What is Flex PCB Assembly?
Let’s start with the basics on flex PCB.
A PCB is an initial for the printed circuit board. It is a device that electronically connects and mechanically supports electrical components.
The connections depend on pads, conductive tracks, plus other features drawn on one or more layers of copper.

Flexible PCB Assembly
A flex printed circuit board is a type of technology where you will print the electronic circuits on flexible substrates.
You can identify the flex PCB with other names such as flex circuits, flexible circuit boards, flex boards or flexible electronics.
Flex PCB assembly is, therefore, the process of assembling all the components of the PCB to make a flexible PCB. The material you will use in making the flex PCB might vary from the material for rigid PCB.
Flexible PCB can take any form and can also go around bends.
Flexible substrates that you can use for printing the electronic circuits include peek, polyimide, or transparent polyester film.
Apart from that, you can find screen printed silver circuits on transparent polyester.
Advantages of Flex PCB in Electronics
Flexible PCBs offer a range of benefits in electronics. These include:

Part of flexible electronic
i.Packaging and Reduction of Weight
The design of the flex PCB increases flexibility and saves enough room to meet different density mounting designs.
Normally, the flexibility also enhances reliability and reduces the process of assembly. It is the solution to miniaturization and movement of electric products.
Flex printed circuits are light and thin, therefore, making the packaging quite simple and substantial.
It allows for the minimization of space with their ability to fold. It is possible to minimize space by applying the 3D geometry packaging.
Using the flex circuits can reduce the weight of the device in comparison to using wire harnesses and wires.
It replaces the wires and reduces the errors that are common in wired assemblies.
ii.Durability and Reliability
Flex circuits increases reliability of devices by eliminating different interface connections such as solder joints. The fewer the number of interconnections in a circuit the fewer the potential sources of failure.
Flex circuits low mass and ductility reduces the impact of shock and vibration therefore increasing the performance.
Also, the thermal stability of the material polyimide allows the flex circuits in high temperature applications. It reduces the possibility of thermal mismatch as compliant base films place less stress on the solder joints.
Apart from that the flex circuits are also resistant to UV exposure and radiation. It is an excellent circuit that offers perfect resistance to chemicals such as gasses, oils and acids.
iv.High Temperature Applications
Polyimide is not only a flexible material but also a good conductor of heat. It allows for the exposure of the flex circuits to high temperature applications up to 400C.
Flex circuits do not expand and contract unnecessarily with the use of the polyimide materials.
v.High Density Applications
The properties of flex circuit materials allow it to perform better in high speed designs. The materials allow for better control of impedances.
Flex circuit assembly involves narrower lines and, therefore, gives way to higher population of high density devices.
A high population of denser devices on the flex circuit gives more space for more product features.
vi.Shielded Applications
Flex circuits allow for radio frequency and electromagnetic interference shielding in different devices. It uses different types of materials such as copper layers, silver ink, and EMI shielding films.
vii.Components or connector assembly
Flex circuits accepts different connectors and components onto rigid PCB designs. It has integrated ZIF contacts providing simple modular interfaces to the environment of the system.
Other connections to rigid circuits include crimped contacts, direct solders, and ZIF connectors.
Quality Testing in Flexible PCB Assembly Process
The greatest joy of a manufacturer always comes when they successfully complete a customer’s design.
The design is never complete until the manufacturers test its functionality.

Flexible PCB assembly quality assessment
Let’s have a look at some of the testing processes for the flex circuits.
·Electrical testing of Flex PCB
There are two main types of flex PCB electrical testing methods. These include simultaneous flex circuit electrical test for mass production of flex circuits.
Quality tests with probes
The method many manufacturers use for testing other flex circuits include isolation or flying probe testing. Flying probe depends on a machine to fix and test the electrical circuit.
·Dimensional tolerance for Flex PCB
Dimensional tolerance test for flex circuits test the tolerance of the circuit according to its dimensions. Testing dimensional tolerance seeks to know if the dimensions of the flex circuit work well.
Manufacturers often design flex circuits of diverse dimensions. It is, therefore, important to test functionality before releasing to customers.
·Thermal testing for Flexible PCB
This test seeks to know if the flex circuit will withstand certain heat ranges. It involves using the flex circuits in different temperature ranges.
At the end of the test, manufacturers will be able to know the specific heat range of the flex circuit. With this information, a customer will know the conditions of operating the flex circuit.
·Ionic Concentration testing of Flexible PCB
Ionic concentration in a flexible circuit will determine the functionality of the product.
During the manufacturing process, ionic residues might be left on the device. These ionic concentrates might cause problems on the flex circuit in humid conditions.
Monitoring ionic concentration is an indication for the cleanliness of the flex circuit.
Flexible PCB Assembly Process
After going through the quality testing essentials, let’s have a look at the assembly process for flex circuits.

Flexible PCB assembly process
There are two main assembly processes for the flex circuits as you are about to learn in this chapter.
The assembly process of flexible circuits takes a completely different treatment method. In this case, the treatment method requires you to be very careful.
Remember, the flexible circuits are often delicate and any slight mistake might compromise the functionality of the circuit.
Most of the manufacturers would often have the design that you need first. As you submit the design, accompany it with all the design notes and requirements of the flex circuit.
These details allow the manufacturer to check on the functionality and manufacturability of the flex circuit.
So, the design will go through a DFM check for all design specifications for any problematic features.
It will help in reducing manufacturing costs as it eliminates the unforeseen errors. After adjusting all the issues, you are free to proceed with the assembly process.