The manufacturing process of copper and aluminum heat sink (radiator) includes: Crimped Fin, Skewer welding, Patch and screw locking combination,Plug copper, embedded copper tube (mechanical compression, thermal expansion and cold contraction combined).
Skewer welding combination of copper and aluminum heat sink
Skew welding uses a metal material with a melting point lower than that of the base material as the solder. At a temperature lower than the melting point of the base material but higher than the melting point of the solder, liquid solder is used to wet the base material, fill the joint gap, and then condense to form a solid joint interface. The main processes are: material pre-processing, assembly, heating welding, cooling, post-processing, etc. The commonly used skewer welding method is tin skewer welding. A very stable oxide layer (AL2O3) will be formed on the surface of aluminum in the air, which makes copper-aluminum welding more difficult, which is the biggest factor hindering welding. It must be removed or chemically removed and electroplated with a layer of nickel or other easily weldable metal, so that copper and aluminum can be welded together smoothly.
The copper bottom base on the heat sink is for heat conduction. What is required is not only mechanical strength, but more importantly, a large welding area (high welding rate) in order to effectively improve heat dissipation efficiency. Otherwise, not only will it not improve the heat dissipation performance, but it will make it worse than the all-aluminum heat sink.
Patch and screw locking combination
The patch process is to combine a thin copper sheet with an aluminum base surface through screws. The main purpose of this is to increase the instantaneous heat absorption capacity of the radiator and extend the life cycle of a part of the mature pure aluminum radiator. After testing, it was found that: Use a high-performance heat-conducting medium between the bottom of the aluminum heat sink and the copper block, apply a force of 80Kgf to compress it, and then lock it with screws. Its heat dissipation effect is equivalent to that of copper-aluminum welding, and it also achieves the expected increase in heat dissipation efficiency.
This method is simpler than welding, with stable quality, simple manufacturing process, and lower investment equipment cost than welding, but it is only an improvement, so the performance improvement is not obvious. Although filled with thermal paste, incomplete contact between the copper sheet and the aluminum bottom is still the biggest obstacle to heat transfer.
The main manufacturing processes are: Copper sheet cutting and leveling (flatness less than 0.1mm, drilling, drilling after applying heat transfer medium, tapping, cleaning, strong pre-compression process, two-stage lock cooperation, fixed torque lock screw.
The focus of the patch process is to control the flatness and roughness of copper, aluminum, and the torsion force of the locking screw, so that a certain degree of performance can be improved. It is a good combination of copper and aluminum. If the heat conduction medium used is inferior, or the flatness of the copper block is poor, the heat cannot be smoothly transferred to the surface of the aluminum heat sink, which greatly reduces the heat dissipation effect. In addition, the locking force of the screws and the purity of the copper material are not enough, which are both negative factors.
Copper plug and copper embedded processing combination
There are two main ways to plug copper: one is to embed the copper sheet in the aluminum base plate, which is commonly used in the radiator manufactured by the aluminum extrusion process. Due to the limited thickness of the bottom of the aluminum radiator, the volume of the embedded copper sheet is also limited. The main purpose of adding copper fins is to strengthen the instant heat absorption capacity of the radiator, and the contact with the aluminum radiator is also very limited. So in most cases, this kind of copper-aluminum radiator is not much better than aluminum radiator. In the case of poor contact, it will even hinder heat dissipation. Another is to embed copper pillars in an aluminum radiator with radial fins. Intel original radiator adopts this design. The volume of the copper pillar is relatively large, and the contact with the heat sink is relatively sufficient. With the use of copper pillars, the heat capacity and instantaneous heat absorption capacity of the radiator can be enhanced. This design is also used more by OEMs.
The rarer triangular base of the heat sink
The copper plug process is generally implemented in the following ways in manufacturing:
Mechanical pressing of heat sink
The mechanical pressing method is to press a piece of copper block with a diameter larger than the aluminum aperture by mechanical means to press it together. Because aluminum is malleable, copper can be combined with aluminum heat sinks at room temperature. The effect of this method of combination is also considerable, but there is a fatal disadvantage that the inner surface of the aluminum hole is easily scratched by the copper when the copper is squeezed into the aluminum hole, which seriously affects the heat conduction. This is to avoid such problems by reasonably matching the interference and optimizing the shape of the copper block.
Combination of thermal expansion and contraction of heat sink
A circular hole with a diameter of ψ=D1 is machined at the bottom of the aluminum heat sink, and a copper column with a diameter of ψ=D1+0.1MM is also made. Using the characteristics of thermal expansion and contraction of metal materials, the aluminum heat sink is heated to 400°C, and the diameter of the heated expansion hole expands to D1+0.2MM. Use a special machine to quickly insert the normal temperature (or cooled) copper cylinder into the round hole of the aluminum heat sink at high temperature. After it cools and shrinks, the copper column and the aluminum heat sink can be tightly integrated into one body. This is also a reliable method. Its copper and aluminum have high stability, and since no third-party media is used, the tightness of the bond is best. The copper plug process can greatly reduce the thermal resistance between the contact surfaces, which not only ensures the tightness of the copper-aluminum bond, but also makes full use of the heat dissipation characteristics of the two metal materials.
But pay attention to the quality control of the diameter and surface roughness of the copper pillars and round holes, which will have a certain impact on the heat dissipation effect.
After the copper plug process is processed, the bottom surface of the radiator is often processed by "milling" and "grinding". The milling process is aimed at the copper core in the copper plug processing, and the grinding process is aimed at the bottom of the entire heat sink.
Forging process of copper and aluminum radiator (cold forging)
The forging process is mainly controlled by the ALPHA company, which is to press the metal into the forging die under high pressure under the special physical state (yield state), and preset the copper block on the die and stuff it into the yielded aluminum. Due to the special properties of aluminum in the yield state (non-liquid, soft, and easy to process), copper and aluminum can be perfectly combined to achieve no voids in the middle, and the interface thermal resistance is very small. The forging process is difficult and the cost is high, so the finished product is expensive and belongs to non-mainstream products. The heat sink using this process generally has many densely packed pin-shaped fins. The heat sink manufactured by this process has rich styles, and the design imagination is larger, but the cost is relatively high.
Hot-shaping combination of copper and aluminum heat spreader (Crimped Fin)
Crimped Fin process boldly improves the traditional copper-aluminum bonding technology. First go out the copper plate into a small groove, and then insert the aluminum sheet. Using more than 60 tons of pressure, the aluminum sheet is combined in the base of the copper sheet, and no medium is used between aluminum and copper. Microscopically atom of aluminum and copper in a way to each other, thus completely avoiding the drawbacks of the conventional copper and aluminum combine to produce thermal resistance of the interface, greatly improving the thermal conductivity of the product, and may produce aluminum copper plug seat . Brass and other copper plug technology products, to meet different cooling requirements. This technology significantly extends the life of some copper-aluminum bonding technologies.
In addition to the above, there are some copper-aluminum bonding methods, but the process is mainly to ensure the bonding quality of the copper and aluminum thermal contact surface, otherwise the heat dissipation effect is not as good as the all-aluminum heat sink. The new manufacturing process requires continuous verification and continuous improvement to finally achieve the desired effect. Don't just look at the appearance when choosing a copper-aluminum radiator. Only by actual comparison can we buy a high-quality copper-aluminum combined radiator.
