Apparatus and method for detecting leaks in packages

US5307139A · kind A · utility

Assignee

• Laser Technology, Inc. · US

Inventors

• John Tyson, II · Newcastle upon Tyne, GB
• John W. Newman · Newtown, US

Key dates

• Filing date: Jan 15, 1992
• Grant date: Apr 26, 1994
• Expiry date: Jan 15, 2012

Classification

• Technology area (CPC G): Physics
• CPC primary: G01M3/363
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

This invention detects leaks in small, hermetically sealed packages, especially microchips or other packages of electronic circuits. The invention includes a procedure for detecting fine leaks, and a somewhat different procedure for finding gross leaks. To detect gross leaks, one places the package in a chamber, and varies the pressure in the chamber slightly. If the leak is not too big, one wall of the package, such as its lid, initially becomes deformed, but quickly returns to its original position, due to the leak. If the leak is very large, the wall of the package may not move at all. The position of the wall is monitored with an interferometer, such as an electronic shearography apparatus. The movements of the wall show whether there is a gross leak. In the fine leak test, the package is placed in the chamber and the pressure is changed substantially, thus causing the walls of the package to deform. If there is a fine leak, a deformed wall gradually returns to its initial position. Preferably, the chamber is pressurized with helium to increase the sensitivity of the test. The gradual return of the deformed wall can be measured by the interferometer, and the rate at which the w…