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The Future of Flexible Circuits

The Future of Flexible Circuits

As predicted by RUSH PCB UK Ltd, the market for flexible circuits is going to continue to expand steadily in the future, just as it has been doing for the past three decades. The reasons for this are not hard to find, as, on one hand, flexible circuits continue to support the existing technology so important to different industries, while on the other, advanced flexible circuits are able to comfortably meet the futuristic demands being made by up-coming industries, including the military, avionics, aerospace, telecommunication, consumer electronics, medical, and automotive. To interpret the future of flexible circuits appropriately, it is necessary to consider the subject from three angles:

  • Newer configurations of flexible circuits [1]
  • Newer applications where flexible circuits are useful [2]
  • Newer technology being used for manufacturing flexible circuits [3]

Newer Configurations of Flexible Circuits

Depending on the market demand, manufacturers are always willing to add higher flex layer counts along with prevalent blind and buried via structures, embedded components, integrated connectors, sculptured flex, and more.

Again, based on application, manufacturers can offer flex designs requiring shielding for EMI/EMC in specific areas, asymmetrical constructions, and varying thicknesses between different rigid areas.

Apart from the regular rigid-flex PCB methods of constructions, there have been recent advances in newer configurations of flexible circuits available from different manufacturers. The standard rigid-flex PCB is rather a symmetrical construction, acts as a baseline for building upon, and offers good control over impedance.

Fabrication of standard rigid-flex PCB usually has flex layers at the center of the construction and even layer counts in both, the flex and the rigid areas. Although four to sixteen layers are common in designs, there can be more. Placing the flex layers at the center offers the maximum level of flexibility. However, manufacturers such as RUSH PCB UK Ltd also offer variations in configurations such as:

  • Odd Layer Counts
  • Asymmetrical Construction
  • Varying Layer Count
  • Integrated ZIF Tail
  • Via-in-Pad Design
  • Air-Gap Construction
  • Multiple Rigid Area Thickness
  • Shielded Layers

Although most designs prefer an even layer construction, manufacturers do offer odd layer counts, and this has its own advantages. For instance, a rigid-flex PCB may have seven layers in its rigid portion, and three flexible circuit layers. Requirements of stripline impedance control mainly drive designs of this nature, where the flex area requires two-sided shielding. The construction in the flex area usually has ground layers on the two outer layers sandwiching a signal layer between them—offering large numbers of interconnects between the rigid sections.

The major factor in the odd layer count design is both rigid and flex areas may have odd layers, and the layers counts in the rigid and flex areas may be mutually independent. Manufacturers offer other variations too—even layer count on one side of the core, and odd layer count on the other. The advantage being higher flexibility and higher reliability of bending both in short-term and long-term. Leaving out unwanted layers also reduces the cost of the design.

Complex design requirements such as blind via construction and or widely different dielectric thicknesses within the same PCB calls for an asymmetrical construction. Manufacturers prefer to shift the flex layers towards the bottom of the stack rather than place them in the middle. Although this does raise some concerns of warp and twist during manufacturing, using hold-down fixtures handles them easily.

Manufacturers offer another variety of construction with varying flex layer counts between rigid sections. For instance, the first and second rigid sections may have four to six layers of flex between them, but have only one or two flex layers between rigid sections two and three. Leaving out unnecessary flex layers helps to improve the bend capabilities significantly for the portion with lower number of layers.

By integrating a ZIF tail into the rigid end of a rigid-flex design, the manufacturer eliminates the necessity of mounting a ZIF connector. This is a boon in high-density designs, as it saves both real estate and cost, while producing a thin design.

High-density designs often require blind and buried vias, whereas close-pitch BGA may require via-in-pad design along with via fill and capping. Although dimensional tolerances of materials and manufacturing methods limit the number of lamination cycles in multi-layer rigid-flex PCBs, manufacturing them with via-in-pad design is possible by placing them within the rigid parts of the board.

Manufacturers also offer flex layers in separately configured independent pairs with an air gap in between. This has the advantage of improving the flexibility of the flex part substantially. Of course, this design is only applicable where there are more than two layers of flex. The absence of adhesives within the rigid areas offers greater reliability of the vias therein, resulting in long-term operation of the board.

Although an expensive and complex stackup design, construction of flex circuits with different thicknesses in multiple rigid areas is possible, but presently limited to two rigid areas with different thicknesses.

Special flex circuits requiring shielded layers for reducing the effects of EMI and RF interference use specialized films rather than copper layers. Using copper layers as shield is an expensive proposition. Instead, the special films act as effective shielding material while keeping the thickness of the flex down, thereby improving the flexibility.

Also Read: Understanding the Basic Aspects of Electronic Components

Newer Applications Where Flexible Circuits Are Useful

One of the latest applications that flexible circuits have independently triggered as an explosion is the wearable electronics market. Wearing electronics on the body essentially calls for comfort, and flexible circuits guarantee this. Some examples of wearable electronic applications prevalent on the market are wrist-worn activity and body function monitors, foot-worn sensors, wearable baby monitors, medical sensors, pet monitors, and electronics on worn clothing. By bending and forming flexible circuits to suit the curve of the human body, the applications provide comfort for long wear and use.

Newer Technology Being Used for Manufacturing Flexible Circuits

Manufacturing flexible PCBs still follows the traditional methods of photo-lithography and etching to get rid of the excess copper. To make even thinner flex circuits, researchers at the McCormick School of Engineering at the Northwestern University are dispensing with the copper layer altogether. Rather, they are using a graphene-based ink sprayed onto the substrate in the required pattern to provide the electrical connections.

The advantages of using graphene are twofold. One, graphene can exist as only one atom thick, and its two-dimensional characteristics makes it both flexible as well as transparent. However, the researchers are spraying it on as 14-nanometer thick layers for creating the tracks and patterns. The second advantage is graphene being 250 times more conductive than copper is, only very thin layers are necessary. This improves the flexibility significantly, reduces the weight, and allows for even thinner flex circuits. The next attempt is to allow doping of graphene so that apart from its use as a conductor, it can be used as a semiconductor to make embedded transistors.

Conclusion

The combination of configuration, technology, and application is making rigid-flex circuits a formidable force in the electronics field. It has already overtaken the applications of traditional rigid printed circuit boards, and is threatening the more sophisticated uses of special PCBs in military, aerospace, medical, and consumer electronics industry.

For further information, refer to RUSH PCB UK Ltd.

References:

  1. https://www.epectec.com/articles/how-rigid-flex-pcb-design-configurations-are-advancing.html
  2. http://circuitcellar.com/cc-blog/the-future-of-flexible-circuitry-2/
  3. https://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/graphenebased-ink-promises-future-flexible-electronics-
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Choosing the Right Flexible Circuit Supplier – Five Critical Considerations

Choosing the Right Flexible Circuit Supplier – Five Critical Considerations

If you are currently shopping for a flexible circuit supplier to build your circuit board, but are not too experienced in this arena, please take the time the time to read the following information.  The choice you are about to make is too important.  One of the biggest mistakes people often make is going with the lowest bidder, although easy on the wallet, you may be exposing yourself to a whole lot of aggravation and frustration.  When you are interviewing perspective flexible circuit supplier it is important to keep the following points in mind;

  • Capabilities (applications, designs, volume, engineering, and fabrication)
  • Assembly
  • Certifications
  • Quality Systems

Capabilities

Can they meet your needs?  Do they have the right equipment and the required knowledge?  After you have explained what your needs are can they tell you how they will meet the mechanical needs, which chemicals they will use, what type of thermals will be used, how the electrical aspects will work, how big it will be, and how the surface will be finished?  If not, then you should probably move on to the next applicant.

Will they be able to meet your supply needs while building it the exact way you need them to?

Do they have the capability to meet your fabrication requirements on a routine basis?  The fabrication process is quite detailed, will they be able to meet every detail you need every time you need it?

Assembly

Can the perspective supplier provide the necessary components?  If so this can save time by eliminating the process of shipping it to another facility to have them added.  But, you should ask them if they have the appropriate equipment, know how?  If they are not capable of performing the component assembly, it just may be worth the extra time to send it to someone who knows what to do and how to do it correctly the first time around.

Certifications

Find out what type of certifications they currently have.  Certifications are an important aspect because they show the suppliers dedication, experience, as well as knowledge of the industry.  This may be a deal breaker for you.  Why should you trust a supplier that does not hold any certifications in their expertise?

Quality Systems

When a supplier has taken the time to demonstrate their expertise through certification they are also providing proof of their standards.  This is because they will routinely go through an auditing process to keep their certification current.  The certifying agency performs the audit, ensuring that the required standards and quality systems are in place and more importantly being used.

Although you may not be an expert in the Circuit Board Industry, it does not mean you can’t arm yourself with the important questions that should be easily answered by the prospective supplier.  You have worked too long and hard to just hand your project over to a supplier who can’t meet your needs.  Perform due diligence now, avoid problems later.

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Flexible Circuits, They Bend for All of Your Electronic Devices

Flexible Circuits, They Bend for All of Your Electronic Devices

For those of you who may not be familiar with the term flexible printed circuit boards you have visited the right place!  They are simply printed circuit boards (the electrical brain of computers) that have the ability to bend or flex making them wearable.  Once you understand this the name makes perfect sense and is self-explanatory.  Generally, they are uses in type of electronic device that needs to be flexible during its use.  They are separated into three separate classes each with specified uses that make them unique.

Class I (One)

Class I flexible circuits are a part of every type of device that you can conjure up.  They do not need a whole of attention while wearing them because they are not exposed to rough environmental factors that usually results in the malfunction of the device.  Some examples of flexible PCB devices would be halter monitors (measures your heart rate), calorie counters, and devices that measure the number of steps you take during the time you are wearing the device.  The standard that must be met for this class is based on reliability and quality.

Class II (Two)

Class II flexible printed circuit boards are utilized for industrial and commercial industries.  They also are not usually exposed to tough environmental factors because of this their standards are based on quality and efficient solder joints making connections within the circuitry.  An example of where you will find a flexible PCB would be in a home automation system.  Most home systems allow you to communication with certain appliance through the internet.

Class III (Three)

Class III flexible printed circuit boards are used for military, aerospace, and medical electronics.  Since these boards are used for such important tasks their standard requirements must meet an extremely demanding testing process before they are deemed ready to function.  The assembly process is also more involved when creating them;

  • Knowing when and how to connect the vias in the bend areas
  • Avoid connecting vias when possible
  • Assuring stiffeners stay in the right places
  • Bending and twisting at different ratios, angles and levels
  • Different electrical components that are associated with it
  • Different thermal traits
  • Application of the J Standard to all military devices
  • Environmental testing
  • Thermal Shock cycling
  • Temperature cycling

Flexible PCB’s are the very heart of computerized machinery, without them we would not be able to enjoy our cell phones, games, computers, the list can go on and on!  We have come to depend on our devices, understanding the types of circuit boards your electronic gadgets have will help you appreciate those wonderful fabricators or manufacturers who share their expertise with the world so we can benefit from everything technology has to offer.  Whether you are using class one, two, or three, or any combination of the three you have experienced what todays flexible printed circuit boards have to offer us.  We excitedly continue to look forward to see what today’s technology will bring us next.

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Significance Of Flexible Circuits

Significance Of Flexible Circuits

In the electronics world, necessity is the main motivation to inventions and can be attributed to the invention, development and evolution of flexible circuits in both electrical and electronic circuits. A flexible circuit also called a flex circuit is an arrangement of printed wiring utilizing flexible base materials with or without a flexible cover layer. Flexible circuits are used in significant life processes in the heart pacemakers, digital cameras, disk drives and car stereos. Such devices require great flexibility in their design and installation. Moreover, flex circuits can be of any size thus many devices can be manufactured to suit customer specifications.

On the other hand, miniaturization is a common word in circuit designing world. In this context, there is need to develop smaller size circuits with zero compromise on their performance. This led to the need for a functional and reliable circuit alongside its flexibility. Luckily, flexible circuits were invented and they serve as a solution to several orientation and spatial constraints which were faced by fixed PCBs (Printed Circuit Boards). Please join us (RushPCB) as we take you through the merits of flex circuits in the modern world where technological advancement is the order of the day.

Merits from the way flex circuits are made

A flexible circuit is made of a film of flexible polymer which is usually laminated onto a sheet of copper which is engraved to yield a given circuit pattern. The polymer is vital since the circuits can be designed or etched on either side of the film. Sequentially, another overcoat of polymer is used to insulate the circuit and protect it from harsh environmental conditions.

The polymer film which is used in the design of flex circuits is KAPTON. This polymer has many favorable characteristics like dimensional stability, heat resistance and flexural capability. Different from that, KAPTON has excellent thermal stability thus it provides a better base for the mounting of hard boards.

In the same token, flex circuits are naturally flat thus they offer considerable space and weight savings compared to the traditional wire harnesses. Their thickness is usually as low as 0.2mm and a weight reduction of 75% is achievable using these circuits.  Are you satisfied with the explanation? Please pay us a visit at https://www.rushpcb.co.uk/blog/

Merits from the Uses of flexible circuits

It is possible to design several double or single-sided flexible circuits with shielding, complex interconnections and surface mounted devices all in multi-layer designs. Alternatively, the multi-layer can be combined with rigid Printed Circuit Boards leading to the creation of a rigid and high flexible circuit which is capable of supporting all the devices needed in the design in question.

A special feature of flexible circuits is that they give a designer a third dimension to work with. This is because just as their name indicates, these circuits are highly flexible since one can bend them and shape circuits along 2 or more planes during the process of installation. It is because of this feature that flexible circuits are used in tight-fitting and complex assemblies where it is impossible to accommodate several rigid harnesses and boards.

Flexible circuits provide an excellent way of reducing the time taken to assemble a product due to its exclusive properties of flexibility and a flawless integrate form. As if that is not enough, the number of assembly operations and testing time reduces significantly.

Merits based on Types of Flexible Circuits

Flexible circuits are of four types depending on the degree of complexity which is used in various combinations to solve each interconnection in the design problems. The four types of flex circuits basing argument on their merits which makes flex circuits preferable shall be discussed in this part.

1). Single-sided flex circuits

Single-sided flexible circuits are the simplest flex circuits of the 4 types as already mentioned. This is because they provide optimal flexibility for dynamic applications. In the same token, these circuits are more adaptable to the Surface Mount Technology (SMT), Tape Automated Bonding (TAB) and many other significant developments in the circuit technology. They derive their name from the fact that they allow access from a single side only. These circuits are used in the optical pick-up for computers, camcorder, camera, vibration motors for a mobile phone and VCD players. Moreover, they are cheap and they are usually produced in great volumes.

Single layer flex circuits are created using the double access or back barring technique which allows access to the metal conductors from the two sides of a circuit. This method is vital since it eliminates the need for plate-through holes needed in multi-layer circuits.

2). Double-sided flex circuits

These are flexible circuits with two conductive layers and which can be accessed from both sides of the board. Their main feature is the component assembly on both sides. However, their flexibility capacity reduces due to their complexity and thickness. Different from that, their ability of interconnecting between sides using plate-through holes is crucial for the implementation of complex designs with the flexibility of the circuits being maintained to the latter. These circuits are mainly used when it is difficult to route the layout and circuit density on a single layer. Comparatively, they are used in the mount assembly of dense surfaces and shielding applications.

3). Multi-layer flexible circuits

These circuits are used in complex and high dense design specifications. They are significant since many conductors can be interwoven into a smaller package. Multi-layer flex circuits are the best circuits to use in order to overcome design challenges like specific resistance requirements, unavoidable cross-overs and in eliminating crosstalk in very sensitive circuits. For information about how you can use PCBs to come up with a flex circuit, please visit us at our site https://www.rushpcb.co.uk

4). Rigid-flex circuits

Rigid-flex circuits are a combination of flex and rigid circuits so they combine the advantages of the 2 circuits. They are a hybrid construction made of flexible and rigid substrates which are laminated together in a single package. As if that is not enough, these circuits can be interconnected by means of plate-through holes. Different from that, rigid-flex circuits are multilayer designs even though it is possible to come up with a two-layer design. These circuits find vast applications in some microelectronic chip-packaging applications like in constructing hearing aids. Additionally, they are used in military product design.

All the types of flexible circuits have provided viable solutions to existing problems especially in the electronics world. We at RushPCB believe that the sky is the only limit in the advancement of flex circuits and technology at large. We are ready to help you understand more about flex circuits and get to design some using PCBs. Please visit us at https://www.rushpcb.co.uk/quote/

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Evolution of Electronic Rigid-Flex Printed Circuit Board

Evolution of Electronic Rigid-Flex Printed Circuit Board

Flexible or flex circuit is the technology of assembling circuits by mounting several electronic devices like polyimide and translucent conductive flexible plastic substrates. On the other hand, rigid-flex PCBs allow the boards to conform to a certain shape or to flex during the time it is on use. There are several types of rigid-flex circuits depending on their construction; single-sided flex circuits, back bared flex circuits or double access, sculptured flex circuits, multilayer flex circuits and rigid-flex circuits.  Have you ever wondered how rigid-flex PCBs emerged and what they really are? Join us https://www.rushpcb.co.uk/blog/ as we discuss the evolution of rigid-flex PCBs.

The first question that comes into your mind is what rigid-flex PCBs are and how they are made. A rigid-flex PCB is a hybrid construction flexible board consisting of flexible and rigid substrates laminated together in a single structure. Rigid-flex Printed Circuit Boards can be shaped to suit the specifications of design as asserted by the customer. This allows for freedom in the packaging geometry and a reduction in the interconnections and at the same time retaining the density, precision and the repeatability of the PCB is retained. These PCBs are usually multilayer structures although two metal layer constructions are used sometimes. Rigid-flex PCBs find numerous applications in the electronics industry especially in medical, military and aerospace electronic equipment.

So what is the history of rigid-flex PCBs? Over the years, Rigid-Flex PCBs and PCBs at large have enjoyed tremendous developments introduced by changes in technology. These changes can be attributed to the development of Printed Circuit Boards. In the early 1900’s, the concept of PCBs was introduced by the construction of electrical paths on isolated surfaces of boards.  This was used in developing and upgrading gramophones and radios. Consequently, the notion of the ‘’through-hole-technique’’ was introduced and a rigid-flex PCB was invented. The fabrication of PCBs was introduced later by a PCB manufacturer in the U.S where they used the automated soldering techniques. PCBs were later adopted by the U.S army and several strides to upgrade them were made. This marked major developments in the electronics world.

From the high speed analog and digital designs to high layer count boards and high pin count BGA with several methods of fabrication like electro-mechanical assembly, box build assembly, cable harness assembly and backplane assembling process, the demand for customized PCBs in various industries increased significantly. With steep competition in the market, PCB manufacturers have always been challenged to differentiate themselves from the chunk by introducing new inventions. As a result, advanced methods used by PCB manufacturers like Surface Mount Technology (SMT), Integrated Circuits (ICs) and Hybrid Circuits have led to state-of-the art-techniques.  Sequentially, there is a range of Printed Circuit Board designs which can be fabricated to suit the demands of the customer. These are the rigid-flex PCB. As if that is not enough, older design methods of Rigid-Flex PCBs were characterized by constructions by many layers of adhesives in the rigid areas constructions. However, due to the high thermal coefficient of thermal expansion of adhesives (about 10 to 20 times that of FR-4), the technique of placing vias under a substantial amount of stress during thermal cycles which occur during multiple assembly cycles, RoHS assembly and component temperatures was introduced. Using adhesives in the rigid areas might cause the formation of cracks in the copper plating within via holes. Are you in need of a Rigid-Flex PCB? Please visit us today at https://www.rushpcb.co.uk and have the opportunity with the experts. We value all customers from all over the globe

Different from that, there is flexibility in the methods of fabricating rigid-flex PCBs with respect to the micro-drilled holes, material thickness, PCB profiling, surface finishing and solder-mask capabilities. There were some improvements in the functional layouts and design with high-end customizations in the PCBs mechanized in several multilayered boards. With the advancement in technology, the PCB assembly has been expanded to incorporate rigid-flex PCBs with regards to the consigned Printed Circuit Board assembly and complete turnkey solution. This has facilitated tendering to the exact needs of the customers with cost effective approaches being used in the fabrication approaches.

In the current market, most of the PCB manufacturers and fabricators like RUSHPCB provide Rigid-Flex PCBs which have the capability of integrating multiple PCB assemblies and other electronic elements like input, display or storage devices without using cables/connectors and wires and replacing them with light and thin composites which integrate wiring in flexible ribbons and wiring in ultra-thin. Such PCBs have fine spacing or lines, blind and buried vias, high aspect ratio vias, high layer counts which are over 20+, RoHS assembly compliance and high operating temperatures. However, some developments have created plated hole reliability and potential via issues.

So what are the advantages of using Rigid-Flex Printed Circuit Boards? To begin with, these circuit boards combine the merits of rigid and flexible PCBs. Consequently, there is a variety of advantages especially in signal transmission, overall size, stability and PCB assembly. We at RushPCB produce various varieties of Rigid-flex PCBs which can be adjusted to suit your specifications. Moreover, such PCBs have rigid areas and flexible areas thus reducing the number of layers needed for a single board. This translates to using less copper thus the cost of a single board reduces appreciably. As if that is not enough, our Rigid-Flex PCBs combine FR4, polyimide, and thin laminate thus the final product is of high quality. In the same token, the PCBs are rigid and they can connect rigid boards without using connectors or cables thus there is a better signal transmission.  Please visit us today https://www.rushpcb.co.uk . We have been on the market for long and our products are exceptionally unique.

Table showing a truncated history of electronic rigid-flex PCBs

YearApplication
1960’sRigid-flex PCBs were used in applications for NASA
1970’sRigid-flex Printed Circuit Boards were used on Missiles and Fighter Aircraft for reduced weight
Early 1980’sRigid-flex PCBs were used in high reliability military electronics
1988Military version of the VAX computer with the help of electronic Rigid-flex PCBs
198924 layer back panel of Military Avionics using REGAL Flex
1990Invention of Notebook Computer
1991Commercial Avionics Flight Box using rigid-flex PCBs
1993Automotive Engine Control Navigation System was invented using rigid-flex PCBs
1994Boeing 777 instrumentation
2000’sImplantable Medical Chips using rigid-flex PCBs

With the discussion above, you must have some questions about Rigid-Flex PCBs or any other PCB of your choice. What is the cost of a Rigid-Flex PCB? How is it fabricated? How can I get a Rigid-flex circuit that suits my needs? Please smile and visit us at RUSHPCB.CO.UK we have a team of dedicated experts who are ready to help you each second of the clock. The interests of our customers come first so we assure you of happiness while interacting with us.