Design of suction nozzle on a new SMT silicone rubber keypad

Abstract

Conductive silicone rubber keypads, possessed outstanding mechanical properties, are widely used in electrical products. However, the assembly of silicone rubber keypad on printed circuit board(PCB) is done by hand. We combined SMT Surface Mount Technology(SMT) with interference fit principle. In this paper, an automatic assembly technology for silicone rubber keypads was developed without solder and the corresponding suction nozzle was designed. The diameter of the pin is larger than that of the PCB hole, so that the pin and the PCB hole can produce interference fit. The working principle of this technology is that the designed SMT suction nozzle is used to suck the silicone rubber keypad, and then the silicone rubber keypad is moved to the directly above the PCB hole with the suction nozzle, and then the two positioning pins of the silicone rubber are pressed into the PCB holes by the two thimbles of the suction nozzle, so that the PCB hole and the silicone rubber keypad positioning pins produce interference fit. Secondly, three suction nozzles, surface suction type, integral suction type and thimble insertion type, are proposed by the different parts of the suction nozzles. The internal structure of each nozzle is designed into four types: cylindrical, circular table, rectangular and circular arc. The suitable and reliable nozzle is selected by fluid simulation and stress simulation. The simulated result shows that the structure proposed is feasible. The suction nozzle and silicone rubber keypads were manufactured for testing on the SMT machine. The test results show that this method is useful and it can be successfully automated.