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|Low Temperature Sintering Silver Paste Using MO Technology|
|Keywords: sintering silver, high thermal conductivity, LED and power devices|
|Traditional thick film technology is widely used in various electronics products. There are two type of paste based on thick film technology. Typically, over 400C is required for high temperature sintering type which contains glass for adhesion function. It shows high electrical and thermal performance. On the other hand, 150-300C range process is used for low temperature process type such as silver epoxy. In last decade, nano silver technology shows amazing progress to address low temperature operation by low temperature sintering. This paper will discuss the results on fundamental study of newly developed nano silver pastes with unique approach which uses MO (Metallo-organic) technology and resin reinforcing technology. Nano silver pastes contain several types of dispersant as surface coating to prevent agglomeration of the particles. Various coating technique has been reported to optimize sintering performance and stability. MO technology provides low temperature sintering capability by minimizing the coating material. The nano silver pastes show high electrical and thermal performance. However, degradation of die shear strength has been found by thermal cycling test due to the fragility of porous sintered structure. To improve the mechanical property, resin reinforcing technology has been developed. By adding special resin to the pastes, the porous area is filled with the resin and the sintered structure is reinforced. Degradation of die shear strength was not found by thermal cycling test to 1000 cycles. This paste is formulated with a low viscosity for easy dispensing and easy processing using standard conventional hot air curing systems. By curing the paste at 200C for one hour, it shows high thermal conductivity of 180 W/mK and very low electrical resistivity of 3 ohm-cm. Furthermore, it shows strong adhesion to metalized die and substrates and the metal-to-metal bonding was highly reliable for thermal cycling. Nano silver pastes using MO technology and resin reinforcing technology will meet lots of requirement on various thick film applications.|
|Ken Araujo, Area Manager