Technetters,
I have received a query from a customer : he is designing a PCB for a BGA ,
as described below :

35 mm ´ 35 mm, cavity up, 352-pin plastic ball grid array (PBGA) package.
Package Outline 35 mm ´ 35 mm
Interconnects 352
Pitch 1.27mm
Solder Balls 62Sn/36Pb/2Ag
Solder Ball Diameter 0.75 mm
Maximum Module Height 1.65 mm
Co-Planarity Specification 0.15 mm
Maximum Force 6.0 lbs. total, uniformly distributed over package (8
grams/ball)

He needs a 2.3mm thick PCB, 10 layers,  4 or 6 of them with 70um copper.
He wants 0.25 mm via holes underneath the BGA, which must be also used as
test pads.
For this reason, he wants these holes filled with conductive material to
increase the contact surface.

He has contacted his usual PCB manufacturers who are not really confident
with such a design.

Who has any experience abour this topic ?
Which solution would you propose ?

Waitnig for your answer,

Kind regards

Marie Magnin

FIRSTEC SA
Rue du Grand Pré 70
CH 1211 Genève 2

Tél.   : +41(0)22 918 36 85
Fax   : +41(0)22 918 36 93
mailto:[log in to unmask]
http://www.firstec.ch

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