Tin or tin alloy material is an excellent terminal electroplating material, relatively low cost, low contact resistance, good solderability, performance in the corresponding use environment can also meet the requirements of engineering design, is an ideal coating material to replace gold and other precious metals.
Necessary requirements for terminal tin plating
Blog | Nov 01,2021
Tinned material must ensure good mechanical stability of both positive and negative terminals after insertion. That said, canning terminal materials are not recommended in vibration environments. The reason: Under the vibration environment, the terminal metal material differential thermal expansion coefficient (DTE) is different, easy to produce Fretting corrosion (Fretting corrosion), generally the terminal will be in the range of 10~200 micron reciprocating friction resulting in coating damage. The raw material is exposed to oxidation, resulting in a significant increase in contact resistance.
In order to maintain stable contact between tin terminals, positive pressure of at least 100 g or more should be applied to the terminals. Auxiliary lubrication is required between tinned terminals. Reason: This is the second one above, the positive pressure of the terminal is very high and needs proper lubrication, the best male end lubrication, the smallest end lubrication.
Tinned material is not recommended for continuous high temperature rings. Cause: The high temperature produced accelerates the brittle middle layer of intermetallic compounds between copper and tin and lead, affecting normal use. An intermediate layer of nickel is recommended because of the slower growth rate of nickel tin intergeneric compounds.
Various tin plating processes do not have a great difference in electrical performance. For example, bright tin plating is more beautiful; The surface of matte tin should be kept clean so as not to affect weldability. Brass, tin should be added to nickel, which is used to prevent the loss of zinc substrate in the underlying layer, as zinc loss can lead to reduced weldability.
Tin plating thickness should be 100 to 300 microinches. Less than 100 will be mainly used for products with low cost and low weldability requirements. Tin-plated and gold-plated terminals are not recommended. The reason: because it will be easier to do so corrosion oxidation. The tin will be transferred to the gold surface, which will eventually result in the accumulation of tin-plated oxides on the harder gold-plated substrate. Hard tin oxide is more difficult to pass through tin oxide from tin without direct destruction. However, the fretting friction conditions of tin-plated and silver-plated pairs are similar to those of tin-plated pairs.
Tinned terminals with each other, it is best to plug two or three times. The purpose is to remove the oxide layer from the tin coating and to achieve reliable metal-to-metal contact. Tinned or tinned alloy terminals are not suitable for frequent on-off of circuits. Tin has a low melting point and is not suitable for frequent switching, such as from the contact point of the arc. Canned terminals are suitable for drying circuits and applications where requirements are not very high.
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