How to choose the right plating metal for electrical connectors?
Gold and tin are the most popular plating metals used in the connector industry.
Silver is an alternative plating metal, but the tendency to react with sulphur in the air and leaving a brown shiny surface, limits silver platings to power applications where cost is an key issue.
The real choice for the connector industry remains between gold and tin.
From a corrosion point of view, gold is the metal of choice, because it is the most inert material.
Tin may offer an important price advantage, but is not always the most efficient solution: In mated condition, tin has a maximum contact resistance expectation of less than 50 mΩ over lifetime, whereas gold has 20 mΩ. To achieve this, tin requires a contact normal force (CNF) of 2 N, while gold needs a CNF of 0,4 N. Tin’s higher CNF creates a higher mating force, which limites the number of contacts in the connector, as well as increase contact point wear when mating and unmating. Typically, tin plated connectors are not suitable for more than 50 mating cycles, on the other hand gold can support up to 500 mating cycles.
Another limitation of tin plated connectors is the use of unmated connectors in the field. In such conditions, tin oxide surfaces created over years in industrial atmosphere will not be broken through with a fresh mating connector. Tin connectors are not recommended in severe conditions of industrial atmospheres.
For that demanding connector industry, IONICS offers efficient electro-plating solutions that range from simple to very sophisticated:
| Plating metals | Metal substrates | Plating processes |
|---|---|---|
| Gold | Coppery | Barrel |
| Silver | Ferrous | Rack |
| Copper | Light alloys | Reel-to-reel |
| Nickel | ||
| Tin |
Despite, but probably also due to the global economic situation, the solar cell industry is still looking for efficient and cheaper solar cells. A roll-to-roll production would facilitate flexible photovoltaic modules and significant decrease the production cost for thin film solar cells. However, no standard processes for monolithic series interconnection on foil substrates are currently available at an industrial scale.
IONICS developed an insulating barrier layer by sol-gel technology, to allow monolithic series interconnection on electrically conducting substrates.
The developed insulating layer is a wet-chemically applied SiOx sol-gel. The coating can be applied on a large scale by cheap, non-vacuum roll-to-roll processes. Pinhole free coatings, prepared by spray and roll coating have been successfully achieved by IONICS customers. Breakdown voltages exceeding 1000 V have been achieved and electrical resistance of the barrier layer measured at 100 V reach values around > 108 Ω, which is too high to be measured with a multimeter.
