Dear colleagues;
 
Steve Gregory, could you please upload the enclosed picture?
 
Solder become perturbated / cracked after thermal cicling:
 
This picture corresponds to a plane (not circular) conector terminal
solded to a pcb pad ENEPIG finished.
The connector terminal has been gold removed by twice pretin.
Solder used is Sn63Pb37.
Thermal cicling: 50°C to 125°C
 
As picture showed there are stretch marks toward left direction and
showed solder crack.
 
Our provider reported temperature didnt pass over 125°C and solder used
63/37.
 
Question:
 
How could these kind of gooves or stretch marks have been produced
taking into account they are just toward one direction (left) and of
considerable length?
Just mecanic stress?
Temperature overpassing on any cicle?
Need of use of different alloy, ie.: In, Bi etc? 
Provider reported the process is being useed from them since long ago
(same solder alloy, temperature, pcb, terminal conector, thermal
cicling) but this is the first time they faced with such a cracking.
 
Do you have any comment in order to anlyse/solve this trouble.
 
Appreciate your feedback we are in middle of a providing acceptance
tests space quality level (IPC class 3).
 
brgds,Ricardo
 


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