Circuits Assembly - February 2008 - (Page 24)

Recent Patents Embedded Active Components for High-Reliability Products By Jim D. Raby The missile’s shock and vibration mandated a new technology: a wire-bonded, solderless PCB. I never planned to be in the assembly and manufacturing business. I was satisfied with my life in government, working with high reliability hardware, including various weapons systems and the Saturn Apollo program – the beginning of my industry experience. That is where I learned the most about the effects of vibration and shock on components and PCBs. But time has a way of changing one’s direction. One day, a friend who worked for the U.S. Navy called and asked for my help on a failing circuit board. I visited the supplier, provided a short-term solution, and then gave the Navy a plan for a long-term solution. They jumped on it quickly. The problem was, the Navy supplier was mounting a heavy module on the board surface. When fired in the missile, the module leads would break loose and fail. Several companies have successfully buried passive die and components in boards, but many attempts to do the same with active die had failed. Nevertheless, I concluded that was the solution to the Navy’s problem. I planted the seed with some bright, young engineers who did not know it “wasn’t possible.” Here’s what we developed. We built wire bonds from chip to board, forming a shorter Figure 1. Imbedded component/die technology circuit card assembly. circuit path, hence fewer parasitic influences. (Store the bare die in a nitrogen environment within a clean room.) The process does not use solder; therefore, tin whisker problems have been eliminated. After assembly is completed, so-called step cavities are filled with suppression materials and then covered with a copper lid on each side. The unit is now a solid block of electronics. There are flex tail inputs and outputs that permit connections to adjacent systems. A central cooling core in the board dissipates heat from components – more so than had been previously capable. For denser packaging, die can be stacked within the cavities. A major problem was finding a board shop and tooling to build the boards, as the step cavities are not simple to build. The result: complex hardware in about onethird the previous printed circuit board area. In October 2006, after sufficient testing to satisfy the harshest skeptics, we were issued US patent 7,116,557. Assemblies built using the novel process have withstood long temperature and humidity testing, and we know it to be solid manufacturing technology. It is less expensive 24 Circuits Assembly FEBRUARY 2008 circuitsassembly.com http://circuitsassembly.com

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Circuits Assembly - February 2008 Contents Caveat Lector Letters Industry News Market Watch Global Sourcing Better Manufacturing Maximizing Lean Copper As a Viable Solution for IC Packaging Embedded Active Components for High-Rel Products Cover Story: XRF Equipment As a RoHS Screening Tool Tech Tips Selective Soldering Test and Inspection Process Doctor Pb-Free Lessons Learned Product Spotlight Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - February 2008

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