Designing a high voltage PCB is not just
about scaling up a standard PCB. It requires critical considerations in
preventing arcing, ensuring safety and maintaining long-term performance.
This article will explore how to optimize
high voltage PCB design for safety and reliability, from high voltage clearance
distance, PCB track spacing to insulation, and more.
What is a High Voltage PCB?
The high voltage PCB is a printed circuit
board specially designed to withstand high voltage, which is usually suitable
for applications where the voltage is much higher than that of standard circuit
boards, such as voltages ranging from several hundred volts to several thousand
volts.
Compared with regular PCBs for low voltage
digital or analog signals, high voltage PCBs need to be designed with a focus
on how to prevent electrical breakdown of insulation layers, how to avoid
arcing through air, and how to ensure that there is sufficient clearance
between conductive elements.
Therefore, in the high voltage PCB
design, key considerations such
as the selection of insulation materials, the setting of high voltage clearance
distance, the reasonable arrangement of PCB trace spacing and implementing
structural isolation methods are very important to ensure safety and
reliability.
Common Applications of High Voltage PCBs
High voltage PCBs are commonly
used in equipment that requires high voltage handling and operates in complex
environments, such as:
•
Power supplies and power converters:
These
devices are used to convert voltage levels, such as from AC to DC or from low
voltage to high voltage.
•
Electric vehicle systems:
In
electric vehicles, components like motor drives, battery management systems
(BMS), and charging systems involve the transmission and control of
high-voltage currents.
•
Industrial automation equipment:
Equipment
such as large machinery, robotic arms, inverters, and motor control systems
often deal with high-power and high-voltage signals or loads.
•
Medical devices (such as defibrillators):
Some
medical devices need to deliver a sudden burst of high voltage—defibrillators,
for example, can generate shock voltages in the thousands of volts.
•
Aerospace and defense systems:
These
systems operate in extreme environments, such as high altitudes, low pressure,
and high humidity, requiring circuit boards with outstanding stability and
safety.
In all of the above applications, without
a reliable high voltage PCB design
for arc prevention, it may result in circuit failure, arcing, or even
personal injury. Therefore, the design stage must focus on insulation, spacing,
materials and other factors to ensure the safe, stable and durable operation of
the equipment under high pressure environment.
Key Design Considerations for High Voltage PCBs
If you're designing a circuit board that
needs to work in a high-voltage environment, you can't just draw it like a
regular PCB. When the voltage is high, it's easy to get sparks, current
leakage, or even burn out the circuit. So you need to be extra careful during
the design process. The following areas must be given special attention:
1. Creepage and Clearance Distance
These two terms sound technical, but
they’re actually easy to understand:
• Clearance: This
is the shortest distance “through the air” between two live metal parts. If
they’re too close, high voltage can break down the air and cause a spark (arc).
• Creepage: This
is the shortest path current might “crawl along” the surface of the PCB. If the
surface is dusty, moist, or dirty, it’s even more likely to leak electricity.
So when you design, make sure there’s
enough distance between live parts. If they’re too close, the current might
“jump through the air” or crawl across the board surface.
2. Material Selection
When the voltage gets high, you can't
just use any material.
-
Common
PCB materials like FR4 are okay for regular use, but they may not be safe
enough for high-voltage situations.
-
It’s
better to use materials with stronger insulation, like high-temperature polyimide or ceramic-based materials. These are much harder for voltage to
punch through.
In simple terms: using the right material
keeps the voltage from “breaking through.”
3. Insulation Techniques
Besides keeping parts apart and choosing
good materials, there are extra ways to improve insulation:
• Conformal coating: Spray
a protective layer on the board surface to keep out moisture, dust, and
corrosion.
• Potting or encapsulation:
Fill the whole board or key areas with glue or resin so the current has nowhere
to go.
• Isolation slots: Cut
grooves into the board to physically separate high-voltage areas from the rest,
forcing the current to take a longer, safer path.
These tricks help “lock in” the voltage
so it can’t leak out or jump around.
4. Board Thickness and Spacing
• Board thickness: The
thicker the board, the better it can resist being broken down by high voltage.
• Trace spacing: The
space between copper lines needs to be wide enough. If the traces are too
close, high voltage might jump across them.
A common rule of thumb is: leave at least
2.5 mm of spacing for every 1000 volts. So for 3000 volts, you’d need at least
7.5 mm.
This might make your board bigger, but
it’s worth it for safety.
5. Surface Finish and Via Protection
• For the board surface, use a
high-quality finish like ENIG (Electroless Nickel Immersion Gold). It prevents
oxidation and improves conductivity, which is great for high-voltage boards.
• For the little holes on the board
(called vias), don’t leave them exposed. Cover them or fill them so they don’t
become paths for electrical arcs.
Conclusion
Designing a high-voltage PCB basically
comes down to one simple idea:
Make the current follow the path it’s
supposed to, and don’t let it jump, arc, or leak.
To do that, you need to choose the right
materials, give parts enough space, apply proper insulation, use thicker
boards, and pay attention to the details. If you handle all these key areas
properly, your high-voltage PCB will be able to operate safely and reliably for
a long time.
If you’re doing product design, handling
procurement, or just starting out in the PCB industry, these are the most basic
but essential safety principles you need to understand.
