Issue link: https://iconnect007.uberflip.com/i/1506834
SEPTEMBER 2023 I SMT007 MAGAZINE 67 CHIPS Act taxpayer money—$52 billion— into this to prime the pump (getting manufac- turers ready to supply electronic devices), but you must have something to pump (that is, an economically sustainable U.S.-based electron- ics ecosystem). Larger and "in-process" heterogeneous assemblies are increasingly fragile. ey're a lot more vibration and environmentally sensi- tive. It's a lot more problematic to move them around the world, say, shipping from a fab to an OSAT on the other side of the planet. is is why we see TSMC, Intel, and others (Samsung is already there) essentially moving into the OSAT space—and poten- tially into the EMS space as assembly for high end elec- tronics increasingly resembles a series of post-BEOL integra- tion processes. How do all these dynamics put pressure on solder to change? Solder usage is expanding and evolving into a whole series of different types of materials, not just alloys, but different formats like vari- ous shapes and ultrafine powder sizes for sol- der paste, and new technologies like mixed powder types. People have been talking about sintering as an alternative in some instances, but it will always be a "near net shape" material; there's no wetting or flow like you see with solder, which is what makes solder so durable and easy to apply. In many applications, such as very high-power die attach, large die (such as IGBT die), high current density type applica- tions, sintering really is a great way to move forward, though it's relatively slow and expen- sive. is is the basis of a power die, where the bottom of the die is attached to a substrate and large amounts of current then flow in the Z-axis through the die, and heat flows out. Regarding high temp solder (HTS), we're seeing that for some of these high-reliabil- ity applications, high-lead (Pb) is actually still being used as an allowance from ROHS. Let's say you have a diode that must survive SMT reflow; the die attach solder inside the package must not re-melt until it's over 265°C, so you use a known-good, high-reliability, high-lead solder. Sintering (usually Ag or Cu) or, prefer- ably, a Pb-free solder, is desirable to finally kick out one of the last bastions of allowed high- lead solder. Indium Corporation is enabling that capability in solder, so that's an example of a need for a high-tempera- ture solder. In medium-temperature solder (MTS), we're work- ing on environmental sus- tainability by reducing the energy costs of reflowing sol- der by moving to lower tem- p e r a tu r e s — f r o m S A C 3 0 5 reflow temperatures (maybe 260°C max) to those associ- ated with more 63Sn (220°C), but using Pb-free solders. With low temperature solders, there is also a move to reflow lower than 195°C, to protect some increasingly delicate devices and sub- assemblies. Reducing solder temperatures also has a benefit in reducing stress on large assemblies, so there are benefits other than simple power cost reduction. Summing up, the pressure is on U.S.-based OSATs and EMS suppliers to reduce costs through automation, enable and optimize low temperature assembly, build and operate cleanrooms, and adopt fine pitch heteroge- neous integration. Most EMS companies are already accustomed to supply chain issues so that won't be anathema to them. Andy, thank you for this insightful conversation. I appreciate the opportunity to talk. anks Nolan. SMT007 Summing up, the pressure is on U.S.-based OSATs and EMS suppliers.