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Tented vias on ENIG boards

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John S.

#39407

Tented vias on ENIG boards | 31 January, 2006

We're looking at lead free surface finishes for some of our products. On one supplier's site, I found a note that tenting vias on ENIG boards can lead to the black pad phenomenon. How does this compare to your design guidelines and experience? Thanks, John S.

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RDR

#39409

Tented vias on ENIG boards | 31 January, 2006

I have never related Solder mask layout to Black Pad. I don't see how they could be related but.......

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Chunks

#39429

Tented vias on ENIG boards | 1 February, 2006

Can you post the site where you saw this? I've never heard of such a thing.

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John S.

#39451

Tented vias on ENIG boards | 1 February, 2006

http://www.saturnelectronics.com/docs/Getting_the_Lead_Out.pdf

This is a document provided by one of our suppliers discussing lead free PCB considerations. Within the document, it mentions black pad being associated with tented vias. Thanks John S.

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RDR

#39454

Tented vias on ENIG boards | 1 February, 2006

Yes it does doesn't it! I wonder how this can cause black pad. Can you contact Saturn and ask them specifically? I browsed other PCB MFGrs. for this type of info and cannot find anyone else who claims this.

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Chris

#39464

Tented vias on ENIG boards | 1 February, 2006

I wonder if they are concerned about getting chemicals trapped in the tented vias. If the tented vias have pin hole openings or even larger openings, chemicals from the ENIG process could become entrapped in the via holes and not washed away in the rinse process. This would cause corrosion in the via hole or even leak out onto the SMT pad.

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Cmiller

#39518

Tented vias on ENIG boards | 5 February, 2006

We have been using ENIG for 8 years as our primary board finish. We have not seen any issues with tenting the vias. We have used a number of suppliers. The ENIG from China does not seem to solder quite as well in general but only had black pad from one supplier and they were outsourcing the gold plating so the Nickel was exposed to the atmosphere for sometimes 3 to 4 days before gold was put on. When we sourced it, they told us the did it in house. They were in Chicago. Saturn is one of our larger suppliers, have never had issues with thier ENIG. If no one beats me to it I will call Yash and find out the issue with the tented vias.

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Yash Sutariya

#39529

Tented vias on ENIG boards | 6 February, 2006

Sorry. I actually should clarify those slides. Black pad is not associated with tented vias. Also, you can tent vias with soldermask, but this requires the immersion gold process to be completed prior to soldermask. As such, all copper features (traces, pads, etc.) will be covered with immersion gold. This, in turn, reduces the soldermask adhesion and may result in some soldermask flaking off. However, reliability will not be affected as the underlying features are protected from oxidation by the immersion gold. Feel free to call (734-941-8100) or email (ysutariya@saturnelectronics.com) with any additional questions or concerns. Thanks!

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RDR

#39532

Tented vias on ENIG boards | 6 February, 2006

Thanks Yash!

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