Electrically conductive adhesives filled with surface modified copper particles

The main hurdle for the wide use of Ag-filled isotropically conductive adhesives (ICAs) is the high cost of Ag fillers. Copper can be a promising candidate for conductive metallic filler due to its low cost, high electrical conductivity and improved electro-migration performance compared to Ag. But the oxidation of copper dramatically increases the resistivity of copper-filled ICAs which considerably limits their applications. Lactic acid, glycolic acid and glutaric acid can react with the copper oxides surrounding copper particles to form copper salts which then can be reduced to copper in the annealing process. In this paper, the copper particles were treated with a variety of organic acid in ethanol. The anti-oxidative copper particles were then mixed with epoxy and the corresponding acid to prepare the electrically conductive pastes which were deposited on glass slides and cured at proper temperatures. The bulk resistivity of the copper filled ICA with a filler loadings of 67 wt.% reached 1.2×10 ⁴ Ω·cm. The curing behavior was analyzed by DSC. The effects of the acids on the electrical resistivity and the microstructure of the samples were studied.