Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


White Tin

Frank Boyko

#11678

White Tin | 27 April, 1999

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?

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Justin Medernach

#11679

Re: White Tin | 28 April, 1999

| 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

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Frank Boyko

#11680

Re: White Tin | 28 April, 1999

| | 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?

reply »

Justin Medernach

#11681

Re: White Tin | 28 April, 1999

| | | 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? | | Frank, Sorry, you caught me. I meant to mention exposed nickel on the immersion gold process instead of exposed copper. Nickel oxidizes readily in the ambient and causes all the solderability problems. I am unaware of anyone running a no clean process on the white tin finish. I'll check around in my pipeline and see if anyone has seen it. Check with your paste supplier and find out if the flux system that you use will handle a white tin finish. You may even be able to get them to run a study.

thanks, Justin

reply »

Charles Stringer

#11682

Re: White Tin | 30 April, 1999

| | | | 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? | | | | | Frank, | Sorry, you caught me. I meant to mention exposed nickel on the immersion gold process instead of exposed copper. Nickel oxidizes readily in the ambient and causes all the solderability problems. I am unaware of anyone running a no clean process on the white tin finish. I'll check around in my pipeline and see if anyone has seen it. Check with your paste supplier and find out if the flux system that you use will handle a white tin finish. You may even be able to get them to run a study. | | thanks, | Justin | We evaluated dexter tin with our no clean process and binned it as a no-no on through hole component soldering. Surface mount seemed Ok though. For the moment on the odd board where we require really flat finish on boards we use gold over nickel. Just make sure your PCB shop does it on a continuous basis and doesn't just fire up the bath for your few specials!

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