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PCB with ENIG plating shelf life?

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Hello all, Can anyone advise if any standard covers ENIG pla... - Nov 07, 2022 by Evtimov  

#88599

PCB with ENIG plating shelf life? | 7 November, 2022

Hello all, Can anyone advise if any standard covers ENIG plated boards shelf life? Or share what you do for bare boards storage and expiration criteria?

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#88601

PCB with ENIG plating shelf life? | 9 November, 2022

ENIG boards have low shelf life as oxidation starts showing up quickly on the solderable areas. We usually keep them vacuum packed till they are ready to be assembled. Most PCB manufacturers will send them vacuum packed.

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#88602

PCB with ENIG plating shelf life? | 9 November, 2022

If they are vacuumed and they approach 6months or 1 year mark, what would you do?

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#88605

PCB with ENIG plating shelf life? | 10 November, 2022

Probably preform some sort of solderability evaluation on the PCBs.

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#88607

PCB with ENIG plating shelf life? | 10 November, 2022

The G in ENIG is gold. It does not oxidise. Either you are thinking of OSP or your board shop is providing defective boards if your boards show oxidation. It would be the nickel that is oxidising but should be totally covered by the gold.

Is there a shelf life for ENIG? Keep moisture out and they store well a long long time. Why else use something as expensive as gold?

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SMTA-64386598

#88609

PCB with ENIG plating shelf life? | 10 November, 2022

The solderability shelf life of ENIG is related almost entirely to diffusion of O2 through the gold plating. When O2 diffuses through the gold, the underlying nickel is oxidized rendering it unsolderable (with ENIG - you solder to Ni, the gold dissolves in the solder joint). Gold plating has a level of porosity that is unavoidable. Thicker Au has less porosity and this helps (but with obvious tradeoffs I won't discuss here). But O2 diffuses through Au. The only ways to slow it down are by a) eliminating the O2 and/or b) reduce the temperature (not a very good storage solution) significantly which would slow the diffusion of O2 through the Au. Typical ENIG will achieve a 2-4 year solderability shelf life in standard storage conditions, but may last quite a bit longer. Typical guaranteed solderability for ENIG is only 1 year.

This message was posted via the Electronics Forum @ SMTASMTA

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#88610

PCB with ENIG plating shelf life? | 10 November, 2022

So if you stored them in a nitrogen cabinet then you would reduce the O2 diffusion as well as keep moisture out of the boards.

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#88618

PCB with ENIG plating shelf life? | 11 November, 2022

SMTA-643865, this is great information. I recently found online IPC1601 table saying 12months + . I was wondering what the + means? My company wants to scrap ENIG boards for 20k just because they hit the 1 year mark. Boards are perfectly sealed, so I wander what can I do to save them? Also around these lower temp solution, should I put them in a fridge or freezer? what would this temp be?

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#88621

PCB with ENIG plating shelf life? | 11 November, 2022

I would certainly test the boards but from our experience, the vacuum sealed in room temp, no issues at all with our PCBs sourced from Suntak / PCB Founder / Fastprint / Yaxinda / JLCPCB well past the 12 month mark. We building boards purchased 5-10 years ago that have been vacuum sealed and no issues to solder to these boards.

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#88622

PCB with ENIG plating shelf life? | 12 November, 2022

Thank you Stephen... I also mistaken it with Immersion Silver.

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#88628

PCB with ENIG plating shelf life? | 14 November, 2022

kumarb would you just check PCBs for solderability or would you do something in addition?

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#88634

PCB with ENIG plating shelf life? | 15 November, 2022

Yes, solderbility. I recall one case of a vendor we met at a past HK electronic fair. Pricing was ok, we selected them and ordered a batch of boards. After a few months of leaving the PCBs in a sealed package (vacuum), we attempted to use the PCBs. We could not solder to the surface even if we used a blow torch. Total scrap. Needless to say, never worked with that supplier again. I think you should find that your PCBs will be ok if the vendor is a solid one like the names dropped already. There are apparently 20k+ PCB suppliers in Asia. Many are front companies for others as the equipment can be expensive.

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#88640

PCB with ENIG plating shelf life? | 16 November, 2022

" so I wander what can I do to save them?" The boards or management?

Seriously I think this is more of a management issue than a technical issue. We can suggest what to do but if management does not accept that solution then it won't work. I'm not sure what the longest that I have seen boards stored with no problems but it would be longer than a year for ENIG boards.

And I would look at a nitrogen cabinet before looking at cold storage. There might be a mismatch CTE issue at lower temperatures. I doubt it but you never know.

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#88644

PCB with ENIG plating shelf life? | 17 November, 2022

I need to back it up with a something like IPC standard. It seems to me that people have used boards that aged after the 12months period, however there is no information supported by studies that can show results in quality and reliability of the boards. This is the type of evidence I am looking for to backup an opinion with.

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#88645

PCB with ENIG plating shelf life? | 17 November, 2022

You might be able to create a process that involves testing a sample before each run. But then you would need something showing that a given batch would be consistent enough to justify testing a pcb to prove the batch. Or if they accept SPC then you can have a number of randomly selected boards tested.

Or maybe you could also look for something that shows that if there was going to be a problem that it would show up at the time of processing. That way you can show that if the pcba's are good when made that the long storage of the boards won't cause trouble later.

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SMTA-64419298

#88806

PCB with ENIG plating shelf life? | 6 January, 2023

Hello Evtimov, sorry...just saw post as I was looking through list...a bit late. I don't know if you ever got your answer. IPC-4552A covers EniG finishes and suggested shelf life. I've referred to these doc's quite a bit. Good spec's ! Yes, I believe it states 12mos, but other commentors are correct... With proper application of Nickel/Gold and good packing/storage, it will easily last two years. Check all packages for vacuum loss. If any Question, perform Wetting test before assy. IPC has a wetting test procedure that is similar to what we have done. Crude steps: 1_ bare board through paste/oven/top-bot (no comps): look for neg. wet angles. 2_Test same board in solder-Wave (mimic total thermal cycles), but may have to populate a few Through-hole comps to make sure no excess micro-voiding or de-wet within holes when leads are present. 3_if all ok so far, place a couple parts (BGA and a most difficult QFN comps with large thermal pad...Reflow...check on Xray. Good luck and hope it all worked out. Les

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