Steve,

I would not recommend you only use flux to reflow the BGA...

I have had to rework a lot of BGAs because someone thought that that would be a reliable process for rigid PCBs...

Paul

Paul Edwards

Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Kelly
Sent: Wednesday, June 03, 2009 9:10 AM
To: [log in to unmask]
Subject: [TN] BGA-113 package

Hi All,

We have a rigid flex that has a BGA-113 (microstar BGA) package to be
mounted to it. The routing in this area on the top layer leaves me with
.0005 of soldermask clearance from the edge of the BGA pad and .003 distance
from the edge of the soldermask to the nearest track- in other words I have
.0035 of clearance from pad edge to next track assuming a perfect etch and
perfect soldermask registration.

Having rooted around Texas Instruments web site I believe that it may be
possible to reflow this BGA without adding solder paste to the pad - just
letting the ball collapse do the attachment. If my scenario is correct I
could open up the soldermask and not have too many concerns about bridging
between the BGA pads and the tracks. Any thoughts or comments would be
appreciated.

Thanks Steve Kelly



Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS)

(416) 750-8433 (work)

(416) 750-0016 (fax)

(416) 577-8433 (cell)




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