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Shear Strength of Tinned Leads

Henry

#25414

Shear Strength of Tinned Leads | 8 August, 2003

I am fairly new to wave soldering and production processes, but I have been tasked with coming up with a calculation involving the shear strength of some through-hole leads. The leads are tinned copper and I suspect that tinning reduces the shear strength, but I have no idea how much. Does anyone have any idea how to quantify the change or know of a resource that might have some information?

Thanks, Henry Cook

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#25415

Shear Strength of Tinned Leads | 8 August, 2003

When I was a salty old fart in the Navy, we sent the babes from the turnip patch off on snipe hunts.

Shear tests are [in my opinion] senseless. The shear stress you measure depends more on the shear rate and on the point where the force is applied than on the grain structure. When shearing a component, you not only apply shear stress, but also roll the component over. This means that shear stress and normal stress are present, again making the results very dependent on where you apply the load.

Properly wetted solder joints have ample strength for anything happening to them (with the exception of single-sided PTH), and there is no correlation between shear (or pull) strength test results and fatigue reliability.

Shear is useful for comparing two processes, materials, etc. Search the conference papers on the SMTA site [ smta.org ] for a starting point.

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