Why don't we see electronic devices in bathrooms failing under such high humidity?

Question

I recently read that the relative humidity inside a fogged-up bathroom, such as during/after taking a shower, should be close to 100%. And we know that bathrooms these days are filled with all kinds of electronic devices – some of which are even explicitly expected to be used inside the shower (such as electronic shavers). But I've never seen electronic devices/components rated to be used in anything close to a 100% humidity environment – it's usually rated to something like 40% relative humidity. So why don't we see bathroom devices failing under such high humidity? Or are these devices actually designed to be fine in 100% humidity environments? If so, then how?

Answer 1

The failure modes for electronics in washrooms are as follows;

1. an insulator becomes a conductor, contaminated with moisture, dust, flux etc.
2. an insulator becomes a bigger capacitor up to 20x to 80x greater due to the dielectric constant of water and RF or fast rise time circuits.
3. a conductor becomes an insulator caused by corrosion accelerated by moisture or %RH

4.a conductor bridges another conductor from corrosion.

The solution depends on the protection level desired for water-spray or immersion, but may involve conformal coating, enclosure rubber seals and ultrasonic cleaning.

Therefore consider the solder mask and conformal dips or spray to reduce moisture ingress types to improve insulation from contaminants with humidity. Most plastic is hydroscopic so choosing the right type depends on the environment.

Even good brands like Philips wet shower shavers have a limited lifespan due to moisture ingress and the reliance of good neoprene seals.

Answer 2

To quote the following article: How-To Geek: Can High Humidity Damage Electronic Devices?

but it is generally quite hard to reach levels of humidity that will actually cause damage since it would likely need to exceed 80 percent for extended periods of time. That would be very unhealthy and will cause far more damage to you than to your electronics. Humidity should be kept at around 40-60 percent for occupied areas.

Basically the takeaway I remember from my classes is that most electronic consumer electronic devices today are made to operate under standard environmental conditions which a bathroom would fall under.

Answer 3

There are many factors to consider.

1. It depends on the device .For example one usually does not bring a laptop or a graphics card inside a bathroom. Those would get damaged easily.

2. Most of the water damage happens when the device is functioning. When the device is on, electrons travel through the traces and cables, speeding up the damage. Again, in bathroom one may not use the device while showering, and the device will have any (little) water on it evaporated after one is done showering.

3. Many devices can prevent water/humidity from entering them, even if they are not water proof. Cell phones or electric shaving machines for example have their chassis protecting the internals and battery, so even if you dip in into the water, it wont get damaged easily (happened to me many times with both).

4. Regarding the ratings of humidity, these must be nominal, and might apply while the IC is working (is on power). Its not so easy to destroy an IC that is not on power even if you dip it inside water, especially evaporated water, which has less (or none) salt and other impurities.