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Gradual development of technology leads electronic manufacturing technologies to non-stop improvement. As a result, electronic products tend to become miniaturized with densification being increasingly protruding. Moreover, as components become downsized and PCBs (Printed Circuit Boards) have to accept increasingly higher density interconnections, mounting density has rocketed to a high extent, leading to increasingly higher product quality requirement. Therefore, inspection on product quality during electronic manufacturing process is never insignificant.

Apart from potential trend of modern electronics, visual inspection with the help of visual inspection devices demonstrates more merits than traditional naked-eye inspection.

• Naked-eye inspection is tiring with low efficiency.

• Naked eyes fail to meet the inspection requirement of miniaturized component inspection.

• Naked-eye inspection is bad for working staff’s eyesight and difficult to capture accurate inspection result.

Nevertheless, depending on visual inspection devices, labor intensity will be greatly decreased with inspection efficiency upgrading. Up to now, visual inspection under inspection devices has been widely applied in all phases of electronics manufacturing.

What is the application of visual inspection in component quality control?

Component manufacturing has long seen much significance of visual inspection because it works for silkscreen, line loop resistance, inductance, polarity and orientation. All the aspects mentioned above are inspected by staff in naked eyes and higher subjectivity tends to be generated and staff are easy to suffer from fatigue. As a result, component quality accuracy and reliability are hard to be captured. By amplifying image through inspection devices prior to inspection, defects will become clearer and staff will be confronted with less fatigue.

What is the application of visual inspection in PCB quality control?

Even the most simplified version of PCB manufacturing process still contains 10 steps at least.

When it comes to PCB quality control inspection, most attention has to be paid to the following inspection items: foreign matter, copper exposion, scratch, insufficient plating, incorrect silkscreen, ineven solder paste and pads, residual copper, and imaging. All those defects are hardly observed through naked eyes. At present, visual inspection methods or devices for PCB quality control include:

• AOI equipment for bare PCB inspection. AOI ranges for bare PCB boards cover short circuits, open circuits, residual copper, vacancy etc.

• Magnifying glass. Magnifying glass is only capable of inspecting defects that are exposed on the surface of PCB. This method is seldom leveraged in modern electronics manufacturing.

• Naked-eye inspection. Naked-eye inspection is an old-school inspection method although it seldom meets constant improvement of quality control and PCB design density. As a result, reliability and stability of naked-eye inspection are hard to be ensured.

• Optical video display system combining naked-eye inspection and AOI. This system displays PCB images on monitor through magnifying them to make inspection easier.

What is the application of visual inspection in SMT/AI technology?

SMT is now the most prevalent assembly technology in electronics manufacturing. Printed Circuit Board assembly process with the application of SMT mainly include: solder paste printing, mounting, reflow solder, cleaning, inspection and rework. All inspection devices applied in all phases of manufacturing include: magnifying glass, microscope, ICT (In-Circuit Test), flying probe test, AOI, AXI and function test among which magnifying glass, microscope, AOI and AXI belong to the range of visual inspection.

Visual inspection will cause different inspection results and targets by placing on different stations during SMT assembly process.

After Solder Paste Printing

Solder paste printing is the first procedure of SMT assembly and its quality directly determines that of final products. Thus, it’s of much necessity to arrange visual inspection after solder paste printing. Up to now, solder paste printing inspection is carried out through the following methods:

a. On-line or off-line solder paste inspection, which mainly displays 3D configurations of solder paste that has been printed on pads on the monitor so that defects can be exposed in terms of thickness, volume, displacement, vacancy, excessive or insufficient solder paste.

b. Magnifying glass.

c. CCD inspector. It displays magnified images on the monitor so that operators will be aware of printing quality.

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