Tsuyoshi Sato

A novel wafer dicing method using metal-assisted chemical etching

A novel wafer dicing method that can singulate silicon wafers into individual dies at once has been developed. Since this method relies on chemical reactions, we call it Chemical Dicing. Chemical Dicing has the advantages of high throughput, narrow dicing line width, and high chip strength compared to conventional blade dicing methods. Chemical Dicing is based on the catalytic wet etching technique called metal-assisted chemical etching (MacEtch). However, the appropriate conditions required to form deep vertical trenches for Chemical Dicing with MacEtch remain controversial. In this paper, the MacEtch mechanisms and appropriate conditions for Chemical Dicing have been verified. The results show that the shape of the trenches can be controlled by a catalyst and a etchant composition, and Chemical Dicing can create vertical trenches with a depth greater than 150 μm and width less than 8 μm. The results are expected to contribute to the development of future dicing techniques.

Study on temperature dependence of viscosity of halogen-free dispensing solder paste

A dispensing process has been used to apply solder paste in surface mount technology (SMT) production. To stabilize the dispensing process, it is necessary to understand the influence of storage conditions on the viscosity of solder paste as one of various factors. In this paper, halogen-free dispensing solder paste is treated at a constant temperature and the variation of its viscosity is examined using a cone-plate-type viscometer, which can measure the viscosity of even a small amount of solder paste. Also, the tin salt is extracted from the solder paste after thermal treatment and the amount of tin in the tin salt is measured, from which the mechanism of increasing viscosity is discussed. In addition, the activation energy for increasing the viscosity of the halogen-free dispensing solder paste is calculated from an Arrhenius equation, and a predictive formula for the viscosity of solder paste is derived. Using this formula, it is possible to prevent dispensing failures by optimizing the storage conditions of halogen-free dispensing solder paste.