What is a Printed Circuit Board (PCB)? A Complete Beginner-to-Advanced Guide

The electronics project failed because the quality of the printed circuit board was low. If you choose an inappropriate PCB manufacturer, you will be wasting time and money on an unavailable substrate. By understanding the mechanism of the printed circuit board,you  will be able to select suppliers that can avoid costly mistakes and supply reliable boards that lead to product success.

What is a Printed Circuit Board?

A printed circuit boards (PCBs) are flat substrates with copper traces that connect electronic components such as resistors, capacitors, and microchips. This board provides mechanical support and electrical connections without using wires.

In the 1950s, printed circuit boards replaced manual wiring circuits. Before that, technicians soldered individual wires between components, but this was time-consuming and costly. Modern printed circuit boards enable the mass production of reliable electronic devices installed in smartphones, computers, medical devices, automobiles, and home appliances.

The structure includes a substrate (foundation), a copper layer (conductor), a solder mask (protective layer), and a silk screen (component labels). Each layer realizes the function of the board.

How PCBs Work

Printed circuit boards are components that are connected to copper pathways. Once you turn on any device, electricity passes on these copper traces. The traces are used as a road that directs current to the required destination.

The PCB design software is utilized by the engineers to map the connections and then construct the board. This eliminates errors such as traces going across one another or fracturing. An efficient board maintains the supply of electricity.

There are two methods of fixing components:

• Through-hole: Metal pins go through holes and get soldered on the back
• Surface mount (SMT): Components are placed flat on solder pads and soldered there.

Surface mount is used in most of the modern boards as parts require less space and machines can be used to place the parts automatically. Surface mount components are significantly smaller as compared to through-hole components.

The reason the thickness of copper is important:

• Thick copper transfers more electricity without heating up – required on power circuits.
• Copper is thin and is used in weak signals but it becomes hot when operating on strong current.
• In high speed circuits, skinny traces lose signal strength.

Choose copper thickness depending on your board. Copper boarding requires power boards to be thick. Simple control boards are also compatible with normal thickness.

Types of Printed Circuit Boards

Single-Sided PCB

Single-sided PCB has copper traces only on one side of the board. Parts are attached to the upper surface and copper traces are wired to the lower surface. This is the simplest and cheapest type of circuit board.

Single-sided boards are suitable for simple electronic devices such as calculators, radios, and LED circuits. However, there is a limit that all wires must fit on one side without crossing. Complex circuits require more than the wiring space that a single-sided board can provide.

Production of single-sided boards is simple and clear. Compared to other substrate types, the number of processes is less and the cost can be reduced. Many hobby projects and simple consumer products use one-sided boards to minimize costs.

Double-sided PCB

Double-sided PCBs are copper traces on both the top and bottom surfaces of the substrate. This doubles the available wiring space compared to one-sided boards. The plated through hole connects the wiring between the two layers.

Many modern consumer electronic devices use double-sided boards. The double-sided substrate has excellent functionality and cost balance. By adding layers, more complex circuits can be realized without switching to expensive multi-layer boards.

Through-hole plating is extremely important in the production of double-sided PCBs. In this plating process, copper is deposited inside the drilled hole and both sides are electrically connected. Without proper plating, the substrate will not operate properly.

Multi-layer PCB

Multilayer boards are laminated with multiple copper layers sandwiched by insulation. In general, there are 4 layers, 6 layers, 8 layers, and more than 20 layers. As layers increase, wiring options and circuit density increase.

Multi-layer boards are essential for smartphones, computers, and advanced electronic devices. These devices pack a huge amount of functionality into a limited space. The multi-layer structure enables complex circuits to be realized in a compact housing.

Production of multilayer boards is complex and costly. In the laminating process, each layer must be perfectly aligned. If there is a dislocation, it will cause connection failure. This process requires dedicated equipment and skilled technicians.

Rigid Board

Rigid boards cannot bend or flex. Substrate material (usually FR-4 fiberglass) provides solid mechanical support. Most printed circuit boards are rigid circuit boards because they are the easiest to manufacture and handle.

Rigid boards are suitable for applications that do not require the movement of the board. Rigid boards are commonly used in desktop computers, TVs, and industrial devices. Rigid boards protect components from mechanical stress.

Due to its high cost and reliability, rigid boards are widely used. The manufacturing process is established, and stable quality is obtained. Rigid PCB boards can withstand more weight than the weight supported by flexible boards.

Flexible Printed Circuit Boards

Flexible printed circuit boards use polyimide and similar materials that do not break even when bending. These boards are suitable for curved surfaces and moving parts. This flexibility enables unique product designs that cannot be realized on rigid boards.

Flexible boards are often used for wearable devices, foldable smartphones, and camera modules. Flexible circuits that fit the contours of the body are also used for medical implants. These boards can be bent, twisted or winded according to design requirements.

The production cost of flexible printed circuit boards is higher than rigid circuit boards. Special materials and manufacturing processes increase production costs. However, the high degree of freedom of design justifies the cost increase in many applications.

PCB Materials Explained

Substrate Materials

The substrate is the physical foundation of the board. FR-4 (fiberglass epoxy) is the most common substrate material. It has excellent electrical insulation, mechanical strength and heat resistance at an affordable cost.

Other substrate materials include polyimide for flexible boards, aluminum for LED applications, and rogers for high frequency circuits. Each material has different properties, affecting performance, cost and application.

Heat resistance temperature is an important factor when selecting substrate materials. The FR-4 can accommodate temperatures from 130 to 140 °C. In high temperature applications, polyimide and ceramic boards that can withstand higher heat without deterioration are required.

Copper Layer

Copper forms a conductive path on a printed circuit board. The copper layer consists of a thin foil laminated on the substrate. Standard copper thickness is one ounce per square foot, which is equivalent to about 35 micrometers.

Thicker copper (2 or 3 ounces) can flow large currents without overheating. Power boards and motor controllers often require thick copper. As a price, the thicker the copper, the higher the cost, the more difficult the etching to fine wiring.

The quality of copper affects the reliability of the substrate. High purity copper has good conductivity and low resistance value. Impurities in copper can cause signal failure in highly sensitive circuits.

Solder Mask and Silk Screen

Solder masks are colored coating layers on the PCB, usually green, but red, blue, black, or white are also available. This protection layer prevents solder bridges between adjacent copper traces when mounting. It also protects copper from oxidation and physical damage.

Silk screen layer is a layer that prints part labels, test points and other markings on the board. The standard is white ink, but other colors can be used depending on the color of the solder mask. Clear labeling is useful for assembly and troubleshooting.

High quality solder mask application prevents manufacturing defects. Insufficient masking can spread to places where solders should not be, causing short circuits. The mask must adhere tightly and not peel off during use.

PCB Design Process

PCB Design Software

PCB design software converts schematics into board layouts that can be manufactured. Typical tools include Altium Designer, Eagle, KiCad, and EasyEDA. Each program has different functions and pricing systems.

Professional engineers prefer Altium for complex designs. This software supports high-speed signal, multi-layer wiring, and design rule checking. However, the price of Altium is so expensive that it is untouchable for people who work with hobbies.

KiCad offers professional features for free. Many startups and makers choose KiCad to reduce development costs. The difficulty of learning is higher than simple tools, but their features are comparable to expensive commercial software.

PCB Board Design Software Tool

PCB board design software includes more than basic layout functions. The Design Rule Check function confirms that the layout meets the manufacturing requirements. This software points out interval violations, trace width errors, and other problems before production.

3D visualization helps identify mechanical interference. You can check how the parts are combined and check the clearance. This prevents assembly problems that require expensive rework.

Automatic wiring function helps with initial part placement. However, in the case of complex boards, manual wiring usually results better. Automatic wiring tools are useful for simple layouts, but they are difficult to handle with high-speed signals and high-density designs.

PCB Manufacturing Process

Copper Etching

Manufacturing starts with copper-clad laminate substrate with copper foil on one or both sides. Photoresist coating covers the copper. UV light exposes the resist through a film showing the desired circuit pattern.

The developer solution removes unexposed resist, leaving copper covered only where traces should remain. The etching solution then dissolves exposed copper. The protected areas stay intact, forming the circuit traces.

Etchant chemistry affects quality and speed. Ferric chloride is common for small-scale production. Ammonium persulfate works faster for industrial manufacturing. The process requires careful control to avoid over-etching or under-etching.

Electroplating (Titanium Anode Role)

Electroplating is a process in which copper is attached to a through hole to increase the thickness of the wiring. PCB acts as the cathode. Titanium anodes serve as the anode (positive electrode). When the current flows, the copper ions from the plating solution deposit onto the board.

Titanium anodes perform better than other electrode materials in PCB plating. Titanium anodes are resistant to corrosion caused by acidic plating solutions that destroy steel and copper anodes. This corrosion resistance increases service life and reduces replacement costs.

High-quality titanium anode manufacturers such as Ti-Better manufacture anode specially designed for plating electronics. These anodes provide a uniform current distribution throughout the plating tank. This uniformity ensures uniform copper thickness throughout the printed circuit board.

Titanium anode coating affects plating performance. Platinum coating and mixed metal oxide coating optimize current efficiency. Poor quality anodes cause unevenness of plating, resulting in time and waste of material. Plating results are directly dependent on the quality of the anode.

Drilling and Assembly

Computer-controlled drills make holes for through-hole parts and via. A very small drill bit of 0.1mm forms a fine connection. Precision is important, and the substrate becomes unusable when the hole is shifted.

After drilling, the hole is plated to connect between layers. After that, the solder mask is applied and silk screen printing is done, and the substrate is completed. The finished board is sent to the assembly process.

In the PCB assembly process, parts are placed on the board and soldered. The pick and place machine places surface mounting parts at high speed. Melt the solder paste in the reflow furnace to permanently fix the parts. Through-hole parts may require hand soldering or wave soldering.

Circuit Board Components

Circuit board components include both active and passive components. Active components such as transistors, microcontrollers, and ICs perform signal processing. On the other hand, passive components such as resistors, capacitors, inductors, etc. perform signal and power adjustments.

The resistor limits the current in the circuit. Resistors have various resistance values and allowable currents. Resistance values are indicated in color bands and numerical codes. Surface-mounted resistors are very small and some are less than 1 mm long.

Capacitors store electrical charge temporarily. The capacitor smoothes the supply voltage, combines signals between each stage, and filters noise. Applications vary depending on the type of capacitor. For high frequency, ceramic capacitors and electrolytic capacitors are used for power supply filtering.

Integrated circuits (ICs) are integrated into small packages of thousands to millions of transistors. The microcontroller performs a program that controls the behavior of the device. Memory chips store data and instructions. Special ICs handle specific functions such as power management and wireless communication.

The connector connects the PCB to the external device. This includes USB ports, power jacks, button switches, and display connectors. Choosing the right connector affects reliability and user experience.

Key Factors When Choosing Printed Circuit Board Manufacturers

Manufacturing Capabilities

Each PCB manufacturer has different facilities and manufacturing capabilities. Check whether you can manufacture your board type. Not all factories support flexible or multilayer boards. Different manufacturers have different trace and spacing requirements.

Please also check the limit of the number of layers. Some manufacturers only handle simple boards, while others can produce more than 20 layers of boards. The complexity of the design determines which manufacturer can manufacture.

The choice of surface treatment affects the soldering of parts and the durability of the substrate. HASL (hot air solder leveling) is inexpensive, but the accuracy is low. ENIG (electroless nickel/immersion gold) is expensive, but provides a flat pad that is ideal for fine pitch parts.

Quality Certifications

Make sure you have at least ISO 9001 certification. This indicates that the manufacturer complies with the quality control system. The IPC standard (IPC-A-600, IPC-6012) defines the acceptable quality level of the substrate.

UL certification is important for products sold in North America. CE marks are required in the European market. The certification required by the manufacturer varies depending on the target market.

Check the manufacturer’s test procedure. Electrical tests detect short circuits and breaks. X-ray inspection inspects internal layers and via. The flying probe test ensures that all connections are functioning correctly.

Lead Time and Price

The standard lead time of the prototype is 1-3 weeks. The urgent service will be delivered in a few days, although additional charges will be charged. Large quantities of mass-produced products require a longer lead time.

The price of PCB boards depends on size, number of layers, quantity and specification. A simple single-sided substrate is less than $1 per piece for large orders. Complicated multilayer boards may cost more than $50 to $100 per piece even if they are mass-produced.

Get quotes from multiple PCB manufacturers and compare prices. The cheapest option is not always the best. Consider cost, quality and service in a balanced manner. Poor quality boards cause expensive problems during assembly and product testing.

Applications of PCBs

LED Printed Circuit Boards

Printed circuit boards for LEDs have special requirements. The aluminum substrate efficiently dissipates heat from higher output LEDs than FR-4. Metal core conducts heat away from LEDs to prevent overheating and extend the life of LEDs.

LED printed circuit boards are used for lighting products such as light bulbs, strips, and lighting fixtures. These boards may have drivers that control the current of the LEDs. Thermal management design is extremely important. The LEDs will fail as soon as they overheat.

For LED applications, the white solder mask reflects light. This improves brightness compared to conventional green boards. Some manufacturers offer special materials optimized for the thermal performance of LEDs.

Consumer Electronics

Smartphones, tablets and laptops all rely on complex multi-layer printed circuit boards (PCBs). These devices pack a huge amount of functionality into a limited space. High density wiring (HDI) technology enables the realization of fine wiring and via required.

Mobile phone boards include RF sections for wireless communication, power management circuits, processor circuits, etc. Multiple dedicated chips are connected via a printed circuit board. With the advancement of miniaturization, PCB technology continues to evolve into a finer structure.

Wearable devices like smartwatches require flexible printed circuit boards to fit the curved case. This flexibility enables designs that are not possible with rigid boards. Battery life depends in part on an efficient PCB layout that minimizes power consumption.

Automotive and Industrial

Modern automobiles are equipped with dozens of PCBs that control engine, safety, entertainment and navigation systems. Automotive boards must withstand vibration, extreme temperature and electrical noise. Conformal coating protects the substrate from moisture and pollution.

In industrial equipment, rigid PCB boards are used in harsh environments. Both motor controllers, automated systems, and sensors require reliable circuit boards. Industrial applications may require components and robust structures for a wide range of temperatures.

Strict regulatory requirements are imposed on PCB manufacturing of medical devices. Traceability documents prove that all PCBs meet the specifications. Clean room assembly prevents contamination of equipment that is embedded in the body.

Common PCB Design Mistakes to Avoid

Inadequate Spacing

Insufficient spacing between wires causes manufacturing problems. If the wiring is too close, a short circuit may occur in the etching process. Depending on the type of printed circuit board, the required minimum interval requirements vary depending on the voltage and current.

Before finalizing the layout, check the manufacturer’s design rules. If a manufacturer has no problem, another manufacturer may fail. In order to prevent defective products, please have room for important intervals.

High voltage circuits require wider spacing to prevent arc discharge. In particular, it is necessary to pay close attention to the power supply. Solder masks have some insulation effect, but are insufficient as the only barrier.

Poor Component Placement

Disorderly placement of parts makes assembly difficult and costs increase. Logically place the relevant parts together. Automatic assembly can be simplified by pointing the parts in the same direction as possible.

Please ensure space for assembly equipment around large parts. Pick-and-place machines require room to place parts. If the interval is too narrow, it may require costly manual assembly rather than automatic process.

Consider heat problems when placing. Do not compact heating parts. In order to properly manage the heat, disperse the heat generation parts throughout the board and place them.

Ignore Feedback From Manufacturers

Many PCB manufacturers offer design review services. Use this feedback to discover problems before manufacturing. Factory engineers understand the limitations of their equipment better than you.

Common problems include drill sizes that don’t match available bits, impossible via structures, or structures that cannot be processed in manufacturing facilities. You can save time and money by fixing these issues early.

Test points help troubleshoot, but many designs have forgotten their placement. Add test points for critical signals at the design stage. It costs very little, but it saves a lot of time when debugging.

Conclusion

Printed circuit boards play a role in connecting electronic components in almost all modern electronic devices. Understanding PCB types, materials and manufacturing processes can help you design better products and select reliable PCB manufacturers. By choosing the right PCB from simple single-sided boards to complex multi-layer boards, you can succeed in electronic equipment projects and increase cost efficiency.

FAQ’s

1. What are the main types of printed circuit boards?

The main types of PCBs include single-sided, double-sided, multilayer, rigid and flexible boards. The single-sided substrate is copper foil only on one side, and the double-sided substrate uses both sides. Multilayer boards are layered with multiple layers, the rigid substrate cannot be bent, and flexible boards conform to curved spaces.

2. What is the manufacturing cost of PCB?

The price of PCB is about 5-50 dollars on a prototype substrate, but the unit price will decrease when mass production. Complex multilayer boards become more expensive. Size, number of layers, surface finish and quantity affect the final price from the PCB manufacturer.

3. Which software should I use for PCB design?

Common PCB design software include Altium Designer (for professionals), Eagle (for intermediate users), and KiCad (for free). The choice of PCB design software depends on the complexity and budget of the design. Beginners can start with EasyEDA, and professionals tend to prefer the advanced features of Altium.

4. Why is titanium anode used in PCB manufacturing?

Titanium anode is resistant to corrosion caused by acid plating in PCB production. In addition, the current is distributed evenly to achieve uniform copper plating. Titanium products provided by manufacturers such as Ti-Better have a long life and reduce replacement costs.

5. What is the difference between rigid PCB and flexible PCB?

Rigid PCB substrate uses hard FR-4 fiberglass and cannot be bent. A  flexible printed circuit board uses polyimide which can be bent repeatedly. In most cases, the cost of rigid boards is cheaper. Flexible boards are suitable for wearable devices, foldable electronics, and moving parts.

6. How should I choose a PCB manufacturer?

Make sure your manufacturing capacity meets your design requirements. Check if you have ISO 9001 and IPC certification. Compare delivery time and price from multiple PCB manufacturers. Please read the review before production and request a sample board.

7. What are some common PCB parts?

Circuit board components include resistors, capacitors, inductors, diodes, transistors, ICs, and connectors. The resistor limits the current, the capacitor filters the signal, the IC performs the processing, and the connector connects with the external device. Selection depends on circuit requirements.