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Comparative analysis report between FSW and Vacuum brazing
In the field of cold plate (heat sink) welding in the power electronics industry, aluminum vacuum brazing and friction stir welding (FSW) are widely used in two different welding processes in the field of cold plate (heat sink) products, each welding process has its own advantages, and there are certain differences and different priorities.
This article will compare the technical characteristics of vacuum brazing and friction stir (FSW).
1、Vacuum brazing is to heat the structural parts under vacuum，it is applied to high quality product and oxidizable material;
2、Vacuum brazing is solid phase connection，the base material will not melt when welding，as the melting temperature of solder is lower than the base material, the heat temperature is lower than the base material's solid line but higher than the solder's.
3ˎIt heat the structural parts and the solder till melt at suitable temperature and time. The liquid solder will infiltrate the surface and gap of the base material, totally mix together with the base material.
4、 Vacuum brazing removes oxide film with different mechanism of actions in vacuum environment. It improves the corrosion resistance as it doesn’t use flux.
5、The invasive and fluidity is very good, so it can weld relatively complex and narrow position, and it can improve the yield.
1、It can weld several neighboring welding joint as a whole surface at one time,it can also superimposed loading, weld several components at the same time, improve the welding efficiency ;
2、All the welded products can bear 30bar internal pressure without deformation;
3、Universal tooling, one-time input cost;
4、The workpiece is heated evenly ， small thermal stress . The amount of deformation can be controlled to the minimum, and a small margin can be achieved and processed easily;
5、 The workpiece is under vacuum, no oxidation, carbonization, decarburization and pollution deterioration. Welding joints are beautiful and have no leaks ,not easy to corrode ；
6、 Cold plate channel structure can be designed complexly according to parameters ，which can make the product achieve better performance and more stable heat dissipation characteristics.
1、The hardness of the cold plate will be lower after high temperature welding, so the cold plate need to do heat treatment again to improve the hardness which lead the cost increases.
2、The welding process requires high technological standard, which takes long time and high energy.
3、 High cost of environmental protection .
The process of friction stir welding: a cylinder or other shape (such as a threaded cylinder) is inserted into the joint of the workpiece, and the high-speed rotation of the welding head causes it to rub against the material of the welding workpiece, thereby making the joint the temperature of the material rises and softens. Then makes it move with the welding heat along the welding interface. The transformative material deposit behind the welding head and become solid welding joint under the pressure of mould.
1、 Low welding temperature, small change in microstructure in heat affected zone ；the hardness of the cold plate will not change.
2、 The operation process is convenient to realize mechanization, automation, low energy consumption, and low requirements on the working environment.
3、 No need to add welding wire or remove oxide film before welding, no protective gas.
4、 The welding process is safe, non-polluting, smokeless, etc.
5、 Energy saving, environmental protection, low cost .
1、It can only weld the welding joint one by one, linear welding , so the welding speed is not fast；
2、 The wear of the mixing head is fast .
3、 High fixture requirements and high input costs .
4、 At the end of the weld, there will be a process hole at the end of the weld, which requires complex design and processing of the process hole.
5、 The amount of deformation of the product after welding is relatively high.
6、 The design of the channel should be simplified, and the internal structure of the cavity cannot be complicatedly welded. When the heat dissipation requirement is difficult to meet it is necessary to increase the flow rate to make up for the requirements, which lead the cost increase.