Overview

An OEM connector terminal photo chemical etching service forms contact springs, socket arrays and leadframes from thin copper-alloy strip in a continuous reel-to-reel chemical process rather than by progressive-die stamping. Photoresist is coated on both faces, the spring outline and gaps are exposed and developed through film, and the unprotected metal is dissolved in a matched etchant, so fine contact fingers, locating holes and carrier borders all form together. Because removal is chemical and reel-to-reel, parts leave the line burr-free with no residual stamping stress, so spring-back and temper stay uniform, which is essential for fine-pitch, high-mating-cycle connectors with selective plating.

For sourcing engineers, this precision etching process solves three limits of stamping: below 0.5 mm pitch, thin die-stamped fingers deform, tooling wears fast and revisions are expensive; stamping burrs scratch the plating and the mating flexible cable, cutting insertion life and causing intermittent contact; and machining cannot hold pitch and flatness across large irregular arrays. With geometry held in the film, a new part number is only a new artwork, and volume runs pair continuous etching with selective gold plating so pitch, spring force and coating thickness stay consistent from sample to mass production.

Parameter Window

• Available Materials: phosphor bronze C51900/C52100, beryllium copper C17200, brass, stainless 301/304, nickel silver
• Material Thickness Range: 0.08–0.8 mm
• Tolerance: ±0.02 mm on contact profile, ±0.03 mm on pitch
• Minimum Feature: 0.10 mm line and 0.15 mm gap, 0.20 mm contact finger at 0.15 mm stock
• Surface Options: selective hard/soft gold, tin, nickel underplate, reel-to-reel plating, passivation
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Convert customer files to vector outlines, check finger width, gap and pitch against stock thickness, and set carrier border positions.
2. Strip Selection — Choose phosphor bronze or beryllium copper by spring force and mating life, unwind and level the coil, and inspect for scratches.
3. Cleaning & Coating — Degrease and de-oxidize, then coat photoresist on both faces with thickness matched to line width so no bubbles sit under fine fingers.
4. Reel-to-Reel Exposure — Expose both sides continuously through high-resolution film with front-to-back registration so fingers and holes stay concentric.
5. Development — Wash away unexposed resist to open the metal to be removed, and rework any gap still showing residual resist.
6. Etching — Spray chemistry matched to the alloy; time, temperature and line speed govern the photo chemical etching of the spring profile across the whole coil.
7. Stripping & Plating — Remove resist and neutralize, then apply selective gold, tin or a nickel underplate, and anneal to restore spring temper where needed.
8. Inspection & Packaging — Verify pitch, spring force, flatness and plating against the approved sample, then rewind or pack on carrier tape with first-article data.

Core Advantages

1. Burr-free edges protect plating: Chemical removal leaves no roll-over, so terminals never scratch the mating flexible cable or their own gold layer during insertion.
2. Uniform spring force: No stamping hardening or residual stress is introduced, so spring-back and contact pressure stay consistent across a batch.
3. Fine pitch without dies: Finger arrays below 0.5 mm pitch form in one pass; a new part number is just a new film, keeping prototypes and short runs economical.
4. Reel-to-reel throughput: Whole coils are etched and plated continuously, suiting high-volume arrays and lowering unit cost over length.
5. Selective plating saves gold: Gold is placed only on the contact zone while non-contact areas keep base metal or tin, cutting precious-metal use.
6. Mixed layouts on one coil: Several terminal types share registration marks on a single strip, reducing handling and cost without separate tools.

Typical Applications

• Board-to-board springs: Fine-pitch contact fingers inside phones and modules, with stable force and selective gold plating.
• FPC/FFC socket terminals: Elastic contacts for flexible-cable connectors, burr-free so insertion never damages the cable.
• Automotive harness terminals: Tinned spring contacts for vibration-prone environments with heat and mating-cycle requirements.
• Medical device contacts: Low-resistance gold-plated touch points for probes and pluggable modules where signal integrity matters.
• RF shielding fingers: Grounding spring arrays between housings and lids, uniformly etched for continuous shielding.
• Battery socket spring pins: Elastic contacts in portable devices, reel-to-reel built for large-batch consistency.

Design Notes & Process Considerations

1. Finger width versus thickness: Keep the narrowest finger at least 1.2 × stock thickness, or undercut thins it and spring force or fatigue life suffers.
2. Pitch and gap: State center pitch and minimum insulating gap; too small a gap invites solder bridging after etching and plating.
3. Plating stack: Specify nickel underplate thickness, gold hardness and thickness, and the selective plating zone; hard gold on contacts extends mating life.
4. Force and mating life: Give target contact force, deflection and insertion cycles, and leave fatigue margin in the alloy choice.
5. Flatness and burr: Call out flatness per 100 mm for SMT or tape-packed terminals and require burr-free edges.
6. Complete drawing data: Put alloy temper, pitch, plating and coil width on the print together to cut back-and-forth confirmation.