What are the Steps Flexible PCB Manufacturing Process

Engineering Knowledge
9 min readJun 11, 2023

Hello readers welcome to the new post. In this post, we will learn What are the Steps Flexible PCB Manufacturing Process. Flexible Printed Circuit Boards are very popular due to their features to provide good flexibility and reliability in different electronic applications. They provide many advantages over rigid PCBs, like enhanced space utilization, good reliability, and increased design flexibility. In this post, we will learn different factors for the flexible PCB manufacturing process. So let’s get started with Flexible PCB Manufacturing Process

Introduction to Flex PCB

Flexible PCBs, also called flex circuits or flex boards, are electronic interconnects that can twist, bend, and fold without having an effect on their functionality. They have a thin, flexible substrate created by polyimide or polyester, which helps them to conform to complicated structures and fit into tight spaces. Flex circuit manufacturing comes with different steps, ensuring the manufacturing of high-quality, reliable boards.

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Understanding Flexible PCBs

Before going to discuss flexible pcb manufacturing, let’s discuss the fundamental parameters of flexible PCBs. These circuit boards have 3 main layers: the substrate, conductive traces, and protective cover layers. The substrate work as the base and offers flexibility, while the conductive traces, created with copper, establish electrical connections between components. The protective cover layers protect the traces and make sure durability.

Benefits of Flexible PCBs

Flexible boards provide many advantages that make them best for various industries. Firstly, their flexibility is used for seamless integration into compact and irregularly shaped devices, optimizing space use. 2nd, their less-weight nature decreases the total weight of the electronic assembly. Also, the absence of connectors and the ability to remove complicated wiring harnesses make simple the assembly process, decreasing manufacturing time and costs. Though, the flexibility of these circuits decreases the chances of mechanical failures due to vibrations or shock, and improves overall reliability.

Designing a Flexible PCB

Designing a flexible board needed careful consideration of the application’s needs, mechanical constraints, and electrical features. It is necessary to select the accurate substrate material, find the number of layers, and define the circuit’s layout. The design process consists of optimizing the placement of components, routing traces, and making sure of proper signal integrity. Advanced design software and professional skills in flex circuit design are important to get optimal results.

Steps in the Flexible Printed Circuit Manufacturing Process

Step 1: Material Selection

The first step in flexible printed circuit manufacturing is selecting accurate materials. The selection of substrate material is based on parameters like thermal stability, flexibility, dielectric properties, and cost. Polyimide and polyester are commonly used due to their high-temperature resistance, excellent flexibility, and electrical insulation features. The conductive traces are made of copper due to its good electrical conductivity.

Step 2: Circuit Design

After the selection of materials, the next step is circuit design. That makes a schematic diagram of the circuitry, explaining the component placement and determining the routing of traces. The circuit design makes sure optimal electrical performance, signal integrity, and adherence to design rules.

Step 3: PCB Layout

In this step, the circuit design is converted into a physical layout. The layout consisting placing components on the flexible substrate and routing the traces to make electrical connections. Attention to detail is important to confirm the accurate alignment of components and reduces signal interference.

Step 4: PCB Printing

After the layout is completed, the PCB board printing process started. Here transferring the circuit design onto the flexible substrate with the use of different techniques like inkjet printing, screen printing, or photolithography. This step needs accuracy to get the required circuit pattern.

Step 5: Component Mounting

Once the circuit pattern is printed, the next phase is component mounting. Surface Mount Technology is commonly used to connect electronic components on flexible PCB. The components are carefully connected and soldered onto the substrate with the use of specialized instruments, make sure proper alignment and solder joint integrity.

Step 6: Soldering

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After component mounting, the flexible boards undergo a soldering method to make reliable electrical connections. Solder paste is applied on the exposed pads, and the PCB board is subjected to a reflow soldering process. The heat melts the soldering paste, making a strong bond between the components and the traces.

Step 7: Testing and Quality Control

To make sure the functionality and reliability of the flexible board, comprehensive testing, and quality control measures are used. Automated optical inspection and electrical testing are done to detect any manufacturing faults, like short circuits or open circuits. This step confirms that only high-quality boards proceed to the next phase

Step 8: Final Assembly

When the flexible board passes the testing and quality control stage, it is ready for final assembly. Additional components and connectors can be connected based on certain application needs. The final assembly confirms the complete integration of the flexible board into the required electronic device.

Step 9: Inspection and Packaging

The last step in the flexible printed circuit manufacturing process is inspection and packaging of the board Visual inspection is done to check for any cosmetic defects or physical damage. The boards are carefully packaged to protect them during transportation and storage, making sure they reach users in optimal condition.

Flex PCB Manufacturing Process & Advantages — JLCPCB

JLCPCB has introduced flexible PCBs, which facilitate common PCB assembly and is now providing a special pricing beginning at $25 for five pieces. JLCPCB has also offered $54 signup vouchers for new users at https://jlcpcb.com/ Never allow prohibitive development expenses to stifle your creativity

The following stages are necessary for all PCB manufacturing processes, like the JLCPCB Flex PCB manufacturing process, to produce a successful Flex PCB.

JLCPCB Flex PCB Manufacturing Proces

Flex Circuit Design:

Using computer-aided design (CAD) tools, the flexible PCB is initially designed. The circuit architecture, component location, and any unique demands for the flexing or bending of the PCB will all be part of the design.

Material selection:

The right substrate material must next be chosen for the flexible PCB. Films made of polyester (PET) and polyimide (PI) are the most often utilized materials. These materials are flexible, tolerate high temperatures, and have strong electrical insulating qualities.

Electrical paths are fabricated on the Flex PCB using a conductive material. Due to its exceptional conductivity, flexibility, and durability, copper is the most widely utilized conductive material.

The layers of the Flex PCB are joined together using an adhesive substance. Usually constructed of epoxy, acrylic, or silicone, a sticky substance.

Coverlay material: The conductive material on the Flex PCB is shielded with this material from environmental elements including moisture, dust, and physical harm. The two materials used for Coverlay the most frequently are polyester and polyamide.

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Solder mask material:

During the soldering process, this material is utilized to shield the conductive traces on the Flex PCB. Epoxy or other photo-imageable materials are frequently used to make solder masks.

Other parts, like as stiffeners, connectors, and component attachment adhesives, are also utilized in the production of Flex PCBs in addition to these materials. The particular materials employed depend on the Flex PCB’s design and intended function.

Material preparation:

The surface of the substrate material is then cleaned and etched to provide a smooth, clean surface for the printing of the circuit.

Circuit printing:

A crucial procedure in the production of Flexible PCB is photolithography. Using photoresist and etching, the circuit pattern is transferred from a planned layout to the substrate material in this procedure.

The application of a photoresist substance to the substrate surface comes first after the materials have been prepared. UV light causes the photoresist, a light-sensitive substance, to become harder. Positive and negative photoresists are the two categories of photoresist materials utilised in the production of Flex PCBs. The next step is photomask alignment, which involves placing a photomask over the substrate and shining UV light through it to expose the photoresist material in the desired pattern.

The circuit layout that will be printed on the substrate is contained in the photomask. To guarantee precise placement of the circuit layout on the substrate, the photomask must be aligned.

The photoresist material that was not subjected to UV light is removed off the substrate after it has been exposed to UV light. Only the hardened photoresist that matches the circuit layout remains after the development process eliminates the soft, unexposed photoresist material. The following operation is called etching, and it entails removing the copper from any places that aren’t covered by the hardened photoresist. This is accomplished by dissolving the exposed copper with an etchant solution, leaving just the desired copper pattern on the substrate.

UV Exposure

Etching

The leftover photoresist material is removed from the substrate using a solvent that dissolves the photoresist after the circuit has been transferred to the substrate material, leaving just the printed circuit design on the substrate.

Component placement:

The components are then adhered to the PCB once the circuit layout has been produced. Surface mount technology (SMT) or through-hole technology can be used to mount components.

Soldering:

Then, either reflow soldering or wave soldering methods are used to attach the components to the PCB.

Testing:

A critical stage in the production of flexible printed circuit boards is testing. Testing is done to make sure that the Flex PCB complies with the necessary electrical and mechanical requirements and is error-free.

Flex PCB Testing

In the production of Flex PCBs, the following testing techniques are frequently used:

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Electrical testing: This entails examining the Flex PCB’s electrical connections. A test fixture that delivers a voltage to the circuit and monitors the current flow is attached to the Flex PCB. The electrical properties of the Flex PCB, such as resistance, capacitance, and impedance, are measured in addition to any circuit breaks or shorts being found.

Visual inspection:This entails visually evaluating the Flex PCB to find any flaws such cracks, scratches, delamination, or alignment issues. To verify that the Flex PCB complies with the necessary mechanical requirements, the examination is carried out under a microscope or magnifying glass.

Environmental testing: This entails exposing the Flex PCB to different environmental factors, including vibration, humidity, and temperature. The Flex PCB is put through tests to make sure it can survive the anticipated environmental circumstances and function dependably in them.

Functional testing: This entails putting the Flex PCB through its paces to make sure it serves its intended purpose. A test fixture that mimics the intended application is connected to the Flex PCB, and its performance is assessed in comparison to the predicted parameters.

X-ray inspection: This entails scanning the interior layers of the Flex PCB with X-rays to look for flaws like voids or delamination. When inspecting the Flex PCB, X-rays are very helpful for finding flaws in the solder joints and other difficult-to-access regions.

Stiffener attachment:

In order to stabilize and protect the flexible PCB during handling and use, a stiffener is lastly connected to it. The stiffener is normally connected using an adhesive and might be constructed of materials like FR4 or steel.

Attach Stiffener

Because it supports and shields the flexible PCB during handling and usage, the stiffener is a crucial part of the PCB. The stiffener stops the PCB from bending or flexing over the limits that were intended, which might harm the circuit or its components. Additionally, it aids in preventing the PCB from breaking or splitting as a result of force placed on the circuit during bending or flexing.

Advantages of Flex PCBs

Flexibility

Flex PCBs, as the name implies, are flexible and can bend, twist, and flex without harming the board’s electrical connections. They are therefore perfect for bending or twisting applications like wearable technology or automobile sensors.

Space Saving

Rigid circuit boards cannot be made to fit into small areas, but flexible PCBs can. Devices may now be more compact and smaller because to this.

Durability

Extreme heat and vibrations are two conditions that flex PCBs are made to survive. They are therefore perfect for use in the automotive, military, and aerospace sectors.

Cost-effective

By doing away with the requirement for connections and cables, flex PCBs can lower the cost of product development. The production process is streamlined, and fewer components are needed.

It’s essential to have high-quality PCBs if you want to realize your amazing PCB ideas. JLCPCB is dedicated to upholding the highest manufacturing standards, and as such, has made investments in state-of-the-art machinery and partnered with eminent global raw material suppliers. JLCPCB also has five self-operated intelligent production sites. JLCPCB is able to cut manufacturing costs via the use of economies of scale, pass the savings through to consumers, and minimize the cost barrier to hardware innovation. Additionally, JLCPCB provides new users with up to $54 in registered discounts. To purchase premium flex PCBs, register and upload your Gerber files here: https://jlcpcb.com/?from=getquote.

Author: Henry

http://www.theengineeringknowledge.com

I am a professional engineer and graduate from a reputed engineering university also have experience of working as an engineer in different famous industries. I am also a technical content writer my hobby is to explore new things and share with the world. Through this platform, I am also sharing my professional and technical knowledge to engineering students.

Originally published at https://www.theengineeringknowledge.com

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