Designing LCDs for Use in High Vibration Environments

What is a Rugged LCD?

Rugged LCD monitors are specialized devices designed to function in a variety of settings where harmful factors such as extreme heat or cold, dust, moisture, or water may be present. High vibration use-cases are often considered for such displays as components need to be able to withstand use in off-road vehicles, construction equipment, or wearable fitness devices. There are multiple considerations in the design of vibration-ready LCD, one of which is the material used to bond an LCD together during the manufacturing process.

Optical Bonding

An LCD is made up of a stack of several materials that work together. The methods and materials used to hold components together must be able to withstand high vibration use cases. A common bonding method to secure LCD components is optical bonding, a process by which the internal reflection between the LCD and cover glass is reduced allowing for improved energy efficiency and improved resistance to shock and vibration.

Optical bonding is a process by which a specialized resin is applied between the glass and the LCD panel bonding them to ensure there are no pockets of air or gaps. Optical bonding is popular in the military, transport, and retails sectors where vibration and shock are commonplace. Another reason why this is a go-to binding method is that the resin binding layer physically prevents moisture and dust ingress between the display and external cover glass.

Enclosures

Display enclosures are another solution and offer additional protection and insulation from bumps, vibrations, and direct impacts. Such enclosures can include foam-based shock insulation and shock-resistant mounting hardware. Enclosures are a cost-effective solution for high vibration situations and can be integrated into the design of the LCDs placement. One example of this can be found in “tough” digital watch cases that protect advanced LCDs from shock, vibration, and temperature extremes.

The materials used for an enclosure are also important to consider. Initially, metal enclosures might be chosen due to their ability to quickly dissipate heat and high rigidity, but in some vibration and shock-prone use cases, plastic or rubber enclosures may be chosen to allow for parts to flex rather than break.

Modern enclosures include those made of carbon fiber, which is extremely strong but still offers relative crack resistance and allows for flexing when exposed to shock. Materials such as magnesium alloys offer mixtures of magnesium with other metals such as aluminum, zinc, manganese, silicon, copper, rare earth metals, and zirconium. These alloys allow for enclosure designs that can be made bespoke to serve the specific situation and conditions that the displays will be exposed to to maximize performance and operating life.

Considerations

LCDs include multiple components aside from the liquid crystals themselves and glass covers. Such components include complicated electronics such as wiring, control modules, and printed circuit boards. A common LCD point of failure in high vibration use cases is the printed circuit board or PCB. This unit can include critical power management hardware, graphics acceleration, and processors. When PCB build materials are not chosen for high vibration environments, they are prone to cracking, additionally, fasteners may loosen over extended time periods. Typical failures also include broken component leads. A good first step to considering PCB design is instituting vibration resistance to the fasteners themselves using materials such as rubber.

One consideration that can affect every component of an LCD that is often overlooked is friction. Parts that are not bound to each other can rub against one another in high vibration environments. Possible points of failure include frayed wires, worn connectors, and rubber seal cracking and failure.

Wire damage can occur in high vibration environments. This can occur when rubber insulation surrounding live wires rubs against other components in response to vibrations resulting in breakages that can lead to short-circuiting, or worse, presenting an electrocution hazard. One manufacturing method that can extend the service life of such components is lubrication which can lower the friction and allow for smooth interaction with other surfaces.

Other significant considerations are the materials and designs of wiring harness connectors. Connectors are used to join wires and cables, as well as to connect modules such as display backlight hardware or processors to the PCB. These sensitive connections are often very small (to optimize space efficiency in compact units) and are traditionally made of materials such as soft plastics. This poses a problem because friction caused by movement, shock, and vibration over time, can wear out connecting hardware and result in connection failures.

Finally, rubber seals that are used to prevent liquid and dust ingress can develop microfractures and eventually fail when exposed to high vibration environments.

The demand for LCD performance in high vibration environments continues to grow as industries such as off-road recreation, military, and law enforcement, as well as industrial construction grow, and existing technologies are upgraded to include LCDs. Displays provide mission-critical information in shock and vibration-prone environments, so failures can result in catastrophic consequences. Luckily, Focus LCDs offers a wide variety of LCDs that are tested to perform in high vibration environments, and will even discuss custom solutions to meet your company’s needs.

REFERENCES: