How to clean and brighten spring finger contacts

The appearance of a finished spring finger depends on proper surface treatment. This guide covers two steps: removing oil and scale from the spring, and then brightening it to a stable, nickel-like finish.

Step 1: remove oil and scale

Method 1, immersion. Immerse the spring in a plastic container of metal cleaning agent A diluted with clean water (cleaning agent to water roughly 1:1 or 1:2). Soak just until the surface is free of oil stains and oxide scale and the metal appearance is restored; do not over-soak. Remove and rinse with water. This method leaves the contact spring with a matt finish.

Method 2, mechanical finishing. Place the spring in an oscillating finishing machine or hexagonal drum with coarse abrasive, with cleaning agent A. Use a spring-to-abrasive volume ratio of about 1:3 and a cleaning-agent quantity of 1%-2% of the spring weight. After grinding and polishing, rinse with clean water. Surface scratches are removed and the surface finish is improved. High-precision springs that are easily entangled are not suitable for this method.

The first two methods can both be applied to high-precision springs.

Method 3, ultrasonic cleaning. In ultrasonic equipment, dilute the cleaning agent with clean water at about 1:30. Treat until the spring is free of oil and oxide scale and its metal nature is restored, then remove and rinse with clean water. This gives the spring surface a matt effect.

Step 2: brighten the spring

Place brightener B in an oscillating polishing machine or hexagonal drum with fine abrasive (spring-to-fine-abrasive volume ratio about 1:3; brightener B about 1%-2% of the spring weight; a longer cycle gives a brighter result). After polishing, remove, rinse with clean water and dry. The finished spring finger has an appearance like nickel plating and will not fade.

Company profile

Dongguan Spring-in-Spring Electronics Co., Ltd. (SiS) was established in October 2011 and specializes in the design, testing and manufacturing of spring fingers and high-current connectors. The company moved to Chang'an Town, Dongguan in May 2018 and operates CNC lathe, spring-finger, assembly and laboratory workshops.

Based on rising industry requirements for high-current connectors, Spring-in-Spring Electronics developed a new type of bidirectional coil spring contact finger (SiS) and a single-turn spring finger, forming an array of deformation contact points of up to more than 300 points. They meet a service life of more than 100,000 insertion cycles; current density and temperature rise are close to those of the transmission cable, and single-turn plugging force is about 5-10 N.

Products include PCB-board connectors (board-to-board USC and board-to-wire), cylindrical quick-swap self-locking connectors with plastic and metal shells, male and female weight-load connectors, electric-vehicle chargers and high-voltage power-battery-pack series connectors. These are used in advanced high-current energy collectors and energy-storage and electrical equipment such as electric vehicles, charging base stations, wind-energy generators, power supplies, high-speed rail and heavy trucks. The company holds a number of national invention and utility-model patents, and its products have passed international-standard testing.