A dry box is a storage container in which the interior is kept at a low level of humidity. It may be as simple as an airtight and watertight enclosure, or it may use active means to remove water vapor from the air trapped inside.
Dry boxes are used to safely store items that would otherwise be damaged or adversely affected by excessive
humidity, such as
cameras and
lenses
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...
(to prevent fungal growth),
3D printing filament (to prevent moisture caused damages such as popping and sizzling when passing thru the hotend and turning into steam. Moisture soaked filament also becomes brittle or soft.), and musical instruments (to prevent humidity induced swelling or shrinkage of wooden instrument parts). They are also used in the storage of
surface mount
Surface-mount technology (SMT), originally called planar mounting, is a method in which the electrical components are mounted directly onto the surface of a printed circuit board (PCB). An electrical component mounted in this manner is referred ...
electronic components prior to
circuit board assembly, to prevent water absorption that could flash into steam during
reflow soldering, destroying the part.
Types
Desiccant boxes
A simple dry box can consist of nothing more than a sealed, airtight box containing a
desiccant
A desiccant is a hygroscopic substance that is used to induce or sustain a state of dryness (desiccation) in its vicinity; it is the opposite of a humectant. Commonly encountered pre-packaged desiccants are solids that absorb water. Desiccant ...
, such as silica gel or anhydrous calcium chloride. These can be easily built at relatively low cost. However, the humidity level in such boxes cannot be controlled or regulated, owing to the difficulty of gauging the quantity of desiccant required to achieve a certain humidity level. Repeated opening of such boxes, allowing humid ambient air to enter, can saturate the desiccant, and some desiccants can have corrosive or other harmful effects on the contents of the box if they collect enough water to dissolve.
Electronic dry boxes
Electronic dry boxes contain a small
Peltier cooler
Thermoelectric cooling uses the Peltier effect to create a heat flux at the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side o ...
, which removes moisture from the air by condensing it out. A control dial is usually provided that permits the user rough adjustment of the humidity level. More sophisticated designs link the cooler to a settable digital hygrometer, allowing very precise humidity level control.
Another form of electronic dry box technology utilizes multi-porous molecular sieve desiccants to absorb moisture. This moisture and humidity control technology is renewable without having to replace desiccant and is capable of reaching low humidity (20%RH or less) to ultra low humidity (5%RH or less) levels. Generally dry boxes with 5%RH or less is utilized in surface mount technology in order to comply with IPC/JEDEC J-STD-033. Desiccants have advantages over Peltier coolers in colder ambient temperatures.
See also
*
Molecular sieve
References
Sources
* https://www.eurekadrytech.com/how-does-eurekas-auto-dry-box-work
* https://www.eurekadrytech.com/application/humidity-controlled-3d-printing-filament-storage-dry-cabinet
Frequently Asked Questions about Dry Box Cabinets
* https://web.archive.org/web/20150513114432/http://www.jedec.org/sites/default/files/docs/jstd033b01.pdf
Tools
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