PCB (Printed Circuit Board) is an indispensable component of modern electronic products.
There are many types of PCBs, including single-layer boards, double-layer boards, and multi-layer boards. PCB multilayer board is a printed circuit board with multiple electrical layers, which plays an important role in modern electronic equipment. This article will introduce PCB multi-layer boards in detail and compare them with single-layer and double-layer PCBs to better understand their differences and advantages.
PCB multilayer boards are composed of multiple layers of conductive materials separated by insulating layers, usually made of epoxy resin or fiberglass. These layers are bonded together using heat and pressure to create a strong structure.
PCB multilayer boards are composed of at least three electrical layers, and the layers are connected by pre-designed copper foil layers. These layers are stacked together to form a whole, and the layers are electrically connected through vias. The number of layers in a multilayer board varies according to the complexity of the circuit design, which not only provides a larger layout space but also enables more complex circuit designs without increasing the size of the board.
Multilayer PCBs contain at least three or more layers, while double-layer PCBs have two layers, a top layer and a bottom layer.
Multilayer PCBs are typically used for more complex circuits that require higher performance and capacity;
Double-layer PCBs are usually used for relatively simple circuit boards.
Multilayer PCBs are generally more expensive than double-layer PCBs because multilayer PCBs require more manufacturing steps and materials.
Multilayer PCBs usually use a stacked structure with internal layers, while double-layer PCBs have no internal layers.
In summary, while single- and double-layer PCBs function in simpler applications using fewer components, PCB multilayer boards offer greater functionality in a limited space while enhancing signal integrity and thermal management capabilities. Their versatility and performance make them the first choice for advanced electronic devices and systems.
The most obvious difference is the number of layers between multilayer boards and single-layer PCBs. Single-layer PCBs have only one conductive layer, while multi-layer boards contain multiple layers.
On a single-layer PCB, all wires and electronic components are on the same side.
On multilayer boards, wires can be distributed on different levels, which helps increase circuit complexity and density.
Single-layer PCBs often use jumpers or soldering to connect different electronic components.
Multilayer PCBs allow for more complex connections via vias or blind holes between internal layers, reducing the need for external connections.
Multilayer PCBs often offer higher performance and circuit capacity because they allow more wires and components to run in a smaller space.
The manufacturing process of PCB multilayer boards involves several complex steps to ensure their quality and functionality. Let’s dive into the detailed instructions of this process.
PCB manufacturing begins with the step of cutting a large motherboard into appropriate sizes, usually using a drill press or CNC machine.
A precision drilling machine creates holes or vias in all layers of a circuit board at designated locations, usually using a CNC drill press. These holes will be used to connect different levels of circuitry for component mounting and interconnection purposes.
After drilling, a thin layer of copper is deposited onto the hole wall of each drilled hole using a chemical deposition process called "through-hole plating". The inner and outer layers are coated with copper through chemical deposition or electroplating. This step ensures that the different layers correct electrical connections.
Cover the copper layer with a photosensitive film for subsequent etching steps. This film is used to define circuit patterns.
Chemical methods are used to etch away unnecessary copper, leaving only the desired circuit pattern. The photosensitive film acts as a protective layer.
Automated optical inspection is performed to ensure there are no manufacturing defects on the circuit board.
Scan multi-layer circuit boards to check their quality and integrity.
By immersing in a chemical solution, the surface is coated with a protective oxide layer to protect the copper layer from oxidation and corrosion.
Multilayer boards usually consist of multiple inner and outer layers. In this step, the inner layer is fabricated, similar to the process for the outer layer.
The inner and outer layers are bonded together using heat and pressure to form a multi-layer PCB
Chemical washing is performed to remove unwanted residual materials to ensure the quality and reliability of multilayer boards.
Apply a protective coating to protect the board surface from environmental factors.
Remove the remaining photosensitive film to prepare for subsequent processes.
Drill holes for positioning and mounting of circuit boards.
Apply solder mask material to create solder pads on the circuit pattern for mounting electronic components.
Add logos, text, and logos to identify the board.
Carry out further drilling to prepare the mounting elements.
Conduct a circuit continuity test to ensure there are no open or short circuit issues. To ensure the functionality of the PCB, various tests such as electrical connection testing, impedance measurement, and signal integrity analysis are required. Any defects or faults are identified and corrected at this stage.
After the PCB passes all tests, electronic components such as resistors, capacitors, integrated circuits, etc. will be welded to the designated positions using automatic placement machines or manual assembly methods.
The exposed copper surface is coated with protective paint to prevent oxidation and facilitate soldering during component assembly. Common surface treatments include HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel Immersion Gold), and OSP (Organic Solderability Preservative).
After the PCB passes all tests, electronic components such as resistors, capacitors, integrated circuits, etc. will be soldered to designated locations using automatic placement machines or manual assembly methods.
The assembled PCB undergoes comprehensive functional testing to verify its performance under real-world conditions. This includes power-on testing, functional verification, and sometimes environmental stress testing.
After successful testing, the PCB multilayer board is carefully packed to protect it during transportation and delivered to the manufacturer or end user for integration into electronic devices.
PCB multilayer board manufacturing process is a complex and diverse process, which is widely used in various industries in the electronic field, such as communications, medical equipment, computers, etc. A successful multilayer PCB project starts with a good design. The design process should follow best practices to ensure circuit performance and reliability. PCB multilayer board technology continues to develop, and future trends include smaller size, higher performance, more environmentally friendly materials and smarter manufacturing processes.
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