Copper Aluminum Bonding Heatsink Process

    At present, the most commonly used heat sink materials are copper and aluminum alloys. Aluminum alloy is easy to process and low cost, so it is also the most used material. In contrast, copper has better thermal conductivity than aluminum alloy, but the heat dissipation rate is slower than aluminum alloy. 

      Considering the respective disadvantages of copper and aluminum, some heatsinks are made of copper and aluminum. These heat sinks usually use copper base, while the heat sink fins still use aluminum alloy. In addition to copper base, there are also methods such as copper column for heat sink, which is also the same principle. With high thermal conductivity, the copper bottom can quickly absorb the heat released by the CPU or other heat source; Aluminum fins can be made into the shape of  most conducive to heat dissipation with complex processes, and provide large heat storage space and rapid release.

       The combination of the two metals is difficult, and the affinity between copper and aluminum is poor. If the bonding treatment is not good, it will produce large interface thermal resistance. Common copper aluminum bonding processes include:

Soldering

     Soldering is a welding process that uses a metal material with a melting point lower than the melting point of the base metal as the solder, wetts the base metal with liquid solder at a temperature lower than the melting point of the base metal but higher than the melting point of the solder, fills the joint gap, and then condenses to form a firm joint interface.

   A very stable oxide layer (Al2O3) will be formed on the aluminum surface in the air, which makes the copper aluminum soldering more difficult, which is the biggest factor hindering the soldering process . It must be removed or chemically removed and plated with a layer of nickel or other easily welded metal so that copper and aluminum can be welded together smoothly.

Screw Locking:

      Screw locking is the combination of thin copper sheet and aluminum bottom surface through screws. The main purpose of this is to increase the instantaneous heat absorption capacity of the heatsink and prolong the life cycle of some mature pure aluminum radiators. After the test, it is found that the high-performance heat conduction medium is used between the bottom of the aluminum heat sink and the copper block. After being pressed with a force of 80kgf, it is locked with screws. The heat dissipation effect is equivalent to that of copper aluminum welding, and the expected improvement of heat dissipation efficiency is also achieved.

    This method is simpler than soldering, with stable quality, simple process and lower cost. However, it is only used as an improvement,  the performance improvement is not obvious. Although filled with heat dissipation paste, the incomplete contact between copper sheet and aluminum bottom is still the biggest obstacle to heat transfer.

Plug copper:

    There are two main ways to plug copper. One is to embed copper into aluminum base plate, which is common in heatsink manufactured by aluminum extrusion process. Due to the limited thickness of the bottom of the aluminum heatsink, the volume of embedded copper is also limited. The main purpose of adding copper sheets is to strengthen the thermal conductivity of the heatsink, and the contact with the aluminum radiator is also very limited. Therefore, in most cases, the effect of this copper aluminum heatsink is not much better than that of the aluminum sink. 

    Another is to insert copper columns into aluminum radiators with radial fins. However, we should pay attention to the quality control of the diameter size and surface roughness of the copper column and round hole, which will have a certain impact on its heat dissipation effect.

Crimped Fin:

    Crimped fin technology improves the traditional copper aluminum combination technology. Firstly, machining the groove on the copper base , and then the aluminum sheet is inserted. The aluminum sheet is combined into the copper base by using more than 60 tons pressure . There is no medium between aluminum and copper. From the microscopic point of view, the atoms of aluminum and copper are connected to each other to some extent, so as to completely avoid the disadvantages of interface thermal resistance caused by the traditional copper aluminum combination and greatly improve the heat transfer capacity of the product, 

  We can also produce copper insert aluminum base, copper insert copper base and other process products to meet different heat dissipation needs. This technology fully extends the service life of some copper aluminum bonding technologies.

    There are also some other copper aluminum bonding methods, but the main process is to ensure the bonding quality of the thermal contact surface between copper and aluminum. Otherwise, its heat dissipation effect is not as good as that of all aluminum alloy heat sink. The new process needs continuous verification and improvement, and finally the expected effect can be achieved. When selecting copper aluminum combined heatsink, you must not only focus on the appearance, but also the actual comparison ,then we can buy a high-quality copper aluminum combined heatsink。