Solder ball formation in silicon alloy transistors

This paper discusses the investigation and solution of the so-called "solder ball" problem which has plagued the transistor industry for years. Upon investigating silicon alloy transistors which use tin for electrodes, it was discovered that solder balls (which can cause internal short circuiting of the device) are not necessarily associated with manufacturing procedures as previously believed but are produced by the devices themselves because of the material used in construction. Electrical stresses or low temperatures produce balls in units which were initially free of any foreign matter. This is due to the low-melting-temperature tin alloy used in the construction of the transistor (or other semiconductor). Thus, devices may have balls when put in use and cause equipment failure later. The devices appear good under all measurement; however, when the devices are in use, a mechanical short circuit may shake a ball loose, short circuiting the transistor and making the circuit inoperable.