As the core technology used in modern electronics manufacturing, SMT (Surface Mount Technology) assembly density is increasing, the number of pins is increasing, and the pitch is decreasing. In addition, more SMDs (Surface Mount Devices) rely on non-visual pins as packages.
These changes place higher requirements on the inspection and testing applied during the SMT assembly process. And it is becoming increasingly important to set inspection and test procedures and adopt inspection techniques during the SMT assembly process.
We have long cooperated with major brand component agents to sign traceability agreements to ensure the quality of components. This largely guarantees the quality of the PCBA after assembling.
After receiving the components, our IQC will check all components for damage and oxidation. Compared the components with the data sheet, check the footprint and the silk print on the components. We compare each component with the actual PCB to ensures the accuracy of the components and the correct packaging.
We will use LCR meter to test some components, for some chips and high temperature and humidity requirements parts, we will store them in a constant temperature and humidity cabinet. Then start to assemble work after all components arriving.
In addition to inspecting components, we also inspect PCB board and solder pastes before assembly. We have a cabinet for storing solder paste. We process the expired solder paste in time, manage the material according to the first-in, first-out mechanism. All PCB boards have been tested before leaving the factory. Before assembling, we will check the appearance of the PCB board, whether there are board warps and scratches.
AOI (Automated Optical Inspection)
When automatic detection, the machine automatically scans the PCB through the camera. Collects the images, compares the tested solder joints with the qualified parameters in the database. And after image processing, checks the defects on the PCB, and displays / marks the defects through the display or automatic signs come out for repair. Using high-speed and high-precision visual processing technology to automatically detect various mounting errors and soldering defects on PCB boards. PCB boards can range from fine-pitch high-density boards to low-density large-size boards, and can provide online inspection solutions to improve production efficiency and welding quality.
By using AOI as a tool to reduce defects, find and eliminate errors early in the assembly process to achieve good process control. Detecting defects early will avoid sending bad printed circuit boards to subsequent assembly stages, and AOI will reduce repair costs and avoid scrapping non-repairable circuit boards.
AOI Implementation Goals
In SMT, AOI technology has functions such as PCB board inspection, solder paste printing inspection, component inspection, and after assembly inspection. The emphasis is different when testing different stages.
1. End quality.
Monitor the final state of the product as it exits the production line. When production issues are clear, product mix is high, and quantity and speed are key factors, this goal is preferred, we usually place AOI at the end of the production line. In this position, the device can generate a wide range of process control information.
2. Process tracking
Use inspection equipment to monitor the production process. Typically includes detailed defect classification and component placement offset information. When product reliability is important, low-volume high-volume manufacturing, and stable component supply, manufacturers prioritize this goal. This often requires placing inspection equipment at several locations on the production line, monitoring specific production conditions online, and providing the necessary basis for adjustment of the production process.
AOI Equipment Location
Although we can use AOI in multiple locations on the production line, each location can detect special defects, but place AOI inspection equipment in a location that can identify and correct the most defects as early as possible. There are 3 check positions:
1. After solder paste printing.
If the solder paste printing process meets the requirements, the number of defects found by ICT can be greatly reduced
2. Before reflow soldering.
Inspection is done after the components are placed in the solder paste on the board and before the PCB is sent to the reflow oven. This is a typical location for inspection machines, as most defects from solder paste printing and machine placement can be found here. The quantitative process control information generated at this location provides information on the calibration of high-speed chippers and close-pitch component placement equipment. This information can be used to modify component placement or to indicate that the placement machine needs calibration. Inspection at this location meets the goals of process tracking.
3. After reflow soldering.
Inspection is performed at the last step of the SMT process. This is currently the most popular choice for AOI, as all assembly errors can be found at this location. Post-reflow inspection provides a high level of security because it identifies errors caused by solder paste printing, component placement, and reflow processes.
With the development of high-density packaging technology in the PCBA industry, new challenges have also been brought to test technology. In order to meet new challenges, many technologies are also emerging. X-RAY testing equipment, as one of the mainstream methods of non-destructive testing equipment, can effectively inspect the quality of BGA welding and assembly.
For the PCBA industry, the quality of BGA testing has attracted more and more attention, especially the miniaturization of PCBA packages. In addition, after soldering the plug-in on the PCBA board, because we cannot see the pins from the appearance of the product, the market mostly uses X-ray equipment to check abnormalities such as solder bubbles, false soldering, and missing soldering. In a sense, X-ray inspection technology is a necessary means to ensure the quality of electronic assembly.
After the assembly work, we will do visually inspect to check whether have any false, such as cold soldering or missing soldering.
Other Test For PCBA
PCBA test also includes 5 main forms: ICT test, FCT test, Aging test, Fatigue test, test under harsh environment. Sometimes our customer will provide function test file, we will check all PCBA function good then ship out them.
The ICT (In Circuit Test) test mainly includes the continuity of the circuit, the voltage and current values and the wave curve, amplitude, noise, etc.
We have been engaged in the production and assembly of circuit boards for more than 18 years. Our QA conducts comprehensive inspection to ensure good quality during all process of PCB making and assembly. We have cooperated with customers over 80 countries with hundreds of products, which are roughly divided into tracking categories, smart home, small appliances, instrumentation, industrial control, automobile manufacturing, etc.. We have extensive experience in quality control and placement for PCB and Assembly industry.
As a professional PCBA Manufacturer, we could supply one-stop service, including PCB board making, PCB Reverse Engineering, components sourcing, SMT assembly work, Program+Test, housing making, housing assembly…
We aslo have ERP system to manage every project from production file, quotation, purchase, production, delivery until service after it. Date will be found quickly and precise no matter when client wants to begin project.
If you have related projects, welcome to inquiry us to get free quotation.