Low Temperature Eutectic Alloy Bonding Used in MEMS-Based Solid Propellant Microthrusters Array

Abstract

Considering the safety of the charge filled in the chambers and the operational reliability, a low temperature eutectic alloy bonding was preferred for the final assembling process of MEMS-based solid propellant microthrusters (SPM) array with top-side igniters. The optimum conditions of the alloy coating are the pH value of the solution is 0.5, the base metal layer is composed of Ti (60nm)/Cu (500nm) deposited by magnetron sputtering. The bonding process was conducted in an oven with air and the bonding temperature is 70°C. To predict the performance of bonding layer, the temperature distributions of eutectic alloy layer were simulated by ANSYS software when the chamber is full of high temperature reactants. The simulation results demonstrated the bonding strength wouldn’t cut down since the heat transfer induced by the combustion of charge. The assembled MEMS-SPM array was tested under constant voltage, the results indicated that the eutectic solder bonding procedure meet the requirements of the MEMS-SPM assembling.

Recent Advances in MEMS-Based Microthrusters

“…Generally, adhesive bonding was adopted for the assembling process due to contamination of the surface after filling propellant. Ru et al [40] developed a vertical structure SPM that adopted a bonding technique of low-temperature eutectic alloy for the assembling of the SPM array by considering the safety of the charge filled in the chambers and the operational reliability. The SPM structure with top-side igniter is shown in Figure 10.…”

“…With the developing of the MEMS, various bonding technologies have been researched to meet some special requirements of different products in MEMS field [38]. The main bonding technologies include silicon-to-silicon fusion bonding, anodic bonding, room temperature silicon-to-silicon bonding [39], adhesive bonding, solder bonding, and eutectic bonding [40]. Generally, adhesive bonding was adopted for the assembling process due to contamination of the surface after filling propellant.…”