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Some people who are new to the electronics manufacturing industry may not be very clear about PCB and PCBA, and may also confuse the two. In order to let everyone quickly identified them and reduce unnecessary troubles, LHD PCB will introduce the difference and characteristics of PCB and PCBA.
First, the PCB
PCB can be called circuit board, PCB board, circuit board, high frequency board, thick copper board, impedance board, multi-layer circuit board, multi-layer PCB, ultra-thin circuit board, ultra-thin circuit board, printing (copper etching technology) circuit Boards, etc., are important electronic components used to support electronic components and to connect electronic components.
PCBA is the abbreviation of PrintedCirruitBoardAssembly in English. In foreign countries, PCBA is generally translated into PCBAssembly. The PCB blank board is processed by SMT patch, DIP plug-in and test to form a finished product, referred to as PCBA.
The difference between them is that the PCB is an empty board (referred to as bare board), and there is nothing on the surface of the board; while PCBA is processed on an empty PCB, and components such as resistors, capacitors, chips, etc. are formed to form a certain function. The board, the core part of all electronic products, is a finished board composed of PCBA.
Why can't PCB board be touched with finger? What are the serious consequences of direct hand contact with the circuit board? In fact, it will cause bad scrap of PCB and reduce the reliability of end users, but in the working process, it is inevitable to touch PCB directly with your hands, so to develop the habit of wearing gloves, which can reduce the harm of direct contact to PCB. Here's a look at how finger prints can lead to PCB defects, hazards, and how to avoid them.
1. Finger marks: finger marks are hand sweat stains, which are mainly composed of water, inorganic salts, fats, oils, cosmetics, skin care products and other pollutants.
2. Hazards of finger printing in PCB manufacturing process:
A. bare hand contact plate before resistance welding will lead to resistance welding, leading to poor adhesion of green oil, which will blister and fall off during hot air;
B. during the process from resistance welding to packaging, bare hand touching the board surface of the circuit board will lead to the board surface of the circuit board is not clean, resulting in poor weld ability or poor bonding;
C. When the bare material touches the circuit board, the copper on the board will undergo chemical reaction in a very short time, leading to the oxidation of the copper surface. After a little longer time in electroplating after obvious fingerprints, uneven coating, causing serious defects in the appearance of the product;
D. wet film or silk screen printing line and the plate surface before pressing film with fingerprint grease, easy to cause the adhesion of dry/wet film to decline, in electroplating lead to infiltration plating and coating separation, gold plate is easy to cause surface pattern, after the completion of resistance welding production, the plate surface oxidation, appear Yin and Yang color.
PCB boards are also becoming an indispensable accessory for electronic devices. Let's take a look at the features of PCB boards.
First, high density, light weight and high flexibility
The PCB circuit board is made of a flexible substrate such as a high-quality polyester film. It not only has the characteristics of high wiring density and light weight, but also has the advantages of high flexibility, and can be moved and stretched according to the requirements of the space layout. to achieve the assembly of the PCB circuit board.
Second, the installation is simple and consistent
The PCB board not only has the characteristics of light weight and space-saving under the same current carrying capacity, but also has outstanding features of uniformity.
Third, the electrical parameter design can be controlled
The parameter design of the capacitance and inductance parameters, characteristic impedance and attenuation of the PCB circuit board are all controllable, which also makes it convenient for practical application of various electronic devices, and the design of the cost-effective PCB circuit board structure is simplified. The use of related clips and fixtures is reduced, which ensures a low production cost of the PCB board to a certain extent.
It can be known from above. The PCB board is not only lightweight and thin, but also has certain advantages in terms of flexibility and flexibility. The short heat dissipation path of the PCB board allows it to have good heat dissipation performance.
PCB Power Layer Cabling Design One of the keys to high-speed power PCB board is to minimize the noise introduced by the voltage drop caused by line impedance and high-frequency electromagnetic field conversion. There are usually two ways to solve the above problem. One is the power bus technology (POWER BUS), and the other is a separate power plane for power.
1. The AC input and DC output should have a clear layout distinction. The best way is to be able to isolate each other.
2. The input and output (including DC/DC conversion primary and secondary) wiring distance should be at least 5 mm.
3. The control circuit and the main power circuit should have a clear layout distinction.
4. Try to avoid parallel wiring of high current and high voltage wiring and measurement and control lines.
5. Apply copper to the blank board as much as possible.
6. In high-current high-voltage wiring connections, try to avoid long-distance connections in the space with wires, and the interference caused by it is difficult to handle.
7. If the cost allows, the use of multi-layer board wiring, with a dedicated auxiliary power layer and ground plane, will greatly reduce the impact of EMC.
8. The workplace is the most susceptible to interference, so try to use large-area copper wiring.
9. The wiring of the shield ground does not constitute an obvious loop, which will form an antenna effect and easily introduce interference.
10. High-power devices are best placed in a relatively regular layout for easy installation of the heat sink and design of the heat dissipation air duct.