This design does not work in the long run. The worst
Hi Li Yi,
This design does not work in the long run. The worst thing you can do
with a solder joint is to put it in a tensile load because the solder
joint will fail as your test has shown. If you must use a U-shape pin
design it would be best to crimp the end of the pins after inserting
them into the PTH's so that the tensile stress is supported by the pins
and not the solder joint.
Regards,
George
George M. Wenger
Andrew Wireless Solutions
Senior Principal FMA / Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [Office] (732) 309-8964 [Cell]
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of ??
Sent: Friday, March 06, 2009 12:54 AM
To: [log in to unmask]
Subject: [TN] About PTH solder joint strength
Hi Tech netters,
In our design process, We need a heatsink be assembled by a spring which
is held by two U-shape pin headers(each has two PTH pins),the spring
keeps the heatsink and the chipset a stable contact and the U-shape pin
headers are soldered on the PWB.
To be sure the heatsink is assembled good, the spring should supply a
40N load which means each pin of the pin header should sustain about
10N.
Think of the solder's creep properties, we could not use the solder's
mechanical properties such as tensile strength or shear shength to get
the PTH solder joint's reasonable load.
The PTH hole diameter is 36mil and the solder pad is 90mil, the brass
pin diameter is 20mil,the PWB thickness is 79mil and the pin headers are
soldered by hand soldering.
In our test, the U-shape pin headers were loaded with 50N, one faild in
6 hours, one failed in 8 hours, the other two failed in 5 hours.
We lose our faith in this design.
Does this design work in the long run? Any one could give me the way to
calculate the soldered PTH pins' reasonable load? Does a 50N test is to
harsh for the pin header, which means each pin should sustain 25N? Are
there any test methods about this?
Thanks and Regards
Li Yi
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