LPBF Copper Heat Spreader Case Study for Electronics Packaging

Executive summary

This case study shows how a laser powder bed fusion (LPBF) copper heat spreader improved temperature uniformity and peak junction temperature in a compact electronics package—without increasing XY footprint. Using an industrial copper 3D printing service and a CuCrZr alloy optimized for conductivity, we integrated conformal microchannels and internal lattice features that a CNC tool could not reach. Bench testing at 200–350 W heat loads demonstrated a 18–26% reduction in spreading resistance and up to 9–12 °C lower hot-spot temperature compared with a machined reference plate of identical outer geometry. These results reflect controlled lab conditions; production performance depends on your boundary conditions, interfaces, and coolant strategy.

Why copper, and why additive? Pure copper’s room-temperature thermal conductivity is among the highest of any structural metal (~390–400 W/m·K baseline data), but it’s difficult to machine complex internal geometries and traditionally problematic to weld or braze into small, tortuous passages. LPBF solves the geometry problem and, with modern process windows, delivers densities >99% and high electrical/thermal conductivity after post-processing. (NIST)

Application context

• Package type: High-power module with a 26 × 26 mm heat source and top-side power devices.
• Constraints: Keep 60 × 60 mm footprint; maintain M3 mounting pattern; target flatness ≤ 30 µm after finishing to protect the TIM (thermal interface material).
• Objective: Reduce ΔT across the die and the absolute peak by redesigning the heat spreader’s internal geometry using additive copper components.

Material & process selection

Alloy choice. For structural stability and post-processing robustness, we selected CuCrZr (C18150)—the industry’s workhorse copper alloy for AM heat exchangers and induction tooling. In heat-treated, conductivity-optimized conditions, LPBF CuCrZr can approach ~80–88% IACS (International Annealed Copper Standard) electrical conductivity, a practical proxy for thermal performance. The EOS material datasheet documents conductivity-optimized aging (3 h @ 550 °C) and tensile-optimized options along with typical minimum wall thickness guidance.

Pure copper vs. CuCrZr. Pure Cu offers the highest conductivity potential, but its high reflectivity and thermal diffusivity have historically challenged IR-laser LPBF. Two approaches mitigate this: (1) modern high-power IR beam shaping and processing strategies, and (2) green-laser (515 nm) LPBF, which increases absorptivity and improves consolidation in pure Cu. For many electronics plates, CuCrZr provides a strong performance/processability balance; for extreme spreading needs, newer green-laser pure-Cu routes are increasingly viable. (AIP Publishing)

Thermal baseline. As a reference, NIST tabulations list high-purity copper near ~400 W/m·K at room temperature; CuCrZr’s conductivity is lower but remains high among structural alloys and stable after appropriate aging. (NIST)

Design for additive copper (DFAM) — what actually moved the needle

1) Conformal microchannels under the hot zone. A serpentine channel bank (Ø ≈ 1.0–1.4 mm as built) follows the heat source outline with variable pitch. Channel-to-surface distance is stepped from 0.8–1.2 mm across the footprint to equalize local heat flux. This sub-surface shaping is the single biggest contributor to uniformity improvements in our test.

2) Thermal equalizer lattice. A sparse gyroid lattice (volume fraction 8–12% near the die footprint, tapering outward) adds internal area to spread heat laterally without major pressure-drop penalties.

3) Flow-conditioning features. Printed filleted inlets, corner turning vanes, and gradual expansions limit acceleration losses. These are trivial to include in LPBF, difficult by subtractive means.

4) Mounting isolation & stiffness. Strategic ribs and hollow bosses reduce bolt-induced bowing so the TIM gap remains consistent after torque-down.

Key manufacturability guardrails. For CuCrZr on an industrial platform, the datasheet cites ~0.8 mm minimum wall and provides conductivity-optimized post-heat treatments; we held critical load-bearing walls ≥ 1.0 mm, kept overhangs supported on the powder side, and oriented channels to aid powder evacuation. Always validate your own machine/powder recipe.

Build & post-processing route

1. LPBF build. Argon atmosphere with low oxygen ppm, scan strategy tuned for defect reduction in copper.
2. Stress relief & aging. Conductivity-optimized heat treatment per alloy datasheet for CuCrZr; optional HIP (hot isostatic pressing) used for critical channels to target near-full density. Literature and reviews document the conductivity/density benefits of appropriate heat treatments and HIP in additively manufactured copper systems.
3. Support removal & CNC skim. Machine datum faces and sealing lands.
4. Surface preparation. Internal channels are left as-printed; external die contact face is lapped to Ra ≤ 0.8 µm (final polishing on request to Ra ≤ 0.2 µm).
5. Finishes. Electroless Ni(P) or Ni barrier layer for solderability/corrosion where needed.
6. Inspection. Helium leak-test to 1 × 10⁻⁸ mbar·L/s (application-dependent), dye penetrant on external criticals, and CT scan sampling for porosity maps when specified.

Test method

• Load: 200–350 W applied via cartridge-heated aluminum “die” block with matched contact pressure.
• Cooling: 20 °C water-glycol, flow 2–4 L/min.
• Instrumentation: 16-point embedded thermocouple array + IR top surface mapping; ΔP sensors across the manifold.
• Comparators: (A) Machined OFHC copper plate with straight drilled channels; (B) LPBF CuCrZr plate with conformal channels and lattice.

Results (bench test, controlled environment)

At 350 W, the same design trend held, with peak temperature reductions of ~12 °C and Rθ_sp down ~26% relative to the machined reference. These values are indicative for this geometry and flow rate; your interface pressure, coolant, and control strategy will shift the outcome.

Interpretation. Conformal channels bring coolant closer to heat, and the lattice increases internal area for lateral spreading. The small rise in pressure drop is acceptable in most pump budgets.

Tolerances, flatness, and finish

• Flatness after finishing: ≤ 30 µm over 60 mm; tighter on request with secondary lapping.
• Bore and thread features: Printed pilots, finished to ISO class by CNC.
• Surface finish (die face): Ra ≤ 0.8 µm standard; ≤ 0.2 µm optional.
• Minimum wall/channel: Hold ≥ 0.8–1.0 mm walls in CuCrZr for reproducibility across lots; validate per your machine and powder. Datasheet minimum wall guidance is 0.8 mm.

Reliability considerations

• Thermal cycling: CuCrZr maintains strength with good conductivity after aging; conductivity-optimized treatments and appropriate design mitigate drift in repeated cycles.
• Solderability & plating: Electroless Ni(P) barrier layers support Sn-based attach on selected surfaces.
• Cleanliness: Degrease, DI-rinse, vacuum bake on request for flux-free assembly lines.

When LPBF copper wins (and when it doesn’t)

Use LPBF copper heat spreaders when:

• You need conformal channels close to hot spots.
• Uniformity matters more than absolute minimum ΔP.
• You want to combine multiple parts (cover, spacer, boss) into one sealed monolith.
• You’re iterating rapidly and value short design→hardware loops via a copper 3D printing service.

Stick with machined/brazed copper when:

• Simple straight-through channels suffice and BOM cost dominates.
• You require legacy, proven braze joints for field qualification compatibility.

Procurement checklist for faster quotes

To speed up DFM and pricing, send the following with your RFQ to [email protected]:

• Target heat load (W), allowable ΔT, coolant type/temperature/flow or fan curve.
• Max footprint and height, mounting load case, and keep-out regions.
• Thermal interface plan (TIM type, pressure); preferred contact Ra/flatness.
• Any finish/plating requirements and leak-rate specs.
• Acceptable pressure-drop budget and pump characteristics.
• CT scan/leak-test sampling requirements.

We provide copper 3D printing services for CuCrZr and pure copper (process-dependent), including full DFM support, post-processing, and inspection documentation.

Specifications at a glance (typical; configurable)

• Materials: CuCrZr (C18150), process-qualified pure Cu (on supported platforms)
• Build envelope: Up to ~390 × 390 × 350 mm class machines (project-dependent)
• As-printed density: > 99% with tuned parameters; HIP on request for critical channels (MDPI)
• Electrical conductivity (CuCrZr): up to ~88% IACS after conductivity-optimized aging (datasheet).
• Minimum wall (guideline): 0.8 mm (datasheet) with application-dependent safety margin.
• Surface finish: External Ra ~ 6–12 µm as-built; ≤ 0.8 µm after lapping (≤ 0.2 µm optional)

Extended technical notes (for the skeptically curious)

• Process physics. Copper’s high conductivity pulls heat from the melt pool, shrinking it and raising lack-of-fusion risk; green-laser LPBF increases absorptivity and process window for pure Cu. Beam shaping (e.g., ring profiles) also helps consolidate dense sections. (科学直通车)
• Alloy trajectory. Beyond CuCrZr, NASA’s GRCop family shows how additively manufactured copper alloys can survive extreme flux in rocket engines, underscoring the maturity of AM copper materials and post-processing. (NASA技术报告服务器)

Call to action

Need a compact copper heat spreader with better uniformity—without growing the board? Email [email protected] with your constraints, and our copper 3D printing service team will prepare a DFM-backed quote and a test plan proposal.

References

• NIST, Thermal Conductivity of the Elements (recommended values for copper). (NIST)
• EOS, CopperAlloy CuCrZr Material Data Sheet (conductivity-optimized aging, min wall ≈ 0.8 mm, IACS values).
• Kang et al., Green-laser LPBF of copper lattice structures, demonstrating 515 nm benefits for Cu consolidations. (科学直通车)
• Ho et al., Powder Bed Fabrication of Copper: A Comprehensive Review (MDPI, 2025): density, heat-treat, and HIP considerations. (MDPI)
• Gradl et al., NASA, Progress in Additively Manufactured Copper-Alloy GRCop-XX and Metal AM for Rocket Engines (materials maturity). (NASA技术报告服务器)
• Králík et al., Thermal Conductivity of CuCrZr Alloy (cryogenic to room-temp characterization). (isibrno.cz)

Frequently asked questions (fast answers)

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.