Ultra-thin precision strip that stamps into a terminal 0.10 mm thick, holds 0.5–3 N contact force through 10,000 insertions, and plates to a gold finish 0.05 μm thick — with thickness tolerance held to ±0.005 mm across the coil.
Every connector terminal solves the same pair of problems: it must exert enough normal force to keep electrical resistance low, and it must survive thousands of insertions without losing that force. No single steel optimizes both spring force and corrosion resistance and cost. The four families below are how connector engineers pick the right balance for each terminal in the connector body.
C ≤0.15%, Cr 16–18%, Ni 6–8%. The lower nickel content makes SUS301 highly responsive to cold work: in the SH temper it reaches 1000–1500 MPa tensile, far above SUS304 at the same reduction. This high strength means the contact beam can be thinner (0.10–0.30 mm) while maintaining 0.5–3 N normal force, and it survives 5,000–10,000 insertion cycles through fatigue resistance. Supplied bright-annealed or skin-passed with a plating-ready surface.
Choose SUS301 SH for every spring terminal, contact beam and high-cycle connector.C ≤0.08%, Cr 18–20%, Ni 8–10.5%. More nickel than SUS301 gives better corrosion resistance but lower cold-work hardening response — typically 600–800 MPa in 1/2H temper. Used for general-purpose terminals, connector housings, ground contacts and terminal blocks where the environment is moist or corrosive and the cycle count is moderate. SUS304 is the default when corrosion resistance matters more than maximum spring-back.
Choose SUS304 for terminals in moist, outdoor or corrosive environments.C ≤0.12%, cold-rolled to 0.15–0.40 mm. SPCC is non-alloy, low-cost, and highly formable — ideal for deep-drawn EMI shielding cans, connector backshells and mounting brackets. Its ferromagnetic properties contribute to EMI attenuation, and it takes tin or nickel plating readily for solderability and corrosion protection. For shielding cans, SPCC is the standard because it balances formability, magnetic shielding and material cost.
Choose SPCC for EMI shielding cans, housings and structural brackets.C 0.62–0.73%, Mn 0.90–1.20%. High carbon and manganese give 65Mn a high elastic limit (≥800 MPa) and good hardenability, reaching HRC 42–48 after quenching and tempering. Used for relay reeds, heavy-duty contact springs and elastic contact pieces where the environment is dry and the priority is maximum spring force per unit thickness. 65Mn is lower cost than stainless but requires plating or coating for corrosion protection.
Choose 65Mn for relay reeds, heavy contact springs and dry-environment elastic parts.Indicative values from production connector programs; the final spec is agreed at RFQ against your terminal drawing, connector class and governing standard (JIS, AISI, GB, IEC).
| Component | Steel grade | Thickness | Key parameter |
|---|---|---|---|
| Connector spring terminal | SUS301 SH | 0.10 – 0.30 mm | Tensile 1000–1500 MPa, contact force 0.5–3 N, 5k–10k cycles |
| Ultra-thin terminal (SIM/SD card) | SUS301 SH | 0.05 – 0.10 mm | Tolerance ±0.005 mm, bright surface, plating-ready |
| USB / Type-C contact spring | SUS301 SH | 0.15 – 0.25 mm | Tensile ≥1200 MPa, insertion life ≥10,000 cycles |
| General terminal / housing | SUS304 1/2H | 0.20 – 0.50 mm | Tensile 600–800 MPa, corrosion-resistant |
| EMI shielding can | SPCC | 0.15 – 0.40 mm | Tin-plated, deep-drawable, magnetic shielding |
| Connector bracket / backshell | SPCC | 0.30 – 0.80 mm | Nickel-plated, formable, weldable |
| Relay reed / heavy contact spring | 65Mn Q&T | 0.15 – 0.40 mm | HRC 42–48, elastic limit ≥800 MPa |
| SIM / SD card slot leaf spring | SUS301 SH | 0.08 – 0.15 mm | High cycle fatigue, precision blanking |
Thickness tolerance is confirmed per coil at ±0.005 mm standard; ±0.003 mm available on request for high-precision programs. Tensile strength for SUS301 SH depends on cold reduction percentage — confirm the target temper (1/2H, 3/4H, H, SH, EH) at RFQ. Surface finish is bright-annealed or skin-passed for plating adhesion.
All grades supplied with confirmed mechanicals and surface quality per coil. Choose by terminal function (spring contact, general contact, shielding, heavy elastic), environmental exposure and required insertion life.
| Part type | Primary grade | Alternative grade | Selection criterion |
|---|---|---|---|
| High-cycle spring terminal | SUS301 SH | SUS301 EH | Contact force + insertion life ≥10,000 cycles |
| Medium-cycle terminal | SUS301 H | SUS304 1/2H | Spring-back + cost balance |
| Ultra-thin terminal (0.05–0.10 mm) | SUS301 SH | SUS301 EH | Thickness tolerance ±0.005 mm + high strength |
| USB / Type-C contact | SUS301 SH | SUS301 H | Tensile ≥1200 MPa + 10k cycle life |
| Corrosion-resistant terminal | SUS304 1/2H | SUS316 1/2H | Moist / outdoor / industrial environment |
| EMI shielding can | SPCC | SPTE (tinplate) | Deep drawability + magnetic shielding + cost |
| Connector housing / backshell | SPCC | SUS304 | Formability + plating + cost vs. corrosion |
| Relay reed / contact spring | 65Mn | C67S (EN) | Elastic limit + HRC 42–48 in dry environment |
| Heavy-duty connector contact | 65Mn | SUS301 SH | High contact force + cost (plated for corrosion) |
| Ground terminal / bus bar | SUS304 | SPCC (tin-plated) | Conductivity + corrosion + formability |
SUS301 temper designations (1/2H, 3/4H, H, SH, EH) correspond to increasing cold reduction and tensile strength. SH is the standard for connector spring terminals; EH is used for ultra-high-strength ultra-thin terminals. Confirm the exact temper and tensile range at RFQ — the stamping die and forming process are designed around the delivered hardness.
These are the failure modes that show up in connector production, in the order connector engineers care about them.
A terminal stamped from SUS301 that is below the SH tensile target (under 1000 MPa) loses normal force after a few hundred insertions, causing intermittent electrical contact. Fix: supply SUS301 with confirmed tensile per coil in the SH range (1000–1500 MPa), verified by tensile test on the MTC. We also confirm the hardness (HV) across the coil width so the stamping die sees consistent material from edge to center.
Terminal strip with thickness variation beyond ±0.005 mm changes the stamping die clearance, producing excessive burr on the terminal edge. A burr of 0.01 mm can prevent proper crimping or cause plating buildup at the edge. Fix: precision rolling with confirmed thickness per coil at ±0.005 mm (±0.003 mm on request), measured at multiple points across the width. We slit to exact width (0.5–5.0 mm) with controlled edge condition for high-speed stamping.
A terminal that develops plating blisters or poor coverage after tin or gold plating usually has residual oil, oxide or surface defects on the incoming strip. Fix: supply terminal strip with a bright-annealed or skin-passed surface, properly cleaned and oiled with a plating-compatible oil. We confirm surface quality per coil and can supply dry (oil-free) strip for in-line plating processes. The surface must be defect-free at the 0.05 μm gold plating level.
A terminal contact beam that fractures at the root after 2,000 insertions typically has a stress concentration from the stamping bend radius or a material surface defect. Fix: SUS301 SH with consistent tensile and ductility, clean shear edges from precision stamping, and a bend radius that matches the material's thickness and hardness. We confirm the strip's elongation and bendability per coil so the terminal maker can design the beam geometry within the material's forming limit.
Connector production draws on several steel families. Match your component below and confirm at RFQ.
SUS301 / SUS304 austenitic stainless for spring terminals, contact beams and connector housings with work-hardened strength and corrosion resistance. Stainless steel family →
SPCC / SPCD low-carbon cold-rolled strip for EMI shielding cans, connector brackets and backshells with deep-drawability and plating-ready surface. Cold-rolled family →
65Mn / C67S spring steel for relay reeds, heavy contact springs and elastic contact pieces at HRC 42–48 with high elastic limit. Spring steel family →
SAE1070 / SK5 high-carbon steel for heavy-duty contact springs and elastic terminals where maximum hardness is required in dry environments. High carbon family →
A typical USB Type-C receptacle spring terminal, described the way it runs.
The terminal is a stamped contact beam, 0.20 mm thick, 1.2 mm wide, with a 3.5 mm active beam length and a formed contact dimple at the tip. The drawing calls SUS301 stainless steel strip in SH temper, 0.20 mm, tensile 1200–1400 MPa, thickness tolerance ±0.005 mm, bright-annealed surface. The strip arrives slit to 1.5 mm width on a plastic core, is fed into a high-speed progressive die at 800 strokes per minute, and is blanked, formed and plated in-line. After stamping, the terminal receives a 1.5 μm nickel underplate and 0.2 μm gold flash on the contact area, with tin plating on the crimp tail.
The insertion life test is the moment of truth. The terminal is mated with a standard Type-C plug at 10 mm/s insertion speed, 10,000 cycles, with contact force measured every 500 cycles. A terminal that drops below 0.5 N normal force before 10,000 cycles fails — and the root cause is almost always incoming strip tensile below spec or thickness variation that changed the forming load. That is why the SUS301 strip's tensile and thickness tolerance are not optional: they are the difference between a 99.5% first-pass life test and a 80% pass rate with die rework. Our job is to make the strip's tensile, thickness and surface so repeatable that the stamping line's variables (die wear, plating bath chemistry, forming speed) are the only variables left.
The same connector uses a SPCC EMI shielding can, 0.25 mm thick, deep-drawn to a 9.0 × 3.5 mm envelope and tin-plated for solderability to the PCB. The shielding can's draw depth requires SPCC with confirmed elongation (≥38%) and a controlled r-value for earing control. If your connector program needs SUS301 for spring terminals, SPCC for shielding, SUS304 for housings, or 65Mn for relay reeds, send the terminal drawing and we confirm grade, temper, thickness tolerance and a trial-coil plan. Our slitting and processing services cover precision-width slitting (0.5–5.0 mm), cut-to-length sheets and edge conditioning for high-speed stamping.
Related reading: how surface finish and plating adhesion interact on stainless terminal strip, and precision steel strip buyer's handbook — thickness tolerance, slitting and surface quality. For a comparison of spring tempers, see spring steel standards and temper designations. Related application pages: home appliance components steel and power tool components steel.
These grade families share material, processing or application territory with the topic on this page.
SUS301 / SUS304 grades with work-hardened strength and corrosion resistance for spring terminals.
SPCC / SPCD grades with deep-drawability and plating-ready surface for shielding cans.
65Mn / C67S grades with high elastic limit for heavy-duty elastic contact pieces.
Send terminal drawing, thickness × width, temper / tensile target, plating spec, quantity and destination port. Our engineers reply within one working day with grade match and a trial-coil option.