A novel connecting material: electrically conductive adhesives based on polyimide resin and conductive ceramic powders

In order to achieve the application of conductive adhesives under high temperatures, we prepared a novel type of conductive adhesives by using CaMnO₃ conductive ceramic powders as conductive fillers and polyimide as matrix resin. The resistivity of the prepared polyimide conductive adhesives is 0.25 KΩ m and the tensile strength is 0.85 MPa. After aging treatment, the stability and heat resistance of the polyimide conductive adhesives are excellent comparing to epoxy resin conductive adhesives. The electrical and mechanical properties of the epoxy resin were decreased rapidly after 24 h. However, there was a great stability on the mechanical and electrical properties of the polyimide conductive adhesives. Their performances were still well after 300 °C, but the performances of the epoxy resin conductive adhesives were obviously deteriorated after 150 °C. These prove that the prepared polyimide conductive adhesives can overcome the disadvantage of poor stability and poor heat-resistance property of the epoxy resin conductive adhesives, and will have broad application prospects as connecting materials in the aerospace field. After a series of exploration experiments, we determined the best recipe and the best curing process of the polyimide conductive adhesives: 40 wt% CaMnO₃ as conductive powders, 40 wt% styrene as thinners, 2 wt% 3-Amino-propyl-triethoxy-silane (KH550) as coupling agent, 2 wt% 2,4,6-trimethylbenzoyl-phosphine oxide as photoinitiator, 4 wt% benzoyl peroxide as thermal initiator, 1 wt% polyethylene glycol-400 as conductive promoting agent, curing temperature of 170 °C, curing time of 240 s.