Keeping electronics cool has become a increasing problem with the advent of high density interconnects. Back in the days of 0.012-inch lines and spaces on 2-ounce copper signal layers, it was easy to keep designs cool. There was always lots of copper. As density increased however, line widths have gotten smaller, spacing is tighter and the cross-sectional copper area has been reduced exponentially. The net result is that cooling has now become a big problem for system designers.

The use of thermal simulation software helps engineers and designers create a system that maximizes heat dissipation within the confines of the construction materials, product performance requirements, the resulting circuit and component densities, power requirements and overall system size and weight factors. Adding thermal simulation early in the design equation will only become more critical as electronics systems increase in functional density. The International Technology Roadmap for Semiconductors has forecast that logic ICs will drop from 25 nm to 6 nm by 2013. At the same time, functional densities will increase from 1.11 billion transistors to 4.42 billion. As performance increases, so does heat throughout the system.

As Robin Bornoff of Mentor Graphics points out in our cover article, “Fluid Dynamic Simulation for Cool Designs,” the thermal resistivity of FR-4 contributes to thermal dissipation problems. While the epoxy and glass matrix of FR-4 makes for an excellent electrical insulator, these materials are very poor thermal insulators. Heat generated in the copper circuits spreads through FR-4, which traps it in and around the heat flow path, making it more difficult to dissipate from the source.

New heatsink materials promise to help keep next-generation electronics cool. Scientists at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research (IFAM) recently announced a new material that combines copper and diamond powder. Diamonds conduct heat five times better than copper. Copper and diamonds together produce a material that has better heat dissipation characteristics and a closer CTE match to ceramic materials.

But the real answer to beating the heat is not likely to come from a material's improvement, but from a new way of transferring information. The Department of Energy and Stanford University have demonstrated that bismuth telluride can be used as a topological insulator. According to the researchers, this new material functions at room temperature and allows electrons to travel on its surface without any loss of energy. The problem of heat generation in electronics is more troublesome than merely thermal dissipation considerations. Up to 40 percent of the power in a circuit is lost due to heat leakage. This makes it increasingly difficult to miniaturize without increasing heat. Enter spintronics.

Spintronics uses the intrinsic spin of electrons to transport and store information. Unlike the voltage-based system used in today’s electronics, spintronics uses topological insulators to carry electrons. Topological insulators offer no resistance and therefore no heat is generated in the process. Unlike previously studied superconducting materials, bismuth telluride has demonstrated the ability to act as a topological insulator at room temperature.

The lack of resistance associated with topological insulators will result in lower energy requirements in part due to the elimination of heat generation. This is likely to lead to increased computing speeds. The system is, however, limited to low power applications, and will be particularly useful in memory applications.

The cooling effects of spintronics and topological insulators like bismuth telluride still have a long way to go before they become a mainstream solution. In the meantime, proactive engineering design and the use of advanced materials to improve heat dissipation are going to become increasingly important.

These challenges cut across the supply chain, from the systems engineer; to IC, package and PCB designers; and on to the PCB fabricator and assembler. If the industry is going to adequately address the problem of hot computers, sizzling cell phones and a host of other overheated high-performance, small form-factor devices, communication and cooperation need to improve. Working together, supply-chain members will be able to meet the short-term demands for cooler electronics as we wait for advancements that will bring a cooler spin on things.