AVS 51st International Symposium
    Materials Solutions for Cooling Technology Topical Conference Monday Sessions
       Session CT-MoA

Invited Paper CT-MoA3
Challenges and Opportunities for Cooling Advanced Semiconductor Devices

Monday, November 15, 2004, 2:40 pm, Room 303B

Session: Material Solutions for Chip Cooling
Presenter: D. Seeger, IBM T.J. Watson Research Center
Correspondent: Click to Email
As CMOS technology continues to evolve, direct scaling has become increasingly difficult. As a result, the rules of scaling have been 'fudged' in order to stay on the historical Moore's law curve. In particular, power has not decreased at a rate consistent with Moore's Law though chip area has scaled. As a result, chip power densities are increasing rapidly. Chip power densities for CMOS technologies today rival that of bipolar devices of the last decade. At that time, the industry was focused on developing advanced chip cooling technologies to deal with the high powered bipolar devices of the time. However much lower power CMOS device technology came along to ‘save the day’ and allowed most of these advanced chip cooling technologies to be shelved. Today we face a similar situation for chip power densities. However there is no comparable low power technology on the horizon and as a result, the power density problem must be solved. In thinking about this problem from the chip to the package, the first surface the chip faces is typically a heat spreader made of copper or other high thermal conductivity material. In order to insure good thermal contact, a thermal interface material (TIM) is sandwiched between the chip and the heat spreader. These materials are two orders of magnitude better in thermal conductivity than air, hence the reason for their existence. However, they are typically two orders of magnitude LOWER in thermal conductivity than the other materials in the chip/package stack. Given that this is the most important interface in the stack, a lot of focus has been placed on improving the thermal conductivity of TIMs. Since the heat spreader has a significantly different thermal coefficient of expansion than the chip, compliant mechanical considerations are also important. Then, intimate thermal contact to an efficient heat sink must be accomplished. Once at the heat sink level, the heat must be expelled to the air and then carried out through the computer box, racks in the case of servers. Finally, this heat needs to be removed from the data center. All of the above components must be optimized as a system since any single point in the thermal path can choke off the flow of heat and dramatically decrease the efficiency of heat removal from the system. This talk will be an overview of these issues and the technologies being developed to overcome them