All -

I am in the process of trying to get a feel for what the industry standard
(or even personal gut feels are) regarding the production of assemblies that
require BGA parts.

For example, within our organization, we have recently had some interesting
debates related to the old school philosophy that more paste is always
better in production versus the opposite philosophy of less is better
because it drives tighter placement tolerances and a better solder joint
with the BGA ball.

So, at this point, I am trying to figure out the best direction in which to
drive our manufacturing processes.  Seeing that I am certainly in the infant
stage of BGA knowledge, I figured that I would pose the following questions
to the 'Net:

Assuming standard eutectic solder:

1.) If the BGA pad dimensions on a PCB are, say, 16-mils, do you recommend
cutting stencil aperture size to be greater than the pad size (say,
17-mils), cut the aperture exactly the same size as the pad (an exact 1 to 1
ratio) or do you recommend a slight undercut (say 15-mils)?

2.) Do the actual production equipment pieces dictate the solder amount?
Example, say one manufacturing line is antiquated equipment versus a
different line that has newer equipment?

3.) Assuming Class 1 BGA components are built into the process (example,
parts may have already built in voids in the outside of the BGA balls - but
clientele and pricing allow this to be acceptable), will extra paste in this
case be better - will the additional paste reflow into the assumed outer
voids and make a more solid connection?


Appreciate all responses.

Thanks -
Dacia


Avant Technology - OEM Module Services
[log in to unmask]
Dacia Leanne Schoolfield
Quality Manager

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