Let you know what pcba is

What are the uses of pull-up resistors and pull-down resistors?

1. Basic concepts of PCBA

PCBA does not refer to a single component or technology, but an integrated concept. It represents the fixation of electronic components (such as resistors, capacitors, chips, etc.) on a printed circuit board through welding and other methods to form a complete circuit system with specific functions. In this system, every component plays an indispensable role and works together to achieve the normal operation of electronic equipment.

2. The composition of PCBA

Printed circuit board (PCB): As the basis of PCBA, PCB is a plate-like structure made of insulating materials with conductive lines and component mounting locations on it. The design and production quality of PCB directly affect the performance and reliability of PCBA.

Electronic components: including integrated circuit chips, resistors, capacitors, inductors, etc. These components are welded to the PCB to form a circuit network. According to their functions, electronic components can be divided into passive components (such as resistors, capacitors, inductors) and active components (such as transistors, integrated circuits).

Welding materials: used to connect electronic components to PCB. Common welding materials include solder wire, solder balls, solder paste, etc. Choosing appropriate welding materials is crucial to ensuring welding quality and circuit stability.

Circuit design: This is the “soul” of PCBA, which determines the layout and connection of components on the PCB. Excellent circuit design can ensure the performance optimization, stable operation and long-term durability of electronic products.

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3. PCBA manufacturing process

Printed circuit board manufacturing: including raw material procurement, circuit pattern production, multi-layer board stacking and other steps.

Component procurement: Select appropriate electronic components based on circuit design requirements and establish cooperative relationships with suppliers.

Component patching: electronic components are accurately placed at predetermined positions on the PCB and fixed by welding and other methods.

Welding and inspection: Complete the electrical connection between components and PCB, and inspect the welding quality to ensure that there are no problems such as weak soldering or missing soldering.

4. What are the types of circuit board PCBA processing methods?

(1).Single-sided SMT mounting

Add solder paste to the component pads. After the solder paste printing on the bare PCB board is completed, the related electronic components are mounted through reflow soldering, and then reflow soldered.

(2)Single-sided DIP insertion

The PCB board that needs to be plugged in needs to be wave soldered after the electronic components are inserted by the production line workers. After the soldering is fixed, the legs can be cut and the board washed. However, the production efficiency of wave soldering is low.

(3).Single side mixed installation

The PCB board is printed with solder paste, and the electronic components are mounted and fixed by reflow soldering. After the quality inspection is completed, DIP insertion is performed, and then wave soldering or manual soldering is performed. If there are few through-hole components, manual soldering is recommended. . (Changkeshun www.smt-dip.com)

(4). Mixed single-sided mounting and insertion

Some PCB boards are double-sided, with one side for mounting and the other side for insertion. The process flow of mounting and insertion is the same as that of single-sided processing, but the PCB board needs to use a jig for reflow soldering and wave soldering.

(5). Double-sided SMT mounting

In order to ensure the aesthetics and functionality of the PCB board, some PCB board design engineers will use double-sided mounting. Among them, IC components are arranged on the A side, and chip components are mounted on the B side. Make full use of the PCB board space to minimize the PCB board area.

(6). Double-sided mixed installation

There are two ways to mix double sides:

The first method of PCBA assembly is heated three times, which has low efficiency, and the wave soldering qualification rate of using the red glue process is low, so it is not recommended.

The second method is suitable for situations where there are many double-sided SMD components and few THT components. It is recommended to use manual welding. If there are many THT components, it is recommended to use wave soldering.

5. PCBA detection method

(1). Visual inspection

Visual inspection is to look manually with eyes. Visual inspection of PCBA assembly is the most primitive method of PCBA quality inspection. It only uses eyes and a magnifying glass to check the circuit of the PCBA board and the welding of electronic components to see if there are any tombstones, connecting bridges, etc. There is too much tin, whether the solder joints are bridged, whether there is less soldering or incomplete soldering. Use a magnifying glass to inspect PCBA

(2). Online tester (ICT)

ICT allows PCBA to identify soldering and component problems. It has high speed, high stability, checks short circuit, open circuit, resistance, capacitance.

(3). Automatic optical inspection (AOI)

Automatic relationship detection can be divided into offline and online types, as well as 2D and 3D. Currently, AOI is more popular in chip factories. AOI uses a photographic identification system to scan the entire PCBA board, and then uses machine data analysis to determine the PCBA board. Welding quality, in which the camera automatically scans the quality defects of the tested PCBA board. Before inspection, an OK board needs to be determined, and the data of the OK board is stored in the AOI. Subsequent mass production uses this OK board to make a basic model to determine other boards. Is it OK?

(4). X-ray machine (X-RAY)

For electronic components with pins such as BGA/QFP, ICT and AOI cannot detect the soldering quality of the internal pins. X-RAY is similar to a chest X-ray machine. It can check whether the internal pins are soldered through the PCB surface. , whether the mounting is in place, etc. X-RAY uses X-rays to penetrate the PCB board to view the inside. X-RAY is widely used in products with high reliability requirements, such as avionics and automotive electronics.

(5). Sample inspection

Before mass production and assembly, first-piece inspection is usually performed so that concentrated defects can be avoided in mass production, causing problems in PCBA board production. This is called first-piece inspection.

(6). Flying probe tester

Flying probe probes are suitable for inspection of high-complexity PCBs that require expensive inspection costs. Design and inspection of flying probes can be completed in one day, and assembly costs are relatively low. It is capable of checking open circuits, short circuits and orientation of components mounted on the PCB. Additionally, it works well at identifying component layout and alignment.

(7). Manufacturing Defect Analyzer (MDA)

The purpose of MDA is simply to perform a visual test of the board to reveal manufacturing defects. Since most manufacturing defects are simple connection problems, MDA is limited to measuring continuity. Typically, a tester will be able to detect the presence of resistors, capacitors, and transistors. Integrated circuit detection can also be implemented using protection diodes to indicate whether components are placed correctly.

(8). Aging test

After the PCBA has undergone mounting and DIP post-soldering plug-ins, board-cutting, component surface inspection and first-piece testing, and after the mass production is completed, the PCBA board will be subjected to an aging test to test whether the various functions have functioned after being powered on for a long time. normal, whether the electronic components are normal, etc.

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5. Application fields of PCBA

PCBA is widely used in various electronic products, such as mobile phones, computers and other consumer electronics products, as well as industrial control equipment, medical equipment, communication equipment, etc. With the continuous development of science and technology, the application fields of PCBA are still expanding, and its high performance and stability provide strong support for the electronic process of various industries.

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