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March 2000

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 28 Mar 2000 14:19:19 -0500
Content-Type:
text/plain
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text/plain (78 lines)
Ken,
First I don't think you really mean to say the part leads are made with
eutectic solder or Alloy 42.  The leads are either Alloy 42 or copper, with
a lead finish of eutectic solder, other tin/lead solder alloy or maybe even
TI palladium.

So you have sufficient pads size for good fillets, good soldering of other
parts, good profile and heel fillets.  Hmmm.  My question would then be, do
the failures look like the lead has pulled right out of the fillet, with
bare lead frame material showing.  If this is the case and the leads are
indeed Alloy 42, then this has been seen before, is related to the final
processing of the Alloy 42 and I think has been discussed here on TechNet.
Check the archives.

regards,
Bev Christian
XLTEK

-----Original Message-----
From: Ken Patel [mailto:[log in to unmask]]
Sent: March 28, 2000 1:27 PM
To: [log in to unmask]
Subject: [TN] Solderability of TSOP...


Guys,
We have encountered problem related to component solderability, looks like!
We are using Cypress Semi TSOP (SRAM-SM 71016 64kx16, ASYNC TSOP-44). This
part has very small foot area which make a direct contact with the pad on
the boards.

The problem we have encountered is that many boards fail at ICT but will
pass once we touch it up using solder iron. Solder at the TSOP location
looks good and also in the surrounding vicinity. I do not see any profile
problem. There is no toe fillet but I can see the heel filet rising on the
lead. Pads are designed longer so that parts made by others can fit too.

What can be possible causes of the problem? I tried look at the WEB but
looks like parts are made using eutectic solder and not Alloy 42 but can't
ruled out it was not specifically mentioned.


re,
ken patel
______________________________________________________
Ken Patel                       Phone:  (408) 490-6804
1708 McCarthy Blvd.             Fax:    (408) 490-6859
Milpitas, CA 95035              Beeper: (888) 769-1808

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