Copper-Alloy Thermal Management: Microchannel Heat Sinks and TPMS Lattices

  November 4, 2025   7 min read

Copper-Alloy Thermal Management: Microchannel Heat Sinks and TPMS Lattices

High-power electronics, laser optics, and compact propulsion hardware all push heat flux into uncomfortable territory. Copper-alloy additive manufacturing—especially laser powder bed fusion (LPBF)—lets us route coolant where it matters, build high–area density microchannels, and pack triply periodic minimal surface (TPMS) lattices into volumes that were previously un-coolable. This article condenses practical design guidance, materials trade-offs, and verification methods that shorten the path from CAD to a qualified thermal module.

Materials that make thermal design easier

CuCrZr (C18150): conductivity first, with workable strength

CuCrZr offers high thermal/electrical conductivity with useful strength after solution + aging heat treatment. In the heat-treated state, electrical conductivity around ~85% IACS is typical, with processing windows published by multiple machine vendors for LPBF. (EU - EOS Store)

When it shines Heat exchangers, induction coils, cold plates, and microchannel heat sinks that prioritize conductivity and stable properties up to roughly 300–500 °C, depending on duty cycle and load path. Powder, parameter sets, and data sheets are broadly available across the ecosystem. (EOS GmbH)

GRCop-42 (Cu-Cr-Nb): high-temperature, high-heat-flux pedigree

Developed by NASA for regeneratively cooled liquid rocket components, GRCop-42 retains strength at elevated temperature with good creep resistance while maintaining copper-class conductivity. For extreme heat flux and thermal cycling, it’s the alloy of record. (ntrs.nasa.gov)

When it shines Combustion-adjacent hardware, turbine-side liners, and laser heads that see red-hot walls yet demand fast heat spreading to liquid circuits.

Microchannel heat sinks: design patterns that print and perform

1) Channel geometry and print realism

  • Hydraulic diameter (Dh): For single-phase liquid cooling, Dh in the ~0.3–1.5 mm band balances heat transfer and pressure drop for most electronics coolant loops.
  • Minimums you can trust: On modern 1 kW LPBF platforms, stable wall thicknesses ~0.3–0.5 mm and channels ~0.4–0.6 mm are commonly achievable with tuned parameters and build orientation; push below that only after coupon proof. Vendor data confirms 80 µm layers and validated heat-treats for CuCrZr processes. (EOS GmbH)

DFAM note: Favor taller, narrower channels (higher aspect ratio) only if you can control bowing and bridge spans; split a “risky” tall channel into two parallel lanes with an internal rib to keep overhangs printable.

2) Manifolds that avoid maldistribution

Headers should expand area gradually (≤7–10° cone angle) and use progressive slotting so each branch sees similar static pressure. Add pressure-tap bosses for flow tuning during bring-up.

3) Surface roughness: friend and foe

As-built internal roughness raises the Nusselt number (more heat transfer) and the friction factor (more Δp). Plan roughness-sensitive CFD with measured coupons; keep AFM/CT-derived Ra/Rz values in your simulation library. Use abrasive-flow machining, chemical polishing, or thin electroless Ni strike (if corrosion control is mandatory) while tracking the conductivity hit of any coating.

4) Two-phase microchannels: only with discipline

Boiling skyrockets heat transfer, but predicting Δp and critical heat flux across regimes is non-trivial, and literature correlations disagree across sub-regions. If you go there, bound operating maps conservatively and instrument the prototype with wall thermocouples and differential pressure. (engineering.purdue.edu)

5) Sealing strategy and leak-tightness

For integral lids, design a machined cover + diffusion-bond or vacuum braze land with witness grooves. Qualify with helium leak testing and flow-bench characterization across the duty envelope before integrating into a system manifold.

TPMS lattice heat sinks: turning volume into area and mixing

TPMS structures (Gyroid, Diamond, Schwarz, Lidinoid, etc.) deliver enormous surface area and 3D tortuosity that enhances convective mixing at low Reynolds numbers. Recent studies on LPBF lattices report improved thermal performance vs. conventional pin-fin sinks at comparable volume, with unit-cell size and periodicity strongly controlling the trade between heat transfer and pressure drop. (link.springer.com)

Designing TPMS for cooling (the fast checklist)

  • Unit cell vs. Dh: Start with a unit cell ~1–2× the target hydraulic diameter of flow passages; refine after coupon tests.
  • Relative density: 10–30% is a practical window for coolant side; gradient the density near hot spots.
  • Manifold-lattice coupling: Blend a short microchannel plenum into the lattice to distribute flow and prevent bypass.
  • Powder evacuation: Provide accessible purge ports and draft angles so trapped powder doesn’t entomb itself in the lattice.

Hybrid cores: microchannels + TPMS inserts

A high-shear TPMS core inside a microchannel plenum gives you both: predictable header behavior and lattice-driven mixing. This pairing is a sweet spot for topology optimization and generative design tools, where you co-optimize manifold loss and lattice density against thermal targets—then lock the geometry with optimization for additive manufacturing rules (overhangs, escape, supports).

End-to-end workflow that cuts iteration time

  1. Thermal targets → Specify heat flux, allowable ΔT, coolant chemistry, and pressure budget (pump curve).
  2. Concept generation → Explore microchannels, TPMS, or hybrids using lattice structure design and lightweight design heuristics.
  3. Printable abstraction → Apply DfAM (design for additive manufacturing): min ribs, drain paths, overhang control, support removal plans.
  4. Multiphysics simulation → Conjugate heat transfer CFD + structural FEA (including load cases for mounting and brazing).
  5. Parameterized coupons → Vary Dh, roughness, relative density, and lattice periodicity; bench for Nu–Re–Pr maps and Δp.
  6. Process definition → Lock powder, machine, layer thickness, and parameter set (e.g., CuCrZr or GRCop-42 playbooks). (EOS GmbH)
  7. Print, heat treat, finish → Solution + aging for CuCrZr; stress-relief for GRCop-42; optional HIP if your porosity/leak budget demands it.
  8. Verification → Helium leak test, flow bench, thermal bench, and CT where risk concentrates (manifold junctions, thin walls).
  9. Design freeze & documentation → Manufacturing plan, inspection plan, and service notes (coolant inhibitors, filtration, ESD and cleanliness where relevant).

Practical design rules you can drop into a checklist

  • Keep overhangs ≥45° inside channels, or rib them so self-supporting spans stay short.
  • Escape powder: add purge/cleaning ports to lattices and serpentine channels; design for pressure-pulse cleaning.
  • Split headers early: large aspect-ratio plates benefit from distributed headers rather than one big inlet.
  • Measure, don’t assume roughness: feed measured Ra/Rz into CFD; avoid “smooth-wall” guesses.
  • Coatings only when needed: electroless Ni or polymer liners help with corrosion but reduce effective conductivity; run the math.
  • Materials fit-for-use: CuCrZr for conductivity-limited electronics; GRCop-42 for red-hot walls and thermal fatigue. (EU - EOS Store)

Capability snapshot (for quoting and risk reduction)

  • Alloys: CuCrZr (C18150), GRCop-42. (EOS GmbH)
  • Feature scale (typical, proof by coupon): channels ~0.4–0.6 mm; walls ~0.3–0.5 mm; TPMS unit cells ≥0.6 mm. (EOS GmbH)
  • Post-processing: heat treatment, surface finishing (AFM/chemical), diffusion-bond or braze sealing, pressure/leak testing, CT.
  • Applications: laser cold plates, RF loads, power electronics bases, rocket/regenerative liners, compact exchangers for aerospace and energy. (ntrs.nasa.gov)

Request a DfAM review or quote: [email protected]

Frequently asked questions (fast answers)

Can you print pure copper or only alloys?
Both are possible, but for microchannels and TPMS lattices we typically recommend CuCrZr or GRCop-42 for better process stability and mechanical margin; pure copper’s reflectivity and softness raise risk for thin walls.
What’s the smallest microchannel you will quote?
We routinely quote ~0.4–0.6 mm channel widths and ~0.3–0.5 mm walls with coupon validation and orientation control. Sub-0.4 mm is R&D territory and must be proven on test coupons first.
How are channels sealed and verified leak-tight?
Commonly with a machined lid that’s diffusion-bonded or vacuum-brazed. We perform helium leak testing and then flow-bench the part across the expected pressure/temperature window.
Do you support two-phase (boiling) cooling?
Yes for prototypes, but only with guard-banded operating maps and dense instrumentation. Two-phase microchannels demand a careful Δp/CHF validation plan before production release.
Coolant compatibility and corrosion?
For water/glycol loops, use inhibitors and filtration; for DI water, assess copper dissolution risk. If needed, we can apply thin Ni or polymer barrier coatings—with a quantified impact on thermal resistance.

References and further reading

Disclaimer: If you choose to implement any of the examples described in this article in your own projects, please conduct a careful evaluation first. This site assumes no responsibility for any losses resulting from implementations made without prior evaluation.

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