IEEE Transactions on Advanced Packaging, Vol. 31, No. 1, pp. 14-21, 2008

On Ultra-Fine Leak Detection of Hermetic Wafer Level Packages

Arindam Goswami
Bongtae Han

Theoretical and practical ranges of leak rates measurable by the helium mass spectrometer are characterized. The effect of noise due to: 1) background helium present in the spectrometer and 2) desorption of helium that attaches itself to the specimen surface during bombing is quantified experimentally. The results guide a framework to extract the true leak rate from the measured leak rate profile. An optical interferometry based hermeticity measurement technique for ultra-fine leaks is proposed. The setup to implement the technique is described and a preliminary experimental result is reported.

Index Terms: Helium fine leak test, hermeticity, optical interferometry, theoretical and practical limits, true leak rate.

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