Preventing Short Circuits in Polyimide Heaters: Detection and Protection Techniques

As we all know, flexible polyimide heaters are designed to be durable and withstand the most extreme conditions in all kinds of applications. However, it’s a good idea to give them a little help to prevent breakdowns and ensure optimal performance. To do this, we must follow safety protocols and remain attentive to the slightest change or alteration to our equipment.

Whether it’s in the aerospace industry, laboratories, or military units, learn how to prevent short circuits with these tips!

With the development of science and technology and the needs of human life, the gradual emergence of electric heating film materials has occurred. The electric heating film is mainly composed of conductive substances and film-forming substances or film materials.

Detecting Short Circuits in Polyimide Heaters

Visual Check

The easiest way to start is to take a close look at your polyimide heaters. Look for delaminations or perforations, burn marks, or discoloration on the surface. Also, watch for damaged or exposed wiring that could cause electrical contact.

Voltage and Resistance Checks

For more detailed testing, a multimeter can be used to detect any resistance fluctuations that could indicate a short circuit.

Set the multimeter to continuity mode and place a probe on each terminal of the polyimide heater.

• Is the multimeter beeping continuously? Then there’s definitely a short circuit somewhere.
• Is the resistance lower than expected? This could be a sign of an internal malfunction.

Thermal Imaging Analysis

Thermal imaging analysis is a precise and non-invasive technique that allows for early detection of any potential short circuit thanks to real-time results.
Using infrared cameras, it monitors the heat distribution over a given surface. This allows for the detection of hot spots, broken connections, and wiring problems leading to irregularities in the current flow.

Insulation Leakage Check

In a properly insulated polyimide heating element, leakage current should be negligible. However, physical damage, manufacturing defects, overheating or exposure to certain chemicals are not without consequences.

In a current leakage test, the heating element is disconnected from its power source and circuit. A megohmmeter is used to apply a high voltage between the conductor and the outer surface of the heating element. A high resistance (greater than 100 MΩ) indicates good insulation. However, caution should be exercised if the resistance appears below 10 MΩ, as this may indicate degraded insulation.

Short Circuits in Polyimide Heaters : practical cases

The heater remains cold

Why ?

• No power or abnormal power supply.
• The power cord is loosely connected to the electric heater’s outlet, or the cord is broken.
• The resistance wire or heater is burned out.

What to do ?

It’s best to replace a damaged heating element, as repairs are usually tricky. Check the circuit using a normal power supply first, replace any faulty elements, and resolder the wires.

I notice the leakage of heating element

Why ?

• The heating element insulation is damaged, or the element has burned out.
  The ground wire is loose.
  Dirt has gotten into the power outlet or plug.

What to do ?

Resolder any disconnected wires and replace any parts that appear damaged. Connect the ground wire properly, then clean and dry everything thoroughly.

The polyimide heater  blows the resistance wire

Why ?

• There’s a short circuit, perhaps because the heating element has burned out, or because poor maintenance has allowed dirt to accumulate in the socket.
• The resistance wire diameter is too small and the capacity is insufficient.

What to do ?

As always, replace defective parts, solder, and clean thoroughly! If necessary, it may also be helpful to replace the power plug or electrical outlet.

Tips for Preventing Short Circuits in Polyimide Heating Elements

As important (if not more so) as knowing how to react in the event of a technical problem: being able to anticipate them!
Of course, you intend to choose quality materials (suitable for your project) and scrupulously follow your supplier’s recommendations. This is a good first step, but you can go a little further by adopting the right practices to preserve your polyimide heaters as much as possible.

Once the heater type has been carefully chosen, ensure proper voltage and wattage to avoid overheating and material breakdown. Consider integrating cut-offs or fuses as well as temperature sensors, such as thermocouples or resistance temperature detectors, to ensure optimal power regulation.

Maintain electrical safety by grounding your polyimide heater appropriately, and perform regular maintenance.

Also, it is generally estimated that an inspection should be performed every 6 to 12 months. Of course, your installation may require more intensive attention if operating conditions dictate. High thermal cycles, exposure to toxic environments, or the need for extremely precise thermal management (aerospace, laboratories…) may require quarterly inspections.
In all cases, pay attention to the condition of the electrical resistance (the resistance for a typical 24V polyimide heater might range between 10–100 ohms), the presence of cracks and discoloration, and the condition of the connectors and wires.

Finally, to help you guarantee the performance and safety of your polyimide heaters, do not hesitate to rely on industry standards and compliance.
Underwriters Laboratories, ISO 9001 and ISO 13485, MIL specs, ensure you comply with the standards defined for your field of activity. While insulation resistance can be tested in accordance with ASTM D257 or IEC 60093.

Proactive Maintenance for Long-Term Reliability

Polyimide heaters, as reliable as they are, benefit from regular maintenance. Be proactive in your inspection and diagnostic programs, and you will significantly reduce the risk of short circuits and performance impairment.

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