Snap-Curing Electrically Conductive Formulation for Solder Replacement Applications

Abstract

Pb-free soldering and the use of electrically conducive adhesives in the electronics industry are a segment of the global trend towards a lead-free environment. In comparison to lead-free solders, current commercial isotropic conductive adhesives are characterized by lower conductivity and need much more time for curing. Usually, a few minutes at 150°C are enough only for precuring. In this paper we describe the developed family of formulations with a curing time of several seconds at 150°C. There are single-component formulations, solvent-free type, prepared in a special way on the base of the common, accessible resins. They have very convenient handling properties; e.g., no drying on open screen during printing process. Viscosity depends on the resin and may be intentionally changed. Shelf life for all these formulations is about 12months at room temperature in closed containers. Refrigeration is not necessary. Unfortunately, the material needs the highest quality and purity of electronic grade silver fillers. The total permitted level of impurities is estimated as less than 10ppm. However, this is, rather, an advantage of the silver-filled adhesives.

Characterization of SnAgCu and SnPb solder joints on low‐temperature co‐fired ceramic substrate

“…Solder joints can provide mechanical and electrical connections and enhance heat spreading efficiency, and therefore are widely used in microelectronic packaging (Yang et al , 2004a). However, lead contained in tin‐lead solders is harmful to the environment (Moscicki et al , 2005).…”

Isotropic conductive adhesives in electronics

“…as conformal interconnect for a 3D IC stack (Robinson et al, 2008). one disadvantage of iCAs is that the polymer cure time is inherently longer than solder reflow times, but it can be shortened by 'snap-cure' polymers (Moscicki et al, 2005) which use fast catalysts, and fast variable frequency microwave curing (Wang et al, 2001;Fu et al, 2003). Much of the research focus in the literature is on reliability failure modes, e.g.…”