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Flex circuits are designed to solve electronic packaging and assembly problems, solve interconnection issues, assist in miniaturization, and provide a dynamic electro-mechanical solution. They are configured with repeatable conductors that foolproof assembly errors. Flex is used in designs where standard printed circuit boards, connectors and cable assemblies just don’t provide the right electrical or mechanical solution.
For solving standard types of solutions, flex vendors use off-the-shelf materials such as rolled annealed copper, Kapton®/polyimide and various adhesives. In some other applications, one can build rigid-flex, where FR-4, prepreg and solder-mask are added to get to the right mechanical construction. From a flex assembly perspective, thousands of 0201 (0.02”X 0.01”) and 0402 components are placed every day. These types of material constructions and component assemblies can be found in many flex circuit shops today.
But now flex vendors are seeing a new wave of challenges to solve. These challenges are rising out of the need for wearable electronics, higher speeds, mobility, component miniaturization, and overall electronic packaging density. Let’s take a look at some of these.
Density and Miniaturization
Two examples of new applications in the medical market that are driving flex technology are: 1) Remote_patient_monitoring, which is forecasted to grow at a 77% CAGR and 2) Wireless healthcare, which is forecasted to grow to $9.6 billion by 2018. Imagine wearing a device on your body that would connect wirelessly to the Internet and feed your doctor various bits of information about your body from your home. Or in this case, from your body, wherever it may be.
Medical devices and sensors are now wearable. We have multiple applications here at PFC today that are wearable solutions. Wearable applications require thinner materials, new circuit geometries, and miniature components. The wearable market is forcing components to be smaller, smarter, faster, and the packaging and assembly to become more complex.
To meet the needs of the medical market requirements standard, off-the-shelf, 1-ounce copper just won’t work. Flex materials are getting thinner, providing densities and flexibility increase. For example, new materials include a 12-micron (.00047 inches) adhesiveless material and there are discussions around 9-micron (.00035 inches) adhesiveless materials. These types of densities are required to meet flexibility, geometric and component requirements of the wearables market.
Because of the some of the new density requirements—lines, spaces and assembly/component placement—standard PCB suppliers and contract manufacturers cannot necessarily support the density of the components. Flex is now the answer. For example, a North American flex circuit supplier received a request from a product design company that is developing a wearable solution requiring a specific .4mm pitch BGA Bluetooth component. The designer’s “go-to” PCB supplier could not support the thickness/thinness requirements of the circuit. In addition, his go-to contract manufacturers could not place a .4mm pitch BGA Bluetooth component.
The Bluetooth component manufacturer suggested they work with the flex circuit supplier, since the supplier had placed the component for other projects. Remember, flex circuits have the ability of being almost any thickness, depending on chosen materials and electrical requirements. Flex is not bound by .031 or .062 standard thicknesses like PCBs.
The important fact here is that the design engineering firm is now using flex circuits instead of rigid PCBs, not because of the electro-mechnical characteristics of flex, but rather because flex can provide the thickness and package density required.
Mike Morando is VP of sales and marketing for PFC Flexible Circuits LTD.
