Hi Lars,

A 'couple' of questions.

1) What type solder?
2) What is the lead to hole ratio?
3) Thickness of the board?
4) Shrinkage/expansion rate of the Polyurethane
5) Does the polyurethane have to go under the device?
6) Mass and dimensions of the cap?
7) CTE and Tg of the polyurethane

And lastly ...... how is the joint failing?

I'm wondering whether the solder joint in "A" would be fine through cycling if the mass of the capacitor body could be supported.
Secondly I'm wondering whether flowing the polyurethane under the device is actually exerting more stress on the joint due to expansion /contraction rather than protecting it.


Sue Knight
Project Engineer

Tel: +44 1256 746747
E-mail: [log in to unmask]
Web: www.sti-limited.comCome and see us at the Southern Manufacturing & Electronics Exhibition

13-14 February 2014, FIVE, Farnborough, Hampshire, GU14 6XL, UK

Stand number F18
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lars Wallin
Sent: 06 February 2014 13:15
To: [log in to unmask]
Subject: [TN] VB: Lödproblem + bild

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]>

The information contained in this communication, and any attachments, may be confidential and/or privileged. It is intended only for the use of the named recipient.

If you are not the intended recipient please contact us.
Tel: +44 (0)1256 768070
Fax: +44 (0)1256 760718
Email: [log in to unmask]

In such an event you should not access any attachments, nor should you disclose the contents of this communication or any attachments to any other person, nor copy, print, store or use the same in any manner whatsoever.

Thank you for your co-operation.

______________________________________________________________________
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] 
______________________________________________________________________