Friction stir welding liquid Cooling Plate
Cooling Plate, Cold Plate, Friction Stir Solder Liquid Cold Plate/Water Cooling Plate
Ⅰ）What is Friction Stir Welding liquid cooling plate ，cold plateFriction Stir Welding liquid cooling plate is a liquid cooling plate sealed by Friction Stir Welding process. It is suitable for high power and high density fields such as IGBT, FBGA, PA, Battery, etc. By friction welding, it is possible to achieve wider flow paths than contact type embedded tube type liquid cooling plates and further reduce thermal resistance by increasing the contact area with heat generating devices. It is more flexible in handling complex flow paths and can be free from the limit of copper tube bending rounds.
Ⅱ）Introduction and principle of Friction Stir WeldingThe principle of Friction Stir Welding is to use a cylindrical or other shape (such as a threaded cylinder) stirring pin (welding pin) inserted into the seam of the workpiece, through the high-speed rotation of the stirring pin, so that the friction with the welded workpiece material, so that the temperature of the material in the joint area increases and softens. At the same time, the material is stirred and rubbed to complete the welding.
The welding process is shown in the figure "Schematic diagram of Friction Stir Welding". During the welding process, the workpiece is rigidly fixed to the backing pad, and the stirring needle rotates at high speed while moving along the seam of the workpiece relative to the workpiece. The protruding part of the stirring needle penetrates into the material for friction and stirring, and the shoulder of the stirring needle rubs against the surface of the workpiece to generate heat and to prevent the spillage of the plastic state of the material, and to remove the surface oxide film. During the welding process, the stirring needle sticks into the seam of the workpiece while rotating. The frictional heat between the rotating stirring needle (shoulder position) and the workpiece causes strong plastic deformation of the material in front of the stirring needle head, and then as the stirring needle moves, the highly plastic deformed material is gradually deposited behind the stirring needle, forming a dense solid-phase weld.
The weld has excellent mechanical properties and small welding deformation. The welding process does not require the addition of shielding gas and welding wire, and there is no melting, soot, spatter and arcing, which is an environmentally friendly new joining technology. Friction stir welding technology has many unique advantages, for light alloy materials (such as aluminum, copper, magnesium, zinc, etc.) connection in the welding method, mechanical properties and production efficiency of other welding methods incomparable superiority.
Friction Stir Welding diagram
Ⅲ）History and applications of friction stir weldingFriction Stir Welding (FSW) is an invention patented by the British Welding Institute (TWI) in October 1991. TWI has conducted more research on the characteristics and applications of the Friction Stir Welding process, and applied for patents in 1993 and 1995 respectively. this technology to expand its application. The Edisonwelding Institute (EWI) in the United States, in close collaboration with TWI, is also conducting research on the FSW process. U.S. Lockheed Martin Aerospace, Marshall Space Flight Center, the U.S. Naval Institute, Dartmouth University, the University of Texas, the University of Arkansas, the University of South Carolina, Germany's Stuttgart University, Australia's Adelaide University, the Australian Welding Institute, etc., from different perspectives on the Friction Stir Welding technology has been Specialized research.
Friction stir welding process is the most striking welding method since the introduction of laser welding. Its emergence will lead to a major change in the joining technology of non-ferrous metals such as aluminum alloys. Welding aluminum alloys with Friction Stir Welding technology has achieved very good results. Now in the United Kingdom, the United States and other countries are being carried out in the Friction Stir Welding of zinc, copper, titanium, mild steel, composite materials, etc.
Friction Stir Welding technology is now widely used in the following industries.
Aerospace industry: cylinder structure fuel tanks, instrument compartments, ammunition compartments, etc.
Aviation industry: fuselage panels, wing panels, cargo compartment floors, hatch covers, etc.
Marine industry: wide aluminum alloy ribbed plate, etc.
Train industry: complete car body, side wall, floor, top plate, pillow beam, hook plate, etc.
Electronic power industry: fin radiator, liquid cooling radiator, heat sink, etc.
Automobile industry: aluminum alloy wheel hub, battery pack, liquid-cooled sleeve, liquid-cooled motor shell, etc.
Ⅳ）Advantages of Friction Stir Welding1) Small changes in the microstructure of the heat-affected zone of the welded joint. The residual stress is relatively low, and the welded workpiece is not easily deformed.
2) The welding of long seams, large sections and different positions can be completed at one time.
3) The operation process is convenient to achieve mechanization, automation, simple equipment, low energy consumption, high efficiency, low requirements for the operating environment.
4) Friction Stir Welding is a solid-phase welding, which does not require the addition of welding wire, welding aluminum alloy does not require pre-weld oxide film, no protective gas, low cost, welding will not produce porosity and other undesirable.
5) The welding process is safe, non-polluting, non-fume, non-radiation, etc.
6) Compared with vacuum brazing liquid-cooled plate, it is cheaper. And there is no risk of runner collapse or adhesion (the main defect of vacuum brazing)
7) It has almost no potential difference because the overall material is basically the same after welding. The cold plate can also be treated with more surface options such as chromate, conductive oxidation, anode, nickel plating, etc.
8) It is more flexible in dealing with complex flow paths and can be free from the limits of Copper tube bending
Ⅴ）Structure and process flow of Friction Stir Welding cooling plate
In general due to the high thermal conductivity of copper and aluminum, stirring friction welding liquid cold plate from aluminum and copper two materials processed (cold plate can only be a material, all copper or all
aluminum, copper and aluminum composite stirring friction welding process is still under development), which all aluminum cooling plate due to the lighter density of aluminum is more commonly used.
1) The welding area is the type of large plane: the sample stage through CNC processing base and cover, and then Friction Stir Welding welding seal; mass production stage base through forging or die-casting process processing, cover through the stamping process, and then Friction Stir Welding welding seal.
2）Type of welding area on the side: sample stage by CNC machining base and cover, then Friction Stir Welding welding seal; mass production stage base by extrusion process processing, cover by stamping process, then Friction Stir Welding welding seal.
Regardless of how the structure of the stirring friction welding liquid-cooled plate changes, its processing process is probably as follows: processing cover and base semi-finished products - cleaning - stirring friction welding - ultrasonic detection of welding defects - leakage test - CNC processing - flushing flow channel - leakage test - thermal resistance and pressure drop test - cleaning - packaging
Ⅵ）The challenges of Friction Stir Welding liquid-cooled plates1）Weight and cost constraints: The product structure needs to be optimized for the product environment, increasing the heat flux density (W/m²) and using lightweight materials (e.g. aluminum) as much as possible.
2) Thermal and mechanical constraints: Cold plate runners and flatness must be optimized to ensure perfect contact with the electronics and maximum contact area, and the exit holes of the friction stir welding head need to be cleverly positioned to reduce processing steps.
3) Pressure drop limitation of the cold plate: Pressure drop has a direct impact on the energy efficiency of the system (pump consumption) and the cover thickness of the cold plate; a low pressure drop allows the use of smaller pumps and thinner cover plates.
4) Coolant and material compatibility restrictions: a high degree of compatibility between the material and coolant is essential.
5) The above conditions limit the operation of liquid cooling systems are interrelated and need to be considered in the design process.
Ⅶ）Quality control of Friction Stir Welding cold plate
Six major testing technologies ensure the perfect quality of the liquid cold plate:
1）Structure test: Detect the mechanical dimension of cold plate by height gauge and CMM equipment to ensure it meets customer requirements.
2）Welding defect test: detect whether the cold plate has welding defects through ultrasonic water testing test machine and pick out the defective products
Cross-section of welding effect detected by ultrasonic
3）Heat dissipation performance test: the thermal resistance and pressure drop parameters of the cold plate are tested by the thermal resistance testing machine to ensure compliance with customer requirements
4）Leakage test: fill the closed cold plate with air, the pressure of filling air is 1.5-2 times the operating pressure of the cold plate liquid cooling system, put the cold plate into the water, observe whether there are bubbles coming out of the cold plate, there are bubbles coming out of the cold plate is defective, this is the most basic and important reliability test of the cold plate, need 100% testing.
5）Burst test: High-pressure water is introduced into the channels of the liquid-cooled plate to measure the crack resistance of the cover.
6）Visual inspection: check by industrial endoscope to determine whether there are aluminum chips, dirt, impurities, etc. inside the flow channel of the liquid cold plate。
Ⅶ）Services and Capabilities
|Product maximum size||≤3000*1000*800MM|
|surface treatment||Degreasing, anode, powder spraying, oil spraying, baking paint, electroplating, passivation|
|maximum working pressure||0.2-2.1Mpa|
|Common coolant||Ethylene glycol solution, propylene glycol solution, pure water|
|Coolant temperature difference between inlet and outlet||0.5-8.5℃|
|Inlet and outlet pressure drop||0.001-0.05Mpa|
|surface temperature rise||5-20℃|
|cooling power consumption||0.1-50KW|