Thermal degradation and decomposition of FR4 laminate PCB substrates joined by Friction Riveting

Glass fiber-reinforced epoxy laminates (FR4), widely used in printed circuit board (PCB) fabrication, face challenges in joining processes due to their susceptibility to thermal degradation. Friction Riveting, a promising technique for joining FR4 substrates, offers advantages over traditional methods, but might induce thermal damage at elevated temperatures. This study investigates the thermal degradation mechanisms of FR4 laminates joined by Friction Riveting, focusing on the influence of process parameters and copper layer configuration. Microscopic cross-sectional analysis, differential scanning calorimetry (DSC), thermogravimetric analysis, Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDX) were employed to assess thermal degradation under different joining conditions. The results revealed that higher process temperatures led to increased rivet deformation and charring of FR4, especially in laminates with double copper layers. The presence of copper layers influenced the decomposition behavior, exhibiting a complex interaction between enhanced thermal stability and accelerated degradation due to increased thermal conductivity and friction. These findings highlight the importance of optimizing process parameters to mitigate thermal damage and ensure the reliability of friction-riveted FR4 joints in PCB assemblies.