A PCB label refers to the text and markings printed on a printed circuit board (PCB) to identify key attributes and aid in assembly and servicing. From part numbers to polarity indicators, labels enable clear recognition of board features and terminals.

PCB labels serve a variety of helpful functions:

• Part numbering for inventory management
• Pin mapping to assist insertion and soldering
• Branding and logos for product marking
• Board variant and revision data
• Power and I/O terminal indicators
• Regulatory compliance information
  • Certification marks
  • Date codes, serial numbers
• Operating parameters and warnings

With increasingly complex and compact PCBAs powering critical systems, clear and permanent labels constitute an indispensable aspect of robust product assembly and field servicing.

Types of Labels

There are two main types of labels used on PCBs:

Silk Screen Lables

Silk screen printed text utilizes epoxy ink layers applied directly to the PCB surface to create a permanent label. Since the process uses the same masked patterning as copper traces, it aligns precisely with board features and pads. This approach supports small text as well fine line work and shading such as logos.

Metal Foil Labels

Metal foil labels consist of thin aluminum plates etched with text and bonded to the PCB surface. They can withstand cleaning solvents which may degrade silk screen ink. Foil labels provide high contrast and durability, however minimum text size and spacing is larger than silk screen.

There are also various self-adhesive vinyl label options, but these tend to be less robust than the printed labeling methods above.

Next we’ll take a look at common PCB label implementations and their purpose.

Key Types of PCB Labels

Identifier Labels

Boards should minimally have a unique identifier label for tracking including:

• Part number – Used for inventory management, may encode options
• Revision – Distinguish versions and board changes
• Serial number – Identify individual boards in production

Identifier labels are essential for supply chain logistics as well as managing field replacements and upgrades.

Orientation Labels

Orientation labels denote board directionality to assist assembly and services. Common indicators include:

• “THIS SIDE UP” text
• “PIN 1” marker near alignment slot
• Rounded/beveled corner showing proper placement

Clearly conveying orientation prevents insertion errors which could damage boards or components during production.

Terminal Assignment Labels

Labels mapping board terminals to I/O functions helps identify connection points for wiring harnesses, cables or connectors during prototyping, test and field deployment.

Information often labeled includes:

• Power rails – GND, VCC markings
• Interface ports – USB, Ethernet, CAN etc.
• Pin counts – Labeled numerically

This labeling eliminates guesswork hooking up boards and ensures proper supply and signal connections.

Power Labels

Boards utilizing multiple voltage domains should identify domains and convey critical electrical constraints like:

• Operating voltage
• Maximum current
• Power sequencing
• ESD warnings

Conspicuous power rail labels help prevent damage from overvoltage or overcurrent.

Logo / Branding Labels

Logos, trademarks and company branding printed on the board provide product authentication and security. This deters counterfeiting and enables brand identification in the field.

Component Placement Labels

Labels mapping component locations is extremely helpful for manual assembly and rework. These often reference schematics or assembly diagrams.

Decorative Labels

Purely aesthetic labels can provide a professional appearance conveying quality. Common examples include decorative company name text and geometric corner motifs.

This summarizes common PCB label usage in products across industrial, medical, automotive, and consumer segments. We’ll now examine some best practices on label implementation.

PCB Labeling Best Practices

Effective application of PCB labels requires some design considerations:

Placement

• Position labels for visibility and access
  • Avoid component placement overlap
• Ensure orientation labels clearly visible
• Put near relevant features
  • Terminals, connectors, components
• Keep grouping consistent
  • Revision/branding in same area

Contrast

• White text on black works well
• Dark backgrounds with light text

Size

• Minimum 10 point (2.5mm) text height
• Increase size for important info
  • Power ratings etc.
• Decrease size for secondary data
  • Codes, logos

Text Format

• Use standard nomenclature
  • GND, VCC, Pin1 etc.
• Be concise but unambiguous
• Avoid text overload

Properly implementing labels using these guidelines ensures clarity forassemblers while providing vital data to field technicians.

Automated PCB Labeling

Manual label placement in PCB design tools often leads to overlooked information and inconsistent styling. Leading edge EDA software platforms like Altium Designer include advanced capabilities to assign labels automatically based on configurable rules.

For example, the following auto-labeling templates can be defined in Altium:

Power Rails Tabular Label

Parts Database Label

Custom Text Label

This automation simplifies incorporating vital identifiers, assembly instructions, ratings specifications and other text elements necessary for manufacturing and field deployment.

For further customization graphical objects can also be embedded into label primitives including lines, rectangles, circles and imported PNG images.

Labeling for Regulatory Compliance

Depending on product safety impact and target markets, PCBs may require certification marks and compliance labeling including:

• CE, UKCA – European Conformity
• UL, CSA – Safety standards
• FCC, ISED – EMI/EMC approvals
• RoHS – Hazardous substances

Other mandatory labels for production date codes, serial numbers, operating specs etc. may also apply per certification regimes. Regulatory requirements should be researched thoroughly based on jurisdictions covered.

Automated database-linked label rules streamline injection of up-to-date certification markings aligned to specific PCB designs and configurations.

Conclusion

In summary, PCB labels constitute a vital yet often overlooked product component serving diverse purposes from branding to assembly facilitation. Careful label design taking into account critical data needs, visibility, sizing and integration with the CAD toolflow results in maximum manufacturing and field serviceability.

Automation technology now readily exists to simplify the labeling process while reducing compliance risks. Given the accelerating complexity of modern electron mechanical goods, leveraging these advances provides real competitive advantage to producers.

Frequently Asked Questions

Q: How are PCB labels physically created?

A: The two main methods are silk screen printing using epoxy ink and metal foil etching. Silk screen enables small text and logos directly on the board surface. Foil provides high contrast and durability. Labels get applied during board fabrication.

Q: Should PCB labels use a standard format?

A: Using common nomenclature like “Pin 1”, “GND”, positive/negative symbols etc. helps ensure universal understanding. But allowing some customization also enables optimized callouts for product-specific architectures.

Q: Can PCB labels be added post-production?

A: Yes, manual adhesive labels can be used albeit with less robustness over molded text. Reworking boards to add silk screen or metal foil labels is also possible but much more complicated. Best practice is to finalize all labels during the engineering stage.

Q: What label content is most helpful for field repairs?

A: Part numbers, revision, branding, power ratings, terminal assignments, voltage domains, component locations are key for technicians troubleshooting and servicing boards. Silk screens of the PCB assembly and schematic drawings are also extremely helpful.

Q: Do all certification marks required need to go on the PCB label?

A: Any markings integral to PCB construction should be included, but certifications primarily related to the full product enclosure can be satisfied on the exterior housing assuming it remains fixed. Research applicable regulations to determine proper label placement.