Abstract The surface tension of molten solder is considered to be the source of the force causing the initiation of the tombstoning effect. The contact angle, which varies with the length of the printed circuit board solder land, has a significant effect on the value of the surface tension acting as a force pulling upward on the component. An analytical method is established for the calculation of the conditions of tombstone initiation. The formula derived from the analysis shows that initiation of tombstoning is due to the combined effects of the surface tension; the weight of the component; the dimensions of the component; the length of the solder underneath the component; and the length of the solder protruding from the end of the component. Selected components are used as examples for predicting the conditions of initiation, and these conditions are further substantiated by a series of experiments.
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