Andy C Mackie, PhD, Product Manager, Semiconductor Packaging Materials, Indium Corporation

In ball-attach fluxes, we are seeing increasing demand for no-clean materials, driven by the twin needs of process cost reduction and elimination of capital (cleaning) equipment costs. The customers of the primary OSAT (outsourced assembly and test) companies are beginning to accept that residues may be acceptable, if they can meet certain performance and appearance criteria.

In direct chip-attach (DCA), the problem of cleaning under flip-chips with clearances less than 100microns will be eliminated by moving to either a no-flow underfill material, or to a low residue no-clean flux. While the first of these may seem tempting, there are still serious concerns about the use of unfilled materials in DCA. The winner will almost certainly be a low-residue no-clean spray flux that exhibits excellent compatibility with capillary underfills, combined with high solderability; we are working with several manufacturers on this technology.

Jordan Ross, Marketing Manager, Thermal Interface Materials, Indium Corporation

The most surprising need for 2008 that will keep extending for the forseeable future is the need for halide-free fluxes, even for water-wash.

Ultra-fine solder pastes will disappear, having reached a natural limit at about 100microns pitch, and be replaced by ultrafine “microspheres”: solder spheres from 50 to 300microns in diameter.

PoP applications are the tip of an incredible iceberg. 3D packaging will drive us into new materials needs, probably with interesting variations on old technologies.

Even though it has been predicted for years, reality is now striking many processor packaging houses that the combination of “smaller” and “faster” for processors also includes necessarily means “hotter”. There is an incredible demand now for heat removal from overclocked CPU’s and GPU’s, which will require thermal interface materials with significantly improved heat-flux capability, and also heat-tolerance, over the standard greases and metal-filled epoxies.

In die-attach, the search for a low-cost lead-free alloy with a solidus over 265degC will continue, although metal-filled polymer materials may . Good luck to all of us on the quest for this material.