When creating a PCB for high voltage DC bias, standards and precautions become much more stringent. High voltage PCB materials and design for arc prevention ensure the final product is safe and functional. Avoid increased costs and danger by keeping these PCB materials and design tips in mind.
PCB Materials for High Voltage
Materials used in high voltage PCB design need to stay at peak performance in both regular environments and overvoltage events as it ages. Consider the following materials for the main components of your PCB:
- Board material: When choosing materials for your PCB, you should prioritize the board itself. It provides a foundation for the rest of the PCB’s functionality, so weigh all the factors in your design before ordering the material. FR4 laminate offers a very high dielectric breakdown, but it also has a weak edge structure and vulnerability to contamination. BT epoxy provides good resistance all around, but it only suits select applications due to its strong sidewalls. High voltage laminates have very high performance but also high prices.
- Copper: The copper used to create your PCB’s vias should have a heavy enough weight to withstand high currents and mechanical stress. The PCB should include heavy (4-10 oz) or extreme (10-50 oz) copper circuits and materials.
- Resin and glass: While not technically a major PCB component, the resin and glass levels in your board will influence its durability in high-voltage situations. A board with high resin content and a small glass style offer the best dielectric properties.
To determine whether a material will provide enough insulation to survive a high-voltage DC bias, research its Comparative Tracking Index (CTI). A material’s CTI indicates the voltage at which it begins to break down in a standardized test. Companies that manufacture PCB laminates do share the CTI figures for their products on the datasheets. CTI numbers come in six categories from 0 (>600 V) to 5 (<100 V), with Category 5 expressing the lowest level of insulation. Industry standards such as IEC-60950-1 and IPC-2221 also mention recommended materials for high voltage PCBs.
Remember that in addition to using a material suitable for high-voltage environments, you must find an option that can stand up to other environmental factors. A PCB with high standards for insulation could also require materials that succeed in high-vacuum or high-pressure applications.
High Voltage PCB Design Tips
Once you choose your PCB’s materials, your manufacturer should follow design principles that increase its suitability for high voltage DC bias, such as:
- Creating a smooth surface finish to minimize the chance of arcs
- Following safety standards for spacing
- Reducing burrs on board edges after routing
- Avoiding sharp corners in the traces and pads’ layout
Clearance vs. Creepage in PCBs
PCBs have tight spacing requirements measured in creepage and clearance. In high voltage environments, an arc can easily form between two of the PCB’s conductive elements. Correctly spacing components reduces the risk of an arc occurring. Clearance and creepage determine this spacing. Clearance refers to the distance through the air between two conductors. If two conductive elements don’t have sufficient clearance, an over-voltage event can cause an arc between them. Creepage also represents the distance between two conductors, but on the surface of the material instead of through the air. Proper creepage ensures the board’s components don’t become too crowded.
High Voltage Applications
More industries than you may think require PCBs that withstand high voltage. Conditions such as low air pressure cause voltages to arc at an increased rate, so some applications that don’t immediately use a high current still need a PCB with good design. Customers need these PCBs for applications involving:
- Spacecraft and other space equipment
- High-altitude aircraft
- High-tech lasers
- Power supplies for particle colliders
PCBs that function in high-voltage applications power the most innovative technologies available today. Engineers, scientists and researchers use this technology to advance our understanding of the way the world works and to develop even more advanced technology. When you create a product featuring a high voltage PCB, you contribute to cutting-edge STEM fields.
More Information About PCBs
To learn more about the materials used to create PCBs, contact us online. Our team members understand the processes behind PCB production and supply and can direct you to the product or service you need for your project. We also supply PCBs in a wide range of materials for numerous applications. Call 717-558-5975 to speak with our customer support team about any PCB-related topic.