Engineering Reference: Stamped Electrical Terminals Material Properties
An FEA model using generic copper property data cannot predict cold-work hardening, forming-induced conductivity drops, or stress relaxation. These three failure modes emerge only when material data matches actual stamped part behavior.
In this reference, you will find mechanical, thermal, and processing data for C11000 copper, Brass 260, and Phosphor Bronze C51000, all anchored in ASTM test methods for direct import into FEA material cards.
Read on for the full datasheet.
Mechanical & Physical Properties
Mechanical property selection for stamped electrical terminals begins with two competing requirements: the material must yield enough to form the contact geometry without fracture, yet must retain sufficient spring-back resistance to maintain contact normal force over the product lifecycle. The three alloys below occupy distinct positions on this formability-versus-strength spectrum, and the choice between them determines everything from minimum bend radius to long-term fretting resistance. For an overview of how material selection impacts production cost and lead time, see stamped terminal production capabilities.
Tensile Strength & Yield Behavior
Tensile and yield strength define how a terminal material responds to the bending, coining, and blanking forces applied during progressive stamping. Annealed C11000 copper enters the die at 220-250 MPa tensile strength with 45% elongation. It forms easily but offers minimal spring contact force in the finished terminal.
Half-hard Brass 260 raises tensile strength to 310-415 MPa while retaining 23% elongation, which provides the forming window most production stampers target for multi-bend terminal geometries.
In bronze terminal stamping, phosphor bronze C51000 in spring temper reaches 690-760 MPa tensile strength with elongation dropping to 8%. This delivers the highest contact normal force of the three but demands larger bend radii and tighter springback compensation in tooling design. Cold working beyond 37% reduction raises C11000 tensile strength to 345 MPa but drops conductivity from 101% IACS to approximately 98% IACS. This trade-off matters when the terminal also functions as a current-carrying path.
Hardness follows the same ranking. Annealed C11000 measures 45-55 HV. Half-hard Brass 260 reaches 110-140 HV.
Spring-temper phosphor bronze C51000 achieves 180-210 HV, which directly correlates to improved wear resistance in high-cycle connector applications exceeding 10,000 insertion cycles.
| Property | C11000 (Annealed) | Brass 260 (Half-Hard) | Phosphor Bronze C51000 (Spring) | Test Method |
|---|---|---|---|---|
| Tensile Strength | 220-250 MPa | 310-415 MPa | 690-760 MPa | ASTM E8 |
| Yield Strength (0.2% offset) | 70-110 MPa | 240-350 MPa | 550-620 MPa | ASTM E8 |
| Elongation at Break | 45% | 23% | 8% | ASTM E8 |
| Hardness | 45-55 HV | 110-140 HV | 180-210 HV | ASTM E384 |
| Elastic Modulus | 117 GPa | 110 GPa | 110 GPa | ASTM E111 |
All values assume room-temperature testing at 23 degree C per ASTM E8 conditioning requirements. Yield strength drops approximately 8-12% for C11000 and 5-8% for phosphor bronze when ambient temperature reaches 75 degree C, a condition common inside sealed automotive engine-bay connectors.
[Data Anchor]: Yield strength of annealed C11000 copper floor at 70 MPa. Any terminal design requiring contact normal force above 2.5 N must specify half-hard Brass 260 or spring-temper phosphor bronze at the material selection stage.
Electrical Conductivity & Contact Resistance
Electrical conductivity measured as % IACS is the primary functional metric for current-carrying stamped electrical contacts. C11000 delivers 101% IACS in annealed condition, making it the benchmark against which all other copper alloys are measured. Brass 260 drops to 28% IACS, adequate for mechanical grounding terminals where force retention matters more than current capacity.
Phosphor bronze C51000 measures 15% IACS, positioning it exclusively for signal-level contacts and spring-force-dependent applications where conductivity takes a secondary role.
Contact resistance consists of two components: bulk resistance governed by % IACS and constriction resistance governed by contact area and surface oxide films. A C11000 terminal with 0.5 mm thickness and 5 mm squared contact area contributes approximately 0.35 milliohm bulk resistance. The same geometry in phosphor bronze contributes 2.4 milliohm. This 7x increase becomes significant in circuits carrying above 5 A continuous current.
Cold working after forming reduces C11000 conductivity by 2-5% IACS, a derating factor that FEA electrical-thermal coupled simulations must include.
[Data Anchor]: C11000 copper conductivity ceiling of 101% IACS degrades to a minimum of 96% IACS after heavy cold working beyond 50% reduction. Terminal designs carrying above 10 A must derate current capacity by 5% to account for this forming-induced conductivity loss.
Fatigue & Impact Resistance
Stamped electrical connectors undergo repeated insertion-extraction cycles, each cycle producing micro-strain at the contact beam root. Phosphor bronze C51000 in spring temper exhibits a fatigue strength of 210 MPa at 10 million cycles, tested per ASTM E466 rotating-beam methodology. Brass 260 half-hard achieves 140 MPa at the same cycle count.
C11000 annealed reaches only 75 MPa at 10 million cycles, limiting it to low-cycle connector applications below 1,000 mating cycles.
Impact resistance matters when terminals face assembly-line insertion forces or snap-fit engagement. C11000 absorbs 55 J of impact energy in Charpy V-notch testing at 23 degree C.
Brass 260 absorbs 35 J. Phosphor bronze drops to 20 J due to its higher strength and lower ductility.
At sub-zero temperatures (-40 degree C, representative of cold-start environments), C11000 retains 85% of its room-temperature impact energy while phosphor bronze drops to 60%, making C11000 the preferred choice for terminals operating in arctic or aerospace ground-support environments.
[Data Anchor]: Phosphor bronze C51000 fatigue limit of 210 MPa at 10 million cycles defines the upper bound for dynamic contact applications. Terminals experiencing above 50,000 insertion cycles must specify this alloy regardless of conductivity requirements.
Thermal & Environmental Limits
Terminal material properties measured at room temperature do not hold at the 85-125 degree C operating range common inside automotive connectors and power distribution modules. Thermal derating affects tensile strength, conductivity, and contact normal force simultaneously, and the derating curves differ significantly across the three alloy families. Review our quality and testing protocols for validated thermal performance data.
Temperature Resistance & Thermal Stability
Continuous operating temperature limits are dictated by stress relaxation behavior, not melting point. C11000 copper begins measurable stress relaxation at 100 degree C, losing approximately 5% of initial contact force after 1,000 hours at this temperature. Brass 260 shows similar relaxation onset at 100 degree C but loses 8% contact force over the same duration due to zinc-atom diffusion within the alpha-brass crystal lattice.
Phosphor bronze C51000 tolerates continuous operation at 125 degree C with only 3% force loss after 1,000 hours, making it the default choice for engine-compartment and under-hood connectors. Above 150 degree C, even phosphor bronze enters rapid stress relaxation: 15% force loss occurs within 500 hours at 150 degree C, and 30% force loss occurs within 100 hours at 175 degree C. Thermal conductivity values follow the same ranking as electrical conductivity: C11000 at 388 W/m-K, Brass 260 at 120 W/m-K, and phosphor bronze at 69 W/m-K, per ASTM E1530 guarded heat flow meter method.
[Data Anchor]: Continuous operating temperature must not exceed 125 degree C for phosphor bronze C51000. Exceeding this threshold triggers stress relaxation above 15% of initial contact force within 500 hours, sufficient to cause intermittent electrical contact in mated connectors.
Corrosion & Environmental Durability
Galvanic corrosion risk arises when a copper-alloy terminal mates with an aluminum conductor or steel connector body. C11000 exhibits an anodic index of 0.35 V versus a saturated calomel electrode.
Aluminum conductors measure 0.75 V. The 0.40 V difference exceeds the 0.25 V threshold for galvanic couple formation in humid environments above 60% RH.
Tin plating over the C11000 substrate shifts the effective surface potential and eliminates the couple, provided plating thickness exceeds 2.5 micrometre and porosity remains below 5 pores per square millimetre.
Brass 260 carries a dezincification risk in acidic environments below pH 5 or in chloride-containing atmospheres above 50 ppm concentration. Selective leaching of zinc from the alpha-brass matrix leaves a porous copper sponge structure that loses 40-60% of its original tensile strength within 6 months of continuous exposure. Phosphor bronze C51000 resists both dezincification and stress-corrosion cracking in chloride environments, passing 96-hour ASTM B117 salt spray testing with no visible pitting at 0.3 mm material thickness.
[Data Anchor]: Unplated C11000 copper terminals form a galvanic couple with aluminum conductors when humidity exceeds 60% RH. A potential difference of 0.40 V drives corrosion rates above 0.1 mm per year in coastal environments, requiring a minimum 2.5 micrometre tin barrier plating.
Processing Behaviors & Morphology
The same material that reads cleanly on a tensile test curve behaves differently when a progressive die punches, bends, and coins it into electrical stamping parts at 200-400 strokes per minute. Grain structure, work-hardening rate, and springback profile are not captured by standard ASTM tensile data. They must be characterized through processing trials or drawn from empirical stamping datasets. Kravzik correlates alloy properties with tooling design parameters through its progressive die tooling process.
The table below compares the four processing parameters that most directly influence progressive die design: blanking clearance as a percentage of material thickness, springback compensation angle for a 90-degree bend, minimum bend radius relative to thickness, and plating adhesion performance on as-stamped surfaces.
Grain Structure & Blanking Behavior
In electrical stamping, the blanked edge of a stamped terminal reveals three distinct zones: rollover, burnish, and fracture. Grain size controls the proportion of each zone. C11000 with ASTM grain size 6 (45 micrometre average diameter) produces a 35-40% burnish zone, the smooth and dimensionally accurate portion of the cut edge critical for contact interface geometry.
Brass 260 with ASTM grain size 7 (32 micrometre) yields a 45-50% burnish zone due to its finer grain structure and lower ductility compared to pure copper.
Phosphor bronze C51000 at ASTM grain size 8 (22 micrometre) produces the cleanest cut edge with 55-60% burnish zone, which reduces the need for secondary deburring in terminals where the blanked edge becomes the contact surface. Blanking clearance as a percentage of material thickness ranges from 3-5% for phosphor bronze to 5-8% for annealed C11000.
Running clearance below 3% accelerates punch wear and produces secondary shear zones. Running above 8% increases burr height beyond 0.05 mm, the typical maximum for connector terminal specifications.
| Processing Parameter | C11000 (Annealed) | Brass 260 (Half-Hard) | Phosphor Bronze C51000 (Spring) | Tooling Impact |
|---|---|---|---|---|
| Grain Size (ASTM / micrometre) | ASTM 6 / 45 µm | ASTM 7 / 32 µm | ASTM 8 / 22 µm | Burnish zone proportion |
| Blanking Clearance (% thickness) | 5-8% | 4-6% | 3-5% | Punch-to-die clearance set |
| Springback Angle (90-degree bend) | 2-4 degrees | 5-8 degrees | 8-15 degrees | Bend angle overbend in tooling |
| Minimum Bend Radius (x thickness) | 0.5 t | 1.0 t | 2.0 t | Punch nose radius |
| Plating Adhesion (cross-hatch rating) | 5B (excellent) | 4B | 3B (requires pre-clean) | Pre-plate surface prep |
Moisture absorption is not a factor for copper alloys in the traditional polymer-science sense, but surface oxidation begins within 24 hours of stamping for uncoated C11000 exposed to 50% RH ambient air. This oxide film reaches 20-30 nanometre thickness within 72 hours and degrades solderability and wire-bonding performance. Phosphor bronze forms a thinner, more stable oxide layer of 5-10 nanometre under the same conditions, which is why it tolerates longer shelf life between stamping and assembly.
[Data Anchor]: Blanking clearance for phosphor bronze C51000 must not fall below 3% of material thickness. Clearances below this threshold produce secondary shear zones that increase burr height above 0.05 mm and accelerate carbide punch wear to 3-5 micrometre per 100,000 strokes.
Springback & Dimensional Stability
Springback, the elastic recovery that occurs after a bend punch retracts, is the single largest source of dimensional variation in electrical stamping components. The compensation angle required depends on the ratio of yield strength to elastic modulus and the bend radius-to-thickness ratio. Annealed C11000 with a yield-to-modulus ratio of 0.0006 to 0.0009 requires only 2-4 degrees of overbend for a 90-degree target angle at 1.0 t bend radius.
Half-hard Brass 260 at yield-to-modulus ratio of 0.002 to 0.003 demands 5-8 degrees compensation. Spring-temper phosphor bronze at ratio 0.005 to 0.006 requires 8-15 degrees. The widest range occurs because small variations in incoming material temper produce large differences in springback angle.
A 15 HV difference in incoming phosphor bronze hardness (within the 180-210 HV spec range) shifts springback by roughly 1.5 degrees. Process control must therefore include incoming hardness verification per ASTM E384 on every coil, not just every heat.
[Data Anchor]: Springback angle for spring-temper phosphor bronze C51000 at 90-degree bend geometry ranges from 8 to 15 degrees. A 15 HV hardness variation within the 180-210 HV spec range shifts springback by 1.5 degrees, requiring per-coil hardness verification before die setup.
Manufacturability & Industrial Applications
Material property data answers the question of what a metal can do. Manufacturability answers the question of whether those properties can be realized at production speed and repeatable tolerances. The three alloy families covered in this datasheet each suit specific stamping process windows, and the gap between laboratory tensile data and production-floor dimensional capability narrows when alloy selection aligns with the stamping method.
Stamping Compatibility by Alloy
C11000 copper in annealed condition runs at the highest terminal stamping press speeds, up to 400 strokes per minute on a 60-ton mechanical press with carbide tooling, because its low yield strength imposes minimal punch wear and its high ductility forgives small clearance variations across progressive stations. Tooling maintenance intervals extend to 500,000 strokes between re-sharpening cycles when blanking C11000 at 6% clearance. For electrical component metal stamping, Brass 260 half-hard reduces maximum press speed to 250-300 spm due to higher punch forces and faster edge wear, but it compensates with tighter dimensional stability: a 0.25 mm thickness Brass 260 terminal holds plus or minus 0.03 mm on critical bend dimensions versus plus or minus 0.05 mm for the same geometry in C11000.
Phosphor bronze C51000 in spring temper runs at 150-200 spm maximum, requires tungsten carbide tooling for blanking punches, and demands re-sharpening every 150,000 strokes. The trade-off is a finished terminal that delivers the highest contact normal force retention in the product family. For terminals requiring both conductivity and spring force, a bi-metal approach (C11000 body with phosphor bronze contact beam) resolves the conflict outside the stamping die via post-stamp assembly.
For custom metal terminals, Kravzik maintains full inventory of C11000, Brass 260, and phosphor bronze C51000 strip in thicknesses from 0.15 mm to 1.5 mm for stamped terminal production.
[Data Anchor]: C11000 copper achieves maximum press speed of 400 spm at 6% blanking clearance with carbide tooling and 500,000-stroke sharpening intervals. Phosphor bronze C51000 caps at 200 spm with 150,000-stroke sharpening intervals, a 2.5x productivity differential that must be factored into per-part cost models.
Plating & Finishing Compatibility
Plating adhesion strength varies significantly across the three substrate alloys. C11000 copper achieves a cross-hatch adhesion rating of 5B under ASTM D3359 for tin and silver electroplated finishes, provided the surface receives alkaline degreasing within 8 hours of stamping to prevent oxide film buildup beyond 10 nanometre. Brass 260 achieves 4B adhesion for tin plating due to zinc-atom surface segregation during electrodeposition, which creates a zinc-rich interlayer approximately 0.5 micrometre thick that reduces the effective tin-to-substrate bond area.
Phosphor bronze C51000 rates 3B for as-stamped surfaces and requires an electrolytic alkaline pre-clean followed by a nickel strike layer of 0.5-1.0 micrometre before tin or silver top-coat deposition. This extra process step adds cost but ensures the plating system survives the 5% minimum elongation that spring-temper phosphor bronze terminals experience during connector mating, preventing plating crack propagation into the substrate.
Pre-plated strip, where tin or silver is applied at the mill before stamping, eliminates post-stamp plating for C11000 and Brass 260 but is not recommended for phosphor bronze due to the risk of plating delamination at the tight bend radii this alloy requires. See Kravzik’s in-house plating and finishing capabilities for process details.
[Data Anchor]: Phosphor bronze C51000 requires a nickel strike layer of 0.5-1.0 micrometre before tin or silver top-coat to achieve acceptable plating adhesion. Without this strike layer, cross-hatch adhesion falls to 3B and plating cracks propagate into the substrate during the 5% minimum elongation experienced at connector mating.
Data to Spec
You selected C11000 copper six months ago because the conductivity spec demanded 100% IACS and the FEA model converged cleanly at 25 degree C ambient. What happens when that terminal operates inside a sealed engine-bay connector where ambient temperature reaches 105 degree C and the contact beam undergoes 50,000 micro-motion cycles over a 150,000-kilometre vehicle lifetime? Yield strength drops 12% from the room-temperature value, contact normal force degrades below 2.0 N, and the bulk resistivity rises 3.8%. This triple failure mode is one that a material selection matrix built on room-temperature data alone would not predict.
Kravzik cross-references your terminal geometry, operating temperature profile, and insertion-cycle requirement against the alloy-specific property data in this datasheet before the first strip enters the press. Learn more about our precision metal stamping capabilities for terminals. An in-house material inventory spanning C11000, Brass 260, and phosphor bronze C51000 in thicknesses from 0.15 mm to 1.5 mm means the material that matches your FEA boundary conditions is already on the shelf, not on a mill lead-time schedule.
Still reconciling FEA results that diverge from dimensional reality on every prototype run? Send us your terminal drawing for a material-property-matched DFM report. Kravzik returns a feasibility assessment with alloy-specific bend compensation factors and plating adhesion projections within 48 hours.
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