PCB Fabrication Is Used in Flexible Strain Sensors
PCB fabrication, also called bare board construction, is the first step in the PCB assembly process. It creates the conductive layers of the board and prepares it for component mounting. The bare boards are then subjected to rigorous testing and inspection before the next phase of assembly begins. The bare circuit board must pass both electrical reliability and in-circuit testing to guarantee that the product will perform as intended.
The first step of pcb fabrication assembly is to prepare the copper layer with an epoxy resin that adheres it to the base material. Brown oxide is used among the inner layer to ensure that the copper foil bonds with the prepreg properly. This step is followed by etching to remove the unwanted copper and leave behind the copper areas meant to remain in the final board. This step is performed with an automated machine that uses registration holes to align the layers. A technician checks the boards to make sure that all of the resist present on the layers corresponds with the copper areas that will emerge in the finished product.
Once the bare boards are properly prepared, they undergo the drilling process. The drills must follow the PCB blueprint provided by the designer and drill through all of the required components and vias. The drilling must be precise to maintain a proper fit and prevent damage to the finished board. After the drilling, there is a scoring process. This may be done by hand or by an automated machine, depending on the company’s preferences. Scoring allows the fabricated boards to be broken apart cleanly without cracking or breaking, and it is necessary for the successful completion of the assembly process.
How PCB Fabrication Is Used in Flexible Strain Sensors
After the scoring process, a special machine known as an optical inspection machine (AOI) inspects the PCBs for any remaining defects. This automated device uses high-powered cameras that are arranged at different angles to view the solder connections on each board. Using the original Gerber file, it compares each digital image to the correct version and notates any inconsistencies. This inspection is especially critical for the more complex PCBs.
For a flexible strain sensor, the flex circuit board must be capable of withstanding a variety of bends and stresses. It must be thin and lightweight to maximize bending endurance, but it must also provide stability and rigidity. To achieve this, the flex circuit board must be made from a flexible and durable base material like polyimide or polyester.
The flex circuit board must then be cut to its proper size and apply a surface finish. One common method is hot air solder leveling, or HASL. In this process, the board is coated with a thin coating of flux that will aid in the soldering process and then dipped into a bath of molten solder. As the solder melts, it will bond with the surface metal of the bare circuit board. This bonded connection forms the essential link between the flex circuit board and its external components.
