Pure Copper (Cu)

Material Profile: Pure Copper (Cu) for Binder Jetting

Binder Jetting Engineering Material Technical Report Series

Compiled from manufacturer technical datasheets and peer-reviewed literature

Abstract—Pure copper (Cu, ≥ 99.9 wt%) is the highest-conductivity metal in the binder-jet portfolio (electrical conductivity ≈ 100 % IACS, thermal conductivity ≈ 400 W/m·K) and is customer-qualified across Desktop Metal X-Series and Production System. Copper is notoriously difficult to process by laser PBF because of its very low absorptivity at 1064 nm (~ 5 %); binder jetting eliminates this constraint entirely — the laser is replaced by a polymer binder, and densification occurs in a sintering furnace at 1050 °C in pure H₂. Sintered density typically reaches 95–98 % theoretical, sufficient for the dominant applications: induction-heater coils, RF/microwave heat-sinks, vacuum thermal-management plates, and electrical bus-bar connectors. For applications requiring full > 99 % density, a HIP cycle at 850 °C / 100 MPa / 4 h is recommended.

Index Terms—additive manufacturing, binder jetting, pure copper, Cu, thermal conductivity, electrical conductivity, heat exchanger, RF.

I.  MATERIAL IDENTIFICATION

This section establishes the canonical names and commercial designations under which the material is supplied.

A.  Designation

Trade names: Desktop Metal Pure Copper / Cu (X-Series customer-qualified, Production); ExOne Cu; Digital Metal DM Cu; HP Metal Jet Pure Copper. Wrought equivalents: ASTM B152 / B187 / B188 (UNS C10100 / C10200 / C11000); EN 1976 (Cu-OFE / Cu-DHP). UNS C10100 (OFE — oxygen-free electronic, ≤ 5 ppm O) is the standard binder-jet target grade.

B.  Full Chemical Name

High-purity copper. Composition (wt%): Cu ≥ 99.95 (typical OFE-grade target), with controlled impurities P ≤ 5 ppm, O ≤ 5 ppm, S ≤ 15 ppm, Bi ≤ 1 ppm, Pb ≤ 5 ppm. Single-phase FCC γ-Cu structure; no second phases.

C.  Aliases and Alternative Designations

II.  COMPOSITION AND MOLECULAR STRUCTURE

A.  Empirical Chemical Formula

Cu(≥ 99.9 wt%) + trace impurities (P, O, S < 30 ppm combined). Single-phase FCC γ-Cu (a ≈ 3.615 Å). No alloying elements; no second phases; no precipitation hardening.

Fig. 1.  Repeating unit / structural schematic of the polymer matrix.

Fig. 2.  Schematic of the single-phase polymer (no reinforcement).

B.  Composition Breakdown

TABLE I
 COMPOSITIONAL BREAKDOWN OF PURE COPPER (DESKTOP METAL X-SERIES) (TYPICAL / PER SUPPLIER DATASHEET)

III.  MECHANICAL PROPERTIES — XY BUILD DIRECTION (HORIZONTAL)

In the XY orientation the tensile load is applied parallel to the powder-bed plane. Binder-jetted (BJ) parts in the as-sintered state generally show modest in-plane vs build-axis anisotropy because sintering occurs near the solidus and re-distributes the porosity left by the binder-removal step. For metal BJ, post-sintering treatments (HIP, solution-anneal, age) are commonly applied to bring properties to wrought-equivalent and to eliminate residual closed porosity.

TABLE II
 MECHANICAL PROPERTIES — XY ORIENTATION (PURE COPPER (DESKTOP METAL X-SERIES))

IV.  MECHANICAL PROPERTIES — Z BUILD DIRECTION (VERTICAL)

In the Z orientation the tensile load is applied perpendicular to the printed layers. Binder-jet metal parts typically exhibit Z-direction strength within 5–15 % of XY in the as-sintered state, since the inter-layer interface effectively dissolves during high-temperature sintering. For sand-mould materials, Z-direction strength is dominated by inter-layer binder bonding and is generally 60–90 % of XY in transverse strength.

TABLE III
 MECHANICAL PROPERTIES — Z ORIENTATION (PURE COPPER (DESKTOP METAL X-SERIES))

Pure copper is essentially isotropic in BJ form. Recrystallisation during the 1050 °C sinter erases the layer-by-layer structure entirely. Z-direction conductivity equals XY because there is no aligned defect microstructure to scatter electrons. The principal property variability is sintered density (95 % vs HIP 99 %), not direction.

V.  RECOMMENDED PROCESS PARAMETERS

Values summarised below give consensus operating windows from public datasheets (Desktop Metal, ExOne, voxeljet, cprint3d). Specific machines and parameter sets may differ within ±10 %; the supplier's verified parameter sheet always supersedes this table. For metal binder jetting, complete green-state cure (~200 °C) and a high-temperature de-bind / sinter cycle (typically 1 100–1 380 °C in H₂ / Ar / vacuum) are mandatory after print. For sand binder jetting, parts are usable directly after print (with optional microwave or oven post-cure).

TABLE IV
 RECOMMENDED BINDER-JETTING PROCESS PARAMETERS FOR PURE COPPER (DESKTOP METAL X-SERIES)

VI.  GLASS TRANSITION TEMPERATURE (TG)

Reported / typical Tg: Not applicable (metallic alloy).

Critical thermal limits: recrystallisation temperature ≈ 200 °C (full softening above this); continuous service temperature ≈ 250 °C in inert atmosphere or 200 °C in air (oxidation); melting point 1083 °C (note: only ~ 30 °C between sinter temperature and melting point — extremely narrow process window).

VII.  HEAT DEFLECTION TEMPERATURE (HDT)

Heat deflection temperature is the temperature at which a standard bar deflects 0.25 mm under a specified flexural load (ASTM D648 / ISO 75).

TABLE V
 HEAT DEFLECTION TEMPERATURE OF PURE COPPER (DESKTOP METAL X-SERIES) UNDER STANDARD TEST LOADS

VIII.  DISTINGUISHING CHARACTERISTICS AND STANDARDS

A.  Highest conductivity in the BJ portfolio

Electrical conductivity ≈ 95–100 % IACS and thermal conductivity ≈ 380–400 W/m·K — by far the highest of any binder-jettable metal. Aluminium AlSi10Mg achieves only ~ 119 W/m·K thermal and 29 % IACS electrical. Cu binder jetting is the enabling technology for high-frequency RF heat-sinks and induction coils that simply cannot be made any other way.

B.  Eliminates the laser-PBF copper problem

Laser PBF copper is challenging because Cu reflects > 95 % of 1064 nm Nd:YAG laser energy. Solutions (high-power green lasers, Cu-15Cr or CuCrZr alloying, laser pre-heating) all compromise either purity or cost. Binder jetting bypasses this entirely — the binder is independent of substrate optical properties — and produces > 99.9 % pure Cu directly.

C.  Geometric freedom for thermal-management lattices

Internal lattice / micro-channel cooling structures impossible to machine are routine in BJ Cu. RF heat-sink fin geometries optimised for natural-convection plus skin-effect surface area are demonstrably 30–50 % more efficient than equivalent machined-Cu fins.

D.  H₂ embrittlement requires OFE-grade powder

Standard ETP copper (UNS C11000) contains 200–400 ppm oxygen — when sintered in pure H₂ at 1050 °C, hydrogen reduces internal Cu₂O, generating H₂O steam at grain boundaries → embrittlement. Binder-jet Cu must use OFE-grade (UNS C10100, ≤ 5 ppm O) powder. Powder cost is ~ 2× ETP.

E.  Per-part cost vs other Cu AM routes

BJ Cu per-part cost is ~ 1/3 of green-laser PBF Cu and ~ 1/5 of cold-spray Cu. For typical heat-sink and RF housing geometries, BJ Cu is the most economical AM Cu route at any production volume above 5 parts. Below 5 parts, conventional brazing of machined Cu sheet remains competitive.

IX.  REPRESENTATIVE APPLICATIONS

Pure Copper (Desktop Metal X-Series) is typically deployed in the following applications:

1)  RF / microwave heat-sinks: Conformal heat-sinks for high-power RF amplifiers, 5G base stations, satellite payloads — exploit BJ's geometric freedom and Cu's high thermal conductivity.

2)  Induction heating coils: Custom-geometry induction coils for localised heating of automotive/aerospace parts; previously hand-formed from Cu tube — BJ produces optimised geometry in hours.

3)  Vacuum thermal-management plates: Cold plates for semiconductor wafer chucks and ion-source baseplates; HIP'd to ~ 99 % density to ensure vacuum tightness.

4)  High-power-electronics bus-bars: Custom geometry bus-bars and current-collectors for EV traction inverters; replaces brazed Cu sheet assemblies with single-piece AM components.

5)  Heat exchangers (compact, high-performance): Cu-walled compact heat exchangers for closed-loop liquid cooling; superior thermal performance vs equivalent stainless steel.

X.  REFERENCES

[1]  Desktop Metal, “Pure Copper — Material Profile (X-Series customer-qualified),” Materials portfolio.

[2]  ASTM B152/B152M-19, “Standard Specification for Copper Sheet, Strip, Plate, and Rolled Bar,” 2019.

[3]  ASTM B187/B187M-20, “Standard Specification for Copper, Bus Bar, Rod, and Shapes and General Purpose Rod, Bar, and Shapes,” 2020.

[4]  ASTM B193-20, “Standard Test Method for Resistivity of Electrical Conductor Materials,” 2020.

[5]  Special Metals Corporation, “Copper Alloys Handbook,” Reference Publication, 2018.

[6]  L. Kaden et al., “Binder-jetting of pure copper: density, conductivity, and challenges,” Additive Manufacturing, vol. 47, 102330, 2021.

[7]  ASTM E8/E8M-22, “Standard Test Methods for Tension Testing of Metallic Materials,” ASTM International, 2022.

[8]  ASTM B962-17, “Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes' Principle,” ASTM International, 2017.

[9]  ASTM E18-22, “Standard Test Methods for Rockwell Hardness of Metallic Materials,” ASTM International, 2022.

[10]  ASTM F3318-22, “Standard for Additive Manufacturing — Finished Part Properties — Specification for AlSi10Mg with Powder Bed Fusion — Laser Beam,” ASTM International, 2022.

[11]  ISO/ASTM 52900:2021, “Additive manufacturing — General principles — Fundamentals and vocabulary,” ISO, 2021.

[12]  ISO/ASTM 52904:2024, “Additive manufacturing — Process characteristics and performance — Practice for metal powder bed fusion process to meet critical applications,” ISO, 2024.

[13]  MPIF Standard 35-MIM, “Materials Standards for Metal Injection Molded Parts,” Metal Powder Industries Federation, 2022 ed.

[14]  Desktop Metal, “Material Properties of Binder Jet Parts,” Desktop Metal Technical White Paper. [Online]. Available: https://www.desktopmetal.com/resources/material-properties-of-binder-jet-parts

[15]  Desktop Metal, “Why Binder Jetting?” Desktop Metal Application Note. [Online]. Available: https://www.desktopmetal.com/resources/why-binder-jetting-1

[16]  Desktop Metal, “Materials portfolio overview,” Desktop Metal product page. [Online]. Available: https://www.desktopmetal.com/materials/

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