PCB Fabrication Assembly Differ From a Rigid PCB
A PCB is an important element of most electronic devices that we use for work and play. They are an essential part of the modern world and we rely on them for everything from smartphones to tablets to computers. But, despite the fact that most advanced electronics rely on surface-mount components, there are still many through-hole parts found in most boards. The difference between a rigid PCB and a rigid-flex PCB lies in the manufacturing process, as well as in how the two types of boards are assembled.
Rigid pcb fabrication assembly are made from a thick, rigid fiberglass-based material called FR4. Copper traces and paths run through the layers and connect the different sections of the circuit board. These conductive layers are bonded together with heat and glue. Rigid PCBs can be single-sided, double-sided, or multi-layered, and they cannot be twisted or bent once they are fabricated. Rigid PCBs are a popular choice in laptop and desktop computers, audio keyboards, solid-state drives (SSDs), flat-screen TVs and monitors, and other electronic gadgets.
The PCB assembly process is a guided step-by-step process that starts with the preparation of the bare circuit board. This includes depanelization, which removes the circuit board from its manufacturing panel or panels, and if necessary, routing out the board outline except for small breakout tabs. Then, the PCB goes through continuity testing with automated test equipment such as a bed of nails or flying probe tester to look for unintentional shorts between nets.
How Does a PCB Fabrication Assembly Differ From a Rigid PCB?
After this, solder paste is stenciled onto the bare PCB in areas where components will be mounted. The process is similar to screen-printing a T-shirt; a thin stainless steel stencil and applicator are used to apply the solder paste to specific areas on the bare circuit board. Then, a mechanical fixture holds the stencil and PCB in place while a machine places SMT or through-hole components into the holes. These components are then soldered using either wave, manual, or selective soldering machines depending on the quantity and design of the component. Rigid PCBs are then washed with deionized water or IPA to remove contaminants from the soldered areas. They are then subject to inspections like AOI and X-ray.
Finally, the flex layer of a rigid-flex circuit board is attached to its rigid sections using prepreg. Often the rigid-flex PCB is asymmetrical, with the flex section being centered over one or more rigid sections. This allows the flex section to be mechanically supported and to reduce the aspect ratio of blind or buried vias.
Generally, the assembly of a rigid-flex circuit board is done with a combination of SMT and through-hole components. For example, a smart watch may use both SMT and through-hole components to control various features. To avoid the assembly process being time consuming and costly, it is essential to prepare the BOM and Gerber files correctly. This includes a separate DO NOT POPULATE (DNP) column for parts that will not be populated on the finished product, as well as providing accurate footprints and tolerances to the CM (contract manufacturer). This helps eliminate errors in the assembly process and reduces costs.
