PCB (Printed Circuit Board) is responsible for loading and connecting electronic components in electronic equipment in order to implement electronic circuit function. For PCBA (Printed Circuit Board Assembly), electric connection between components and circuit on PCB mainly lies in tin plating or wire bonding and rarely in plug-in and fastening connection. In order to assemble connection in PCB design, pad or land is designed. To easily and reliably implement electric connection between pad or land and components, surface finish has to be laid on the surface of pad or land in the PCB manufacturing process, which aims to stop copper from oxidation or deterioration and to provide surface that's convenient for tin plating bonding and wire bonding.
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