Latest PCB Cooling Technology (3)

With thermal simulation, design engineers can predict the thermal performance of initial and subsequent designs without building and testing prototypes. Design variables such as the number of heatsinks, the thickness of the heatsink, the thickness of the heatsink base, and the thermal resistance of the heatsink interface material should be considered.

A correct thermal model is important for future 3D ICs planning to use logic and memory devices composed of thin dies, which significantly reduce lateral heat spread. Higher temperature spots will become more common as die thickness shrinks. Hot spots on the logic die can cause localized temperature rises in the memory die, which can reduce DRAM data retention time.

Researchers at the Belgian Inter-University Microelectronics Centre (IMEC) have validated the correct thermal model for the design of next-generation 3D hybrid stacked ICs. Much like future commercial chips, these 3D stacked chips consist of IMEC’s ​​proprietary logic CMOS ICs stacked on top of commercial DRAM. Stacking is achieved using through-silicon vias (TSVs) and micro-bumps. The research work is a collaboration between IMEC and partners Fujitsu, Globalfoundries, Intel, Micron, Panasonic, Qualcomm, Samsung, Sony and TSMC.

IBM plans to use microchannel water-cooling technology in future 3D IC processors, such as the Power8 processor to be launched in 2013. Energy-efficient hot water cooling technology is part of IBM’s zero-emission data center concept, said Bruno Michel, manager of the Advanced Thermal Packaging Division at IBM’s Zurich Research Center in Switzerland. To cool 3D stacked chips that generate more heat than a single processor in nearly the same space, using water instead of air reduces energy consumption.

The liquid-cooled CPU is also used in the XLR8 GTX 580 GeForce graphics card from PNY Technologies, which is primarily used in challenging graphics-intensive gaming products. PNY has also teamed up with CPU thermal management specialist Asetek to produce a product for gamers and their GPU/CPU cooling systems.

This combined design uses a closed-loop system and Asetek’s sealed water cooler to provide consumers with a ready-to-use, easy-to-install product. PNY claims the new system can deliver up to 30 percent improvements in cooling temperature, noise and performance compared to a standard reference-design Nvidia GeForce GTX 580 graphics card.

Thermal management through water cooling is also employed in a wide variety of power devices such as thyristors, MOSFETs, and silicon-controlled rectifiers (SCRs). The XW180GC34A/B developed by Westcode Semiconductors, a subsidiary of Ixys Corporation, is a good example. This nickel plated heat sink features a 127mm diameter contact pad, ideal for press pack devices with electrode contacts up to 125mm diameter.

Typical heat sink to input water thermal resistance at 10 L/min flow rate is 4.3K/kW (two coolers plus one semiconductor device) and 5.6K/kW (three coolers plus two semiconductor devices). Heatsinks may or may not have complete connecting bus bars.

“Typical applications for coolers are mini megawatt power stage devices and high power rectifiers, such as in heavy industrial applications, or in substations next to electric train tracks, and in power generation and distribution applications.” Westcode Marketing & Technical Support “The efficient cooling provided by these coolers can help consumers achieve higher power density systems in a smaller footprint,” said manager Frank Wakeman.