Test Methods for Tensile Strength of Solder Joints

Soldered connections must stand up to a variety of stresses.

Several methods are available to test soldered connections under different conditions. Solder ball/shear pull strength tests address grain coarsening in solder. Solder ball hot pull tests can focus upon brittle fracture characteristics.

Solder Failure

Soldered connections can often fail in electronic circuits during shipping and military or automotive applications. Shipping can subject the connections to vibration and shocks. Military and automotive applications subject the connections to impact loading. Tests must duplicate such conditions.

Testing Conditions

The testing of electronic circuits often involves inserting a socket or dropping a item to check durability. The tests must include rapid loading of stresses upon the connections since this will be the condition in which there is the highest rate of failure.

Hot and Cold Tests

Traditionally, tests have been performed in a cold state with a shear device centered over the ball of solder and clamping from the outside. Newer methods involve heating a copper wire and inserting it in the ball of solder. Either method can give accurate results. Cold testing appears to be more sensitive to the speed of shearing. Hot testing appears to be unaffected by the speed and can result in more accurate data.

References

• Newman: BGA Brittle Fracture Alternative Solder Joint Integrity Test Methods
• Darveaux, Reichman & Islam: Interface Failure in Lead Free Solder Joints

Resources

• Ormet Circuits Inc.: Ultimate Tensile Strength