There are a number of separate issue concerning the presence of voids in
solder joints:
1. Can voids be eliminated, or controlled to a certain minimum limit, or
reduced significantly? Process, material and equipment optimization should
be able to help.
2. Are the voids good or bad for the joint reliability? Do they make the
joint stronger? If they do then are there any limits on their sizes or their
total volume with respect to the solder ball? Are too many not good? If so,
then how many are too many?
3. If any amount of voiding is good than can that amount, and the required
void size variation within that amount, be controlled or guaranteed lot
after lot (unless any or no voids both have the same effect on quality and
reliability)?
Syed.
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Sunday, May 27, 2001 6:17 PM
To: TechNet E-Mail Forum.; sahmad
Subject: Re: [TN] Antw: [TN] voids in BGA
At a seminar I recently attended, where the speaker was one Horatio
Quinones (designer of the Power PC CBGA), it was stated that small internal
voids in BGA solder joints are a good thing up to a point, as they render
the joint more flexible under thermal cycling and/or vibration conditions.
The voids must not break out, though. Horation said that even if the voids
rise to the top of the ball and 'desolder' an area between the solder ball
and the Nickel layer, this, too, is OK if there is no break-out.
This struck me as comparable (for all you nature lovers) with hollow
trees. In high winds, hollow trees survive better than trees with solid
trunks. Why? The hollow trees are more flexible than those with solid
cores, so bend more with the wind. Solid trees can't bend so well and are
more prone to being blown over.
Pete Duncan
sahmad
<sahmad@MICRO To: [log in to unmask]
N.COM> cc: (bcc: DUNCAN Peter/Asst
Prin Engr/ST Aero/ST Group)
Sent by: Subject: Re: [TN] Antw: [TN]
voids in BGA
TechNet
<[log in to unmask]
ORG>
05/26/01
06:22 AM
Please
respond to
"TechNet
E-Mail
Forum.";
Please
respond to
sahmad
process can be optimized to minimize or eliminate voids.
Syed
-----Original Message-----
From: Bogdan Gabi [mailto:[log in to unmask]]
Sent: Tuesday, October 17, 2000 1:49 AM
To: [log in to unmask]
Subject: Re: [TN] Antw: [TN] voids in BGA
Just a thought from another point of view- tell me if I am wrog- Seeing
voids in the solder joint you know nothing about when inspecting a BGA by
X-Ray could be something positive if they are not in excess- at least you
know that melting took place. If you have a laminograph and you can locate
them- at the interface or inside the ball- good for you. I don't have a
laminograph and perfect balls without any voids make me suspicious.
Gaby
----------
From: Guenter Grossmann[SMTP:[log in to unmask]]
Reply To: TechNet E-Mail Forum.;Guenter Grossmann
Sent: יום שלישי 17 אוקטובר 2000 10:14
To: [log in to unmask]
Subject: [TN] Antw: [TN] voids in BGA
Tom
Well without a picture of what you called small voids it is difficult
to say something about your solder joints. However, I heard people
saying that there is no such thing like an SMT solder joint without
voids. From the material behaviour and what I know I dare to say that
I wouldn't care for some voids in some of the connections.
Best regards
Guenter
Guenter Grossmann
Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland
Phone: xx41 1 823 4279
Fax : xx41 1823 4054
mail: [log in to unmask]
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