Automated Visual Inspection (AVI)

Automated Visual Inspection (AVI) is a relatively new process that visually inspects the final bare PCB before being assembled.   The AVI process removes the human factor in the final inspection step.  However, there are many experienced human inspectors who can determine an acceptable board or rejectable board faster than an AVI machine.  The AVI machine when setup adequately can consistently give the same inspection board by board or lot by lot.  All PCBs are accepted or rejected with the same algorithm. 

AVI, automated visual inspection is an automated vision inspection of PCB is performed in one of the final steps before the PCB are shipped to the assembler or are assembled.  After scanning by an AVI machine, the defects which do not meet the manufacturer’s requirement will be identified by the machine.  Therefore, AVI will increase the quality/cosmetic quality of PCBs.

About the AVI Machines

The basic principles of the AVI machines are to have a motion system in combination with a camera and specialized software. AVI machines take advantage of colour cameras and led lights. Modern AVIs use a conveyor to transport the PCB into the machine and have cameras on the top and bottom side to inspect both sides of the PCB at the same time.

The Camera

On all AVI machines, colour is an important concern as it is used for cosmetic inspection. They must detect some contamination or discoloration on PCBs, so color cameras are more commonly used than monochrome camera for AOI machines.

In digital imaging, a pixel (or picture element) is a single point in a rasterized image. The pixel is the smallest addressable screen element; it is the smallest unit of picture that can be controlled. Each pixel has its own address. The address of a pixel corresponds to its coordinates. Pixels are normally arranged in a two-dimensional grid and are often represented using dots or squares. Each pixel is a sample of an original image; more samples typically provide more accurate representations of the original.

The intensity of each pixel is variable. In color image systems, a color is typically represented by three or four component intensities such as red, green, and blue, or cyan, magenta, yellow, and black.

The number of pixels is also an important parameter of cameras. Larger number of pixels does not mean it can detect smaller defects. To detect smaller defects, smaller pixel size is required.  Pixel size is calculated by scan width / number of pixels. For example, the scan width is 2 inches and number of pixels of camera is 2000. Pixel size =2 inches/2000 = 1mil. Some machines use cameras with fewer pixels.  But they can use more cameras to compensate for it.  Normally the exposure time for more pixels CCD is longer. So, the scanning time of more pixels CCDs is longer too.  Therefore, some machines use multiple CCDs with less pixels rather than using one camera with more pixels.

Detecting Defects

For AVI, the main two factors that determine whether the defects can be identified are the size and brightness/color of defects.  The pixel size of the AVI machine determines the minimum size of defects it can detect.  The pixel size can be seen as the basic unit of the scanned image.  Therefore, the minimum defect size detectable must be larger or equal to pixel size.  But even if the defect size is the same as the pixel size, the defect might be very difficult to detect.  For example, in the following case, defect size is same as pixel size.

For case A, it is the best situation where the defect is inside the pixel, so the defect is easily detectable.  For case B, it is the worst situation as each of the four pixels can only see the 25% of the defect, so it may not detect the defect.  Therefore, if the defect size is very small and is close to the pixel size, then it may not be detected by the machine.

Case for defect size equal to pixel size

Another factor which makes the defect difficult to detect is brightness/color of defect.  If the brightness/color of the defects is close to normal area, then it will be difficult for the machine to detect the defects.  The common missing defects on AOI and AVI are scratches and dents. 

Blue– Missing pad area

Red– Scratch on gold surface

Gold- Open under the mask

 

Case for defect size equal to pixel size

A verification station is used offline to the AOI to verify or repair defects.

Why Gardien’s Solution?

Your Gardien Local Service Centre may offer this service.  The AOI tooling and production services are controlled by Gardien’s proprietary job flow system called Ontrack (link to Ontrack).   This creates a seamless and error free flow of information from the customer supplied data to the Service Floors at Gardien.

Gardien’s team is trained and qualified on all internal process as documented Quality Management System.  The internal process has specific inputs for incoming, certified, and not good boards as well as descriptive educational programs on various board types, and surface finishes. 

Gardien certifies each order processed with a Certificate of Compliance with details about how the order was processed, what specifications were used to certify the product, equipment used with calibration expiry date, team member who processed the order, quantity, and failure analysis.

Gardien strongly recommends that the test sequence and parameters are clearly stated on the manufacturing drawing or at a minimum agreed upon during the quoting or contract realization phase.    In addition, any PCB sent to us for processing should have a unique identifier on each peace for electronic traceability.

KEVIN SYVRET

FINANCE DIRECTOR, NORTH AMERICA

Mr. Syvret joined Gardien Services Canada as Financial Controller in 2001 and assumed the role of Finance Director North America in 2007. Over the past 20 years, Mr. Syvret has held senior finance and accounting roles, including with Canadian Pacific Ltd and Sprint Inc.

NIRAJ PATEL

VICE PRESIDENT, GARDIEN NORTH AMERICA

Mr. Niraj Patel joined the company on a part time basis in 1993 while attending college full time. He worked in various positions until he graduated from the Centennial College Computer Systems Technology program, whereupon he was hired full time. He progressed through several testing and CAM department positions and was appointed North American CAM Manager in 1998. After 18 years with the company, Mr. Patel was promoted to Senior Vice President of Operations, Gardien Services Canada Inc. in 2011. In January, 2015 Mr. Patel became Vice President NA of the newly combined organizational unit North America which includes the Canada and USA.

TODD KOLMODIN

VICE PRESIDENT QUALITY, NORTH AMERICA

Mr. Todd Kolmodin, a native to the Pacific Northwest was born in Seattle Washington. At a young age he moved to the Portland Oregon area. In March of 1986 he graduated from ITT Technical Institute with a degree in Electronics Engineering Technology. Todd began his tenure in the Electrical Test field that same year.  Todd spent eight years working in an independent testing facility in Wilsonville Oregon where he built skills in all aspects of Electrical Test and Quality Assurance. 

Todd then spent a short term with Yamamoto Corporation on their Engineering staff covering PCB drill, finishing and Electrical Test before joining Probe Test Fixtures in 1995. His charge was CAM and Fixuring Manager.  Todd joined the Gardien Group in September 1998 continuing the same roll and taking on the responsibilities of Quality Manager for Oregon operations. In 2008 Mr. Kolmodin was promoted to Vice President Quality USA. In this position Mr. Kolmodin oversees and maintains the Gardien ITAR registration, ISO Multi-Site registration and multiple site Lab Suitability with the Defense Logistics Agency Land and Maritime. Now also maintaining the Gardien QMS system Todd now serves as Vice President Quality North America.

Mr. Kolmodin is also a published columnist and Technical Presenter with multiple appearances at the IPC Apex Expo Conferences in both San Diego and Las Vegas. 

ROLAND VALENTINI

CHIEF OPERATING OFFICER

Mr. Valentini was appointed COO in July 2010 after successfully serving as head of North American operations since 2005.

Roland has over ten years’ experience in the PCB industry, including sales, service, and project management at Atotech GmbH, Germany mainly relating to PCB plating equipment.
He has significant sales experience from his tenure at Mack Rides GmbH and headed up worldwide installations for Lurgi Bischoff GmbH.

Mr. Valentini received a Master’s Degree in Mechanical Engineering from the University of Mannheim, Germany.

RICHARD HORSMAN

EXECUTIVE CHAIRMAN

Prior to Richard joining Gardien in September 2014, he was Chairman/CEO of tool chain vendor Atego Group Systems Limited which was sold to PTC Inc.

Prior to joining Atego, Richard held a number of Executive and Non-Executive roles including Senior Independent Non-Executive Director of Plethora Solutions, an AIM listed Pharmaceutical Company and CEO of AIM listed Cybit Holdings plc. where he grew the company from inception to revenues of over 25 million and took the company through multiple acquisitions before managing a sale of the business to Francisco Partners.

Richard previously held a number of senior roles in the Software industry.

RICK MERAW

GROUP VICE PRESIDENT QUALITY

Mr. Meraw was appointed Group Vice President of Quality in Jan 2015 after successfully  serving as Senior Vice President of USA operations since 2011.  Prior to being responsible for USA operations Mr Meraw was responsible for Canadian operations since 2001.

Rick has over twenty years’ experience with Gardien Group and has various roles including, service technician, customer liaison, Quality manager, technical support, project management, and software design/ implementation.

In June 1992 he graduated with an Electronic Engineering Technologist degree, with honors from a local community college.

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Our People

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+65 6225 2238

info.group@gardien.com

ROLAND VALENTINI

CHIEF OPERATING OFFICER

Mr. Valentini was appointed COO in July 2010 after successfully serving as head of North American operations since 2005.

Roland has over ten years’ experience in the PCB industry, including sales, service, and project management at Atotech GmbH, Germany mainly relating to PCB plating equipment.
He has significant sales experience from his tenure at Mack Rides GmbH and headed up worldwide installations for Lurgi Bischoff GmbH.

Mr. Valentini received a Master’s Degree in Mechanical Engineering from the University of Mannheim, Germany.