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Best Guide for Flexible PCB Manufacturing: (Flex pcb design Guide 2020)

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Flexible Printed Circuit Boards (Flex PCB or FPCBs) are all kinds of flexible loop systems that can contain single, double or multi-layer interconnect structures. Their designs can be fully flexible, or a combination of rigid and flexible parts.

The ever-growing demand for flexible circuits and, in particular, for hybrid rigid-flexible multilayer printed circuit boards is driven by the following factors:

  1. Flexible schematics allow you to create unique designs that address interconnection and wiring issues while providing system flexibility.
  2. With these circuits, PCB manufacturers can produce complex flexible stubs and other designs with consistently high yield rates.
  3. Flexible boards use the most advanced adhesive systems such as acrylics used in flexible composites.
  4. Flexible boards provide increased efficiency and reliability for end systems.

Compared to rigid wiring, PCBs made from materials based on polyimides, acrylates, polyesters and epoxies are more cost effective because they provide:

  • More freedom and opportunities for the designer;
  • Higher productivity in the production of boards and in the assembly of finished products;
  • Give a gain in weight and volume occupied by products;
  • Provide easy error-free assembly and installation of the final product.

Compared to Other Flexible Composites, Polyimide-Based Flexible Films can Provide:

  • Consistently higher bond strength;
  • Controlled and low fluidity of the adhesive;
  • Good chemical and solvent resistance;
  • Exceptional thermal stability, e.g. when soldering;
  • Good dimensional stability;
  • Large technological processing width;
  • Long shelf life without refrigerators;
  • Consistency of quality from batch to batch.

With these qualities in mind, PCB manufacturers of all flexible materials prefer polyimide materials to increase the productivity and efficiency of their plants.

When working with polyimide materials, experts note such advantages as:

  • The possibility of multiple pressing and multiple soldering without delamination and swelling of the boards;
  • Simplicity and ease of removal, replacement of components, reliability when re-soldering;
  • Exceptional electrical properties;
  • Outstanding flexibility and adhesion for critical bending conditions;
  • The ability to design multi-layer boards with a very high wiring density;
  • Increased reliability of systems installed in the workplace.

It is for these reasons that polyimide materials are indicated in the specification for the most complex schemes with the highest reliability requirements.

The physical properties of polymer films used in flexible circuits differ significantly from the properties of materials used in rigid boards based on fiberglass with epoxy or polyimide systems. This encourages rigid board manufacturers to embrace new technologies specific to the production of flexible and flexible systems.

Here we will present that what flex PCBs are and about the Flex PCB manufacturing process. Moreover, advantages of flexible PCB manufacturing. Since it is very important for manufacturers to understand all the manufacturing procedure of flexible PCBs. So that they can fabricate flex PCBs by

  • Cost saving
  • Increasing the functionality and durability.

What are Flex PCBs?

Flex PCBs actually contain a very thin insulating polymer film that has conductive circuit patterns affixed thereto. Moreover, it has supplied with a thin coating of polymer in order to protect the conductor circuits. Electronic engineers are using flex PCBs in interconnecting electronic devices.

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Basically, this advanced technology had first used by the manufacturers in 1950. Today it has become most popular interconnection technology for modern electronic gadgets. These PCBs are also popular by the name of Flex PCBs or Flexible PCBs. Flex PCB manufacturers have assigned this name because they have capability to fit in the complicated devices easily.

Flex PCBs have very exceptional and extraordinary advantages. As they have tiny volume and good quality. Furthermore, they are,

  • Light weight
  • Has agile structure.

Hence, they have ability to satisfy all the needs and demands of modern-day’s electronic devices. Flex PCB boards also have capability to expand to three-dimensional space. And hence they can easily improve the freedom of mechanical structure design and circuit design.

Moreover, all of these benefits can reduce all the burden of the assembly errors and machine. In fact, flex PCBs also helpful to extremely improve high stability and reliability of all the electronic gadgets.

Electronic engineers create flexible PCBs in order to resist the highest temperatures. The range of these extreme temperatures is between -200° C and 400° C. So, they are most wanted in gas and oil industries.

How Many Kinds of Flex PCB Boards?

Basically, you can get flex PCBs after Flex PCB manufacturing process. Actually, there are two manufacturing ways to design these flex PCB boards. Such as,

  1. Classification of flexible PCBs based on Layers
  2. Classification of flexible PCBs based on the configurations

On the basis of layers, the types of flexible PCB boards are:

  • Single-Sided Flex PCB Boards
  • Single-Sided Flex PCBs with Dual Access
  • Double-Sided Flex PCBs
  • Multi-Layered Flex PCB boards

Furthermore, the classification of flexible PCBs based on the basis of configurations:

What are the Benefits of Flex PCB Manufacturing?

It is a real fact that in the future uses of flex PCBs is significantly increasing day by day. In fact, you will notice that flex PCB manufacturers are using flexible PCBs in almost all electronic devices. Moreover, the flexible PCBs have many advantages. Flex PCB designs actually offer many advantages to their manufacturers as they are backbone of small and unobtrusive electronic gadgets.

Flexible PCB boards are lightweight and has smaller package size. Furthermore, they are ideal for those electrical devices where you have no choice for any other solution. These PCBs are very thin and hence you can easily

  • Folded
  • Creased
  • Positioned in any area where other parts are not supporting to fit.      

Here we are providing some benefits of Flex PCB manufacturing for your attention.

Greater Capability

Flexible PCB boards have ability to perform greatly even in the environment of extreme temperatures.

They can also make use of extra kinds of connectors and more components. Additionally, they also provide superior resistance to all the radiation issues.

Greater trustworthiness

In fact, in flex PCBs, there is less need of connectors and interconnectors, so it adds less potential failure points. In this way there is less need of replacement or maintenance. Furthermore, you can also get benefit of flexible PCBs because of their lower copper weights and quite smaller drill holes.

Smaller in size

Great bendability offers a great ability to shorten the area of board and also provide wide range of mounting possibilities.

Perfect Designs:

Manufacturers often perform Flex PCB manufacturing by making use of automated machinery. So, there is less chances of errors which had involved in handmade harnesses and wires. Moreover, all these perfect designs make flex PCBs an essential use and also make sure of great accuracy.

Long-term Performance and Durability

Flex PCB manufacturers have actually designed the flex PCBs in order to increase the lifespan of electronic devices. They can actually flex electronic devices maximum up to 500 million times and hence have capability to increase their lifespan. Moreover, they are best for vibrations and shocks and so improve the performance of such devices.  

High Heat Dissipation:

Because of the denser device populations and compact designs, designers create shorter thermal paths. Hence, it helps to dissolve all the heat in comparison to rigid board. Moreover, these flex printed circuit boards also help to vanish the heat from both of the sides of the board.

Best for High Temperature Devices:

Since designers use polyimide in flex PCB designs so that it can easily withstand high temperatures.

Furthermore, it also provides extreme resistance against all materials like,

  • Oils
  • Gases
  • Acids, etc.

Flex PCBs are perfect even in temperatures up to 400 degree. And they are also best in harsh working environments.

Cost efficient:

Flex PCB manufacturing is very helpful in reducing all and all assembly costs. Because very thin and flexible films of polyimide have capability to fit in a smaller area with extreme ease. Flexible PCB boards also can help to reduce,

  • Wire routing errors
  • Testing time
  • Reworking time

What Factors are to Consider Before Flex PCB Manufacturing?

As we have already explained that using of flexible boards can provide great reliability and a vast variety of interconnections. Furthermore, flexible PCBs are:

  • Durable
  • Lighter in weight
  • And can provide compressed construction.

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There are several different kinds of manufacturing offers and materials available for flexible circuit boards. Because this modern and latest rising technology has an extremely bright and golden future. But we are here to describe some very important things to you. You will obviously need to think about them or consider before manufacturing flex PCBs.

  1. Reduction of Weight:

In fact, you can reduce the weight of several different electronic packages by making use of flexible circuits. In comparison to unfilled polymers, they are higher in solidity. So, you have to select a suitable material with great care for weight reduction.

  1. Cost of Purchasing

Basically, flex PCB boards are costly. Moreover, if you compare them with their durability then price does not matter. But people think that they are very costly. However, if you select reliable flex PCB manufacturers then they will provide you,

  • Durable
  • Strong
  • Long-lasting
  • Reasonable prices of flex boards.

But if you get best quality flex boards by spending a little extra cost then it is not a big deal.

  1. Decreased Assembly Time:

Printed boards which are very flexible they have least chance to breakage during manufacturing. Actually, flex boards are not delicate and sensitive. Hence, there is the less risk of breakage or damage of flex PCBs. So, they take less assembly time.

  1. Active and Dynamic Flexing

Indeed, it is a very important factor to purchase polyimide with very thin copper foil. Because it is a best choice for several different devices of dynamic flexing. Moreover, you can easily make use of a thicker flex for a stay and bend application.  

       5. Materials Using in Flex PCB Manufacturing

There are many other materials that are available for flex PCB manufacturing. But Polyimide is the actually very popular and common material for flexible circuit boards. Here are some other materials available for manufacturing flexible PCBs. Such as,

  • LCP
  • PET
  • PEN

Furthermore, polyimide will be your top priority. As polyimide has several advantages. Such as,

  • Polyimide is Ideally flexible at all temperatures
  • It has perfect electrical priorities
  • It contains amazing ability of resistance against chemicals and tear
  • Polyimide also has the greatest tensile strength

Although polyimide has several benefits but it also has some drawbacks. We are giving you some of its disadvantages. Like,

  • The performance of temperature becomes really worse, if Flex PCB manufacturers make use of it with an adhesive system
  • polyimide is fairly expensive in comparison to PEN
  • It has ability to absorb maximum moisture up to 3%.
  1. Several Design Possibilities

Flexible PCBs actually provides lots of choices in designs. So, manufacturers can adapt flex PCB designs according to their requirements and needs.

General Guidelines for Designing Flexible Boards

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Initial Data for Design

What tasks should you set for yourself before starting the design?

  1. The density of the mounting field. The size of the contact pads for mounting and the gaps between them largely determines the content of the project: the resolution of the picture, the configuration of the interconnections, the dimensions of the boards.
  2. Dimensions of the group blank of the printed circuit board and assembly and assembly blank installed on the conveyor of the assembly and assembly line. Methods for separating boards from a workpiece.
  3. Alignment system (locating system) with workpiece fiducial marks and sights for installing multi-pin components on the working area of the board.
  4. Finishing coatings for soldering.
  5. Permissible warpage of the rigid part of rigid-flex printed circuit boards. Often, boards are rejected due to unacceptable warping, preventing them from assuming the flat state required by the printer and component installer.
  6. Conditions for subsequent installation. Heat resistance of printed circuit boards determines the acceptability of soldering temperature conditions. This problem is especially acute when using lead-free soldering technologies. To ensure these conditions for the manufacture of printed circuit boards, materials with a high glass transition temperature must be used. These materials are more expensive than conventional materials, but you have to put up with it in order to get a product of acceptable quality and reliability.
  7. Execution of a release liner and a solder mask. Solder mask configuration: accurate alignment with the mounting field, the presence of a mask in the gaps between the mounting elements, the absence of mask “creeping” onto the contact pads on the hard part, or vice versa – pinching of the contact pad with a cover film on the flexible board – all this affects the quality of soldering. The heat resistance and moisture resistance of the solder mask and the cover film is subsequently reflected in the characteristics of the resistance of the printed circuit assembly to external factors.
  8. That it should be readable is no doubt. But it is often used to center components. The positioning accuracy of the fiducial marks is then added to the quality of the marking.
  9. The board must be testable, that is, it must have additional points for contacting probes (probes) for in-circuit control and quality diagnostics. Typically, these additional elements reduce the density of the layout by 10-15%. But this has to be reckoned with in order to ensure an acceptable level of quality and reliability of the electronic module through testing.
  10. Finally, the configuration of the mounting elements on the board must be tailored for bulk soldering methods. Otherwise, the printed circuit assembly will have numerous solder and non-solder bridges, for the detection and correction of which it is necessary to go on additional labor costs and an increase in the production cost.
  11. Separately, for mounting BGA components, it is necessary to observe the soldering conditions without solder leakage into the metallized holes (Fig. 1) or to fill the holes with metal (copper using a special technology).
  12. Plating through holes on curved surfaces should be avoided.
  13. You cannot route conductors at 90 ° to the direction of the bend.
  14. It is not recommended to route conductors on single layers around bends.
  15. The bending arc should be made as large as possible: to increase the life of dynamic flexible printed circuit boards.
  16. It is necessary to design a GPU with copper layers in the neutral part of the PCB fold.

Conclusion:

We have described some of the most important factors that a manufacturer should consider while flex pcb manufacturing. Although, Flexible circuit boards are extremely beneficial and useful for complex devices.

But it is also a real fact that they are not applicable for all applications. Because there are several applications which use only rigid circuit board. Moreover, they are also costly but rigid boards are affordable for all products.

Flexible circuit boards are expensive but we cannot refuse their importance for modern gadgets. Because they are light weight and has ideal structure for low profile gadgets. They are also best for extreme temperatures.

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