Ruggedizing Electronics with Parylene
Posted by Sean Horn
Friday, December 4, 2015 8:00
@ 8:00 AM
Ruggedized products are strengthened by various processes to ensure better resistance and prolonged use in operating conditions characterized by unusually excessive abuse. These conditions exist for aerospace/aeronautic, automotive, commercial over-the-counter (COTS), medical and military products, which require reliable performance through a disparity of functional environments that include:
- extreme temperature range,
- persistent, intensive vibrations both internally and external to the device, as well as
- material intrusions of dust, rain, soot, water or wind,
- among other working circumstances that generate wear, stress, and abuse.
Of primary importance is safeguarding the printed circuit boards (PCBs) and similar electronic assemblies that power or guide so many ruggedized products and systems.
- a device’s functional capacity under the conditions cited above and, more significantly,
- how it responds to the impact of artillery/gunfire, extreme acceleration and the presence of fungus or salt fog.
While many kinds of ruggedized electronics, such as implantable medical devices, do NOT need to perform through gunfire or require protection from acceleration, they still must function up-to-standard throughout the entire range of extreme and severe conditions specified above.
It should be remembered that medical devices are often required in situations that safeguard lives, to an extent equal to or exceeding military products, and require similarly reliable protection to assure functionality. But what can be used to protect the products themselves, to assure their dependable performance? One substance of considerable value for these purposes is parylene conformal coating.
Parylene Protection for Ruggedized Devices and Products
Types of conformal coatings vary, and can be applied with success for purposes suited to their particular properties and application procedures. Wet application materials such as acrylic, epoxy, silicone and urethane can offer degrees of coating hardness or flexibility, heat resistance or surface protection useful for specified ruggedized purposes. None, however, exhibits parylene’s versatility for ruggedized applications.
Parylene’s chemical vapor deposition (CVD) process permeates deep into the substrate surface. This property provides the PCB or electrical assembly a truly uniform, pinhole free coating that is exceptionally dielectric, maintaining long-term surface insulation resistance (SIR) appropriate to the optimal function of the protected electrical system. In addition, the increased development and use of MEMS/nano-scale electrical systems for ruggedized devices largely eliminates the use of competing coating materials. Their standard dip, spray, and brush-on coating methods simply cannot protect MEMS/nano applications; in contrast, parylene can, and very well. .
Prior to CVD, treating substrates with A-174 silane, or newer pre-treatment technologies, assures adhesion to surfaces as diverse as an elastomer, glass, metal, paper, and plastic, enhancing parylene’s versatility for ruggedized purposes. Its conformal coatings generate:
- barriers capable of withstanding the impact of bodily fluids, dirt, hazardous chemicals, heat, moisture, and other contaminants on assembly performance,
- high dielectric strength, coupled with favorable mechanical/physical properties, providing
- resistance to environmental convulsions, heavy vibrations, and shock, natural or man-made.
Parylene as a Medium of Enhanced Ruggedization
Approved as a military-spec conformal coating, parylene enhances the integrity of ruggedized devices without adding high cost. Much depends upon the application process, where deposition of the gaseous parylene onto the substrate generates a simulated organic growth of the coating, from beneath the substrate surface to the outer coating-layer. This ultra-thin protective film is exceptionally durable, yet not brittle as spray/dipped-coated substances like urethane or epoxy can become under harsh, frigid temperature conditions. Moreover, the parylene coatings do not decompose at upper range temperatures. The coating remains intact, maintaining the necessary dielectric and insulation qualities required for component performance.
Parylene types C, F, or N are highly recommended for ruggedization. All types of parylene share similar barrier and conductive properties, combining strength with minimal added weight and surface resiliency.
In addition to aerospace/military applications, refinement of parylene for ruggedized medical components responds to the need for exemplary functionality in the presence of often harsh bodily fluids. Appropriate masking of fragile electrical assemblies and components prior to enacting the CVD process ensures parylene application will not interfere with their function when in use.
Parylene coatings are recommended for ruggedized products where reliable, dedicated electrical, biological or environmental protection is required. Manufactured specifically to meet challenging performance standards for use in severe conditions, devices provided ruggedized parylene protection maintain operational performance. The resistance to harsh working environments provided by parylene supports functionality where unprotected devices would otherwise fail. Internal components of these specialized products require the same degree of ruggedization as exteriors. Whatever the ruggedized requirement, clear parylene can assist in assuring all systems work as expected