一般来说，相变材料是指从固态变为液态或从液态变为固态时会储存或释放能量的材料。
- 盐水合物，如硫酸钠、氯化钙、醋酸钠等
- 共晶盐
- 石蜡
- 非石蜡有机物
不过，这些相变材料类别并非包罗万象。其他材料，如金属，无论是否共晶，都可用作相变材料，以发挥其热能存储和去除能力。
Nearly all soft solders classify as phase change materials according to their melting temperature.According to Maurice J. Marongiu from MJM Engineering, who conducted a webinar on phase change materials, the melting temperature of a typical phase change material is between 0-250ºC.Solders officially may melt at higher temperatures, such as the AuGe eutectic alloy which melts at 356ºC, however the majority of solders used melt below 250ºC.
Phase change materials are a common occurrence in the world of thermal interfaces for electronics.Here, tighter commonalities between phase change materials can be found.For instance, the phase change temperature for these thermal interface materials is within the range of a common TIM junction temperature, which is typically lower than 100ºC.For this reason, when we consider a metal interface to be a phase change material in this industry, it is an alloy or material which changes phase below 100ºC.
在热界面中使用金属或非金属相变材料时，需要考虑一些设计因素：
- Phase change materials are applied as solid pads.At room temperature they are firm and available with specific dimensions which make them easy to handle.Consistent application should be inherent.
- Phase change materials each change phase at a unique temperature.The appropriate phase change material engineered for an application will have a phase change temperature reached within the normal operating cycle of the device.
- Phase change materials are designed to turn liquid in operation.The liquid phase of these materials will have a distinct viscosity.Depending on the material, clamping pressure and assembly orientation, the molten material may leak.Proper precautions should be taken to prevent material leakage, especially toward active electrical components if the phase change material is electrically conductive.
- 当相变材料从固态变为液态时，材料的体积会增大。如果相变材料膨胀并使储层破裂，这将导致泄漏，并由于热界面被空气回填而最终导致电子设备失效。
