I. Structural Premise
A stamped liquid cold plate consists of a stamped channel plate with grooved flow channels and a smooth flat cover plate. Sealing welds are only arranged along the peripheral bonding surfaces, and no welding is required inside the flow channel cavity. The function of NOCOLOK flux is to remove aluminum oxide films at high temperatures and facilitate wetting and spreading of Al-Si brazing filler metal. Three flux spraying schemes are available: spraying the channel plate only, spraying the flat plate only, and spraying both plates.
II. Scheme 1: Spraying the channel plate only (Mainstream Mass Production Solution in the Industry)
Advantages
- Optimal internal cavity cleanliness Masking tooling covers the channel grooves, and flux is only applied on the peripheral sealing edges. Hardly any flux is squeezed into the cooling channels, resulting in minimal residue inside the cavity after brazing. This simplifies cleaning procedures, meets strict cleanliness acceptance standards for computing power and energy storage products, and prevents microchannel blockage.
- Low flux consumption and reduced production costs Flux is only sprayed on the peripheral frame, cutting flux consumption by 40%–60% compared with dual-plate spraying, delivering significant long-term mass production cost savings.
- Stable brazing wetting performance Stamped forming leaves heavy tensile oxide films and residual lubricant on the channel plate surface. Targeted flux application effectively removes oxide layers. During plate lamination and pressing, capillary action evenly distributes flux across the upper and lower bonding gaps, ensuring sufficient weld wetting and reducing cold solder joints and micro-leakage risks.
- Low defect risk Eliminates flux crystal residue inside channels, preventing after-sales issues such as coolant corrosion, pipeline blockage and impurity precipitation, and improving the first-pass yield rate of helium leak testing.
- Compatible with continuous NOCOLOK atmosphere furnaces Thin single-frame flux coating minimizes fluoride volatilization inside the furnace, reduces furnace contamination and extends furnace maintenance intervals.
Disadvantages
- Masking tooling is required, increasing upfront equipment investment for tool fabrication and loading/unloading processes.
- For large-size thick plates or products with large assembly gaps, insufficient flux supply from the single plate may lead to poor wetting at weld corners.
- When using high-magnesium aluminum alloys, single-sided flux provides limited oxide film removal capacity, occasionally causing partial incomplete brazing.
III. Scheme 2: Spraying the flat plate only
Advantages
- The flat plate features a smooth, even surface without concave-convex grooves, requiring simple spraying tooling without complex masking, and enabling easy equipment commissioning.
- Flat plates have consistent incoming material conditions free of stamping deformation, allowing easier control of coating uniformity.
Disadvantages
- Failure to pretreat heavy oxide layers on the channel plate The stamped channel plate carries thick oxide films on its uneven surfaces. Reliance solely on limited flux penetration from the flat plate side after lamination fails to fully remove oxide films, frequently causing cold solder joints, discontinuous welds and micro-leakage detected by helium testing.
- Massive flux squeeze into flow channels after pressing Full-surface flux on the flat plate is extruded into the grooves during lamination, causing severe residue accumulation inside the cavity. Cleaning workload doubles, microchannels are prone to blockage, and such products are directly rejected by high-end customers.
- Uneven flux distribution at weld edges Insufficient flux supply at sealing corners and narrow edges leads to inconsistent brazing quality and high batch defect rates.
- Incompatible with high-magnesium aluminum sheets due to severely insufficient oxide film removal capability.
IV. Scheme 3: Dual-plate spraying (channel plate + flat plate) – Low-End Simplified Process Being Phased Out
Advantages
- No precision masking tooling needed, streamlining production workflows and suitable for small-batch low-end cold plates.
- Flux applied on both sides of welds thoroughly eliminates oxide films, delivering optimal brazing wetting for large-gap assemblies and high-magnesium sheets with rare cold solder joints.
Disadvantages
- Worst internal cavity cleanliness Superimposed flux from two plates is squeezed into flow channels during lamination, leaving heavy residue buildup inside cavities. Multiple additional cleaning steps including acid washing and ultrasonic cleaning are mandatory, drastically raising production costs and labor hours.
- Doubled flux consumption leads to high consumable costs.
