Rush PCB Inc. produces high voltage PCBs and is an expert in their design and production. We follow international standards for high voltages on PCBs. For this, we isolate sections with high voltage from the rest of the PCB, and mark them with the international hazard symbols.
Our team comprises leading design engineers with decades of experience in handling high voltage PCB design. From design and selection of material to circuit fabrication and final assembly, Rush PCB Inc. engineers are highly experienced in processing a wide variety of materials for printed circuit boards.
General PCBs are not well-suited for high voltage operations, as they can induce arcing. We make high voltage boards of special type of materials with high dielectric strength and capable of withstanding thermal fluctuations. We mainly make them from heavy copper. Most of our high voltage boards are single-sided.
Industries such as those in power generation, military, and the aerospace industry are our main customers for high voltage PCBs. Compared to regular PCBs, the presence of thicker cores and heavy copper in high voltage boards offer characteristics such as:
- Enhanced mechanical strength
- Enhanced capacity for currents
- Enhanced endurance to thermal strains
- Enhanced heat transfer to external heat sinks
- Reduced size (compared to regular PCB for the same current carrying capacity)
However, high voltage PCBs do have their disadvantages also:
Fabricating high voltage PCBs takes substantially longer than for producing regular boards. Moreover, the presence of additional material and heavy copper comes at an additional cost.
Our high voltage boards comply with RoHS and WEEE directives for restrictions on the use of hazardous substances. We have the international certification for ISO 9001, and we also follow the international safety standards ISO 14001, conforming to safe environmental standards.
Materials for High Voltage PCBs
High voltage PCBs must conform to several stringent conditions that promote safety and reliability. This requires using material that continues to maintain its characteristics even as it ages. Some of the material that we use are:
FR4—Although possessing a high dielectric breakdown capacity, FR4 has higher porosity and is susceptible to contamination as compared to epoxy and polyimide. Its weaker edge structure reduces its dielectric value, especially when an FR4 board has developed a crack. Arcing on an FR4 board is likely to carbonize the material.
What is FR-4 Laminate?
BT Epoxy—Compared to FR4, BT Epoxy has better dielectric breakdown around cracks, and the material works best with medium voltage circuits.
Isola Laminates—This material is self-extinguishing, and our customers prefer it as it does not sustain flames. We use Isola laminates for high voltage boards as this material has high insulation properties. We mostly make single sided and very basic double-sided boards carrying high voltages.
Rush PCB Inc. offers full turnkey PCB services that includes high voltage boards as well. We fabricate the high voltage boards according to your design instructions, we procure the components for the board according to your BOM, and we assemble and test your PCBs before shipping them to you. Our customers rely on us for the high standards of quality that we maintain in all our manufacturing activities.
Designing High Voltage PCBs
Apart from the presence of high voltage on the board, the designer must also consider the operating frequency of the signals. Unless there is adequate spacing between circuits carrying high frequencies and others, there is likelihood of cross-talk.
Likewise, inadequate spacing between circuits carrying high voltage and those with lower voltages can result in arcing. Spacing for high voltages involves two distances, clearance and creepage. While creepage is the separation following the insulated PCB surface, clearance distance is the separation in air. Electrochemical migration from copper, tin, and silver can create conductive filaments across the PCB surface, leading to a reduction is the actual separation. Maintaining a large creepage distance helps in maintaining a proper separation.
Multi-Layered High Voltage PCBs
Although difficult to manufacture, Rush PCB Inc. does fabricate multi-layered high voltage PCBs, but these require following a few set guidelines. For PCB tracks and vias with a difference of voltage not greater than 80 V:
- Spacing should be at least 0.1mm, if they are on an internal layer.
- Spacing should be at least 0.6 mm, if they are on an external layer and not covered with solder resist.
- Spacing should be at least 0.13 mm, if they are on an external layer and covered with solder resist.
Heavy Copper in High Voltage PCBs
At Rush PCB Inc., we normally use heavy copper weighing 4-20 oz. However, depending on customer specifications and application requirement, we can use heavy/extreme copper weighing anywhere between 20-200 oz as well.
We use high speed plating and differential etching for working with heavy copper. This method allows us to control the thickness of the copper plating, and helps with realizing vias with better plating on their barrel.
Heavy copper can carry higher currents without heating up substantially. The level of current that a track can safely carry depends upon the heat the current flow generates. Direct convection from the track surface and conduction through the board material helps in cooling the trace and stabilizing its temperature.
DFM/DFA for High Voltage PCBs
We conduct a DFM or design for manufacturing and DFA or design for assembly check when we receive a design from our customers. For high voltage PCBs, we check the following major points:
- High voltage circuitry is in an isolated area, as grouping circuits carrying high voltages helps minimize chances of damage on the board.
- Adequate creepage and clearance is available, depending on voltage levels.
- Adequate spacing is available for high frequency tracks
- Components have adequate derating
- The tracks and copper lands do not have any sharp corners to cause arcing
- The board material can withstand high voltage without breakdown
Industries that use high voltage PCBs also have environments with fluctuating thermal conditions. At Rush PCB Inc., we design high voltage PCBs capable of handling extreme thermal excursions. This calls for stringent quality control so that we can achieve the best quality and reliability our customers have come to rely upon for high voltage PCBs.