The Process Origin of Impurities in Hermetic Electronic Device Packages 670221
Many investigators who have studied the reactions of various gases and contaminants on solid state device operating characteristics have not particularly concerned themselves with the process origins of these gases and contaminants. Analysis of the contents of hermetic device packages at Autonetics has revealed large variances in composition and concentration of these gases and contaminants. Once the gas or contaminant had been established as deleterious to the operation of the device, it was necessary to determine its origin. It was assumed that all deleterious materials of concern to the study were process oriented. The techniques utilized by various manufacturers to make hermetic packages were compared for common practices associated with the closure techniques, the ambients, the temperatures, and their controls. These were carefully evaluated and compared to the analyses performed using mass spectrographic and gas chromatographic techniques. Also, solid contaminants trapped inside the device due to processes occurring prior to the seal operation were traced to their origin using analytical techniques including the electron microprobe. Results of these studies indicated major sources of impurities to be (1) dry box ambients, (2) outgassing for metal surfaces, (3) residual processing solvents, (4) weld flash, etc. This paper describes some examples of joint studies involving Autonetics and its suppliers which resulted in corrective actions which eliminated these process oriented impurities. For example, open aluminum interconnects in integrated circuits were determined to be caused by chloride corrosion present as a result of incomplete cleaning processes.