Can you plug from one side and coat with LPI from the other?

-----Original Message-----
From: Ofer Cohen [mailto:[log in to unmask]]
Sent: Tuesday, May 27, 2003 8:19 AM
To: [log in to unmask]
Subject: [TN] Plugging under BGAs


Technetters,
Most of our boards carry BGA (pitch => 1 mm). The finish is HASL, which,
from various reasons, can't be changed. The general rule is to plug all the
through-hole vias from the print side, apart of BGA locations, where the
plugging is from the BGA side (mostly components side).

In a new design, there are pairs of identical BGA-packaged components from
both PCB sides, using the same TH vias. I have two options:
1.      To select one side to plug (danger of solder balls under the BGA of
the other side), or
2.      Plug from both sides (danger of over-stress on the hole plating
during the reflow, because of the air pressure inside the hole.

What is your opinion?

Regards
Ofer Cohen
Quality Assurance Manager
Seabridge Ltd.

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