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Flexible PCB Manufacturing: How Are Flex PCBs Made?

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Flexible PCB manufacturing
Flexible PCB manufacturing
Resource: https://www.edn.com

How is your flexible circuit board made? This guide details all the steps involved in flexible PCB manufacturing by tracing them from when the manufacturer designs the board to when the actual flex PCB fabrication and testing takes place. But before delving into the process, let’s begin by looking at what a flexible PCB means.

What is a Flexible PCB?

In simple terms, a flexible printed circuit board, or flex PCB in short, is used to mean a type of electronic circuit board that flexes and can be bent or folded. To enable that, the PCB is made using a thin and flexible insulating material, commonly polyimide, with conductive but flexible traces of copper printed and etched into it.

Flexible PCBs offer several advantages: They are lighter and thinner, which makes them ideal for portable and wearable devices. They can also be shaped to fit into irregular spaces, a property that makes them usable where space is limited.

Other advantages of flexible PCB include their higher resistance to shock and vibration, which makes them more durable than rigid PCBs in harsh environments. Overall, flexible PCBs are a versatile and useful in abroad range of applications.

How to make flexible PCB
How to make flexible PCB
Resource: https://www.youtube.com/watch?v=cGFYCFK3jSk

Flexible PCB Manufacturing

Flex PCB manufacturing starts with designing the board structure and layout. This involves the use of design software. The required materials are also determined and sourced. These typically include the substrate, copper traces, coverlay and adhesives or stiffeners if needed.

Flexible PCB Design

Using PCB design software, the specific flex PCB layout is determined, usually based on the intended application and customer specifications. The layout involves placing the components on the board, routing the traces that connect the components, and adding any necessary electrical components such as resistors, capacitors, or inductors.

The design is then checked for any errors. This can be done using specialized software that checks for issues such as incorrect trace widths or clearance violations.

Once the flex PCB design has been checked and approved, Gerber files are created. These contain the information needed to manufacture the PCB, including the placement of components and the routing of traces.

Flexible PCB Material Materials

Appropriate materials are selected, usually based on the requirements of the project, such as the level of flexibility required or the operating temperature range.

Common flexible PCB materials include polyimide and polyester for the base or substrate layer, copper foil for the conductive layer or layers, and (if needed) acrylic and epoxy resins for the adhesives.

In some cases, a stiffener is added. These materials are first chemically cleaned, and then prepared for the PC fabrication process.

The steps for flex PCB fabrication, although almost similar to those of rigid boards, are more detailed. This because the requirements for this type of circuit board are stricter, and manufacturers must tailor each circuit board to its specific use.

Flexible PCB Manufacturing Process

The flexible circuit board manufacturing process involves several stages of board fabrication and quality control. This helps to ensure the PCBs meet the required specifications — and that they’re free from defects. The specific process may vary across different flexible PCB manufacturers, depending on the requirements of the project. Generally it involves these steps:

Flexible PCB Laminate

  • The flex PCB substrate, which is commonly polyimide, is laminated to a copper sheet — or sheets depending on the number of layers. The method to attach the two materials together may vary. Traditionally, an adhesive is used. This can be acrylic or epoxy.
  • The modern way of laminating the polyimide and copper sheet involves chemical deposition or sputtering. This is called adhesiveness lamination. Note that a flex PCB manufacturer may choose to source and use pre-laminated films.

Flexible PCB Printing and Etching

  • The flex PCB circuit’s pattern is printed onto a film. This involves using a photoresist coating with the required circuit or pattern, which is then developed using UV light to leave the circuit pattern on the film.
  • The resulting pattern is then chemically etched. This leaves the areas with the photoresist coating intact. This is what will be used to represent the copper traces or conducting patterns of the flexible circuit board.

Flexible PCB Via Drilling

  • A high-speed machine drills out the holes that will be used to mount the electrical components during assembly, or vias to connect the different layers electrically, among other functions.
  • Through holes are chemically pated with a conductive material, typically copper, just as they would when making rigid PCBs. For tiny flex PCB via drilling, greater accuracy is a necessity, and laser drills are commonly used.

Flexible PCB Printing

  • After drilling holes, the panel is now coated with a film of photoresist material. This is a material that will harden upon exposure to light. A laser then scans out the outline of the circuitry that was created during the design stage.
  • The flexible PCB printing process results in the areas that the laser hit hardening, while the areas that were not hit remain soft. The soft areas are them washed out.
  • Next, a chemical is used to remove the copper in the exposed areas, in a process called etching. The photo resist is then chemically removed. Just like with standard rigid boards, this leaves a pattern of the required circuitry.

Flex PCB Coverlay

  • The flex PCB coverlay or film is added. This is similar to the solder mask of rigid boards and serves to protect against damage by the elements. In most cases, this is a polyimide layer that is applied using an adhesive or without.
  • A covercoat may also be used instead. This is a material coating unlike coverlay, which is usually installed as a thin film. A covercoat will also need curing in an oven.

Flexible PCB Punching

  • The finished circuit board is now punched (or blanked) to the required board sizes and shapes. Although the type of machine varies across manufactures, most flexible PCB punching presses are hydraulically operated.
  • Blanking knives that are made in the shape of the required board are also used. This can punch several layers of the PCB simultaneously and help reduce production time and costs.
  • Finally the flex circuit boards are checked for quality and either shipped to client — or assembled with electronic components before shipping.

The flex PCB manufacturing process is an extensive procedure that involves selecting the right materials, designing and fabricating the board, and testing it for quality.

At Jamindo PCBA, we provide custom flex PCB manufacturing solutions to fit your individual needs. Our services as a leading PCB manufacturer include both flex PCB manufacturing and flex PCB assembly. Contact us today to get started on your next project!

Conclusion

From material selection to design and fabrication, the flex PCB manufacturing process requires careful balance of expertise and collaboration to ensure the project’s success. This guide is an overview of the most important flex PCB manufacturing steps: From when engineers create the layout to when the finished circuit board is cut into the required sizes and inspected for quality.

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