RE>>Assy: Ball Grid Array 9/27/96
We also have assembly shops who have the capability to reball BGAs, but in our experience, this needs to be combined with the ability to retest the devices prior to replacement.
Greg Bartlett
Mercury Computer Systems
Chelmsford, MA
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--------------------------------------
Date: 9/26/96 5:25 PM
To: Greg Bartlett
From: Tony Sturgeon
We have removed, reballed, and replaced many BGAs for numerous
customers without a hitch. We do not rely on Winslow Automation's
preforms, but have our own tool and process to reball BGAs. Our tool
is easily adjusted to any array pattern, keeping tooling costs
low. In all of the parts we have removed, reballed, and replaced, we
have not seen damage due to numerous reflow cycles. If you would
like more information on BGA processes you may contact Axiom's
Engineering Manager, Christina Piasky ([log in to unmask]), or Doug
Robertson, Senior Account Executive([log in to unmask]).
Date: Tue, 24 Sep 1996 18:21:17 -0500
To: [log in to unmask] (TIM MENDENHALL)
From: [log in to unmask] (Jerry Cupples)
Subject: Re: Assy: Ball Grid Array
Cc: [log in to unmask]
Tim Mendenhall asked:
> We are currently establishing our BGA process and have several
> questions:
>
> 1. What is an acceptable amount of times a BGA device can be
> reworked, reballed, and remounted?
Zero (for PBGA's) - you get one shot.
I suppose you may want to disprove the above. Go for it - see
http://www.smtnet.com/smt_forum/messages/59.html for a suggestion. I guess
there is a company Winslow Engineering in Sanata Clara, CA who has
something called BGA "SolderQuik" 408-496-6636. Their trick is a paper
carier for a matrix of solder balls. The paper carrier (with solder balls)
is placed on the clean, fluxed underside surface of the BGA and reflowed.
After reflow, the carrier is softened with water and peeled off, leaving a
matrix of reflowed solder spheres on the BGA. Doug Peck says it works well.
My comments based on the fact that Motorola told me they would not reball
any PBGA parts for us, and that they considered it NR. We have not tried
the above. Seems to me that you are talking about 3-4 reflows and a lot of
labor, high risk of part/PWB damage. Let me know how you make out.
> 2. What are the critical elements to consider and why?
design of the pads at board layout
moisture sensitivity of the part (pkg and handling prior to assembly).
reflow profile - (low peak temp), tight delta T.
good rework equipment/process with profile capability
> 3. What is the maximum number or percentage of solder voids allowed
> per solder joint (bump) connection?
depends on void size - some are inevitable, I have heard max dia 1/4
collapsed ball dia as a guideline.
> 4. Has IPC released a BGA standard?
sorry, don't know, but I would guess it is out or in work. Good excuse for
more committee meeting in Florida.
cheers,
Jerry Cupples
Interphase Corporation
Dallas, TX USA
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Tony Sturgeon
Axiom Electronics
3003 SW 153rd Dr.
Beaverton, OR 97006
Phone 643-6600
Fax 641-0572
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Subject: Re: Assy: Ball Grid Array
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