Immersion Tin VS Immersion Silver VS HASL
Lead-Free HASL is similar to standard HASL, but with an obvious difference… It doesn’t use Tin-Lead solder. Instead, Tin-Copper, Tin-Nickel or Tin-Copper-Nickel Germanium may be used. This makes Lead-Free HASL an economical and RoHS compliant choice. But like standard HASL it is not ideal for smaller components.
Immersion silver is a non-electrolytic chemical finish applied by immersing the copper PCB into a tank of silver ions. It is a good choice finish for circuit boards with EMI shieldingand is also used for dome contacts and wire bonding. The average surface thickness of the silver is 5-18 microinches.
Comparison With These Surface Finishes
·The features of immersion silver as surface finish place it in between OSP and immersion gold. Even when exposed to humidity, heat, and pollution, immersion silver continues to provide good solderability and electrical connection, although it will tarnish. Immersion gold has a layer of nickel under it, which provides it with physical strength. As there is no nickel layer under immersion silver, its physical strength is lower than that of immersion gold.
·Immersion silver requires more care for storage and handling than immersion tin does. However, immersion silver is safer for the environment than immersion tin is.
·Immersion silver is easier to use compared to Organic Solder Preservative or OSP is.
·Immersion silver offers a more planar surface than HASL does.
It is important to select the appropriate surface finish for your project by considering the various options while factoring in performance requirements and material costs.