● Solder Paste
● Pick and Place
● Inspection & Test
In PCB assembly, there are a number of individual steps. However, it is necessary for them to work together to form an integrated assembly process. Each step of assembly must be compatible with the next, to ensure the good quality. In this way, any problem can be detected quickly and the process can be adjusted accordingly.
PCB Assembly Process
PCB assembly process overview：
Solder paste: Prior to the addition of the components to a board, solder paste needs to be added to those areas of the board where solder is required. Typically these areas are the component pads. This is achieved using a solder screen.
With solder screen, solder paste will be placed directly on the board and registered in the correct positions. A runner is moving across the screen, squeezing a small amount of solder paste through the holes in the screen and the boards. As the solder screen has been generated from Gerber files, it has holes on the positions of the solder pads that solder is deposited on.
Pick and place: After solder paste step, the board will pass 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. The pick and place machine is derived from the PCB design information. This enables the pick and place programming to be considerably simplified.
Soldering: Once the components have been added to the board, the next step is soldering. Although some boards may be passed through a wave soldering machine, this process is not widely used in SMT nowadays. Rather than using wave soldering, reflow soldering techniques are used more widely.
Inspection: After the boards have been passed through the soldering process they are often inspected. Manual inspection is not an option for surface mount boards with a hundred or more components. Instead, automatic optical inspection (AOI) is a far more viable solution. Machines are able to inspect boards and detect poor joints, misplaced components, and the wrong components.
Test: It is necessary to test electronic products before they come into the market. There are several ways in which they may be tested.