Yes I agree - also look at the geometry of the BGA pads - do they make
the device specs and watch for "hot-dog" shaped ball to via runs, these
can starve paste from the standoff and create opens, usually on finer
pitch arrays.
Jeffrey Bush
Director, Quality Assurance and Technical Support
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302-1890
Tel. 802.257.4571.21 Fax. 802.257.0011
[log in to unmask]
http://www.vtcircuits.com
-----Original Message-----
From: Misner, Bruce [mailto:[log in to unmask]]
Sent: Wednesday, April 07, 2004 9:52 AM
To: [log in to unmask]
Subject: Re: [TN] BGA soldering issue
I have seen BGA intermittents caused by excessively large voids within
the BGA balls (verify with X-ray) especially if via in pad was used.
Also black pad is a possibility if the finish was ENIG.
Regards,
Bruce Misner
-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Wednesday, April 07, 2004 9:34 AM
To: [log in to unmask]
Subject: Re: [TN] BGA soldering issue
Hi SJ!
I've heard of this problem more than just a few times. Former TechNetter
Earl Moon ran across this problem and solved it easily.
You can go to: http://www.stevezeva.homestead.com and look at "Creative
Engineering" at the top left-hand picture there. What? You don't want to
fix the problem like Earl did? Why not?
Just kidding...Earl did what he had to do so the board would play. I
believe in his case it was more part related than any manufacturing
issue.
I've had an intermittent connection with a BGA once. It was a VERY
expensive 560-ball Xilinx device, that I really didn't want to have to
remove and replace because of it's price. The part had eutectic balls.
Test said the part would play when pressed on. So I figured I had
nothing to lose by fluxing the part liberally beneath it, and then
taking it over to my rework station to reflow the BGA and hope that
maybe the intermittent connection would heal itself. The soldering gods
were with me that day and it worked. The board passed the initial test
after rework, as well as subsequent tests after thermal cycling.
Some days you're just lucky I guess...
-Steve Gregory-
> Dear Technetters,
>
> We encountered BGA chip having intermitten contact issue in our
prototypes.
> When we pressed hard on the BGA chip, the prototype worked ok. We need
advice
>
> on how to tackle this issue from prototype building's point of view.
> What measures should be taken to make sure "no contact issue" during
> prototype building.
>
> Your advice is very much appreciated. Thanks in advance.
>
> Best regards,
> SJ Liew
>
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