Steve,
You can also try using solder preforms, rather than solder, and they are supposed to kinda mitigate voiding. You can check with Alphametals and Indium, they both offer preforms. One of them, (or maybe Nihon Superior?) have a paper on the matter.
Best regards,
Ioan Tempea, P. Eng.
Manufacturing Engineer, Satellite Systems
MacDonald, Dettwiler and Associates Corporation, 21025 Trans-Canada Highway, Ste-Anne-de-Bellevue, QC, Canada H9X 3R2
Tel: +1-514-457-2150 x3556
www.mdacorporation.com
This e-mail, and any attachments, are intended solely for the use of the intended recipient(s) and may contain legally privileged, proprietary and/or confidential information. Any use, disclosure, dissemination, distribution or copying of this e-mail and any attachments for any purposes that have not been specifically authorized by the sender is strictly prohibited. If you are not the intended recipient, please immediately notify the sender by reply e-mail and permanently delete all copies and attachments. This email is for informational purposes only and shall not be interpreted to authorize or conclude a binding agreement between MDA and any other party unless this email contains or is accompanied by an express written confirmation of MDA's intention to enter into a binding agreement, such confirmation shall only be provided by an authorized representative of MDA.
-----Message d'origine-----
De : TechNet [mailto:[log in to unmask]] De la part de Steven Kelly
Envoyé : Friday, February 13, 2015 2:32 PM
À : [log in to unmask]
Objet : [TN] Voids in solder joints
Hi All,
I have some queries that is a little off the wall- at least for us. We are soldering an aluminum nitride thermistor onto a 2 layer flex. Under the thermistor there is mostly a ground plane and there are vias through the ground to the other ground layer (basically thermals) . We also reflow a .015 solid copper stiffener/heat sink on the other ground layer of the flex.
I have read Mr. Hillman's papers on voids but in this case we seem to find if we "smash" the solder paste to reduce the voids when we run the finished unit we pass more thermal cycles - I think in reading Mr. Hillman's papers that makes sense ( I hope).
Solder paste is water soluble SAC 305.
We also find if we glue the thermistor down and not "smash" the solder paste we pass more thermal cycles- I think this also makes sense to me.
We are going to run one more set of tests doing both the smashing and gluing to see what happens.
We need to pass 15000 thermal cycles - -40 to + 85 but we think we are seeing deterioration in the thermistor- any thoughts on how we look for that - what kind of analysis can be done for this?
Thanks. Steve Kelly
______________________________________________________________________
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] ______________________________________________________________________
______________________________________________________________________
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]
______________________________________________________________________
|
