| | We use Immersion Gold (AuNi) for our 20 mil pitch and BGA boards. | | Lately, we have been having solderability problems with boards with this surface from some of our suppliers. | | | | We are considering trying boards with White Tin solderable surfaces such Dexcoat or Omikron. | | | | Does anyone have experience with this type of board coating? | | | Hi Frank! | Long time, no chat. Hope all is going well for you. Recently, I processed several hundred boards with the Omikron coating. I loved the stuff. It soldered great but we used an RMA process. I'm not sure how the no-clean you are currently using would handle the tin. You would certainly have to run a qualification. Also, there have been concerns about long term reliability of the white tin coating. It is certainly a viable solution to your problems with the gold but it may introduce a whole new slew of issues. Immersion gold can yeild a decent process. The problem with it is the deposition thickness. Beat up on your supplier and have them tighten their inspection procedures. Specify that you want a coating thickness measurement for one out of 5 boards until you have confidence in their process. This is a way to get to where you should be. Typically, when you see solderability issues with gold, the coating is not there and you're left with bare copper. Too much gold and you would notice it on the discrete components. The solder joints will look very dull. You might want to check into your profile as well. Immersion gold always requires a jumped up reflow temperature. Bottom line: Run an eval lot with the white tin coating. See if you like it but don't discount the gold. Seems more like a supplier issue to me. | | Regards, | Justin |The controls you describe are not practical for a small producer. We qualified a supplier and his process. Things went well for a year and then went to pot when the supplier changed his process without telling us. The suppliers with tight processes have higher quantity requirements than we need.
Also, we have seen problems with the nickel surface and with the gold surface but not with the copper surface as you mention. The immersion gold process can go bad at a lot of points!
White tin seems atractive because it is a simpler process than immersion gold. Clean the copper, put it on, rinse.
Has anyone tried it with no-clean solder paste?
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