On Tue, 10 Apr 2007 00:34:34 +0200, Adam Seychell
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a_seychell@...> wrote:
> I'm wondering what other people are doing out there for PCB that use
> SMD. I finding over the years my PCBs need smaller and smaller tracks to
> suit the ever shrinking SMD packages. Well, we know BGA is out, because
> that needs a multilayer board. Luckily, only the really big chips are
> BGA. These days 0603 chip resistors/caps are the norm. Often I need to
> run a trace under a 0603, or my latest project has two 0.5mm pitch TQFP
> (leaded) and QFN (leadless) packages. I'm wondering how other people
> deal with PCBs for SMD.
> I use photomasks from a inkjet printer. Recently I bought a Canon MP810,
> and noticed the resolution and line edge sharpness was a noticeable
> improvement over my old printers (Epson Stylus 660, Canon i550). Its
> definitely true 1200x1200 dpi resolution. Using "3M Universal
> Transparency" film, and printing with the driver set to "Photo Paper
> Pro", "Quality 1" and Cannon OEM inks, I can just get away with
> 0.008"(0.20mm) lines/spacings. 18um foil instead 36um makes etching fine
> traces a lot better.
> Adam
8 mil is no problem with toner transfer, but my printer won't go much
below that (6 mil maybe). I usually use 10mil smallest size unless i
really need less.
0.5mm qfn and stuff works just fine, only trouble are thermal pads (lack
of VIAs).
I avoid using passives smaller than 0805 (why should i?).
I don't think pitch will go much lower, but we will see more and more
trouble with thermal impossibilities. A case the size of a pinhead can not
cool the same as a to220 case, no matter what the manufacturers want to
make us believe.....
ST