Re: gEDA-user: SMD soldering challenge status

[DJ Delorie <dj@xxxxxxxxxxx>]

> My first thought is it could be a helpful test aid if it had
> graduated versions between close to chip legs/lands sizes and
> oversize that let lots of solder cling on.  By oversize, I mean only
> in the direction of chip leg lengths, not fatter.

Well, the chips are the expensive parts.  Other than that it shouldn't
be a problem to design a board that had 25 footprints for the same
chip, but with different length pads.  But you're talking $8 worth of
parts just for that one board.

OTOH you can test two different lengths on each chip; one length on
each side.  Assuming you can position the chip carefully enough.  Now,
with a TQFP the alignment is a "given", and you can test four sizes
per chip.  One or two chips should be enough.  For example, one Atmel
ATTINY28L-4AC gives you a 32 pin tqfp (four sides, four lengths to
test) for only $1.51.

None of those options work with a $2 target price.

Now, if we're referring to caps, yeah, we can offer a couple of land
sizes.  0201's are just over a penny each, we could have a couple of
those.  I'm putting two each of the small caps on, I figured I'd use
one "fat" footprint and one "skinny" one.  There's three "standard"
footprint sizes for each part size, I suppose one each would make
sense.  Although, the 01005 parts are 12 times more expensive than the
0204s.  The 0603-0204 sizes have another price break at qty 500 (5 per
kit).


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