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"We convert PCBs into PCBAs at the Adiva technology PCB assembly facility. Surface mount and through-hole assemblies are included in PCB assembly. Below, observe the PCBA procedure on a whole PCB manufacturing line."
01Overview
PCB Assembly (PCBA) is the process of mounting electronic components onto unfinished PCB boards to create semi-finished devices. This procedure involves both PCBA manufacturing and testing to ensure high-quality and functional electronic products.
The PCBA process includes several essential phases: solder paste printing, SMT (Surface Mount Technology), reflow soldering, AOI (Automated Optical Inspection), THT (Through-Hole Technology), wave soldering, touch-up and cleaning, IC programming, functional testing (FCT), and aging testing. Each step plays a crucial role in ensuring the reliability of the final product.
PCBA testing is a critical part of PCB assembly, ensuring that mounted components function correctly. Various testing methods, such as functional testing (FCT) and aging tests, are conducted throughout the process to guarantee 100% product quality and customer satisfaction.
Before beginning large-scale production, a First Article Inspection (FAI) is performed on PCBA prototypes. This ensures that the design meets all specifications and quality standards. The FAI report is then sent to the client for approval before proceeding with mass production.
02Step by step
Step 1.
Verifying the BOM Our skilled engineers inspect your bill of materials (BOM) prior to assembly. In this way, the suitability of electronic components for PCB construction is ensured.
Step 2.
Moving PCBs from an automatic loader to a machine that prints solder pasteBare PCB boards are put onto an automatic loader when they are delivered to our PCBA plant from clients or manufactured in our PCB manufacturing facilities. The PCBs will next be loaded into the solder paste printing equipment by the loader.
Step 3.
A personalized SMT stencil is already pre-set inside the automatic solder paste printing device. Each PCB board is stacked beneath the SMT stencil, and one by one, the machine's scraper blade prints solder paste on the PCB pads. Typically, in PCBONLINE, we set the speed at 60±5mm/s, the tangle at 60°, and the pressure at 3±0.5KG by the blade. The distance between the PCB and the SMT stencil is set to 1.0-1.5mm, and the speed is 0.5±0.05mm/s when the PCB is removed from the stencil. Next, by allowing it to dry, the machine cleans the SMT stencil.
Step 4.
The typical solder paste thickness is between 0.09 and 0.15 mm, and the SMT stencil thickness must be within ±0.03 mm of the solder paste thickness tolerance. We check the solder paste with the SPI machine, and we can only move on to the next step with the PCBs if the solder paste's thickness falls within this range and its shape is acceptable. Depending on the needs of the application, some PCBs may require thinner or thicker solder paste; we will determine the specific thickness range.
Step 5.
We move electronic components into functional, fast mounters while printing solder paste. Large components such BGAs, FPGAs, USB connectors, connections, and so forth are moved into the functional mounter; small components like diodes, triodes, resistors, capacitors, inductors, ICs, FPC connectors, and so forth are placed into the high-speed mounter. The parts are arranged on rolls of tape on the feeder, and when the tapes are pulled by a wheel, the parts are removed from the tapes and precisely positioned inside the mounter.
Step 6.
In this stage, solder paste-printed PCBs are fed into a high-speed mounter where tiny components are inserted onto the appropriate pads. The PCBs are brought into the working mounter in a matter of seconds thanks to the high-speed mounter's lightning-fast operation.
Step 7.
Accurate placement of large components occurs when PCBs with small component mounting enter the functional mounter.
Step 8.
After placing the mounted PCBs into an X-ray machine to check for soldering flaws, a qualified technician will visually examine a few samples. Until everything is in order, the PCBs will not go to the next stage.
Step 9.
In the PCBA process, reflow soldering is the most crucial stage. A conveyor belt that travels through a reflowing oven at a constant horizontal speed transfers your installed PCBs. There are ten temperature zones in the reflowing oven. Solder paste melts on the pads as the temperature rises from the first to the ninth in accordance with the predetermined temperature curve. Solder paste solidifies in a cooling zone on the eleventh. After that, the pads and electronic components on PCBs are securely attached, and the PCBAs are yours.
Note: There is still a fluctuation in the reflowing oven's zone temperatures and conveyor velocity. In our PCBA factory, skilled experts set them based on the specifications of the application. The solder paste has a melting point of 217°C.
Step 10.
Your PCBs are mounted with components on one side after the aforementioned stages, and they typically move on to the following step. On the other hand, certain PCB designs call for component mounting on both sides. In order to mount the components on the opposite side, we will in this instance repeat steps 2 through 9.
Step 11.
We employ 3D-scanning, in contrast to other PCB assemblers whose AOI only uses 2D-scanning. Any potential flaws are indicated on the screen, and our AOI operator examines each one individually to determine whether any are actually there. We'll select the products that are flawed. Subsequently, a different professional visually inspects the PCBAs; in the same way, any flaws will be noted and faulty goods will be identified. Following that, a sampling examination of a few PCBA samples will take place in the testing region. After being sent for repair, all of the problematic goods will still need to be kept apart from other PCBAs.
Step 12.
The PCBAs are moved to a THT (through-hole technology) assembly line because some components with long legs cannot be put on PCBs on an SMT assembly line. The lengthy legs are inserted through the PCB holes using a DIP machine.
Step 13.
Components with long legs require soldering, and wave soldering accomplishes this by utilizing PCBAs to secure the components and tin to fill the space between the PCBA holes and the long legs in order to electrically link the components. After soaking the soldering side of the PCBAs in melted tin using a wave soldering oven, the component legs will be trimmed with a cutter to be between 1 and 2 mm in length.
Step 14.
We must touch up any faults that may have occurred during the wave soldering process, such as soldering holes and inadequate tin plating. A skilled worker carefully examines the PCBAs and fills the board surface with tin using a soldering iron. In the event of a short circuit, the technician will then use flux to remove any remaining tin from the board. The technician next gives the PCBAs one more inspection.
At this point, PCBA manufacturing is complete. We will transport the PCBAs to the IPQC (in-process quality control) working area if customers do not require functional tests. There, specialists will visually inspect the PCBAs one more before packaging them. Functional tests are processed if and when clients request them.
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