JohnG300c
Advanced Member level 4
enig black pad
I'm in the process of choosing a surface finish for my latest PCB. The smallest pitch is 0.5 mm (FPGA in 208 PQFP). I have narrowed down my choices to two:
1) ENIG (Electroless Ni, immersion Gold): Apparently a tricky manufacturing process or else i'll end up with the black pad issue.
2) DIG (Direct Immersion Gold): Simpler manufacturing but may start to corrode after 4-6 months (not really an issue in my case since the boards will go to production pretty much right away).
I'm leaning towards DIG. Questions:
a) Does anyone have real-world experience with DIG?
b) Is this finish common in China (where i will manufacture the PCB)?
c) Is the ENIG finish really suffering from black pads these days?
d) In general, what is the price difference between ENIG and DIG?
I have also seen references to immersion silver and tin but corrusion problems (silver) and growing whiskers (shorts for tin) makes these less interesting. These are not high-volume boards (100+ per year perhaps) so the pricing difference perhaps really doesn't matter (unless it is large).
I'm in the process of choosing a surface finish for my latest PCB. The smallest pitch is 0.5 mm (FPGA in 208 PQFP). I have narrowed down my choices to two:
1) ENIG (Electroless Ni, immersion Gold): Apparently a tricky manufacturing process or else i'll end up with the black pad issue.
2) DIG (Direct Immersion Gold): Simpler manufacturing but may start to corrode after 4-6 months (not really an issue in my case since the boards will go to production pretty much right away).
I'm leaning towards DIG. Questions:
a) Does anyone have real-world experience with DIG?
b) Is this finish common in China (where i will manufacture the PCB)?
c) Is the ENIG finish really suffering from black pads these days?
d) In general, what is the price difference between ENIG and DIG?
I have also seen references to immersion silver and tin but corrusion problems (silver) and growing whiskers (shorts for tin) makes these less interesting. These are not high-volume boards (100+ per year perhaps) so the pricing difference perhaps really doesn't matter (unless it is large).
