What Is A Rigid PCB?
There are many kinds of printed circuit boards and many kinds of classification standards. If divided according to the raw materials, there are three kinds of printed circuit boards: flexible printed circuit boards, rigid printed circuit boards, and rigid-flex printed circuit boards. A rigid PCB is mainly manufactured by using copper laminates as the base material. It is not easily deformed, which also means that it cannot be bent. And this article will unfold the details about rigid PCB and general information about the PCB industry.
Characteristics of Rigid Printed Circuit Boards
First: producible. Being producible does not mean that rigid printed circuit boards can be produced. It refers to rigid printed circuit boards that can be produced in large quantities on production lines, creating an effect of scale. This greatly improves the efficiency of production.
Second: designability. There are special rigid printed circuit board design companies on the market, for customers to design rigid printed circuit board schemes. The engineer designs Gerber and BOM according to the customer’s requirements.
Third: testability. For the rigid printed circuit board produced by the factory, the quality department must carry out a detailed quality inspection to ensure that all the parameters of the rigid printed circuit board are qualified before it can be sent to customers.
Fourth: high density. There are many dense components on the rigid printed circuit board, and with the continuous development of the rigid printed circuit board, the components become more and more closely related to each other.
Advantages of Rigid Printed Circuit Boards
First: small size. The tight connection between components on top of the rigid printed circuit board can save the size very well. And the size will be smaller and smaller, and the products that need circuit boards will be more and more miniaturized.
Second: small noise. The reason is that the components are closely connected and the distance is short. As a result, the current is minimized, and there is less electromagnetic interference so less noise is produced.
Third: anti-mobility. The components are welded on the rigid printed circuit board, and even if the external environment is bad, the components will not move.
Fourth: easy to repair. After the rigid printed circuit board is broken, the repair steps are relatively simple, and it does not take much time. Maintenance methods generally include observation methods, static measurement methods, online measurement methods, and so on.
The Difference Between Rigid PCB and Flexible PCB
As mentioned earlier, the printed circuit board is divided according to the raw materials, and there are three kinds of PCB: rigid printed circuit boards, flexible printed circuit boards, and rigid-flex printed circuit boards. The first thing that came up was a rigid printed circuit board. We may wonder what’s the difference between a rigid printed circuit board and a flexible printed circuit board.
First: shape. Most rigid printed circuit boards on the market are square or rectangular.
Second: the conductivity of the line. The heat dissipation performance of the rigid printed circuit board is better than that of the flexible printed circuit board. Therefore, if the heat dissipation condition is the same, the components of the rigid printed circuit board are closer, and the size of the rigid printed circuit board is smaller, which helps reduce the volume of the product. Because the heat dissipation of the flexible circuit board is taken into account, extra width or spacing is needed for the wires.
Third: flexibility. Different from the rigid printed circuit board, good flexibility is the biggest feature of the flexible printed circuit board. Flexible printed circuit boards can be bent arbitrarily, yet their bending function has not been affected. Mobile phones and tablet screens tend to use flexible printed circuit boards. The flexibility of flexible printed circuit boards is unmatched by rigid printed circuit boards. Flexible printed circuit boards have better performance for a large number of bending cycles.
How Are Rigid PCBs Manufactured?
The following steps introduce how rigid PCBs are manufactured in general.
Step 1: Design
Before the manufacturing process begins, the rigid PCB needs to be designed by a CAD engineer based on a working circuit schematic. Once the design process is complete, a set of documents is provided to the rigid PCB manufacturer. The documentation includes Gerber files, which consist of layer-by-layer configurations, drill-down files, pick-and-place data, and text comments. What’s more, the documents should also provide processing instructions critical to manufacturing about the PCB specifications, dimensions, and tolerances.
Step 2: Making preparations before the fabrication
Once the PCB manufacturer receives the files from the designer, they can begin creating the manufacturing process plan and the product packaging. The plan will be defined by listing such things as material type, surface finish, plating, work panel array, process route, etc. In addition, a set of physical artwork can be created with the film plotter. The artwork will include all layers of the rigid PCB as well as artwork for the solder mask and terminology markers.
Step 3: Preparing materials
The PCB specifications stated by the designer determine the type of material, core thickness, and copper weight required in the material preparation process. Single-sided and double-sided rigid PCBs do not require any inner layer handling and go directly to the drilling process. If the rigid PCB is multi-layered, a similar material preparation will be performed, but it will be carried out in the form of an inner layer which is usually much thinner and can be stacked to a predetermined final thickness.
Step 4: Drilling
The drilling process is performed by a CNC-controlled multi-station drilling machine. The drilling process creates a clean, smooth hole wall that does not damage the inner layer, but the drilling can provide a pathway for inner layer connectivity after plating and the non-through hole eventually becomes the site of the through-hole assembly. Non-plated holes are typically drilled as an auxiliary operation.
Step 5: Copper Plating
Electroplating is widely used in rigid PCB production where through-hole plating is required. The objective is to deposit a layer of copper on a conductive substrate through a series of chemical treatments, and then increase the thickness of the copper layer to a specific design thickness, typically 1 mil or greater, through subsequent plating methods.
Step 6: Outer Layer Treatment
Both sides of the top and bottom layers are coated with photoresist. The two sides are aligned using the outer layer artwork and tooling holes, and then each side is exposed to UV light to detail the optical negative pattern of traces and features. The UV light falling on the photoresist bonds the chemicals to the copper surface, and the remaining unexposed chemicals are removed in a development bath. The next step is to remove the bare copper through an etching process. This leaves copper traces hidden beneath the photoresist layer. The resist is then peeled off, leaving traces and features on the outer layer. Automatic optical inspection can be used to find defects in the outer layer before the solder mask.
Step 7: Solder mask
The application of the solder mask is similar to the outer layer processes. The main difference is that a photo-imageable mask is used over the entire surface of the production panel instead of a photoresist. The artwork is then used to take images on the top and bottom layers. After exposure, the mask is peeled off in the imaging area. The goal is to expose only the area where the components will be placed and soldered. The mask also limits the surface finish of the rigid PCB to the exposed areas.
Step 8: Surface Finish
There are several options for the final surface finish, such as sink gold, sink silver, OSP, lead-free solder, leaded solder, etc. All of these methods are effective, but making a choice is based on the design requirements. Gold and silver are applied by plating, while lead-free and leaded solder is applied horizontally by hot air solder.
Step 9: Marking
Most rigid PCBs have markings on their surface. These markings can prompt reference marks and polarity marks during the assembly. Other markings can be as simple as part number identification or manufacturing date codes.
Step 10: Depanelization
Rigid PCBs are produced in complete production panels and need to be moved out of their manufacturing profile. Most rigid PCBs are set up in arrays to improve assembly efficiency.
Most arrays are either contour milled on a CNC milling machine using a carbide tool or etched using a diamond-coated serrated tool. Both methods are effective and the choice of method is usually determined by the manufacturer, who usually approves the arrays built in the early stages.
Step 11: Testing
Rigid PCB manufacturers typically use a flying probe or bed-of-nails testing process. The test method is determined by the number of products or available equipment.
What Are the Rigid PCBs Used for?
The rigid PCB is the carrier that supports the components as well as makes the electrical connection and is a very important electronic component. After rigid PCBs are used in electronic equipment, the errors of manual wiring can be avoided and operations like automatic insertion or placement of electronic components, automatic soldering, automatic detection, etc. can be completed due to the consistency of similar rigid printed circuit boards. The use of rigid PCBs ensures the quality of electronic equipment, improves labor productivity, reduces costs, and facilitates maintenance.
When Should you Use a Rigid PCB & What Are the Benefits?
When to choose to use the rigid PCB is determined by the following two factors.
The first factor is the customer’s application needs. Rigid PCBs can be used in many different products. In particular, the use of rigid PCBs in larger products (such as TVs and desktop computers) is advantageous.
The second factor is the advantages of rigid PCBs. Rigid PCBs have the following advantages: the controllable cost, the capability of accomplishing large production, the shortened lead time, and the reduced installation costs.
As to its benefits, it can reduce production costs due to material selection, component and design techniques, reduced number of holes, surface finish requirements, solder resist layer requirements, test parameters, and lower environmental impact.
Examples of Rigid PCB Applications
Rigid PCBs have a significant role in various fields. The following examples are only some of them.
- Medical equipment industry
- Industrial control industry
- Automotive electronics industry
- Smart home industry
- Lighting industry
- Aerospace industry
- Security industry
- Military industry
Development of Rigid Printed Circuit Boards in China
For electronic products, the printed circuit board is the most important component, and the rigid printed circuit board is widely used in China including consumer electronics such as mobile phones and tablets, healthcare, automation equipment, uninterruptible power supplies, data centers, automobiles, and so on. At present, there is no product to replace the printed circuit board.
1) Since Economic Reform and opening up, especially since the 1990s, China’s printed circuit board industry has made rapid progress. It is not exaggerated to say that in the world the most complete printed circuit board production base is in China, and the outstanding printed circuit board enterprises are also in China. At the same time, China is also the largest country of printed circuit boards in the world.
The printed circuit board is divided into high – medium – low three levels. Small and medium printed circuit board company in China is mainly medium-low grade. High-end circuit board enterprises are generally large companies and foreign companies represented by state-owned enterprises. Small printed circuit board companies, plant rental and machinery and equipment less input, compared with large circuit board companies, has a lower cost, and the price is relatively low. The company scale of printed circuit board companies in China can not be compared with foreign companies and large state-owned enterprises.
2) Chinese rigid printed circuit board enterprises are concentrated in the Yangtze River Delta, Pearl River Delta, and Bohai Rim. Yangtze River Delta, Pearl River Delta, and Bohai Sea Rim are three important economic belts in China. Printed Circuit board companies are mainly concentrated in these places. In recent years, affected by industrial transfer, some printed circuit board companies have moved to inland cities, such as Ganzhou city in Jiangxi Province. There are many printed circuit board factories. But on the whole, printed circuit board companies mainly concentrated in the Yangtze River Delta, Pearl River Delta, and Bohai Rim area. The upstream and downstream matching of printed circuit boards in these regions is relatively perfect, the procurement of raw materials is relatively convenient, the transportation is developed, and the logistics cost is relatively low.
3) Rigid circuit board industry is highly competitive. China’s rigid printed circuit board companies are mainly concentrated in the low-end market, and the access threshold is relatively low. Each printed circuit board company often fights a price war, so the competition is very fierce.
In 2021, compared with previous years, the sales revenue of rigid circuit board enterprises did not increase significantly. The delivery time has been extended.
Industry experts point out that there are two main reasons for the longer delivery time:
1) Chip shortage
Last year, the pandemic and other reasons caused the world chip supply shortage, so the production of rigid printed circuit boards was greatly affected. Due to the extension of delivery time, the orders of terminal customers from foreign printed circuit board customers are reduced, and also reduced orders to Chinese circuit board companies. And not only chip shortage, but other components are also in short supply. Printed circuit board manufacturers often can not buy components. Many downstream printed circuit board enterprises, such as automobiles, mobile phones, and other electronic products, due to the extension of the printed circuit board delivery, have to postpone the delivery. For example, due to a shortage of chips and other related components, the production of smartphones in 2021 is down by more than 40 million units from the previous year. Among them, Apple’s 2021 production plan is down by 10 million units.
China’s auto industry has also been affected by a lack of chip supply, with production falling for months. It’s not just the auto industry. Other consumer electronics are also affected, such as range hoods and other home appliances. Customer orders have also been reduced due to longer delivery times.
2) Government’s energy consumption control policy
In 2021, the electricity supply was tight in many places in China, and many cities implemented power rationing policies. The rigid circuit board company could not start production normally.
Analysis of the Printed Circuit Board Industry Chain
- Upstream of the printed circuit board industry chain
The printed circuit board industry chain is divided into upstream, midstream, and downstream. The upstream industry chain refers to raw materials generally. In an electronic product, the proportion of the printed circuit board in the total cost is relatively large, generally more than 50%.
- Downstream of the printed circuit board industry chain
The downstream range of the printed circuit board industry chain is very broad. It can be said that all electronic products need printed circuit boards, including common mobile phones, computers, television sets, network switches in data centers, etc. And with the development of society, the application scope of the printed circuit board is also larger. Last year, according to the survey, the top areas of demand for printed circuit boards were communications, automobiles, and consumer electronics.
- The communications industry
The communication industry involves a variety of products, and different communication products need different printed circuit boards. Most of them need rigid printed circuit boards, but also some communication equipment needs flexible printed circuit boards and high-frequency printed circuit boards.
The biggest characteristic of the flexible printed circuit board is good flexibility, which can be bent arbitrarily, with a lighter weight than the rigid printed circuit board. But the heat dissipation is poor. When flexible printed circuit boards first appeared, they were used in the military. The development of flexible printed circuit boards has been widely used in civil fields, such as mobile phone screens, liquid crystal displays, and other consumer electronics.
The High-frequency printed circuit board is the full name of the high-density interconnected printed circuit board. The density of a high-frequency printed circuit board is higher than that of an ordinary printed circuit board. With the same size, more components can be installed on the board. If the number of components is the same, the size of the high-frequency printed circuit board is smaller. Choosing a high-frequency printed circuit board can reduce the volume of the product.
At present, the communication industry and some smartphones will use high-frequency printed circuit boards. In recent years, the high-frequency printed circuit board has developed rapidly, and the annual growth rate of output value is in two digits. However, the production process of the high-frequency printed circuit board is more complex, and the requirements of the factory are relatively high, so the price will be more expensive than the ordinary printed circuit board.
- Automotive electronics
Originally, the demand for printed circuit boards of cars does not change much. In recent years, with the popularity of new energy vehicles, the demand for printed circuit boards for cars is increasing. The safety requirements of the automobile printed circuit board are relatively high.
- Consumer electronics
Last year, the sales of rigid printed circuit boards declined in China. The most important reason is that the consumer electronics market is saturated because consumers’ purchase intention for smartphones, computers, and other electronic products has decreased. Since mobile phone functions have not changed much, people are not willing to buy new mobile phones. Coupled with the impact of the pandemic, the demand for rigid printed circuit boards in consumer electronics products is expected to be little changed in the coming years.
Rigid printed circuit boards in China’s market scale are growing. There are three main reasons. The first is that the application scope of rigid printed circuit boards has expanded, and the communication field needs more and more rigid printed circuit boards. The second is the increase in the use of multilayer boards, and the price of multilayer boards will be more expensive than the ordinary double panel. The third is the industrial transfer from developed countries in Europe and the United States, bringing advanced technology and management experience.
Development Trend of the Printed Circuit Board Industry
The printed circuit board is used in downstream electronic terminal products. The change in consumer demand for electronic functions affects the technological development of printed circuit boards. The technological upgrading of electronic products is relatively fast, developing toward miniaturization, portability, and multi-function.
For example, in the past, mobile phones only had the function of making calls and sending short messages. Today’s smartphones can be used for shopping, entertainment, bank transfers, learning, and free video calls. The development and change of electronic products promote the printed circuit board toward high density, high performance, and environmental protection direction change.
The higher the density of the printed circuit board, the higher the requirements for wiring width, layer height, and aperture size in factory production. High-frequency printed boards to respond to the demand for high density came into being. HFT boards have fewer through-holes than normal printed circuit boards because of the precise blind and buried holes. This can effectively save the wiring area of the printed circuit board. The density of the printed circuit board is higher.
Environmental protection development
The production process of the printed circuit board is more complex, and the production will cause certain pollution to the environment. Many Pearl River Delta printed circuit board factories have relocated to mainland cities to meet the requirements of the government’s environmental policy. To achieve sustainable and scientific development, circuit board companies use environmental protection materials, and improve production technology as well as scientific treatment of industrial pollution, toward the direction of environmental change.
The high performance of the printed circuit board generally refers to the heat dissipation and impedance performance. With the development of 4G and 5G technology, the data transmission speed is fast and the transmitted information increases. Only the printed circuit board with good impedance performance can meet the needs of modern transmission. Ensure the stability and accuracy of data transmission. It is very important to control the temperature of the printed circuit board within a certain range. Excessive temperature may damage components on the printed circuit board, affecting the stability and reliability of data transmission. So the heat dissipation performance of the printed circuit board is very important.
How Do you Control the Temperature of the Printed Circuit Board?
Dissipate heat through the printed circuit board
At present, FR-4 is widely used. Although its electrical and processing performance is better, its heat dissipation is poor. The heat generated by components mainly depends on the heat dissipation from the air of components.
However, with the development of printed circuit boards toward miniaturization and high-density development, the components are getting closer together, and the area of the components is getting smaller, so it’s obvious that relying on such a small area for heat dissipation is not enough. The components are in contact with the board. If the heat can be transferred to the board, the heat can be emitted through the printed circuit board, which can effectively reduce the temperature of the printed circuit board.
Add heat sink
When a small number of components generate more heat and the temperature is high, a small electric fan can be used to reduce the temperature.
Adopt a reasonable routing design to achieve heat dissipation
The current heat dissipation of the printed circuit board is poor, but the copper foil line and holes can be very good at heat dissipation, so the design of the printed circuit board should consider improving the residual rate of copper foil and increasing the number of holes. In the horizontal direction of the printed circuit board, the components that generate a lot of heat are arranged in the edge position of the printed circuit board, which is conducive to increasing contact with the air. In the vertical direction of the printed circuit board, the components with high heat output are arranged above the printed circuit board to reduce the adverse impact on other components.
The components that are sensitive to high temperature are arranged in the position of low temperature, and the components are staggered in the horizontal plane to prevent heat concentration.
Viasion has 16 years of experience in manufacturing printed circuit boards. Whether you need rigid printed circuit boards, flexible printed circuit boards, or rigid-flex printed circuit boards, or whether your printed circuit board is simple or complex, our company will try our best to produce satisfactory products and provide satisfactory service for you. We will do our best to ensure the delivery date of our products, so that your products may enter the market as soon as possible.
Different Types of Rigid PCB Provided by Viasion
Different types of rigid PCBs provided by Viasion are mainly listed below.
- Single-sided rigid PCBs, double-sided rigid PCBs, and multi-layer rigid PCBs（up to 40+ layers）
- Rigid PCBs made of a wide range of laminates, such as CEM3, normal FR4, high TG FR4, halogen-free FR4, high Speed, high frequency, aluminum base, copper base, ceramic, PTFE, Rogers RO4350, RO4003, RO3003, Arlon 85N, 33N, VT47, Panasonic Megtron 4, Megtron 6, TU872, EM827, ISOLA IS410, FR408…
- Rigid PCBs made on mixed dielectrics (hybrid) constructions, such as FR4 and Rogers; FR4 and PTFE
- Rigid PCB with blind & buried vias
- Micro Vias, Any-Layer HDI rigid PCB
- Rigid PCB with heavy copper (20 oz. outer layer / 10 oz. inner layer)
- IC substrate rigid PCB
- Max panel size: 21″x 59″