Ideas & Solutions
Alternative PCB Finishes: Advantages and Disadvantages Comparison
In order to maintain the solderability of PCBs over a period of storage time, it is necessary to protect the copper surface mount pads with solderable surface finish. Up to now the most common finish is eutectic tin-lead alloy by hot air solder levelling (HASL) method because it has most desirable properties of ideal PCB surface. Unfortunately this coating does not meet requirement of soldering pads planarity – fundamental factor for fine – pitch, very large scale integration surface mount technology. There are over the dozen alternative PCB finishes on the market. All are useful for some applications, many of them provide much better planarity, but none really fit as "universal surface finish". Mike Barbetta has highlighted each of the common surface finishes (HASL, OSP, ENIG, immersion silver, immersion tin, electrolytic nickel-gold, electroless nickel/palladium/immersion gold, reflowed tin-lead, selective finishes) with regard to advantages and shortcomings.
- More about this you can find here (available for IPC members only).