Most hardware engineers and inventors know what a Rigid Flex is. It is both the most frustrating part of a significant circuit and yet is, at the same time, the most beneficial and essential part of the circuit.
Its layout and the components that it contains gives it an edge above the rest of the PCB at an average inventor’s disposal. More importantly, thanks to the orientation of the Rigid-Flex PCB, a designer can maneuver it around different parts of the circuit and also connect other parts of the circuit.
That said, there are also various problems that come with using such a peripheral as it is also one of the most complicated Printed Circuit Boards to integrate. In this guide, we will go over the basics of a Rigid-flex circuit board, its layout, its problems, and their solutions.
1、What is a Rigid Flex PCB?
A Rigid-Flex Printed Circuit Board is a combination of various rigid and flexible technologies that tend to make up a very diverse and effective combination of the two. Unlike most Printed circuit boards, a Rigid Flex PCB has multiple different layers of both rigid and flexible technology so that it may be able to function at an optimum level without the risk of breaking.
Contrary to popular belief, the rigid-flex does not stay in a fragile state; instead, it is in a steady state of a curve. The shape that the Rigid flex takes is very similar to a spring, where if you happen to stretch or compress it will return to its original state.
It is also right about the rigid Flex except that you can bend it whichever way you please, but it will come back to its original position. However, that doesn't mean that all Flex PCBs have a constant shape, various devices have a somewhat flexible PCB that allows them to have no regular shape.
An excellent example of one such PCB is that of printers, as they boast a very flexible tape that allows them to move back and forth without any restrictions. The Flex PCB is one of the essential parts of a printer, as it is quite impossible for the machine to print otherwise.
Image 1: Rigid Flexible Circuit
2、Rigid Flex PCB Design
To say that the design for the Rigid Flex PCB is complicated would be an understatement, not only is it one of the most hectic of PCBs to craft, but it is also a PCB that requires a very meticulous design. Due to there being various layers in a rigid Flex PCB, a designer must give intense attention to each of these layers so that one may not be different from the other or may intersect the other.
So to get a better understanding of how a Rigid Flex PCB works, let’s dive deeper into its design and the many different layers of such a PCB.
Before we move onto the proper design of such a PCB, you must also keep certain factors in mind. Technology is always changing and evolving as the years go by; this means that people come up with new designs and methods of creating a Rigid Flex PCB are and will always be different, so there is no absolute way of making a rigid Flex PCB.
Moreover, depending on the application of the rigid flex and its purpose, the design and layout can be very different from the standard design, so keep in mind that the purpose of the PCB can significantly affect the design of the PCB.
Image 2: Rigid Flexible Circuit
The thickness of a Rigid Flex PCB is very subjective, as depending on the purpose of the build the difference can be minor or incredibly significant. The average board thickness for a rigid Flex PCB can be somewhere between 0.2mm and 0.4mm. 0.2mm is the average thickness of a single layer PCB circuit, and 0.4mm is the average thickness of a PCB with nearly 4 layers.
Image 3: Rigid Flexible Circuit
The materials used to construct a proper Rigid Flex PCB are copper and the adhesive material used to join both the rigid and flex layers together. Although the choice of material for this is very strange, to say the least, this special adhesive prevents the copper from cracking or breaking.
Combining rigid Flex PCBs is also a daunting task because there are too many variables to consider, which means you can make many mistakes that in turn destroy the entire circuit and application.
There are many different PCB assembly types which include Flip Chip, Wire harness, Ultrasonic Welding, and in-circuit testing to name a few. All of these different types of assembly methods have their benefits, and each one of them is complicated in their own right.
Some designers and manufacturers use several of these methods in conjunction with other methods to create a Rigid Flex PCB that is both durable and flexible. All of these methods combine to make an effective and efficient circuit board.
Image 4: Rigid Flexible Circuit
PCB Design Considerations
When you are crafting your Rigid-Flex Printed Circuit Board, there are certain things that you must first take into consideration, as they can significantly reflect on the overall outcome of the application. The first thing that you must consider is the electromechanical factors.
Whenever you get around to making a PCB circuit, you must always think regarding electromechanical factors, and how they will affect the result of the application. First, you have to consider the bend to thickness ratio, the thicker the wire, the larger the curve. If your circuit happens to be very thick, then it can increase the risk of failure and can sabotage the entire circuit.
Another consideration that you must also make is the bend line of every Rigid Flex PCB. Seeing how nearly all flexible circuits have bend lines that significantly affect their routing, you should be careful not to place any components on or around it.
Furthermore, it would be best if you did not repeatedly bend the flex circuits as it places stresses on the various surface-mount pads and through holes. There is a remedy for this as you can use through holes plating to reduce stress, you can also add additional padding to anchor the pads.
When you are designing your trace routing, you should also take into consideration some practices that will reduce the stress that you might otherwise experience on your flex circuit. Try to use curve traces instead of 90° or 45° angles as they can carry more power without having the risk of bending and breaking.
You can also use hatched polygons so that your circuit may carry a ground or power plane without having to compensate on the flexibility of your circuit.
Image 5: Rigid Flexible Circuit
3、Rigid Flex PCB’s Technology and Production Process
The technology that most manufacturers use on a PCB differs depending on the manufacturer, type of PCB, and the efficiency of the PCB. The efficiency of the PCB is one of the unique attributes about a rigid flex's PCB, as depending on the task of the PCB the technology that a designer uses can differ significantly.
An excellent example of this is the use of a rigid flex in a printer and a 3D printer. While both of these machines are accomplishing the same task, bringing a soft copy into hard copy, the technology being used is significantly different in both of these machines.
Seeing how the purpose of the PCB greatly influences the technology being used in it, it will undoubtedly also affect the PCB production process. At this point, it is obvious what are the factors that can influence the production process, so rather than talking about the factors that influence it we will discuss the process itself.
The production process of every PCB starts with stacking various layers of metal and other circuit boards. This part of the process is called the stack up.
The Stack Up
The stack up is the process of placing the layers for the rigid flex printed circuit board. Depending on the Rigid-flex circuit board the stack up can be of one, two, or four layer(s), and layers increase by the object's application as well as its uses.
Think of these layers as ingredients to a recipe, they all might be completely different from the other, yet they all combine to make for a delicious recipe, with each ingredient adding greatness to the dish in some way, shape or form.
The process is straightforward, but it is quite difficult to explain without the help of visual aid, so to better explain the process take a look at the following diagram.
Image 6: Rigid Flexible Circuit
As you can see in the diagram each of the individual layers, take center stage, and you can see the difference between each one. Now that you know the major differences between each of these PCBs the next two diagrams will show you all of the components that go into making a PCB.
Do note that this is a very generic view of all of the various components that go into making a PCB and that these components can significantly differ depending on the type of PCB that you intend to make and its purpose.
Image 7: Rigid Flexible Circuit
Image 8: Rigid Flexible Circuit
4、 Benefits of Rigid-Flex PCBs
Moving onto what is possibly the most important part of this guide, the benefits. Why do people use Rigid flex PCBs? To say that because it is somewhat elastic is to do this magnificent work of engineering injustice.
The Rigid Flex PCB has many different benefits other than just reaching and connecting other circuits, which makes it possibly the most versatile type of PCB’s in the world.
The first of the many advantages of a Rigid Flex PCB is the customizability. Now some of you might be thinking that all PCBs are customizable; this PCB is a little different regarding customizability. Unlike generic PCBs that shape how the device will be, a designer can customize the size and shape of the Rigid Flex to fit the device. In other words, if you happen to make a design that you like, but are having trouble making a proper PCB for it, then you can craft a rigid-flex PCB to fit the design better.
Another one of the many benefits of the rigid-flex is its compact and flexible design. Thanks to the compact and flexible design of these printed circuit boards, the size of various accessories can significantly be reduced. The compact design of a rigid-flex board always tends to give way for more portable accessories and equipment that do not compromise on functionality for size.
The rigid-flex design also allows for more components in a certain device, which in turn greatly improve the overall product. Thanks to the flexible design there are various advancements and modifications that the manufacturer can make to their design to accommodate a variety of different modification that can improve the overall product.
Rigid Flex PCB is a very famous choice among various mobile phone manufacturers, as it gives them the liberty to make a PCB that caters to the design and specifications they have in mind.
As the name implies, Rigid-Flex technology allows for the best of rigid and flexible circuitry in their boards. It means that a Rigid Flex PCB can give you all of the benefits that come with a rigid and flexible circuit without having any of their disadvantages. It is possibly the single biggest advantage to a Rigid Flex PCB as it is capable of giving manufacturers all of the positives of these two individual circuit boards, without much of the negatives.
Another benefit of rigid-flex is its amazing heat absorption capability. Unlike the other two types of these circuits, a rigid-flex PCB can manage to take a lot more heat thanks to the technology used in these types of circuits.
The addition of polyimide to Rigid Flex PCB makes it exceptionally resistant to heat, as well as UV rays and radiation. What makes this feat more impressive is that Rigid Flex PCB are a lot less thick as compared to their other counterparts. With the maximum height of a 4-layered PCB going up to 0.4 cm, a rigid-flex PCB is very extremely thin yet more functional than other PCB.
5、 Rigid Flex PCB Applications
The rigid-flex PCB has various applications in different types of accessories and equipment that we use on a daily basis. One of its most obvious uses comes in a smartphone application. In the current age, smartphones have to be incredibly thin yet very functional, something that can only be achieved by using rigid-flex technology.
Another very famous application of rigid-flex PCB comes in various computer electronics all of which use some form of rigid flex PCB. One of the many components that use rigid-flex technology is the hard drive; it does to keep up with the ever-increasing write speeds of today's computer. Using a rigid flex for a hard drive is great as it keeps the hard drive cool even when it is working at its peak.
Rigid-flex PCB is also used in the field of medicine. Most recently, an invention called the pill cam allows you to see the inside of a person's stomach to examine the internal damage. This pill is made of well designed rigid flex circuits that are very effective.
6、Rigid Flex PCB Cost
The cost of a rigid Flex PCB is very different depending on the type of rigid-flex that you get and where you get it from. A rigid-flex PCB can have somewhere between one to four layers of different materials to make up the PCB.
The prices of a Rigid Flex PCB vary greatly depending on the type of PCB that you want, and the layers that it will contain. It means that depending on the type of PCB that you require, the price will increase or decrease.
Another factor the makes up for the cost of the PCB is the developer or manufacturer. Depending on the manufacturer, the price can be reasonable or absurd. However, this high price is justified by the amazing quality of the product as well as the immense attention to detail that the more expensive manufacturer will give to your product.
Rigid-Flex PCBs are one of the most important and effective types of PCBs in the current market. Not only can they absorb much heat, but they can also make for a very small and compact circuit that can be as effective as bigger circuits. Finding the right manufacturer that can give you cheap service without having to compromise on quality can be very hard. Which is why OURPCB can offer you some of the best services of the current time along with the best price. You can contact them at (insert e-mail and Phone number)