Cold plates are critical components in liquid-cooled battery thermal management systems, designed to efficiently dissipate heat generated by battery cells during operation. Their manufacturing processes involve precise engineering to ensure optimal thermal performance, durability, and integration within battery packs. This article explores the materials, design considerations, fabrication methods, and industry standards for cold plate manufacturing, along with a comparison of active and passive liquid cooling approaches.

Materials used in cold plate construction are selected based on thermal conductivity, weight, and corrosion resistance. Aluminum is the most common material due to its high thermal conductivity (approximately 200-250 W/m·K), lightweight properties, and cost-effectiveness. Aluminum alloys such as 6061 and 6063 are frequently used for their balance of strength and manufacturability. Copper offers even higher thermal conductivity (around 400 W/m·K) but is heavier and more expensive, limiting its use to high-performance applications where weight is less critical. Composite materials, such as graphite-aluminum or metal-matrix composites, are emerging as alternatives, offering tailored thermal properties and reduced weight. The choice of material impacts the cold plate's heat transfer efficiency, pressure resistance, and compatibility with coolants.

Design considerations for cold plates focus on maximizing heat transfer while minimizing pressure drop and ensuring uniform cooling. Flow channel geometry is a key factor, with common designs including serpentine, parallel, and microchannel configurations. Serpentine channels provide longer coolant paths, enhancing heat absorption but increasing pressure drop. Parallel channels reduce pressure drop but may lead to uneven cooling if not properly balanced. Microchannel designs, with channel widths typically below 1 mm, offer high surface-area-to-volume ratios for improved heat transfer but require precise manufacturing to avoid clogging. Heat transfer efficiency is further influenced by the cold plate's thickness, surface roughness, and the contact area with battery cells. Computational fluid dynamics (CFD) simulations are often employed to optimize these parameters before production.

Fabrication methods for cold plates vary depending on material and design complexity. Traditional techniques include brazing, where two or more metal parts are joined using a filler metal with a lower melting point. Aluminum brazing often employs flux or vacuum furnaces to prevent oxidation, while copper brazing may use silver or phosphorus-based fillers. Machining is another common method, where flow channels are milled or drilled into a solid metal block, though this can be material-intensive. Additive manufacturing, or 3D printing, is gaining traction for its ability to produce intricate channel geometries and reduce material waste. Techniques like selective laser melting (SLM) and direct metal laser sintering (DMLS) enable the creation of lightweight, high-performance cold plates with internal features that are difficult to achieve through conventional methods. However, additive manufacturing can be cost-prohibitive for large-scale production.

Active and passive liquid cooling systems differ in their approach to thermal management. Active cooling relies on external pumps to circulate coolant through cold plates, providing precise temperature control and higher heat dissipation rates. This method is commonly used in electric vehicles and high-power applications where thermal loads are variable and demanding. Passive cooling, on the other hand, uses natural convection or thermosiphoning to move coolant, eliminating the need for pumps but offering lower cooling capacity. Passive systems are simpler and more reliable but are generally suited for low-to-moderate heat loads. Integrating cold plates into battery packs requires careful consideration of space constraints, thermal interface materials (TIMs), and mechanical stability. TIMs such as thermal pads or gels are used to enhance heat transfer between cells and cold plates, while structural supports ensure even pressure distribution and prevent deformation.

Industry standards and performance metrics ensure cold plates meet reliability and safety requirements. Key standards include ISO 19453 for automotive battery thermal management and SAE J2908 for liquid cooling system performance. Performance metrics include thermal resistance (measured in °C/W), which quantifies the cold plate's ability to transfer heat, and pressure drop (measured in kPa or psi), which affects pumping power requirements. Heat transfer coefficients (W/m²·K) and uniformity of temperature distribution are also critical for evaluating cold plate effectiveness. Manufacturers often conduct rigorous testing under simulated operating conditions to validate these metrics before deployment.

In summary, cold plate manufacturing for battery thermal management involves a combination of material selection, advanced design, and precision fabrication to achieve efficient and reliable cooling. Aluminum and copper remain dominant materials, while additive manufacturing opens new possibilities for complex geometries. Active cooling systems offer superior performance for high-demand applications, while passive systems provide simplicity and reliability. Adherence to industry standards ensures cold plates meet the rigorous demands of modern battery systems, contributing to safer and more efficient energy storage solutions.