Andy,
First question is What's a lot of RF power?
I've seen where 125+ watts can vaporize solderjoints, copper traces, vias, etc.
Even though you only measured 170C, I would not be surprised to find out the joint got much hotter very quickly and failed.
Any clue as to where the missing solder went to (I expect not)?
What size is the cap?
How wide is your trace in and out?
What is the finished copper weight?
Great pics by the way.
Good luck,
FNK
Frank N Kimmey CID+
Electrical Engineer / PCB Design
VeriFone Inc
1400 W Stanford Ranch Road, Suite 200
Rocklin, CA 95765 USA
W: 1-916-625-1818
M: 1-916-833-9877
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Giamis, Andy
Sent: Wednesday, September 06, 2017 9:25 AM
To: [log in to unmask]
Subject: [TN] Crazy Solder
Hi TechNetters,
Here’s something I have not seen before.
I have seven different ‘theories’ for what’s happening here.
Three of which do not involve mythical creatures, illegal substances or the alignment of celestial bodies.
This capacitor is on a path that sees a lot of RF power.
The unit went through 20 cycles of -70C to +115C while at nominal power. Temperature sensing suggests this device could be hitting 170C.
No, we normally don’t test to these extremes.
The PCB has ENiG finish and the solder is SAC. This is normal SMT, no rework.
I think I know in general what happened, but I am surprised.
I don’t have an explanation for the formation of the big pocket on the right.
Has anyone ever come across any solder joints like this?
Thanks Steve for uploading the pictures (links below).
http://stevezeva.homestead.com/pockets_25.jpg
http://stevezeva.homestead.com/Pockets_CS.jpg
http://stevezeva.homestead.com/Pocket-left.jpg
http://stevezeva.homestead.com/Pockets-right.jpg
Best Regards,
Andy
Andrew C. Giamis
Senior Failure Analysis Engineer
CommScope
2601 Telecom Pkwy
Richardson, TX, 75082, USA
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