Electronics Protection - March/April 2013 - (Page 10)

Feature Testing for Ingress Protection of Portable Electronic Devices Cherish K. Robinson, Application Engineer W. L. Gore & Associates Today’s consumers expect to be able to use their full-featured mobile devices anywhere, whether they are skiing on top of a mountain, talking on the phone while running through a rainstorm, or taking underwater pictures in the Caribbean. They also expect these devices to be small and lightweight, and most of these devices have audio components that require one or more openings in their housings to enable sound waves to be transmitted. Testing devices for ingress protection is one of the essential elements of the engineering cycle to ensure they can withstand the environmental conditions they encounter. Manufacturers generally protect their mobile devices from exposure to environmental contaminants by using rugged seals in the housings. They have traditionally used the International Standard IEC 60529 criteria to validate their protection against contaminants. The testing protocols in this standard were originally developed for industrial electronics in larger enclosures such as construction and worksite devices, large shipping containers for transporting equipment and stationary equipment on telecommunication towers. Although the IEC 60529 defines specific levels of protection, the testing protocols are limited and do not account for realworld conditions that portable electronics encounter. As a result, manufacturers usually do one of two things; either they ignore the standard, which can compromise reliability, or they spend substantial time and effort trying to comply with the standard. In this case, the result can be an over-engineered instrument that doesn’t appeal to the consumer’s desire for a small, lightweight device. The portable device industry needs testing protocols that are more focused on consumer electronics and how they are used. W. L. Gore & Associates has developed multiple testing methods that address particulate and liquid protection in the real-world conditions these devices encounter. With these protocols, test results are more reliable, which results in improved durability of portable electronics. Materials Testing To protect the audio components of portable devices, most manufacturers install protective vents over the transducer opening. Under IEC 60529, these vents are tested as a component of the assembled device and as such, are not independently rated. Therefore, their performance is not evaluated until the device is completely assembled. For portable devices, different material constructions can be used depending on the design of the device housing. For example, if a housing has open holes near the transducers, a tight non-woven material is needed for protection. However, if the housing has louvered openings, the slats provide some level of contaminant protection, so the material can have a more open weave. Therefore, engineers often want to evaluate 10 the performance of various venting materials and housing designs to identify the best combination for their specific application, but IEC 60259 does not define testing protocols for this scenario. Particulate Testing IEC standard 60529 testing protocols evaluate materials based on their ability to block particulates of 50 microns (µm) or larger. This results in two challenges for the portable electronics industry. First, portable electronics are exposed to a variety of particulates that are usually much smaller than 50 µm, particulates that range from 1 to 30 µm such as human hair, carpet fibers, pet dander and smoke fumes (Figure 1). Devices are not tested against these realworld particulates. Figure 1. Portable electronic devices are often exposed to particulates smaller than 50 µm. Second, if a device is tested, it may fail due to improper material selection. Many manufacturers simply specify a maximum pore size for the venting membrane, and they select materials based on their pore size specification. Particulate shape and surface area have a more direct impact on the level of protection a material can provide than pore size does. Woven and non-woven materials are used in vents that provide dust and splash protection. Because a woven material has a uniform pore size (defined by the width of the open square between fibers), the material is able to capture only spherical particulates equal to or greater than the material’s defined pore size. For example, a human hair has a surface area equal to or larger than the specified pore size of many woven materials, yet it can still pass through the material because of its shape (Figure 2). On the other hand, non-woven materials are able to capture particulates of various shapes and sizes because of their three-dimensional structure. They are also more likely to maintain consistent airflow because they capture particulates in a torturous path not limited Figure 2. A human hair’s shape enables it by a specific pore size. to pass through a woven material with a smaller pore size. To address the needs of the portable electronics industry, Gore’s engineers developed a protocol that focuses on particulates that are as small as one micron. They worked with an independent laboratory to modify the ASHRAE 52.2 test protocol, Method of Testing General March/April 2013 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - March/April 2013

Electronics Protection - March/April 2013
Newer Technology Releases Next-Generation Power2U AC/USB In Wall Charging Solution
Specifiers of Enclosures for Components in Outdoor Applications: Be Aware of Material Selection Issues
How to Protect Electronic Circuits from Power Surges
Testing for Ingress Protection of Portable Electronic Devices
Increasing the Lifespan and Reliability of Electrical Components
From the Inside: The Configurable Plastic Enclosures Revolution
Tips for Selecting and Designing a Membrane Switch
HP Intelligent Series Rack Models Available for Networking and Demanding Server Requirements
Polyonics Antistatic Tapes Solve ESD Problems Before They Damage Static Sensitive Devices
OptoTherm Introduces IR LabMate Infrared Camera Solution
Falcon Electric Offers NEMA 3R/4 Enclosures with SSG UPSs
PEM SpotFast Fasteners Enables Flush Joining of Two Sheets
Industry News
Calendar of Events

Electronics Protection - March/April 2013