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SSOP pcb printing

Discussion in 'Electronic Design' started by EBG, Jan 7, 2004.

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  1. EBG

    EBG Guest

    I'm attempting my first project using an SSOP chip.

    I've always been able to do decent pc boards by simply printing at 100% and
    using my Epson 880 inkjet but it looks as though I may be SOL with these
    small devices.

    Is the inkjet out of the question?....do I need to go back to my Laser
    printer? (looks that way).....any tricks?

    Thanks
     
  2. Leon Heller

    Leon Heller Guest

    I don't have any problems using an old LaserJet IIIp for artwork. I can
    manage down to about 10 mil tracks and 0.65 mm spaced leads without too
    many problems.

    Leon
     
  3. Modern inkjet printers are very good and I haven't seen a consumer laser printer that is even in the same league, performance wise. The small number of laser printers I've seen have printed tracks significantly fatter than they were supposed to. The last board I did came out perfectly and was printed on an Epson Stylus C82 inkjet printer (rated for 5760x1440 dpi, which is twice the vertical and horizontal resolution of yours). Features as small as 2.496 mils were intact, although admittedly, under 8X optical magnification slight edge distortion was apparent, so I wouldn't trust a signal carrying feature of anything smaller than around 4 or 5 mils.

    As for tricks... well... let see here:

    1. Use good transparencies. Ink is not all the same, so what works well for one printer may be particularly poor on another printer. When we first got the Epson printer, we were using transparencies which worked well with an HP 890C, but tracks looked notably somewhat transparent on the transparency when used with the new printer. Choosing a different brand fixed the problem. If you max out the printer driver's quality settings and set the medium type appropriately, and yet you can still see light through your traces, it might be a good idea to give a different transparency brand a test.

    2. Mirror the artwork before printing. If you mirror the artwork, you can place the transparency face down so that the printed side comes in contact with photoresist. If it faces up instead, you will leave a small gap between your mask and the resist due to the finite thickness of the transparency. Surely your light source isn't an ideal point source. Boards still seem to come out adequately if you forget this step, but still, every iota of optimization is worthwhile, IMO.

    3. Don't print from a PDF or other 3rd party printing utility unless you know exactly what your PDF writer driver does. I have one which artificially limits the resolution to 96x96 dpi which is a far cry from what the physical printer can manage.

    4. Using genuine Epson ink might be a good idea. I've never tried ink refills but as noted in 1 it isn't all the same so I suspect you'll get what you pay for if you buy refills.

    Lastly, you probably are already, but you should have a clear chunk of plastic or glass laying on top of your transparency to hold it in close contact with the board. We use a thick chunk of glass and sometimes put large metal food cans on the corners to weigh it down. If you want to buy a new printer for making boards, I think I would recommend buying the Lexmark Z25m printer, which I bought at Wal-Mart for $34.63. [ http://www.walmart.com/catalog/product.gsp?product_id=2188246 ]. It advertises 1200x1200dpi, comes with partially filled ink cartridges (full ones cost very nearly as much as the printer), and it comes with a 30Vdc 0.4A switch mode power supply which can be easily pulled out of the printer's socket. My color ink cartridge is always clogged, which is annoying, but the shear amount of technological goodness for its cost makes it quite worthwhile.

    Howard Henry Schlunder
     
  4. Russell Shaw

    Russell Shaw Guest

    A good list here:
     
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