## 3 Description of the Analysis
In this study, in order to perform the QFD analysis, parameters that could affect these requirements were assigned to the customer's requirements and the above-described score was set for them (Figure 3). The values of the points were assigned based on the best knowledge in the field of the influence of temperature changes on the thermal parameters of the tested transistors [27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37]. There is a possibility of making a mistake at this stage. It may be discovered that the score is not fully accurate and that the less important parameters are ranked higher than the more important ones. Such an error is not significant as long as the statistical analyses performed at later stages do not show other relations between the analyzed values than those resulting from the assigned scores. However, more attention should be paid to the fact that none of the parameters for the analysis should be omitted, as this may result in an incomplete picture, and a complete picture of the results is necessary to describe those results. The results in the HoQ (Figure 3), in the \"importance rating\" column, indicate which influence of the factor on the customer's requirement set, according to priority, is the most important. According to the colors used here, the areas were compared with each other and, in the importance rating, the most important ones were marked in red and orange (Figure 3). The results indicating the weak influence of the factors on the specified requirements are marked in dark or light green, depending on the value. Thus, out of the 10 previously defined factors, the six with the highest value exceeding 150 were as follows [38]:  
* the temperature measured at the cross-section points of the transistor case (rating 229);
* the transistor type (rating 187);
* the average temperature measured at the component case (rating 178);
* the ambient temperature (rating 178);
* the total voids (rating 175);
* the individual voids (rating 154). The above-described parameters are marked in yellow in the matrix. From the results of the HoQ matrix obtained in this way, it can be concluded that the most important dependences that should be verified are:  
* the dependence of changes in thermal resistance Rth on the temperature measured along the cross-section of the component (Rth measurements for several selected points in the cross-section of the transistor case);  
Figure 3: QFD analysis using the House of Quality data matrix to determine the most important factors influencing the customer’s requirements. * the temperatures measured along the cross-section of the transistor and other parameters, which are defined as follows:
* T\({}_{\rm{emp1}}\)--the highest temperature measured on the case;
* T\({}_{\rm{empmin}}\)--the lowest temperature on the case;
* T\({}_{\rm{emp2}}\)--the temperature measured at the opposite end of the transistor case to the transistor feed point;
* T\({}_{\rm{emp\
ot=}}\)--the mean temperature of the transistor case area;
* The temperature difference T\({}_{\rm{emp1}}\) and T\({}_{\rm{emp2}}\);
* R\({}_{\rm{thT1}}\), R\({}_{\rm{thmin}}\), R\({}_{\rm{thT2}}\)--the determined thermal resistances at the characteristic points of the transistor case cross-section at the temperature values T\({}_{\rm{emp1}}\), T\({}_{\rm{empmin}}\) and T\({}_{\rm{emp2}}\);
* R\({}_{\rm{thaverage}}\)--the average value of thermal resistance determined as the arithmetic mean of values R\({}_{\rm{th\,T1}}\), R\({}_{\rm{th\,T2}}\) and R\({}_{\rm{th\,min}}\);
* T\({}_{\rm{a}}\)--the ambient temperature measured with the described Optris system [1];
* P--the power dissipated on the transistor determined from the set values of drain current I\({}_{\rm{D}}\) and voltage V\({}_{\rm{DS}}\).