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The paper discusses selected statistical methods enabling the effective assessment of the influence of selected factors on the efficiency of the assembly process of RF systems. The considerations were carried out on the example of the investigations into the influence of the size of the voids appearing in the soldering area of RF power transistors on the value of selected electrical parameters of these devices in a considered electronic module. Selected quality tools were described and additional analyses were performed using the Six Sigma methodology and the Minitab application. With the use of the QFD (Quality Function Deployment) method and the HoQ (House of Quality) tool, all the relevant output quantities of the tested system and its components were defined. The obtained results of statistical analyses allow determining the existing correlations between particular quantities, which include, among others, the temperature of the transistor case, the size of the void spaces in the soldering area or the location of transistors on the PCB (Printed Circuit Board). From the performed investigations, it is clear that no correlation between the void size and the thermal resistance of the tested transistors was observed.

The paper presents the results of investigations illustrating the influence of imperfections in the soldering process on thermal properties of transistors operating in RF (Radio Frequency) systems. The methods of measurements used to determine the junction and case temperature of the tested transistors and their thermal resistance are described. The results of the performed measurements are presented and discussed, and their statistical analysis is carried out. The correlation between thermal parameters of the tested transistors, parameters of the assembly process and the measurement conditions is investigated. Some calculation results illustrating an influence of device thermal resistance and dissipated power on changing its lifetime are shown and discussed. It is also shown that no correlation between the void sizes and the device thermal resistance and lifetime is observed. Possibilities of improving the assembly process are indicated, which allows extending the expected lifetime of the tested transistors.

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