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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 needed. Typical equipment consists of wire and solder paste bonders, pick and place devices, reflow ovens, and optical inspection machines. In addition, PCB assembly equipment also includes a testing mechanism to ensure that each board functions correctly.
A wire and solder paste bonder machine creates the solder pads along the printed circuit board's surface. Wire mesh is cut into a specific pattern for the pads and placed across a blank PCB; solder paste is forced through the open mesh holes onto the board's surface. The resulting pattern of solder paste on the PCB creates the needed circuitry pathways for future electronic component placement.
Pick and place PCB assembly equipment might be described as automated hands that locate and position tiny electronic components, like resistors, from a supply inventory onto the solder pads. Workers previously performed this assembly portion by hand, but more modern components are extremely small and are 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 will function properly.
The electronic components are temporarily held in place by the solder pad's paste; however, they must be soldered permanently to the PCB by entering a reflow oven. This extremely hot oven allows the components to adhere to the melting solder pads. Heat is controlled within a specific range to ensure that the solder flows steadily while retaining each component's structural integrity.
Once the board exits the reflow oven, it must be inspected by an optical machine. The components are extremely small; any defects or partial solder points cannot be seen with the human eye. A worker places the board through this specialized optical PCB assembly equipment machine. Light reflects off of the board's components and circuitry and bounces into numerous sensors; these sensors can detect the smallest break in the circuit or a mismatched component. Any problems are reported through the machine's display for immediate repair or rebuild.
The last form of PCB assembly equipment the board must pass through is a testing module. Each PCB manufacturer has a different testing process depending on the board's intended use. Typically, an employee will set the board on test equipment and apply electrical power. Each function of the board will need to be checked for activation and deactivation, as well as reliability.