Authors: E.M. Meyer, A. Arp, F. Calderone, J. Kolbe, W. Meyer, H. Schaefer, and M. Stuve
Affilation: Metalor Technologies SA, Switzerland
Pages: 441 - 444
Keywords: ink-jet, adhesive, conductive adhesive, microelectronics, microsystems, nano-filled
The present work demonstrates feasibility of an inkjettable, isotropically electrically conductive adhesive in the form of a silver loaded resin with a 2-step curing mechanism. In the first step, the adhesive is dispensed (jetted) and precured leaving a “dry” surface. The second step consists of assembly and final curing. The 2-step cure system is based on a Acrylate-Epoxy-Resin matrix with very low viscosity, i.e., 3 mPas of newtonian properties. Spheroidal silver particles of high purity and a compatible organic coating have been loaded at 70% by weight. As the metallic silver particles are not transparent to UV, special attention had to be paid to include various UV initiators. The present adhesive allows curing of layers up to 30 mm thickness. (To our knowledge, there are no commercially available conductive adhesives based on radical UV curing.) Inkjet dispensing was performed using an innovative design based on a glass capillary nozzle with a final opening of 30 mm, surrounded by a piezo-actuator. Droplet sizes of 30 – 100 mm have been achieved, depending on adhesive parameters and nozzle size. This joint development of resin system, silver particles and inkjet device has opened the door to apply the technology for electrically conductive joining in the microsystem and microelectronic fields.