In most cases, if one compares the cost per square inch of a flexible circuit with that of a PCB, the later comes out lower. PCBs in general are less expensive to process; use less costly materials and their processes are easier to automate. However the total cost of an electronic package may be significantly less with a flex circuit. There are a number of ways that a flexible circuit can be the lowest cost solution, or best value over other more traditional interconnect products.
Perhaps the biggest advantage of flex over PCB comes when the designer utilizes the full three dimensional packaging capabilities inherent with a flexible circuit. Consider the “origami” flexible circuit in the image below. This is made from one double sided flexible circuit.
The “origami” flexible circuit space craft might be an extreme example, but it does make a point about the possibilities of flex. Using PCB products to create anything remotely resembling figure 1 would require multiple PCB’s, cables and connectors and other components. It would hard to imagine a bill of material that was less than 25 items and the resulting creation would be bulky and unstable. When comparing the cost of flex and PCB’s, the full material cost of all components need to be considered as well as the added labor required building the PCB system. In this example the cost of flex would beat PCB’s hands down!
The less components and connection points you have, the less risk of failure. While the PCB system can be made reliably, the flexible circuit should make most reliability engineers happy since there are far less junctions that could fail in the system. The cost of a field failure is often not figured into the calculated price of a product, but the cost of a field failure can be 10 -1000 times the cost of the purchased unit when you consider the effort to diagnose, service and replace the defective part. This does not even include customer dissatisfaction or the litigation costs if the failure caused damage or injury.
Space and Weight
It is not hard to see that by eliminating connectors and cables and reducing the number of boards, space and weight savings of a flexible circuit may be significant. In today’s market, customers are expecting smaller, faster and lighter products. The evolution of just about every product over the last couple decades involves using less space and weight, integrating electronics, and providing more functionality. Flexible circuits have often been instrumental in enabling these improvements, particularly in densely packaged product designs.
Supply Chain Management
Lean manufacturing drives companies to carry less inventory with faster inventory turns. Per the example above, there are significantly less inventory items to manage with a flexible circuit. Each item needs to be counted, stored, itemized for purchase, and handled multiple times in the supply chain. A design with flexible circuitry can dramatically reduce the number of components and thereby greatly simplify the supply chain management with the system. Supply chain and logistic costs may be hard to capture, but most supply chain managers are striving to reduce the number of inventory items and vendors with the strong belief that costs will go down.
Since flex circuits can be folded, bent and cut out into odd shapes, it has the potential to address complex three dimensional challenges. Designs using PCB’s are often 2 dimensional. Today many of the electronic packaging challenges require three dimensional conceptualization. If a designer looks only at the cost per square inch as a comparison may be very misleading. Using flex may result in an overall cost savings in addition to reducing the packages weight, while reducing inventory and improving reliability.