If you disassemble several electronic devices, you will discover a printed circuit board (PCB), which is a small green board with maze-like markings.So what is a PCB? These small green boards aid in the operation of electronic devices. The device would not function without them. PCBs connect all of the other components inside, allowing you to use your electronic device for its intended purpose.Despite its small size, the PCB manufacturing process is quite extensive. Whether you make your own or use a PCB manufacturer, multiple steps are required for the board's development. Because each step is critical to the overall process, let's take a closer look at the 4-layer PCB production flow. The production flow of a 4-layer PCB Catalog I Parts of printed circuit boards1.1 Features of printed circuit boards1.2 The role of printed circuit boardII PCB manufacturing processFAQ I Parts of printed circuit boards To have a thorough understanding of Printed Circuit Boards (PCBs), it is important to know the various parts that are used to make the boards.The most obvious starting point is the board itself. It is plastic, reinforced with glass. The next most obvious parts are the lines and pads that connect together. These are made of copper, and are known as ‘traces’. They conduct electricity, allowing electrical charges to be carried through the board. They are similar to wires, but are much finer, and are used to carry the electricity to the end-point (one of the various types of components within the board).  Figure 1. Essential parts of a printed circuit board Simple PCBs are single-sided, with one copper layer. These are structured with one side having all the components, while the other side had the traces. Holes are placed through the board for the circuit to be carried from the trace to the component. For many years, all boards were made in a single-sided design. By definition, double sided PCBs have traces on both sides of the board.To allow the boards to be more complex and control additional functions, multi-layer boards are used. Additional layers of board have their own set of traces and components. In developing multi-layer boards, a range of issues needed to be addressed. Firstly, it is essential that the copper connections do not cross each other, as this would compromise the path of the electrical circuit. Other factors that need to be considered are resonance and noise and capacitance.The layer set in place above the copper is called the soldermask. This is a form of insulation, ensuring that the copper traces aren’t affected by any metal that may come into contact with it. It is traditionally colored green. It is designed to have gaps that expose the copper in specific places, providing points where components can be soldered to the board. The silkscreen is a layer that is printed onto the soldermask. It is a layer where text can be printed (letters and numbers) that provide instructions for the user.A range of components can be incorporated into a PCB. Without components, the PCB is simply a conductor of electricity, with no function. Components can be grouped into two broad categories – passive (components that do not require direction) and active (components that only function when they receive current from one direction). Common components include:1. Batteries: these provide the circuit with voltage.2. Capacitators: The store electricity for later use. They are available as polarized or non-polarized.3. Diodes: allows current to pass in one direction only, blocking the other.4. Inductor: These coils store charge in a magnetic field.5. Light emitting diodes (LEDs). These light up when current flows is applied. They only allow current to flow in one direction.6. Resistors: These control the electric current as it passes through. The level of resistance provided varies based on the needs of the engineer. 7. They are made in different color codes to show the level of resistance.8. Switches: These can be open or closed, allowingor blocking current.9. Transistors: These are a form of switch that performs changes function based on the voltage passing through.10. Vias: small holes in the board that allow a signal to be passed from one side to the other 1.1 Features of printed circuit boards1. After the electronic component is encapsulated, the electrical conduction can be realized.2. It is required that there should be no current flow in the insulating part.　3. It is required that there must be current flow in the conduction part.　4. As the mechanical support for the fixation and assembly of components, it must meet the requirements of mounting components.5. There must be complete and clear recognition characters and component symbols.6. It can be fixed to the appropriate part of the machine. 1.2 The role of printed circuit boardAfter the printed circuit board is adopted in the electronic equipment, the error of manual wiring is avoided because of the consistency of the same kind of printed circuit board. And the automatic insertion or mounting, automatic soldering and automatic detection of electronic components can be realized. In a word, it ensures the quality of electronic equipment, improves the labor productivity, reduces the cost, and is convenient for maintenance.Figure 2. Printed circuit board II PCB manufacturing process Now, let's take four layers as an example to see how printed circuit boards are made.  Figure 3. Chemical clean Step 1: In order to obtain an etching pattern with good quality, it is necessary to make sure that the corrosion resistance layer is firmly combined with the substrate surface, and the substrate surface is required to be free of oxidation layer, oil pollution, dust, fingerprint and other dirt. Therefore, before coating the corrosion resistant layer, it is necessary to clean the surface of the board and make the surface of the copper foil reach a certain degree of coarsening. Core material: when you start making four layers, the inner layer (the second and the third layer) must be done first. The core material is a copper sheet composed of glass fiber and epoxy resin on the upper and lower surfaces.   Figure 4. Cut sheet →dry film lamination Step 2: In order to make the shape we need on the core material, we first paste a dry film (photoresist) on the core material. The dry film is composed of polyester film, photoinduced corrosion resistant film and polyethylene protective film. When sticking the film, the polyethylene protective film is stripped from the dry film, and then the dry film is pasted on the copper surface under the condition of heating and pressurization.  Figure 5.  Image expose→image develop Step 3: Under the irradiation of ultraviolet light, the photoinitiator absorbs the luminous energy to decompose into free groups, which in turn initiate the polymerization and crosslinking of photopolymerizable monomer. After the reaction, a high molecular structure insoluble in dilute alkali solution is formed. The polymerization reaction will continue for a period of time. In order to ensure the stability of the process, the polyester film should not be torn off immediately after exposure. It should stay for more than 15 minutes, so that the polymerization reaction can continue and the polyester film should be torn off before development. Image Develop: the active group in the unexposed part of the photosensitive film reacts with dilute alkali solution to produce a soluble substance and then it dissolves, leaving a graphic part that has been photosensitive crosslinked and solidified.  Figure 6.  Copper etch Step 4: In the production of flexible printed circuit board or printed circuit board, the copper foil is removed by chemical reaction to form the required loop pattern. The copper beneath the photoresist is preserved from etching.   Figure 7. Strip resist→post etch punch→AOI inspection→oxide Step 5: The purpose of removing the film is to remove the corrosion resistant layer retained on the surface of the etched board so that the copper foil below can be exposed. "Membrane slag" filtration and waste liquid recovery should be properly treated. If the water washing after the film removing can completely cleans the board, you can consider not doing pickling. Finally, the board should be completely dry after cleaning.   Figure 8. Lay-up with prepreg Step 6: Before entering the press machine, it is necessary to prepare the raw materials for each multilayer board for lay-up operation. In addition to the oxidized inner layer, the prepreg is also needed. The function of the lamination is to stack the boards covered with protective film in a certain order and place them between the two-layers of steel plate.  Figure 9.  Lay up with copper foil→vacuum lamination press  Step 7: Cover the current core material with a layer of copper foil on both sides, and then cool to room temperature after multi-layer pressurization, which requires temperature and pressure to be measured over a fixed period of time. And a multilayer sheet is finished.   Figure 10.  CNC drill Step 8: Under the accurate condition of inner layer, the CNC drilling machine drills according to the mode. Drilling accuracy is required to ensure that the hole is in the correct position.    Figure 11. Electroless copper Step 9: In order for the through hole to be conductive between the layers ,which means the resin and glass fiber bundles of the non-conductor part of the hole wall should be metalized), copper must be filled in the hole. The first step is to coat the hole with a thin layer of copper, which is a complete chemical reaction. The final copper plating is 1/1000000 of 50 inches thick.   Figure 12. Cut sheet→dry film lamination Step 10: Photoresist: this time we apply photoresist to the outer layer.   Figure 13. Image expose→image develop Step 11:This time we finish the outer exposure and development.   Figure 14. Copper pattern electro plating Step 12:This also becomes the secondary copper plating, the main purpose is to thicken the line copper and the through-hole copper.  Step 13:Its main purpose is to prevent etching and to protect the copper conductors covered by it from attacking during alkaline copper etching. The copper conductors include all the copper lines and the through holes interior.   Figure 15. Strip resist Step 14:We already know the purpose. All we have to do is to make the copper on the surface exposed by using chemical methods.   Figure 16.  Copper etch Step 15:We also know the purpose of etching. And the tinned part protects the copper foil below.   Figure 17. Tack dry→image expose→image develop→thermal cure solder mask Step 16:The welding resistance layer is used to expose the welding pad, that is, the green oil layer, which is actually digging holes in the green oil layer and exposing the welding pad and other places that do not need to be covered with green oil. Suitable surface features can be obtained by proper cleaning.  Figure 18. Surface finish Step 17:The process of hot air leveling solder coating (commonly known as tin spray) is to soak the printed circuit board with flux, then dip it in the molten solder. Next, pass it between the two wind knives and blow off the excess solder on the printed board with the hot compressed air in the wind knives. At the same time, the excess solder in the metal hole is eliminated, so as to obtain a bright, smooth and uniform solder coating.Gold finger (Gold Finger, or Edge Connector) is designed to use the connector insertion as an outlet for external contact with the board, so the gold finger process is required. Gold was chosen because of its superior conductivity and oxidation resistance. But because of the high cost of gold, it can only be used for gold fingers, local plating or electroless gold. FAQ 1. What is a PCB in a printer?While design of a printed circuit board (PCB) can be done internally, manufacturing is generally outsourced. This dependence often results in uncontrollable, and unexpected delays. ... It is here that desktop PCB printers are aiming to come to the rescue. 2. How much does it cost to print a PCB?In general, the cost to produce a PCB will cost between $10 and $50 per board. 3. How does a PCB printer work?A special printer called a plotted printer is used to print the design of the PCB. It produces a film that shows the details and layers of the board. When printed, there will be two ink colors used on the inside layer of the board: Clear Ink to show the non-conductive areas. 4.Why are PCB green?It is due to the solder mask, which protects the copper circuits printed on the fibre glass core to prevent short circuits, soldering errors, etc. ... The colour of the solder mask gives the board its appearance. 5. How much does custom PCB cost?At BatchPCB, a two-layer board costs $2.50 per square inch (about $0.40 per square centimeter), while a four-layer board costs $8 for the same area (about $1.24/cm2). The first step in creating a custom PCB is laying out the schematic view. 6. How do I print directly from PCB?A laser printer is used to print an image of the PCB on special “transfer paper” which is then placed on the bare copperclad board and either ironed or run through a modified laminator to transfer the image to the copper. 7. What does PCB stand for?printed circuit board. A printed circuit board, or PC board, or PCB, is a non-conductive material with conductive lines printed or etched. Electronic components are mounted on the board and the traces connect the components together to form a working circuit or assembly. 8. What is PCB made of?copper circuitry. Printed circuit boards (PCBs) are usually a flat laminated composite made from non-conductive substrate materials with layers of copper circuitry buried internally or on the external surfaces. They can be as simple as one or two layers of copper, or in high density applications they can have fifty layers or more. 9. Which type of PCB is more economical type?Aluminum-Backed PCBs. Aluminum is inexpensive, making almost 8.23% of planet's weight, and leads to most economical manufacturing process. PCBs made up of aluminum are easily recyclable and non-toxic in nature, making them as ideal source for energy conservation. 10. How do you choose a PCB material?Electrical functionality is based on PCB function, which makes it a good criterion for design-based circuit board material selection. According to function, PCBs may be classified as the following board types: High Frequency (High Speed) – These boards can accommodate frequencies in the 500MHz – 2GHz range.