3. Surface coating
Tin plating is a relatively common electroplating process currently used in connectors. This process has the following disadvantages:
First, heating the tin coating to a high temperature or storing it for a long time (even at room temperature) will result in reduced solderability and increased contact resistance. This phenomenon mainly stems from the maintenance of intermetallic compounds between the coating and the base metal.
Secondly, the contact material of the connector plating layer is more frictional than the metal plating, which leads to an increase in the insertion force of military power connectors. This defect is especially obvious in the use of multi-wire connectors.
So for the plating of multi-line connectors, choose some new plating processes as much as possible. While achieving connection transmission, reduce the insertion force of the connector. For example, the current gold plating process is a relatively good plating process. Sunkye has gold plated connectors for sale, contact us for more info.
From the point of view of micro-physics, the surface of any smooth-looking object is rough and uneven, so the contact surface of automotive terminals is not a surface contact, but a point contact. In addition, the general metal surface is covered with non-conductive oxide film and other types of film layers, so in the actual contact surface, only a small part of the film layer can be crushed or voltage breakdown. And only these places can realize the real electrical contact. These contact points are called "conductive spots".
Most of the contact is through the film layer. Therefore, when the current passes through the interface of the two contacts, the current will concentrate through the extremely small conductive spots, so the current line near the conductive spots will inevitably shrink. This also causes the current line to shrink in the vicinity of the conductive spot, increasing the length of the path through which the current flows, and the effective conductive area is reduced, so a local accessory resistance appears, called "shrinkage resistance." Increasing the surface finish of the terminal can also improve the transmission performance of the terminal.
For now, the standards for inspecting the coating quality are:
① Check the thickness of the coating. This method judges the quality of the coating by controlling the thickness of the coating.
② Check by corresponding salt spray experiment
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