High thermal conductive adhesive film for Cu and Al plate adhesion in power eectronics package

The high thermal conductive of 10 to 15 W/mK and high heat durable adhesive film has been developed. It is composite of the imide base high heat durable thermosetting resin and high thermal conductive particles. The 1% and 5% weight loss temperature were 384 and 494°C, respectively. Breakdown voltage of the 200 μm thick film was larger than 5 kV at 50 Hz. Insulation reliability was evaluated at 85°C and 85%Rh with applying 750 V and no resistance drop was detected for 1000 hours. The material was mainly designed for thermal interface adhesive of heat generator side lead flame Cu and heat sink Al in power electronics packaging field Coefficient of thermal expansions of Cu and Al were 17 and 23 ppm/°C, respectively. That valued of the adhesive was made up to 19 ppm/°C, which lay between them. The numerical stress analysis of the structure by finite element method was performed. It indicated that the modulus of the adhesive at low temperature affected the stress significantly. Cu (50 mm × 60 mm × 7.5 mm) and Al (70 mm × 80 mm × 6.0 mm) thick plates were adhered by the adhesive and 2000 times thermal cycle durability evaluation between -45 to 125°C were implemented. The sample adhered by the adhesive which was designed to be low modulus at low temperature had no delamination after the thermal cycle, which was investigated by scanning acoustic microscope.