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May 2000

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Subject:
From:
Richard Tilbrook <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 31 May 2000 11:36:11 +0100
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If you are doing X-ray with a dedicated operative / inspector plus keeping the
image with the PCB then great, this tells you if there is a short, cracks, etc,
whatever the quality of the x-ray machine allows you to do (and what it lets you do
is proportional to cost). From my LIMITED understanding, this is an inspection tool,
 for testing each and every PCB where hidden faults (like under a BGA) are a
possibility.

For process control, it is advantageous to be able to look at the reflowed ball on
a BGA. You inspect joints on every x PCBs to ensure the BGA balls are reflowing
correctly, as compared to other joints on the PCB. The most publicised method of
doing this is to use an "Ersascope" by ERSA. With all the bits and bobs, you can
framegrab onto PC (supplied) and compare to a database thats supplied. The viewer
can go 8 balls deep, the database can offer suggestions for your process. Before
you go making any decisions, I believe that there are alternatives on the market. I
cannot make a recommendation as I haven't looked that closely at the problem.

Regards,

Richard Tilbrook

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