PCB assembly is an essential process for transforming a bare circuit board into a fully functional electronic device. It is a complex and intricate process that requires strict quality control measures to produce high-quality products. In order to ensure that your PCB assembly is performed properly, choose a PCB assembly manufacturer with the right capabilities and expertise for your project. A trusted manufacturer will have a long list of industry contacts, allowing them to source components at competitive prices and with fast turnaround times. They will also provide a powerful communication channel between the fabrication and assembly teams to prevent misunderstandings or miscommunications that can lead to errors.
The first step in the PCB assembly process is preparing the inner layer of the board. This step involves printing the design onto a piece of laminate material with a plotter printer. The printed film is then aligned to the copper layers on top of the board using registration holes. Once the alignment is complete, a copper paste is added to the bottom of the board to create traces that will carry the electric current through the device. Once the copper is placed, a solder mask is added to both sides of the board to limit the contact between different components.
Once the inner layer is in place, a technician inspects the product to make sure that all of the resist has been properly covered with copper and that none of the unintended areas remain exposed. This step only applies to boards that have more than two layers, since simple two-layer boards skip ahead to drilling.
Next, a stainless-steel stencil is applied to the board using a mechanical fixture. The stencil is then used to apply a precise amount of solder paste to the areas that will be connected to other components. This is a common step that requires both a high level of skill and accuracy. A robot then picks up and places surface mount components, or SMTs, on the prepared PCB. This step is automated for mass-production PCB lots, as machines are faster and more accurate than humans and can work around the clock without suffering from eyestrain or fatigue. The placement machine can be programmed to place specific types of components based on the requirements of your project, or it can be programmed to randomly select components from a reel.
The last step in the PCB assembly process is testing and evaluating the performance of the finished board. After the board is assembled, it is powered and tested for passive features such as solder bond strength or impedance. The test results are compared to the original specifications of the design and any necessary adjustments are made. Functional testing is then performed to confirm that the PCB functions as intended. The board is then ready for shipping to the final customer.