Hi Prashat,
There are too many variables involved for any kind of standard to be practical.
What you need to do is remove address the trouble directly. For these chip components, there is way more solder present to make a proper mechanical and electrical connection.
The solution—much more important with the much stiffer SAC solders, is a reduction in the size of the solder fillets. Actually, a total elimination of the fillets is even better with the solder joints looking more like mini-solder balls.
To accomplish this, radically reduce the size of the soldering pads on the PCB—of course, this is not possible if you still use wave soldering.
Because of the high soldering T's required for SAC's, reducing the number of solder T excursion is very important, and wave soldering in many cases is no longer necessary.

Werner


 


 

-----Original Message-----
From: prashant chopra <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 13 Nov 2008 2:37 am
Subject: [TN] 0603 capcitor cracking










Hi,
 
We are using a 1.6mm FR4 material PWB. This PWB is held onto the plastic base 
with 2 hook and 2 snaps.  We have 10 localised point on the board for the FFT 
testing. 
 
The overall force of the 10 pogo pins which is applied from below on the PWB 
during testing is 3KgF.   
 
We have 2 nos. of 0603 capacitor sitting on the other side of the board directly 
above these test points.   We are seeing some displacement of the 
PWB when the 
pogo pin force is applied.  
 
The query is would this force cause the capcitor crack or solder joint crack of 
the 0603 part?  Does anyone have the data as to how much stress or strain on the 
0603 part will cause it to have the crack on the component or solder crack. The 
component is ROHS and paste is leaded.
 
Thanks in advance to everyone for the inputs.


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