Peter Rodgers

In situ temperature measurement of a notebook computer - a case study in health and usage monitoring of electronics

Reliability prediction methods do not generally account for the actual life cycle environment of electronic products, which covers their environmental, operating and usage conditions. Considering thermal loads, thermal management strategies still focus on a design for continuous operation that is often determined based on an accumulation of worst-case assumptions. Health monitoring is a method of assessing the reliability of a product in its actual application conditions. A case study in health and usage monitoring of electronic products is presented for a commercial notebook computer. Internal temperatures were dynamically monitored in situ and statistically analyzed during all phases of the life cycle, including usage, storage, and transportation. The effects of power cycles, usage history, CPU computing resources usage, and external thermal environment on peak transient thermal loads were characterized. Such monitored life cycle temperature data could be applied in a life consumption monitoring methodology, to provide damage estimation and remaining life prediction due to specific failure mechanisms influenced by temperature. These findings could contribute to the design of more sustainable, least-energy consumption thermal management solutions.

Limits of air-cooling: status and challenges

Despite the perception that the limits of air-cooling have been reached, this paper reviews approaches that could maintain the effectiveness of this technology. Key thermal management areas that need to be addressed are discussed including heat sink design and analysis, interface thermal resistance minimization, heat spreading, fan performance, hybrid thermal management, heat sink surface fouling, and sustainability.

Extending the limits of air-cooling in microelectronic equipment

Despite the perception that the limits of air-cooling have been reached, this paper reviews approaches that could maintain the effectiveness of this technology. Key thermal management areas that need to be addressed are discussed, including heat sink design and analysis, interface thermal resistance minimization, heat spreading, fan performance, hybrid thermal management, heat sink surface fouling, and sustainability.

Prediction of electronic component-board transient conjugate heat transfer

Numerical analysis of electronic component transient heat transfer has generally been confined to nonconjugate methods. This study discusses the need for conjugate (conduction/convection) analysis, both for component temperature and thermo-mechanical behavior prediction in operational, assembly and reliability qualification environments. The capability of computational fluid dynamics (CFD) analysis to predict component transient conjugate heat transfer is investigated using an industry-standard CFD code for the thermal analysis of electronics. The test cases are based on a single board-mounted, 160-lead plastic quad flat pack (PQFP) component, subjected to dynamic power- and air temperature conditions, in still-air and forced airflows. Benchmark criteria are based on component junction temperature and component-printed circuit board (PCB) surface temperature, measured using thermal test dies and infrared thermography respectively. Using both nominal component/PCB geometry dimensions and material properties, component junction temperature is found to be accurately predicted. The results suggest that CFD analysis could play an important role in providing critical boundary conditions for component electrical performance and thermo-mechanical behavior analyses, optimizing accelerated life test (ALT) parameters and convective assembly processes.

Reliability of pressure-sensitive adhesive tapes for heat sink attachment in air-cooled electronic assemblies

This study investigates the reliability of commercially available pressure-sensitive adhesive (PSA) tapes used for electronic component-to-heat sink attachment. It is found that creep can affect the PSA reliability. Therefore, creep is experimentally characterized using isothermal, constant load, double lap shear measurements in conditions representative of vertically oriented heat sink applications. PSA joint life predictions are derived from the accelerated creep characteristics using a secondary creep model. The creep resistance of a laminated silicone/aluminum/acrylic PSA tape is found to be significantly lower than that of a single-layer acrylic tape. This suggests that the potential impact of tape creep on joint reliability should be carefully evaluated as a function of tape chemistry/construction and application environment. Furthermore, the sensitivity of PSA creep characteristics to both operating temperature and heat sink weight highlights the need for thermally optimized, least-weight heat sink designs.

Prediction of thermal performance degradation of air-cooled fine-pitch fin array heat sinks due to fouling

The fouling of air-cooled fine-pitch heat sinks by air born dust particles has become a major reliability concern for desktop and notebook personal computers, where significant thermal performance degradation can result. This paper investigates for the first time heat sink fouling mechanisms by both analytical and experimental analyses. The contribution of two fouling modes, namely accumulation of a thermally insulative dust coating on the fins within the heat sink channels, and blockage of the heat sink leading edge entrance, is quantified. It is found that the former fouling mode does not significantly increase heat sink thermal resistance. Instead, heat sink thermal performance degradation is essentially attributable to leading edge entrance blockage, which reduces the airflow rate through the heat sink by increasing pressure drop