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May 2001

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Subject:
From:
Jason Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 10 May 2001 07:59:58 -0500
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OK, guys, here's one.
Why is it so important for local fiducials to be placed near diagonal corners of BGA's. The keyword here is "SO". I've performed studies in the past detailing the natural tendency of BGA's to self-align during reflow. It's even lead to me to work on a patent concerning a BGA rework preform. What I'm wondering is....ssop's, tssops, qfp's, etc. have greater impact on placement quality when misplaced. And they do not self-align!!! I do, however, understand that BGA's balls are not easily seen once placed (you can only see the edges). But my point that I'm getting to is.....wouldn't you want local fiducials more at the parts that will not "self-correct" themselves during reflow than at the parts are more forgiving? Just wondering.


Jason Gregory
Software Specialist - NPI Group
SCI Systems/Plant 2
13000 S. Memorial Pkwy.
Huntsville, AL. 35803
(256) 882-4107 x3728
[log in to unmask]

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