4SLP

                             

                            On Fri, Apr 18, 2014 at 8:33 AM, John Stockman <jcs1@...> wrote:

                             

                            Thank you all, I will plan to do it all in one session. Solder paste is new to me.

                            John Stockman, KC2THY

                             

                            Sent from my Verizon Wireless 4G LTE DROID



                            Jean-Paul Louis <louijp@...> wrote:

                            Cecil,

                             

                            You’re playing with fire when you wait for reflow,

                            The solder paste is VERY sensitive to moisture, and the flux evaporate fairly fast.

                            So, you end up with crusty paste that might hold the parts a bit, but you are

                            almost certain to create cold solder joints, and tons of solder balls.

                            At all the places I have worked, 6 hours was the shelf life of a board with solder paste and parts.

                            Past that time, the PCB was washed and recycled because it was the most expensive part.

                            The paste and the inexpensive parts were trashed. Some (very few) very expensive ICs were recycled.

                             

                            I understand the hobbyist viewpoint, but please don’t suggest that it is an acceptable practice.

                             

                            I would suggest to place a few parts and reflow them, then you can wait, then add fresh solder paste, place parts

                            and reflow those.

                            Too many reflows are not good for ICs, but 3 to 4 is OK.

                            So you can limit the number of reflows by adding heat screens on your board for the parts already soldered

                            (aluminum foil makes a good screen)

                             

                            My $0.02

                             

                            Jean-Paul (AC9GH)

                             

                             

                            On Apr 17, 2014, at 11:03 PM, Cecil Bayona <cbayona@...> wrote:

                             

                            From personal experience I've had no problems with putting the 
                            paste and parts and then soldering a few days later, what happened 
                            was that some of the binding oil evaporated but the parts were held 
                            in place by the dried out paste. When placed in the oven the parts 
                            were soldered OK.

                            It would not be OK if you put the paste but not the parts, when you 
                            go to put in the parts later they would not stick to the pad.

                            At 08:53 PM 4/17/2014, you wrote:
                            >
                            >
                            >I am planning the build of an Ensemble RX and I am thinking of 
                            >trying the griddle-heat gun reflow method to install the SMT parts. 
                            >As far as blocking out time to apply the solder paste and place 
                            >individual parts, how long can one let the applied parts stand 
                            >without reflow? I would like to break the placement process up over 
                            >several days but I am worried that the solder paste will separate or 
                            >otherwise degrade if I don't place all the parts and reflow them in 
                            >the same session. Can the process be broken up over a period of days 
                            >or even a couple of weeks without ruining the already placed parts?
                            >John Stockman, KC2THY

                            -- 
                            Cecil - k5nwa
                            http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

                            Never take life seriously. Nobody gets out alive anyway. 

                             




                            --
                            I can explain it for you, but I can't comprehend it for you.

                          • MICHAEL TALLENT
                            My first surface mount build was an RXTX and I used small solder and a very fine tip. My second surface mount build was the RX II. I got the solder paste
                            Message 13 of 18 , Apr 18, 2014
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                              My first surface mount build was an RXTX and I used small solder and a very fine tip.  My second surface mount build was the RX II.  I got the solder paste from KD5SSJ and a Mr. Coffee cup warmer from Wal-Mart to pre-heat the board and a Martha Stewart heat embossing tool from the Hobby store.  I was not going to build the LF version so I marked the parts not used and put a small dap of paste on all the pads used.  I then mounted all the parts, there are not that many parts.  set the board on an aluminum spacer on the cup warmer, plugged it in and waited about 25 minutes until it got to about 85 degrees C.  I then started the heat tool and held it about 4-6 inches above the board and slowly moved it around and around and then started to slowly move it closer watching for the paste to melt.  When the paste melted it turned very shiny and all the parts centered themselves on the pads, amazing.  I then slowly moved the heat away while still moving it around then I turned off the cup warmer and let it sit for about 30 minutes.  Probably took less than 2 hours including the cool down.  If you use a method like this I would only do the heating ONCE as it is not very well controlled heat.  If you have a nice temperature controlled programmed heat oven then maybe heating several times would be OK.  But with so few parts to install I don’t see the reason for breaking up the assembly of the surface mount parts.  I am 72 and it was my first surface mount assembly, although I do design and build a lot of electronics.
                               
                              Mike  W6MXV
                               
                              From: jcs1@...
                              Sent: Thursday, April 17, 2014 9:53 PM
                              Subject: [softrock40] SMT/Solder Paste Question
                               


                              I am planning the build of an Ensemble RX and I am thinking of trying the griddle-heat gun reflow method to install the SMT parts. As far as blocking out time to apply the solder paste and place individual parts, how long can one let the applied parts stand without reflow? I would like to break the placement process up over several days but I am worried that the solder paste will separate or otherwise degrade if I don't place all the parts and reflow them in the same session. Can the process be broken up over a period of days or even a couple of weeks without ruining the already placed parts? 
                              John Stockman, KC2THY
                               
                            • Cecil Bayona
                              A long time ago I was like many convinced by many rumors of how difficult SMT work was, it turned out to be nay say from persons that probably never even tried
                              Message 14 of 18 , Apr 18, 2014
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                                A long time ago I was like many convinced by many rumors of how
                                difficult SMT work was, it turned out to be nay say from persons that
                                probably never even tried it.

                                My first attempt at it was a total disaster , my PCB caught fire. The
                                problem was an oven with horrendous thermal inertial, and a
                                thermometer that was both inaccurate and slow to respond to the real
                                temperature. After that attempt I though about what happened and
                                adjusted the procedure coupled with visual observation, and several
                                dry runs while monitoring the temperatures with a faster thermometer
                                I then went and tried another board and it came out perfect. Since
                                then when I can I make a project use SMT components as I found it
                                easier to work with than leaded components. I've also tried using a
                                embossing air gun and that worked well for building, repairing, and
                                salvaging components.

                                Once I get my oven controller going then it will be even easier as
                                all the timing and temperature monitoring will be automatic, I have
                                an old controller but I'm not happy with it, that is why I want to
                                build a better one using better thermocouple amplifiers and A/D with
                                a resolution of 1/4 degree.
                                < https://www.adafruit.com/products/269 >

                                Since I built the first successful board I have encourage others to
                                try SMT when possible, it's not the scary dragon people make it out
                                to be, in my case it's actually easier to do than leaded components.


                                At 09:41 AM 4/18/2014, you wrote:
                                >Hi Cecil,
                                >
                                >I see that you were very careful andtook precautions that were not
                                >mentioned in your previous
                                >email. The ziplock bag in the fridge probably saved your day, as well as the
                                >temperature soaking time.
                                >At work, we used solder paste in 500g jars, and any open jar that
                                >was not used in a shift was trashed.
                                >But that was Telecom manufacturing were reliability and quality are
                                >a few of prime requirements.
                                >I agree with you, six reflows is pushing your luck.
                                >
                                >But we need also to be positive about SMT. This technology is way
                                >easier and way better than the now
                                >very old thus mature TH technology.
                                >
                                >Hams need not to be scared by those tiny parts. With simple care,
                                >they solder easily, and make DIY a
                                >lot of fun. That's why, since I retired, I design SDR stuff, and in
                                >a not too distant future, I will introduce
                                >what I see as the next wave in term of SDR Rx/Tx and Test instruments.
                                >
                                >73 de
                                >Jean-Paul
                                >AC9GH @ EN61vr99
                                ><mailto:louijp@...>louijp@...
                                >
                                >
                                >
                                >
                                >
                                >On Apr 18, 2014, at 1:16 AM, Cecil Bayona
                                ><<mailto:cbayona@...>cbayona@...> wrote:
                                >
                                >>I have never experienced the results you mentioned, but I keep your
                                >>information in mind, I don't postpone the soldering phase often.
                                >>
                                >>I did it a couple of times because after putting some of the parts
                                >>and emergency came up and had to abort. I placed the board in a zip
                                >>locked bag in the refrigerator and continued the next day. As a norm
                                >>I very slowly ramp the preheat temperature precisely to get rid of
                                >>moisture. On those boards I did a very long and slow warm up cycle
                                >>since the boards were cold, all the joints were soldered just fine.
                                >>
                                >>Soldering paste doesn't have a very long life in commercial outfits
                                >>but using manual paste application I have solder paste that work
                                >>quite well after two years, the commercial environment requires the
                                >>paste density to be in a very strict range in order to be
                                >>automatically applied, manual procedures can accept a larger variance.
                                >>
                                >>I did one experiment where I place a partial parts count and
                                >>re-flowed the board, I then did it an additional two times and was
                                >>surprised that the components were all fine after some of them were
                                >>re-flowed three times, since then I've read some have done as many as
                                >>six times but I think you are pushing your luck doing it that many times.
                                >>
                                >>I've bought the components to make an automatic controller for my
                                >>Infrawave Oven once that is done then repeatability will improve, and
                                >>I can work on other boards while the first batch is proceeding on
                                >>auto pilot. I'm thinking of using it for commercial projects.
                                >>
                                >>At 11:35 PM 4/17/2014, you wrote:
                                >> >Cecil,
                                >> >
                                >> >You're playing with fire when you wait for reflow,
                                >> >The solder paste is VERY sensitive to moisture, and the flux
                                >> >evaporate fairly fast.
                                >> >So, you end up with crusty paste that might hold the parts a bit,
                                >> but you are
                                >> >almost certain to create cold solder joints, and tons of solder balls.
                                >> >At all the places I have worked, 6 hours was the shelf life of a
                                >> >board with solder paste and parts.
                                >> >Past that time, the PCB was washed and recycled because it was the
                                >> >most expensive part.
                                >> >The paste and the inexpensive parts were trashed. Some (very few)
                                >> >very expensive ICs were recycled.
                                >> >
                                >> >I understand the hobbyist viewpoint, but please don't suggest that
                                >> >it is an acceptable practice.
                                >> >
                                >> >I would suggest to place a few parts and reflow them, then you can
                                >> >wait, then add fresh solder paste, place parts
                                >> >and reflow those.
                                >> >Too many reflows are not good for ICs, but 3 to 4 is OK.
                                >> >So you can limit the number of reflows by adding heat screens on
                                >> >your board for the parts already soldered
                                >> >(aluminum foil makes a good screen)
                                >> >
                                >> >My $0.02
                                >> >
                                >> >Jean-Paul (AC9GH)
                                >> >
                                >> >
                                >> >On Apr 17, 2014, at 11:03 PM, Cecil Bayona
                                >> ><<<mailto:cbayona@...>mailto:cbayona@...><mailto:cbayona@c
                                >> ox.net>cbayona@...> wrote:
                                >> >
                                >> >> From personal experience I've had no problems with putting the
                                >> >>paste and parts and then soldering a few days later, what happened
                                >> >>was that some of the binding oil evaporated but the parts were held
                                >> >>in place by the dried out paste. When placed in the oven the parts
                                >> >>were soldered OK.
                                >> >>
                                >> >>It would not be OK if you put the paste but not the parts, when you
                                >> >>go to put in the parts later they would not stick to the pad.
                                >> >>
                                >> >>At 08:53 PM 4/17/2014, you wrote:
                                >> >> >
                                >> >> >
                                >> >> >I am planning the build of an Ensemble RX and I am thinking of
                                >> >> >trying the griddle-heat gun reflow method to install the SMT parts.
                                >> >> >As far as blocking out time to apply the solder paste and place
                                >> >> >individual parts, how long can one let the applied parts stand
                                >> >> >without reflow? I would like to break the placement process up over
                                >> >> >several days but I am worried that the solder paste will separate or
                                >> >> >otherwise degrade if I don't place all the parts and reflow them in
                                >> >> >the same session. Can the process be broken up over a period of days
                                >> >> >or even a couple of weeks without ruining the already placed parts?
                                >> >> >John Stockman, KC2THY
                                >> >>
                                >> >>--
                                >> >>Cecil - k5nwa
                                >> >><
                                >> >><<http://thepartsplace.k5nwa.com/>http://thepartsplace.k5nwa.com/
                                >> >http://thepartsplace.k5nwa.com/ >
                                >> >>< <http://www.softrockradio.org/>http://www.softrockradio.org/ >
                                >> >>
                                >> >>Never take life seriously. Nobody gets out alive anyway.
                                >> >
                                >>
                                >>--
                                >>Cecil - k5nwa
                                >><
                                >><http://thepartsplace.k5nwa.com/>http://thepartsplace.k5nwa.com/ >
                                >>< http://www.softrockradio.org/ >
                                >>
                                >>Never take life seriously. Nobody gets out alive anyway.
                                >

                                --
                                Cecil - k5nwa
                                < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ >

                                Never take life seriously. Nobody gets out alive anyway.
                              • William H. Fite
                                Well, either that or dedicate your first-born to the solder gods. -- I can explain it to you, but I can t comprehend it for you.
                                Message 15 of 18 , Apr 18, 2014
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                                  Well, either that or dedicate your first-born to the solder gods.

                                  --
                                  I can explain it to you, but I can't comprehend it for you.
                                • PERI COSSEBOOM
                                  First time with SMD. Built two smaller SMD kits first. I ended up using a hobby hot air gun. $20. Did 25% of the board at a time over an afternoon. Mainly to
                                  Message 16 of 18 , Apr 18, 2014
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                                    First time with SMD. Built two smaller SMD kits first. I ended up using a hobby hot air gun. $20. Did 25% of the board at a time over an afternoon. Mainly to stay organized and to reduce the risk of knocking off parts. The wet paste melts at significantly lower temp than the solder. Which is very good. Just keep the gun vertical to the board and heat just enough to melt the solder. With practice you can tell when the solder is going to melt. No need to over heat.
                                     
                                    Use very little paste. A fine tip iron is very handy for touch ups and removing bridges. Kit isn't finished yet. I got a FT-817 for Xmas and haven't been very motivated.
                                     
                                    73 de W7WBB
                                     
                                    Peri
                                  • Jean-Paul Louis
                                    Hi Peri, Congratulations on your great start with SMT. I have been involved with SMT professionally since 1973, and now that I am retired, I design with SMD
                                    Message 17 of 18 , Apr 18, 2014
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                                      Hi Peri,

                                      Congratulations on your great start with SMT.
                                      I have been involved with SMT professionally since 1973, and now that I am retired, I design with SMD only
                                      when possible. Sometimes Through parts have a way to snick-up on you.
                                      I also use an embossing gun that I got from Hobby Lobby for $14.
                                      Don’t be mislead, the melting point of solder paste is the same as the wire as they both are 63/37 tin-lead.
                                      On the other hand, the new unleaded solder melts at a higher temperature.

                                      Good luck on your project.

                                      73 de AC9GH
                                      Jean-Paul


                                      On Apr 18, 2014, at 3:42 PM, PERI COSSEBOOM <ls5102@...> wrote:


                                      First time with SMD. Built two smaller SMD kits first. I ended up using a hobby hot air gun. $20. Did 25% of the board at a time over an afternoon. Mainly to stay organized and to reduce the risk of knocking off parts. The wet paste melts at significantly lower temp than the solder. Which is very good. Just keep the gun vertical to the board and heat just enough to melt the solder. With practice you can tell when the solder is going to melt. No need to over heat.
                                       
                                      Use very little paste. A fine tip iron is very handy for touch ups and removing bridges. Kit isn't finished yet. I got a FT-817 for Xmas and haven't been very motivated.
                                       
                                      73 de W7WBB
                                       
                                      Peri


                                    • wa7son
                                      I haven t tried this yet, but, maybe if you refrigerate overnight, it may work out okay. I would maybe place the board in a Tupperware container, (providing
                                      Message 18 of 18 , Apr 18, 2014
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                                        I haven't tried this yet, but, maybe if you refrigerate overnight, it may work out okay. I would maybe place the board in a Tupperware container, (providing you received permission for your YL)..., heh heh heh.......

                                        If you are using a heat gun, I would let it warm to room temperature, just so you don't stress the parts.
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