Overview

Probe spring etching uses photochemical machining to produce micro contact springs for test probes, pogo pins and socket contacts, where the spring must be small, flexible and repeatable. The spring profile — the coils, arms or folded beams — is defined by a resist pattern and cut from thin metal by dissolution, so there is no stamping stress, no burr and no tool wear on the spring surface. This lets a probe spring hold a precise free length, tip geometry and spring rate at scales where a die cannot form reliably.

The controlling properties are spring force and fatigue life. The spring must deliver a consistent contact force over thousands or millions of compressions without taking a permanent set or breaking, while the tip stays sharp enough to penetrate oxides on the device under test. Probe spring etching runs beryllium copper and stainless steel from 0.02 mm to 0.3 mm thick, and because the shape is artwork-driven, tip shape, coil count and force can all be tuned between prototype and production without new tooling.

Parameter Window

• Available Materials: beryllium copper (C17200), stainless steel 301/304, phosphor bronze
• Material Thickness Range: 0.02–0.3 mm
• Tolerance: profile ±0.02 mm, tip width ±0.01 mm
• Minimum Feature: tip and arm width down to 0.05 mm
• Surface Options: nickel underplate, gold or rhodium plating, passivation
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Spring Design Review — Convert the probe spring profile to vector artwork and confirm free length, tip shape and target force.
2. Material Selection — Choose beryllium copper for conductivity or stainless for corrosion, at the required temper and thickness.
3. Cleaning & Lamination — Degrease the strip and laminate dry film resist without bubbles over the fine spring features.
4. UV Exposure — Expose the spring profile through film with registration to the strip edge for repeat pitch.
5. Development — Wash out unexposed resist and inspect tips and arms for residue or under-development.
6. Etching — Etch with matched chemistry, controlling undercut to hold tip width and arm width precisely.
7. Stripping & Plating — Strip resist, neutralize, then apply nickel underplate and gold or rhodium finish.
8. Inspection & Packaging — Measure tip width, free length and plating, test force and fatigue on samples, then pack in trays or reels.

Core Advantages

1. Stress-free spring material: Chemical removal leaves the spring zone free of stamping stress, so the spring rate stays true.
2. Controlled tip geometry: Fine tips down to 0.05 mm are held sharp and uniform for reliable oxide penetration.
3. Repeatable spring force: Uniform cross-section and clean edges give a consistent contact force from spring to spring.
4. High fatigue life: Burr-free, stress-free springs withstand millions of cycles without taking a set or fracturing.
5. No tooling: Tip shape, coil count and force change with the artwork, not with a new die.
6. Micro-scale capability: Springs too small to stamp are produced with consistent, fine features.

Typical Applications

• Test probe springs: Contact springs for wafer and ICT test probes.
• Pogo pin springs: Micro springs inside pogo pins for board test and docking.
• Socket contacts: Spring elements for IC sockets and burn-in sockets.
• Switch and relay springs: Precision flexing elements with controlled force.
• Battery contact springs: Etched springs for cell and module connections.
• Medical probe contacts: Small, precise springs for diagnostic devices.

Design Notes & Process Considerations

1. Tip width versus thickness: Keep the tip near 1× thickness or greater so it penetrates without buckling or bending sideways.
2. Force specification: State the working force at a given deflection so arm width and length can be sized.
3. Material and temper: Specify beryllium copper or stainless and the temper, since it sets both force and fatigue life.
4. Plating: Name nickel underplate plus gold or rhodium, with thickness, to keep contact resistance low and stable.
5. Free length tolerance: Call out the free length tolerance, as it directly controls the assembled preload and force.
6. Fatigue cycles: Give the expected compression cycles so the material and geometry are matched for endurance.