In the realm of high voltage PCB designs, meticulous precision and thoughtful selection of the appropriate PCB material are imperative. Additionally, it is crucial to understand the motivations behind the desire for a high voltage board, carefully choose components, implement quality testing procedures, and account for key design considerations.
This article aims to provide comprehensive insights into the realm of high voltage PCB designs and boards. It commences with a fundamental definition and subsequently delves into the associated design procedures. Without further ado, let us embark on this informative journey.
What are High Voltage PCBs?
A printed circuit board (PCB) operating at a voltage higher than the typical range is commonly referred to as a high voltage PCB. This classification encompasses various applications such as inverters, EV boards, and power suppliers. It is important to note that there is no universally defined threshold that determines when a PCB qualifies as high voltage. However, some individuals consider a PCB to be high voltage if it operates at a minimum of 100V, although this is not an official designation.
When dealing with voltages above this threshold, certain design practices must be carefully considered to ensure the reliability and functionality of the printed circuit board. Prior to commencing the design process, it is essential for the designer to possess a comprehensive understanding of key terms and concepts associated with high voltage PCBs. These include but are not limited to basic insulation, functional insulation, altitude, creepage distance, reinforced insulation, double insulation, supplementary insulation, conductive elements, and clearance.
Furthermore, the selection of an appropriate insulating material for high voltage designs is a critical aspect that demands careful attention.
Types of High Voltage Printed Circuit Board
High voltage printed circuit boards (PCBs) are designed to withstand and distribute high voltage levels safely. They are commonly used in various applications such as power electronics, industrial equipment, electric vehicles, and high-voltage power supplies. Here are some types of high voltage PCBs:
Single-sided PCBs
Single-sided high voltage PCBs have conductive traces on one side of the board, with all components mounted on the same side. They are relatively simple and cost-effective, suitable for lower voltage applications.
Double-sided PCBs
Double-sided high voltage PCBs have conductive traces on both sides of the board, with vias connecting the top and bottom layers. This design allows for more complex circuitry and higher voltage handling capabilities.
Multilayer PCBs
Multilayer high voltage PCBs consist of several layers of conductive traces separated by insulating layers. They offer increased routing density and better signal integrity, making them suitable for high voltage and high-frequency applications. The number of layers can vary depending on the specific requirements.
Hybrid PCBs
Hybrid high voltage PCBs combine multiple technologies, such as FR-4 (standard PCB material) and ceramic substrates, to achieve higher voltage ratings. These boards are designed to handle extreme voltage levels and offer enhanced thermal performance.
Metal core PCBs
Metal core high voltage PCBs have a metal core layer (usually aluminum or copper) that acts as a heat sink, providing excellent thermal conductivity. They are suitable for high-power applications where heat dissipation is crucial.
Flexible PCBs
Flexible high voltage PCBs are made of flexible materials like polyimide or polyester. They can be bent or twisted to fit into space-constrained applications while maintaining high voltage handling capabilities.
Ceramic PCBs
Ceramic high voltage PCBs utilize ceramic materials as the base substrate due to their excellent electrical insulation properties. They can handle high temperatures, have low thermal expansion, and are often used in high power and high-frequency applications.
It’s important to note that the specific design and construction requirements of high voltage PCBs can vary depending on the voltage levels, current ratings, environmental conditions, and safety regulations of the intended application. Working with experienced PCB designers and manufacturers is crucial to ensure the correct choice of materials and manufacturing processes for high voltage PCBs.
PCB Materials for High Voltage
When designing a high voltage PCB, it is crucial to select materials that can maintain peak performance in both regular environments and during overvoltage events as it ages. The choice of materials for the main components of the PCB should be carefully considered.
First and foremost, the board material itself plays a vital role as it provides the foundation for the PCB’s functionality. It is essential to evaluate various factors in your design before finalizing the material selection. One commonly used material is FR4 laminate, which offers a high dielectric breakdown. However, it is important to note that FR4 laminate has a weak edge structure and is susceptible to contamination. Another option is BT epoxy, which provides good resistance overall, but its suitability is limited to specific applications due to its strong sidewalls. High voltage laminates offer exceptional performance but come with higher costs.
Copper, used for creating PCB vias, should have a sufficiently heavy weight to withstand high currents and mechanical stress. It is recommended to incorporate heavy (4-10 oz) or extreme (10-50 oz) copper circuits and materials in the PCB design.
Although not considered major PCB components, the resin and glass levels in the board significantly influence its durability in high-voltage situations. Optimal dielectric properties can be achieved by using a board with high resin content and a small glass style.
To ensure that a material can provide adequate insulation to withstand high-voltage DC bias, it is essential to research its Comparative Tracking Index (CTI). CTI indicates the voltage at which a material starts to break down in a standardized test. Manufacturers of PCB laminates typically provide CTI figures for their products on datasheets. CTI numbers are categorized from 0 (>600 V) to 5 (<100 V), with Category 5 representing the lowest level of insulation. It is worth noting that industry standards such as IEC-60950-1 and IPC-2221 also recommend specific materials for high voltage PCBs.
Furthermore, it is important to consider other environmental factors besides high-voltage environments. A PCB designed for high insulation standards may also need to withstand high-vacuum or high-pressure applications.
By carefully considering these factors and selecting appropriate materials, you can ensure that your high voltage PCB will maintain optimal performance in various environments while aging gracefully.
Component Sourcing for High Voltage PCB
When procuring high voltage PCB components, it is crucial to begin by developing a comprehensive bill of materials (BOM). The BOM serves as an overview of all the necessary components required for the assembly of your board. It should include details such as the quantity of parts needed, their sizes, and the respective sources for procurement. By creating a well-defined BOM, you gain a clear understanding of the entire assembly process.
In many cases, you will need to outsource certain components from other manufacturers. To ensure accurate guidance in acquiring the necessary components, a well-prepared BOM becomes an essential requirement. It enables manufacturers to identify and fulfill your specific requirements for high voltage PCBs.
It is crucial to source your components from reliable, experienced, and certified companies. Such companies have proven their competence and expertise in the field. By engaging with reputable suppliers, you can be confident in the quality and suitability of the sourced components. Additionally, the BOM serves as a valuable tool for generating accurate quotations, aiding in the budgeting and cost estimation process.
When sourcing PCB components from overseas, it is imperative that the manufacturer possesses shipping capabilities. Given the fragile nature of components, special packaging and shipping methods are necessary to ensure their safe arrival. Therefore, it is essential to verify that the manufacturer can handle the packaging and shipping requirements adequately. By considering these factors, you can be assured that the outsourced components will meet your specific needs.
It is important to note that the selection of PCB components depends on the particular applications of the printed circuit board. Each application may have unique requirements, necessitating the sourcing of specific components tailored to those needs. Consequently, it is crucial to identify and procure components that align with the intended purpose and specifications of the high voltage PCB.
While cost considerations are important, it is unwise to prioritize cheap components over quality when it comes to high voltage PCBs. The paramount factor to consider is the quality of the components. Substandard components can lead to performance issues, safety hazards, and reliability problems. Therefore, it is advisable to prioritize quality over cost to ensure the optimal functioning and longevity of the high voltage PCB.
High Voltage PCB Design Tips
When designing a high voltage PCB, there are several important tips to keep in mind to ensure safety, reliability, and optimal performance. Here are some key considerations:
Material Selection: Choose PCB materials that are specifically designed for high voltage applications. Consider factors such as dielectric breakdown strength, insulation resistance, and tracking resistance (CTI). High voltage laminates or specialized materials like FR4 with high CTI ratings are commonly used.
Creepage and Clearance: Maintain appropriate creepage and clearance distances between high voltage traces and components to prevent arcing and electrical breakdown. Follow industry standards and guidelines for minimum clearance requirements based on the voltage levels involved.
How to Determine Spacing and Materials When Designing High Voltage PCBs?
● IPC-2221 is a widely recognized standard that offers comprehensive guidelines for PCB design, including clearance and creepage distance. It provides specifications and recommendations to determine the appropriate spacing between conductors, taking into account factors such as voltage levels and environmental conditions. Adhering to IPC-2221 ensures that the PCB layout maintains adequate insulation and minimizes the risk of electrical breakdown or arcing.
● IEC-60950-1 is a specific standard applicable to IT products powered by AC mains or batteries. It focuses on electrical safety requirements for information technology equipment and covers aspects such as protection against electric shock, insulation coordination, and clearances. Compliance with IEC-60950-1 ensures that high-voltage PCBs used in IT products meet internationally recognized safety standards.
● By incorporating guidelines from IPC-2221 and adhering to the requirements of IEC-60950-1, designers can ensure that their high-voltage PCBs are designed with appropriate clearance and creepage distances, insulation coordination, and other critical safety considerations. These standards provide a framework to minimize risks and ensure the safe operation of high-voltage PCBs in various applications.
Copper Weight: Use heavy copper traces and planes to handle high currents and minimize resistive losses. Consider using heavier copper weights (e.g., 4 oz or more) for high voltage sections of the PCB.
Insulation and Encapsulation: Apply conformal coating or potting materials to insulate and protect the PCB from moisture, contaminants, and potential corona discharge. Use materials with high dielectric strength and resistance to breakdown.
Component Selection: Choose components rated for high voltage operation to ensure they can withstand the required voltage levels without breakdown or damage. Pay attention to voltage ratings of capacitors, resistors, connectors, and other active and passive components.
Layout Considerations: Carefully plan the PCB layout to minimize high voltage traces’ proximity to low voltage or sensitive circuits. Keep high voltage traces away from signal traces and sensitive components to avoid coupling and interference.
Grounding and Shielding: Implement proper grounding techniques to minimize ground potential differences and reduce the risk of electrical breakdown. Consider using shielding techniques to protect sensitive circuits from high voltage interference.
Test and Verification: Perform thorough testing and verification of the PCB design, including high voltage testing under controlled conditions, to ensure it meets the required specifications and safety standards.
Safety Precautions: Take appropriate safety precautions when working with high voltage PCBs. Always follow safety guidelines and procedures to prevent electrical hazards during assembly, testing, and maintenance.
Compliance with Standards: Adhere to relevant industry standards and regulations for high voltage PCB design, such as IEC-60950-1 and IPC-2221, to ensure compliance and safety.
Remember, the design of high voltage PCBs requires careful consideration of various factors to ensure safe and reliable operation. Consulting with experienced professionals or engineers specializing in high voltage design is highly recommended to ensure the best practices are followed and potential risks are mitigated.
EMI Factors to Consider
High-voltage printed circuit boards (PCBs) are renowned for their ability to generate a wide range of frequencies. To effectively reduce these frequencies, it is crucial to minimize the loop area and maximize the grounding of the PCB, while also considering the use of a metallic sheet for insulation of high-voltage components.
Transformers with High Frequencies
In the case of transformers used in switch-mode circuits to generate high voltages on high-voltage boards, it is important to adhere to the insulation level of the transformer’s core. Ideally, the PCB layout should include a split ground plane between the main and secondary sides. Additionally, a significant isolation gap with cutouts should be incorporated on the board, creating separation between the primary and secondary sides.
Mosfets/Transistors/Switches
When it comes to high-voltage devices such as MOSFETs, transistors, and switches, it is generally advisable to select devices that are specifically designed to tolerate high voltages, as they are typically available in appropriate packaging. Opting for devices with larger pin pitches is recommended when high voltages are expected. For instance, choosing a TO-247 device over a TO-220 device, if space permits, would be a suitable choice. Similar considerations can be applied to surface-mount devices (SMDs) as well.
Mosfets/Transistors/Switches
The selection of passive components is crucial in high-voltage designs, as the voltage tolerance directly depends on the size of the component. For example, if there is a 300V potential difference across an SMD resistor, it is preferable to choose a larger package size such as 1206 rather than 0402. In some cases, it may be necessary to place multiple components in series to distribute the voltage stress evenly across them.
Cutouts and Slots for Isolation
To ensure safety compliance, it is important to incorporate cutouts or isolation holes near any high-voltage component on a high-voltage board. These features are required by various safety regulations applicable to consumer goods such as chargers and power supplies. Particularly in high-humidity environments or situations where contamination is a concern, these cutouts and slots contribute to improved reliability. Most often, these isolation slots and cutouts are located in the mechanical layer of the board.
By following these practices in a professional manner, high-voltage PCB designs can effectively manage frequencies, ensure component tolerances, and meet safety requirements, ultimately resulting in reliable and efficient high-voltage systems.
Why Should You Design PCBs for Systems of High Voltage?
One primary reason for the widespread use of printed circuit boards (PCBs) capable of handling high voltages is their necessity in various industries. Sectors such as high voltage applications, power generation, military, and aerospace heavily rely on these specialized boards. Utilizing alternative PCBs in these industries can lead to increased arcing, which not only incurs substantial costs but also causes significant inconvenience.
Benefits of a High Voltage PCB Design
There are numerous benefits associated with high voltage PCB designs, primarily attributed to the utilization of heavier copper compared to other PCB designs. These advantages include enhanced endurance against thermal strains, ensuring that the board can effectively withstand thermal fluctuations.
Moreover, high voltage PCBs exhibit increased current-carrying capacity, a characteristic not commonly found in other types of boards. Additionally, these boards offer superior mechanical strength, particularly evident in plated-through holes (PTH) and connector sites. By incorporating a higher copper weight on the circuitry layer, high voltage PCBs enable a significant reduction in the overall product size. Furthermore, copper-plated vias facilitate efficient heat transfer to external heatsinks, optimizing thermal management.
Drawbacks of a High Voltage PCB Design
However, it is important to acknowledge that high voltage PCB designs do have certain drawbacks. The foremost drawback is their higher cost. The incorporation of heavier copper necessitates additional materials, leading to increased expenses in the manufacturing process. Furthermore, fabricating and assembling high voltage PCBs requires more time compared to standard PCBs. The additional modifications involved, such as the use of heavier copper, contribute to the extended production duration.
Therefore, the prevalence of high voltage PCBs across various industries is driven by their ability to handle high voltages effectively. These specialized boards offer several benefits, including improved endurance against thermal strains, increased current-carrying capacity, and enhanced mechanical strength. However, it is important to consider the associated drawbacks, such as the higher cost and longer fabrication time. Despite these limitations, high voltage PCBs remain indispensable in industries where reliable performance under high voltage conditions is crucial.
Applications of the High Voltage PCB
High voltage PCBs find applications in numerous industries and technologies where the ability to handle high voltages is essential. Here are some common applications of high voltage PCBs:
Power Generation: High voltage PCBs are extensively used in power generation plants, including thermal power plants, hydroelectric power plants, and nuclear power plants. They are employed in various components such as transformers, switchgear, power converters, and control systems, where they ensure reliable operation and efficient power transmission.
High Voltage Equipment: Industries that require high voltage equipment, such as electric utilities, industrial automation, and energy distribution, rely on high voltage PCBs. These PCBs are used in circuit breakers, voltage regulators, power supplies, and high voltage switches to ensure safe and efficient operations.
Aerospace and Defense: The aerospace and defense sectors extensively utilize high voltage PCBs due to their stringent requirements for reliable performance under extreme conditions. These PCBs are used in aircraft electrical systems, avionics, radar systems, missile guidance systems, and electronic warfare equipment.
Medical Equipment: High voltage PCBs play a vital role in medical equipment that requires high voltage applications, such as X-ray machines, CT scanners, MRI systems, and particle accelerators. These PCBs enable precise control of electrical signals and ensure the accuracy and safety of medical procedures.
Research and Scientific Instruments: High voltage PCBs are used in various research and scientific instruments, including particle accelerators, laser systems, high voltage power supplies, and analytical instruments. They provide the necessary voltage stability, precision, and insulation required for accurate measurements and experimental setups.
Alternative Energy Systems: Renewable energy systems such as solar power and wind power often require high voltage PCBs. These PCBs are used in inverters, converters, and energy storage systems to convert and manage high voltage DC or AC power efficiently.
Electric Vehicles: As the demand for electric vehicles (EVs) continues to grow, high voltage PCBs are crucial for their power electronics systems. They are employed in EV battery management systems, motor controllers, charging stations, and onboard charging systems, ensuring efficient and reliable power conversion and distribution.
High Voltage Testing and Measurement: High voltage PCBs are utilized in testing and measurement equipment for high voltage applications. They are employed in devices such as high voltage probes, voltage dividers, high voltage measurement systems, and high voltage test equipment, enabling accurate and safe voltage monitoring and testing.
These are just a few examples of the diverse applications of high voltage PCBs. Their ability to handle high voltages reliably and efficiently makes them indispensable in industries and technologies where electrical power and voltage control are critical.
High Voltage Testing and Verification
High voltage testing and verification are crucial steps in ensuring the safety, reliability, and compliance of high voltage PCBs. Here are some common techniques and considerations for high voltage testing and verification:
Insulation Resistance Testing:
Purpose: To measure the insulation resistance between high voltage traces and other conductive elements.
Method: Apply a DC voltage between the high voltage node and ground and measure the resulting current flow. A high insulation resistance indicates good isolation, while a low resistance may indicate potential insulation breakdown.
Equipment: Insulation resistance testers or megohmmeters.
Dielectric Withstanding Voltage Testing:
Purpose: To assess the ability of the PCB to withstand high voltage without breakdown or excessive leakage current.
Method: Apply a high AC or DC voltage between high voltage traces or nodes and ground for a specified duration while monitoring leakage current and observing for any breakdown or arcing.
Equipment: High voltage testers or hipot testers.
Partial Discharge Testing:
Purpose: To detect and measure partial discharges, which are localized electrical discharges within the insulation material.
Method: Apply a high voltage and monitor for any discharge pulses using specialized sensors or detectors. Partial discharge activity can indicate potential insulation weaknesses.
Equipment: Partial discharge detectors or monitoring systems.
High Voltage Impulse Testing:
Purpose: To assess the ability of the PCB to withstand fast voltage transients or impulses, such as lightning strikes or switching surges.
Method: Apply high voltage impulses or surges to the PCB and observe for any breakdown or flashover. The PCB should be able to withstand the specified voltage level without damage.
Equipment: High voltage impulse generators.
Thermal Testing:
Purpose: To evaluate the thermal performance and heat dissipation capabilities of the high voltage PCB.
Method: Apply high voltage and monitor the temperature rise of critical components and the PCB itself. Thermal imaging or thermocouples can be used to measure temperature distribution.
Equipment: Thermal imaging cameras, thermocouples, or thermal chambers.
Functional Testing:
Purpose: To verify the overall functionality and performance of the high voltage circuitry.
Method: Apply appropriate input signals and measure the output responses of the circuit. Verify that the high voltage circuit operates as intended and meets the specified requirements.
Equipment: Signal generators, oscilloscopes, multimeters, or specialized test equipment.
It’s important to refer to relevant safety standards, guidelines, and specifications when performing high voltage testing. Additionally, ensure that the testing equipment is calibrated and operated by trained personnel to maintain safety and accuracy.
Conclusion
Jarnistech is a trusted and dependable contract manufacturer specializing in high-voltage PCBs. With our extensive years of experience and a team of highly skilled professionals, we are fully committed to providing you with superior service.
We possess in-depth knowledge on optimizing the design of high-voltage circuits, ensuring they remain free from contaminants while meeting your specific requirements. Our expertise allows us to achieve optimal performance without compromising on quality.
Count on us to leverage a wide range of materials to construct various layers of high-voltage PCBs, including single-sided and double-sided boards. By utilizing these materials effectively, we can deliver exceptional results that align with your project objectives.
Investing in a higher voltage circuit board offers numerous advantages. Notably, it enables significant reductions in product size, enhances thermal endurance, facilitates efficient heat transfer to external heatsinks, and increases the current-carrying capacity. These benefits contribute to the overall performance and reliability of your products.
Partner with JarnisTech for your high-voltage PCB manufacturing needs, and experience the difference our professionalism and expertise can make.