Blank PCB shelf life - Page 1
Forum section: electronics / general

author: law
author_rank: Regular Contributor
timestamp: August 21, 2024, 12:41:08 am
content: Hi all,I have some old blank PCBs that have been in storage for a bit over a year, that I am looking at using.The packaging has been opened, and the boards stored in their opened package in an Ikea container with a lid.There has been no humidity control. The boards are ENIG, from PCBway.I am aware of the requirements to bake blank boards that are stored improperly, but in general do blank PCBs have a shelf life?Thanks

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 21, 2024, 01:08:37 am
content: Blank PCB's do have a shelf life and it's due to surface finish and (very minimal) oxidation that affects solderability. Tin oxidizes relatively quick while gold is pretty much inert.Did a short search and followed some links:https://duckduckgo.com/?hps=1&q=ENIG+shelf+life&ia=webMany claim a shelf life of 12 months for ENIG, which I find strangely short. I guess that simply nobody wants to test for longer durations or make claims that could result in a warranty dispute if a PCB ever fails to solder. Just covering their asses in an area nobody cares about at the moment they order new PCB's.On top of that, solderability after long storage is affected by a lot of factors. Long ago, when local electronics shops were still a thing and I bought matrix PCB's for my own projects some had areas that were difficult to solder and which had a very suspicious form and size of a fingerprint.

author: jmelson
author_rank: Super Contributor
timestamp: August 21, 2024, 01:48:52 am
content: When using boards more than a few months old and in the open, I get blisters between layers if I don't bake them before IR reflow. My procedure is 1 hour at 50 C then 1-2 hours at 70 C. Then, there won't be any blisters. That's the only shelf life issue I am aware of.Jon

author: law
author_rank: Regular Contributor
timestamp: August 21, 2024, 10:15:31 am
content: Thanks fellas,Yeah I thought I'd post the question here as I see different manufactures have pretty wildly different shelf lives.I see PCBway says 6 months for ENIG when vacuum packed .Then this random supplier shows 1+ years .Here I'm not too sure if this just means PCBway boards just have a short shelf life...https://www.pcbway.com/pcb_prototype/PCB_Shelf_Life.htmlhttps://www.sfcircuits.com/pcb-production-capabilities/pcb-surface-finishes

author: wraper
author_rank: Unknown
timestamp: August 21, 2024, 10:27:25 am
content: Quote from: jmelson on August 21, 2024, 01:48:52 amWhile you should bake the boards if they were not stored in moisture barrier bags with desiccant, blisters suggest your IR reflow process likely overheats them. Also 70oC is too low, especially for just 1-2 hours. If you need to dry them within a few hours, I suggest about 120oC.

author: ansonbao
author_rank: Regular Contributor
timestamp: September 05, 2024, 05:49:17 am
content: If it is vacuum packed, the shelf life of immersion gold can be maintained for one year.If it is not vacuum packed, it depends on the actual storage environment, temperature and humidity, etc. You can test it to see if it can still be used.

author: law
author_rank: Regular Contributor
timestamp: September 05, 2024, 10:54:40 pm
content: Thanks - how do you test it? Just solder to the pads and see how it goes?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 09, 2024, 10:39:45 am
content: There are two possible issues. Outgassing of absorbed moisture, that can be fixed by baking the PCB's. and oxidation of the pads, which makes soldering more difficult, and can possibly be remedied by using a more aggressive flux. But apart from the baking, indeed just try it out. It also depends on the cost of the PCB versus the cost of the parts you put on the PCB (and the cost of assembly time).Unless the parts are very expensive or difficult (1500 pin BGA's), I would just try it out. At the very least you gain some experience.

author: Psi
author_rank: Super Contributor
timestamp: September 09, 2024, 10:45:07 am
content: ENIG is really good.Silver becomes bad in less time than it takes the PCB fab to ship them to youHASL is somewhere in the middle

author: law
author_rank: Regular Contributor
timestamp: September 09, 2024, 11:09:00 pm
content: Excellent - Thanks very much all