Die-attaching silver paste based on a novel solvent for high-power semiconductor devices

A new solvent composed of 4-(tert-butyl) cyclohexyl acetate as a dilute agent and HPMDA as a thickener was developed to make micron-sized Ag paste and to bond power semiconductors. The new Ag paste achieved sentinel printing to form sharp Ag patterns with uniform thickness and defined boundaries, which is a key to printing fine pitches in the electronics industry. The electrical resistivity of Ag patterns of 3 μΩ cm was obtained at 280 °C for 30 min. Two Ag-plating copper substrates were successfully bonded with the new Ag paste and the shear strength gradually increased with the bonding temperature. A high strength of 80 MPa was achieved at 280 °C under a small sintering pressure of 0.4 MPa. This value is far higher than the value obtained by using an expensive Ag nanoparticle paste. The detailed mechanism is discussed in this work by comparison with common ethylene glycol solvent.