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PCB,also known as printed circuit boards,are providers of electrical connections for electronic components.Circuit boards are often represented by "PCB",but cannot be called "PCB boards".
Its development has a history of more than 100 years;its design is mainly layout design;the main advantage of using circuit boards is to greatly reduce wiring and assembly errors,and improve the level of automation and production labor rate.
At present,there are a wide variety of testing technologies used in the field of electronic assembly testing.Commonly used are Manual Visual Inspection (MVI), In-Circuit Tester (ICT), and Automatic Optical Inspection (Automatic Optical Inspection, AOI for short), Automatic X-ray Inspection (AXI for short),Function Tester (FCT for short), etc.
They can be classified into two categories according to whether the PCBA has passed power-on: one is electrical testing technology, the other is the end of non-electrical testing, or whether the PCBA is in contact with the test equipment is divided into two categories: one is the end of contact testing, One is non-contact testing technology.
Manual Visual MVI
The manual visual test is to confirm the component placement, insertion, and soldering materials on the PCBA board through human visual comparison. Rely on the operator's eyes to see goods supplemented by magnifying glass and microscope visual inspection. This technique is one of the oldest and most widely used online testing methods.
However, with the application and development of microelectronic surface assembly technology (SMT processing), electronic products are developing in the direction of light, thin and miniaturized, and the density of printed board assemblies (PCBA) has become higher and higher with the continuous miniaturization of components.Cheats plug-in components block each other’s sight, as well as micro-packages (0201), "invisible" solder joints (such as BGA,CSP,and flip-chip components FCA) that have appeared widely in recent years.The method of "viewing color" is powerless to the naked eye, and the quality of PCBA processing can no longer be guaranteed.
Someone once carried out such an experiment, letting four experienced inspectors inspect the solder joint quality of the same board (medium-complexity circuit board,such as 300 components,3,500 nodes single board) four times respectively. As a result, the first inspector detected 44% of the defects,the second inspector had a 28% agreement with the first, and the third inspector had a 12% agreement with the first two.And the fourth inspector has only 6% agreement with the first three.This test exposed the subjectivity of manual visual inspection, which is neither reliable nor economical.At present,the manual visual testing method is only used as a supplementary auxiliary method in the manufacturing process.
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