PCB Manufacturing

How to Choose the Right Material for Your Flexible LED PCBs

Flexible LED PCBs

What are Flexible LED PCBs?

Printed circuit boards, or PCBs, offer seamless device functioning by connecting electronic components, and the field of flexible printed circuit technology is always developing. These circuit boards find use in consumer electronics, automotive industry, and aerospace industries, among other major electronics sectors. With the introduction of flexible LED PCB, the conventional techniques for joining different parts of an electronic gadget or circuitry have undergone a radical change and due to the adaptability of the connector, and its small size, flexible PCBs allow for a substantial decrease in size, and expenditures when compared to rigid PCBs.

  • Flexible LED PCBs flexibility allows them to be bent and flexed, giving application designers and operators more creative freedom because standard rigid circuits cannot accommodate the ability of flexible circuits to adapt to tiny or irregularly shaped places.
  • Flexible LED PCBs also have the benefit of taking up less space, which lightens the load on the motherboard of the application, and the use of the available space also enables improved thermal management, which lowers the quantity of heat that needs to be released.
  • In cases where the electronic components are exposed to continuous oscillations and mechanical strain, flex LED PCBs may prove to be more secure and robust than stiff PCBs, and as a result, the traditional connectivity methods that rely on solder wiring are replaced with flexible printed circuits.

Electrical equipment used in various industries is susceptible to constant mechanical strains and vibrations, and they all need a dependable connection to function and that is when flexible LED PCBs ensure dependability, longevity, and low maintenance.

Importance of Flexible PCBs in LED Strips

LED strips are getting more and more popular as technology advances and flexible PCBs just make LED strips better. LED strips consist of interconnected circuit boards and surface-mounted components such as SMD LEDs are used to create flexible printed circuit boards using Surface Mount Technology. The FPCB serves as a foundation for the LED chips when they are assembled because the ability of a circuit board to dissipate heat is just as crucial as its design. LED strip lights greatly benefit from flexible electronics and different FPCBs are single-layer, double-layer, and multi-layer PCB circuits that can be used to build LED strips.

What are the Materials of a PCB?

Printed circuit board materials are the basic elements of PCBs since they provide the foundation and shielding required for the multiple layers and to create electrical connections among the copper-containing layers that make up some of the electronic elements. A flexible LED PCB uses the same components as any other PCB and the materials work in the same way.

1. Substrate Layer

The printed circuit board is constructed on top of the substrate layer and fiberglass is frequently used to make it because fiberglass is a very hard material that provides PCB rigidity. Nevertheless, other substances may also be employed as backing materials and examples of these include FR-1, polyimide, insulated metal substrates, epoxies, and G-11. Materials are particularly designed to satisfy requirements such as the dielectric constant and glass transition temperature and the most common material used for substrates is FR-4.

2. Conductive Layer

The copper layer is the conductive layer that forms signal traces and the circuit can conduct electricity thanks to these signal wires. Other common materials for the conducting layer that can be utilized effectively are gold and silver, however, nearly all of the conductive layers on PCB designs are composed of copper because copper is an electrical conductor with high efficiency.

3. Solder Mask Layer

The solder mask has a small coating of polymer and is positioned with copper siding on top of the laminate. Furthermore, the solder mask is what gives the LED flexible PCB its green color and this layer aids in the prevention of solder bridge creation by helping PCB manufacturers solder the correct locations on the board.

4. Silkscreen Layer

Epoxy is often used for silk screening on the board and it also acts as a reference designator to help with component placement on the circuit board. It helps in identifying different warning indicators and the use of a silkscreen helps locate test areas and manufacturer markings.

How to Pick the Right Material for Flexible LED PCBs

LED Flexible PCBs

As a result of their expanding dominant position in the market and quick technical improvements, the flexible LED PCB is becoming increasingly prevalent. This is because LED flexible PCBs may be used for an extensive variety of purposes because of their thinness, pliability, and lightweight characteristics. This has been rendered achievable by the creation of innovative, LED flexible PCB manufacturing techniques. Since the efficiency of the substrate material influences the fundamental characteristics of the PCB, improving the operation of the substrate substance is crucial to increasing the technical capabilities of the PCB.

Let us discuss the various types of materials used in flexible LED PCBs and see which properties can be most beneficial during the production of the flexible LED PCB.

1. Film Substrate Material

The capacity of film substrate material to serve as an insulating medium and conductor carrier between circuits makes it a useful material and it must also be flexible enough to bend and curl.

  • The choice of substrate components should be based on its effectiveness and affordability, however, for flexible copper-covered laminated material, PI, a heat-set resin that becomes inflexible at elevated temperatures, is frequently the recommended substrate medium. Since PI has excellent electrostatic qualities and significant resistance to heating, it can continue to maintain its flexibility and plasticity throughout thermal polymerization, unlike many other thermoplastic resins.

In addition to having a higher degree of stability, improved PI material has rip resistance and substantial moisture retention qualities.

  • Halogen-free environmental requirements are required for both flexible and rigid CCL, which is an unavoidable and strict trend in the electronics sector and six categories of dangerous compounds have been prohibited from being used in electronic equipment including the flexible PCBs.
  • The adhesive is used to attach copper foil and substrate material films and it may be broadly classified into four types- acrylic, PET, modified epoxy, and PI resins. Of these four products, modified epoxy and acrylic resins are more commonly utilized due to their strong adhesive properties.

There are more than a thousand categories of materials that may be used in a PCB, some of which must be appropriate for the production of flexible LED PCBs, and that is the reason new flexible LED PCB substrate materials will be used as the uses for flexible LED PCBs grow.

2. Two-layer PI Substrate Material

When two-layer flexible CCL is used in a flexible LED PCB, they are more suitable for environmental preservation and may fulfill the requirements of lead-free soldering by raising the temperature as it doesn’t include glue that might contain halogen. There are three different ways to manufacture 2L-FCCL- Film coating, lamination, and electroplating. After comparing the three approaches, it is obvious that copper foil and thinner substrate material can be obtained at a reasonable cost and that electroplating metal layers on polyimide films is a simple process to roll out. Film coating is useful for inexpensive, large-scale manufacturing because when creating double-sided boards, lamination performs very well.

 3. New-Type Copper Foil

Copper or copper foil is the primary conducting material used in flexible LED PCBs but alloys such as aluminum, nickel, gold, and silver are also occasionally utilized. Copper foil is divided into two categories- rolled and annealed (RA) and electro-deposit (ED) copper foil, based on the various production processes used, and the two varieties of copper foil differ from one another in their crystal forms. The column array geometry of RA copper foil results in a smooth, even structure that is amenable to etching and roughening processes, and fish scale is a property of ED copper foil that results in smooth, durable copper foil that cannot be roughened or etched. When it comes to the dynamically flexible LED PCB that requires a high degree of elasticity, RA copper foil is typically used. Currently, ED copper foil is the primary component of high-density flexible PCB and new requirements are set to be compatible with the mass-volume fabrication of PCBs whose pitches fall below 50 μm.

4. LCP Substrate Material

LED Flex PCBs

Liquid crystal polymer (LCP) is a recently created material that fundamentally modifies the disadvantage of polyimide substrate material and single or double-sided CCL is produced by covering a thermoplastic LCP sheet with copper foil and continuously pressing it with heat. With a water absorption rate of just 0.04% and a low dielectric constant, this kind of CCL can withstand the demands of high-frequency digital circuits. The advantages of TLCP include its ability to be molded and manufactured by pressing into thin films, which may be used as flexible LED PCB substrate material. Furthermore, it may be recycled and utilized again after undergoing secondary processing and that is why flexible LED PCBs are starting to use TLCP. This material also provides other benefits due to its low absorption of humidity, high-frequency compatibility, and thermal dimensional stability and has become a sought-after material for PCB construction.

5. Halogen-Free Material

The WEEE and RoHS outlawed the use of six different categories of hazardous materials and the processing of waste electronic and electrical equipment and as a result lead in surface coating and bromine used as a flame retardant in PCBs are currently banned by these regulations. With advancements, it is now possible to use halogen-free substrate in flexible and rigid printed circuit boards because various flexible substrate materials, including reinforcement boards, prepreg, and solder masks, are halogen-free and fire-resistant.

6. Photosensitive PI Coverlay

PIC was developed since standard PI coverlay was unable to fulfill flexible PCB criteria, such as superior density and environmental safeguards and PIC has a high degree of flexibility tolerance as well. Because of their great binding force, flexibility, and high resolution, liquid PIC has gone through extensive study and has multiple applications, however, the limited amount of dimensional stability is a drawback of PI.

7. Conductive Silver Paste

A printed conducting coating has the characteristics of an excellent connection, minimal resistance, and adaptability. Conductivity ink, which primarily consists of silver particle paste, can be printed on insulation material that includes wiring or shielding material generated during the manufacturing of these circuit boards. This silver paste can make images for RFID objects and satisfies the demands for minimal resistance and adaptability. The Flexible LED PCB that has conductive silver paste applied is approved in terms of humidity testing, high-temperature storage, and high- and low-temperature cycle performance and the component has proven to be of great value.

Flex LED PCBs

Factors You Should Consider When Choosing a PCB Material

To guarantee the best possible performance, and dependability of an electronic device, the proper PCB material selection for a given application is essential and when selecting a PCB material, there are a number of things to take into account, all of which have an impact on the finished product’s overall performance.

1. Electrical Performance

Dielectric constant and loss tangent are important electrical characteristics to take into account for the electric performance of a flexible LED PCB because the loss tangent shows the material’s energy dissipation component, whereas the dielectric constant measures the material’s capacity to store electrical energy. Signal integrity and the general operation of high-speed and high-frequency circuits are all impacted by these two characteristics and selecting a PCB material with a low dielectric value and low loss tangent is crucial for applications that need high-frequency operation or fast data transfer.

2. Chemical Resistance

During the processes of production, and assembly, PCB materials may come into contact with a variety of substances, including fluxes, cleaning solvents and corrosive conditions, and these exposures can only be tolerated by a material that has strong chemical resistance without deteriorating or losing its thermal, or electrical capabilities. Take into account the particular chemicals that a flexible LED PCB could come into contact with throughout its lifespan.

3. Thermal Performance

The most important parameters for assessing an electric device’s thermal performance are its thermal conductivity and glass transition temperature and high thermal conductivity PCB material may efficiently disperse heat produced by electronic components, lowering the risk of thermal failures and increasing the useful life of the device. Since they can withstand extreme temperatures without sacrificing their mechanical strength, substances having a greater transition temperature are suitable for operations that generate a lot of heat or function in extreme environments.

4. Cost

The material’s basic performance is vital, but it’s also critical to balance those needs with financial limitations as it is essential to take into account all expenses associated with the electronic device’s lifespan. These factors include those related to assembly, manufacture and maintenance when evaluating the availability and cost of PCB components. Affordable and readily available materials can assist in ensuring that the work is completed without a hitch, and lower the likelihood of setbacks or excessive expenditure while maintaining the cost of the finished product

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