The effect of solder paste residues on RF signal integrity

Wireless devices such as pagers and cellular phones are becoming common con sumer items. These products require low loss RF signal propagation which is affected by material choices and processing conditions. This paper examine s the effect of a series of no-clean solder pastes on signal integrity usin g an RF test circuit which sends a broadband signal through a gallium arsen ide antenna switch and measures its transmission using a network analyzer. The test circuit also measures signal leakage. This paper reports on two di fferent test vehicles, one that uses a 900 MHz antenna switch, and the othe r that uses a 2.0 GHz antenna switch. The transmission and leakage readings were taken daily for 16-21 days while the test vehicles were under acceler ated aging conditions of 85 degrees C and 85% RH. Average values for the re adings for each solder paste were plotted to provide comparison among the p astes. The comparison data clearly distinguish solder pastes that provide c onsistency throughout the test period from those which do not.