The thermoacoustic method of determination of the air-tightness of metal transistors׳ packagings

The paper presents a new method of determination of the air-tightness of metal packagings of transistors. This method is based on the thermoacoustic approach with a microphone detection. The thermoacoustic approach means that the periodical overpressure is generated by the periodical temperature of the transistor caused by the periodical electric power dissipation in it. In the paper both the experimental thermoacoustic frequency characteristics and theoretical approach applied for numerical interpretations of experimental data are presented and discussed. The paper presents the experimental thermoacoustic set-up used in experiments, mathematical models, procedures applied and experimental results obtained for TO-3, TO-39 and TO-18 packagings. General predictions of the thermoacoustic theory concerning the sensitivity of this method for different types of packagings are also presented and discussed.