## 3 Description of the Analysis  
Using the statistical methods described in the previous section, the analysis of the properties of an electronic module were performed. At first, the P-diagram of the analyzed module was formulated. It is shown in Figure 2.  
In the case of the system for measuring the effect of voids in the soldering area of transistors, the input and control parameters, interferences and output signals are defined as follows:  
Figure 2: P-diagram with inputs, control and noise parameters’ influence on the output data of the tested transistors in PCB. input signals: the drain current \(\rm I_{D}\) [A] and dissipated power P [W];
* controllable input parameters: the gate-source voltage \(\rm V_{GS}\) [V] and the voltage between the drain and the source \(\rm V_{DS}\) [V];
* uncontrollable input parameters(in this case, these are additional parameters affecting the measurement results, which were not controllable, but were measured in order to relate to the values of the output signals): the ambient temperature \(\rm T_{a}\) [\({}^{\circ}\)C], the total void area in the soldering area of power devices expressed in %, the total individual void size also expressed in %, the type of the transistor being measured (BLC9G22 LS-160 VT or BLC10G22 LS -240 PVT) and the position of the transistor on the PCB; two pairs of transistors (Figure 1) are mounted in the tested system;
* output parameters: the temperature \(\rm T_{C}\) measured on the case of the transistors (the average temperature along the transistor cross-section), the area temperature [\({}^{\circ}\)C] and the thermal resistance \(\rm R_{th}\) expressed in K/W. In the case under consideration, the QFD is used to determine the type of analyses that should be performed to determine the level of influence of selected factors on certain parameters of the discussed electronic module (shown in next section). As it was only important to identify which technical factors have the greatest impact on meeting the customer requirements, the QFD analysis was limited to the five most important phases. The customer's requirements related to the operation of the electronic module include:  
* Reliability of the electronic system operation;
* Lifetime of transistors;
* Output power;
* Thermal resistance \(\rm R_{th}\). The customer requirements described in this way were assigned the following priorities on a 10-point scale:  
1--very little importance;  
4--little importance;  
7--quite important;  
10--very important. The differentiation of the scale according to the above nomenclature made it possible to define the matrix of points between the customer's requirements and the parameters of the factors assigned to them, which may have had an impact on the described requirements. The following parameters were taken into account:  
* the total area of the voids in the soldering area expressed as the sum of the individual (Voids total) measured with the X-ray DAGE system XD7600 NT;
* the greatest individual voids measured with the same X-ray system, as in the case of the measurement of the area of total voids;
* the temperatures measured on the component case using the Optris IR camera with the Optris PI connect software [34] thermographic camera in the chamber [1] for a selected operating point;
* temperatures measured on the component's case at selected points of its cross-section;
* the ambient temperature;
* the transistor type;
* the position of the transistor on the PCB;  
* positions TR_A1, TR_A3 are for the transistor BLC10G22 LS-240 PVT;
* positions TR_B2, TR_B4 are for the transistor BLC9G22 LS-160 VT;
* the soldering profile;
* the types of the solders used;
* the type of SMT oven used (conventional, or the one using nitrogen as an environmental factor). Not all of the above-mentioned parameters may affect the fulfillment of the requirements [4], although these seem to be the most important [35; 36; 37].