What is Immersion Silver?

Immersion Silver is a method that applies a lead free layer of silver onto a PCB, to protect copper traces from corrosion. Silver surface finish has excellent solder-ability comparable to solder plating, as well as moderately long shelf life, though still less than some of the other finishes. It is a popular choice due to silver being the most electrically conductive metal available, and ideal for high-speed signals. Silver surface finish can be applied to copper traces with an electroless immersion reaction, displacing the copper layer. The application process for this surface finish forms a very flat surface, which is advantageous for SMD assembly. Silver immersion is a surface finish with benefits that far outweigh its costs, and thus it has gained widespread popularity since the RoHS and WEEE directives came into effect; however, silver immersion is not without its drawbacks. Silver is sensitive to contaminants, both in the air and on the board, and thus it should be packaged as soon as possible to prevent tarnishing.See below figure 1

Figure 1:Example of Silver Immersion Surface Finish 

Pros

• RoHS complaint

• Planar

• Fine pitch

• Cost-effective

• A good alternative to ENIG

• High stability 

Cons

• Tarnishes 

• Silver Whiskering

• Some Systems Cannot Throw into Micro-Via Aspect Ratios of > 1:1

• High Friction Coefficient/Not Suited to Compliant-Pin Insertion (Ni-Au Pins)

We at Hopetimepcb offer Immersion Silver as a standard surface finish option, with a standard price,meaning no additional cost will be applied for selecting this finish.


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