We once had the same problem. 
The production of a cca worked out right.
After the transfer to an EMS problems occured. Solderbeading. while he was 
using the same layer, same solderpaste, same components. The EMS changed 
stencil design from homeplate to negative homeplate to standard 1:1, 
reduced the aperturesize, used our stencil. Varied the viscosity of the 
solderpaste, placement pressure for the components, solderingprofile. 
Nothing worked out right, until he renewed his airconditioningsystem.

Kind regard

Frank 



Von:
Rob Strecker <[log in to unmask]>
An:
[log in to unmask]
Datum:
27.01.2010 17:14
Betreff:
[TN] Solder Ball Under Chip Cap
Gesendet von:
TechNet <[log in to unmask]>



We recently received a call from one of our customers that their boards
are failing Hi-Pot test.  They sent us a picture of a solder ball under
one of the chip caps (package 1825).  Apparently it's present on all 50
boards we built and always in the same place.  We are using leaded paste
for this build and the stencil we received was from the previous
manufacture who could not fix the problem and went to hand soldering the
part (info we got after the fact).  I have inspected the stencil and it
looks fine.  The apertures are a 1:1, so the only thing I can think of
is getting a reduction of some kind on the stencil.  I will send the
picture to Steve to get it posted.

 

Thanks,

 

Rob Strecker 


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