Understanding the Structure of Flexible Printed Circuit Boards

Flexible printed circuits are designed using photolithographic technology. However, the difference is that the board will be able to flex in an application. Besides photolithography, flexible circuits can also be produced by laminating thin copper strips in PET layers.

Types of Flex PCB Constructions

They can be provided in different construction types. The basic examples of these include:

Single Sided Flex Circuits
Double Access or Back Bared Flex Circuits
Sculptured Flex Circuit boards
Double-Sided Flex Circuits
Multilayer Flex Circuits
Rigid-Flex Circuit boards
Polymer Thick Film Flex Circuit board

Although there are a variety of components within a circuit board’s construction, there are three main parts that need to be present:

Base Material: This consists of a flexible polymer film, and the base for the laminate. The base material provides the primary electrical and physical properties of the circuit.
Bonding Adhesive: As the name suggests, adhesives are used as the bonding agent when creating a laminate. While it is an important element, the adhesive is also a performance limiting element of a laminate.
Metal Foil: In flexible laminates, metal foils are the primary conductive element, on which the circuit paths are etched. Copper is generally the popular option for creating metal foils, as it possesses physical and electrical performance attributes. For example, copper is known for being a soft metal with immense ductility. In terms of electrical properties, copper is a good thermal and electrical conductor.

Each of the above mentioned elements need to provide consistent performance, thus allowing the PCB to meet the demands of an application. Also, the elements need to work in cohesion with all the other materials and components, so that the construction of the flex PCB will be completed with accuracy.

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