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How to Make PCB Boards
PCB (printed circuit board) is an indispensable part of electronic products, and its manufacturing process is complex and delicate. Let’s explore the entire manufacturing process of PCB boards from raw materials to finished products.
1. Selection and preparation of PCB board materials
The main materials of printed circuit boards include copper-clad laminate, copper foil, gold plating/tin plating layer, solder resist ink, etc. Copper-clad laminates are usually made of glass fiber-reinforced epoxy resin or special composite materials containing polyimide, which have excellent insulation, mechanical strength and heat resistance. Copper foil is a high-purity copper material used to make conductive lines on PCBs. Gold plating or tin plating can improve the corrosion resistance and welding performance of PCBs. Solder mask ink is used to cover unused areas on the PCB to provide insulation protection.
Before using these materials to make PCBs, they need to be rigorously cleaned and inspected to ensure that the material quality meets the requirements. The copper-clad laminate needs to have surface stains removed, and the copper foil needs to have its surface cleaned to ensure good adhesion. At the same time, the size, thickness, flatness and other parameters of the material also need to be measured and calibrated.
2. PCB board design and drawing
The design of PCBs is usually completed by electronic engineers. They design the PCB layout based on the circuit schematic diagram and determine the location and wiring path of each component. In order to improve manufacturing efficiency and product quality, PCB design needs to follow some basic principles, such as wiring density, trace width, component layout, etc.
After the design is completed, the PCB layout drawing needs to be converted into CAD files for manufacturing, including front view, back view, drilling drawing, etc. These files provide a reference for subsequent exposure, etching, drilling and other processes.
3. Exposure and etching of PCB board
Once you have the CAD file, you can start the printed circuit board manufacturing process. The first is the exposure process of the copper-clad laminate. The copper-clad board is coated with photosensitive resin, and then a photolithography machine is used to expose the CAD pattern onto the resin layer. After exposure, a chemical reaction occurs in the resin layer to form a latent image.
Next comes the chemical etching process. Soak the exposed copper-clad board in the corrosive solution, and the unexposed resin layer will be dissolved, exposing the underlying copper layer. After precisely controlling the etching time, the expected wiring pattern can be obtained.
After etching, the PCB board needs to be thoroughly cleaned to remove residual corrosive liquid and resin. This step is called film removal, which ensures that the PCB surface is clean and flat.
4. Drilling of PCB board
The printed circuit board needs to have holes at specific locations for subsequent installation of components and connecting wires. This step is called the drilling process. First, you need to make a drilling template according to the CAD drawing, and then use a CNC drilling machine or laser drilling machine to accurately drill holes on the PCB board.
Holes of different sizes require drill bits of different diameters. For small hole diameters, special chamfering treatment is also required to improve welding quality. After drilling is completed, there will be a large amount of metal shavings and burrs on the surface of the PCB board, which requires vacuuming and deburring.
5. Tin plating and gold plating of printed circuit boards
To improve the welding performance and corrosion resistance of the PCB, a layer of tin or metal needs to be plated on the surface of the PCB. This process is called tin plating or gold plating.
The tin plating process includes three steps: pickling, electroplating, and hot melting. First, use acid to remove the oxide layer on the PCB surface, then perform electroplating in an electroplating tank, and finally solidify and fuse the electroplated tin layer in a hot melting furnace.
The gold plating process is to first electroplat a layer of nickel on the surface of the PCB as an intermediate layer for adsorbing the gold layer, and then electroplat a layer of gold. The purpose of gold plating is to improve the conductivity, weldability and oxidation resistance of PCB.
6. Solder mask printing on PCB board
On the surface of the manufactured printed circuit board, a layer of solder mask ink needs to be printed. Solder mask ink can cover unused areas on the PCB, providing insulation protection and beautifying the appearance of the PCB.
The solder mask printing process usually uses screen printing. First, a layer of photosensitive solder mask ink is coated on the PCB surface, and then a metal screen is used for pattern transfer. After printing is completed, it needs to be cured in a hot air oven.
7. PCB board testing and packaging
PCB boards manufactured through the aforementioned process require comprehensive quality inspection. Mainly includes appearance inspection, dimensional measurement, electrical performance testing, etc. Only qualified PCB boards can enter the subsequent assembly and packaging process.
In terms of packaging, printed circuit boards need to take corresponding protective measures according to different transportation environments and storage conditions, such as anti-static packaging, moisture-proof packaging, etc. After packaging is completed, the PCB board can be shipped to downstream electronic product manufacturers.
In short, the manufacturing process of PCB boards is a complex and delicate process that requires multiple key steps such as material preparation, design and drawing, exposure etching, drilling plating, solder mask printing, and test packaging. Only by strictly controlling every link can the quality and performance of printed circuit boards be ensured. As electronic products continue to be updated, PCB manufacturing technology is also constantly improving and optimizing, providing a solid foundation for the development of the electronics industry.