Aunque muchas tiendas locales pueden fabricar una placa fría tubular simple, una placa fría diseñada y fabricada correctamente basada en la aplicación dará como resultado un rendimiento y una confiabilidad significativamente mejores. However, assessing the quality of a cold plate can be difficult if you do not know what to look for.
How Construction Affects Tube Cold Plate Reliability and Performance
High reliability is important, as a coolant leak can be catastrophic in a liquid cooling system. First examine the tubes; they can reveal a lot about the reliability of the cold plate. A cold plate that uses continuous tubing is inherently more reliable than one constructed from straight tubes connected by soldered joints, as any joint increases the potential for leakage.
Look also at the quality of the bends. If the tube bending is not carried out carefully, the tube can be deformed. While this does not affect the reliability, it changes the cross-sectional profile of the tube, which can result in increased pressure drop and lower performance.
Next look at how the tubes are attached to the plate. For maximum thermal transfer, engineers should be careful designing cold plates utilizing epoxy between the tubing and the plate. Although epoxy can be used to keep the tube in place and keep thermal contact between the two components, it can also act as a thermal insulator when used incorrectly, such as being applied too thickly or not utilizing the correct epoxy.
Finally, examine the cooling surface of the plate. For demanding applications, direct contact between the tube and the component is best. This means that the tube surface must be flush with the aluminum plate. A common manufacturing technique is to put an over-sized tube into a channel and machine off or fly-cut the top. However, this costly technique, known as skim cutting, creates a tube section of varying thickness that affects structural integrity and performance.
Another alternative is to embed the tube below the surface of the cold plate and add copper inserts to level the surface. This technique is both expensive and limits performance. The cooling tube is further from the components being cooled, and the additional layer of epoxy required between the tube and the insert further decreases performance.
A high performance option is described in patent US# 6853555 and used in Press-lock™ CP12 and CP15 cold plates. Careful design of the locking feature and proprietary pressing techniques ensure that the tube is flush with the plate surface, providing good thermal contact with the component being cooled. This manufacturing method also ensures good metal-to-metal contact between the tube and the plate, guaranteeing excellent thermal performance and eliminating the need for epoxy. Figure 4 demonstrates the performance advantage of Press-Lock technology compared to cold plates manufactured using epoxy.
La mayoría de las aplicaciones utilizan un material de interfaz térmica (TIM, por sus siglas en inglés) entre el componente o la placa y la placa fría para ayudar a reducir al mínimo los espacios. El TIM debería ser lo más delgado posible, ya que la resistencia térmica relativamente alta del TIM relega en gran medida cualquier mejora de conductividad ofrecida por una superficie más lisa. Incrementar la fuerza de sujeción del componente o la placa a la placa fría también puede ayudar a compensar una mayor rugosidad, pero puede aumentar la tensión en la placa o el componente. La tensión de sujeción también puede aumentar el impacto de los desajustes del coeficiente de expansión térmica (CTE, siglas en inglés) a medida que la placa fría y el componente o la placa se calientan.
To avoid galvanic corrosion, utilize the same materials, or materials with similar electrical potential, throughout your cooling loop. Ensure that the plumbing, connectors and other components do not introduce a reactive metal into the system.
| Reliable | Unreliable | Alto rendimiento | Lower Performance |
|---|---|---|---|
| Continuous tube | Tube with joints | Epoxy-free construction | Inserts over tube to create flat surface |
| Flattened top surface | Skim-cut top surface | Tubes flush with surface of plate |
In addition to these considerations, other factors of cold plate performance include: fittings, connectors, materials, fluids, channel patterns or number of passes, and the associated heat exchanger. Boyd offers a variety of options in standard sizes and custom and semi-custom designs.
