# Derating of Electrical Contacts with Varying Surface Roughness
## 4 Conclusions and Summary  
This study provides new scientific insights into the role of surface roughness in shaping the thermal and electrical performance of electrical contacts, particularly in the context of derating behavior. The results demonstrate that surface roughness is not merely a mechanical property but a critical factor influencing contact resistance, thermal conductivity, and overall current-carrying capability. The analysis of the impact of surface roughness on the derating parameters of electrical contacts revealed significant differences in the behavior of the tested samples. Surfaces with lower roughness (R\({}_{\mathrm{z}}\) = 2 \(\upmu\)m) exhibit higher contact quality, which translates into better current conduction. The larger actual contact area allows for more efficient heat dissipation, reducing the risk of overheating at higher current levels. On the other hand, surfaces with higher roughness (R\({}_{\mathrm{z}}\) = 10 \(\upmu\)m) show greater contact resistance, leading to higher heat losses and a faster temperature rise as the current load increases. Measurement data indicate a direct correlation between increased contact surface roughness and elevated temperature limitations. Higher current intensities lead to more pronounced thermal loading of the samples, thereby reducing the maximum permissible ambient temperature. The derating characteristics observed for contacts with a surface roughness of R\({}_{\mathrm{z}}\) = 10 \(\upmu\)m demonstrate a heightened sensitivity to ambient temperature variations, as evidenced by a more rapid decline in allowable current with increasing temperature compared to contacts with smoother surfaces. The thermal tests and contact resistance measurements showed that contacts with smooth surfaces (R\({}_{\mathrm{z}}\) = 2 \(\upmu\)m) are more effective in applications requiring stable operating parameters under high current loads. High roughness (R\({}_{\mathrm{z}}\) = 10 \(\upmu\)m) limits the thermal conductivity of the contacts, requiring the use of lower operating temperatures or reduced maximum current values to avoid overheating. Therefore, when designing systems using electrical contacts, surface roughness parameters must be considered as a key factor influencing their thermal characteristics. The analysis of the derating characteristics further reveals that the curve corresponding to R\({}_{\mathrm{z}}\) = 2 \(\upmu\)m is notably smoother compared to that of R\({}_{\mathrm{z}}\) = 10 \(\upmu\)m, which exhibits more abrupt temperature increases. The derating behavior for R\({}_{\mathrm{z}}\) = 2 \(\upmu\)m, associated with a smoother contact surface, indicates a more gradual temperature rise with increasing current. In contrast, the R\({}_{\mathrm{z}}\) = 10 \(\upmu\)m curve, representative of a rougher surface, displays pronounced temperature spikes under similar current conditions. This behavior suggests that contacts with lower surface roughness are better suited to sustain higher current loads with reduced thermal stress, whereas those with higher roughness require more stringent thermal management due to their elevated susceptibility to rapid overheating. The findings of this study underscore the critical role of surface quality in the performance of electrical contacts, particularly in applications demanding high reliability and