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Re: photo layer coming off

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  • cunningfellow
    ... Well in that case def. do not use lye. Maplins might recomend it on the web page, but the manufacturer recomends sodium silicate on the package of the pre
    Message 1 of 24 , May 13, 2013
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      > dave wrote:
      > <SNIP>
      > The boards are positive photo from Maplins
      > <SNIP>

      Well in that case def. do not use lye.

      Maplins might recomend it on the web page, but
      the manufacturer recomends sodium silicate on
      the package of the pre sensitized boards.

      Sodium silicate is a lot more fogriving.
      With lye if you have the temp. too high the
      entire thing will just strip instantly.

      If you under exposed positive resist then
      EVERY thing should have stayed on.

      As everyone has said 15s is probably too short.
      Too short an exposure with positive and you
      will get a completly covered board.
    • Paul
      Hi Dave Maplin board! I nearly mentioned that when I replied before. I have had terrible problems with some batches from the local branch. I think some of it
      Message 2 of 24 , May 13, 2013
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        Hi Dave

        Maplin board! I nearly mentioned that when I replied before. I have had
        terrible problems with some batches from the local branch. I think some
        of it may sit on the shelf for a long time. I only go and buy it as a
        last resort if I really have nothing left in stock and need some board
        in a hurry.

        I have found that Maplin board needs even longer exposure times. One
        batch needed 8 minutes here.

        The Mega Electronics pre-sensitised board has always been consistent &
        reliable.
        http://www.megauk.com/pcb_laminates.php

        Never bothered printing double. LaserStar (from Mega) works really well.
        http://www.megauk.com/artwork_films.php

        But since work scrapped all their overhead projectors some time ago I
        have quite a bit of OHP transparency film which I use for less critical
        boards.

        Regards

        Paul

        On 13/05/2013 19:36, dave_donlan wrote:
        >
        > cheers for the advice I will try another test strip but go over longer
        > time.
        > The uv box is a converted scanner with four UV 9W tubes from a nail
        > curing unit
        > The boards are positive photo from Maplins
        > it is clear acetate lazer printer. I print 2 images to double up the
        > thickness
        > Dave
        >
        > --- In Homebrew_PCBs@yahoogroups.com
        > <mailto:Homebrew_PCBs%40yahoogroups.com>, "smilingcat90254"
        > <smilingcat@...> wrote:
        > >
        > > One thing not mentioned so far is to cure the image after
        > exposure-development.
        > >
        > > After the image is developed on the board, some recommend to cure
        > the remaining resist by exposing the image to harden the image. Some
        > resist may not be compatible with this step so check first.
        > >
        > > Another issue is resist adhesion. Lots of discussion on this too. I
        > always wear rubber glove to keep the board free of oil from my hand
        > and to keep chemicals off my hand. Some even have recommended to
        > mildly pre-etch the blank then apply the resist. And so on...
        > >
        > > If you want to be accurate with exposure, you might want to use
        > Stouffer's 21 step exposure guide. do a google search if you want one.
        > >
        >
        >
        >
        > No virus found in this message.
        > Checked by AVG - www.avg.com <http://www.avg.com>
        > Version: 2013.0.2904 / Virus Database: 3162/6319 - Release Date: 05/12/13
        >



        [Non-text portions of this message have been removed]
      • Harvey White
        ... As a complete guess on the exposure, look for a good exposure to be 3 to 4 minutes. This is based on my own experiences, different photoresist, more UV
        Message 3 of 24 , May 13, 2013
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          On Mon, 13 May 2013 18:36:03 -0000, you wrote:

          >cheers for the advice I will try another test strip but go over longer time.
          >The uv box is a converted scanner with four UV 9W tubes from a nail curing unit
          >The boards are positive photo from Maplins
          >it is clear acetate lazer printer. I print 2 images to double up the thickness

          As a complete guess on the exposure, look for a good exposure to be 3
          to 4 minutes. This is based on my own experiences, different
          photoresist, more UV light (perhaps).

          I do think that 15 seconds is way too small.

          Positive photoresist is a polymer (long chain molecules). It is
          damaged (read unlinked, read broken apart) by UV light. This happens
          from the top down to the board surface. The mask prevents that from
          happening.

          Under UV light, the top down starts to change into a form that can be
          dissolved. Note that the stripper is just a more concentrated
          solution, so we're dealing with degrees, not absolutes.

          Underexpose, and with too strong a developer, you tend to strip the
          board. That very thin layer of photoresist may not work to keep the
          etchant away.

          You may want to check the strength of your developer. IIRC, it took
          very little time (15 to 30 seconds) to "develop" photoresist.

          Harvey


          >Dave
          >
          >--- In Homebrew_PCBs@yahoogroups.com, "smilingcat90254" <smilingcat@...> wrote:
          >>
          >> One thing not mentioned so far is to cure the image after exposure-development.
          >>
          >> After the image is developed on the board, some recommend to cure the remaining resist by exposing the image to harden the image. Some resist may not be compatible with this step so check first.
          >>
          >> Another issue is resist adhesion. Lots of discussion on this too. I always wear rubber glove to keep the board free of oil from my hand and to keep chemicals off my hand. Some even have recommended to mildly pre-etch the blank then apply the resist. And so on...
          >>
          >> If you want to be accurate with exposure, you might want to use Stouffer's 21 step exposure guide. do a google search if you want one.
          >>
          >
        • Mitch Davis
          ... My 2c: When making boards at home I print onto drafting paper. 8mil is no problem:
          Message 4 of 24 , May 13, 2013
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            On Tue, May 14, 2013 at 2:36 AM, dave_donlan <dhd01@...> wrote:
            > cheers for the advice I will try another test strip but go over longer time.
            >
            > it is clear acetate lazer printer. I print 2 images to double up the thickness

            My 2c: When making boards at home I print onto drafting paper. 8mil
            is no problem:

            http://capnstech.blogspot.com/2011/05/playpause-making-pcbs-at-home.html

            Drafting paper is transparent to UV, and I worry less when it goes
            through the printer.

            (And now my plug: I supply pro-quality PCBs, double sided everything,
            10 boards for USD19 inc worldwide delivery.
            http://tinyurl.com/hvpcbfaq)

            Mitch.
          • Jeff Heiss
            Do you mean $19 per board when 10 boards are ordered ($190 total)? What is the cost for one or two boards? Jeff _____ From: Homebrew_PCBs@yahoogroups.com
            Message 5 of 24 , May 13, 2013
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              Do you mean $19 per board when 10 boards are ordered ($190 total)? What is
              the cost for one or two boards?



              Jeff

              _____

              From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
              On Behalf Of Mitch Davis
              Sent: Monday, May 13, 2013 10:56 PM
              To: Homebrew_PCBs@yahoogroups.com
              Subject: Re: [Homebrew_PCBs] Re: photo layer coming off





              On Tue, May 14, 2013 at 2:36 AM, dave_donlan <dhd01@...
              <mailto:dhd01%40live.co.uk> > wrote:
              > cheers for the advice I will try another test strip but go over longer
              time.
              >
              > it is clear acetate lazer printer. I print 2 images to double up the
              thickness

              My 2c: When making boards at home I print onto drafting paper. 8mil
              is no problem:

              http://capnstech.blogspot.com/2011/05/playpause-making-pcbs-at-home.html

              Drafting paper is transparent to UV, and I worry less when it goes
              through the printer.

              (And now my plug: I supply pro-quality PCBs, double sided everything,
              10 boards for USD19 inc worldwide delivery.
              http://tinyurl.com/hvpcbfaq)

              Mitch.





              [Non-text portions of this message have been removed]
            • Mitch Davis
              Hello Jeff, hello homebrewing PCB folks. First, something on-topic: When I was getting started with home etching, I also made a test strip. I used my CAD
              Message 6 of 24 , May 13, 2013
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                Hello Jeff, hello homebrewing PCB folks.

                First, something on-topic: When I was getting started with home
                etching, I also made a test strip. I used my CAD program (KiCad) to
                place 10 SOIC-14 footprints at 1-inch intervals, and wired each chip
                to its neighbours with traces of various thicknesses. After printing
                (see the blog entry from my last group email), I made marks at 1-inch
                intervals on the back of the blank board. Then I got two pieces of
                card, and slipped the blank between them with only the last inch
                hanging out. Off to my UV light, and I started a timer. Every thirty
                seconds I pulled out another inch, so that after about five minutes,
                I'd exposed all of the strip. I then developed and etched it. What I
                found was that for my UV light setup, and the blank I was using, 2½-3
                minutes was fine. I was able to get reliable 8mil traces through
                drafting paper with only one run through the printer. (I should point
                out that my making of boards at home is entirely unconnected to the
                professional PCBs I supply to customers)

                On Tue, May 14, 2013 at 11:39 AM, Jeff Heiss <jeff.heiss@...> wrote:
                >
                > Do you mean $19 per board when 10 boards are ordered ($190 total)?

                Haha, oh goodness no! I wouldn't do any business! That's USD19 total
                for 10 boards.

                As an example, this customer paid me the Australian equivalent of
                USD19 for these boards:

                http://nanibox.com/2013/03/kurobox-prototype/

                He also paid USD3 for registered shipping, but that's it. (He and I
                are both Australian so it was easier for us this way).

                According to my records, for his order, I checked and processed his
                order same day, board manufacture took 3 days, and shipping was 7
                days.

                There are some other important details: That's the up-to-5x5cm price,
                and for Paypal it's +5%. For more info, read my guide:

                http://tinyurl.com/hvpcbfaq

                > What is the cost for one or two boards?

                I have a 10-for-5 offer for boards that are up to 5x5cm (USD19), and
                10-for-5 on up to 10x10cm (USD36, but smaller sizes are cheaper.
                Also, thinner is cheaper). If you're really only after one or two, 'm
                very happy to make 5 and throw 3 or 4 away before shipping them to
                you. Or you can give them to budding engineers or use them for SMT
                soldering practice.

                Oh, and here's another happy customer:

                http://electronics.ozonejunkie.com/2012/11/pcb-manufacture/

                His boards were also USD19, but he also paid me USD25 for DHL.

                If you're greedy, you can visit these too:

                http://dangerousprototypes.com/forum/viewtopic.php?f=2&t=4722
                http://dangerousprototypes.com/2012/12/06/workshop-video-interview-with-mitch-from-hackvana/

                Talking to my customers is the highlight of my day. I have a 24-hour
                live chatroom where several dozen of my customers hang out and talk
                about electronics, give feedback to each other on their PCB designs,
                and generally have a good time. You're all welcome to join (see my
                guide).

                Like most of you I'm an engineer and a tinkerer. I love making stuff,
                and I get a buzz out of helping others to make stuff.

                Lest I wear out my welcome here, if you'd like to know more, please
                send me a private email, or come chat with me and other customers in
                the chat room.

                Regards,

                Mitch.
              • Paul
                Hi Mitch More power to you, it s a really great idea to have someone on the ground as an interface between Europe/USA and the Chinese PCB makers although I
                Message 7 of 24 , May 13, 2013
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                  Hi Mitch

                  More power to you, it's a really great idea to have someone on the
                  ground as an "interface" between Europe/USA and the Chinese PCB makers
                  although I do have a great Chinese friend in HK who is into specialist
                  electronics manufacturing and who helps me out.

                  A couple of questions

                  How about a sideline in supplying some PCB materials for us homebrew
                  hackers? Pre-sensitised board is expensive here and solder resist
                  laminate film is expensive and very difficult to find in small quantities.

                  What kind of costs for a solder paste mask? (I saw somewhere you can
                  supply them)

                  Do you miss the Fosters?

                  Ooops that's three questions.....

                  Regards

                  Paul

                  On 14/05/2013 05:44, Mitch Davis wrote:
                  >
                  > Hello Jeff, hello homebrewing PCB folks.
                  >
                  >
                  >
                  > On Tue, May 14, 2013 at 11:39 AM, Jeff Heiss <jeff.heiss@...
                  > <mailto:jeff.heiss%40comcast.net>> wrote:
                  > >
                  > > Do you mean $19 per board when 10 boards are ordered ($190 total)?
                  >
                  > Haha, oh goodness no! I wouldn't do any business! That's USD19 total
                  > for 10 boards.
                  >



                  [Non-text portions of this message have been removed]
                • Mitch Davis
                  ... That s what I do. I speak Chinese so you don t have to. I check boards thoroughly and give a report on each one. This saves you a lot of time and money.
                  Message 8 of 24 , May 13, 2013
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                    On Tue, May 14, 2013 at 2:11 PM, Paul <paul@...> wrote:
                    >
                    > More power to you, it's a really great idea to have someone on the
                    > ground as an "interface" between Europe/USA and the Chinese PCB makers
                    > although

                    That's what I do. I speak Chinese so you don't have to. I check
                    boards thoroughly and give a report on each one. This saves you a lot
                    of time and money. And I'm there to make sure the fabs do a great job
                    every time.

                    >I do have a great Chinese friend in HK who is into specialist
                    > electronics manufacturing and who helps me out.

                    I'd be interested in talking to him, as I don't have good contacts for assembly.

                    > How about a sideline in supplying some PCB materials for us homebrew
                    > hackers? Pre-sensitised board is expensive here and solder resist
                    > laminate film is expensive and very difficult to find in small quantities.

                    I'd really love to. One issue is freight. Fibreglass is extremely
                    heavy. Freight for a few boards can often end up more than for the
                    boards. For another issue, see below.

                    > What kind of costs for a solder paste mask? (I saw somewhere you can
                    > supply them)

                    I was selling laser-cut stainless frameless solderpaste stencils of up
                    to A4 in size for USD25. I have stopped doing that for the moment
                    though, as I really really have to concentrate on getting web ordering
                    of PCBs going. (And 90% of that is the back-end processing, not the
                    customer-facing stuff).

                    If you'd like to make your own solderpaste stencils, it's not hard:

                    http://lowpowerlab.com/blog/2013/02/11/diy-smd-metal-stencils-the-definitive-tutorial/

                    I think everyone should try that. (Felix is another customer of mine :-) )

                    > Do you miss the Fosters?

                    LOL, Fosters is megaswill, I never drink it. I brew my own beer :-)
                    That's what this group is for eh, making your own?

                    Mitch.
                  • Mitch Davis
                    ... I should clarify that I check the design. Here s a recent report for a customer: - No board outline file. Please see attached. The purple lines should
                    Message 9 of 24 , May 13, 2013
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                      On Tue, May 14, 2013 at 2:26 PM, Mitch Davis <mjd@...> wrote:
                      >
                      > I check boards thoroughly and give a report on each one.

                      I should clarify that I check the design. Here's a recent report for a
                      customer:

                      - No board outline file. Please see attached. The purple lines should
                      be a rectangle enclosing the whole board. You can have right angle or arc
                      corners. In particular, please pay close attention to the shape of the
                      board in the area of the four RJ45 connectors (or whatever they are).

                      - Be aware of PCB manufacture limitations if your final board outline
                      has sharp angled concave corners near the RJ45s. It's not possible to
                      faithfully reproduce sharp angled concave corners. The mill bit is 0.8mm,
                      and therefore the smallest radius of curvature of the arc you'll get on
                      concave corners is 0.4mm. Please let me know that this is ok.

                      - The fab will "pull back" copper very slightly so there's no copper
                      right at the very edge of the board. There will be a very thin copperless
                      margin right around the board. If you don't want the fab to do pullback
                      (for example, if your design had SMA connectors) then please tell me and
                      I'll tell the fab.

                      - Many packages use .dri for drill files, but Eagle wants to put drill
                      holes into .txt files. That's ok, but the files to include in your .zip
                      are the .txt files. (Also, with our .cam file, we can't find a way to stop
                      Eagle from generating useless .gpi files, sigh).

                      - On the top you have silkscreen across the pads. What will happen is
                      that the soldermask will be used to mask the silkscreen - silkcreen will be
                      omitted where it crosses pads. This is not a fatal problem, but if you're
                      expecting to get back boards where the silk looks just as you designed it,
                      this can be a bit of a shock. The easiest solution to this is to redefine
                      your footprints so no silk crosses the pads, but you'll still need to
                      carefully review every part of your board if you want a total remedy.

                      - The "XYZ" text is covering up "ABC".

                      - No silkscreen on the bottom layer (that's ok, but please tell me it's
                      intentional).

                      My chat channel is also a very good place to get a review.

                      Mitch.


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                    • Paul
                      ... But they keep telling us on the TV ads that it is amber nectar! You imply they are telling porkie pies? :-) Real ale myself... proper Brit stuff. I do brew
                      Message 10 of 24 , May 14, 2013
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                        On 14/05/2013 07:26, Mitch Davis wrote:
                        >
                        >
                        >
                        > > Do you miss the Fosters?
                        >
                        > LOL, Fosters is megaswill, I never drink it. I brew my own beer :-)
                        > That's what this group is for eh, making your own?
                        >
                        > Mitch.
                        >
                        > _
                        But they keep telling us on the TV ads that it is amber nectar! You
                        imply they are telling porkie pies? :-) Real ale myself... proper Brit
                        stuff. I do brew although none on the go at the moment.

                        Paul


                        [Non-text portions of this message have been removed]
                      • Mitch Davis
                        ... That it was an ad should be enough of a giveaway, that it was also on the TV means it s incredible. Desperate attempt to stay on topic: How long does
                        Message 11 of 24 , May 14, 2013
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                          On Tue, May 14, 2013 at 3:45 PM, Paul <paul@...> wrote:
                          >
                          > But they keep telling us on the TV ads that it is amber nectar!

                          That it was an ad should be enough of a giveaway, that it was also on
                          the TV means it's incredible.

                          Desperate attempt to stay on topic: How long does presensitised board
                          last when the bag is sealed? How about once it's been opened but then
                          sealed up? (Not talking about what the manufacturer recommends, which
                          is probably going to be "after using your 2x2cm square, throw the rest
                          of the board away" but what folks have found for themselves...)

                          Cheers,

                          Mitch.
                        • lists
                          In article , ... Thank God for that. -- Stuart Winsor Midlands RISC OS and Raspberry pi
                          Message 12 of 24 , May 14, 2013
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                            In article
                            <CA+KzSgJHRQsZ3gojr0ij=1UkLBWx-MdtbHRscDmzLUKbLxarHQ@...>,
                            Mitch Davis <mjd@...> wrote:
                            > > Do you miss the Fosters?

                            > LOL, Fosters is megaswill, I never drink it. I brew my own beer :-)

                            Thank God for that.

                            --
                            Stuart Winsor

                            Midlands RISC OS and Raspberry pi show, 13th July 2013

                            http://www.mug.riscos.org/show13/MUGshow.html
                          • lists
                            In article , ... Maplin - Arrgh Bought some board from them once, they had to order it because they had none in stock at the
                            Message 13 of 24 , May 14, 2013
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                              In article <51914A6B.9000102@...>,
                              Paul <paul@...> wrote:
                              > Maplin board!

                              Maplin - Arrgh

                              Bought some board from them once, they had to order it because they had
                              none in stock at the local shop. That was usual. I would go in with a list
                              and if I was lucky they might have two of the items I wanted - must have
                              cost them a fortune in postage because they would send direct from head
                              office post free.

                              When it turned up it seemed to be covered in scratches, which I judged
                              would have gone right through the protective film and the photo-resist. I
                              complained and they sent me a replacement piece that looked worse than the
                              first - looked like somebody had been kicking and scuffing it around on
                              the floor. I was in a hurry and desperate so I had to use it - broken
                              tracks everywhere where the scratches had removed the resist.

                              One would have thought that because I had complained they would have
                              checked the replacement over before sending it out.

                              --
                              Stuart Winsor

                              Midlands RISC OS and Raspberry pi show, 13th July 2013

                              http://www.mug.riscos.org/show13/MUGshow.html
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