Printed Circuit Board Assemblies Manufactured
The process that transforms a bare substrate into a fully operational Printed Circuit Board (PCB) takes meticulous planning and execution. It includes imaging and etching, component placement, soldering, and detailed inspection. Each of these steps contributes to the functionality, reliability, and user-friendliness of a finished product.
printed circuit board assemblies are fabricated from materials such as glass fiber, epoxy resin, or metals. Those that are multi-layer offer an even greater level of sophistication, featuring multiple stacked layers with insulating material between them. Plated through holes connect these layers, allowing for 4 to 12 or more layers in high-density designs.
To begin fabrication, a PCB contract manufacturer (PCB CM) receives electronic data in the form of Gerber files. The data identifies the shape, size, and layer sequence of each layer on the circuit board, along with the layout of all the components that must be placed. This data is then used to generate the image files needed for imaging and etching.
How Are Printed Circuit Board Assemblies Manufactured?
The glass fiber or other base material is then impregnated with epoxy resin by dipping or spraying. This resin is semicured in a heated oven. Once it is fully cured, the board is cut into large panels.
Next, a machine known as a laser or photolithography system prints the images of the layer layout and circuitry patterns onto each panel. The resulting imaged layers of copper foil are layered on top of the epoxy. The conductive pattern is masked off using a film or other means, and the exposed areas are chemically cleaned to remove any resin smears. A tin plating process then coats the exposed copper with a thin tin layer, which prevents oxidation and enhances the solderability of the board.
Using an etching process, the exposed copper is etched away to leave the final plated copper circuitry pattern. The tin-lead coating is then removed, and the remaining conductive surface is coated with an anti-oxidation copper.
Finally, the patterned substrate is masked off again and the contact fingers are plated with metals such as nickel, gold, or silver to facilitate electrical contact. The circuit boards are then sealed with an epoxy to protect them from contamination while the assembly and component placement processes take place. Instructions and other markings are stencilled on the boards at this point.
Depending on the design, the circuit boards are then either routed out or broken apart at this stage. Routing out uses a machine to create v-shaped cuts in the edges of each individual board, or, if the circuit board is to be broken apart after assembly, the entire board is scored with a cutter or CNC machine. The individual circuit boards are then packaged for shipment. The packaged boards undergo continuity testing with automated equipment such as a bed of nails or flying probe test systems. Any unintentional shorts between traces on different layers are identified and corrected at this stage. The resulting boards are shipped to the contract manufacturer for component assembly.