Self-induced instability of passive intermodulation in microwave laminates

The experimental results presented above provide the strong evidence of the significant instability of the PIM performance of commercial PCB laminates. The observed phenomenon is attributed to the viscoelastic stress relaxation in the processed boards. Although the presented data show improvement of the PIM performance with time, the associated physical mechanisms indicate the necessity of tighter manufacturing control over the electromagnetic properties of the high-performance laminate materials.