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April 2010

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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Tue, 20 Apr 2010 13:21:08 -0400
Content-Type:
text/plain
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text/plain (223 lines)
Hi Inge!

Have your picture posted here:

http://stevezeva.homestead.com/XILINX_Daniel_28.jpg

I've not looked closely yet, I may look at them closer and tell you what I
see.

Steve

P.S. Added a couple more names to the Technetter page today. Still more
room...

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Tuesday, April 20, 2010 12:36 PM
To: [log in to unmask]
Subject: Re: [TN] SAC Shrinkage Voids in BGA Balls

High all.
Are u sure the balls are not shrinked even before soldering? I inspected 
hundreds of packages before soldering and found them to be like the neck of 
a Galapagos turtle.  Both SAC and PbSn look all the same.
I'll send  a typical picture to Steve and ask you all: do you have shrinked 
balls too before action is taken?
I get question frequently from the operators, because they want see shiny 
balls and not old prunes. Myself, I think the wrinkled balls has not 
significance.

Inge



--------------------------------------------------
From: "Werner Engelmaier" <[log in to unmask]>
Sent: den 20 April 2010 08:55
To: <[log in to unmask]>
Subject: Re: [TN] SAC Shrinkage Voids in BGA Balls

> Hi Dave,
> A shrinkage void in an ingot occurs where it solidifies last---in its 
> center.
> The same is true for SJs, except that they do not necessarily cool from 
> the outside in. but a connected to various heatsinks and reservoirs---the 
> component is typically a heat sink [coolest] and the PCB is a reservoir 
> [hottest], with various heat transfer conditions on the surface due to 
> forced air/N2.
> Overall, SJs tend to solidify first at their surface; hence, most 
> shrinkage voids are to be found there.
> Werner
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: David D. Hillman <[log in to unmask]>
> To: [log in to unmask]
> Sent: Tue, Apr 20, 2010 10:13 am
> Subject: Re: [TN] SAC Shrinkage Voids in BGA Balls
>
>
> Hi Bev - in theory, a shrinkage void in a solderball is the same physics
> as a shrinkage void in a aluminum or steel casting so no, the shrinkage
> void  would not have to necessarily always reach a surface. However, after
> looking at several hundred SAC BGA/CSP cross-sections, I have nearly
> always (99.999%)  found a path of a shrinkage void to the solderball
> surface. Because we have a very limited and very small molten solder
> "volume", I think you will find a surface connection.  And I guess I'll
> bite - why the question?
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
>
> Bev Christian <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 04/20/2010 08:16 AM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> Bev Christian <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [TN] SAC Shrinkage Voids in BGA Balls
>
>
>
>
>
>
> TechNetters,
> Do all SAC shrinkage voids in BGA balls reach/start at the surface of
> the ball?  I realize I may be stumped by a 2D cross-section of a 3D
> phenomenon, but I thought I would ask this august body.
> Bev
> RIM
>
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