Hi Chris,
How hot is hot?
With a thick=stiff spreader, co-planarity will be forced by the solder creeping rather fast at the higher T's.
Werner
-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
To: Werner Engelmaier <[log in to unmask]>; [log in to unmask] <[log in to unmask]>
Sent: Tue, Sep 14, 2010 9:34 am
Subject: RE: [TN] Bergquist Gap Pad
Werner,
Yes, definitely agreed.
We and our customer had been ignoring this part of the study for that reason. But, we have picked up on some planarity issues between the heat spreader (it’srather thick) and the board. Also the clips are rather low force.
So, brainstorming.. I thought there might be a differentialcompression across the BGA, combined with all the differential CTEs… Thesethings got hot.
Just a thought.
Wondering if anyone had been there and got the t-shirt already.
Chris
From: Werner Engelmaier[mailto:[log in to unmask]]
Sent: Tuesday, September 14, 2010 9:17 AM
To: [log in to unmask]; Chris Mahanna
Subject: Re: [TN] Bergquist Gap Pad
Hi Chris,
These clips would put the SJs into compression—that means that even whenfatigued to fracture, you will not see a functional failure.
Werner
-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Sep 13, 2010 10:25 pm
Subject: [TN] Bergquist Gap Pad
We are working on a memory module FA. Sandwich looks like this:
top of clip
Ni plated Cu heat spreader (goes across all 8 BGAs)
Gap Pad
8 BGAs in a single row
board
Gap Pad
bottom of clip
Has anyone seen more than [expected] damage after natural field cycling (maybe)
caused by the gap pad? The material appears to be patented for low-modulus,
high W/mk but...
Chris
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