How to survive sourcing for harsh environments

esuk-oct16-p29-charcroft2A product designed specifically to operate in harsh environments is defined by its ability to withstand and survive a critical event. So how robust are the components you specify?


When a mobile phone is dropped, it could smash the screen or damage the electronics inside resulting in a repair, or an insurance claim. When a military communications system is dropped however, the consequences are significantly greater, so its ability to survive and continue to operate must also be higher.

For buyers, understanding the different levels of robustness across key parameters can help to inform purchasing decisions.

What are the risks?

A component’s ability to withstand contaminants in the operating environment is covered by the ingress protection (IP) standard. Comprised of two digits, the first defines resistance to solid particles and the second shows protection against water.

When it comes to withstanding extreme temperatures, the industry has defined a number of set ranges. The commercial range extends from zero to 70°C; industrial from -40 to 85°C; extended industrial and automotive from −40 to 125°C, and military from -55 to 125°C. With the proliferation of high-temperature applications in industrial and down-hole industries, many products are rated above 200 or even 250°C.

Resistance to mechanical impact or shock is measured in joules and follows the IP format. The IK code, specified in EN 62262, ranges from IK0 up to IK10, at which the product should withstand a force of up to 20J. In contrast to shock, acceleration is measured as a gravitational force. Standing at sea-level, the human body is subjected to a gravitational force of 1g, while the maximum g-force in a fighter jet is around 10g.

G-force forms part of the vibration rating, in conjunction with Hertz, which measures the speed, or frequency. Compare, for example, the regular low-level vibration of a machine on a production line with the faster, more violent vibration of a fighter jet at take-off. Aircraft circuit breakers, for example, are therefore rated for vibration of at least 10G and frequencies of between 50 to 500Hz.

Assess sealing needs

Typically, a hermetically-sealed package will ensure that a device is air or gas-tight. Hermetic package bonding options include glass to metal, ceramic to metal, or epoxy seals.

Encapsulating, or potting, components in epoxy resin works by placing the original device in a case, which is then filled with liquid epoxy resin and cured until the resin becomes solid. Moulding refers to a similar technique where the mould is removed after curing to leave the encapsulated component. Another method is powder dipping, in which powdered epoxy resin is applied to the component, heated and cured until it melts to form a glossy encapsulation. Alternatively, one or more of these techniques can be used together to provide additional protection.