The inverted T-joint for surface mount connectors

The stresses in inverted T-shaped surface mounted solder joints are computed by means of a beam-on-elastoplastic-foundation model. The stress in the inverted T-shaped joint is shown to be distributed more evenly than in the L-shaped joint, and hence, the inverted T-shaped joint gives a much higher vertical pull strength than the L-shaped (gull wing) lead. Pull tests experiments on these two types of joints support the analytical result. It is shown that a simple pull test can give an erroneous strength indication if rotation at the loading point is permitted