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| Date: | Mon, 20 Apr 2009 06:26:17 -0500 |
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Wayne,
Is this a single resistor failure, or a trend problem? Is there other usage of this part on the board? Is the part near a hardware mounting location? Do you do any type of ESS with performance monitoring over temperature on your product?
Jim Carlson
L-3 Communications
Applied Signal & Image Technology
443-457-1111 Ext. 238
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Goulet
Sent: Sunday, April 19, 2009 1:11 PM
To: [log in to unmask]
Subject: Re: [TN] Bad resistors
I'm just wondering if there are other factors here if the parts are good then bad afterwards.
A possibility is stress factors in handling, use of board racks versus ESD trays, depaneling, press, wash or test.
In this situation the parts fail when put into service.
- I've seen a problem with parts to close to the edge of a board where the FNK depaneler, some call the pizza cutter, set up a vibration that damaged the parts that were too close to the board edge.
- You can also have the problem if the break-away tabs are too close to the edge and the boards are manually separated versus having access to a board router. We changed the panelization and resolved the issue
- I had a situation many years ago where the flux trapped in the epoxy under the caps and resistors changed the value.
----- Original Message -----
From: "Wayne Thayer" <[log in to unmask]>
To: [log in to unmask]
Sent: Wednesday, April 15, 2009 2:54:15 PM GMT -05:00 US/Canada Eastern
Subject: [TN] Bad resistors
I had a bad 0201 part once--resist material mis-alignment with endwrap metallization. That was years ago and 0201 parts were brand new at the time, so I wrote it off.
I just had an identical situation with an 0402 part from a large production order. The part only failed when put into service. How do I protect myself from this situation?
Wayne Thayer
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