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Flexible PCB

Flexible PCB

Custom flexible PCB board from PCBSky,  flexible PCB manufacturer in China Shenzhen, a reliable PCB manufacturer.

Because of the advantages (for example, cost, space, and weight savings), flexible and Rigid-Flex-circuit boards have for some projects, they are used ever more frequently. PCBSky produces your flexible circuit boards with the highest quality, either as prototype or as series with 1-10 layers.

The standard surface used is chemical gold (ENIG), the contours are formed according to requirements, preferably using laser cutting, or also with mechanical milling.
You should discuss the selected materials and design for the construction and layout of flexible circuit boards with us in the planning phase; we can assist you to work out the optimum solution!

Flexible PCBs: advantages and disadvantages
Flexible PCB technology, also known as FPC (Flexible Printed Circuit), is continuously growing, with applications in the main electronics sectors, such as consumer, automotive, electro-medical devices, wearables, telecommunications and aerospace. The introduction of flexible PCBs has revolutionized the legacy electrical interconnection techniques, traditionally used to connect multiple parts of the same circuit or of multiple electronic devices. Thanks to the flexible nature of the connection, its compactness, and the high density of electrical connections that can be achieved, the solution based on flexible PCBs allows to obtain a considerable reduction of space, weight and costs compared to an equivalent solution based on rigid PCBs. Flexible printed circuits have replaced many types of wiring, often done by hand, in several applications, reducing the total cost of electrical wiring by up to 70%. The heart of an FPC is represented by flexible films and thin layers of conductive material that make the electrical connection by replacing the traditional wires (think, for example, of the connection between a microcontroller board and an LCD or OLED display), and on which electronic components can be directly attached via soldering or conductive adhesive. Figure 1 shows an example of flexible printed circuit.

Structure of a flexible PCB
As happens for rigid PCBs, FPCs can be divided into single layer, double layer or multi- layer circuits. The main elements of a single layer flexible printed circuit are the following:

dielectric substrate film: the base material of the PCB. The most commonly used material is polyimide (PI), characterized by high resistance to traction and temperature;

electrical conductors: made of copper, they represent the traces of the circuit;

protective finish, made with cover lay or cover coat;

adhesive material (polyethylene or epoxy resin), used for joining the various parts of the circuit together.

The first phase of the FPC manufacturing consists in etching the copper to obtain the traces, while the protective coating (cover lay) must be drilled so as to allow access to the soldering pads. After a cleansing treatment, the components are joined together by rolling. The external terminals/pins, necessary for the electrical connection of the circuit, are protected from oxidation by immersion in tin for welding or in gold. If the circuit has a high complexity, or requires the presence of copper ground shields, it is necessary to switch to a double layer or multi-layer FPC. The manufacturing technique is very similar to that used for single layer flexible circuits, with the difference that in multi-layer FPCs it is necessary to insert PTH (Plated Through Hole), so as to create, where required, the electrical connection between different conductive layers. The union of these materials forms a flexible circuit, in which the adhesive material serves to join the conductive tracks with the dielectric substrate or, in multi-layer flexible circuits, to join the individual layers together. In addition, the adhesive film can also be used for protective purposes, preventing moisture, dust or other external agents from corroding or oxidizing the flexible circuit. In Figure 2 we can observe the structure of a multi-layer FPC. The example shown in Figure 2 includes four conductive copper layers, PTHs (on the right side of the image) and holes for accessing the conductive material (on the left side of the image, on both external layers).

Advantages of flexible PCBs
Being flexible, FPCs can bended and flexed, allowing greater freedom in the design and operation of the application. Flexible circuits can also adapt to small or irregularly shaped spaces, a feature not supported by standard rigid circuits. Another advantage of flexible circuits is that they take up less space, reducing the weight on the application's motherboard. The optimal use of the available spaces allows also for better thermal management, reducing the amount of heat to be dissipated.

Compared to rigid PCBs, flexible printed circuits can also prove more reliable and long-lasting, especially in applications where the circuits are subjected to continuous vibrations and mechanical stress. The standard interconnection techniques, based on soldered wires and hand-wired connectors, are replaced by flexible printed circuits, characterized by extremely low weight and thickness, which are accompanied by high mechanical resistance, resistance to high temperatures and atmospheric agents as well as good electromagnetic immunity (EMI). Think, for example, of the wiring of multiple electronic devices in the automotive sector, such as dashboard, display and man-machine interfaces (rotary controls, buttons, etc.). All these devices require a reliable connection in all operating conditions of the vehicle, being furthermore subjected to continuous mechanical stresses and vibrations. In the automotive sector, flexible printed circuits guarantee reliability, durability and maintenance interventions tending to zero. Figure 3 shows an automotive application of the FPC technology, here used in a car light switch.
In addition, the use of FPC can reduce the incidence of human errors during wiring, with consequent improvement in quality and reduction of costs. FPC technology contributes to significantly reduce both the size and weight of the application, a key factor for the creation of reliable, compact and highly integrated electronic devices.

Disadvantages of flexible PCBs
Although there are several and meaningful advantages, the FPC technology has also some drawbacks, or disadvantages. First of all, compared to traditional rigid PCBs, FPCs have a high one-time initial cost. Since flexible circuits are designed for very specific applications, the initial costs related to circuit and prototype design are higher than for rigid PCBs. If the cost is a determining factor in the choice of the type of PCB, it is better to use the FPC technology only for production volumes that are not too low.

Another disadvantage is the difficulty of repairing or modifying the PCB when it needs to be reworked. In this case, in fact, it is first necessary to remove the protective film that wraps the circuit, perform the intervention and then restore the protection. Flexible PCBs are a relatively new technology and not all manufacturers are equipped to provide this type of product to their customers. Furthermore, during the assembly phase, great care must be taken, as the circuit can be easily damaged if handled incorrectly, or by unauthorized personnel.

Flexible printed circuits are used in several applications that we encounter in everyday life, such as smartphones, tablets, cameras, printers and laptops. They can even be hosted inside our body, being a fundamental component for the creation of pacemakers, cochlear implants and defibrillators. Over the past few years, the FPC industry has grown considerably, driven by the spread of increasingly smaller and lighter wearable and electro-medical devices. In many applications, flexible PCBs can eliminate the need (and cost) of connectors and cables, improving connection reliability and reducing assembly time, assembly costs and overall device dimensions. In conclusion, we can affirm that flexible PCBs have allowed the implementation of new and interesting applications, not achievable with traditional rigid PCBs. However, during the preliminary analysis of every new design, it is necessary to carefully evaluate the advantages and disadvantages deriving from the use of a flexible PCB, compared to a rigid one; for many applications, the choice of a flexible PCB is mandatory, for others it depends on results of the costs and benefits analysis.
  • Multi-layer Flexible PCB Multi-layer Flexible PCB

    Multi-layer Flexble PCB uses single-sided FCCL and adhesive as the base materials, the similar technology of Double-sided FPC with the method of single side, double access; through several times of la…

  • Double Sided Flexible PCB Double Sided Flexible PCB

    After the double-sided PI board copper-clad board material is used in the double-sided circuit, a protective film is added on both sides to form a circuit board having a double-layer conductor. The St…

  • Single Sided Flexible PCB Single Sided Flexible PCB

    After the completion of the circuit, the single-sided PI-clad material is covered with a protective film to form a flexible fpc with only a single layer of conductor. Structure of Single-layer FPC The…

Exploring the Many Advantages of Flex Circuit Boards

  • Reduced Space and Weight: Most of the advantages associated with flexible PCBs come from their low volume and weight. In fact, using a flexible PCB instead of a rigid PCB can result in a space reduction of over 50 percent and a weight reduction of 95 percent, while simultaneously maintaining the function and reliability of the circuit.
  • Durability: The flexibility, reduced weight and reduced number of interconnects in PCBs allow them to handle changing external forces and improve their resistance to shock and vibration.
  • Signal Integrity: Flexible PCBs work in a wide range of environments, so signals will continue to perform smoothly despite exterior conditions. This improves the PCB’s signal reliability.
  • Higher Density: The thin layers and smaller parts mean that flexible PCBs are capable of supporting higher circuit densities.
  • Minimized Errors: Due to the elimination of mechanical connectors and reduced variations in assembly methods, flexible PCBs experience reduced wiring errors.
  • Low Cost: Because of the fewer assembly steps involved in the creation of flexible PCBs, they tend to be relatively low-cost.
  • Heat Dissipation: The thinner material of flexible PCBs allows for a greater surface-area-to-volume ratio, improving heat dissipation.

Flexible PCB Capability

Feature Capability
Quality Grade Standard IPC 2
Number of Layers 1 -10layers
Order Quantity 1pcs - 10000+pcs
Build Time 2days - 5weeks
Material DuPont PI, Domestic Shengyi PI
Board Size Min 6*6mm, Max240*610mm
Board Thickness 0.1mm -1.0mm
Copper Weight (Finished) 0.5oz - 2.0oz
Min Tracing/Spacing 3mil/3mil
Solder Mask Sides As per the file
Solder Mask Color Green, White, Blue, Black, Red, Yellow
Solder-stop coating---Soldermask oil Green, White, Blue, Black, Red, Yellow
Solder-stop coating---Coverlay PI and PET film
Silkscreen Sides As per the file
Silkscreen Color White, Black, Yellow
Surface Finish HASL - Hot air solder leveling Lead - free HASL - RoHS ENIG - RoHS Immersion Tin - RoHS OSP - RoHS
Min Annular Ring 4mil
Min Drilling Hole Diameter 8mil
Min. hole size---Drilling (PTH) 0.2mil
Min. hole size---Punching (NPTH) 0.5mil
Tolerance of dimension ±0.05mm
Other Techniques Peelable solder mask Gold fingers Stiffener (only for PI/FR4 substrate)

Main Equipments

Frequently Asked Questions (FAQ) About Our Flexible Boards Process and Capabilities
Here you will find many quick questions and answers about FPC PCBs,don’t hesitate to contact us,our email is [email protected]

How Many Flexible PCB Layers Do You Produce In Your Facotry?
We can produce from single layer flexible circuit,double layer,multilayer flex PCB unitl 10 layer FPC PCB.

What Are Flexible Circuits Used For?
Flexible circuits have evolved and help provide durability and reliability. Flexible circuits are also used in the aviation field. Other applications of flexible circuits are in hearing aids, calculators, cameras, printers, and in satellites.

What Is The Standard Delivery Time For Flexible Circuit Boards?
Typically,the leading time of prototyping flexible circuit board is one week,as for high volume of flex PCB,it will take around 2-3weeks.

What Is Flexible PCB Stiffener?
Stiffeners are a key design element in most flex designs and have a significant impact on both the performance and reliability of the finished flex circuits.There’re several types of stiffeners,such as FR4 stiffeners,polyimide stiffeners,aluminum and stainless steel.

What Materials Are Flexible Circuit Boards Made From?
The material is most of polyimide, copper, coverlay and stiffeners. These are all bonded together through either an epoxy or acrylic adhesive.

What Are The Best Flex Prepreg Materials?
No-flow prepreg is the preferred bonding material for joining flex and rigid materials. This is most commonly found in standard FR-4 or Polyimide.

Is It Best To Panelize A Flex Board, Or Leave That To The Vendor?
Leave it to the vendor. However, the engineer should supply array dimensions.

What Is A FPC Connector?
Flexible Printed Circuit (FPC) Connectors have been developed to meet the challenges of this expanding market, which demands smaller centerline or pitch spacing, lower profile heights, and lighter interconnect solutions. View video to explore FPC connectors’ capabilities.

What Is FPC Material?
FPC stands for Flexible Printed Circuit, also known as flexible circuit boards or soft boards. It is a highly reliable flexible printed circuit made by polyimide or polyester film.

Is There Any Minimum Order Quantity?
No,we can produce 1 to 10,000 pieces,what’s more,there is also no minimum order surcharge or additional fees
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