Our goal is to make the Wockets enclosure waterproof.

One idea is to use two layers of protection:

Waterproofing electronics is not difficult, but waterproofing electronics at low cost and thinly and in a way that can be done at low and high volume production is tricky.

We have tested the Parylene coating and it appears to work. Here is an image of a Wocket V2.1 transmitting while immersed in water.

WocketInWater.jpg

We have also built a device to heat seal the sensor in a polyethylene housing. It creates a housing like the one shown here (we handle the seal around the microSD using polyethylene tape that adheres to the PCB, which the polyethylene outer film then adheres to (and pressure seals) during the sealing process.
ProtoSensorPolyHousing.jpg

This method meets our design criteria, but the polyethylene housing cannot withstand much abrasion, which can happen if the sensor is just placed in pockets with keys, a phone, etc. Nearly invisible holes can develop, and if the sensor is placed in a washing machine (our test case), water will seep in.

The method will be adequate for short term testing, but the sensors are not going to survive much abuse.

We are looking for alternative methods. We've thought about potting/encapsulating the sensor and battery (using custom molds that round edges) and using polyetheylene to encase and protect the wire and hold the sensor together, but we have concerns about thermal expansion and sutability of potting for production runs.

Ideas? (That don't substantially increase thickness or cost and provide a waterproof layer?)


Resources related to waterproof enclosure: