Whenever former U.S. President Ronald Reagan spoke publicly, he typically cited a poignant anecdote. One of the most famous ones was “Trust, but verify.” He was, of course, referring to his handling of foreign nations at the time. However, Reagan’s motto is still highly applicable and can be implemented in the realm of modern electronics production.
The process of building or constructing circuit boards is a two-stage process that consists of fabrication and assembly. During fabrication, the basic PCB structure is created. Assembly consists of soldering the components, testing, and then inspecting the overall PCBA. The range of possible circuit board test regimens that validate the quality of the manufacturing process is extensive and may vary depending on the design and intended application of the board. PCB inspection, however, is an essential aspect of all board spins.
PCB Testing vs PCB Inspection
What is the difference between testing and inspecting PCBs and PCB assemblies, exactly? The following definitions can help you distinguish between the two.
|PCB testing describes the utilization of equipment to assess a physical property or characteristic of the circuit board structure. Bend radius, peel pressure, and characteristic impedance determinations—measured using a time domain reflectometer (TDR)—are examples of PCB structural testing.|
|PCB inspection, which is more accurately termed PCBA inspection, is commonly used to describe the manual and automated inspection techniques and methods where the board’s assembly is evaluated for solder bridging, bad solder joint quality, component placement-footprint layout, pad-trace misalignments, or other failure modes.|
The specific tests performed may be dictated by the developer or required by certain standards and regulations. For example, aerospace electronics may need to undergo highly accelerated life testing (HALT). The same is true for PCB inspections, which fall into one of two general types and have performance criteria defined in IPC standards A-610 and J-STD-001.
DFM for HDI Printed Circuit Boards
Circuit Board Inspection Types
As stated above, the purpose of inspecting boards is primarily to identify failure modes. However, there are additional benefits. For example, consistent inspection can be a predictor of potential failures as well. The degradation of quality over time, even if still within acceptable limits, is a strong indicator that some process adjustments are necessary. Inspections also provide accurate data for PCB yield determinations This design validation is a critical part of an optimal design development checklist and should make use of both manual and automated PCB inspection methods.
PCB Inspection Types
Manual board inspection is the visual evaluation of a PCBA with the naked eye or some other optical equipment. Commonly used tools include cameras and microscopes that provide high resolutions. The advantage of this type of inspection is that it enables technicians or quality control personnel to target specific areas or components of the board.
Although manual inspection should be utilized, it is not a substitute for automation. By automating the inspection process, manufacturing can achieve the accelerated turnaround times that are required to reach optimal quality during prototype development. The automated process, referred to as automated optical inspection (AOI), employs image processing and software to provide high-level pictures of internal connectivity and vias of the PCBA.
|Tempo's Custom PCB Manufacturing Service
PCB inspection is an essential element of the PCB assembly process as it can ensure quality and validate the level of quality control of the manufacturing process. At Tempo Automation, the industry leader in high-quality PCBA prototyping and on-demand production, we employ both automated and manual inspections throughout the board building process to minimize failure mode risks, optimize yield rates, improve efficiency, and maximize ROI.
And to help you get started on the best path, we furnish information for your DFM checks to avoid delays and ensure manufacturability. 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 provide 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 CAD files or how to incorporate your design into a CAD format, contact us.