Adhesion in Circuit Board Assembly
Circuit board assembly is a vital step in the production of electronic devices that touch almost every aspect of our daily lives. It brings together the components that form a fully functional circuit and ensures they will work properly for their intended lifespan. Adhesives are an essential component of this process, allowing for a strong bond and protection from potential damage.
Adhesives used in the manufacturing of PCBs are available in a wide variety of formulations, each designed to suit a specific use case. Some are able to be used to adhere coverlays, stiffeners, and other support structures to the circuit board while others are capable of bonding complex geometries with precision and control. These adhesives also come in varying strengths to address different application requirements, with some offering electrically conductive and thermal properties as well as UV curing capabilities.
Regardless of the type of adhesion required, it is crucial that these products meet industry standards and comply with all applicable regulations for safety and quality assurance. This is especially true in cases where the product will be used for military applications or in other environments that require ruggedization.
The Role of Adhesion in Circuit Board Assembly
As such, all PCB assembly processes are rigorously tested for compliance with all applicable specifications to ensure that the end product will be reliable and safe. This testing is performed to ensure that all materials meet a certain minimum level of performance, and that all assembly steps are done in accordance with all applicable environmental and regulatory requirements. This is often done through a design for manufacturing (DFM) check, which Altest offers for free to all of our clients. This checks a client’s design for issues like part spacing, pin indications, footprint corroboration and more. It is a great way to catch any initial errors before they become costly production problems down the line.
One of the most important uses for adhesives in a circuit board is to hold surface-mount devices (SMD) in place. These are tiny electronic components that are mounted directly onto the surface of the board and must be held firmly in place to guarantee proper functioning. Using a pick and place machine is the most common method for placing these small components, as it is faster, more accurate, and less likely to cause human error than manual assembly with tweezers.
In order to properly bond these delicate components, PCB manufacturers must first apply an epoxy or acrylic-based adhesive film to the circuit board. This is then heated and lightly pressed in order to make the film tacky enough for adhesion. The heat must be applied carefully in order to avoid burning the components or the board. Once the adhesive is cured, it can then be moved into a reflow oven for the soldering process.
The reflow oven is a conveyor-based system that features multiple temperature zones including preheat, soak, and reflow zones. Each of these has a unique temperature profile, and the amount of time that the board spends at each of these temperatures is determined by the particular reflow oven used.