## 4 Discussion  
### Analysis of the Influence of Temperature and Humidity on SIR  
When ionic contaminates occur on the surface of the product, hydrophilic ionic contamination absorbs water in the humid environment and the solution changes from a crystalline solution to a saturated solution, (deliquescence) [31; 32]. When the relative humidity reaches the critical relative humidity (CRH) of the contaminated salt, deliquescence of the contaminated salt occurs. NaCl is not only hydrophilic but also a strong electrolyte. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**TEST** & **Test Project** & **Test Condition** & **Voltage (kV)** \\ \hline TEST-1 & Humidity (steady State) & MIL-STD-202 103-A & 4, 7, and 10 \\ TEST-2 & Moisture Resistance & MIL-STD-202 106 & 4, 7, and 10 \\ TEST-3 & Thermal shock & MIL-STD-202 107-B-1 & 4, 7, and 10 \\ TEST-4 & Alternating hot and humid & 2.4.2 & 4, 7, and 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Test condition. Figure 17: Potting sample. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & \
\begin{tabular}{c} **Minimum Deviation from** \\ **the Sampling Value** \\ \end{tabular} &
\begin{tabular}{c} **Maximum Deviation of the** \\ **Sampling Value** \\ \end{tabular} \\ \hline encapsulated samples & 0 & 0 \\ unencapsulated samples & 0.03 1  & 0.44 \\ (non-contamination) & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of sampling values for encapsulated and unencapsulated samples. Figure 18: Sampling values after potting validation test. According to [PERSON]'s law [20], it is completely dissociated into Na\({}^{+}\) and Cl\({}^{-}\) in water. In the absence of an electric field, ions diffuse along the surface of the PCB. After a long enough diffusion time (several hours), the ions will be uniformly distributed on the surface of the PCB, resulting in a small and essentially isotropic surface impedance. However, under the action of an applied electric field, ions change from random diffusion motion to movement in the direction of the power line, which is called ion migration, as shown in Figure 19. After ion migration, the positive ions gradually accumulate at the negative extreme of the electric field and the negative ions gradually accumulate at the positive extreme of the electric field. Humidity and temperature are the main factors affecting ion migration. The results show that the sampling values of all products did not change below 70% RH, and the change occurred at RH \(\geq\) 75% RH. With an increase in temperature, the relative humidity point where the change occurred did not decrease significantly. This is because the CRH of NaCl at 20\(\sim\)40 \({}^{\circ}\)C is 75% RH. In addition, as the ionic bond breakage does not generate heat during the dissolution of sodium chloride, solubility does not increase with the increase in temperature, which means that the increase in temperature has little influence on the relative humidity of NaCl. The influence of temperature on SIR is reflected in the degree of deterioration. Under the same relative humidity conditions, the more severe deterioration occurs as the temperature increases, which is reflected in the product, and the greater the deviation of the telemetry parameters from the normal value. Temperature and humidity have a synergistic effect on SIR. Humidity is the main factor, providing the necessary moisture for the formation of the electrolyte. The influence of temperature on electronic products has two factors. On the one hand, the increase in temperature increases the content of water vapor in the air. On the other hand, the increase in temperature reduces the viscosity of the saturated solution and accelerates ion mobility [33]. In general, the variation of insulation performance of HV-PCB under temperature and humidity stress has similar and different effects on low-voltage PCBs.