Hi Marie,

Being a Contract Manufacturer , we had to deal with an equal design.
The board was also 2.3mm and via-holes were used as testpads.

Using the via's as testpads was a disaster. It didn't work.
We tried to cover the via's with solderpaste but that didn't give any
improvement.
The holes were just too big. (forgive me , I don't remember the size).
And solderpaste disapeared in the hole.

Until now this issue still isn't solved.
We decided not to accept any similar design until we find a adequate
solution for testvia's.


So Marie , I can't help you but perhaps you can use this as feedback to your
customer.



Good luck

Jowan Iven




-----Original Message-----
From:   TechNet [mailto:[log in to unmask]] On Behalf Of Marie-Elisabeth MAGNIN
Sent:   vrijdag 14 maart 2003 11:02
To:     [log in to unmask]
Subject:        Re: [TN] 2.3mm thick PCB and BGA

Hi Peter
Thanks for your quick answer. Here are some further explanations :

application is avionics ! I also have concerns about copper plating in the
hole. This is the first point I told my customer. We just met a similar
problem last week on a 1.6mm thick PCB and 0.2mm via holes, the copper layer
broke when changing wrong BGA's.

to save place, the idea is to use via pads as test pads : via holes should
not be epoxy filled, but filled with a conductive material to create a
"large" test pad to contact on the test fixture (large despite a round pad
of 0.6mm diameter). Unfortunatly, it cannot be filled during wave soldering
(the process will only be reflow).

ME Magnin
mailto:[log in to unmask]
http://www.firstec.ch

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