In a message dated 2/17/99 11:14:08 AM Pacific Standard Time,
[log in to unmask] writes:

<< We also came across the same problem of f and on. Being subcontr. , it is
difficult if not impossible to relayout or redesign. Problem includes other
combination as well  e.d. SOP to DIP. But in our case , the volume is low ,
redesign is not an option and we are still looking for custom vendor/ solution
provider.

Let me also know if somebody has come up with solution . >>

Hi there!

     I don't know if my response posted back when this post was first listed
(the ISP for our TechNet server has been barfing lately), but there's a
company called Twin Industries here in Santa Clara (1-800-570-8946 and/or for
a picture go to: www.twinhunter.com/products/SMT/8100-SMT9.htm) that makes all
kinds of PCI, ISA, EISA extender cards, prototyping boards, and SMT to PTH
adapters that they sell in Fry's and the like...but most of what they have has
to do with QFP's. BUT, don't fret, they DO have TSOP 40,44,& 56 adapters as
well as something they call a PSOP 44 adapter ?, and a SSOP 56 adapter. Just
so we're all talking apples to apples, what pitch is your SSOP 20? and how is
the part laid-out? Is it a rectangluar shape and the leads are on the short
end? The reason I ask is that sometimes the TSOP, SSOP, QSOP, terms get
confused.

     Twin Industries list the TSOP as being a 20-mil pitch part with it being
rectangular and the leads on the short ends, the PSOP is listed as a 50-mil
pitch rectangular part with the leads on the long sides, and the SSOP is a
31-mil pitch rectangular part with the leads on the long sides. These boards
look like they come in panels of 10-up, and have a SMT footprint that have
traces from each pad fanning out to PTH's...but they don't go back into a
20-pin DIP footprint. You could use let's say the 40-pin adapter and center it
up on the footprint. But I really think that the only way you'll get a hold of
something like that is to have something custom made...even if it is something
that you and I know is simple and basic. I'm just about positive you won't
find something "off-the-shelf". How you would use that adapter with your PCB
is another story...

     As ugly and "Rube Goldberg'ish" as it sounds, it may come down to "dead-
bugging" the IC to the PCB and wiring the thing to the holes. I know, I
know...you're probably gagging right now, but it sounds like there's not a
whole lot of choices. I've had to do some pretty funky things to boards in the
past, but it was only because the customers got themselves into a bind for
whatever reason, and were left with no choice but to do something pretty ugly
if they still wanted to ship product.

     This is a good illustration of why it's so important for a designer to
not only be skilled at creating a good, manufacturable, lay-out for a board,
but to also have a good handle on what's going on in the market with the
components he's specifying on his board.

     I've run across that same sort of problem with a number of proto boards
that I've built here recently...and they're all coming from one design house
that a couple of our customers use (I won't mention any names though..) that
SIMM socket fiasco was the last one I had to deal with that came from there.
Other problems have included laying out SMT pads for PTH parts, or having a
50-mil pitch footprint for a part that is 20-mil pitch, fun stuff like that.

    So ya'll see now why I treat Trang so good...she's had to solder all these
parts for me, and she does a pretty darn good job seeing what I'm asking her
to do. These have all been proto's and only need to work long enough to debug
the design so they can clean the fab up when it rolls. When all the rules are
off and you only need to make electrical contact, you can get pretty creative!
It's actually kinda' fun sometimes...

-Steve Gregory-

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