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Dana on Data: Best Practices in Interpreting Drawing Notes—‘Use Latest Revision’

The global nature of electronics manufacturing requires clear, consistent, and precise communication, particularly in technical documentation. An area where miscommunication often arises is in interpreting drawing notes—small lines of text with the potential to dramatically impact product quality, manufacturing efficiency, and customer satisfaction.

I returned from a week-long visit to our factory in Huizhou, China, where I gained firsthand insight into these challenges. Observing highly skilled front-end engineers as they navigated drawings in various English dialects underscored the importance of clarity. A single misread or overlooked note can mean costly scrap, rework, or, even worse, an unsatisfied customer.

This article is the first in a series on common drawing notes and how interpreting them can significantly affect the manufacturing process. We will start by examining one of the most frequently encountered and deceptively simple directives: “Use latest revision of IPC-6012.”

The Evolution of Specification Referencing
In the early days of PCB design, it was standard practice to specify the exact revision of a referenced standard in the drawing notes, for example: “IPC-6012B.” While this ensured clarity at the time of release, it introduced a downstream problem. The updating and revising of specifications over a product’s lifecycle resulted in existing drawings referencing outdated, or “down revision,” standards. This forced designers into a dilemma: Update every affected drawing, or risk using obsolete requirements.

To streamline this process, the industry gradually  the revision letter or number, opting for notes such as “Use latest revision of IPC-XXXX.” The intention was that manufacturers would always build to the most current version of the specification unless otherwise directed.

However, reality proved more nuanced. Many high-reliability electronics companies instituted internal review processes before adopting new or revised specifications to assess the impact on their products and compliance requirements. PCB fabricators themselves often perform similar reviews to determine how changes may affect their processes and quality standards. As a result, implementation of a new specification revision might be immediate for some. In contrast, for others, it could be delayed for months as the change works through internal procedures.

The Role of the Global Electronics Association in Revision Control
To some extent, the Global Electronics Association dictates when to apply a new revision. Each revision’s cover sheet states that it supersedes the prior version and typically identifies the previous revision and document number. Nonetheless, the timing of adoption still depends on both the customer’s and fabricator’s readiness and approval processes.

How Frequently Do IPC Specifications Change?
IPC specification revisions are relatively infrequent. An analysis performed in February 2024 revealed:

• 30% of IPC specifications were last changed or released in the previous century
• 19% have been released or modified in the current decade
• IPC-6012, specifically, has undergone three revisions or amendments since 2020, with another revision actively in progress

This pattern of infrequent but occasionally significant updates underscores the importance of monitoring standards and maintaining internal review processes.

When Should New Revisions Be Implemented?
There are many life-cycle stages between initial prototype fabrication and assembly through to obsolescence. The Association does not provide guidance on when to update the board with the new revision during its lifecycle. PCB fabricators and assembly houses are often left to decide when to apply the new version. What are your company’s rules? Here are some examples:

Case 1: The IPC specification does not change revision after tooling through assembly QA. In this case, use revision A.

Case 2: Revision changes occur after tooling the PCB and releasing it to production. Fabrication engineering and assembly tooling, occurring in parallel, use revision A, but Final QA will have revision B in the system. The drawing says to use the current revision. Should QA use the down revision or the new revision?

Case 3: The revision changes after the PCB has been tooled and fabricated. EMS doesn’t assemble the PCB until the release of revision B. The drawing states to use the current revision. Should EMS use the down revision or the new revision?

Case 4: Production is running for 2025 and 2026 with no changes in the referenced IPC specifications. Everyone uses revision A.

Case 5: Production is running in 2025. The OEM adds a new fabrication source in 2026. The specification revision changed in 2026. Now, Supplier #1 is using the 2025 revision, and Supplier #2 is using the new revision. Which revision should the EMS company use for its assembly in 2026? Do they allow both revisions, or do they require supplier #1 to update the PCB to the new revision? 

There are many more permutations of when to apply new specification revisions. Updating existing part numbers to newer revisions may change the PCB functionality, reliability, assembly yield, etc. There will be additional costs for the suppliers to update their products, documentation, and test fixtures, as well as resources that may be required by the OEM to validate the medication impacts.

Key Takeaways

• If designers and manufacturers don’t clearly define internal processes, drawing notes referencing the “latest revision” of a standard can become ambiguous.
• The industry shifted from referencing specific revisions to using generic language to reduce overhead, but this requires review and communication at each specification update.
• Customers and PCB fabricators must maintain internal processes to assess the impact of new standards before implementation.
• IPC standards, while not frequently updated, do evolve, and staying informed is essential for compliance and product reliability.

In future articles, we will explore additional drawing notes that pose similar challenges, offering strategies to improve clarity and minimize costly misinterpretation in global manufacturing environments.

Dana Korf is the principal consultant at Korf Consultancy LLC.