If I were the Customer, I would rather leave the leads alone and
        rely on the toe and side fillets than even attempt to reform the
        leads.  Particularly on Class 3 product.

        The reforming would require buyoff from the Customer and if
        they're going to buy off on anything, they should buy off on the
        lack of a heel fillet.

        If you get good wetting on the toe and sides, that is by far the
        preferred scenario.

        Depending on how many boards you have with this situation
        (hopefully, not too many otherwise it should have shown up in
        prototyping) it may be better to have the components hand placed
        and soldered for optimum pad to lead interface and to give every
        advantage to good solder filleting.

        Jan Pelchat


______________________________ Reply Separator _________________________________
Subject: [TN] reforming a SOIC
Author:  "Collins; Graham" <[log in to unmask]> at 0UTG0ING
Date:    8/26/98 8:54 AM


Technetter's
Let's say a customer designed a board with the wrong pad size, too far
apart, such that a gull wing lead placed on the pad doesn't have a heel
fillet.  Obviously a bad thing.  A redesign is in progress, but in the
interim it has been proposed that the part be reformed to spread the feet a
bit further apart (by about 20 thou).  Component is a 20 lead SOIC.

My questions and concerns are:
 - the bend will have to occur at the point where the lead enters the
component body, otherwise there will be no clearance between the part and
the board.  How dangerous is this from a reliability perspective (class 3
product, conformally coated)?  Should I take the next few weeks off?  Flee
the country?  Anyone have job openings?

 - do any technetters have suggestions of a half decent way to reform these?
I'm currently faced with doing it to about 100 to 150 parts, and doing it by
hand does not appeal to me due to the variability.

Any other suggestions?  I did consider borrowing some of the Freeze-it that
Steve's using on his diodes, and shrinking the boards, but the reflow
process might disagree with that...

thanks!

Graham Collins

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