PCB surface coating (plating) coating is an important part of printed board manufacturing. It is related to the solderability, reliability service life of PCB. It must be given full attention, especially according to the application situation application field. Judge choose. Fully understand the type of surface coating (plating) coating its application effect overview, choose according to application requirements application fields.

Due to the mutual diffusion between the gold-copper interface to form a fragile connection the solder copper interface to form a "temporary state" CuxSny intermetallic compound (IMC) welding layer, these will affect the high reliability long product application Service life. In order to eliminate reduce these failures, a barrier (isolation) layer must be used between copper solder, which can prevent the gold-copper atoms diffusing with each other the CuxSny intermetallic compounds that produce "temporary state" It also provides solderability. This means that the connection between the pins of the component the solder pad of the printed board is soldered together with the solder in the barrier (isolation) layer, thereby eliminating gold-copper mutual diffusion copper-tin ( solder ) CuxSny intermetallic compounds hidden problems.

Since the characteristics application effects of various surface coatings (plating) are different, they should be selected according to application requirements application fields, cannot be based on manufacturing difficulty cost.

General principles: (1) For civilian industry, conventional industry, etc., choose the type of products coated with (plating) coatings without welding on the "barrier layer", such as high temperature type organic solderability protection agent (T -OSP), etc .;

(2) For the application areas of high reliability long service life key department equipment, facilities, instruments, such as medical equipment, transportation (high-speed rail, automobiles, etc.), national defense military equipment, aerospace equipment other important fields, The product of the surface plating layer welded on the "barrier layer" should be selected. At least the surface plating layer of electroless nickel-gold should be used. Of course, it is recommended to use electroless nickel-palladium-gold electroless nickel-palladium. electroless palladium plating. pcb customization

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