Finger spring surface treatment methods

Surface treatment of a finger spring removes oil and scale and finishes the metal so the contact performs reliably and presents a consistent surface. The process is carried out in two steps: cleaning, which can be done in any of three ways, and glazing.

Step 1: removing oil and scale

Immersion. Dilute metal cleaning agent A with water in a plastic container at roughly 1:1 to 1:2 and immerse the springs until the metal returns to its natural colour and is free of oil and oxide scale. The soak time should not be excessive; rinse thoroughly with clean water afterwards. This method leaves a matt finish.

Vibratory polishing. Place cleaning agent A in a vibratory polishing machine or hexagonal drum together with coarse abrasive and the springs, using a spring-to-abrasive volume ratio of about 1:3 and about 1% to 2% cleaning agent by spring weight. After grinding and polishing, rinse with clean water. Surface scratches are removed and the finish improves. High-precision springs that are easily deformed during processing are not suitable for this method.

Ultrasonic cleaning. Use a cleaning-agent-to-water ratio of about 1:30 and clean until the natural colour of the metal returns and all oil and scale are gone, then rinse with clean water. This also gives the finger spring a matt effect.

Step 2: glazing

Place brightener B in a vibratory polishing machine or hexagonal drum with fine abrasive, using a spring-to-abrasive volume ratio of about 1:3 and about 1% to 2% brightener by spring weight; the longer the process, the brighter the result. After polishing, rinse and dry. The surface reaches a brightness comparable to nickel plating and does not fade.

About SISE

Dongguan Spring-in-Spring Electronics Co., Ltd. (SISE), established in October 2011 and relocated to Chang'an Town, Dongguan in May 2018, designs, tests and manufactures elastic conductive electronic components in a CNC lathe workshop, spring-finger workshop, assembly workshop and laboratory. Its spring contact fingers provide multiple columnar contact points (over 300), a service life of more than 100,000 cycles and an insertion force of about 10 N.