Three Components, Three Thermal Jobs
A liquid cold plate, heat spreader, and heat sink may appear similar because each uses conductive metal and a controlled contact surface. Their functions are different. A cold plate transfers heat into flowing coolant. A heat spreader redistributes concentrated heat across a larger area. A heat sink transfers heat to moving air through fins or pins.
| Component | Main function | Typical manufacturing focus |
|---|---|---|
| Liquid cold plate | Moves heat into a coolant circuit | Flow channels, sealing, contact face, ports, joining, leak testing |
| Heat spreader | Reduces hot spots by lateral conduction | Thickness, flatness, parallelism, surface finish, plating, mounting |
| Heat sink | Transfers heat to air | Base contact, fin geometry, airflow, mounting, surface treatment |
Choose From the Complete Thermal Path
Component selection begins with heat load and heat flux, but it also depends on allowable device temperature, contact area, thermal interface material, clamp load, coolant or airflow, pressure drop, available volume, mass, noise, reliability, and serviceability.
A heat spreader may sit between a package and a cold plate. A hybrid server can use cold plates on accelerators and heat sinks on lower-power components. Avoid selecting hardware from a single conductivity value without modeling the full path from silicon to facility heat rejection.
Liquid Cold Plate Design
Cold plates combine a thermal interface with an internal pressure boundary. The design must balance contact-face thickness, channel placement, flow distribution, pressure drop, material, sealing, joining, cleanliness, and testability.
CNC machining supports prototypes and complex custom geometry. Review our CNC machined cold plate guide and microchannel machining guide for detailed process planning.
Heat Spreader Design and Machining
A heat spreader needs predictable contact on both sides. Flatness, thickness, parallelism, roughness, plating thickness, edge condition, mounting-hole position, and material homogeneity can affect performance and assembly.
- Define functional datums around the mating surfaces and mounting pattern.
- Specify surface roughness only where it supports the selected interface material.
- State whether dimensions apply before or after nickel plating or another finish.
- Control handling and packaging to prevent scratches, dents, oxidation, or contamination.
Heat Sink Manufacturing Considerations
Heat sinks can be extruded, skived, bonded, forged, cast, or CNC machined. CNC machining is useful for integrated mounting features, prototypes, low quantities, complex bases, and designs that combine channels or enclosures with fins.
Fin height, thickness, pitch, direction, base thickness, bypass airflow, fan curve, orientation, and surface finish should come from the thermal and mechanical design. Tall thin fins require realistic cutter access or an alternate manufacturing process.
Aluminum, Copper, and Hybrid Structures
Aluminum provides low mass, useful conductivity, good machinability, and several finishing options. Copper provides higher conductivity and better spreading for concentrated heat but adds mass, material cost, and machining considerations. Hybrid structures can localize copper near the heat source while using aluminum elsewhere, but joining and galvanic compatibility become critical.
See our detailed aluminum versus copper comparison.
Contact Interfaces and Mounting
Thermal performance depends on real contact rather than nominal CAD contact. Package bow, plate flatness, surface texture, interface material thickness, fastener pattern, spring load, tolerance stack, and assembly sequence all influence contact pressure.
Do not impose extreme flatness without considering measurement method, part size, unclamped condition, temperature, joining, coating, and practical assembly benefit. Define requirements from thermal validation and package specifications.
Inspection and Validation
- Material identity and traceability
- Contact-face flatness, profile, roughness, and damage limits
- Thickness, parallelism, mounting pattern, and interface location
- Channel, seal, port, and leak integrity for cold plates
- Fin geometry and base relationship for heat sinks
- Coating or plating condition, cleanliness, and protected packaging
Thermal Hardware RFQ Checklist
- Component type, heat source, heat load, heat flux, and allowable temperature
- 3D model, dimensioned drawing, package specification, and assembly context
- Material, finish, interface material, mounting and clamp requirements
- Coolant and pressure data for cold plates or airflow data for heat sinks
- Inspection, thermal, leak, cleanliness, documentation, and packaging needs
- Prototype and production quantities plus target delivery
Frequently Asked Questions
Is a heat spreader the same as a cold plate?
No. A heat spreader redistributes heat through conduction; a cold plate includes a liquid path that carries heat away.
Is a heat sink still used in a liquid-cooled server?
Often yes, depending on architecture. Some devices remain air cooled while high-heat components use direct-to-chip liquid cooling.
Can all three be CNC machined?
CNC machining can produce each type, especially for prototypes and complex custom parts, although extrusion, skiving, bonding, or other routes may be better for some fin structures and volumes.