MVI (Manual Visual Inspection):

MVI, or Manual Visual Inspection, is a method used to detect defects in digital circuits during SMT production. It involves the use of the naked eye, magnification tools like magnifiers or microscopes, and sometimes metal needles or bamboo toothpicks to test QFP pins. This method helps identify issues like soldering defects or bridge connections in IC pins.

While flexible and fundamental, MVI is no longer suitable for moderately complex PCBs. It is becoming less reliable and cost-effective as more advanced methods are developed.

ICT (In-Circuit Test):

ICT is a contact-based testing method widely used for fault diagnosis in production. It involves a specially designed pin bed fixture that connects to the PCB, where spring probes test various components like resistors, capacitors, and ICs. This method provides quick fault detection by verifying analog and digital components separately.

ICT is effective in detecting various manufacturing defects such as:

• Soldering defects (bridging, excess solder, pseudo soldering, etc.)
• Component issues (wrong resistance, loss of components, incorrect polarity, etc.)

The ICT system is fast, reliable, and evolving with advances in IC technology, offering more integration and I/O capabilities. As the integration level of chips increases, testing methods such as boundary scan and non-vector detection are becoming more widely applied.

AXI (Automated X-Ray Inspection):

AXI is essential for inspecting components like BGAs and CSPs, where solder joints are hidden beneath the package. The PCB assembly enters an AXI machine, and X-rays pass through the board to create an image detected by sensors, highlighting the solder joints.

Since solder joints absorb X-rays more effectively than other materials, AXI provides clear images that make defect analysis intuitive. This technology has evolved from 2D to 3D, allowing for better inspection of double-sided PCBs or multilayer boards by isolating and imaging each layer.

3D AXI can detect defects in BGA, multilayer PCBs, and through-hole solder joints. It provides a detailed inspection by “slicing” the PCB and assessing each layer of the solder joint, ensuring thorough evaluation of all joints, which improves the overall quality and reliability of the PCB.

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