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- Newsgroups: sci.electronics
- Path: sparky!uunet!munnari.oz.au!metro!sunb!macadam!johnh
- From: johnh@macadammq.edu.au (John Haddy)
- Subject: Re: PC masks from a laser printer??
- Message-ID: <1992Jul28.223202.12212@mailhost.ocs.mq.edu.au>
- Sender: johnh@macadam (John Haddy)
- Nntp-Posting-Host: macadam.mpce.mq.edu.au
- Organization: Macquarie University, School of Mathematics, Physics, Computing and Electronics
- References: <1992Jul27.065039.5734@lugb.latrobe.edu.au> <1992Jul27.225040.606@cmkrnl.com>
- Date: Tue, 28 Jul 1992 22:32:02 GMT
- Lines: 41
-
- In article <1992Jul27.225040.606@cmkrnl.com>, jeh@cmkrnl.com writes:
- |>
- |> YOU SHOULD NOT ASSUME THAT A LASER PRINTER IS A PRECISION DEVICE!
- |>
- |> Specifically, you should not assume that your laser printer will lay down toner
- |> in the same place every time, not until you test it.
- |>
- |> Here's one test. Coax your printer to printing a 6" square grid of 0.1-inch
- |> squares. Print two such grids onto separate sheets of white paper. Find a
- |> light table or something similar, lay the two grids on top of one another, and
- |> see if you can make them match up *everywhere at once*. Never mind getting
- |> them to match up with the edges of the pages aligned -- that's not an issue,
- |> that's what the crop marks on your PCB pattern are for. No, I'm talking about
- |> getting them to match up *at all*.
-
- Before lining them up, let them settle for a while. The thermal setting process
- which bonds the toner to the paper also has the effect of making the paper/mylar
- warp. I've found that letting the mylar settle for a couple of hours in a stable
- temperature environment helps immensely.
-
- In fact, every laser printer around here that I've tried (HP's and Apple's) can
- produce good artwork - at least for boards up to about 8"x6". Good artwork in
- this case means that 0.1" hole spacings for DIPs are still close enough to 0.1"
- that a 48pin DIP will fit easily. We don't usually go beyond one trace between
- DIP pads.
-
- For information, I prefer min. 0.012" track widths. We make our own boards (double
- sided, non plated thru holes) and the etch bath varies in its characteristics, so
- we like tracks to be wide enough to cope with a little corner undercutting if it
- happens.
-
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- | _ |_ _ |_| _ _| _| Electronics Department
- |_| (_) | | | | | | (_| (_| (_| \/ School of MPCE
- ---------------------------------/- Macquarie University
- Sydney, AUSTRALIA 2109
-
- Email: johnh@mpce.mq.edu.au, Ph: +61 2 805 8959, Fax: +61 2 805 8983
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