Printed Circuit Board Manufacturing Assembly
Printed circuit board (PCB) assembly is the process of mounting and soldering electronic components onto fabricated PCBs to create functional boards and assemblies. The most common methods of PCB assembly are through-hole and surface-mount technology, though both have their own advantages and uses. The most important aspect of a successful PCB assembly is having reliable interconnects. Several factors can affect the reliability of solder joints, including metallurgy, thickness, and layout. These factors can have a direct impact on the life and performance of a PCB, especially in demanding applications like MEMS pressure sensors.
The fabrication of a pcb manufacturing assembly starts with the design files that are generated by a PCB designer. These output files include Gerbers, netlists, drill files, and a bill of materials for the fabrication process. Once the design is completed, these files are sent to a PCB manufacturer to be converted into physical circuit boards ready for component placement and soldering.
To convert the file into a PCB, a layer of photo-reactive chemicals called a photoresist is applied to a blank copper-clad panel. This chemical reacts with light to form a positive image of the circuit layers and a negative image of the solder mask on the surface. The resulting image can be read by a computer to precisely match it with a pre-loaded CAD/CAM design file. The unexposed areas are then removed by a solvent that leaves behind only the preferred copper substrate on the PWB. The remaining solder resist, which is typically green, protects the copper from being melted by reflow soldering and other manufacturing processes.
How Printed Circuit Board Manufacturing Assembly Is Used in Flexible Pressure Sensors
A legend, which is typically printed with ink, helps identify the PWB’s component designators, switch settings, and other indicators that are useful during assembly, testing, and servicing. The legend is usually printed on one or both sides of the board. Screen printing is the most traditional method of legend printing, but liquid photo imaging and ink jets are now more commonly used.
Once the PCB is prepared for component placement, it goes through a reflow soldering process that melts a metal alloy to affix and secure the components to the circuit board. The reflow process also ensures that all of the solder connections are strong and durable. Once the soldering is complete, the circuit board passes through a quality inspection and functional test to make sure that it performs as intended.
A key consideration in the development of a flexible PCB is the minimum bend radius, which determines the bending capabilities of the board. A smaller bend radius increases flexing endurance and improves board stiffness, but reduces the ability to accommodate high-frequency signals. Flex PCBs can use a combination of techniques to optimize both flexing and high-frequency performance, such as selecting the right materials for the core and stackup, using thermal mitigation vias, and designing a rigid-flex board with a large copper area to dissipate heat efficiently. Additionally, the PCB’s layout can be engineered to help maximize flexing endurance by placing critical components in high-speed zones and using conductive traces with small diameters.