Overview

A custom 301 stainless steel spring contact is a photochemically etched elastic terminal that delivers a stable normal force in board-to-board connectors, battery bays and EMI grounding. Type 301 stainless in spring temper is chosen because cold rolling lets a very thin section retain high elasticity and recovery without relaxing over time. Etching removes metal through a photoresist mask rather than punching it, so contacts leave the line flat and burr-free, without the work-hardening or root micro-cracks that stamping would leave in a 0.1 mm cantilever.

For an interconnect designer, a custom 301 stainless steel spring contact addresses three recurring limits: cantilevers that must hold uniform normal force on thin stock, fine-pitch arrays too dense for a punch die, and plating or mating surfaces that must survive tens of thousands of insertions without burrs scoring the counterpart. Geometry is defined by artwork, so a new contact layout is a new film rather than a new die. Supplied from 0.05 mm to 0.6 mm stock, contacts are usually nickel- or gold-plated to lower contact resistance and support soldering downstream.

Parameter Window

• Available Materials: stainless 301 (1/2H to full-hard spring temper), 304, beryllium copper, 316L on request
• Material Thickness Range: 0.05–0.6 mm
• Tolerance: ±0.02 mm on beam width, ±0.03 mm on outline profile
• Minimum Feature: 0.10 mm beam width and 0.10 mm gap at 0.15 mm stock
• Surface Options: passivation, electrolytic Ni/Au, bright anneal, stress-relief anneal, anti-oxidation coating
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork & DFM Review — Convert the contact drawing to vector artwork and confirm beam-to-thickness ratio, root radii and array pitch.
2. Material & Temper Selection — Match 301 lot, cold-rolled hardness and flatness to the normal-force and insertion-life target.
3. Cleaning & Lamination — Degrease and micro-etch, then laminate dry-film resist with no bubbles over fine beams.
4. UV Exposure — Expose both faces through registered film so beam outlines align to back-side thinning zones.
5. Development & Inspection — Develop the resist and inspect fine beams for pinholes before etching.
6. Controlled Etching — Spray-etch in stainless-matched chemistry; time, temperature and conveyor speed set sidewall and half-etch depth.
7. Stripping, Anneal & Plating — Strip resist, stress-relief anneal to stabilize force, then apply Ni/Au to the contact tips.
8. Force & Dimensional Verification — Measure beam width, force-deflection curve and flatness, then tray-pack or tape for automated placement.

Core Advantages

1. Uniform normal force: Chemical removal leaves no roll-over, so beam width and recovery match across the whole array.
2. No hard tooling: A new layout is a new phototool rather than a punch die, keeping low-volume programs affordable.
3. Crack-free roots: Etched beams carry no stamped-in micro-cracks, surviving tens of thousands of insertions.
4. Fine-pitch arrays: 0.10 mm beams with 0.10 mm gaps hold at 0.15 mm stock for high-density interconnects.
5. Low contact resistance: Spring-temper 301 with Ni/Au plating gives low, oxidation-resistant signal and power contact.
6. Batch repeatability: A custom 301 stainless steel spring contact from one approved film etches identically from first article to volume lots, simplifying qualification.

Typical Applications

• Board-to-board connectors: Elastic terminals in fine-pitch mezzanine and FPC connectors for reliable compression.
• Battery and charging contacts: Spring tabs in battery bays and charging docks that resist insertion wear.
• EMI fingers and grounding: Shield-can and chassis grounding springs that hold low-impedance contact.
• Tactile switches and keypads: Moving contacts in membrane and micro switches with crisp, long-life return.
• Antenna springs: Feed-point contacts in mobile devices that stay thin without losing RF contact.
• Test and programming fixtures: Elastic probe blades in ICT and programming jigs built for repeated compression.

Design Notes & Process Considerations

1. Beam width versus thickness: Keep the narrowest beam at 0.10 mm or 1.5 × material thickness, whichever is larger, to avoid root over-etch.
2. Root radii: Use internal radii ≥ 0.10 mm to reduce stress concentration and resist trapping at beam roots.
3. Half-etch depth: When local thinning is needed, state depth and tolerance — typically 30–60% of stock — together with beam width.
4. Force and deflection: Specify target normal force, working compression and insertion cycles so temper and anneal are chosen correctly.
5. Plating specification: State nickel underplate and gold thickness and confirm the contact tip is fully covered.
6. Panelization and marking: Group contacts on a shared registration grid with orientation marks to speed automated placement.