PCB Assembly And Production Process

Product Details

PCB Assembly and Production Process

- Overview of the PCB assembly process involved in building surface mount technology (SMT) boards using pick and place technology.

 

Electronics Manufacture Includes:
Manufacturing basics     Pick & place machine    

 

There are many separate stages in printed circuit board electronics/production or manufacturing. However, all of them must work together to form a comprehensive overall process. Each stage of assembly and production must be compatible with the next stage and feedback must be passed from the output to the input to ensure the highest quality. In this way, any problems can be quickly detected and the process can be adjusted accordingly.



PCB assembly process overview

The various stages of the PCB assembly process include adding solder paste to the board, picking and placing components, soldering, inspection, and testing. All of these processes are required and need to be monitored to ensure the highest quality products are produced. The PCB assembly process described below assumes that surface mount components are now used in almost all PCB components and currently use surface mount technology.

· Solder paste:   Solder paste needs to be added to the board area that needs to be soldered before adding the board to the board. Typically, these areas are component pads. This is done using a solder screen.


· Solder paste is a paste of small particle solder mixed with solder. This can be deposited in place during a process very similar to certain printing processes.


· Using a soldering screen, place it directly on the board and register it in the correct position, move the slider across the screen, squeeze a small amount of solder paste through the holes in the screen and into the board. Since the welded mesh is produced from a printed circuit board file, it has holes in the position of the pads, and thus the solder is deposited only on the pads.


· The amount of solder deposited must be controlled to ensure that the resulting solder joint has an appropriate amount of solder.Pick and place:   During this part of the assembly process, the board with the added solder paste is then passed into the pick and place process. Here a machine loaded with reels of components picks the components from the reels or other dispensers and places them onto the correct position on the board.





Typical pick and place machine 

· The components placed on the board are held in place by the tension of the solder paste. If the boards are not vibrating, this is enough to keep them in place.

               In some assembly processes, pick and place machines add small glue to secure the assembly to the board. However, this is usually done only when the board requires wave soldering. A disadvantage of this method is that any repair becomes more difficult due to the presence of glue, although some glues are designed to degrade during the welding process.


 The location and part information required to program the pick and place machine is derived from printed circuit board design information. This greatly simplifies picking and placement programming.Soldering:   Once the components have been added to the board, the next stage of the assembly, production process is to pass it through the soldering machine. Although some boards may be passed through a wave soldering machine, this process is not widely used for surface mount components these days. If wave soldering is used, then solder paste is not added to the board as the solder is provided by the wave soldering machine. Rather than using wave soldering, reflow soldering techniques are used more widely.

· Inspection:   The board is often inspected after the soldering process. For surface mount boards with one hundred or more components, it cannot be checked manually. In contrast, automated optical inspection is a more viable solution. You can use a machine that can check the board and detect poor connectors, misplace components, and in some cases detect the wrong components.

· Test:   It is necessary to test electronic products before they leave the factory. There are several ways in which they may be tested. Further views of test strategies and methods may be found on the "Test and Measurement" section of this website.

· Feedback:   To ensure a satisfactory manufacturing process, the output must be monitored. This is done by investigating any faults detected. The ideal location is in the optical inspection phase as this usually occurs immediately after the soldering phase. This means that process defects can be quickly detected and corrected before building too many boards with the same problems.




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In this overview, the PCB assembly process for manufacturing a loaded printed circuit board has been greatly simplified. PCB assembly and production processes are often optimized to ensure extremely low defect levels to produce the highest quality products. Given the number of components and solder joints in today's products and the high quality requirements, the operation of this process is critical to the success of the manufactured product.


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