AOI Automated Optical Inspection：
The high speed and high precision vision processing technology is used to automatically detect all kinds of wrong placement and welding defects on the PCB board. PCB board can range from thin high density board to low density large size board, and can provide online detection scheme to improve production efficiency and welding quality. By using AOI as a tool to reduce defects, we can find and eliminate errors in the early stage of assembly process to achieve good process control. Early detection of defects will avoid sending bad boards to subsequent assembly stages. AOI will reduce repair costs and avoid discarded non repairable PCB.
Why AOI
Because of the change of circuit board size, it brings more challenges, because it makes manual inspection more difficult. In response to these developments, more and more OEMs are adopting AOI. By using AOI as a tool to reduce defects, we can find and eliminate errors in the early stage of assembly process to achieve good process control. Early detection of defects will avoid sending bad boards to subsequent assembly stages. AOI will reduce repair costs and avoid discarded non repairable PCB.
|
Comparison of AOI and manual inspection |
Manual inspection |
AOI Inpsection |
|
|
pcb<18*20 within one thouandpad |
Worker |
Important |
Supplementary Examination |
|
Time |
Normal |
Normal |
|
|
Persistence |
Not stable |
good |
|
|
Reliability |
Not stable |
Very good |
|
|
accurately |
Not stable |
High rate of delay |
|
|
pcb<18*20Over one thousandpad |
Worker |
Important |
Supplementary Examination |
|
Time |
Long |
short |
|
|
Persistence |
Not stable |
good |
|
|
Reliability |
Not stable |
Very good |
|
|
accurately |
Not stable |
High rate of delay |
|
|
Pcb Four zones (each station is responsible for one quarter of the inspection board) |
|||
main characteristics
1) High speed detection system
It is independent of PCB mounting density
2) Fast and convenient programming system
-Under the graphic interface
- automatic data detection using post mounted data.
-Using component database to edit test data quickly
3) Using a variety of special multi-functional detection algorithms and binary or gray water
Detection by imaging processing technology of photolithography
4) According to the instantaneous change of the position of the detected element, the
Automatic calibration to achieve high precision detection
5) By marking directly on the PCB with ink or operating the display
Check the detection electricity with graphic error representation
Detectable components
Component type
-Rectangular chip element (0805 or larger)
-Cylindrical chip element
-Tantalum electrolytic capacitor
-Coil
-Transistor
-Platoon
-QFP，SOIC（0。4mm or more)
-Connector
-Special element
Testing items
No element: independent of PCB board type.
-Misaligned: (disengaged)
-Opposite polarity: component board is marked
Erect: programming settings
Welding failure: programming settings
-Component flipping: components have different features up and down
-Wrong post components: different features between components
Less tin: programming settings
-Kicking: Programming
Continuous welding: it can be detected 20 microns.
No solder: programming settings
Multi tin: programming settings
Factors affecting AOI examination results
External factors: chip quality; flux content; components; indoor temperature; welding quality.
Internal factors: AOI luminosity; machine temperature; graph analysis algorithm; mechanical system; camera temperature;
