Power up for tough conditions

ESNA SepOct14 Pg22 Harsh Environments MPD 1Challenging environmental conditions require robust and reliable power management solutions to last the distance, explains president of Memory Protection Devices, Tom Blaha.

The majority of consumer electronic devices are powered by standard, off-the shelf rechargeable and non-rechargeable batteries that deliver a maximum of three to five years of service life within a fairly moderate temperature range. Since these mass produced devices are intended to be replaced every few years, the choice of battery holder is usually dictated by cost.

Meanwhile, increasingly sophisticated wireless applications are emerging that require robust power management solutions to address challenging environmental conditions involving extreme temperatures, corrosion, shock and vibration.

Materials selection

Application-specific requirements dictate the ideal choice of battery holder. If the device needs to be miniaturized, or circuit board real estate is at a premium, then space-saving battery holders need to be considered. Solutions include the Mini, which allows coin cells to sit in a hole drilled through the printed circuit board (PCB) to minimize profile, through to vertically-oriented battery holders that free up space on the PCB.

Coin cell holders made of high quality liquid-crystal polymer (LCP) plastic are ideal for surface mount (SMT) soldering because they boast exceptional dielectric strength and can withstand 300ºC lead-free reflow process temperatures.

Wave soldering processes require less rugged materials, supporting the use of PBT/nylon plastic insulator materials that feature a dielectric strength of 560V/mil at 25ºC for five seconds. Other benefits are said to include resistance to chemicals and solvents, excellent strength and toughness, a wide temperature range with good thermal cycling performance characteristics and an insulator resistance of 5,000M Ohm minimum. Nylon is ideal for the frigid temperatures of medical cold chain storage, which can reach -85°C, as this material is less brittle than LCP.

If the device is exposed to moisture and humidity, then gold-plated battery contacts are preferred over tin/silver- or nickel-plated contacts. Gold offers improved electrical conductivity and will not corrode.

Rugged construction

For devices that require high shock resistance, pressure contacts are recommended over spring-loaded contacts. If the device has a battery access door, then it could make sense to add plastic ribs to the inside of access door to further prevent battery movement. Many larger cylindrical battery holders also come with optional retaining straps or covers that further ensure ideal battery retention.

Buyers looking for low-cost protection may be able to utilise the Snap Dragon holder. This patented device was developed for securing CR2023 coin cells. It is said to be both ultra-thin and extremely strong, and features an LCP plastic carrier that can withstand the high temperatures associated with medical autoclave sterilization. The Snap Dragon also features a snap-on cover that encloses the entire coin cell, yet is designed to allow for easy battery insertion and extraction. Snap Dragon battery holders can be supplied with SMT tabs or thru-hole pins on standardized tape and reel packaging for pick-and-place assembly.

Choose quality

Battery holders intended for use in extreme environments must be manufactured to the highest quality standards using superior quality raw materials, meeting and exceeding ANSI/EIA-5405000 standards, as well as all other applicable regulatory compliance requirements, including RoHS lead-free. Thorough due diligence during the specifying process will help ensure years of trouble-free operation.