Lars,

In my working career we had issues with a SCR mounted in a heat sink 
bolted to a single sided board much like C, normal cycling not sure how 
many but over 10 years the solder would crack at the lead land juncture. 
So with that in mind I would say the best solution is, B, however the 
leads may break at the component.     If you could keep the poly out 
from under the cap would be best.   Next best would be to incorporate 
stress relief between the base of the cap and the board and stand the 
cap off the board slightly, using the poly to support the cap weight. 
It also matters whether the cap is mounted vertical or horizontal in 
relation to gravity.     We had a group of boards edge mounted in a card 
cage and the large block caps fell off of the boards over time, 50 or so 
of them.    Ended up replacing that type and using RTV to support them.

pat


On Thu, Feb 6, 2014 at 5:14 AM, Lars Wallin wrote:

> Hello Technet,
>
> Please check the attach sketch.
> It involves soldering a large capacitor (20 x 30 x 40 mm see enclosed 
> picture) and then mould in the whole board with a warm polyuretan 
> mould mass. The requirement is that the solder joint should withstand 
> 300 cycles (from-40C to +85 C).
>
> Figure A, can not cope with the requirement of 300 cycles. a = 
> polyurethane mass.
>
> Which of the figures B-E do you think would be a better solution? Or 
> would you suggest any other solution?
>
> Looking forward to your answer.
>
> Best Regards
> Lars Wallin
> IPC European Representative
> Location: Stockholm, Sweden
> Phone:  +46 8 26 10 07
> Mobile: +46 70 212 74 39
> Email: [log in to unmask]<mailto:[log in to unmask]>

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