When you see a heat sink as precise as comb teeth in an electronic device, you may not think that its peak performance was determined long before the blade touched the metal. Why are big manufacturers willing to spend a lot of money on material pretreatment? Because this step can directly upgrade the heat sink: cutting aluminum saves 20% of effort, copper heat sinks can be used for 3 more years, and even 12 cm high heat sinks can be cut in one go. This article introduces how to "massage and loosen bones" of metal through scientific means, so that hard metal can be obediently transformed into a perfect heat sink.

1-Why is pretreatment the "invisible engine" of the skived heatsink?

a. Manufacturing challenges of high-precision heat sinks

· Residual stress concentration: The residual stress from the rolling or casting process of the raw materials is released during skiving, causing the substrate to warp.

· Material softening: Aluminum, copper and other materials soften locally due to temperature rise (aluminum 40-60℃, copper 80-120℃) during the cutting process, causing the tooth to collapse or increase burrs.

· Surface oxidation: Copper is easily oxidized in the air to form a CuO layer (high hardness and high brittleness), which aggravates tool wear and shortens tool life.

b. Pretreatment - the key bridge from "metal raw materials" to "precision tooth slices"

· Material performance optimization, recrystallization annealing of aluminum and copper materials respectively, eliminates the residual stress generated during the rolling process, and the uniformity of material hardness can be significantly improved.

·Surface state control, using chemical cleaning to remove the oxide layer on the surface of the material, such as copper can be pickled with 10% HNO₃, and the surface roughness can be reduced to 0.4μm after treatment, effectively reducing tool adhesion; or passivation treatment of aluminum, such as anodizing aluminum to form a 5-10μm thick Al2O3 film to prevent secondary oxidation during processing.

c. How does pretreatment technology improve processing efficiency?

·Shorten the processing cycle, the cutting resistance of the material is reduced after pretreatment, allowing for increased feed speed.

·Reduce rework rate: Stress pre-release greatly improves the flatness pass rate of the substrate, eliminating the secondary correction process.

2-The foundation of pretreatment technology: the integration of material science and technology

The core of pretreatment technology is to customize the process logic based on material properties to solve the inherent contradictions of high thermal conductivity materials such as aluminum and copper in gear skiving.

a.Material properties determine pretreatment logic

·Pretreatment of aluminum materials: annealing at 300–350℃×2h can eliminate rolling stress and improve hardness uniformity by 40%; surface treatment can be selected by anodizing to generate 5–10μm Al₂O₃ film or chemical passivation (chromate treatment) to inhibit oxidation during processing.

·Pretreatment of copper materials: annealing at 500–600℃×1h can soften the material, reduce hardness from 80HB to 45HB, and reduce cutting force by 30%; pickling uses 10% HNO₃ solution to remove the oxide layer. When the CuO thickness exceeds 1μm, the tool wear rate will increase by 50%.

b. Core contradiction: Processing paradox of high thermal conductivity materials

·Contradiction point: high thermal conductivity (such as 380 W/m·K for copper) is the core advantage of the heat sink. High thermal conductivity causes cutting heat to be quickly transferred to the tool, accelerating wear (the tool life of copper processing is only 1/3 of that of aluminum).

Pretreatment scheme, balance between thermal conductivity and machinability, such as low-temperature pretreatment of copper materials to reduce cutting temperature rise or gradient material design; oxide layer management, such as retaining the dense Al2O3 film of aluminum materials to reduce friction; coating the copper materials with benzotriazole oil film after pickling to block secondary oxidation.

3-Core pretreatment methods

a. Mechanical pretreatment: "paving the way" for processing

Surface cleaning (sandblasting/polishing), removing oxide layers, oil stains and burrs, improving surface roughness (Ra value), enhancing coating adhesion or subsequent pickling effect.

b. Chemical pretreatment: activating material surface activity

Through physical cleaning (decontamination), chemical modification (conversion film formation) and surface performance improvement, the material surface is transformed from an inert state to a highly active state. The core lies in balancing surface roughness, chemical functional group density and corrosion resistance, thereby providing an ideal substrate for subsequent processes.

c. Heat treatment: reshaping the material microstructure

By precisely controlling the heating, insulation and cooling processes of the material, the microstructure is reorganized and optimized. The core lies in using thermal activation mechanisms to drive atomic diffusion, phase change and defect reorganization, thereby giving the material new performance characteristics.

d. Composition control: full process management from smelting to molding

Composition control is the core technology of material manufacturing. Through the selection of raw materials, precise smelting control and molding parameter optimization, combined with digital detection, fine control of fluctuations, and improved performance.

4-Aluminum vs. Copper: Differentiated Pretreatment Strategies

Due to the significant differences in the physical and chemical properties of aluminum and copper, pretreatment strategies need to be designed specifically to solve their respective processing pain points.

5-How does pretreatment become an efficiency "amplifier"?

a. Collaboration with skiving processing

· Reduce tool wear: After pretreatment, the residual hard oxide on the surface is reduced, the tool life of the skiving tool is extended, and the chipping rate of high-density fins pieces is reduced.

· Improve processing accuracy: Sandblasting pretreatment eliminates material internal stress, reduces the tooth height error from ±0.5mm to ±0.1mm, and meets the requirements of high-multiple teeth (tooth height/substrate thickness ≥10).

b. Collaboration with surface treatment

· Enhance coating adhesion: After passivation pretreatment, the coating adhesion test pass rate can be significantly improved.

· Reduce contact thermal resistance: Pretreatment forms a uniform microporous structure, which reduces the thermal resistance of the radiator and heat pipe welding interface by 15%-20%.

c. Collaboration with surface CNC processing

· Reduce secondary processing defects: After chemical cleaning to remove oil stains, the burr rate of CNC milling aluminum is reduced by 60%, and the tapping and sliding defects are reduced by 50%.

d. Effect of pretreatment on production efficiency

· Improved yield rate: By optimizing the chemical and mechanical pretreatment processes, the yield rate of skived heatsink and CNC processing has been significantly improved, and product quality has been guaranteed.

· Shortened processing cycle: After pretreatment, aluminum processing does not require separate deburring, and the processing time of a single piece is greatly shortened. The processing speed of the automated sandblasting line is increased, and production efficiency is significantly improved.

· Reduced energy consumption and costs: Mechanical pretreatment is used instead of chemical pickling, and processing energy consumption is reduced. After pretreatment, the hardness of the material is reduced, the mold loss is reduced, and the production cost is effectively reduced.

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