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Re: [SeattleRobotics] Re: surface mount class?

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  • Peter Balch
    From: T ... After just a couple of boards, I decided I preferred SM to through-hole. It s a lot faster and you end up with a much neater product. You don t
    Message 1 of 21 , Mar 22, 2011
    From: T
    > People actually can do this?
    > I thought only machines could do surface mount.

    After just a couple of boards, I decided I preferred SM to through-hole.
    It's a lot faster and you end up with a much neater product. You don't have
    to bend the resistor leads and cut them to length. You don't have to keep
    turning the board over.

    Watch a couple of YouTube videos. I haven't tried a toaster-oven or skillet
    yet (it's not clear to me how essential a stencill is).

    You need good flux-paste applied with a syringe, decent solder-wick and fine
    solder - I bought a cheap "kit". With those, even 0.5mm pitch pins are
    straightforward - much faster than through hole for a big chip.

    I found I needed very good close-up glasses - so I soldered some together
    from two +3.50 glasses from a "pound" shop. Photo attached!

    Re-working can be a pain - but no worse than for through-hole. I guess I'll
    end up doing more in the future so I'm going to build some solder-tweezers
    from an old soldering iron and maybe a desoldering hot-air pencil (there are
    DIY plans on the web).

    Peter
  • Richard Greenway
    Pick up a hot air gun, the $20 ones from home depot work, just have to watch that you don t run em too long on your board. You can easily lift off and reuse
    Message 2 of 21 , Mar 22, 2011
      Pick up a hot air gun, the $20 ones from home depot work, just have to watch that you don't run em too long on your board.  You can easily lift off and reuse even 100pin tqfp parts.  That's not something I even bother with trying to do with 40pin DIP parts.  If I need to remove a large dip, I cut the leads and call the part garbage.  With SMT, rework is much faster and easier. 

      A stencil is really only needed for BGA packages, or other packages with hidden pads.  It does make rework easier if doing 20+ of the same board.  But for single boards certainly never need it.    I have made simple stencils for QFN parts with scotch tape which works quite well.

      http://www.fenchurch.org/priv_cgi-bin/ids/index.cgi?mode=album&album=%2FComputing%2F%23001_RobotStuff%2FRobotBits%2FJan2008_CircuitBoards%2FSoldering&sort=name

      http://tinyurl.com/4h4w6jq

      Really though, the only things you actually need for reliable fine pitch SMT soldering is some flux and maybe solderwick.  solder paste can make things faster for large chips, though I find mini-wave (using a big tip on an iron and a ball of solder, rolling it along the pins) works just as well as paste.  Skillet is nice if you do have paste, you can paste up all the pads, place the parts and cook em all at once.  I usually am building up prototypes though, so do small pieces of the board, like power supplies first and then test them before populating the rest.   Or I am doing boards that are too big to fit in a skillet. 

      Richard
      www.fenchurch.org


      On 3/22/2011 1:23 PM, Peter Balch wrote:
      <*>[Attachment(s) from Peter Balch included below]
      
      From: T
      
      People actually can do this?
      I thought only machines could do surface mount.
      
      After just a couple of boards, I decided I preferred SM to through-hole. 
      It's a lot faster and you end up with a much neater product. You don't have 
      to bend the resistor leads and cut them to length. You don't have to keep 
      turning the board over.
      
      Watch a couple of YouTube videos. I haven't tried a toaster-oven or skillet 
      yet (it's not clear to me how essential a stencill is).
      
      You need good flux-paste applied with a syringe, decent solder-wick and fine 
      solder - I bought a cheap "kit". With those, even 0.5mm pitch pins are 
      straightforward - much faster than through hole for a big chip.
      
      I found I needed very good close-up glasses - so I soldered some together 
      from two +3.50 glasses from a "pound" shop. Photo attached!
      
      Re-working can be a pain - but no worse than for through-hole. I guess I'll 
      end up doing more in the future so I'm going to build some solder-tweezers 
      from an old soldering iron and maybe a desoldering hot-air pencil (there are 
      DIY plans on the web).
      
      Peter
      
      
      
      <*>Attachment(s) from Peter Balch:
      
      <*> 1 of 1 Photo(s) http://groups.yahoo.com/group/SeattleRobotics/attachments/folder/257356163/item/list 
        <*> P1000481.JPG
      
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    • Peter Balch
      From: Richard Greenway ... I wasn t thinking so much about re-using the part but about changing component values or even changing the circuit. Pretty well all
      Message 3 of 21 , Mar 23, 2011
        From: Richard Greenway
        > Pick up a hot air gun, the $20 ones from home depot work,
        > just have to watch that you don't run em too long on your board.
        > You can easily lift off and reuse even 100pin tqfp parts.

        I wasn't thinking so much about re-using the part but about changing
        component values or even changing the circuit. Pretty well all the pcbs I
        solder are prototypes. Often, the pcb is worth more that the chips - not in
        straight replacement cost but the time lost in ordering a new batch. Being a
        prototype means I've probably got a few things wrong with the circuit. An SM
        pcb is harder to hack than a through-hole one.

        So let's say I need to remove an op-amp chip - not to salvage the chip but
        to change that small part of the circuit (or, more likely, build a
        replacement on a daughter board). How can I use a hot air gun if I'm working
        in an area a few mm square? I've probably got a few wires and connectors
        soldered onto the board.

        I'd assumed that's why I needed a hot air pencil.

        I particularly like this design
        http://www.dansworkshop.com/electricity-and-electronics/smt-hot-air-pencil.htm
        whereas these seem to have trouble reaching the right temperature
        http://www.engadget.com/2006/03/07/how-to-make-a-surface-mount-soldering-iron
        http://pskillenrules.blogspot.com/2008/06/home-brew-hot-air-pencil.html


        > A stencil is really only needed for BGA packages, or other packages with
        > hidden pads.
        > http://tinyurl.com/4h4w6jq

        So you reckon that you can use a toaster-oven or skillet without a stencil?
        Ah, I see. You're just doing a single chip. You'd have trouble if there were
        several chips close to each other. Then you do the discretes by hand?

        > I usually ... do small pieces of the board, like power supplies first and
        > then
        > test them before populating the rest.

        You can re-heat the board without un-soldering the existing parts?

        Peter
      • David Buckley
        Peter I have used the Portasol Butane soldering torch with an hot air tip to unsolder 4mmsquare smt chips. Tips still available from ?Farnel in 2006. New ProII
        Message 4 of 21 , Mar 23, 2011
          Peter
          I have used the Portasol Butane soldering torch with an hot air tip to unsolder 4mmsquare smt chips.
          Tips still available from ?Farnel in 2006. New ProII from RS.
           
          DAvid
           
           
          ----- Original Message -----
          Sent: Wednesday, March 23, 2011 11:47 AM
          Subject: Re: [SeattleRobotics] Re: surface mount class?

           

          From: Richard Greenway
          > Pick up a hot air gun, the $20 ones from home depot work,
          > just have to watch that you don't run em too long on your board.
          > You can easily lift off and reuse even 100pin tqfp parts.

          I wasn't thinking so much about re-using the part but about changing
          component values or even changing the circuit. Pretty well all the pcbs I
          solder are prototypes. Often, the pcb is worth more that the chips - not in
          straight replacement cost but the time lost in ordering a new batch. Being a
          prototype means I've probably got a few things wrong with the circuit. An SM
          pcb is harder to hack than a through-hole one.

          So let's say I need to remove an op-amp chip - not to salvage the chip but
          to change that small part of the circuit (or, more likely, build a
          replacement on a daughter board). How can I use a hot air gun if I'm working
          in an area a few mm square? I've probably got a few wires and connectors
          soldered onto the board.

          I'd assumed that's why I needed a hot air pencil.

          I particularly like this design
          http://www.dansworkshop.com/electricity-and-electronics/smt-hot-air-pencil.htm
          whereas these seem to have trouble reaching the right temperature
          http://www.engadget.com/2006/03/07/how-to-make-a-surface-mount-soldering-iron
          http://pskillenrules.blogspot.com/2008/06/home-brew-hot-air-pencil.html

          > A stencil is really only needed for BGA packages, or other packages with
          > hidden pads.
          > http://tinyurl.com/4h4w6jq

          So you reckon that you can use a toaster-oven or skillet without a stencil?
          Ah, I see. You're just doing a single chip. You'd have trouble if there were
          several chips close to each other. Then you do the discretes by hand?

          > I usually ... do small pieces of the board, like power supplies first and
          > then
          > test them before populating the rest.

          You can re-heat the board without un-soldering the existing parts?

          Peter

        • Richard Greenway
          ... Some may find it so, I don t. I always prefer working and hacking on SMT boards over through hole. More of the traces are on the same side, so it s
          Message 5 of 21 , Mar 23, 2011
            > I wasn't thinking so much about re-using the part but about changing
            > component values or even changing the circuit. Pretty well all the pcbs I
            > solder are prototypes. Often, the pcb is worth more that the chips - not in
            > straight replacement cost but the time lost in ordering a new batch. Being a
            > prototype means I've probably got a few things wrong with the circuit. An SM
            > pcb is harder to hack than a through-hole one.
            >

            Some may find it so, I don't. I always prefer working and hacking on
            SMT boards over through hole. More of the traces are on the same side,
            so it's easier to see where they go. You do have to be a little more
            gentle when lifting pins, but if you want to lift a pin of an opamp, or
            even a tqfp package you can just heat it up and lift it off its pad.
            Then solder wire to the pad and the pin separately.

            Anything smaller then 1206 (and you can do 1206 and bigger too,) you can
            just remove with an iron. Just heat up both sides and slide the part
            off the pads. Or TeePee two parts into the location of one.


            > So let's say I need to remove an op-amp chip - not to salvage the chip but
            > to change that small part of the circuit (or, more likely, build a
            > replacement on a daughter board). How can I use a hot air gun if I'm working
            > in an area a few mm square? I've probably got a few wires and connectors
            > soldered onto the board.
            >
            > I'd assumed that's why I needed a hot air pencil.
            >
            > I particularly like this design
            > http://www.dansworkshop.com/electricity-and-electronics/smt-hot-air-pencil.htm
            > whereas these seem to have trouble reaching the right temperature
            > http://www.engadget.com/2006/03/07/how-to-make-a-surface-mount-soldering-iron
            > http://pskillenrules.blogspot.com/2008/06/home-brew-hot-air-pencil.html
            >

            Pencils are nice too, just cost more. You can find a good selection here.
            http://circuitspecialists.com/level.itml/icOid/7543

            But as long as you aren't "sweeping" across the board, or dropping it
            while it is hot, it's very easy to just heat up and lift the parts you
            want to remove with tweezers leaving the rest in place. Even if the
            solder melts a bit during rework.

            And just like a through hole board, you can always just cut the pins.
            (SMT pins cut pretty well with a utility knife) and clean up the pads
            with a little solder wick and heat. When repairing audio boards where I
            lost the voltage regulators for the opamps and needed to replace them
            all, knowing them to be bad, that is usually my method. It's not as
            fast as hot air probably, but at least then I know for sure the chip is
            bad if it didn't make it into the trash bin immediately and I run across
            it later.

            >> A stencil is really only needed for BGA packages, or other packages with
            >> hidden pads.
            >> http://tinyurl.com/4h4w6jq
            > So you reckon that you can use a toaster-oven or skillet without a stencil?
            > Ah, I see. You're just doing a single chip. You'd have trouble if there were
            > several chips close to each other. Then you do the discretes by hand?
            >

            You can do single chips, or the entire board. Just depends on your
            build style. If you are using paste in a syringe, it's not so difficult
            just to put a drop on all the pads, and set the parts in it. Soldering
            the entire board in one go. Or you can just choose to do the larger
            parts, or sections of a board, and then solder the rest by hand. Hand
            soldering though is not difficult. I only break out the skillet if I am
            going to be doing more then 5 of the same board. If I am just building
            a single board, I will always just hand solder it unless it has a BGA
            package on it. Even QFN/MLF (leadless) packages I will solder by hand
            with hot air to get the center pad well attached to the PCB.




            >> I usually ... do small pieces of the board, like power supplies first and
            >> then
            >> test them before populating the rest.
            > You can re-heat the board without un-soldering the existing parts?
            >
            Just let them unsolder, as long as you don't move them, they will be fine.*




            *If you are going to be doing this for devices for space travel, or
            applications that can affect human health, please make the boards right
            with the right tools. IR Reflow with the proper temperature curves, the
            right pastes and the right fluxes. I have never had a problem with
            baking parts well beyond their rated curves, removing and reusing
            complicated parts while moving from one prototype version to another.
            Pulling parts off of old PC boards to reuse in new designs etc. But
            always balance the cavalier with a thought to the final risks involved
            if something were to go wrong.




            > Peter
            >
          • Peter Balch
            From: Richard Greenway ... You mean the huge heat-sink under the chip? That s not a problem I ve had to face yet. Are you saying you use hot air on the top of
            Message 6 of 21 , Mar 23, 2011
              From: Richard Greenway
              > Even QFN/MLF (leadless) packages I will solder by hand
              > with hot air to get the center pad well attached to the PCB.

              You mean the huge heat-sink under the chip? That's not a problem I've had to
              face yet. Are you saying you use hot air on the top of the chip to melt the
              solder underneath it?

              Peter
            • Charles Holzschuh
              I have talked to two people who were interested. There may not be enough interest. However, I push on. I just noticed SchmartBoard is clearing out QFN 56 and
              Message 7 of 21 , Mar 25, 2011
                I have talked to two people who were interested. There may not be enough interest. However, I push on. I just noticed SchmartBoard is clearing out QFN 56 and 68 pin breakout boards for one dollar. The boards do not have EZ technology. Is this a problem? Do we need "EZ" technology? Should I, we, you get some?
                --- On Mon, 3/21/11, Richard Greenway <bj153@...> wrote:

                > From: Richard Greenway <bj153@...>
                > Subject: Re: [SeattleRobotics] surface mount class?
                > To: SeattleRobotics@yahoogroups.com
                > Cc: "xolzscxux" <xolzscxux@...>
                > Date: Monday, March 21, 2011, 3:00 PM
                > Or just let me know, and I can bring
                > in some microscopes, flux, pastes,
                > and tweezers to play with after a meeting.
                >
                > Richard
                > www.fenchurch.org
                >
                >
                > On 3/20/2011 3:24 PM, xolzscxux wrote:
                > > Is anyone interested in another surface mount
                > soldering class? I know I need to go over it again. I'm
                > thinking after the regular meeting on a build day. If there
                > is enough interest, we might twist Richard Fenchurch's arm
                > and he might go for it. I'm just putting this idea out there
                > - no pressure.
                > >
                > >
                > >
                > > ------------------------------------
                > >
                > > Visit the SRS Website at http://www.seattlerobotics.orgYahoo! Groups Links
                > >
                > >
                > >
                > >
                > >
                >
                >
                >
                >
                > ------------------------------------
                >
                > Visit the SRS Website at http://www.seattlerobotics.orgYahoo! Groups Links
                >
                >
                >     SeattleRobotics-fullfeatured@yahoogroups.com
                >
                >
                >
              • Richard Greenway
                Really, I don t mind running one after a meeting for any # that want to show. 1 to 30 is easy. I can bring everything except enough soldering irons, so bring
                Message 8 of 21 , Mar 25, 2011
                  Really, I don't mind running one after a meeting for any # that want to
                  show.
                  1 to 30 is easy. I can bring everything except enough soldering irons,
                  so bring your own, and learn how to use it for SMT.

                  I may not be able to make meetings as regularly in the past after May,
                  but will try to continue to make them all. Just may have kid in tow.

                  Richard

                  On 3/25/2011 2:57 PM, Charles Holzschuh wrote:
                  > I have talked to two people who were interested. There may not be enough interest. However, I push on. I just noticed SchmartBoard is clearing out QFN 56 and 68 pin breakout boards for one dollar. The boards do not have EZ technology. Is this a problem? Do we need "EZ" technology? Should I, we, you get some?
                  > --- On Mon, 3/21/11, Richard Greenway<bj153@...> wrote:
                  >
                  >> From: Richard Greenway<bj153@...>
                  >> Subject: Re: [SeattleRobotics] surface mount class?
                  >> To: SeattleRobotics@yahoogroups.com
                  >> Cc: "xolzscxux"<xolzscxux@...>
                  >> Date: Monday, March 21, 2011, 3:00 PM
                  >> Or just let me know, and I can bring
                  >> in some microscopes, flux, pastes,
                  >> and tweezers to play with after a meeting.
                  >>
                  >> Richard
                  >> www.fenchurch.org
                  >>
                  >>
                  >> On 3/20/2011 3:24 PM, xolzscxux wrote:
                  >>> Is anyone interested in another surface mount
                  >> soldering class? I know I need to go over it again. I'm
                  >> thinking after the regular meeting on a build day. If there
                  >> is enough interest, we might twist Richard Fenchurch's arm
                  >> and he might go for it. I'm just putting this idea out there
                  >> - no pressure.
                  >>>
                  >>>
                  >>> ------------------------------------
                  >>>
                  >>> Visit the SRS Website at http://www.seattlerobotics.orgYahoo! Groups Links
                  >>>
                  >>>
                  >>>
                  >>>
                  >>>
                  >>
                  >>
                  >>
                  >> ------------------------------------
                  >>
                  >> Visit the SRS Website at http://www.seattlerobotics.orgYahoo! Groups Links
                  >>
                  >>
                  >> SeattleRobotics-fullfeatured@yahoogroups.com
                  >>
                  >>
                  >>
                  >
                  > ------------------------------------
                  >
                  > Visit the SRS Website at http://www.seattlerobotics.orgYahoo! Groups Links
                  >
                  >
                  >
                  >
                  >
                • Thomas
                  Yeah, but don t you need a surgeon s hand? I mean, it s all so very TINY. If I tried, it would become all one ball of solder. Solder bridges? Heck, I d have
                  Message 9 of 21 , Mar 25, 2011
                    Yeah, but don't you need a surgeon's hand? I mean, it's all so very TINY. If I
                    tried, it would become all one ball of solder. Solder bridges? Heck, I'd have
                    solder CITIES!!!




                    Thomas Messerschmidt


                    Like robots?
                    http://www.robots-and-androids.com
                  • Mike Payson
                    _I_ can do it. If I can do it, you can too. :-) You will get solder bridges, but they are easy to fix. If you use the skillet method, it is even easier.
                    Message 10 of 21 , Mar 25, 2011
                      _I_ can do it. If I can do it, you can too. :-) You will get solder bridges, but they are easy to fix. If you use the skillet method, it is even easier.

                      On Fri, Mar 25, 2011 at 11:32 PM, Thomas <famousbots@...> wrote:
                      Yeah, but don't you need a surgeon's hand? I mean, it's all so very TINY. If I
                      tried, it would become all one ball of solder. Solder bridges? Heck, I'd have
                      solder CITIES!!!




                      Thomas Messerschmidt


                      Like robots?
                      http://www.robots-and-androids.com





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                    • Wim Lewis
                      ... Use as little solder as possible and plenty of flux, and (amazingly!) it pretty much works. When you inevitably do make a bridge, you can easily sop up the
                      Message 11 of 21 , Mar 26, 2011
                        On Mar 25, 2011, at 11:32 PM, Thomas wrote:
                        > Yeah, but don't you need a surgeon's hand? I mean, it's all so very
                        > TINY. If I
                        > tried, it would become all one ball of solder. Solder bridges?
                        > Heck, I'd have
                        > solder CITIES!!!

                        Use as little solder as possible and plenty of flux, and (amazingly!)
                        it pretty much works. When you inevitably do make a bridge, you can
                        easily sop up the extra solder with solder braid, and get rid of the
                        bridge while leaving the actual connection intact. Lots of people say
                        the best way to solder TQFPs is by bridging all the pins on one side
                        and then removing the extra.

                        If you get your boards professionally made, so they have soldermask,
                        that REALLY helps. But even my homemade ferric-chloride-and-toner-
                        transfer boards take SOICs and 0804s fine. I don't think I'd want to
                        try a QFN or SOT-363 or something on them though.

                        The other thing that really really helps is magnification. I have a
                        jeweler's-style loupe. Magnifier lamps and stereo microscopes are
                        also good.

                        I share Peter Balch's worry bout rework, though. Tweaking a prototype
                        without lifting traces or scorching a nearby component seems harder
                        than with through-hole.
                      • David Buckley
                        Using a hot air pencil it is a LOT easier to remove a small sm chip than a through hole one. Flames are too hot and burn stuff. ... From: Wim Lewis To:
                        Message 12 of 21 , Mar 26, 2011
                          Using a hot air pencil it is a LOT easier to remove a small sm chip than a through hole one.
                          Flames are too hot and burn stuff.
                           
                          ----- Original Message -----
                          From: Wim Lewis
                          Sent: Saturday, March 26, 2011 7:43 PM
                          Subject: Re: [SeattleRobotics] Re: surface mount class?

                           


                          On Mar 25, 2011, at 11:32 PM, Thomas wrote:
                          > Yeah, but don't you need a surgeon's hand? I mean, it's all so very
                          > TINY. If I
                          > tried, it would become all one ball of solder. Solder bridges?
                          > Heck, I'd have
                          > solder CITIES!!!

                          Use as little solder as possible and plenty of flux, and (amazingly!)
                          it pretty much works. When you inevitably do make a bridge, you can
                          easily sop up the extra solder with solder braid, and get rid of the
                          bridge while leaving the actual connection intact. Lots of people say
                          the best way to solder TQFPs is by bridging all the pins on one side
                          and then removing the extra.

                          If you get your boards professionally made, so they have soldermask,
                          that REALLY helps. But even my homemade ferric-chloride-and-toner-
                          transfer boards take SOICs and 0804s fine. I don't think I'd want to
                          try a QFN or SOT-363 or something on them though.

                          The other thing that really really helps is magnification. I have a
                          jeweler's-style loupe. Magnifier lamps and stereo microscopes are
                          also good.

                          I share Peter Balch's worry bout rework, though. Tweaking a prototype
                          without lifting traces or scorching a nearby component seems harder
                          than with through-hole.

                        • Peter Balch
                          From: David Buckley ... What make/model do you use? Peter
                          Message 13 of 21 , Mar 26, 2011
                            From: David Buckley
                            > Using a hot air pencil it is a LOT easier to remove a small sm chip than a
                            > through hole one.
                            > Flames are too hot and burn stuff.

                            What make/model do you use?

                            Peter
                          • David Buckley
                            Peter The PortasolPro butane pencil which I have had for 20 years (I don t use it except in emergencies and I haven t been doing that sort of thing for a long
                            Message 14 of 21 , Mar 26, 2011
                              Peter
                              The PortasolPro butane pencil which I have had for 20 years (I don't use it except in emergencies and I haven't been doing that sort of thing for a long time.). I was really surprised that HotAir tips were still available for it in 2008 when I had to debug and repair some smt motor control boards with PIC, CAN and A/D. There wasn't much room round the chips and it was just possible with a superfine tip (on a normal iron) and paste to solder new chips in. The boards had stuff and connectors on both sides so it had to be an iron to put on the new chips.
                              I would get a more modern butane torch and look for cheap tips as well, the platinum doesn't last long.
                              DAvid
                               
                               
                              ----- Original Message -----
                              Sent: Saturday, March 26, 2011 10:09 PM
                              Subject: Re: [SeattleRobotics] Re: surface mount class?

                               

                              From: David Buckley
                              > Using a hot air pencil it is a LOT easier to remove a small sm chip than a
                              > through hole one.
                              > Flames are too hot and burn stuff.

                              What make/model do you use?

                              Peter

                            • Peter Balch
                              Just came across these excellent videos http://wn.com/surface-mount I found the section on desoldering towards the end of the first one to be very interesting.
                              Message 15 of 21 , Mar 27, 2011
                                Just came across these excellent videos
                                 
                                 
                                I found the section on desoldering towards the end of the first one to be very interesting. I hadn't seen all those designs of hot-air nozzles before.
                                 
                                They're all worth watching though some of them are pretty darned advenced!
                                 
                                Peter
                                 
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