“Visual inspection”

“Visual inspection”
Jüri Josepson & Vadim Troitski
Elcoteq Presentation / author
21.04.06
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Why visual inspection
• Check, that our processes are on a level that we
produce “good” products.
• Check, that no “not-good” products goes to the
customer.
• Send “not-good” products to repair.
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Quality
• In its broadest sense, quality is a degree of excellence: the
extent to which something is fit for its purpose. In the
narrow sense, product or service quality is defined as
conformance with requirement, freedom from defects or
contamination, or simply a degree of customer
satisfaction. ----- Quality is the result of a comparison
between what was required and what was provided.
(The Institute of Quality Assurance, on homepage)
• In technical usage, quality can have two meanings: 1. the
characteristics of a product or service that bear on its
ability to satisfy stated or implied needs. 2. a product or
service free of deficiencies.
(The American Society for Quality, on homepage)
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Standards
• ISO, IEC, IPC, JEDEC, ....
• IPC-A-610 Revision D
• EESTI STANDARD EVS-EN ISO 9001:2001
– Tõlgendamise erimeelsuste korral on kehtiv inglise
keele tekst (lk. 17)
• Several journals are discussing assembling:
– www.circuitsassembly.com
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IPC-A-610D
• ESD, handling, ...
• Class 1 -- General Electronic Products
• Class 2 -- Dedicated Service Electronic Products
• Class 3 -- High Performance Electronic Prod
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Manual inspection
Inspection
Reference
Land Widths or Land Magnification Magnification
Power
Power
Diameters
>1 mm
1.75X
4X
>0.5 to 1.0 mm
4X
10X
0.25 to 0.5 mm
10X
20X
<0,25 mm
20X
40X
• Magnifying glass
• Microscope
• Oblique vision system
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Manual inspection
• Health precaution (work with microscope)
– after 20 min. work close your eyes and till your
head down for 20 sec.
– After 1 hour work stand up, move for 5-6 min. and
look far away.
– It is not allowed to collect these times!
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BGA inspection
(Ersascope)
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AOI – Automated Optical Inspection
• It is an inspection tool using cameras that optically scans
a board comparing the information with that of known
good boards to detect errors in manufacture.
• Typically these may be incorrect components, incorrectly
placed components, missing components and dry joints.
• AOI systems basically cover only physical failures.
Electronic defects cannot be detected. Also, the
inspection of BGA’s or components with similar packages
CSP is not possible.
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Why AOI?
• Despite the major improvements that have been made,
modern circuits are far more complicated than boars
were even a few years ago.
• The introduction of surface mount technology, and the
subsequent further reductions in size mean that boards
are particularly compact.
• Even relatively average boards have thousands of
soldered joints, and these are where the majority of
problems are found.
• This increase in the complexity of boards also means
that manual inspection is not a viable option these
days. Even when it was an accepted approach, it was
realized that it was not particularly effective as
inspectors soon tired and poor and incorrect
construction was easily missed.
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How they work
• The board is light by several light sources and
there are likely to be a number of high definition
cameras. This enables them to monitor all areas
of the board, even those hidden in one direction
by other components.
• The AOI system takes time to “learn” the board. It
must be able to recognize and adapt to
differences in the appearances of the board that
result from the normal production process
variations.
• However it must be able to recognize any that
affect performance. To achieve this it is normal to
run a number of good boards through the system
before full production starts so that the system can
“learn” the board.
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• Gray Scale Correlation,
• Vectoral Imaging
HT1869V
FBV21
9803
• Optical Character
Recognition (OCR)
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Quality of AOI inspection
• Good level for AOI 1-2 escapes per
60000 inspected
components
• Normal level for AOI 3-5 escapes per
60000 inspected
components
Escape
• Good level for AOI - 5-6 False alarms per 1000 inspected
components
• Normal level for AOI - 10-15 False alarms per 1000 inspected
components
0
0
False alarms
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AXI – Automated X-ray Inspection
• A form of inspection that uses X-Rays and in this
way joints under components such as ball grid array
chips can be seen.
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Why AXI?
• The growing trend to use ICs with packages such as ball grid arrays
(BGA) where the connections are underneath the chip and not visible
means that ordinary optical inspection is not viable.
• Additionally as the connections are underneath the chip package
there is a greater need to ensure that the manufacturing process is
able to accommodate these chips correctly.
• Additionally the chips that use BGA style connections are generally
the larger ones with many connections and it is essential that all the
connections are made correctly.
• As they are not visible the only alternative is to use a low level X-Ray
inspection. These inspection systems are more costly than ordinary
optical systems, but they are able to check all the connections.
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Agilent 5DX Series 5000
• Agilent 5DX Series 5000 model 5400 has the
resolution capability to inspect to 8mil/0.2mm pitch
devices.
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How laminography works
• An electron beam is moving on the circle changing the position where
the X-rays are generated. The detector is also rotating but is 180° out
of phase compared to the electron beam. The image is over a
complete rotation.
• The letter “T” on the top side of the board is in the focal plane and
always appears on the same position of the detector. The letter “B” on
the bottom side of the board is not in the focal plane If you increase
the detector rotation speed the letter “B” is smeared and disappears
finally in the background.
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Phoenix X-ray PCBA Analyser
•
•
•
•
•
scanning area: 610x460mm
maximum sample size: 710x560mm 5kg
geometrical magnification: up to 2060x
total magnification: up to 12800x
detail detectability: less than 1 um, down to 0,2um with nanofocus
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