Any PCB that works at a very high voltage is called a high-voltage PCB. Devices like main-powered power supplies, inverters, and EV chargers have high-voltage PCBs. They take an input power of 220V from the wall outlet. This voltage level is very high as compared to standard PCBs.
What is a high-voltage PCB?
Any printed circuit board that works at a higher voltage rate is known as a high-voltage printed circuit board. The high-voltage PCBs are manufactured at a higher level of an industry standard that can endure a high voltage of up to 220V. It is usually used in devices like laptops, chargers of heavy trucks, high-power electronics, and inverters. To avoid potential breakdowns or failures, a manufacturer ensures several key terms including, creepage distance, reinforced insulation, double insulation, supplementary insulation, conductive elements, basic insulation, functional insulation, altitude, and clearance.
The Working Range for high-voltage PCBs
The working range for high-voltage PCBs is uncertain. There is no standardized or official rating for high-voltage PCB designs. The designers frequently make a high-voltage PCB that is capable of working at 150V to 200V. As a result, any circuit working at levels above 150 volts is known as a high-voltage PCB.
Important Materials Used for Making High Voltage PCB
A strict manufacturing criterion is followed during the development of high-voltage PCBs. This criterion is important in preventing the formation of electrical arcs. The selection of the best products ensures the reliability and safety of the product, allowing it to maintain its maximum functionality over time. Some of the suggested high-voltage materials are explained below:
The FR4 laminate provides resistance against elevated dielectric breakdown. Nonetheless, when compared to materials like polyimide and epoxy, it has greater porosity, rendering it vulnerable to contamination. Its edge structure is relatively fragile. The presence of a crack at the edge results in a reduction of its dielectric properties. It is used to prevent carbonization that results from high voltage or overvoltage incidents.
BT epoxy helps in making perfect side structures. It is beneficial for applications that have planar coils. It is the best choice for medium-high voltage circuits. It is very suitable for making heavy-duty printed circuit boards.
These are the top choices due to their capabilities of ending arcs created on the circuit boards due to overloading and overheating. The Isola laminates come at a higher cost. Typically, Isola laminates are used in double-sided and single-sided boards. It is important to consider environmental factors when using these high-voltage PCB materials.
This process is an exhausting adventure. It is necessary to follow the professional manufacturing steps for the best results.
The following methods are preferred for making high-voltage PCBs:
Internal Layers making process
It is a flexible process to add multiple layers in the PCB’s layers by using low voltage across all the layers.
Consider the following factors while making the internal layering of a high-voltage PCB:
- Material Selection: Avoid using the usually used prepreg named, Flame Retardant 4 (FR-4) for this design. It is not suitable for low-to-high voltage PCB designs due to its delicate internal structure.
- Spacing Considerations: Manufacturers ensure that the minimum thickness of individual layers is 0.005 inches. This thickness size allows the required spacing and filling in the layers of a PCB.
To attain the required results, it is important to route and connect the traces correctly. The following suggestions can help in the best routing of the PCB:
- Avoid connecting the high-voltage traces through the internal layers of the board.
- Add “clearance” in the traces, especially when these traces show a substantial voltage difference.
- Prevent pointed corners in the high-voltage PCB design. This minimizes their possibility of being utilized as the areas have strongly developed electric fields.
Notice the Disturbances
PCBs are easily perturbed by Electromagnetic Interference (EMIs) in the form of disturbances. The emergence of such particles on the PCB becomes a major problem in the performance of high-voltage circuits. EMI radiation can occur internally and externally in the PCB.
The following are the effective strategies that can prevent electromagnetic interference within the PCB:
- Protecting the high-voltage components by placing them in a metallic cover.
- Attaching the vias to the ground plane.
- Minimizing the loop placed on the printed circuit board.
Plane clearing process
In this process, the polygon concentrated site is created to cover various sections of the board within itself. It is an area that promotes high voltage. Avoid the addition of compact spacing between the internal layers of a PCB. It leads to highly functional PCBS.
Important things to consider during the manufacturing of high-voltage PCB
Exceptional design principles and factors are followed to make the best quality high-voltage PCB. The design concepts and professional practices serve as guidelines for achieving the best results. These principles lead to the further manufacturing of an exceptional quality high voltage printed circuit board. Here are some key aspects to keep in mind while crafting a high-voltage circuit board:
Unlike clearance, creepage is an alternative approach for the separation between a PCB’s conductive components. The methods of creepage and clearance are different techniques that quantify the spacing between conductors or conductive elements on the PCB. Creepage measurement occurs along the surface of a solid insulating material. The following options are considered to enhance the creepage distance on a high-voltage PCB:
- Enter a vertical insulating barrier or introduce a slot between the tracks. This technique effectively increases the creepage distance on the board.
- Prevent the entrance and gathering of dust or moisture because these factors can reduce the creepage distance.
Isolating the high-voltage areas
It is necessary to consider that the PCB components work at different voltage levels. Isolation is vital for protecting the low-voltage components from the components that use high voltage. It is important to prevent the high-voltage PCBs from getting affected through arcing due to isolation. The most effective approach is to create isolation for the high-voltage regions. Here are key guidelines to help you establish this process:
- Grouping of Circuitry: Begin by grouping the circuitry. This method ensures that circuits with the same voltage levels are present in a designated area. It will reduce the negative impact that can arise if there is an interaction with other components.
- Incorporating Inserts: The best method is using inserts that separate the regions having high voltage from the other parts of the printed circuit board. The routing slot must be placed near the insert for enhanced separation.
Consider the Clearance
The most important factor for consideration during the manufacturing is the clearance. Two critical aspects of high-voltage PCB design are clearance and creepage, and their functionality provides beneficial results for the maximum functionality of the board. Clearance means the “minimum air gap between the two conductors.” This measurement is preferred to prevent the increased risk of arcing when there is insufficient clearance between the two conductors during an over-voltage incident.
Noise Sources’ Isolation
Isolation is not only related to high-voltage regions but it is also helpful in controlling the noise-generating sources. This can be achieved through the following steps:
- Demarcating the high-voltage areas from the other regions on the PCB where the noise comes from.
- Employing the shorter routing traces on the high-voltage PCB.
Solder Mask Application
Another important method for consideration during the high-voltage PCB design is the placement of the solder mask on the surface of the PCB. It serves as one of the board’s insulators. Effective techniques for applying the solder mask are given below:
- The solder mask should be applied between the fine pitch of the circuit board.
- Prefer to apply the solder mask in the middle of the high-voltage PCB between the pins and the exceptionally fine pin pitch.
Leverage the “Isolation Slots”
Special isolation slots are placed on the printed circuit board. Depending on the requirements of a specific device the features are designed for isolation. This is particularly observed in power supplies and electric vehicle charging systems that mostly have prominent isolation slots and cut-outs. These openings allow the easy isolation of high-voltage components located near a particular section of the board.
The Working Frequency of a High Voltage PCB
The working Frequency is the level of power that the high-voltage Printed Circuit Board uses for its functioning. The frequency is ensured to be finely tuned by the prevailing factors in the surroundings. For example, some environments encounter issues like electrochemical migration and etching. To end the risk of arcing at lower voltages with higher frequencies, the following recommendations are considered by the manufacturers:
Check the Dielectric Strength
A PCB component can have a weak dielectric strength if it fails to perform as expected, particularly after exposure to the maximum electric field. It confirms if the PCB is suitable for functioning for high voltage appliances. Dielectric strength means the maximum electric field a PCB material can tolerate without losing its insulating properties. The selection of high-power components assures the superior dielectric strength of a high-power PCB.
What are the Applications of the High Voltage PCB?
They are specially designed for handling and distributing high-voltage electrical signals. These boards are used in a wide range of applications where high voltage is usually required. Some of the common applications of high-voltage PCBs are given below:
They are used in the construction of power supply units for various electronic devices, such as laboratory power supplies, medical equipment, and industrial machinery.
Electric Vehicles (EVs):
They are necessary components of electric vehicles. It is included in hybrid and fully electric cars. They are used to manage and distribute high-voltage power to the vehicle’s electric drivetrain.
Solar inverters convert direct current (DC) electricity generated by solar panels into alternating current (AC) for usage in homes and businesses. They are utilized in these inverters to handle the conversion process efficiently.
Many medical devices, such as X-ray machines and MRI scanners, need high-voltage components and PCBs for their operation. These PCBs ensure the safe delivery of electrical signals in electronics.
These PCBs are used in industrial equipment. These equipment include high-power laser systems, plasma cutting machines, and manufacturing equipment. They require high voltage for operation.
In the telecommunications industry, high-voltage PCBs are used in equipment like power amplifiers, transmitters, and base station components. In these devices, high-voltage signals need to be processed and transmitted.
Instruments used in scientific research usually need high-voltage PCBs. This equipment includes electron microscopes, mass spectrometers, and particle accelerators, where precise control of high voltage is necessary.
Aerospace and Defense:
These high-voltage PCBs are used in aerospace and defense applications. This equipment includes radar systems, avionics, satellite communication equipment, and missile guidance systems.
Electric Grid and Utilities:
They are used in power distribution equipment and substations for managing high-voltage electrical transmission and distribution.
They are used in specialized lighting applications, such as high-intensity discharge (HID) lamps. In such equipment, high voltage is required for illumination.
Particle accelerators are used in physics research and medical applications. They rely on high-voltage PCBs for generating and controlling high-energy particle beams.
Research and Development:
They are used in experimental setups for research and development purposes. In this equipment, high-voltage circuits are required for the best functioning process.
High-voltage PCBs play a crucial role in the production of devices that operate in varying temperature conditions. They are specially prepared to tolerate these temperature fluctuations. From the board’s production to the assembly phase, these PCBs ensure optimal performance. The board design and all the production phases of such PCB require great consciousness and adherence to the established guidelines and best practices.
Can PCB handle high voltage?
Yes, some PCBs are specifically made to tolerate high voltages through the use of special components on the circuit board.
What is the spacing for PCB for high voltage?
Following the “3W” guideline, the gap between two microstrips and the neighboring high voltage line should be 1.5 mm. It is approximately equivalent to 60 mils.
What is considered as high voltage in PCB design?
Some heavy appliances like inverters, electric vehicle boards, and power supplies are considered as high voltage in PCB design. Some manufacturers classify high-voltage PCBs as those with a minimum of 200 volts.
What are the failure mechanisms in high-voltage printed circuit boards?
Two primary categories of failure mechanisms are used to handle situations related to metal migration and electrical breakdown. Failures of high-voltage PCBs are due to elevated voltage and closer conductor spacing.
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