My relativity humidity is around 80% average. I heard electronics must be maintained between 40 to 60% Relative Humidity. So I'm thinking of the following options.

1. I'll buy an air tight plastic container to put the device insideit, and put moisture absorbing silica gel pouch inside. So I plan to put the device inside when Relative Humidty of surrounding is 60%. Logic is the humidity inside won't be 80%. But question. If the silica gel is present inside, would humidity inside the air tight box go down to maybe less than 40% and become ESD prone (for humidity less than 40%)?

2. Generally. Would the air tight plastic container be a good idea since it can hold static? Can it affect the device that has its own cover and the PCB not exposed of course. But it has connector that can attract ESD?

3. The best of all worlds would be to get an air tight antistatic ESD container. Is there such? Should one get a conductive container or slowly dissipative container? But I doubt if it is also airtight. If it is not, humidity can be a problem.

 

What is the device? Is it a DHT temperature and humidity sensor?

 

A sealed container - especially plastic - will develop a static charge simply from being handled. Plastic is not a good choice.

Now; assume you have a plastic box with no static charge and is at 50% humidity. Assume you leave it alone for years and never touch it. Also assume you have an absorbent pack to attract the moisture. Simply by nature, osmosis will attract more moisture into it. Eventually the absorbent will become saturated and the humidity level will go up and down with ambient moisture. You're not going to gain anything without an ACTIVE moisture control approach.

But the thing with high humidity is the corrosiveness of oxygen and moisture. THAT can cause trouble with connections and with solderability. ESD and moisture are two separate issues. Sure, with low humidity static charges are more easily generated and held onto by different materials. Even you are subject to holding a static charge. The human body can hold charges as high as 50KVS (Kilo Volts Static). It's that snap when in the winter time you get out of your car to pump gas and you turn and touch the door to close it and you get that muscle jolting pulse of static discharge that can be somewhat painful.

I would never recommend storing static sensitive components in a plastic container. Passive components? Sure. I have resistors, capacitors, diodes and even transistors in plastic containers. BUT the transistors are robust and can handle any charge buildup and discharge. Sensitive stuff like small active components, microchips etc. those get stuffed onto conductive foam. That keeps the whole component at the same charge level. Even when handled. The thing about conductive foam is that it can promote tarnishing of the leads making it harder to solder, sometimes even impossible to solder.

 

How can osmosis attract more moisture into the sealed container? No air coming inside. What is the medium of osmosis?

I am storing an expensive EEG device that is sized like a router. I don't want the constant 80% humidity to corrode the internal parts. So how should I store it?

 

If you are storing something so expensive, why don't you get air tight ESD container? Your option No. 3.
There are all kinds of ESD storage boxes, if you are concerned about the humidity you can get a bunch of ESD zip-bags too.. they come in all sizes.. put the device in a zip bag and in the container.

 

If you just want to store the equipment, put it in an antistatic bag or warp it with aluminium foil. Then place it in a zip-lock bag with some silica gel packets and a moisture indicator card.

You can rejuvenate silica gel packets and the indicator card by placing them in an oven at 120° C for 2 hours.

 

If you are storing something so expensive, why don't you get air tight ESD container? Your option No. 3.
There are all kinds of ESD storage boxes, if you are concerned about the humidity you can get a bunch of ESD zip-bags too.. they come in all sizes.. put the device in a zip bag and in the container.

My question is whether to get air tight ESD storage box that is conductive or dissipative. And what humidity outside before I closed the box. Like do I have to open aircon to decrease humudity before shutting it close and whether the silica gel can make it further go down to 20% relative humidity inside. Also I've been googling half an hour. I cocldn't find any air tight ESD storage box for storing something same size as router.

 

How can osmosis attract more moisture into the sealed container?

In high school science we did an experiment. We took bags and filled them with water then immersed them into water. In one bag we put salt water and sealed it; then dropped it into a bucket of fresh water. The second bag was filled with fresh water and sealed it; then dropped it into a bucket of salt water. Come the next morning the bags with salt water in them had shrunk by osmosis. The higher concentration of salt migrated through the bag, leaving the bag size diminished. Whereas the other bag with fresh water had swollen from being immersed in salt water. Again the higher concentration, through osmosis, had made its way into the bag swelling it.

When dealing with ESD, higher humidity reduces the risk. You don't want it in a desiccated environment. Any generation of static will affect the components. The BEST storage for sensitive electronics would be to use a velostat bag. Velostat bags are metalized bags that form a Faraday Cage. Any static charges will pass along the metalizing and be conducted around the protected circuitry to ground. Or to some other source of draining of the charge. If you don't have or can't get a metalized bag - use a metal box.

But how did this device come to you? Likely in a cardboard box with packing to protect it from damage. The engineering that went into the circuitry included considerations for handling ESD events safely. No sense in buying a thousand dollar safe to keep your lolly-pop in it. Protected? Yes. But at what expense?

 

My relativity humidity is around 80% average.

That sounds miserable. Why not solve that problem and make yourself comfortable at the same time? Get an A/C or a dehumidifier.

 

That sounds miserable.

Sounds like Houston or Florida. Or anywhere in-between.

 

If the factory packaging of the sensitive devices has been opened, a closed marmalade jar without the marmalade works well.

----> https://www.petronaftco.com/moisture-barrier-material-for-packaging/

 

If the factory packaging of the sensitive devices has been opened, a closed marmalade jar without the marmalade works well.

I am storing an expensive EEG device that is sized like a router.

I don't think it's going to fit into a mason jar.

 

Almost !

Seen olives packed in ~ 16" jars

 

Secan do you have dimensions of the device?

 

You are overthinking this solution.

Wrap the device with aluminium foil.
Place it in a zip-bag with a silica gel packet and humidity sensor card.
Wrap it again with aluminium foil.
Place it in a cardboard box.

Done.

 

My relativity humidity is around 80% average. I heard electronics must be maintained between 40 to 60% Relative Humidity. So I'm thinking of the following options.

1. I'll buy an air tight plastic container to put the device insideit, and put moisture absorbing silica gel pouch inside. So I plan to put the device inside when Relative Humidty of surrounding is 60%. Logic is the humidity inside won't be 80%. But question. If the silica gel is present inside, would humidity inside the air tight box go down to maybe less than 40% and become ESD prone (for humidity less than 40%)?

2. Generally. Would the air tight plastic container be a good idea since it can hold static? Can it affect the device that has its own cover and the PCB not exposed of course. But it has connector that can attract ESD?

3. The best of all worlds would be to get an air tight antistatic ESD container. Is there such? Should one get a conductive container or slowly dissipative container? But I doubt if it is also airtight. If it is not, humidity can be a problem.

I am asking very specifically as to where you "heard this" .
Certainly, to assure good solder connections the condition of components to be soldered is important.
BUT after "electronics" is built, it often must survive high humidity and random temperatures.
So either what the TS "heard" was applicable to specific items, or it was just more garbage spewing online .

 

Does it happen even when container is AIR TIGHT??

It can. Some materials can appear to be a physical barrier while still allowing diffusion. For instance plastic wraps differ in their rates of oxygen or water vapor diffusion.

That said, the rate of moisture diffusion through an "air tight" surface is going to be pretty low compared to the occasional opening of the chamber. Whatever you are using to mitigate the moisture should be able to handle more than just diffusion.

I maintain that the best strategy is to dehumidify the entire room. This will benefit more than just the few pieces of equipment.

 

Can wood introduce static? Usually not, in regions with high humidity.

I use it every few days, do you mean I have to wrap it in aluminum foil and putting inside zip-bag with silica gel every few days or did you assume it was for long term storage only which is not?

I assumed you meant long term storage.
If you are going to use it every few days, just put it in a cardboard, wooden, or metal box and don't lose sleep over it.

 

to assure good solder connections the condition of components to be soldered is important.
BUT after "electronics" is built, it often must survive high humidity and random temperatures.

Bill raises an excellent point. One even I considered mentioning but neglected to. Thank you Mr. Bill for taking the time to state such a fact. To be clear, solderability is not at question. ESD is the crux of the topic.

I use it every few days, do you mean I have to wrap it in aluminum foil and putting inside zip-bag with silica gel every few days or did you assume it was for long term storage only which is not?

Since this is a finished product the only static discharge you'd need to worry about is lightning. Any other form of static is not going to be of any consequence.

That is why putting inside container would be better. But I can't find any air tight ESD storage box. What product can you suggest?

At this point storage on any kind of shelving will be of no danger to your equipment. Metal, wood or plastic, you don't need to be concerned about ESD.

I'd like to know if such kind of case is anti static.

It's unlikely a manufacturer of such a device at this state of build would take on the cost of using an anti-static case for their product. If it WERE of concern the manufacturer would likely have stated that the product - in order to maintain warranty - MUST be stored in an anti-static container. Since I see no warning I would assume ESD is of no concern.

My advice - don't worry about it. It's not a real concern. Otherwise there'd be hundreds, thousands, tens-of thousands of failures due to improper storage.

Unwatched.

 

I have worked with and used some electronic equipment THAT DID COME WITH STATIC WARNINGS! Those warnings were rather explicit. That equipment was an exception.