Frequency Dependence of Impedance of Adhesive Joints

Electrically conductive adhesives have, in comparison with solders, significantly higher non-homogeneity of the structure, and therefore stability of electrical as well as mechanical properties of adhesive joints is lower than soldered ones. The impedance of the joints has been measured in wide frequency range (20 Hz to 1 MHz and 300 MHz to 3GHz). Measurements have been carried out by two methods: impedance in the range 20 Hz to 1MHz has been measured by LCR meter HP 4284A. A special test board for assembly of 1 jumper (of the type 1206) by electrically conductive adhesive has been fabricated for this measurement. The measurements at the frequencies 300 MHz and higher have been carried out using a shielded high-Q triplate line. Specimens have been prepared on Teflon boards, a scalar analyzer Rohde Scwartz ESPI has been used for evaluation. Very low changes of impedances of the joints have been found in the range of 20 Hz to 1 MHz. Typical courses of real and imaginary components of joints impedances in the frequency range 300 MHz to 3 GHz are as follows: the real components have grown in consequence of a skin-effect and have dominated. The imaginary components have been very low. The task for the future research is to explain decrease of the resistance of the joints with growing frequency for two types of adhesives