Automated optical inspection (AOI) is an automated
visual inspection
Visual inspection is a common method of quality control, data acquisition, and data analysis.
Visual Inspection, used in maintenance of facilities, mean inspection of equipment and structures using either or all of raw human senses such as vision, ...
of
printed circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...
(PCB) (or
LCD,
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
) manufacture where a
camera
A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with ...
autonomously scans the device under test for both
catastrophic failure
A catastrophic failure is a sudden and total failure from which recovery is impossible. Catastrophic failures often lead to cascading systems failure. The term is most commonly used for structural failures, but has often been extended to many oth ...
(e.g. missing component) and
quality defects (e.g. fillet size or shape or component skew). It is commonly used in the manufacturing process because it is a non-contact test method. It is implemented at many stages through the manufacturing process including bare board inspection, solder paste inspection (SPI), pre-reflow and post-reflow as well as other stages.
Historically, the primary place for AOI systems has been after solder reflow or "post-production." Mainly because, post-reflow AOI systems can inspect for most types of defects (component placement, solder shorts, missing solder, etc.) at one place in the line with one single system. In this way the faulty boards are reworked and the other boards are sent to the next process stage.
SMT inspection
AOIs for a PCB board with components may inspect the following features:
* Area defects
* Billboarding
* Component offset
* Component polarity
* Component presence or absence
* Component Skew
* Excessive Solder Joints
* Flipped component
* Height Defects
* Insufficient Paste around Leads
* Insufficient Solder Joints
* Lifted Leads
* No Population tests
* Paste Registration
* Severely Damaged Components
* Tombstoning
* Volume Defects
* Wrong Part
* Solder Bridging
* Presence of Foreign Material on the board
AOI can be used in the following locations in the
SMT lines: post paste, pre-reflow, post-reflow, or wave areas.
Bare PCB inspection
AOI for a bare PCB board inspection may detect these features:
* Line width violations
* Spacing violation
* Excess copper
* Missing pad – a feature that should be on the board is missing
* Short circuits
* Gold Finger damage
* Cuts
* Hole breakage – a drilled hole (via) is outside of its landing pad
* Wrong mounting components identified
The triggering of a defects report may be either rule-based (e.g. no lines on the board should be smaller than 50μ) or CAD based in which the board is locally compared with the intended design.
This inspection is much more reliable and repeatable than manual visual inspection.
In many cases, smaller circuit board designs are driving up the demand for AOI vs in-circuit testing.
Related technologies
The following are related technologies and are also used in electronic production to test for the correct operation of electronics printed circuit boards:
Zentroid
- PCB/CAD/AOI Basics, Component and Package names
* Automated x-ray inspection
Automated inspection (AXI) is a technology based on the same principles as automated optical inspection (AOI). It uses as its source, instead of visible light, to automatically inspect features, which are typically hidden from view.
Automated ...
(AXI)
* Joint Test Action Group
JTAG (named after the Joint Test Action Group which codified it) is an industry standard for verifying designs and testing printed circuit boards after manufacture.
JTAG implements standards for on-chip instrumentation in electronic design auto ...
(JTAG)
* In-circuit test
In-circuit testing (ICT) is an example of white box testing where an electrical probe tests a populated printed circuit board (PCB), checking for shorts, opens, resistance, capacitance, and other basic quantities which will show whether the assemb ...
(ICT)
* Functional testing
See also
*Object recognition
Object recognition – technology in the field of computer vision for finding and identifying objects in an image or video sequence. Humans recognize a multitude of objects in images with little effort, despite the fact that the image of the ...
*Machine vision
Machine vision (MV) is the technology and methods used to provide imaging-based automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry. Machine vision refers to ...
*Automated X-ray inspection
Automated inspection (AXI) is a technology based on the same principles as automated optical inspection (AOI). It uses as its source, instead of visible light, to automatically inspect features, which are typically hidden from view.
Automated ...
*Under vehicle inspection An under-vehicle inspection (UVI) system generally consists of imaging systems mounted on a roadway and used at facility access points, particularly at secure facilities. An under-vehicle inspection system is used to detect threats—such as bombs†...
References
{{reflist
Hardware testing
4. Automated Optical Inspection (AOI) Equipment List
Applications of computer vision
Printed circuit board manufacturing
Nondestructive testing