Brazing of aluminum alloy cold plate
The application and processing status of liquid cooled radiators in power and electronics industries, high-power devices are prone to heat burning or overheating resulting in performance instability and other problems, often need to be equipped with radiators for its cooling.
Traditional radiators are mostly made of copper, aluminum and their alloys. The joint process is usually brazing, and some parts are welded. In order to meet the requirements of welding deformation and surface assembly, the surface after welding needs to have certain machining allowance.
It is difficult to use conventional welding or brazing if the sealing is good and has certain compressive strength. It is easy for solder plug to block the channel or solder leakage to appear weak joint welding defects.
Water-cooled aluminum alloy plate (friction stir welding process)
Product design requirements: 2MPa for 15 minutes without leakage;
Test after FSW welding: 4MPa lasts 20 minutes without leakage, greatly exceeding the design requirements.
Through theoretical calculation, the effective welding depth of 1mm FSW can withstand the internal pressure above 10MPa for the watercourse structure within 15mm wide cover plate.
All aluminum alloy products involved in connection can be connected by friction stir welding process. The aluminum alloy welds welded by the friction stir welding process are recrystallized under the forging pressure of the mixing head after the solid phase connection method is used to directly plasticize the base material without cutting the groove and filling the wire. The weld grain is less than one order of magnitude of the base material, and the various properties of the weld are close to the base material. Perfect realization of aluminum alloy connection.
Technical features of friction stir welding
Friction stir welding is aimed at aluminum alloy, copper alloy, magnesium alloy, titanium alloy and other non-ferrous metal joint process. Technical features of friction stir welding include:
1. Welding the base material directly, without cutting the groove or filling the wire;
2. It is not necessary to remove the oxide layer of materials before welding, and no vacuum and shielding gas is required during welding. No burning loss of elements after welding.
3. The grain structure of weld is forged. Morphology isotropy. Each performance close to the parent material
Aluminum alloy cold plate
Requirements for high-end electronic products, heat dissipation structure footprint as small as possible, the weight of the lighter the better, the more reliable performance, the better, air cooling fin radiator obviously unable to meet this requirement, the designer to gradually shift from air cooling heat dissipation structure of the water surface plate heat dissipation structure, the solution is studied experimentally JiaGongShui involves what process can meet the design intent.
There are three options:
First, heat pipe heat dissipation;
Second, embedded copper pipe in aluminum plate forms channel heat dissipation;
Three is a cold plate, directly in the aluminum plate milling groove, cover plate welding to form a channel. The analysis of the above three design schemes of water-cooled plate is as follows:
Heat pipe heat dissipation: generally, self-heat dissipation cycle is formed in the vacuum pipe body. However, this scheme cannot be used as a large cold plate, which is inconvenient for maintenance at the same time.
Buried pipe heat dissipation: the fabrication cost of buried pipe heat dissipation is relatively low. Milling out the channel inside the aluminum plate and burying copper pipe into the channel to form an airtight channel. The copper tube is filled with a gel between the aluminum plate. The scheme can meet the requirement of heat dissipation, but the disadvantage is that large heat dissipation interval cannot be formed locally, and the heat dissipation requirements of some structural parts cannot be met.
Integral cold plate: direct groove in the aluminum plate, plate welding forming channel, this needs to choose a kind of welding process on base plate and the cover plate sealing, preliminary selection of brazing process, brazing solder are the shortcomings of easy to loss, loss of solder may clog waterways, loss of the position of the solder will appear the phenomenon of not welded, led to the channel leakage. The yield rate is about 80%, depending on the degree of proficiency, the sense of responsibility, the consistency of solder, and the temperature in the furnace. Because of too many uncertain factors, it is not reliable to use this process to weld liquid cold plates, especially for the important structural parts.
The electronic radiator sought for the friction stir welding technology to make the aluminum alloy water cooled board because of the unreliable brazing technology, and the friction stir welding technology showed an incomparable advantage in this product:
1. Under normal temperature and normal conditions, there is no need for groove opening, packing, vacuum extraction and gas protection;
2. Pleasant working environment, no noise, arc or radiation during welding;
3. High yield, nc operation, not dependent on manual proficiency;
4. High efficiency, 100% yield with unchanged materials and correct parameters.