Solder Joint Failures

Solder Joint Failures


Solder joints refer to the solder connections between a semiconductor package and the application board on which it is mounted. In unmounted devices, it mayalso refer to the package's solder connection features themselves, e.g., solder balls, solder bumps, solder studs, etc, in the context of their attachment to the package body. Since solder joints areone of the most fragile elements of a package (mainly due to the fact that they are small in size and used at high temperatures relative to their melting points), their reliability is of utmostconcern to assembly engineers. A good understanding of solder joint failures is essential in the improvement of any package's solder joint reliability (SJR).

Solder joint failures occur forvarious reasons: 1) poor solder joint design; 2) poor solder joint processing; 3) solder material issues; 4) excessive stresses applied to the solder joints, etc.. In general, however, solder jointfailures are simply classified in terms of the nature of the stresses that caused them, as well as the manner in which the solder joints fail.

Most solder joint failures fall under three majorcategories: 1) tensile fracture due to stress overloading, which is short-term; 2) creep failure due to the application of a long-term, permanent load; and 3) fatigue failure due to the application ofcyclical stresses. Of course, more than one of these stresses can act on a solder joint in a given situation, so solder joint failure analysis can be challenging at times. Add to this the fact thatsolder joint degradation due to other factors such as corrosion can occur.

Solder Joint Fracture Due to Stress Overloading

Solder joint fracturesattributed to short-term stress overloading are mainly those experienced by units subjected to gross mishandling or misprocessing, especially after these units have been mounted on the application board....