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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