By Mike Carano, OMG Electronic Chemicals, LLC
With so many final finish options available, how do the PCB fabricator, designer and assembler reconcile the best option to insure long term solder joint reliability under lead-free soldering conditions? What finish or finishes are best suited for fine pitch BGA as well as through-hole assembly?
There are nine criteria that should be considered when selecting a final finish. These are:
- What is the ultimate reliability requirement for the PCB? Atmosphere, environment, etc.
- How many assembly cycles will the board (and surface finish) be subjected to?
- Is ICT important for the finish?
- Are cosmetics a key attribute?
- Does the PCB eventually require wirebonding?
- Product life of the circuit board?
- Equipment considerations for final finish processing
- Is shock/drop testing a concern?
- Overall cost of the finish in comparison with the total board cost and required functionality
Selecting a final finish for your printed circuit boards may be one of the most important decisions you will ever make. Certainly, one should not select a finish solely on cost or because one likes the “look” of the finish.