Flexible Printed Circuit Board Introduction and Importance

A PCB (printed circuit board) is a circuit that provides mechanical support for electrical components connected by conductive copper wires. It is the basic building block of many electronic projects, opening the door to small, compact, and unstable designs.

The PCB you see today has evolved into more complex circuit boards over the years, compared to the circuit boards installed in TVs in the 1990s with the circuit boards used in modern LED designs and smartphones.

PCB boards are divided into single-layer, double-layer, multi-layer, rigid, flexible, rigid flexible combination boards, aluminum substrates, and other types. Introduce flexible circuit boards.

What is a flexible PCB?

Flexible PCB, also known as flexible printed circuit board or flexible circuit, is a special type of circuit board that can be bent into the desired shape. They are widely used in high-density and high-temperature applications. The flexible design is composed of polyimide or transparent polyester film as the substrate material, which has high heat resistance and is very suitable for welding and installing components.

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The flexible circuit has a trace conductive layer made of copper and is combined with a polyimide dielectric layer. The thickness of the copper conductive layer can vary from 0.0001” to 0.010”, and the thickness of the dielectric material can vary from 0.0005” to 0.010”. An adhesive is required to bond the conductive copper layer to the substrate; sometimes, vapor deposition can also easily connect the copper to the substrate.

The choice of materials for manufacturing flexible circuit boards is tricky and depends on many factors, including chemical and mechanical resistance, current, temperature, capacitance, and bending type.

Flexible designs are more reliable because they have fewer interconnects, ensuring fewer solder joints and contact crimping. Due to their flexible bending ability, these circuits require less space, and they only cover 10% of the area compared to rigid circuit boards.

Flexible PCB manufacturing process：

The single-layer flexible PCB, as the name suggests, contains only one conductive layer that sits on the flexible dielectric film. The electric components rest on only one side of the PCB.

Double Layer Flexible PCB
The double-layer flexible PCB offers a conductive layer on both sides of the PCB, allowing you to connect electrical components on either side of the conductive layer.

Flexible PCB manufacturing process：
Polyimide is used as a substrate material for the manufacture of flexible printed circuit boards. This material is more expensive than FR-4, so it needs to be used with caution. In order to use polyimide materials correctly, nesting techniques need to be used to keep the circuit boards close to each other.

Cycle
The service cycle ensures the service length and circuit components, that is, the amount of additional materials you add that exceed the designer’s limit.

Determine the conductor size
Thin copper is used as a conductive material on the board. Thin copper is responsible for the flexibility of the circuit and makes it suitable for dynamic applications.

Etching
The etching process is used to compensate for any isotropic loss in the manufacturing process. In this process, the thickness of the copper foil is half of the line width loss. Factors that affect the line width include conductors, etching masks, and the different types of conductors used.

Route selection
The routing is simple. Wiring ensures that stress is reduced and bending and folding are improved.

Ground plane
Creating a ground plane will reduce the weight of the circuit board and bring better circuit flexibility.

Next, you need to create holes before applying rounded corners to increase the pad area to disperse the stress. Then add the adhesive film for dynamic flexible circuit applications. Next, you need to apply a screen-printable liquid coating first, and then add imaginable liquids and thin film polymers to act as solder resist layers and prevent internal and external damage to the circuit.

Types of flexible PCBs：
Flexible printed circuit boards are divided into four different types.

Single layer flexible circuit board
A single-layer flexible PCB, as the name suggests, contains only one conductive layer located on the flexible dielectric film. The electronic components are only located on one side of the PCB.

Double layer flexible circuit board
The double-layer flexible PCB has conductive layers on both sides of the PCB, allowing you to connect electronic components on both sides of the conductive layer.

Multi layer flexible PCB
A multi layer flexible PCB has three or more conductive layers separated by a dielectric material. Irregular lamination ensures high flexibility of the circuit board, and the lamination thickness of the adhesive area is usually small.

Rigid flexible binding plate
Rigid flexible binding board is a combination of the rigid and flexible circuit board, which can provide higher component density compared with other circuit boards.

HDI flexible circuit board
HDI stands for high density interconnection. Compared with other circuit boards, these circuit designs are efficient, reliable, and have a better design, construction, and layout. Due to the thinner substrate material used to manufacture these boards, HDI flexible boards can provide better electrical performance and reduce package size.

Flexible PCB Importance in the modern world：

Flexible boards can be bent into any shape, which is why they are widely used in dynamic bending and static applications. Dynamic circuit boards are used for regular bending, while circuit boards for static applications provide minimal bending.

Flexible circuits are designed to withstand high temperatures between -200°C and 400°C, so they are very suitable for drilling measurements in the oil and gas industry.

Flexible circuit boards are convenient in many applications, but they cannot be used instead of rigid circuit boards. Because rigid plates are cheap and can be installed in high-volume automated manufacturing applications.

Flexible circuit boards are ideal for applications that require better performance, high precision, precision, and regular bending. Applications of flexible circuit boards include：

Bottom line, if you have flex circuit design or flex printed circuit board needs, we can help. contact us