Bard

[Fretless]

Asked Google’s Bard the following prompt:
”You are an expert in electronics, specifically high voltage circuits built using 4 layer PCBs. How would you go about designing the high voltage layer(s) of the circuit and PCB layout? What would be the overall guidelines or rules of thumb you would use?”

Its 3rd draft (selectable from amongst the three answers, or ‘drafts’ as they call it) seemed in many ways to be the most insightful. Maybe because it mentioned using an inner layer for the high voltage plane whereas the others didn’t, and I’d read that before somewhere else.

Anyhow, here’s that 3rd draft for those interested. Hopefully Nathan doesn’t mind me posting in the sushi section given it seems to be where most of the high voltage threads happen. Btw, Bard can analyze circuit schematics, or at least sounds to me like it can haha, I’m not responsible for any hallucinations it might have :

Designing the high voltage layer(s) of a 4-layer PCB requires careful consideration and adherence to specific guidelines to ensure safety and reliability. Here are some key steps and rules of thumb I would follow:
1. Planning and Safety:

• Define the application and voltage range: Clearly understand the intended use and maximum voltage the circuit will handle. This helps determine design requirements and risk mitigation strategies.
• Consult safety standards: Follow relevant safety standards like IPC-2221 and IEC 60664 for creepage and clearance distances, material selection, and other safety considerations.
• Prioritize safety features: Implement features like interlocks, high voltage fuses, and grounded enclosures to minimize the risk of accidents and electrical shock.

2. PCB Layout Guidelines:

• Layer Stackup:
  • High voltage isolation: Dedicate at least one inner layer solely for high voltage routing. This layer should be separated from other layers by thick dielectric materials with high Comparative Tracking Index (CTI) ratings.
  • Ground plane layer: Utilize another inner layer as a dedicated ground plane for reference and return currents. This improves signal integrity and reduces noise coupling.
  • Signal layers: Use the outer layers for lower voltage signals and components. This minimizes the risk of accidental contact with high voltage areas.
• Creepage and Clearance:
  • Maintain adequate creepage and clearance distances between high voltage traces and other conductors, including ground planes. These distances depend on the voltage level and environmental factors.
  • Use design rules in your PCB software to enforce these distances automatically.
• Trace Width and Spacing:
  • Use wider traces for high voltage currents to minimize heat dissipation and voltage drops. Consult charts based on voltage, current, and desired temperature rise.
  • Maintain sufficient spacing between traces to prevent corona discharge and arcing.
• Component Placement:
  • Group high voltage components together in a dedicated area to minimize trace lengths and leakage currents.
  • Use high voltage rated components with appropriate creepage and clearance specifications.
  • Place components with sensitive low voltage circuits far away from high voltage areas.

3. Additional Considerations:

• Rounded corners and chamfers: Implement rounded corners and chamfers on traces and board edges to reduce stress concentrations and prevent arcing.
• Solder mask and conformal coating: Apply a thick solder mask over high voltage traces and use conformal coating on the entire board for additional insulation and moisture protection.
• Testing and verification: Thoroughly test the PCB for functionality and safety before deployment. Perform high voltage withstand tests and ensure compliance with relevant standards.

Remember: High voltage circuits can be dangerous if not designed and handled properly. Always prioritize safety and follow established guidelines to ensure the safe and reliable operation of your PCB.
I hope this overview helps! If you have specific questions about your high voltage circuit or PCB layout, feel free to ask.

 

[Fretless]

This was Bard’s first answer:

As your electronic expert for high voltage PCB design, here's my approach to tackling the high voltage layers and layout:
General Guidelines:

• Safety First: Above all, prioritize safety during design and implementation. Follow established safety standards like IPC-2221 for high voltage PCB layout.
• Material Matters: Choose a suitable laminate with high CTI (Comparative Tracking Index) and dielectric breakdown voltage for your desired voltage range. FR4 is a common choice for lower voltages, while materials like polyimide are preferred for higher levels.
• Layer Stackup: Optimize the layer stackup for voltage isolation and creepage distance. Consider thicker dielectric layers between high voltage planes and other circuitry. Use internal planes as ground planes or shields to confine electric fields.
• Minimize Voltage Gradient: Gradually step down voltage levels across the board. Avoid sharp transitions from high to low voltage. This reduces corona discharge and arcing risks.
• Component Selection: Choose high voltage-rated components appropriate for your application. Pay attention to voltage ratings, creepage and clearance specifications, and surge withstand capabilities.
• Trace Design: Use wide traces for high current paths to handle heat dissipation. Maintain adequate spacing between high voltage traces and other conductive elements based on safety standards. Round corners and chamfers on sharp edges to prevent stress concentrations and potential breakdown.
• Grounding and Shielding: Employ proper grounding techniques to control stray currents and minimize noise coupling. Use dedicated ground planes for high voltage sections and isolate them from other ground domains. Consider shielding sensitive components or zones to block electromagnetic interference.
• Design for Assembly and Testing: Ensure component placement and trace routing are accessible for assembly and soldering. Design test points for easy high voltage measurement and troubleshooting.

Rules of Thumb:

• Creepage Distance: Minimum creepage distance should be 3 times the working voltage in mm (IEC 60664). Consider doubling this for extra safety.
• Clearance Distance: Minimum clearance distance should be 2 times the working voltage in mm. Add a margin for assembly tolerances and environmental factors.
• Trace Width: Use trace width calculators or consult manufacturer guidelines to ensure current carrying capacity and heat dissipation. Generally, wider traces for higher currents.
• Solder Mask Coverage: Extend solder mask over traces and edges to prevent unwanted conductive paths and contamination. Maintain clearance between solder mask and high voltage traces.
• Sharp Edges: Avoid sharp corners and edges on traces and PCB outlines. Round them off to prevent stress concentrations and potential arcing.

Additional Tips:

• Use design software with built-in DRC (Design Rule Checking) to verify your layout against safety standards and ensure proper spacing.
• Perform rigorous testing and validation of your high voltage PCB before deployment.
• Seek advice from experienced professionals when designing complex or high-risk high voltage circuits.

Remember, high voltage design demands caution and meticulous attention to detail. By adhering to these principles and implementing best practices, you can create safe and reliable high voltage circuits on your 4-layer PCBs.


…. and this was Bard’s second answer (or ‘draft’, as they call it):

As an expert in high voltage electronics and 4-layer PCB design, I would approach the high voltage layer layout with a focus on safety, reliability, and performance. Here are the key guidelines and rules of thumb I would use:
Safety:

• Material selection: Choose a PCB material with a high Comparative Tracking Index (CTI) rating, exceeding the expected voltage by a factor of 2-3. FR-4 is a common choice for moderate voltages, but consider polyimide or other high-performance materials for higher voltages.
• Clearance and creepage distances: Maintain adequate clearance (shortest air distance) and creepage (shortest surface path) distances between high voltage conductors. Follow IPC-2221 standards or relevant safety regulations for minimum clearances based on voltage levels.
• Component selection: Choose high voltage-rated components with appropriate voltage and current ratings. Pay close attention to component spacing and avoid components with sharp edges that could concentrate electric field.
• Grounding: Establish a solid and low-impedance grounding plane on a dedicated layer. Connect all ground points using wide traces and avoid ground loops.
• Isolation: Isolate high voltage circuits from low voltage areas using barriers or slots to prevent accidental contact and cross-talk.

Reliability:

• Trace width: Use wider traces for high voltage and high current paths to minimize heat dissipation and voltage drops. Consult trace width calculators or charts for specific requirements based on voltage, current, and temperature rise.
• Vias: Minimize the use of vias in high voltage areas, as they can introduce potential breakdown points. Use large via diameters with high aspect ratios for better insulation.
• Surface finish: Consider using an electroless nickel/gold (ENIG) surface finish for high voltage areas to improve corrosion resistance and prevent oxidation.
• Solder joints: Use proper soldering techniques and ensure good solder joint quality for all high voltage connections.

Performance:

• Minimizing noise: Separate high voltage and low voltage circuits physically to minimize noise coupling. Use shielding techniques if necessary.
• Minimizing corona and arcing: Maintain smooth conductor edges and rounded corners to reduce electric field concentration and prevent corona discharge. Consider using potting or conformal coating for additional protection.
• Design for testing and inspection: Ensure easy access to high voltage test points and inspection areas.

Additional tips:

• Use design tools with built-in Design Rule Checking (DRC) capabilities to verify your layout against safety standards.
• Consider consulting with a high voltage PCB design expert for complex or critical applications.
• Always prioritize safety and follow relevant safety regulations and industry standards.

Remember, high voltage circuits can be dangerous, so it's crucial to take all necessary precautions to ensure a safe and reliable design. By following these guidelines and best practices, you can create a high voltage PCB that is both functional and safe.
I hope this information helps! Feel free to ask further questions if you have any specific queries about your design.


Is anyone else using these chat bots to work through this kind of thing, or circuits in general? It seems pretty useful, tho I can’t say I’ve done enough of it to have double checked it’s answers