man with drill
To generate a modern printed circuit board (PCB) for items as varied as cell phones and vehicle dashboard components, many types of PCB assembly equipment are required. Typical equipment consists of solder paste and wire connectors, pick and place devices, reflow ovens and optical inspection machines. In addition, the PCB assembly equipment also includes a test engine to ensure that each board works correctly.
A solder paste and wire binding machine creates the solder pads along the surface of the printed circuit board. The wire mesh is cut into a pattern specific to the pads and placed on a blank PCB; Solder paste is forced through the open mesh holes in the surface of the board. The resulting pattern of solder paste on the PCB creates the circuitry needed for future placement of electronic components.
PCB pick-and-place assembly equipment can be described as automated hands that locate and position tiny electronic components, such as resistors, from a stockpile of supplies onto solder boards. Previously, workers performed this part of the assembly manually, but more modern components are extremely small and more difficult to place. This specialized type of PCB assembly equipment ensures that the correct component is placed in a particular orientation so that the circuit works properly.
Electronic components are temporarily held in place by solder pad paste; however, they must be permanently soldered to the PCB by entering a reflow oven. This extremely hot oven allows components to adhere to fusion solder plates. Heat is controlled within a specific range to ensure solder flows steadily while retaining the structural integrity of each component.
As soon as the plate leaves the reflow oven, it must be inspected by an optical machine. The components are extremely small; any defects or partial solder spots cannot be seen with the human eye. A worker places the board through this specialized optical PCB assembly machine. Light reflects off board components and circuits and bounces off various sensors; these sensors can detect the slightest break in the circuit or an incompatible component. Any problems are reported via the machine’s display for immediate repair or rebuild.
The last form of PCB assembly equipment that the board must go through is a test module. Each PCB manufacturer has a different testing process depending on the intended use of the board. Typically, an employee will place the board on the test equipment and apply electrical power. Each board function will need to be checked for activation and deactivation as well as reliability.