Rigid PCB is an inflexible and solid Printed Circuit Board. We cannot bend them or force them out of shape. It is very difficult to fold them or modify them after their manufacturing. Rigid PCB is made from the solid substrate and they have copper tracks. They also include component layouts where we solder active & passive components through automated or manual techniques. The aim of this article is to guide you regarding Rigid PCB and tell you everything you need to know.
Features and Benefits of Rigid PCB
Rigid PCB offers many benefits when we use them for commercial and industrial electronic systems. We mainly choose them because,
- We can manufacture them to fit into any device instead of designing a device according to the specifications of the PCB.
- They are compact and lightweight. Therefore, they have a smaller size.
- We can design them without contact crimps or connectors. So, they are reliable when it comes to high-end applications.
- Since they have a lesser number of interconnects, hence they have a smaller chance of circuit failure.
- They can withstand extreme temperatures because of their thermally stable structure. This advance property makes them a suitable option for aerospace and military applications.
- They require lesser material for manufacturing. Therefore, expenses for material procurement and manufacturing are reduced.
- Rigid PCBs offer good resistance to ultraviolet radiation, aggressive oils, and harsh chemicals. Hence, we can use them in marine applications.
- We can design them such that we can easily surface mount them on both sides.
- It is possible to customize a rigid PCBs to meet special industrial requirements.
- We can manufacture them robustly to withstand vibrations, high impact, shock, and other aggressive conditions.
Applications of Rigid PCB
We tend to use Rigid PCBs when we are looking for maximum adaptability and reliability. If we don’t want the circuit to bend under the applied stress then we use Rigid PCBs. They have evolved at an enormous pace in the last few years and are now used in a variety of applications. This has led to an increased demand for Rigid PCBs, the likes of which are unprecedented.
Most of the computer components today rely on Rigid PCBs. For instance, computer hard drives revolve at very high speeds. Therefore, it is necessary that their adjoint circuit can withstand the consequent vibrations. Also, if the hard drive operates for a long time then it will get very hot. So, the PCB will have to face high temperatures. Therefore, we use Rigid PCBs because they can withstand these extreme conditions and the data is safely read and written on the hard drive.
These conditions are not subject to computers only. Rather, most of the electronic systems today like PlayStation, televisions, microwaves, refrigerators, and printers have these extreme conditions. Therefore, we have to use rigid PCB because their performance isn’t affected by extreme conditions.
Most of the electronic hardware in modern automobiles rely on rigid PCBs. These include anti-lock braking systems, instrument panels, engine management units, airbag controllers, and dash systems.
We can design rigid PCBs to fit into small spaces or irregularly shaped craters. This provides us flexibility in the manufacturing process. We can sync the circuits with other electronic modules without using bulky connectors or cable ties. Weight is also a concern in many vehicles. Therefore, even a small addition can make a huge difference. Rigid boards allow us to effectively address these concerns as compared to conventional alternatives.
The electronic components in automobiles have to withstand extreme conditions. They experience extreme vibrations because of driving on the rough terrain. They are also exposed to extreme cold and heat from the air conditioner and the engine. Therefore, we must use rigid PCBs because they are the only ones capable of withstanding these conditions.
Smartphones are handheld, therefore we need to make them small, portable, and lightweight. So, we need a PCB which can perfectly sync the core components and hold them together. Therefore, rigid PCBs are an ideal candidate for smartphones.
We take our smartphones everywhere with us so their hardware must withstand the changing environment and temperature fluctuations. Therefore, we cannot use conventional PCB. So, we look towards a rigid PCB.
Nowadays, most smartphones are water-resistant and come with water-repelling cases. These allow a smartphone to work even when it is submerged in water or any other liquid. These service conditions are too demanding for conventional PCBs. Hence, we have to once again rely on rigid PCBs.
The material of Rigid PCB
The performance of rigid PCBs depends mainly on the substrate material which constitutes the adhesive and dielectric films. We mostly use Polyester for manufacturing low-end rigid PCBs. However, for manufacturing high-end rigid PCBs we use PTFE and Kapton. These are a bit expensive and are therefore deployed in aerospace and military applications.
When we compare these three materials, we come to see that Kapton has the highest dielectric constant. Therefore, it has superior mechanical and electrical properties. These properties sustain even in high temperatures. However, these are more expensive and readily absorb moisture. In comparison, polyester doesn’t absorb moisture but it can’t sustain its performance at extremely high temperatures. We mainly use PTFE in high-frequency applications that require low dielectric constant.
Manufacturing of Rigid PCB
There are different technologies for manufacturing rigid PCB and we choose between them according to our requirements. Now we will take a look at some of them.
Layer Stack up Technique
One way to manufacture rigid PCBs is by stacking up layers of rigid material in a selective and orderly manner. We can then use through-holes for establishing connections between the layers. We can easily reduce the volume of the finished electronic product by using the stack up technology. This will allow rigid PCBs to withstand extreme contact pressure and intense heat strokes. Therefore, we will get better performance and improved reliability.
Industrialists came up with the idea of rigid PCB in the 70s. Since then, the stack up technology is widely deployed for fabricating rigid PCBs. With the passage of time, many people came up with different innovations and the standard procedure was modified. Today, the most reliable variant is to apply glass epoxy resin (FR4) on a rigid board. Also, we apply a solder mask for protecting the circuit pattern on the rigid board.
We mostly use Kapton as a substrate material for making the core. We use a mixture of Kapton and acrylic for making a film that protects the circuit pattern. In this case, the adhesion is dependent on the prepreg which has a low flow rate. We laminate all these elements so that we can fabricate the rigid PCBs.
Rigid substrate material allows for excellent dielectric properties which are suitable for impedance control and high-frequency signal transmission. Therefore, they can also withstand the extreme environment, radiations, and temperature shocks. Hence, we can ensure that the electronic product will run smoothly.
Rigid PCBs can solve the issue of thermal dissipation and loose contact by taking care of the connectors. Therefore, we can improve the overall reliability of the electronic product. Towards the end of the manufacturing process, we can try to bend the PCB. If it is successfully bent then it doesn’t meet the electrical and mechanical performance standards. This allows us to effectively perform quality control and modify the process if need be. Therefore, we can achieve the required degree of rigidity and consequently the required level of performance.
Shortcomings of the Stack Up Technique
When we manufacture rigid PCBs through the stack-up technique then they have comparatively high density and low yield rate. Therefore, it is difficult to repair them in case of a breakdown. We need to embed the rigid base within the substrate material during the manufacturing process. So, there is a large wastage of raw material and the manufacturing process becomes difficult. Therefore, we need some new technology for manufacturing rigid PCBs.
When we use the embedding technique, we integrate the circuit units into internal rigid boards. So, after that, we can go about the bottom-up approach. So, the interconnections are unavailable between the two layers and the connection is mainly dependent on the buried VIAS and blind VIAS. Embedding allows us to reduce the raw material wastage and improve the performance of the rigid boards.
Since we are layering up in the embedding technique, therefore the effective surface area is much larger. So, the usage rate of the substrate material is improved. We can further enhance this by using through-holes to establish a firm connection in the circuit.
Embedding technique also allows us to address the problems of high density. It also offers a relatively easier manufacturing process. Therefore, we prefer this technique over the stack-up technique.
If you are looking for a reliable and durable rigid PCB then you are in the right place. MOKO Technology is a renowned name in the PCB industries and we have a wide experience in manufacturing rigid PCB. Our products are of premium quality and our services are of a superior standard. We have a large setup with mass production capacity. So, we can offer customized products as per your needs. Feel free to contact us for a quote or any further questions.