Some Metallurgical Studies Related to the Surface Mounting of Electronic Components

The introduction of high density surface mount technology may lead to a number of metallurgical problems. This paper considers two aspects which are currently being actively discussed. Firstly, incompatibility in expansion properties of the materials used and severe thermal cycling may induce creep and fatigue stresses on soldered joints, and the merits of different alloys are considered. Secondly, the necessary thermal treatments such as burn‐in and elevated service temperature can lead to intermetallic compound layer growth between the solder and the metallised layer on components which may be considered a potential source of joint strength reduction. Mention is also made of the different visual appearance of joints to chip components compared with conventional soldered joints.