PCB Assembly Process

Once the PCB and production materials are ready, solder paste is applied to the appropriate pads on the PCB using a stencil printer. The stencil defines where the solder paste is deposited, while the squeegee controls how the paste is transferred onto the board.

The amount and position of solder paste are important because they directly affect the quality of the solder joints during reflow. Printing parameters such as stencil alignment, squeegee pressure, and printing speed need to be properly controlled for consistent results.

After solder paste printing, the PCB passes through a Solder Paste Inspection (SPI) machine to check whether the paste has been applied correctly. SPI equipment uses 3D imaging to measure factors such as solder paste volume, height, area, and position.

This inspection helps identify problems such as insufficient solder paste, excessive paste, or paste offset before components are placed. Detecting these issues at this stage allows them to be corrected before they become soldering defects later in the process.

After the solder paste has been inspected, the PCB moves to the pick-and-place machine. The machine automatically picks components from feeders and places them onto the corresponding PCB pads according to the assembly data.

Placement accuracy is particularly important for small and fine-pitch components, where even a small deviation can affect soldering quality. The placement program, component orientation, feeder setup, and machine calibration all need to be properly controlled before production.

With the components placed on the PCB, the board enters the reflow oven to permanently solder the components in place. The PCB passes through several controlled temperature zones, typically including preheating, soaking, reflow, and cooling.

During the reflow stage, the solder paste melts and forms solder joints between the component terminals and PCB pads. A suitable temperature profile is important to achieve reliable solder joints while avoiding excessive thermal stress on the PCB and components.

After reflow soldering, the assembled PCB is inspected using Automated Optical Inspection (AOI). The AOI system uses cameras and image processing to compare the assembled board against the expected assembly data.

Depending on the equipment and inspection requirements, AOI can identify issues such as missing or misplaced components, incorrect component orientation, solder bridging, and other visible assembly defects. Boards with detected abnormalities can then be reviewed and corrected before moving to the next stage.

After the main assembly process is completed, the PCBA undergoes final inspection to verify its overall assembly quality. Engineers or quality inspectors check the board for visible defects and confirm that the required components have been correctly assembled.

Where functional testing is required, the assembled PCB is also tested under defined operating conditions to verify that it performs as intended. The specific test method depends on the product design and customer requirements.

Once the PCBA has passed the required inspections and tests, it is prepared for shipment. The finished boards are handled and packaged according to their requirements to help prevent damage, contamination, electrostatic discharge, and other issues during transportation.

At AIVON, PCBAs can be shipped using major international express carriers such as DHL, FedEx, and UPS, along with other shipping options based on the customer's requirements. The completed orders are properly labeled, packed, and prepared for delivery to help ensure a smooth and reliable shipping process.