Solder Joint - Lap Joint Calculation / Formula

Solder Joint Design Calculations

Solder lap joint equations for stress in tension, stress in shear, tensile stress in brazed joint.

Solder lap joint equations for stress intension

Preview Solder Lap Joint Strength Calculator

Allowed Joint stress loading equation:

τA = SUS / ks

Joint shear stress equation:

τ = F / ( b · L )

Minimum overlap length of solder surface formula:

Lmin = F / ( b · τA )

Strength check of solder line:

τ ≤ τA

Optimum overlap length formula:

Anticipates that any breakage occurs in the joint itself, and not in the basic parts material equation:

Lopt = max {Lmin, L1 }


L1 = ( SUb · s ) / SUS


SU = joint strength in shear of solder [psi, MPa],
kS = shear safety coefficient factor (typically 2 or greater),
F = transferred force [lb, N],
b = width (minimum) of connected parts [in, mm],
s = thickness of connected parts (in, mm],
SUb = Tensile strength of basic part material in axial loading [psi, MPa],
L = Length of overlap (in, mm).,
L1 = Minimum length of over lap on parts strength (in, mm).


Kent's Machine Engineers Handbook, 12th Edition Design and Production, 1950 Colin Carmichael

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