Flexible Circuits Differ From Traditional PCBs
The distinction between a traditional printed circuit board (PCB) and a printed flexible circuits is often overlooked. While they both serve a similar electrical function, there are significant differences in their mechanical and structural design that can significantly impact the final product’s cost. This article will provide a brief overview of these differences and highlight the benefits of using flexible circuits in your electronics design.
In short, the primary difference between a flexible circuit and a rigid PCB is that a flexible circuit can be bent or flexed while a rigid PCB cannot. This flexibility offers a number of design and manufacturing advantages that can greatly reduce your overall circuit cost.
A flexible circuit consists of a base layer of conductive material and a coverlay that provides protection. Depending on the application, different types of coverlay materials are used including polyimide and epoxy. Rigid PCBs use glass epoxy FR4 as their base layer and have rigidized sections that prevent them from bending. In most applications, rigid PCBs are the preferred option unless there is a technical reason to use a flexible circuit.
Printed circuit boards are typically made up of several layers, each with specific physical and electrical properties. The core of the circuit board is the dielectric layer, which is then covered with a conductive metal and plated through holes for interconnection. The most common conductive metal is copper foil, which can be etched to create the required traces.
How Do Flexible Circuits Differ From Traditional PCBs?
The base layer of a flexible circuit is most often made from a polyimide material. It has good flexibility, but does not offer the same mechanical support and dimensional stability that is found in the glass epoxy FR4. Generally speaking, a flexible circuit is used when the application requires a large number of plated through-hole connections or surface-mounted components.
Single sided flexible circuits are the most basic type of flex PCB and consist of a single conductive metal layer that is bonded to one side of the substrate. In most cases, this is enough to meet the requirements of the given application.
A double sided flexible circuit has a copper layer on both sides of the substrate, connected through metallized plated thru-holes. This type of flex circuit is the most commonly utilized in electronic devices, and it offers a range of useful features.
The most advanced flex circuits are multi-layer boards with complex interconnections, shielding and other design elements. These boards are designed to withstand a variety of mechanical and environmental conditions, and they can be manipulated multiple times during installation or operation without the risk of failure. This versatility allows for the creation of electronics that are able to fit into small or irregularly shaped spaces that would be impossible with standard rigid PCBs. They also make it possible to utilize narrow spaced conductors which can increase device population density, decrease weight and lead to improved airflow. All of this translates into lower production and shipping costs, reduced assembly and maintenance time, and higher overall product performance.