Liquid cooling plates

Definition

A liquid cooling plate (also called a cold plate, liquid cold plate, or cooling plate) is a flat, thermally conductive component with internal fluid passages or embedded tubes that circulates a coolant to remove heat from attached heat-generating devices. It functions as a compact liquid-cooled heat exchanger, transferring heat from components such as battery cells, power electronics, motors, or CPUs/GPUs into a thermal management loop for rejection at a radiator or chiller.

How it works

  • Heat flows by conduction from the device into the plate, then by convection from the plate surfaces into the moving coolant. The warmed coolant carries heat to a secondary heat exchanger for dissipation.
  • Thermal interfaces (grease, pads, phase-change materials, or bonded/brazed joints) minimize contact resistance between the device and the plate.
  • The plate may cool on one or both sides and can be integrated as a base plate under modules or as side plates between elements (for example, between battery cells).

Key technical characteristics

  • Internal flow structures: serpentine channels, parallel microchannels, manifold–microchannel networks, pin-fin or dimpled cavities, embedded tube-in-plate designs, extruded multichannel profiles, or jet-impingement features to increase local heat transfer.
  • Performance metrics: thermal resistance (K/W), allowable or uniformity temperature rise (often targeting less than 2–5 °C spread in battery packs), heat flux capacity (commonly 10–100+ W/cm² for high-power electronics), coolant-side heat transfer coefficient, and pumping power/pressure drop.
  • Hydraulic behavior: pressure drop versus flow rate, flow distribution uniformity across multiple parallel paths, avoidance of maldistribution, gas entrapment, and cavitation.
  • Interface and mounting: surface flatness and planarity, bolt patterns or clamps, compliant or gap-filling TIMs, and provisions for double-sided cooling when needed.
  • Coolants: water–glycol mixtures in automotive and industrial loops; dielectric fluids (PAO, engineered fluorocarbons, silicone oils) where electrical isolation is required; inhibitors and biocides to control corrosion and biological growth.
  • Reliability factors: galvanic corrosion management, erosion at high velocities, elastomer compatibility, freeze/boil protection, leak integrity, fatigue under vibration and thermal cycling, and cleanliness to prevent channel blockage.

Applications and relevance

  • Electric vehicles: battery cooling plates beneath or between prismatic/pouch cells and in cell-to-pack designs to keep cells within optimal ranges (typically about 15–35 °C), support fast charging, and maintain tight temperature uniformity; cooling for inverters, onboard chargers, DC/DC converters, and e-axles to sustain high power density and efficiency.
  • Electronics and computing: direct-to-module or baseplate cooling for power modules, CPUs/GPUs, telecom and data center hardware where air cooling is insufficient.
  • Industrial and energy systems: drives, traction in rail, renewable energy inverters, lasers, medical imaging, and test equipment requiring compact, high-performance heat removal.
  • System integration benefits: denser packaging, lower noise than forced air, improved efficiency and component life, and compatibility with heat-pump or waste-heat recovery in vehicle and stationary systems.
  • Safety and durability: tighter thermal control reduces lithium plating risk during fast charge, helps limit propagation in thermal events by maintaining lower baseline temperatures, and reduces thermo-mechanical stress in electronics.

Materials

  • Aluminum alloys (common in automotive for high conductivity, low mass, good formability, and vacuum-brazing compatibility).
  • Copper and copper alloys (very high conductivity, often used for compact electronics; higher mass and cost).
  • Stainless steel or titanium (strength and corrosion resistance in aggressive environments or for embedded tubing).
  • Surface treatments and coatings (e.g., nickel plating, anodizing) to reduce corrosion; polymer housings or inserts in some dielectric-fluid systems.
  • Seals and gaskets: EPDM, FKM, or silicone elastomers selected for coolant compatibility and temperature range.

Manufacturing methods

  • Machined channel plates closed by a cover plate, joined by vacuum brazing, diffusion bonding, laser welding, or soldering.
  • Plate-fin or corrugated cores sandwiched and vacuum-brazed to create high surface-area flow passages.
  • Tube-in-plate constructions with embedded copper or stainless-steel serpentine tubes.
  • Aluminum extrusions with integrated channels, cut to length, end-sealed, and machined for interfaces.
  • Friction stir welding (FSW) for joining plate halves with low distortion and high joint quality.
  • Metal additive manufacturing (laser powder bed fusion or similar) to realize complex, conformal passages, turbulence promoters, and topology-optimized flow fields.
  • Sheet stamping or hydroforming for manifolds and covers, then joined by brazing or welding.
  • Surface enhancements (pin fins, microfins, dimples, chemically etched textures) to increase heat transfer coefficients.

Design and validation considerations

  • Corrosion control via compatible material pairings, coolant inhibitors, and protective coatings; adherence to OEM/industry coolant specifications.
  • Cleanliness, filtration, and degassing to prevent fouling, blockage, and gas pockets; provisions for bleed ports and filters.
  • Structural integrity appropriate to mounting, crash, or vibration environments; validation by pressure, burst, leak (including helium), thermal shock, and thermal cycle testing.
  • Flow balancing across multiple plates or zones; manifold design to minimize maldistribution.
  • Instrumentation and serviceability: ports for pressure/temperature sensing, flow meters, and leak detection strategies.
  • Integration with the thermal loop (pump, radiator/chiller, valves, expansion tank) and controls to manage temperature setpoints, flow rates, and energy use.

Synonyms and related terms

  • Synonyms: cold plate, liquid cold plate, cooling plate.
  • Related terms: battery cooling plate, microchannel cold plate, jet-impingement plate, liquid-cooled heat sink, cooling jacket (a jacket is integrated into a housing rather than a stand-alone plate), thermal interface material (TIM), thermal management system (TMS), radiator, chiller.

Notes on selection

Selecting a liquid cooling plate involves balancing heat flux and temperature uniformity targets, allowable pressure drop and pumping power, coolant type and corrosion environment, package and weight constraints, manufacturing cost and scalability, and reliability requirements over the intended life cycle.

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