Importance of Adding AOI Inspection to SMT Production Lines
As electronic products become increasingly compact, the use of SMT technology to mount components on PCBs has become more prevalent. However, the reduction in size has made the quality of soldering and assembly more challenging. To address these issues, AOI inspection provides effective solutions. This article will explore the importance of AOI in the SMT line and explain how it works, with insights from FS Technology.
Explanation of SMT and AOI
In the image provided, the computer located next to the two employees in pink uniforms is an AOI testing equipment, the rectangular machine in front of it resembling a “coffin” is a reflow soldering machine, and the equipment in front of the employees in blue uniforms includes the SPI detector, placement machine, and solder paste printing machine, all connected via a connecting table to form a complete SMT production line.
SMT, or Surface Mount Technology, is a widely used technology in PCB assembly. In this process, the bare PCB board is loaded into the solder paste printing machine, and the solder paste is applied to the board via a preset hole using a scraper. After this step, an SPI inspection is carried out to ensure that the printing quality is acceptable and to verify accuracy. The board then moves to the placement machine where components are accurately placed on the solder paste according to a predetermined program. Once placement is complete, the PCBA board enters the wave soldering machine via the connecting table, where the solder paste solidifies after being heated to form a permanent solder joint, completing the SMT process flow.
AOI, or Automatic Optical Inspection, is a type of visual inspection. After the SMT process is complete, the PCBA board enters the AOI testing equipment along with the connecting table. Prior to this, an image of the correct PCBA board is captured by the AOI system. When the PCBA board enters the AOI equipment, it is scanned and compared to the correct image to detect any common PCB problems.
Why PCBA manufacturers must add AOI inspection to the SMT process
In the world of PCB assembly, SMT and THT are two common assembly technologies, with SMT gradually replacing THT due to the trend of miniaturization. However, SMT comes with its own set of challenges, such as difficult-to-detect issues like insufficient or excessive solder, component polarity issues, connectivity problems, and more. Manual inspection is not enough to solve these issues, hence the need for more advanced instruments.
This is where AOI detectors come in. By using high-speed cameras, image processing technology, and algorithms, AOI detectors can automatically identify and detect components and soldering conditions on PCBs. This helps manufacturers to quickly and accurately identify issues in SMT assembly, make necessary adjustments, and correct issues in a timely manner, ultimately leading to improved production efficiency, product quality, and reduced maintenance costs. As such, adding an AOI system to SMT production lines has become an inevitable trend.
At FS Technology, we connect the AOI equipment to the wave soldering machine, but there are other application forms that different PCBA companies use. Regardless of the specific application form, the working logic of AOI remains the same. Commonly used methods in the analysis system include DRC (Design Rule Check) and CAD (Computer-Aided Design). Although CAD has more advantages, both methods are used to check the design according to the input program and to compare the stored data in the AOI system with the actual image pattern captured to summarize the inspection results.
Set up new AOI procedures to improve SMT assembly quality
- To create a new plan, click “New” and give your new project a name.
- Add attributes by moving the cross lines to the four corners of the PCBA board. The system will automatically generate a test preview for you.
- Set marks by locating two character positions on the board. The AOI system will look at them when testing.
- Edit your program, which includes two methods: manual programming (for small batch PCB assembly) and CAD programming (for large batch PCB assembly). This guide will focus on CAD programming.
- Debug your program using one of three modes: automatic learning, error pause, or automatic positioning.
- Check your program by canceling the mode selection and clicking “Start”. The system will verify your program.
In addition to AOI, what detection methods are there in FS Technology?
Is it possible not to add AOI to the SMT production line?
Do I need to use AOI in THT?
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