Failure Analysis of Wire Bonds

Failure analysis of wire bonds has an important part to play in determining the causes of microelectronic device failure and ways for making and using devices to achieve greater reliability. Several tests and procedures used in the failure analysis of wire bonds are reviewed. Some of the inferences. about possible causes of permanent or intermittent failure that can be drawn from such tests, particularly those involving inspection with an optical microscope and with a scanning electron microscope, are discussed. Some attention is paid to the effects on the reliability of the wire bond of the growth of gold-aluminum intermetallic compounds, of Kirkendall voids, and of the use of poor materials, poor processes in making the wire bond, and poor control over the processes used. Also reviewed are some metallurgical sectioning techniques and a variety of methods used in opening the commonly used packages and in exposing wire bonds that are encapsulated in epoxy, phenolic resin, or silicone materials.