Surface tension-based ultra-micro precision dispensing method for micro-scale manufacturing and its key influence factors analysis

Due to the rapid development of precision micro-manufacturing technology, the connection and assembly process of precision micro devices put forward higher requirements for the volume and accuracy of micro dispensing technology. In this paper, an ultra-micro dispensing method based on the surface tension is proposed. It can realize micro size feature adhesive dispensing, here, adhesive droplet volume is in range of fL-pL. The transferring needle passes through the thin tube filled with adhesive liquid, and correspondingly, a micro amount of adhesive liquid is attached to the needle depending on the adhesion between needle and liquid. Then, the adhesive force between adhesive liquid and dispensing surface and the liquid's self surface tension make a micro amount of adhesive liquid left on the dispensing surface and form a droplet. In this paper, we carried out a set of detailed single factor experimental study, and systematically analyzed the affection of main working parameters, including the diameter of transferring needle, dispensing speed, dispensing distance between the tip of needle and dispensing surface and the viscosity of adhesive, on dispensing results. Based on the above research results about working parameters characteristics, an ultra-micro dispensing process at fL level volume was realized. Diameter of adhesive droplet could be as small as 22.4 mu m, and volume reached to 228 fL. Ultra-micro automatic continuous dispensing is realized through automatic moving path planning of transferring needle by CAD program, and we obtained two droplet dot arrays with different layouts. The proposed ultra micro dispensing system can control droplet size and dispensing position precisely. The deviation of adhesive droplet diameter is less than 2.2 mu m, and the position deviation is within 1.58 mu m.