Challenges in Cooling Design of CPU Packages for High-Performance Servers


Jie Wei
Corporate Product Technology Unit, Fujitsu Limited , Kawasaki , Japan

Cooling technologies that address high-density and asymmetric heat dissipation in CPU packages of high-performance servers are discussed. Thermal management schemes and the development of associated technologies are reviewed from a viewpoint of industrial application. Particular attention is directed to heat conduction in the package and heat removal from the package/heat sink module. Power dissipation and package cooling characteristics of high-performance microprocessors are analyzed. The development of a new metallic thermal interface technology is introduced, where thermal and mechanical performance of an indium-silver alloy in the chip/heat spreader assembly was studied. The paper also reports on research on other thermal management materials, such as diamond composite heat-spreading materials. Some actual package designs are described to illustrate the enhanced heat spreading capability of heat pipes and vapor chambers.


고성능 서버의 CPU 패키지에서 고밀도 및 비대칭 열 방출을 처리하는 냉각 기술이 논의된다. 열 관리 체계와 관련 기술의 개발을 산업 적용 관점에서 검토한다. 패키지의 열 전도 및 패키지/열 싱크 모듈에서 열 제거에 특히 주의하십시오. 고성능 마이크로프로세서의 전력 소산 및 패키지 냉각 특성을 분석한다. 칩/열 확산기 조립체에서 인듐-실버 합금의 열 및 기계적 성능을 연구한 새로운 금속 열 인터페이스 기술의 개발이 도입되었다. 이 논문은 또한 다이아몬드 복합 열 확산 재료와 같은 다른 열 관리 재료에 대한 연구도 보고한다. 일부 실제 패키지 설계는 열 파이프와 증기 챔버의 향상된 열 확산 능력을 설명하기 위해 설명된다.

Figure 1 A typical structure of CPU package and heat sink module.
Figure 1 A typical structure of CPU package and heat sink module.
Figure 3 Liquid-cooled MCM package of Fujitsu GS8900 (Turbo).
Figure 3 Liquid-cooled MCM package of Fujitsu GS8900 (Turbo).
Figure 5 Temperature distribution on a test processor chip.
Figure 5 Temperature distribution on a test processor chip.
Figure 10 Impact of voids in TIM-1 on temperature distribution on the chip.
Figure 10 Impact of voids in TIM-1 on temperature distribution on the chip.
Figure 15 Comparison of various heat sinks in terms of their cooling performance and weights.
Figure 15 Comparison of various heat sinks in terms of their cooling performance and weights.


Challenges in thermal management of CPU packages for high-performance servers are discussed. Described in this paper are the characteristics of power dissipation in the recent generation of CPU processors, the investigations conducted to incorporate advanced thermal interface and heat-spreading materials in the package design, and the evaluations of enhanced cooling capability of air-cooled heat sinks. With further miniaturization and increasing complexity of devices and components in high-performance processors, challenges will continue to mount in the thermal design of high-performance servers. The industry is facing the critical needs for extending the limits of conventional technologies that are attractive from a cost perspective, while attempting aggressively to make advanced cooling solutions viable options.


고성능 서버용 CPU 패키지의 열 관리 문제에 대해 논의한다. 이 논문에서 기술된 것은 최근 세대의 CPU 프로세서에서 발생하는 전력 소산의 특성, 패키지 설계에 첨단 열 인터페이스와 열 확산 재료를 통합하기 위해 수행된 조사, 그리고 공랭식 열제거원의 강화된 냉각 기능에 대한 평가 등이다. 고성능 프로세서에서 소자와 구성품의 소형화와 복잡성이 증가함에 따라, 고성능 서버의 열 설계에 대한 도전은 계속 증가할 것이다. 업계는 비용 측면에서 매력적인 기존 기술의 한계를 확장하는 동시에 첨단 냉각 솔루션을 실행 가능한 옵션으로 만들기 위해 적극적인 노력을 기울여야 하는 중요한 요구에 직면해 있다.


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