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Daughter Board Attachment??? Help!



Daughter Board Attachment??? Help! | 22 August, 2000

I have a customer that has a wrong pin out on a TSOP32. The Raw PCB is expensive, "time to market concerns", and respin lead times are forcing an alternative solution. He would like to design a "conversion" daughter board with the correct pin out to be placed on the original PCB then attach the TSOP32 I/C to the daughter board.

Has anyone out there done anything like this??? There are 12 I/C's per board and 40 boards to do. The TSOP is a 20 pitch device.

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Re: Daughter Board Attachment??? Help! | 22 August, 2000

Mark: The fact that these daughter boards have to be attached to the TSOP-footprints is what makes the thing difficult cause they will be greater than the original part. One could think that a LCC-design allows for proper routing. But when it comes to soldering those things to the original footprint with 20mil pitch there will be a problem. Haven�t seen LCCs with such a small pitch yet. The easiest way considering time to market and the best solution under technical aspects would be rerouting the PCB. The ugliest way but maybe the cheapest is to glue them backside down to the board and patch with wires (40x12x32 calls for someone with outstanding patience and I hope you have a good microscope with enough space to do the work).

Keep on working on your customer untill someone here comes up with "the solution" that�s even better than redesign which will most likely to be done anyway cause this seems to be a prototype. "The mistake isn�t that serious when it can be fixed somehow" isn�t that the true motivation behind this all. Offer one or two boards prototyped with patches while they fix the problem with the PCB.



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Travis Slaughter


Re: Daughter Board Attachment??? Help! | 22 August, 2000

Depending on how wrong the pinout is another possibly a little less ugly option would be to bend the wrong pins up then wire them to the correct pads after reflow of the correct pins. You may want to trim the ends of the pins a bit use heat shrink or in some other way prevent them from being able to short against anything around them. I have done lots of the kinds of daughter boards your talking about and it works great to replace a obsolete PGA with a PLCC but I think your asking for trouble trying to solder a board to a 20 mil TSOP pad design .

Hope this helps. Travis

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