PCB Optical Inspection: Usage and Methods

March 12, 2020 , in Blog

There used to be a time when kids wearing glasses were subject to ridicule by their peers. As a result, some young people would put themselves at risk of not clearly recognizing obstacles, such as doors, that may lead to injury. Fortunately, our views toward allowing children to “pick on” or, in a more intense form, bully others have changed. Greater societal acceptance, advances in technology, and even changes in fashion have all contributed to the virtual elimination of the stigma of wearing glasses. Today, the ability to see far outweighs the method or mechanism by which that sight is accomplished.

Using optical inspection on a circuit board

Using AOI on a PCBA

Fortunately, this same wisdom prevails in the building of PCBs and PCBAs. The primary objective of circuit board development and production is a finished product that is able to meet performance objectives, reliably, over the projected lifecycle of the board. In other words, quality is the most important criterion, and this cannot be achieved in the presence of substantial defect(s). Although some defects can be detected manually, such as severe deformity or breakage, many cannot. In order to inspect and identify small or interior problems, the circuit board construction process uses PCB optical inspection. Let’s investigate this invaluable tool for PCB manufacturing and explore how its utilization can contribute to the quality of your board.

What is PCB Optical Inspection?

Quite simply, PCB optical inspection is the use of a camera to inspect a printed circuit board. However, this is not the whole story, and where and how the cameras are used can vary from contract manufacturer (CM) to CM. The most common utilization is automated optical inspection (AOI), which is performed during board assembly to inspect solder joint quality, component shifts, tombstoning and other issues that may require rework. In the event that soldering issues are detected, then rework is performed by skilled technicians on individual boards, as needed. If the issue displays a repetitive pattern or occurs consistently, then a more comprehensive solution is warranted, which may already be dictated by the CM’s risk management protocols or may need to be newly devised.

The effectiveness of AOI is dependent upon the type of equipment used, available capabilities, and integration into the PCB manufacturing process. Depending upon the CM’s operations, equipment may range from a single isolated device that is used to sample test boards to multiple machines strategically located at various points or steps during manufacturing to analyze board quality throughout the fabrication and/or assembly stages. For more advanced PCBA manufacturing facilities, AOI is combined with software to improve quality as well as provide automation and augmentation for smarter circuit board construction.

How PCB Optical Inspection Can Improve Board Quality

There are many quality control options that CMs may employ during manufacturing. However, AOI is one of the most effective, as it can identify many defects that would otherwise go undetected. In fact, this testing method may even be utilized to compare the actual board with the idealized CAD design generated by PCB design software. Below is a listing of some of the uses for AOI that can be used to optimize the quality of your fabricated and assembled board.

PCB Optical Inspection Identification Usage

During Fabrication

  • Trace violations
      • Width inconsistency
      • Incorrect copper weights
      • Broken traces
  • Spacing violations
  • Drill hole errors
      • Inadequate annular ring diameter
      • Offset holes
  • Lamination problems
  • Incorrect or missing labels or reference indicators
  • Pad or footprint damage

During Assembly

  • Solder bridging
  • Bad solder joints
  • Tombstoning
  • Incorrect component orientation
  • Insufficient solder relief
  • Missing solder paste
  • Damaged components
  • Contamination
  • Component verification (identification of counterfeit components)

The list above, although extensive, does not include all of the possible uses for AOI. It does, however, demonstrate the importance of this testing tool for ensuring board quality.

Reliability in operation is the most important metric by which your boards are evaluated. And this can only be achieved by your CM employing quality control methods that ensure your PCBAs meet the manufacturing standards to meet this goal. Of all the quality control methods your CM might utilize, PCB optical inspection is probably the most valuable procedure.

Tempo's Custom PCB Manufacturing Service
  • ISO-9001, IPC-600, and IPC-610 commitment to quality certifications.
  • Execute your full development cycle from proto to validation, NPI, and low volume production.
  • Accurate quote in less than a day.
  • Performs entire turnkey process in as fast as 4 days.
  • DFX support, including DFM, DFA, and DFT from Day 1 of design.
  • Sources components from the most reputable suppliers in the industry. to reduce procurement time.
  • Software-driven smart factory with monitoring and control throughout the manufacturing process.
  • Performs multiple automated inspections during PCB assembly to ensure PCB quality for prototyping.
  • Smooth transition from prototyping to production.

Tempo Automation is the industry leader for fast, high-quality prototyping and low-volume production of circuit boards and we employ PCB optical inspection throughout the manufacturing process to ensure your boards will meet your objectives.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on PCB optical inspection or how it can be used to improve your board quality, contact us.

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