This document is written for professional system integrators building Mobile PCs from industry-accepted build-to-order laptops. It provides information and recommendations for thermal management in systems using Intel® Core™2 Extreme mobile processors.
It is assumed that the reader has a general knowledge of, and experience with, PC operation, integration, and thermal management. Integrators who follow the recommendations presented here can provide their customers with more reliable PCs and will see fewer customers returning with problems.
Laptop thermal management
Laptops using Intel Intel® Core™2 Extreme mobile processors all require thermal management. The term "thermal management" refers to two major elements: a cooling solution properly mounted to the processor, and effective airflow through a part of that cooling solution to evacuate heat out of the system. The ultimate goal of thermal management is to keep the processor at or below its maximum operating temperature (Tcase).
A typical laptop cooling solution is far more sophisticated than that for desktop systems. Due to limited space, varying laptop design, layout, and processor location, laptop cooling solutions vary greatly between laptops from different manufacturers. In all laptops, however, the processor may use one or both of two cooling methods: passive and active.
For higher power processors today, almost all laptops employ some form of an active cooling solution. This can be accomplished in one of two ways:
- By using a heatsink attached directly to the processor
- By using a Remote Heat Exchanger
A Remote Heat Exchanger, or RHE, offers more flexibility in thermal design because the actual heatsink and fan can be placed far from the processor. Figure 1 shows the RHE design concept.
Figure 1: Typical remote heat exchanger design
Heat is transferred from the processor to an attachment block, through which runs a heat pipe. A heat pipe is typically a hollow copper pipe containing a fluid and wicking material. Through a process of vaporization and re-condensation, heat travels through the very efficient heat pipe to the fins of a heat exchanger (heat sink). Localized airflow then evacuates the heat to the outside air.
Although the RHE design is very efficient, some notebook designs may use the RHE design together with a passive element to increase the cooling efficiency of the solution. Usually, to add a passive element, a large metal plate is attached to a part of the RHE design that allows additional heat to dissipate passively, typically from under the keyboard. Figure 2 shows examples of actual thermal solutions using a remote heat exchanger. The figure on the right shows an additional passive component.
Figure 2: Typical Micro-FCPGA Thermal Solutions Designs
Highly efficient cooling solutions rely heavily on proper processor installation to work. In all laptop designs, after the processor is installed, it must be attached to the notebook cooling solution. Generally, a thermal interface material is used to provide efficient thermal exchange between the processor and attachment block. The thermal interface material type may vary depending on the laptop manufacturer.
Proper installation of this thermal interface material is crucial to the success of the thermal solution.
Failure to properly install the thermal interface material could cause the processor to overheat. Follow the manufacturer's instructions carefully to ensure the thermal interface material makes 100% contact with the processor's exposed die and with the notebook's thermal solution attachment block. Also, never touch the thermal interface material as any foreign substances (such as oils from your skin, or chemicals) can reduce the effectiveness of the thermal contact between the processor and the attachment block.
Note: If the thermal interface material is removed from the processor, the thermal interface material will most likely need to be replaced. Since laptop designs vary, different manufacturers use different thermal interface material. As a result, Intel does not provide the thermal interface material. Contact your place of purchase or laptop manufacturer to obtain replacement thermal interface material.
In addition, if a laptop uses an additional passive thermal solution, such as a plate underneath the keyboard, this passive solution must be re-attached carefully. Systems that utilize an additional passive thermal system rely on it to meet the cooling requirements of the entire system.
Integrators building Intel® Core™2 Extreme mobile processor-based laptops should consult their manufacturer to determine the highest power processor your laptop will support. Although most laptops support throttling - a method of slowing down the processor if it exceeds its maximum operating temperature - it may cause a reduction in performance and should not be relied upon to manage the processor thermal solution.
Thermal testing may not be needed if the processor is installed correctly and the system is designed to accommodate the power of the processor. Nonetheless, your laptop manufacturer may provide software utilities to assist in monitoring the processor temperature. Intel® Core™2 Extreme mobile processors have built-in thermal sensors, and most laptops have built-in circuitry to convert the sensor reading into a real temperature, so processor temperatures can be monitored. Consult your notebook manufacturer for availability of a thermal monitoring utility.
Use of thermocouples to measure processor temperature may be impractical, as any attachment of thermocouples will likely compromise the performance of the thermal solution.
For more information on the Intel® Core™2 Extreme mobile processor thermal specifications, refer to the Intel® Core™2 Extreme Mobile Processor Datasheet.