Overview

A custom copper probe spring is the compliant contact element inside a wafer probe card, IC test socket or fine-pitch connector, where a thin copper-alloy beam must press a pad with controlled force thousands of times without taking a permanent set. Photochemical etching forms the beam, the root fillet, the contact tip and any relief slots out of 0.05–0.30 mm beryllium copper, phosphor bronze or copper-nickel-tin sheet in one pass. Because no die touches the metal, the spring leaves the line flat, burr-free and free of the work-hardened edges that stamping would leave at the root, so fatigue life and contact resistance stay predictable.

For test and interconnect engineers, a custom copper probe spring is defined by three numbers: beam width, deflection and contact force, all of which trace back to alloy temper and etched thickness. Half-etching thins selected zones so the spring bends where intended while the tip stays stiff enough to scrub through surface oxide. The same film produces an entire array of contacts that etch at one rate, so force and geometry repeat from the first article to a production lot, and changing the layout means a new film rather than new tooling, which fits the short revision cycles of probe cards and sockets.

Parameter Window

• Available Materials: beryllium copper C17200, phosphor bronze C51000, copper-nickel-tin C72500, pure copper C11000, nickel silver
• Material Thickness Range: 0.05–0.30 mm, with locally half-etched beam zones
• Tolerance: ±0.015 mm on beam width, about ±10% of stock thickness on half-etched depth
• Minimum Feature: 0.06 mm beam width, 0.10 mm relief slot, 0.15 mm adjacent pitch
• Surface Options: nickel plating, gold plating, stress-relief anneal, anti-tarnish passivation, selective plating
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Convert the drawing to vector artwork, check beam width, root radii and deflection allowance, and confirm the panel orientation.
2. Material & Temper Selection — Set alloy, hardness and rolling direction to the contact force and life target, then verify flatness and thickness tolerance.
3. Cleaning & Lamination — Degrease and micro-etch, then hot-roll dry film matched to the narrowest beam so no bubbles sit under fine features.
4. UV Exposure — Expose both sides through high-resolution film with front-to-back fiducials registered so beams and tips stay aligned.
5. Development & Inspection — Wash out unexposed resist and check every panel for fully opened beams and any broken root fillets before etching.
6. Etching — Spray alloy-matched chemistry; time, temperature and conveyor speed set the sidewall, with half-etched zones stopped precisely.
7. Stripping & Heat Treatment — Strip and neutralize, apply a stress-relief anneal to restore spring temper, then plate nickel or gold locally if needed.
8. Inspection & Packaging — Measure beam width, contact force and plating against the approved sample, then pack in trays or on tape with a first-article report.

Core Advantages

1. No work-hardened root: Chemical removal leaves no stamped edge or micro-crack, so the beam keeps its temper through repeated flexing and lasts longer.
2. No hard tooling: A new part number is a new film, so prototypes take days and frequent probe-card layout changes carry no die cost.
3. Controlled contact force: Half-etching thins the beam to a precise depth, building deflection and force into the metal rather than relying on post-forming.
4. Complex beam shape in one step: Beams, fillets, contact tips and relief slots etch together, removing secondary machining and re-fixturing.
5. Full-panel consistency: Contacts on one sheet etch at the same rate, so width and force match within a lot and are held across lots by locked parameters.
6. Material and plating flexibility: Beryllium copper, phosphor bronze and copper-nickel-tin run on the same line, so a custom copper probe spring can be plated with nickel or gold to balance conductivity and wear.

Typical Applications

• Wafer probe cards: Compliant contact beams on probe cards, gold plated for low contact resistance across dense pad arrays.
• IC test sockets: Spring contacts in package test sockets, with half-etched zones giving stable travel and rebound.
• Battery contact springs: Battery terminals for rechargeable devices, where thin stock, high volume and consistent force all matter.
• Board-to-board connectors: Fine-pitch connector terminals whose 0.06 mm beams deliver enough normal force in a tight space.
• Flex circuit springs: Contact fingers on FPC stiffener regions, flat after etching so they do not lift adjacent traces when bonded.
• MEMS probe arrays: Micro-probe rows for MEMS testing, formed as a full panel so every needle carries equal force and height.

Design Notes & Process Considerations

1. Beam width versus thickness: Keep the narrowest beam at 0.06 mm or 1.2 × material thickness, whichever is larger, or it will fracture in etching or lose force.
2. Deflection and stress: State target deflection, cycle count and the stress-relief anneal condition; residual stress warps thin beams and drifts contact force.
3. Plating and wear: Give nickel or gold thickness and the underplate process; plating that is too thin wears through to copper after thousands of cycles.
4. Half-etch depth: Call out target depth and tolerance for thinned zones, typically 0.02–0.06 mm, and say whether etching is one- or two-sided.
5. Layout and grain direction: Run beams along the rolling direction for better fatigue life, use shared fiducials and leave enough etch and dicing allowance.
6. Drawing completeness: Put alloy, temper, deflection, plating and datums on the drawing in one pass; for a custom copper probe spring these six fields cut most of the back-and-forth.