PCB |
UL affirms acceptance of immersion<br>silver circuit board finishes
UL has announced revisions to its acceptance of printed circuit boards featuring immersion silver final finishes.
PCBs use immersion silver coatings to preserve the solder ability of copper conductors. This silver coating is specified in a wide array of electronics and is now used on more than 15% of all PCBs made in the world this year.
In the past, silver metal used in electronics was connected with electrochemical migration and dendritic growth failures. As a result, UL included a restriction in documentation regulating the use of silver.
As immersion silver grew in use in the mid 1990s, a group of scientists formed a committee to investigate electrochemical migration in more detail. This group found that silver was more vulnerable to electrochemical migration failures, but only when deposited as a thick, electroplated silver coating. Immersion silver was found to perform similarly to all other commonly used PCB finishes such as HASL, ENIG, OSP and Tin.
