How Capacitive Touch Technology Enables Design Trends

The rapid shift from physical buttons to touch screens and capacitive touch switches has been fueled by the widespread adoption of smartphones as well as advances in the technology and materials utilized in user interface construction. While touch screens involve a transparent surface over living LCD screens, capacitive touch switches have a predefined location of keys or sliders that are mounted behind fixed graphics. As a finger gets near it, a capacitive sensor senses the change in the electrical field around the defined area and reports to the microchip that touch has been initiated. No direct contact is needed with capacitive sensors; in fact, the strength and length of touch can be calibrated using software.

Recent advances in the sensitivity and accuracy of the sensors, as well as the film or overlays that signify the “buttons,” have made capacitive touch interfaces elegant, durable and flexible. This has opened the door to a wide variety of use cases, components and features when the right tools and materials are used. By working with an experienced supplier such as Molex, manufacturers and designers can ensure that the components of a capacitive interface—sensors, overlays, adhesives and more—are the best fit for the product. 

Today’s capacitive interfaces have many customization options, making them an ideal solution for a wide variety of consumer and industrial products. Overlays can be plastic, glass or wood—anything nonconductive and thin enough to allow the capacitive sensor to sense the proximity of the finger nearby. They can be customized with a range of cosmetic options such as colors, molded facades, textures and backlighting, facilitating a sleek image. They can also incorporate sliders, wheels and proximity sensing for multifaceted panels, and can be mounted on curved surfaces.

Seamless overlays ensure easy cleaning. Additionally, key sensitivity, response time and proximity can be adjusted with software, making panels extremely customizable. Under the overlay, capacitive solutions can utilize traditional printed circuit boards (PCBs), flexible polyimide circuits or printed polyester circuits. Capacitive technology also offers durability due to:

• The absence of mechanical components that might wear out or break
• Resistance to harsh chemical exposure, the effects of EMI and contaminants
• The ability to be sealed against environmental conditions

Capacitive technology has been used for decades, and newer materials and approaches help overcome design obstacles, especially when used in more advanced or intricate applications. For example, it can be difficult to properly calibrate sensors if several keys are set close together, but the ability to adhere the sensor to the top of a graphic display enables broader alignment. Using adhesives with capacitive foil eliminates the potential for air gaps between the overlay and the sensor and makes assembly a more efficient process. And while capacitive switches on curved surfaces can present challenges for designs with FR4 boards, flexible substrates like silver flex circuits provide an adaptable solution.

Suppliers such as Molex are continually exploring new materials and processes to ensure capacitive touch capabilities are reliable for a range of applications. One emerging solution is silver flex, an electronic circuit that uses conductive Silver ink printed on a nonconductive substrate. This method helps reduce the size of or even eliminate PCBs in order to achieve cost and space savings.

The capabilities of silver flex are customizable depending on how it is assembled: it can be used on curved surfaces, and when clear conductive materials and adhesives are used, enhancements such as backlighting or in-mold decorated plastic can be added to the application.

Capacitive touch is becoming more ubiquitous in consumer and industry applications alike, as advances in materials and technology make it a more reliable and adaptable solution. However, choosing the right components is critical to ensuring the capacitive circuit is optimized for the application—and this includes considering the types of overlays, adhesives, circuit types and electronics that will be used. Working with experienced suppliers, such as Molex, that provide mechanical, electrical and software expertise allows designers to embrace creative solutions without sacrificing on cost, reliability or aesthetics.