most common circuit board assembly techniques
The assembly process transforms the bare circuit board, essentially just a blank page with conductive pathways, into a fully functional, operational electronic device. Among the many tasks involved, one of the most important is soldering and ensuring that all components are attached properly. Often, poor component placement and assembly can create issues that result in the board not functioning as intended. To help reduce problems during manufacture and assembly, adherence to best practices should be a top priority. These include proper orientation, spacing and thermal management.
To begin the circuit board assembly process, a stencil is created with a pattern that ensures the right amount of solder paste is applied to the board in designated areas. Once the paste is in place, the board is passed to a screen printer which applies an even coat of the melted metal known as solder to each pad on the board. This step is followed by a 3D solder paste inspection machine to verify that the correct thickness and amount of paste was added. Altest utilizes several high-speed EKRA and GKG screen printing machines to apply the paste accurately and efficiently.
After the paste is applied, automated pick and place machines follow a design blueprint to delicately position surface components on the PCB. Once the components have been positioned, they are then soldered to the circuit board using either wave or reflow soldering techniques. These methods use a metal alloy known as solder to establish robust electrical and mechanical bonds.
What are the most common circuit board assembly techniques?
Orientation and Polarity: During the design phase, it is recommended that similar SMT components are oriented in the same direction to ensure consistent placement and reduce errors during placement and soldering. This will also simplify the assembly process and save time.
Spacing: Strictly adhering to spacing guidelines helps to prevent solder bridging, which could cause potential circuit failure. Additionally, it is critical that the package size of each component is appropriate. Choosing smaller packages when possible helps to decrease assembly time, avoid errors during insertion and ultimately increase longevity of the finished product.
Reflow soldering is used for surface-mount components. After the board is populated with components and solder paste, it is heated in an oven, where the solder paste melts and forms solid joints between the components and the PCB. The temperature profile of the reflow process is carefully controlled to avoid damaging the components.
For more complex, through-hole components, the assembly process includes manually or automatically inserting the component leads into holes drilled into the PCB and then soldering them to pads on the opposite side of the board. This technique offers strong mechanical bonds and is well suited for components that need to withstand significant physical stress or require high power levels. After the soldering, a post-soldering inspection is performed using automated optical inspection (AOI), X-ray inspection or functional testing to ensure that all components are connected and correctly aligned. Once the inspection is complete, the assembled boards are cleaned to remove flux residues and packaged for shipment.