Flexcertainty
By Steve Kelly, President, PFC Flexible Circuits Ltd.

Flexible printed circuits are one of the fastest-growing segments of the electronics manufacturing industry. This technology allows electronics to be mounted onto flexible plastic in order to fit circuit boards into curved surfaces, tiny spaces, or to enable circuit boards to actually move or flex during the product’s intended use. The circuitry is printed directly onto the plastic using photolithography, or may be imbedded between layers of plastic through a laminating process. 

Today’s sophisticated packaging requires complex electrical and mechanical interfaces, and as miniaturization demands increased performance from each component, flexible printed circuits are one of the few products that can provide the necessary mechanical and electrical interfaces in a cost-effective solution. The technology is ideal for small electronics, such as cameras and cell phones, and it’s a key innovation behind numerous common and specialty applications.

But for flex circuits to perform the way their designers intend, a total integrated design and manufacturing package is required, one that includes not only the flex substrate and its circuits, but virtually every minuscule component that is attached to it.

Flexible printed circuit assembly is much different than assembling a printed circuit board. Good circuit design, materials, panel layout, temperatures, component placement requirements, and oven flow are all critical factors in creating an assembly that works the first time.

Design to Deliver

There is always the potential for improvement in the product development process, which impacts the time to market. One manufacturer of flexible circuits, PFC, actively advocates that customers and prospects utilize the company’s expertise in the early stages of development to assist in creating a buildable, producible, and repeatable solution. The upfront assistance saves the customer both time and money in the long run. PFC calls this concept “design to deliver.”

• Understanding the application is key to a solid design. Interconnect parameters, mechanical considerations, product environments, signal speeds, and shielding are key to design and cost considerations. Early involvement and documenting of multiple options, along with their advantages and weaknesses, is critical to prevent wasted time and costly choices that may not be the best practice or best fit for the fabrication or the end application.

• Costing can begin at the concept stage and can also be a measure of progress along the production path. The more information, and the better the quality of the information, the more reliable are the cost estimates, which results in fewer surprises and critical supplier assumptions.

• Documentation requirements. Complete documentation packages are required to ensure manufacturability, testing parameters, assembly instructions, and technical requirements. This requires a tight communication link between PFC and its customers. Document packages should include:

• Assembly drawings

• Mechanical drawings

• Gerber files

• Drill files

• Specifications and quality requirements

• Bill of materials

• Tooling. The quantity, delivery, and estimated annual usage all impact the fabrication methodology and tooling approach. Pricing targets prevent a fine Cadillac from being designed for a short-run market that really wants a Smart Car. If within this package one or more items are missing, the opportunity for error arises; a clean package will again result in fewer surprises.

Cost of Ownership

New and specialty products may require a custom flex circuitry design. However, the commercial aspects of having a flex designed, built, and assembled — and using two to three different subcontractors — leads to many hidden costs. Handling issues, logistic management, component mark-ups, lead-time considerations, shipping costs, and potential for miscommunication must all be factored into the process. Technically, material considerations, temperature variances, assembly techniques, component tolerances, test parameters, and overall ownership of the design and product can create havoc for any company looking for an electronic interconnect device. Companies such as PFC provide products that are adaptable yet perform as if they were custom designed, leading to an overall lower cost of ownership.

As flexible printed circuitry becomes essential to new product design in a multitude of areas, a truly flexible product — one that is versatile enough to meet many different needs, yet repeatable enough to be cost-effective and accessible — is the key to meeting the timelines of the marketplace. Yet it is essential that flex circuits be evaluated closely during the earliest stages of the planning process to truly demonstrate their potential to facilitate leading design.