Complete Guide to Welding Processes for Heat Sink
Welding is a crucial part of heat sink manufacturing, as it directly determines the structural strength, thermal conductivity efficiency, and service life of the heat sink. Whether it's the battery liquid cooling plate for new energy vehicles or the CPU radiator for computers, the connection process behind them all relies on welding.
Below, I will introduce six of the most common heat sink welding processes to help you fully understand their principles, advantages, and applicable scenarios.
1. Vacuum brazing
Principle:
Place the assembled workpiece into a vacuum furnace, extract air to reach a high vacuum state, and then heat it to melt the brazing material and fill the weld gap under capillary action. After cooling, a firm connection is formed.
Features:
* Welding is carried out in a high vacuum environment (with a vacuum degree of up to 10 ⁻ Pa level) without the need for chemical flux, and the weld seam is very clean.
* After melting, the brazing material can fill complex narrow channels, making it very suitable for heat sinks with multi-channel and multi-layer board structures.
* Multiple components can be welded at once, resulting in high efficiency in batch production in the same furnace.
Advantages:
* The overall heating is uniform, with low thermal stress and minimal welding deformation
* No need for soldering flux, the product has good corrosion resistance
* High welding yield and dense weld seam
Disadvantages:
* High equipment investment and difficult process operation
* High energy consumption and long single furnace cycle
Typical applications: new energy vehicle battery liquid cooling plate, high-end server heatsink, aerospace heat exchanger, etc.
Summary: Vacuum brazing is suitable for high-precision, high pressure resistant, and large-scale heat sink products, and is the mainstream choice in the fields of new energy and high-end electronics
2. Argon arc welding
Principle: Using a tungsten electrode as an electrode, an arc is generated under argon protection to locally melt the base material and form a weld seam. It belongs to a type of fusion welding.
Features:
* Argon, as an inert gas, can effectively isolate air and prevent oxidation during the welding process
* The weld joint is smooth and dense, without defects such as slag inclusion or porosity
Advantages:
* High welding strength and good compressive strength
* Suitable for welding materials such as stainless steel and aluminum alloy
* Flexible operation, suitable for workpieces of various shapes
Disadvantages:
* Welding heat input is large, and thin-walled parts are prone to deformation
* The current carrying capacity of tungsten electrode is limited, and it is easy to cause tungsten electrode melting and evaporation under high current, which may contaminate the weld seam.
* The cost of argon gas is relatively high
Typical applications: welding of industrial heat sinks, stainless steel heatsink cores, etc.
Summary: Argon arc welding has high strength but significant thermal impact, making it suitable for medium thick plate heatsink radiators that require high strength and are less sensitive to deformation.
3. Laser welding
Principle: Using a high-energy density laser beam to irradiate the surface of the workpiece, converting light energy into heat energy, achieving local rapid melting and connection.
Features:
* The laser beam can be focused to the micrometer level, with extremely high energy density and fast welding speed
* The heat affected zone is very small (usually less than 1mm) and hardly affects the properties of surrounding materials
Advantages:
* High welding accuracy, capable of achieving ultra-fine welds (micrometer level), suitable for welding ultra-thin cavities.
* Excellent sealing performance and beautiful weld seam
* Easy to automate integration, suitable for large-scale production
* Suitable for welding precision microdevices
Disadvantages:
* High equipment investment cost
* Penetration power is not as good as electron beam welding.
* High precision requirements for welding workpiece assembly
Typical applications: High end heat dissipation devices such as VC heat dissipation plate heat sinks, consumer electronics micro heat sinks, server heat dissipation modules, etc.
Summary: Laser welding has high precision and minimal thermal impact, and is currently the mainstream connection technology for high-end compact heat sinks.
4. High frequency welding
Principle: By utilizing the skin effect and proximity effect of high-frequency current (usually 10-500kHz), the metal is instantly heated locally to a molten or plastic state, and welding is completed under pressure.
Features:
* High frequency induction heating has a fast heating speed, and can heat up to the silver brazing temperature (about 720 ℃) in 3-8 seconds.
* Combined with customized induction coils, precise local heating can be achieved, and the heat affected zone can be controlled within 3mm
Advantages:
* Fast welding speed and high production efficiency
* Localized heating, small heat affected zone, minimal impact on surrounding materials
* Suitable for thin-walled pipe fittings and continuous welding production.
Disadvantages:
* High equipment investment
* Induction coils need to be customized for specific products, and different products require different coils
* There are certain restrictions on the shape of the workpiece
Typical applications: high-frequency welded finned tube heatsink, etc.
Summary: High frequency welding has fast speed and precise local heating, making it particularly suitable for continuous production of heat dissipation components such as finned tubes.
5. Friction Stir Welding (FSW)
Principle: By using a high-speed rotating mixing head to insert into the joint of the workpiece, heat is generated through friction to cause plastic deformation of the material. Under the compression of the mixing head, a dense solid-phase weld is formed, and the base material does not melt.
Features:
* Belonging to solid-state welding, the base material does not melt during the welding process, avoiding melting welding defects such as pores and cracks
* The grain size of the weld seam is small, and its performance is close to or even better than that of the base metal
Advantages:
* High welding quality, good weld density, outstanding fatigue and corrosion resistance performance
* No need for welding wire, no need for protective gas, no need to remove oxide film before welding
* Energy saving and environmentally friendly, without smoke and dust pollution
* Controllable deformation amount, capable of achieving small margin flat processing
Disadvantages:
* Can only perform linear welding (unidirectional straight seam), cannot weld complex curves
* The requirements for fixtures and jigs are high, and the investment cost is high.
* The endpoint of the weld seam will leave process holes that require additional processing.
* Slow welding speed and relatively low production efficiency
Typical applications: high-power water-cooled plates, wind power converter heatsinks radiators, IGBT heat sinks, laser heatsinks, motor controllers, etc.
Summary: Friction stir welding has high weld quality, does not require filling materials, and is suitable for water-cooled plates and power electronic heat sinks radiators with high reliability requirements.
6. Soldering
Principle: Using tin based brazing material with a melting point lower than the base metal (180-280 ℃), the brazing material is melted and filled in the weld gap by heating, and then cooled to form a connection.
Features:
* The welding temperature is relatively low, much lower than brazing and melting welding, and the deformation of the heat sink is small. The mechanical properties of the substrate are not affected.
* The thermal conductivity of tin solder is about 35-70 W/(m · K).
Advantages:
* Low welding temperature, low thermal stress, suitable for thin-walled and precision structures
* Relatively simple operation and low cost
* Suitable for small-scale production and maintenance scenarios
Disadvantages:
* The thermal conductivity of welded joints is low, and there is a problem of interface thermal resistance
* Easy to have air holes, not suitable for large heatsinks radiators.
* Solder may soften in high temperature environments, resulting in poor long-term reliability
Typical applications: traditional electronic heat sinks (small), LED lights, heat pipe embedded heat sinks, etc.
Summary: Soldering temperature is low and deformation is small, suitable for the production of small-sized and low-cost heat sinks, but not suitable for large-sized and high reliability scenarios.
7. How to choose the appropriate welding process?
When choosing a welding process, it is recommended to consider the following dimensions comprehensively:
1. Product accuracy requirements: Laser welding is preferred for precision micro heat sinks; Vacuum brazing or friction stir welding can be considered for medium and large heat sinks radiators.
2. Material combination: Wide range of welding options for the same metal; Friction stir welding is recommended for copper aluminum dissimilar metal welding.
3. Production batch: For large-scale standardized products, priority is given to vacuum brazing or tunnel furnace welding; Small batch customized products can consider argon arc welding or laser welding.
4. Cost budget: High end processes (laser welding, vacuum brazing) are suitable for high value-added products; Soldering and argon arc welding are suitable for cost sensitive products.
5. Structural complexity: prioritize vacuum brazing or soldering for complex flow channels and multi-layer structures; Simple linear welds can consider friction stir welding.
8. Conclusion
Different welding processes have their own advantages, there is no absolute "best", only "most suitable". If your product requires extremely high precision and heat dissipation efficiency, laser welding and vacuum brazing are worth prioritizing; If you pursue high reliability and weld quality, friction stir welding is a good direction.
AWIND has accumulated rich experience in heat sinks radiator welding technology. Whether it is vacuum brazing, friction stir welding or laser welding, we can provide one-stop services from process selection to sample production and mass production according to your specific needs.
If you are struggling with the welding process selection for the heatsinks, please feel free to contact us at any time to discuss the most suitable solution for you.
