Hi Joe - as Doug would say "it depends" as there are a number of inputs on 
the collapse of a solderball under a BGA or CSP (i.e. reflow temperature, 
pad size, solder paste deposit, component mass, etc.). However, as a first 
order approximation, you can use a 2-3 mil decrease in solderball diameter 
for tin/lead eutectic solder alloys (i.e. a 30 mil diameter will reduce to 
a 27-28 mil diameter). We have observed the "2 mil" number over a large 
number of DOEs and production investigations using metallographic 
cross-sections to confirm the value. Its not a perfect value but gives you 
a place to start.

Dave Hillman
Rockwell Collins
[log in to unmask]




From:   Joe Macko <[log in to unmask]>
To:     <[log in to unmask]>
Date:   11/28/2012 09:55 AM
Subject:        [TN] estimating collapsed solder ball diameter change
Sent by:        TechNet <[log in to unmask]>



Good morning.

 

I am trying to estimate the typical change in a solder ball's diameter
after reflow. IPC-7095B has great discussion about the typical change in
a ball's height after reflow but I did not see anything about
diametrical changes. Maybe there is another IPC document that addresses
this.  Factors such as package weight, # of solder balls, ball alloy,
etc. influence collapse so I am sure there is no quick answer buy maybe
there is a rule of thumb to estimate the diametrical change.

 

Look forward to any advice. thx

Regards,

-Joe

 

 


"This e-mail and any attachments are solely for the use of the addressee 
and may contain L-3 proprietary information that may also be defined as 
U.S. Government export controlled technical data. If you are an unintended 
recipient of this e-mail, use, disclosure or distribution of its content 
is prohibited. Please notify the sender by return e-mail and immediately 
delete this message."
 

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________




______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________