Component on A Flex PCB: All You Need To Know


Oakley Mae

Home » Blog » Assembly » Component on A Flex PCB: All You Need To Know

Understanding the component of a flex PCB is critical since it determines the function and operation of the PCB.

And the best designers and engineers know that efficient electronic device starts with selecting the best PCB components.

Generally, a circuit board has many components that we can broadly categorize as mechanical and electrical. 

The mechanical components provide mechanical supports and have nothing to do with power or signals.

However, we further categorize electrical components into passive and active options that offer electrical connections to the PCB.

And electrical components include resistors, diodes, capacitors, and ICs. 

Today’s piece helps you understand flex circuit board components to create reliable products. Let’s get rolling.

Table of Contents

What Is A Flex PCB

A flexible PCB

(A flexible PCB)

Rigid circuit boards have been around for years, with significant applications in designing electronics.

However, these devices can’t fit into tight spaces and won’t support functionalities in harsh conditions.

Therefore, manufacturers have developed flexible PCBs, high-functional boards that can bend to fit into smaller, tight spaces. 

Most aspects of flexible circuit boards, like materials and components, are similar to those of rigid boards.

But flexible PCBs have additional features like the ability to work under harsh conditions and less risk of failure.

Generally, flexible PCB supports high circuit density and uses various process technologies, including through-hole and surface mount technology.

How Do You Connect Components on A Flex PCB

A PCB with components

(A PCB with components)

Soldering is the most common approach to connecting components on a flexible PCB.

This process involves employing filler materials known as solder to join the components to the board. Generally, the process happens at low temperatures. 

Soldering PCB Components

First, find the right equipment, like a soldering iron, and clean the circuit board surface.

Next, put the component you want to solder into the PCB hole, with the legs coming out of the solder pad side.

Therefore, bend the component’s legs slightly so that it doesn’t fall off when you position the board upside down. 

You can then carefully solder components on the board, ensuring the solder doesn’t overflow.

Moreover, ensure you observe safety precautions not to damage the components or injure yourself. 

Placing Components On The PCB

Placing components on a flexible circuit board is quite straightforward.

First, group the components by function and keep the details from the dissipating area.

Next, put the board-to-wire connectors closer to the board edge.

Afterward, standardize the component orientation before creating copper trace spaces. 

Flex PCB Mechanical Components

Generally, we categorize electrical components into electrical and mechanical components.

Mechanical components employ “the mechanized process,” which has everything to do with their metal material. 

The mechanical component is mainly made of copper, aluminum, bronze, and steel.

And unlike electrical components that allow current and signals to pass through, mechanical components primarily offer mechanical support. 

Flex PCB Electrical Components

An electronic circuit board with components

(An electronic circuit board with components)

Electrical components are likely what you see first when your eyes land on a circuit board.

We place these components on the circuit board using the surface mount or through-hole technology.

You’ll have to solder them to remain firm on the board. 

We categorize flexible PCB electrical components into passive and active components. 

Passive Components

A passive component doesn’t directly control the flow or transfer of electrical energy.

Most passive components come with two leads; you can identify them through the silk screen printing on the top. 

Let’s explore some of the common flexible circuit board passive components below. 

Capacitors: A capacitor is a component used to store charge in a circuit.

We identify them with the capacitance value ‘C,’ and we measure the charge in Farads. 

Fuse: This safety component provides flex PCB with overcurrent protection.

Without it, components in the circuit could easily blow up thanks to overcurrent situations. 

Resistors: This component regulates or limits current flow in the circuit.

Therefore, they lower the voltage or reduce the current in any part of the circuit.

You can identify resistors by their blue or green bands. 

Connectors: As the name implies, we use these components to integrate and connect multiple components.

Also, you can use them to link various circuit boards. Generally, you can identify a connector by checking for the initial ‘K.’

Inductors: We use inductors in the circuit to store power and charge.

They’re denoted by the letter ‘L,’ and you can identify them by marking ‘H.’Battery: Lastly, a battery stores charge and supply it to power the circuit.

Therefore, you can identify them by checking for the letter ‘B’ or ‘BT’ on the body.

Active Components

An integrated circuit

(An integrated circuit)

Passive components are directly involved in carrying signals and currents.

Also, you’ll get these components in both through-hole and surface mount technologies.

Let’s explore the common active components below.

Integrated Circuits: This is the powerhouse of any circuit board, denoted by ‘IC’ or ‘U.’

Generally, it holds together the different PCB building blocks, including but not limited to timers, microprocessors, memory, oscillator, and amplifier.

Therefore, they assist with saving flexible PCB space. 

Diodes: These components usually regulate voltage in a single direction.

In simple terms, it behaves as a one-way switch allowing current to flow through in one direction.

Some of the common diode types include: 

Identifying Through-Hole Components

A component being inserted into through-holes

(A component being inserted into through-holes)

Through-hole is one of the technologies we use when designing circuit boards.

It involves creating holes in the circuit board to insert components.

Therefore, the components you place using this method have long leads and are large-sized.

Most components that you attach to a pad using solder are through-hole components. 

What Are SMT Components?

SMT components don’t use holes but are mounted atop the circuit board.

Below are some characteristics to identify these components on the circuit board:

  • They have shorter leads
  • The components depend on soldering the surface to the copper pads
  • They lack holes in the circuit board


Do flexible PCB components age?

Absolutely! Flexible circuit components will age due to many factors. First, the components age due to long-term usage.

Also, expect the component to age faster when something goes wrong during manufacturing.

This could be as simple as not using reliable coverlay materials, thus accelerating corrosion. 

Therefore, after your components have been in service for a long, replace them immediately.

Generally, most components like transformers, transistors, and diodes have a service life of about ten years. 

To prevent component aging, ensure you employ quality materials during PCB fabrication.

Furthermore, it would be best if you used the proper soldering techniques.

This includes but is not limited to avoiding fluid leakage and chemicals. 

How can you identify PCB components during repair?

When your flexible PCB component gets damaged, you can repair or replace it rather than buy a new PCB.

But to do this, you must first identify the component to repair. Therefore, use any of the below options:

Check the schematic: The schematic shows the component connections and their corresponding value and types.

Generally, a schematic is available on the board, in the manual, or online.

The schematic makes identifying damaged components easier, determining their parameters, and making suitable replacements. 

Testing the components: But what if you don’t have a schematic?

In this case, use a logic analyzer, oscilloscope, or multimeter to determine faulty parts.

Therefore, you can check the test results against what’s on the data sheet or schematics. 

Final Remarks

In conclusion, any circuit board is incomplete without functional components.

And we categorize circuit board components into mechanical and electrical components.

Generally, mechanical components only provide mechanical support to the board and have nothing to do with signals or power. 

However, electrical components facilitate the transfer of signals and power through the circuit board.

Therefore, these components include resistors, diodes, transistors, connectors, and integrated circuits. 

Moreover, we place components on the circuit board using either surface mount or through-hole technology.

With through-hole technology, you must further solder the components to keep them firm on the board.