Solder Joint Embrittlement

Alloy Shift

Diffusion of copper or nickel into the tin matrix changes the internal atomic structure of the joint. Developing solder joint embrittlement happens faster when assemblies stay at high operational temperatures for prolonged periods. The resulting chemical compounds are naturally stiffer than the original soft metals used in the initial assembly.

Impact Tolerance

Stiffness prevents the joint from absorbing the energy generated during a drop onto a hard surface. Severe solder joint embrittlement leads to clean fractures along the interface that completely isolate the component from the board. Physical inspection cannot always see this problem until the mechanical event occurs.

Growth Bound

Surface finishes such as gold help prevent initial oxidation but can contribute themselves to this hardening phenomenon. Controlling solder joint embrittlement requires limiting the thickness of specific metals that migrate into the liquid phase during soldering. Testing checks for these elements using chemical mass indicators.