Hi Bob,
so it was you with this ol $B!- (J oil trick I recently cited ond not Earl the
Moonman, sorry for not remembering and citing correct.
Although I often remember the good things my memory for names seems a bit
weak.
Hope you don $B!- (Jt forgive me
Wolfgang
-----Ursprungliche Nachricht-----
Von: Bob Willis [mailto:[log in to unmask]]
Gesendet am: Freitag, 16. November 2001 18:59
An: [log in to unmask]
Betreff: Re: [TN] BGA voids
We have experienced voiding with via in pad, I know it ws stated that the
pads don't have vias in them but if they did they can somtimes gass through
the plating, its not the air traped by the paste. I have investigated this
with my old outgassing oil test which showes up the problem and will
contribute to voiding.
Bob Willis
See us at APEX 2002 www.bobwillis.co.uk/workshops/apex/apex.htm
<http://www.bobwillis.co.uk/workshops/apex/apex.htm>
www.bobwillis.co.uk <http://www.bobwillis.co.uk>
Tel: (44) 01245 351502 Fax: (44) 01245 496123
Single solution to your seminar, conference or roadshow
www.seminar-registrations.com <http://www.seminar-registrations.com>
----- Original Message -----
From: Peter George <mailto:Peter George [log in to unmask]>
[log in to unmask]
To: [log in to unmask] <mailto:[log in to unmask]>
Sent: Friday, November 16, 2001 8:52 AM
Subject: Re: [TN] BGA voids
Hi, Peter,
I was at a seminar earlier this year where BGA's and their solder joints
were discussed at some length. The received wisdom is that voids in solder
joints are not of themselves a 'defect' unless they break out through the
side of the ball. In fact, they make the joint more "flexible" - better
able to withstand creep fatigue - so are beneficial, up to a point.
What causes them is often outgassing of volatiles in the solder paste flux
during the reflow process, though the size and shape of voids increases and
changes when there are via-in-pad features as well. About the only way to
detect them is by X-ray, and to judge from previous TechNet postings, there
are some pretty fancy machines around now that can give you a very much
clearer view of the balls than is normally the case ... if you have cash to
splash!
Peter Duncan
Peter Lee
<ppwlee@YAHOO To: [log in to unmask]
<mailto:[log in to unmask]>
.COM> cc: (bcc: DUNCAN Peter/Asst
Prin Engr/ST
Sent by: Aero/ST Group)
TechNet Subject: [TN] BGA voids
<[log in to unmask]
ORG>
11/16/01
04:25 PM
Please
respond to
"TechNet
E-Mail
Forum."
Hello,
I am encountering voids after reflow on several micro BGAs on one PCA
product. The voids that I $B!G (Bve observed (with Xray) contribute to as
high as
60-70% of the joint area. My reflow profile was designed by running a
sample board with dummy components and thermalcouples attached right at the
joint. I also inspected the PCB lands and didn $B!G (Bt see any via on pad.
Does anyone know the possible reasons for voids formation in BGA (micro)
reflow?
In general, in step by step how would one trouble shoot such a defect?
Rgds,
Peter
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