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February 1998

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Subject:
Laser via in pad
From:
David Backen <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sun, 1 Feb 1998 10:14:02 -0500
Content-Type:
text/plain
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We are interested in the impact of a micro via dimple or  laser via in BGA
pad.  General construction would consist of a laser via 3 -5 mil diameter
(2 - 4 mil diameter after plating) in a dielectric material 2 - 3 mils thick.

I understand that microvia cleanliness is crucial.  Any moisture or
chemical residue left in the dimple could out gas and produce a void in
the solder ball during the assembly process.

Is this a reliability issue?
Will improved PWB cleaning and packaging methods will be required to
keep microvias clean and dry?
Do PWB  methods exist to minimize the dimple in the PWB?
Do assembly clean or paste methods exist to eliminate voids in the solder
ball?

Thanks for your interest and any response you may have,
Dave Backen

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