What is difference in electrical conductivity between copper and aluminum die castings?

Copper-alloy die castings can have higher electrical conductivity than aluminum die castings, but the difference is not one universal value. It depends on the exact copper, brass, bronze or aluminum alloy, chemistry and material condition. Compare certified or measured conductivity for the proposed production alloys, then validate resistance and temperature rise through the finished part, contacts, joints and surface system.

Pure metals are not the production comparison

Pure copper and pure aluminum are useful reference materials, but die-casting alloys contain elements chosen for castability, strength, die interaction, corrosion or machining. Those additions change conductivity. A brass selected for machining or a bronze selected for wear may conduct very differently from a high-conductivity copper alloy.

Likewise, A360, A380 and other aluminum casting families are not interchangeable. Require exact designation, governing specification, actual chemistry range and production condition. Do not assign a handbook value from annealed wrought stock to a die-cast part.

Conductivity comparison table

Use a declared measurement basis

Conductivity may be reported in different units or relative scales. The specification should name the method, temperature, specimen geometry, calibration and acceptance. If supplier data comes from a separately cast coupon, decide whether it represents the critical region of the production part.

For procurement, request certified typical data only as a screening input. Final acceptance may require lot chemistry, witness specimens or measurements from a defined part location. The plan should reflect consequence of failure and normal material variation.

Compare resistance, not only conductivity

An electrical component is designed around resistance and heat. Resistance depends on material resistivity, path length and cross-sectional area. A lower-conductivity aluminum design may use a larger section while retaining lower mass; a higher-conductivity copper concept may use a smaller path but carry greater density and material cost.

Model both finished geometries for allowable voltage drop, current density and temperature rise. Include constrictions around holes, threads, ribs and transitions. Current crowding can make a local feature control performance even when bulk conductivity is favorable.

Contacts and joints can dominate

Bolted, pressed, welded, brazed or plated contacts add interface resistance. Surface oxide, contamination, contact pressure, flatness, creep, thermal cycling and fretting affect long-term behavior. A copper casting with a poor joint can perform worse than a well-designed aluminum assembly.

Define fastener, torque, contact area, plating, lubricant if permitted and environmental sealing. Test initial and aged contact resistance after thermal, vibration or corrosion exposure relevant to the product. Do not approve the design from bulk alloy data alone.

Surface treatment matters

Plating may improve solderability, corrosion response or contact consistency, but its substrate preparation, thickness, porosity, adhesion and intermetallic behavior need qualification. Decorative finish is not automatically a functional contact finish. Mask or machine surfaces where the coating would interfere.

Aluminum anodizing forms an electrically insulating oxide and generally must be excluded from intended contact lands unless the design uses a separate conductive path. Copper alloy tarnish or corrosion products can also raise contact resistance. The full finish and service environment belong in the test.

Casting route and local continuity

Gate and fill design, oxide films, porosity, shrinkage and machining into subsurface material can affect a highly loaded electrical path. Not every internal indication materially changes resistance. Locate the critical current path and connect inspection limits to measured electrical performance.

Ask the copper-alloy supplier and aluminum die caster for comparable alloy-process data. Keep cavity, machining and finish traceable during validation.

Make a system-level material choice

Copper alloy may be selected where electrical loss, package size, joint count or heat generation justifies its cost and mass. Aluminum may be selected where a larger section is available, low mass matters, conductivity is sufficient, or complex integrated geometry provides product value. A hybrid aluminum body with copper contacts can be effective if joining and galvanic risks are controlled.

Compare tooling, gross shot metal, machining, plating, assembly, inspection and accepted yield. Include operating energy only when a defined duty cycle and measured resistance support it. Avoid unsupported lifetime savings claims.

RFQ inputs and final answer

Provide current, voltage-drop or resistance limit, duty, allowable temperature rise, path envelope, joint design, environment, alloy restrictions, finish, demand and validation method. Ask for exact alloys, conductivity basis, chemistry records, current-path DFM, process risk and finished assembly tests.

The conductivity difference is the measured or certified difference between the two specified production alloys at the declared condition. The correct design decision comes from finished-path resistance, thermal behavior, mass and cost, not a universal copper-versus-aluminum percentage.