What are Through and Reflow Soldering?
Through Fin & Reflow Soldering (soldering) refers to the way the fin is connected to the heat pipe.
In a heat sink, the fins need to absorb the heat conducted by the heat pipe and dissipate it into the air with the help of wind. Therefore, the contact method between the heat pipe and the fin has become one of the keys to determine the heat dissipation efficiency.
Reflow Soldering Features
Reflow soldering, by soldering, the fins are firmly welded to the heat pipe. First brush solder on the heat pipe, then thread the fins into the heat pipe, and finally put the heat sink into the reflow machine to warm it up. After the solder paste is heated, the gap between the heat pipe and the fin is filled due to gravity and capillary action, and the finished product is finally obtained.
On the heat sink fins that use reflow soldering, small openings are generally reserved for solder filling and solder paste reflow. When reflow soldering is used, the small holes next to the heat pipe will slowly be filled with solder paste and disappear.
The characteristics of reflow soldering are that the fin connection is relatively firm and tight, but the disadvantages are high cost and long process.
Through Fin Features
The so-called "Through Fin" is a way of joining materials at low temperature. That is, through the external force and the elasticity between the materials, the fins are tightly "embedded" into the heat pipe to achieve heat conduction.Fitting the heat pipe and fins tightly is like forcing a large part into a small hole.
Through Fin does not require solder and high temperature, so the material cost is lower. However, the Fin-wearing process is easy to wear out, and the high-quality Fin-Through process requires high tolerances. Once it fails, it is difficult to restart, and the yield rate will be greatly affected. If the tolerance requirements are reduced, the cost will be lower, but the joint between the fin and the heat pipe will become loose again.
Due to the difference between the thermal expansion coefficients of copper and aluminum, the heat sinks needs to undergo frequent high and low temperature transformations, as well as repeated disassembly and assembly. After using long time, there may be gaps between copper and aluminum, which will loosen the originally tight fins, resulting in a decrease in heat dissipation efficiency.
In fact, welding is difficult due to the different materials between copper and aluminum. Typically a transition layer - usually nickel on the heat sink - is required to assist with reflow. Nickel itself is a metal with poor thermal conductivity, and the thermal resistance of solder (tin) is also very high.
Therefore, in principle, because there are two to three layers of high thermal resistance substances between the heat pipe and the fins, the reflow soldering can never achieve the true thermal resistance of 0, so the thermal conductivity is not the highest. Similarly, the theoretical efficiency of nickel-plated heat pipes, nickel-plated bases and nickel-plated fins is not the highest.
On the other hand, through Fin, ideally, the thermal resistance of high-quality through Fin is far lower than that of reflow products, and the performance is stronger. However, the technical requirements of through fin are high, so there are not many through fin products with high yield.
Why are reflow soldering products often stronger on the market?
Limited by the ultra-high tolerance requirements of the high-quality through fin process, there are very few manufacturers on the market that can make high-quality through fins. Most fin products often have large tolerances and cannot take advantage of low thermal resistance. The connection is not strong at all. High-quality through fins have little cost advantage, and reflow soldering is more mature and firm, so it is more favored by high-end heatsink manufacturers.
For consumers, there are special requirements for durability, so through Fins that may decay with use are not popular.
However, it should be noted that reflow soldering and high performance still cannot be equated, and be wary of low-quality reflow soldering products.
