Effects of interface conditions and long-term stability of passive intermodulation response in printed lines

Abstract

An experimental investigation of the effect of conductor-to-substrate interface on distributed passive intermodulation (PIM) generation in printed microstrip lines has been undertaken using the custom-designed microwave laminates with removed surface bonding layers and with the commercial adhesion promotion applied to the conductor underside. The study of long-term stability of PIM performance of the printed circuits is reported for the first time. The comprehensive measurement results, observations of the selfimprovement of the PIM performance and the effect of panel bending on PIM generation in printed boards with different finishing are presented. A consistent physical interpretation of the observed phenomena is proposed. The results of this study provide new important considerations for the design and characterisation of low-PIM printed circuits.

Experimental Studies of Passive Intermodulation in Metal-to-Metal Contacts

“…This suspended microstrip line is made on Taconic TLX dielectric (Dk = 2.55 and Df = 0.0012 at 1.9 GHz) with a height of 0.8 mm. According to [9,10], its use allows to reduce the influence of PIM sources from dielectric itself, such as PIM issues resulting from the copper cladding technics. Therefore, PIM sources from metal-metal contact are not disturbed by other PIM issues.…”