Electro-conductive adhesives for high density package and flip-chip interconnections

Dispensable isotropic conductive adhesives (ICA) and snap-curing anisotropi c conductive adhesives (ACA) are developed through the EC funded Brite EuRa m project DPICTEL #BE95-1503. They show very promising capabilities for hig h-density applications when compared to benchmark electro-conductive adhesi ves. As first high-density application, assemblies of ceramic and plastic ball g rid array/land grid array (LGA) on FR4 with DAC3-102/14 ICA are realized. M ixed assemblies solder/ICA show poor results, especially during aging. Full polymer LGA assemblies are built successfully. Daisy chains with hundreds of transitions component/substrate present resistances as low as 4 Omega. A fter comparison with benchmark products, CLGAs show themselves to be partic ularly reliable under moisture conditioning. Secondly, Aip-chip assemblies on board, of medium sized chips bumped with e lectroless NiAu and using DAC2-143/02 ACA, are performed. Contact resistanc es as low as 10 m Omega are produced. For this application, reliability res ults are succinct. Finally, flip-chip assemblies on glass of slim chips with NiAu bump pitch d own to 80 mu m, by means of the newly developed DAC2-143/02 ACA, are demons trated. The material shows better performances than a benchmark anisotropic conductive film, where measurements reveal contact resistances lower than the sheet resistance of the transparent indium tin oxide metallization used in display applications. Thermal cycling and temperature storage reveal go od behavior of the ACA paste. (C) 2000 Elsevier Science Ltd. All rights res erved.