Environmentally Friendly Conductive Adhesive Copper Powder

For the copper-filled isotropic conductive adhesives formulation, we used bisphenol-A type epoxy resin, imidazole as curing agent for the system and incorporating formaldehyde as reducing agent, along with dibutyl phthalate and silane couple agent, and adding Cu powders of 45μm diameter as conductive fillers. Optimal properties of Cu-filled ICAs were achieved by the L9(34) orthogonal experiments. In addition, the factors and their effects on the properties of conductive and mechanics were studied through adding different kinds of silane couple agent, weight percents of Cu, curing time and curing temperature, respectively.The optimal ratio between epoxy rein and imidazole was achieved by FTIR. The contents of oxygen on the surface of Cu powders before treated and after were determined by X-ray spectrometer. And the surface of the samples before and after coating silane couple agent were observed by SEM. In addition, X-ray diffractometer and thermo gravimetric analysis were applied to analyze the anti-oxidant property of Cu before they were coated silane couple agent and after. The bulk resistivity, shearing strength and aging performence were characterized by digital multimeter, stretcher and oven,respectively. The experiment results can be summarized.(1)The Cu-filled ICAs with their bulk resisvivity and shearing strength were 1.5×10-3/Ω·cm and 5.52 Mpa respectively when the ratio between epoxy rein and imidazole was 100:8, the percent of titanate couple agent was 1% and formaldehyde was 6%, and adding Cu up to 65 wt.%. After aging for 6 months under natural conditions, the bulk resisvivity can remain at 3.3×10-3/Ω·cm. In addition, the samples had good conductive property even exposed at 180 degrees. However, their properties under 50℃85%RH were poor.(2)The percolation threshold of ICAs is 65 wt.%. The conductivity of the samples increases with the percents of Cu and shearing strength decreases on the contrary. And the main factors which effected on the properties of Cu-filled ICAs were different.(3)The experiment showed that the optimal cuing process was 120℃for 3 h.(4)The result of SEM showed that silane couple agent may has a protective effect against some reunion, however, the protection of silane couple agent is not effective.(5)The results of XRD and TG showed that the anti-oxidant property of Cu after coated silane couple agent was really better than the untreated due to the polymer of silane couple agent had high thermal stability even exposed under hing temprature.