surface finish question

[popoyboys]

May i know how to choose what type of surface finish to be used in pcb designs?

 

[marce]

ENIG or ENIPIG,
ENIG is one of the most widely used currently if not currently No1), it has one of the longest shelf life, flat surface and minimal problems, I have sourced lots (6 figure) boards direct from China and Europe with ENIG and never seen black pad or had any processing problems both with leaded and lead free soldering processes, re-flow, wave and selective soldering.
Due to the increase in the price of gold and the relative cost of palladium ENPIG is becoming a popular choice.
There are other finishes, that I have investigated that had to many disadvantages for my requirement, one of the main ones being storage conditions. The more exotic finishes put a lot of onus on well controlled storage requirements, that if not followed can have a great impact on solderability and long term reliabity.
Plent of info out there, including white papers on the IPC site. Here is a little selection to WET your appetite, and hopefully your joints:
Printed Circuit Design & Fab Magazine Online
Printed Circuit Design & Fab Magazine Online
Printed Circuit Design & Fab Magazine Online
Printed Circuit Design & Fab Magazine Online
Printed Circuit Design & Fab Magazine Online
Printed Circuit Design & Fab Magazine Online
Printed Circuit Design & Fab Magazine Online
Printed Circuit Design & Fab Magazine Online

 

[taisen]

The question you first have to ask yourself is what type of process this PCB will see during assembly. If you are going to be wire bonding then ENIG would not be the way to go. That would be things to consider. If it is just a basic PCB assembly then ENIG would be the cost effective way to go.

 

[marce]

ENIPIG is suitable for wire bonding. Think ENIG with a bit of palladium