Metal Capacitive Micro-pressure Sensor Diaphragm Welding Technology

The metal membrane based capacitive micro-pressure sensor shows high measurement accuracy, high sensitivity, and corrosion resistance, making it adaptable to extreme and harsh environments with diverse application scenarios. The design and manufacturing process of metal based capacitive micro-pressure sensors are complex, involving structural design, diaphragm welding, and circuit design, among which diaphragm welding is crucial for determining sensor’s performance. A new method of welding membrane with low welding stresses are proposed in this manuscript. According to the method, the 0.035 mm thick inconel 600 membrane are successfully welded to bulk inconel 600. The distance between the membrane and bulk inconel is 350 μm, with the based capacitance of 2.9 pF. The leakage rate of the welding reaches 7.5×10-12 Pa•m3/s. A high-precision testing system with a capacity of 10 Torr are built and the variation of capacitance with pressure after welding are characterized. The exprement result shows that when the pressure changes from 1 Torr to 10 Torr, the capacitance changes from 2.9 pF to 12.1 pF with repeatability reaching 0.02%. The FEM results of COMSOL match the experimental results very well, and this welding method can be applied to any low stress thin film welding engineering practice.