Are We Cool?

By Francoise von Trapp, Sr. Technical Editor

At IWLPC 2011, held Oct 6-8 2011 in Santa Clara, CA, Raj N. Master, General Manager for IC Packaging, Silicon Operations, Quality and Reliability for all hardware products, Microsoft, both informed and entertained the attendees during the dinner keynote address. The topic of his talk was Thermal and Power Considerations in Electronics Packaging, and Master really drove home the importance of these issues, especially as our computing devices become smaller and more portable.

Traditionally, Master noted, thermal management has been handled at the system level through the strategic use of fans and heat sinks inside the computer enclosure. However, recent technologies using high density ICs, 3D packaging and higher levels of integration creates chips that are so hot, thermal issues could become a show stopper; rendering products incorporating the latest Si advances as un-usable. This has galvanized new research into chip designs, novel materials and thermal solutions that could allow electronics to run much cooler and remove the roadblocks presented by thermal management.

We don't often give it the credit its due, but Master's talk really drove home the point that ultimately, thermal and power is the driving force for all technology. He said that since we can't afford to generate products inside a refrigerator, we need to put the refrigerator inside the product.

To illustrate his point while keeping the dinner crowd engaged, Master talked about real-life thermally provoked situations many of us have experienced when using electronics devices. He talked about "hot crashes" when laptops overheat and shut down in the middle of a critical point. The device must be allowed to completely cool before powering up again, and can result in interrupted workflow, and at times, loss of data. Then there's the "Hot Thighs" situation, where users have experienced burns from working on laptop. Male infertility has even been tied to using laptops and notebooks, because of the increased temperature to - ahem - let's just say a fertility- critical anatomical region. One study of handheld devices showed that temperatures in excess of 40-45°C next to the skin can cause damage . Therefore <40°C must be kept as a benchmark acceptable-for-use temperature for all portable devices.

As the whole world is going mobile and consumers are ubiquitous, thermal and reliability issues become a bigger challenge for Si packaging technologies. Thermal issues aren't just about causing physical harm. Poor thermal management also drastically affects the device reliability. How many of us have experienced device failure purely related to poor thermal management? However, "Few people will buy a device based on reliability, but everyone will expect it to be reliable," notes Master. So once again, thermal management may not be seen as a value-add situation, but is quite necessary to the final product.

Doubling densities through 3D integration, (or 2.5D integration) to improve performance is useless if the thermal issues haven't been addressed, because it can result in degraded performance if the heat can't be dissipated. Many solutions addressing thermal management at the device and chip level such as chip cooling with thermoelectric coolers, copper pillar bumps, microfluidic cooling, and carbon nanotubes have been demonstrated and suggested, noted Master, but few of them have been implemented in the market to address today's Si packaging advancements. Master called for a Thermal Management Roadmap. He said that thermal management solutions need to survive shock, drop, impact, bending, and other physical impact situations. A portable hydrodynamic cooling device might be one option.

Ultimately, Master left the attendees with a renewed respect for thermal management and power solutions, and the importance these holds for the future of electronic packaging. Thermal management is not just a nuisance that will solve itself. These solutions are critical to the future of electronic packaging technologies.