Re: gEDA-user: Outsourcing PCB layout

[DJ Delorie <dj@xxxxxxxxxxx>]

> My understanding is that if one uses RoHS parts, then tin whiskers
> can still grow even if one uses good SnPb solder.

*If* the part has tin in it!  RoHS doesn't mean "includes tin" it
means "excludes lead" (and some others).  Although many chip leads are
tin plated, I suppose.

> 5V SRAM parts are a problem unfortunately...

I used Cypress CY7C1049B-20VXC in such a project.  Digikey no longer
stocks them, but they're 20ns 5v parts.

> Thanks for the advice.  So this arrangement is better than having
> the two grounds connected with a 0 ohm resistor or disconnected
> altogether?  What's the underlying rationale?

I wanted EMI isolation, but without the 10M resistor there was nothing
else to keep the pcb's ground anywhere near earth ground.  Plus, with
two generic footprints, you can swap out parts later.  They're
labelled "EMI1" and "EMI2" on the board.

> And I'm still looking for someone to do the layout for a price I can
> afford...  (So far I have no clue as to what price range to expect,
> not even an order-of-magnitude estimate.)

Well, my wife says I'm not allowed to take on new projects...  and I
have no idea what such a job would cost either.


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