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double sided PCB, accuracy

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  • Michel Baguet
    hi guys, I got to the point where I can etch 6 mils traces and 32 mils vias with a 12 mils hole with inkjet paper. To align both side, I tried inkjet
    Message 1 of 26 , Jul 3, 2008
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      hi guys,

      I got to the point where I can etch 6 mils traces and 32 mils vias with a 12 mils hole with inkjet paper. To align both side, I tried inkjet transparent but those get deformed at some places during printing and it's impossible to align the vias. A part of them are ok while other are only touching by the side.
      Taping the transparent on 200g paper didn't help.
      Do someone solve this problem ?

      Mike.





      [Non-text portions of this message have been removed]
    • DJ Delorie
      What I ve been doing is including a target in my prints (four 25 mil squares in a square, with a 1 mil gap - that translates to a 1 mil ink crosshair when I
      Message 2 of 26 , Jul 3, 2008
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        What I've been doing is including a "target" in my prints (four 25 mil
        squares in a square, with a 1 mil gap - that translates to a 1 mil ink
        crosshair when I print negatives). I print this on all photomasks and
        one on plain paper. The plain paper one I use to pre-drill 16 mil
        holes at each crosshair. Then, when exposing, I can line up the holes
        with the crosshairs pretty accurately, and double-check through the
        glass overlay.
      • Michel Baguet
        Well, line up is not a problem. it s the transparent getting deformed when heated. ... From: DJ Delorie Subject: Re: [Homebrew_PCBs] double
        Message 3 of 26 , Jul 3, 2008
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          Well, line up is not a problem. it's the transparent getting deformed when heated.

          --- On Fri, 7/4/08, DJ Delorie <dj@...> wrote:
          From: DJ Delorie <dj@...>
          Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
          To: Homebrew_PCBs@yahoogroups.com
          Date: Friday, July 4, 2008, 5:50 AM













          What I've been doing is including a "target" in my prints (four 25 mil

          squares in a square, with a 1 mil gap - that translates to a 1 mil ink

          crosshair when I print negatives). I print this on all photomasks and

          one on plain paper. The plain paper one I use to pre-drill 16 mil

          holes at each crosshair. Then, when exposing, I can line up the holes

          with the crosshairs pretty accurately, and double-check through the

          glass overlay.



























          [Non-text portions of this message have been removed]
        • fana cute
          I never try this, but I read from some article (i ve forgotten where) that problem is from your ink printer...and the article advised to use epson ink.. ...
          Message 4 of 26 , Jul 4, 2008
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            I never try this, but I read from some article (i've forgotten where) that problem is from your ink printer...and the article advised to use epson ink..

            --- On Thu, 7/3/08, Michel Baguet <bagmik@...> wrote:
            From: Michel Baguet <bagmik@...>
            Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
            To: Homebrew_PCBs@yahoogroups.com
            Date: Thursday, July 3, 2008, 11:04 PM











            Well, line up is not a problem. it's the transparent getting deformed when heated.



            --- On Fri, 7/4/08, DJ Delorie <dj@...> wrote:

            From: DJ Delorie <dj@...>

            Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy

            To: Homebrew_PCBs@ yahoogroups. com

            Date: Friday, July 4, 2008, 5:50 AM



            What I've been doing is including a "target" in my prints (four 25 mil



            squares in a square, with a 1 mil gap - that translates to a 1 mil ink



            crosshair when I print negatives). I print this on all photomasks and



            one on plain paper. The plain paper one I use to pre-drill 16 mil



            holes at each crosshair. Then, when exposing, I can line up the holes



            with the crosshairs pretty accurately, and double-check through the



            glass overlay.























            [Non-text portions of this message have been removed]





























            [Non-text portions of this message have been removed]
          • Dylan Smith
            ... First, I presume you re using glossy inkjet paper for toner transfer from a laser printer. If that s the case you don t need to muck around with
            Message 5 of 26 , Jul 4, 2008
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              On Thu, 3 Jul 2008, Michel Baguet wrote:

              > hi guys,
              >
              > I got to the point where I can etch 6 mils traces and 32 mils vias with
              > a 12 mils hole with inkjet paper.

              First, I presume you're using glossy inkjet paper for toner transfer from
              a laser printer.

              If that's the case you don't need to muck around with transparencies.
              Print both sides of the layout to your normal paper, place them together
              face in - hold them to a bright light and use the vias to align. Suitable
              bright lights are: the sun, a table lamp, or best, a light box where you
              can lay it all flat.

              Then tape the ends of the paper together at one end, to form a hinge.
              Re-check that it's still aligned. If it is, slip the copper board between
              the paper and get ironing.

              I've done lots of double sided boards this way - never had a failure.
            • Harvey White
              On Fri, 4 Jul 2008 09:47:55 +0100 (BST), you wrote: I ve always had a conceptual problem doing it exactly this way. I can see that if the joint between the
              Message 6 of 26 , Jul 4, 2008
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                On Fri, 4 Jul 2008 09:47:55 +0100 (BST), you wrote:

                I've always had a conceptual problem doing it exactly this way. I can
                see that if the joint between the two pieces of paper is exactly in
                the middle of the board thickness, every thing aligns. If it's not,
                then one layer is offset with respect to the other.

                Has anyone considered aligning the masks with a filler made from a
                scrap piece of etched board, same thickness, and then perhaps a piece
                of plastic to duplicate the board?

                Harvey


                >On Thu, 3 Jul 2008, Michel Baguet wrote:
                >
                >> hi guys,
                >>
                >> I got to the point where I can etch 6 mils traces and 32 mils vias with
                >> a 12 mils hole with inkjet paper.
                >
                >First, I presume you're using glossy inkjet paper for toner transfer from
                >a laser printer.
                >
                >If that's the case you don't need to muck around with transparencies.
                >Print both sides of the layout to your normal paper, place them together
                >face in - hold them to a bright light and use the vias to align. Suitable
                >bright lights are: the sun, a table lamp, or best, a light box where you
                >can lay it all flat.
                >
                >Then tape the ends of the paper together at one end, to form a hinge.
                >Re-check that it's still aligned. If it is, slip the copper board between
                >the paper and get ironing.
                >
                >I've done lots of double sided boards this way - never had a failure.
              • Leon
                ... From: Harvey White To: Sent: Friday, July 04, 2008 2:09 PM Subject: Re: [Homebrew_PCBs] double
                Message 7 of 26 , Jul 4, 2008
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                  ----- Original Message -----
                  From: "Harvey White" <madyn@...>
                  To: <Homebrew_PCBs@yahoogroups.com>
                  Sent: Friday, July 04, 2008 2:09 PM
                  Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy


                  > On Fri, 4 Jul 2008 09:47:55 +0100 (BST), you wrote:
                  >
                  > I've always had a conceptual problem doing it exactly this way. I can
                  > see that if the joint between the two pieces of paper is exactly in
                  > the middle of the board thickness, every thing aligns. If it's not,
                  > then one layer is offset with respect to the other.
                  >
                  > Has anyone considered aligning the masks with a filler made from a
                  > scrap piece of etched board, same thickness, and then perhaps a piece
                  > of plastic to duplicate the board?

                  That has been mentioned on this forum before, it's probably the best way to
                  do it. A couple of pegs could be used with holes in the transparencies, to
                  make the alignment even better. I think that something similar is used by
                  the PCB manufacturers - they use dowels with their phototools.

                  Leon
                  --
                  Leon Heller
                  Amateur radio call-sign G1HSM
                  Yaesu FT-817ND and FT-857D transceivers
                  Suzuki SV1000S motorcycle
                  leon355@...
                  http://www.geocities.com/leon_heller
                • Bertho Boman
                  Sticking the tail or joint between two half thickness spacers (strips) forces the tail to be in the middle and the artwork aligns. To use the alignment pins
                  Message 8 of 26 , Jul 4, 2008
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                    Sticking the "tail" or joint between two half thickness spacers (strips)
                    forces the tail to be in the middle and the artwork aligns.



                    To use the alignment pins suggested a dedicated puncher with fixed spacing
                    should be used and a way to accurately align the artworks to be punched. Of
                    course the fixture pins must also accurately match the punch setup.

                    Bertho





                    From: Harvey White Sent: Friday, July 04, 2008 09:09:

                    I've always had a conceptual problem doing it exactly this way. I can
                    see that if the joint between the two pieces of paper is exactly in
                    the middle of the board thickness, every thing aligns. If it's not,
                    then one layer is offset with respect to the other.

                    Has anyone considered aligning the masks with a filler made from a
                    scrap piece of etched board, same thickness, and then perhaps a piece
                    of plastic to duplicate the board?

                    Harvey



                    [Non-text portions of this message have been removed]
                  • Dylan Smith
                    ... I ve never found it to be a problem. I only had bad registration on one board I ve made this way, and even then it wasn t bad enough that the board
                    Message 9 of 26 , Jul 4, 2008
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                      On Fri, 4 Jul 2008, Harvey White wrote:

                      > On Fri, 4 Jul 2008 09:47:55 +0100 (BST), you wrote:
                      >
                      > I've always had a conceptual problem doing it exactly this way. I can
                      > see that if the joint between the two pieces of paper is exactly in
                      > the middle of the board thickness, every thing aligns. If it's not,
                      > then one layer is offset with respect to the other.

                      I've never found it to be a problem. I only had bad registration on one
                      board I've made this way, and even then it wasn't bad enough that the
                      board couldn't be used. Most of the time the registration is pretty much
                      spot on. If you need really fine tolerances for small vias then I suspect
                      a piece of old board in the tape 'hinge' as you suggest would reduce the
                      risk of mis-registration. I use 0.8mm drill bits, so my vias tend to be
                      sized for that (except for things like jumper headers where I use 1.0mm
                      bits), with 10 mil annular rings minimum (so that'd make my largest vias
                      35 mils, and the smaller ones 30 mils.
                    • DJ Delorie
                      ... Ah, that. What I did was calibrate the deformity once (transfer a 3x3 square to a board and measure it) and compensate for it in PCB. To align two sides,
                      Message 10 of 26 , Jul 4, 2008
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                        Michel Baguet <bagmik@...> writes:
                        > Well, line up is not a problem. it's the transparent getting
                        > deformed when heated.

                        Ah, that. What I did was calibrate the deformity once (transfer a 3x3
                        square to a board and measure it) and compensate for it in PCB. To
                        align two sides, I ended up using targets centered on the sides of the
                        board, rather than diagonally opposite. Also, I've tried using a hand
                        iron to tack down the paper before laminating it.

                        Photomask is easier because there's no heat, you can see through the
                        paper to line it up, and nothing moves during the exposure.
                      • DJ Delorie
                        ... Another thing to try is to tape *three* corners, not two. The extra tension helps hold the seam centered on the thickness of the board. Not that I ve ever
                        Message 11 of 26 , Jul 4, 2008
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                          Harvey White <madyn@...> writes:
                          > Has anyone considered aligning the masks with a filler made from a
                          > scrap piece of etched board, same thickness, and then perhaps a
                          > piece of plastic to duplicate the board?

                          Another thing to try is to tape *three* corners, not two. The extra
                          tension helps hold the seam centered on the thickness of the board.
                          Not that I've ever done that; my TT paper is too opaque to line up
                          that way. I've pre-drilled target holes in the PCB and poked matching
                          holes in the TT paper to tack it down in the right place, with some
                          success.
                        • Michel Baguet
                          Using a filler is partway what I m doing. I put a target at each corner of the two sheets, align them with needles then lift one of the sheet to insert a piece
                          Message 12 of 26 , Jul 4, 2008
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                            Using a filler is partway what I'm doing. I put a target at each corner of the two sheets, align them with needles then lift one of the sheet to insert a piece of PCB to get the right space between them. I place the filler outside the printed area but as close as possible from the needles. I tape the two sheet to the filler, remove the needles (the tape is supossed to keep the sheets aligned) and  put the PCB to etch between the sheets, tape the sheet to the PCB and remove the filler.This is many manipulations and whatever you do, alignement is like playing with dices . Some times you win, some times you loose... Especially with 32 mils vias.
                            This is the reason why I wanted to use transparent for inkjet. But there are two problems, the first is that the transparent get deformed, bended with the heat of the fusing unit inside the laser printer and the second, toner density is very light, even with density set at max. (laserjet 6P) And I'm afraid that the pcb will be etched with a lot of pinhole.
                            So I believe I'll get back to blind alignement with plain paper by first driling 12 or 16 mils holes at the corner of the pcb to etch and holes in the sheets and align them with needles in the PCB.



                            --- On Fri, 7/4/08, Harvey White <madyn@...> wrote:
                            From: Harvey White <madyn@...>
                            Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                            To: Homebrew_PCBs@yahoogroups.com
                            Date: Friday, July 4, 2008, 1:09 PM











                            On Fri, 4 Jul 2008 09:47:55 +0100 (BST), you wrote:



                            I've always had a conceptual problem doing it exactly this way. I can

                            see that if the joint between the two pieces of paper is exactly in

                            the middle of the board thickness, every thing aligns. If it's not,

                            then one layer is offset with respect to the other.



                            Has anyone considered aligning the masks with a filler made from a

                            scrap piece of etched board, same thickness, and then perhaps a piece

                            of plastic to duplicate the board?



                            Harvey



                            >On Thu, 3 Jul 2008, Michel Baguet wrote:

                            >

                            >> hi guys,

                            >>

                            >> I got to the point where I can etch 6 mils traces and 32 mils vias with

                            >> a 12 mils hole with inkjet paper.

                            >

                            >First, I presume you're using glossy inkjet paper for toner transfer from

                            >a laser printer.

                            >

                            >If that's the case you don't need to muck around with transparencies.

                            >Print both sides of the layout to your normal paper, place them together

                            >face in - hold them to a bright light and use the vias to align. Suitable

                            >bright lights are: the sun, a table lamp, or best, a light box where you

                            >can lay it all flat.

                            >

                            >Then tape the ends of the paper together at one end, to form a hinge.

                            >Re-check that it's still aligned. If it is, slip the copper board between

                            >the paper and get ironing.

                            >

                            >I've done lots of double sided boards this way - never had a failure.



























                            [Non-text portions of this message have been removed]
                          • Michel Baguet
                            the main problem is that the transparent get deformed while passing thru the fusing unit of the printer. ... From: Leon Subject: Re:
                            Message 13 of 26 , Jul 4, 2008
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                              the main problem is that the transparent get deformed while passing thru the fusing unit of the printer.

                              --- On Fri, 7/4/08, Leon <leon355@...> wrote:
                              From: Leon <leon355@...>
                              Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                              To: Homebrew_PCBs@yahoogroups.com
                              Date: Friday, July 4, 2008, 1:21 PM











                              ----- Original Message -----

                              From: "Harvey White" <madyn@embarqmail. com>

                              To: <Homebrew_PCBs@ yahoogroups. com>

                              Sent: Friday, July 04, 2008 2:09 PM

                              Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy



                              > On Fri, 4 Jul 2008 09:47:55 +0100 (BST), you wrote:

                              >

                              > I've always had a conceptual problem doing it exactly this way. I can

                              > see that if the joint between the two pieces of paper is exactly in

                              > the middle of the board thickness, every thing aligns. If it's not,

                              > then one layer is offset with respect to the other.

                              >

                              > Has anyone considered aligning the masks with a filler made from a

                              > scrap piece of etched board, same thickness, and then perhaps a piece

                              > of plastic to duplicate the board?



                              That has been mentioned on this forum before, it's probably the best way to

                              do it. A couple of pegs could be used with holes in the transparencies, to

                              make the alignment even better. I think that something similar is used by

                              the PCB manufacturers - they use dowels with their phototools.



                              Leon

                              --

                              Leon Heller

                              Amateur radio call-sign G1HSM

                              Yaesu FT-817ND and FT-857D transceivers

                              Suzuki SV1000S motorcycle

                              leon355@btinternet. com

                              http://www.geocitie s.com/leon_ heller





























                              [Non-text portions of this message have been removed]
                            • Michel Baguet
                              Do you use plain paper ? ... From: Dylan Smith Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy To: Homebrew_PCBs@yahoogroups.com
                              Message 14 of 26 , Jul 4, 2008
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                                Do you use plain paper ?

                                --- On Fri, 7/4/08, Dylan Smith <dyls@...> wrote:
                                From: Dylan Smith <dyls@...>
                                Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                                To: Homebrew_PCBs@yahoogroups.com
                                Date: Friday, July 4, 2008, 3:38 PM











                                On Fri, 4 Jul 2008, Harvey White wrote:



                                > On Fri, 4 Jul 2008 09:47:55 +0100 (BST), you wrote:

                                >

                                > I've always had a conceptual problem doing it exactly this way. I can

                                > see that if the joint between the two pieces of paper is exactly in

                                > the middle of the board thickness, every thing aligns. If it's not,

                                > then one layer is offset with respect to the other.



                                I've never found it to be a problem. I only had bad registration on one

                                board I've made this way, and even then it wasn't bad enough that the

                                board couldn't be used. Most of the time the registration is pretty much

                                spot on. If you need really fine tolerances for small vias then I suspect

                                a piece of old board in the tape 'hinge' as you suggest would reduce the

                                risk of mis-registration. I use 0.8mm drill bits, so my vias tend to be

                                sized for that (except for things like jumper headers where I use 1.0mm

                                bits), with 10 mil annular rings minimum (so that'd make my largest vias

                                35 mils, and the smaller ones 30 mils.



























                                [Non-text portions of this message have been removed]
                              • Michel Baguet
                                The transparent is already deformed when passing thru the fusing unit of the printer and the the deformation are not regular. For exemple, the corners align
                                Message 15 of 26 , Jul 4, 2008
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                                  The transparent is already deformed when passing thru the fusing unit of the printer and the
                                  the deformation are not regular. For exemple, the corners align well while the top center is too low, the center is on the left and the center bottom is on the right... and so on.
                                  Different print give different deformation positions.

                                  --- On Fri, 7/4/08, DJ Delorie <dj@...> wrote:
                                  From: DJ Delorie <dj@...>
                                  Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                                  To: Homebrew_PCBs@yahoogroups.com
                                  Date: Friday, July 4, 2008, 4:07 PM













                                  Michel Baguet <bagmik@yahoo. com> writes:

                                  > Well, line up is not a problem. it's the transparent getting

                                  > deformed when heated.



                                  Ah, that. What I did was calibrate the deformity once (transfer a 3x3

                                  square to a board and measure it) and compensate for it in PCB. To

                                  align two sides, I ended up using targets centered on the sides of the

                                  board, rather than diagonally opposite. Also, I've tried using a hand

                                  iron to tack down the paper before laminating it.



                                  Photomask is easier because there's no heat, you can see through the

                                  paper to line it up, and nothing moves during the exposure.



























                                  [Non-text portions of this message have been removed]
                                • Michel Baguet
                                  What do you mean by some succes ? Is-it often, 3 out of 5, or less ? Is there a big off-registration ? ... From: DJ Delorie Subject: Re:
                                  Message 16 of 26 , Jul 4, 2008
                                  • 0 Attachment
                                    What do you mean by "some succes" ? Is-it often, 3 out of 5, or less ?
                                    Is there a big off-registration ?

                                    --- On Fri, 7/4/08, DJ Delorie <dj@...> wrote:
                                    From: DJ Delorie <dj@...>
                                    Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                                    To: Homebrew_PCBs@yahoogroups.com
                                    Date: Friday, July 4, 2008, 4:09 PM













                                    Harvey White <madyn@embarqmail. com> writes:

                                    > Has anyone considered aligning the masks with a filler made from a

                                    > scrap piece of etched board, same thickness, and then perhaps a

                                    > piece of plastic to duplicate the board?



                                    Another thing to try is to tape *three* corners, not two. The extra

                                    tension helps hold the seam centered on the thickness of the board.

                                    Not that I've ever done that; my TT paper is too opaque to line up

                                    that way. I've pre-drilled target holes in the PCB and poked matching

                                    holes in the TT paper to tack it down in the right place, with some

                                    success.



























                                    [Non-text portions of this message have been removed]
                                  • Leon
                                    ... From: Michel Baguet To: Sent: Friday, July 04, 2008 5:40 PM Subject: Re: [Homebrew_PCBs] double sided
                                    Message 17 of 26 , Jul 4, 2008
                                    • 0 Attachment
                                      ----- Original Message -----
                                      From: "Michel Baguet" <bagmik@...>
                                      To: <Homebrew_PCBs@yahoogroups.com>
                                      Sent: Friday, July 04, 2008 5:40 PM
                                      Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy


                                      > the main problem is that the transparent get deformed while passing thru
                                      > the fusing unit of the printer.

                                      I think it only works properly when printing transparencies on an inkjet
                                      printer.

                                      Leon
                                      --
                                      Leon Heller
                                      Amateur radio call-sign G1HSM
                                      Yaesu FT-817ND and FT-857D transceivers
                                      Suzuki SV1000S motorcycle
                                      leon355@...
                                      http://www.geocities.com/leon_heller
                                    • DJ Delorie
                                      Try using laser transparencies instead of inkjet transparencies (assuming the toner will release afterwards). The pin trick is easier if you pre-poke the holes
                                      Message 18 of 26 , Jul 4, 2008
                                      • 0 Attachment
                                        Try using laser transparencies instead of inkjet transparencies
                                        (assuming the toner will release afterwards).

                                        The pin trick is easier if you pre-poke the holes from the toner side,
                                        so you can tell where they are.
                                      • DJ Delorie
                                        ... Keep in mind I use 6/6 rules with 13 mil via drills, so some success for me might be just fine for you. Success for me is within 4-5 mils of dead
                                        Message 19 of 26 , Jul 4, 2008
                                        • 0 Attachment
                                          Michel Baguet <bagmik@...> writes:
                                          > What do you mean by "some succes" ? Is-it often, 3 out of 5, or
                                          > less? Is there a big off-registration ?

                                          Keep in mind I use 6/6 rules with 13 mil via drills, so "some success"
                                          for me might be "just fine" for you. Success for me is within 4-5
                                          mils of dead center; I use my 13 mil drills as the pins. It's a lot
                                          of hassle, but if you take your time it does come out correct.
                                        • Michel Baguet
                                          indeed for uv exposure but I m doing toner tranfer ... From: Leon Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy To:
                                          Message 20 of 26 , Jul 4, 2008
                                          • 0 Attachment
                                            indeed for uv exposure but I'm doing toner tranfer

                                            --- On Fri, 7/4/08, Leon <leon355@...> wrote:
                                            From: Leon <leon355@...>
                                            Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                                            To: Homebrew_PCBs@yahoogroups.com
                                            Date: Friday, July 4, 2008, 5:13 PM











                                            ----- Original Message -----

                                            From: "Michel Baguet" <bagmik@yahoo. com>

                                            To: <Homebrew_PCBs@ yahoogroups. com>

                                            Sent: Friday, July 04, 2008 5:40 PM

                                            Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy



                                            > the main problem is that the transparent get deformed while passing thru

                                            > the fusing unit of the printer.



                                            I think it only works properly when printing transparencies on an inkjet

                                            printer.



                                            Leon

                                            --

                                            Leon Heller

                                            Amateur radio call-sign G1HSM

                                            Yaesu FT-817ND and FT-857D transceivers

                                            Suzuki SV1000S motorcycle

                                            leon355@btinternet. com

                                            http://www.geocitie s.com/leon_ heller





























                                            [Non-text portions of this message have been removed]
                                          • Michel Baguet
                                            A few days ago, I read on HP website that they are using a special mean to fuse the toner with the transparent so no possible release . ... From: DJ Delorie
                                            Message 21 of 26 , Jul 4, 2008
                                            • 0 Attachment
                                              A few days ago, I read on HP website that they are using a special mean to fuse the toner with the transparent so no possible release .

                                              --- On Fri, 7/4/08, DJ Delorie <dj@...> wrote:
                                              From: DJ Delorie <dj@...>
                                              Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                                              To: Homebrew_PCBs@yahoogroups.com
                                              Date: Friday, July 4, 2008, 5:49 PM













                                              Try using laser transparencies instead of inkjet transparencies

                                              (assuming the toner will release afterwards).



                                              The pin trick is easier if you pre-poke the holes from the toner side,

                                              so you can tell where they are.



























                                              [Non-text portions of this message have been removed]
                                            • Michel Baguet
                                              Good idea, using the drill bits as a guide to align the sheet, same diameter as the holes should avoid misalignment ... From: DJ Delorie
                                              Message 22 of 26 , Jul 4, 2008
                                              • 0 Attachment
                                                Good idea, using the drill bits as a guide to align the sheet, same diameter as the holes should avoid misalignment

                                                --- On Fri, 7/4/08, DJ Delorie <dj@...> wrote:
                                                From: DJ Delorie <dj@...>
                                                Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                                                To: Homebrew_PCBs@yahoogroups.com
                                                Date: Friday, July 4, 2008, 5:51 PM













                                                Michel Baguet <bagmik@yahoo. com> writes:

                                                > What do you mean by "some succes" ? Is-it often, 3 out of 5, or

                                                > less? Is there a big off-registration ?



                                                Keep in mind I use 6/6 rules with 13 mil via drills, so "some success"

                                                for me might be "just fine" for you. Success for me is within 4-5

                                                mils of dead center; I use my 13 mil drills as the pins. It's a lot

                                                of hassle, but if you take your time it does come out correct.



























                                                [Non-text portions of this message have been removed]
                                              • Bertho Boman
                                                Why blind alignment? Crank up enough backlight and you should be able to see through the paper. Bertho From Michel Baguet Sent: Friday, July 04, 2008
                                                Message 23 of 26 , Jul 4, 2008
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                                                  Why blind alignment? Crank up enough backlight and you should be able to
                                                  see through the paper.
                                                  Bertho

                                                  From Michel Baguet Sent: Friday, July 04, 2008 12:39

                                                  ----> snip
                                                  So I believe I'll get back to blind alignment with plain paper by first
                                                  drilling 12 or 16 mils holes at the corner of the pcb to etch and holes in
                                                  the sheets and align them with needles in the PCB.
                                                • Philip Pemberton
                                                  ... Perhaps a strobe light would be powerful enough. Assuming you could get used to the flickering :) But seriously, what about this -- 1 piece of FR4, 1.6mm
                                                  Message 24 of 26 , Jul 6, 2008
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                                                    Bertho Boman wrote:
                                                    > Why blind alignment? Crank up enough backlight and you should be able to
                                                    > see through the paper.

                                                    Perhaps a strobe light would be powerful enough. Assuming you could get used
                                                    to the flickering :)

                                                    But seriously, what about this --

                                                    1 piece of FR4, 1.6mm (assuming that's what you're using to make the PCBs).
                                                    Remove the copper, either by etching or sanding. Cut it into four 2"x0.5" strips.

                                                    Drill a tiny - as in roughly the size of the needle - hole in each corner,
                                                    about a quarter inch in from the top and left edges. Do the same thing for all
                                                    four strips.

                                                    Push four thin needles into the holes. Ideally these should push in and fit
                                                    tightly. Also put some double-sided tape on the FR4. Both sides :)

                                                    Now print your pattern with alignment holes ~2x0.5" away from the corners.
                                                    Take one sheet of paper and push it onto the needles. Check alignment and
                                                    remove the tape from each piece of FR4 in turn. Stick them down. Now put your
                                                    PCB in the middle and do the same for the other side, align as before, stick
                                                    down and remove the needles.

                                                    Iron the board and cross your fingers...

                                                    I'm still working on finding a decent TT paper that's still in production.
                                                    Seems HP Everyday doesn't work any more... Still, it works in the inkjet (a
                                                    rebuilt Epson C86 loaded with dye based ink) so it's not a total waste...

                                                    --
                                                    Phil.
                                                    ygroups@...
                                                    http://www.philpem.me.uk/
                                                  • Michel Baguet
                                                    I just find a way to solve the print geometry problem. Now I m going to test blind alignment with needles and holes in the PCB of the same diameter. ... From:
                                                    Message 25 of 26 , Jul 6, 2008
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                                                      I just find a way to solve the print geometry problem. Now I'm going to test blind alignment with needles and holes in the PCB of the same diameter.

                                                      --- On Sun, 7/6/08, Philip Pemberton <ygroups@...> wrote:
                                                      From: Philip Pemberton <ygroups@...>
                                                      Subject: Re: [Homebrew_PCBs] double sided PCB, accuracy
                                                      To: Homebrew_PCBs@yahoogroups.com
                                                      Date: Sunday, July 6, 2008, 7:45 AM











                                                      Bertho Boman wrote:

                                                      > Why blind alignment? Crank up enough backlight and you should be able to

                                                      > see through the paper.



                                                      Perhaps a strobe light would be powerful enough. Assuming you could get used

                                                      to the flickering :)



                                                      But seriously, what about this --



                                                      1 piece of FR4, 1.6mm (assuming that's what you're using to make the PCBs).

                                                      Remove the copper, either by etching or sanding. Cut it into four 2"x0.5" strips.



                                                      Drill a tiny - as in roughly the size of the needle - hole in each corner,

                                                      about a quarter inch in from the top and left edges. Do the same thing for all

                                                      four strips.



                                                      Push four thin needles into the holes. Ideally these should push in and fit

                                                      tightly. Also put some double-sided tape on the FR4. Both sides :)



                                                      Now print your pattern with alignment holes ~2x0.5" away from the corners.

                                                      Take one sheet of paper and push it onto the needles. Check alignment and

                                                      remove the tape from each piece of FR4 in turn. Stick them down. Now put your

                                                      PCB in the middle and do the same for the other side, align as before, stick

                                                      down and remove the needles.



                                                      Iron the board and cross your fingers...



                                                      I'm still working on finding a decent TT paper that's still in production.

                                                      Seems HP Everyday doesn't work any more... Still, it works in the inkjet (a

                                                      rebuilt Epson C86 loaded with dye based ink) so it's not a total waste...



                                                      --

                                                      Phil.

                                                      ygroups@philpem. me.uk

                                                      http://www.philpem me.uk/



























                                                      [Non-text portions of this message have been removed]
                                                    • Bertho Boman
                                                      Try a regular good flash light or a halogen desk lamp. It works surprisingly well. A related trick if this method is used is to not use two identical targets
                                                      Message 26 of 26 , Jul 6, 2008
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                                                        Try a regular good flash light or a halogen desk lamp. It works
                                                        surprisingly well.

                                                        A related trick if this method is used is to not use two identical targets
                                                        as is normally done. Instead use complimentary targets. For example, on
                                                        one layer use concentric circles of 5 mil lines and 5 mil spacing. On the
                                                        other layer use the same dimensions but start with a space and then a black
                                                        line. In other words, you will have a positive and a negative target.
                                                        When placed on top of each other and viewed with light from below they
                                                        will turn all black only when perfectly aligned. Any error is very obvious.

                                                        Another comment:
                                                        Taping just a hinge allows a slight movement of the layers since the hinge
                                                        allows a microscopic movement. Cut off the corners of the top layer where
                                                        the hinge will normally be placed. Placing tape on those corners really
                                                        locks the artwork together without any movement.

                                                        Finally, place two half thickness spacers one on each side of the tail to
                                                        force it to be in the center when the board is put under the glass for
                                                        exposure. For ironing use just one half sized spacer on the bottom and push
                                                        the tail down on it to keep the top and bottom aligned.
                                                        Bertho
                                                        =================================


                                                        From: Philip Pemberton Sent: Sunday, July 06, 2008 03:45

                                                        Bertho Boman wrote:
                                                        > Why blind alignment? Crank up enough backlight and you should be able to
                                                        > see through the paper.

                                                        Perhaps a strobe light would be powerful enough. Assuming you could get used

                                                        to the flickering :)
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