Step 1: Solder Paste Application Using Stencil

　　First, we apply solder paste to the areas of the printed circuit board where components will be mounted. This is done by applying the solder paste onto a stainless steel stencil. The stencil and PCB are held together by a mechanical fixture, and then the solder paste is evenly applied to all the openings on the board via an applicator. The applicator applies the solder paste evenly; therefore, the right amount of solder paste must be used in the applicator. When the applicator is removed, the solder paste will remain in the desired areas of the PCB. The gray solder paste is 96.5% tin, contains 3% silver and 0.5% copper, and is lead-free. After heating in step 3, this paste will melt and form a strong joint.

　 　Step 2: Automated Component Placement

　　The second step in pcba is to automatically place the SMT components onto the PCB board. This is done by using a pick-and-place robot. At the design level, the designer creates a file that will be fed into the automated robot. This file has pre-programmed X, Y coordinates for each component used in the PCB and identifies the location of all components. Using this information, the robot will simply place the SMD devices accurately on the board. The pick-and-place robot will pick up the components from its vacuum fixture and place them accurately on top of the solder paste.

　　Before the advent of pick-and-place robots, technicians would use tweezers to pick up the components and then carefully observe the position and avoid hand tremors to place them on the PCB. This led to high technician fatigue and eye strain and resulted in a slower SMT component PCB assembly process. Therefore, the chances of errors were very high.

　　With the advancement of technology, automated robots for picking and placing components have relieved technicians of their workload and enabled fast and accurate component placement. These robots can work 24/7 without fatigue.

　 　Step 3: Reflow Soldering

　　The third step after the components are placed and the solder paste is applied is reflow soldering. Reflow soldering is the process of placing the PCB along with the components on a conveyor belt. The conveyor belt then moves the PCB and components into a large oven with temperatures as high as 250 o C. This temperature is sufficient to melt the solder. The molten solder will secure the components to the PCB and form solder joints. After the PCB is subjected to high temperatures, it enters a cooler. The cooler then solidifies the solder joints in a controlled manner. This will form a permanent solder joint between the SMT components and the PCB. For double-sided PCBs, the side of the PCB with fewer or smaller components will be processed first from steps 1 to 3 above, and then the other side will be processed.

　 　Step 4: Quality Control and Inspection

　　After reflow soldering, components may be misplaced due to some wrong movements in the PCB tray and may cause short circuits or open circuits. These defects need to be identified, and this identification process is called inspection. Inspection can be manual or automated.

　 　a. Manual Inspection:

　　Because the SMT components on the PCB are small, visually inspecting the board for any misplacements or faults will lead to technician fatigue and eye strain. Therefore, this method is not suitable for advanced SMT circuit boards due to inaccurate results. However, this method is suitable for boards with THT components and lower component density.

　　b. Optical Inspection:

　　For high-volume PCBs, this method is feasible. This method uses automated machines that have high-power and high-resolution cameras mounted at various angles to view the solder joints from all directions. The light will reflect off the solder joints at different angles depending on the quality of the solder joint. These Automated Optical Inspection (AOI) machines are very fast, and the time required to process high-volume PCBs is very short.

　 　X-Ray Inspection:

　　X-ray machines allow technicians to see inner-layer defects through the PCB. This is not a common inspection method and is only used for complex and advanced PCBs. Incorrect application of these inspection methods may lead to PCB rework or scrap. Regular inspection is required to avoid delays, labor, and material costs.

　 　Step 5: THT Component Fixing and Soldering

　　Through-hole components are common in many PCB boards. These components are also known as plated through-holes (PTH). The leads of these components will pass through holes on the PCB. These holes are connected to other holes and through-holes via copper traces. When these THT components are inserted and soldered into these holes, they will be electrically connected to other holes on the PCB that are the same as the designed circuit. These PCBs may contain some THT components and many SMD components, therefore, the above-mentioned soldering methods such as reflow soldering for SMT components are not suitable for THT components.

　 　Step 6: Final Inspection and Functional Test

　　Now the PCB is ready for testing and inspection. This is a functional test where electrical signals and power are supplied to the PCB at designated pins and the output is checked at designated test points or output connectors. This test requires common laboratory instruments such as oscilloscopes, DMMs, function generators

　　This test is used to check the functionality and electrical characteristics of the PCB and verify the current, voltage, analog, and digital signals as stated in the PCB and circuit design requirements

　　If any parameters of the PCB show unacceptable results, the PCB is discarded or scrapped according to the company's standard procedures. The testing phase is very important as it determines the success or failure of the entire PCBA process.

　 　Step 7: Final Cleaning, Packaging, and Shipping:

　　Now that the PCB has passed the tests and everything has been confirmed as OK, it is time to clean up any unwanted residual flux, finger smudges, and oil. A stainless steel high-pressure cleaning tool using deionized water is sufficient to clean all types of dirt. Deionized water will not damage the PCB circuitry. After cleaning, the PCB is blown dry using compressed air. Now the final PCB is ready for packaging and shipping.

　　PCB electronics refers to choosing a powerful electronics processing company to help produce products so that you can focus on the R&D and market development of new products. The PCBA electronics manufacturing process mainly includes material procurement, SMT surface mount processing, DIP plug-in processing, PCBA testing, finished product assembly, and logistics distribution. The PCBA sample assembly manufacturing process is as follows:

　　pcba testing equipment

　　Determine cooperation and sign a contract

　　After mutual consultation, a cooperation contract was signed.

　　Customer orders and provides processing information

　　The customer starts placing orders and provides the bill of materials, PCB files, Gerber files, diagrams, and PCBA test plans required for product processing.

　　 Material Procurement

　　Electronic processing plants purchase electronic components, PCB boards, steel mesh, fixtures, etc., according to customer orders.

　　 Material Arrival, Inspection and Processing

　　Upon arrival, incoming materials are inspected and processed before being delivered to PMC for planned production.

　 　SMT Surface Mount and DIP Plug-in Processing

　　Materials are processed online, going through processes such as solder paste printing, placement, reflow soldering, AOI inspection, DIP plug-in, and wave soldering to complete PCB processing and welding. Each step involves quality inspection.

　 　PCBA Testing

　　The electronic processing plant follows its own testing procedures and the customer's test plan to test the products and repair any defects found.

　 　Packaging and Transportation

　　After all products are produced, they are packaged and shipped according to customer requirements. PCBA electronic product processing is a complex process. During production, every employee must work together, strictly controlling quality according to the production process to meet customer quality requirements and deliver perfect products.