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Endoscopy inspection in electronics-detect BGA defects

2017-12-21 04:18  
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Endoscopy is known to be used in medicine, but it can also be used in other areas of industry like electronics.

In big electronic industries where investments are huge, the requirements to quality are also big. In big industries there are automatic testing using. This allows to achieve maximum quality with minimal cost. In smaller industries there is requirement to inspect almost every product to avoid faults. One of the biggest problems that may occur is soldering errors, position errors or other defects. For visual defect identification often endoscopy is used.

Endoscopy in electronics is some kind of AOI a€“ Automatic Optical Inspection, which is often used to check BGA pins. Endoscope usually consists of light source directed by fibber glass and optical sensor with variable focus. Changing focus length it is possible to view about 50mm area while space between chip and board can be only 0.05mm. Information from optical sensor can be sent to computer for further processing. Comparing to X-RAY method optical inspection of electronic devices is cheaper.

BGA_defect

Defective BGA solder

Biggest problem in visual inspection is defect detection. Visual inspection is more subjective than objective. Testing result usually depend on quality engineer. If there is no obvious disjoint of lead, then decision can be various depending on specialists conclusions.

Endoscopy_BGA

Good BGA soldering

To detect defects usually organisations use database of common defects, that they could compare results and make right decision. Inspection is like experience based. Previous results help to improve future testing results. There is whole theory about this so I won’t going into this right now.

Endoscopy inspections help to detect bad solder joints under BGA packages as there is no other way to do this except X-RAY method. This is best choice for smalle organisations, that haven’t any of automatic fault detection systems. Endoscopy is not for massive series of electronic products at it is time consuming process.

Lets take on example of optical inspection system. It would be LS 3000 constructed by PACE organisation. It is used for controlling quality of soldering such packages as PBGA, CSP, Flip Chips, LBGA, CBGA. This system can also be used for labs where new technologies are being adapted.

LS3000_endoscopy

System consists of high resolution CCD video camera and sensors. Image from CCD camera is transferred to computer screen. Main features:

magnitude from 100 up to 375 times;

field from 1.5 to 6.35;

focus from zero to 228mm;

minimal space between component and board a€“ 0.05mm;

minimal space between components;

contains optical sensors with LED’s and optical fiber;

More information can be found in manufacturers site: paceworldwide.com


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