A famous postulate in quantum mechanics asserts that it is impossible to know a particle's exact position and speed simultaneously. The importance of the Heisenberg Uncertainty Principle—named after Dr. Werner Heisenberg who proposed it in 1927—is profound because it places a limitation on the degree of accuracy that can be obtained from direct measurement of the fundamental building blocks for all systems where motion exists, which includes electrons, the active particle in electronics. A more simplistic way to interpret this is that room for error always exists.
This principle holds for all electronics systems; however, from a macroscopic perspective, the effect is negligible. As a result, we can design circuit boards and develop manufacturing processes that have no appreciable error. One way to accomplish this level of near perfection is to employ an error-proofing or poka-yoke strategy to the board building process. Knowing the advantages and disadvantages of poka-yoke in manufacturing will enable the best application for PCBA development.
Poka-Yoke: Pros and Cons
The term poka-yoke was developed at Toyota in the 1960s in an effort to develop a strategy to avoid mistakes in the manufacturing process. The intent is to ensure that the correct conditions exist to avoid mistakes prior to proceeding with a process step whenever possible. In the event this cannot be done, the goal is to identify any error as soon as possible so that it can be corrected. In this regard, poka-yoke resembles a risk management strategy. Although typically associated with lean manufacturing, poka-yoke is not application-specific and has its advantages and disadvantages.
Error Targets for Poka-Yoke
- Component errors
For PCB assembly (PCBA), not having the correct component is a critical error that can result in misaligned pads and traces, open circuits or other common failures that affect operation and reliability.
- Setup errors
Improper setup should not be an issue for typical board builds; however, for In-Circuit Tests (ICTs), misaligned test points could render an expensive and time-consuming process ineffective.
- Operations errors
This is likely an issue for manufacturing steps that depend heavily upon the technician or operator's expertise for successful execution.
- Processing errors
Processing errors are particularly concerning for automated or programmed PCBA manufacturing steps.
- Measurement errors
Aside from impedance control and contamination minimization, automated optical inspection (AOI) is perhaps more important than measurement for PCBA manufacturing. This QA technique is essential for discovering component and process errors that would otherwise go undetected.
Prevention or early detection of the types of errors listed above highlights the advantages of implementing a poka-yoke strategy. Yet, some disadvantages should be considered.
The underlying motivation for using a poka-yoke method is the recognition that humans make mistakes, especially when performing repetitive processes. Therefore, the goal is to eliminate or minimize opportunities for these mistakes. Such actions, however, can sometimes have unintended consequences. For example, eliminating the need for an operator to perform routine checks may result in an obvious error being overlooked. Additionally, if the poka-yoke measure is not well-designed, it may reduce efficiency and increase costs unnecessarily. To assure that your implementation is beneficial and does not work against your PCBA development optimization, a few best practices should be followed.
How to Best Utilize Poka Yoke in PCB Manufacturing
Poka-yoke is as much a perspective as it is a set of concrete actions. The actions are application-specific and may vary in detail among CMs; however, a process based on high-level quality control must be instituted and adopted to ensure success. This is best accomplished by following the guidelines below.
Best Practices for Using Poka-Yoke in Manufacturing
- Ensure your CM is committed to QC
Employing poka-yoke indicates a commitment to high-level QC, which should be a primary factor for selecting a CM for your PCBA manufacturing.
- Collaborate with your CM
The importance of working closely with your CM to ensure that your design intent is incorporated and that your design promotes efficient manufacturing cannot be overemphasized.
- Optimize your design for manufacturing
More than any other, PCBA manufacturing influences development efficiency. Therefore, it is important that your design process aids your CM by avoiding common layout mistakes that can extend turnaround times.
The PCB Design Development Checklist
The key to effectively utilizing poka-yoke in board development is to know how to leverage its advantages and avoid the disadvantages to optimize your manufacturing and new product introduction (NPI) process.
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Testing is one of the major stages of PCBA development that is required to ensure that your boards adhere to the performance and operational expectations for which they were designed and built. If this testing must be outsourced, working with a CM that employs a digital PCB manufacturing process, as we do at Tempo Automation, can save you time and money while providing the flexibility to easily and quickly make any necessary changes to meet your design 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.