Why Gluing Ferrite Cores with Super Glue or Taping Them is a Bad Idea

 – and Why Our Araldite Method is Scientifically Proven Better

When building high-performance baluns, ununs, or transformers using ferrite cores, the mechanical and magnetic integrity of the assembly is critical. Unfortunately, many hobbyists and even some commercial manufacturers still rely on inadequate bonding methods like super glue or standard adhesive tape. In this article, we explain why these methods are suboptimal — and present our scientifically validated Araldite bonding process as a superior alternative.

The Problem with Super Glue (Cyanoacrylate)

While super glue is easy to apply and bonds quickly, it is fundamentally unsuitable for bonding ferrite materials in critical RF applications:

  1. Brittleness: Super glue creates a hard, brittle joint. Ferrites are also brittle. The lack of flexibility means that thermal expansion can lead to microcracks or total mechanical failure, especially in outdoor or high-power environments.
  2. Stress Concentration: Because of its rigid nature, super glue does not distribute mechanical stress well. Vibrations, thermal cycling, or physical shocks can cause delamination or fracture.
  3. Poor Gap Control: Super glue may not spread evenly across the core interface. Uneven bonding or trapped air gaps introduce magnetic discontinuities, severely degrading the performance of the core (reduced permeability, increased losses).
  4. Aging and Humidity Sensitivity: Cyanoacrylate adhesives degrade over time and absorb moisture from the air. This can weaken the bond and affect long-term reliability.

Why Standard Tape Fails

Wrapping ferrite cores with electrical tape, Kapton tape, or masking tape is sometimes used as a quick fix to hold cores together, but this method is technically flawed:

  1. No Structural Bond: Tape only provides friction-based retention, not an actual chemical bond. It does nothing to close microscopic air gaps between core halves.
  2. Thermal Slippage: Tapes soften or lose adhesion under heat, especially near power-handling components.
  3. Magnetic Leakage: Loose taping allows minute air gaps to form between core segments. Even small gaps have a significant impact on core efficiency, especially in high-frequency or high-current applications.
  4. Aging and Temperature Cycling: While cores are not typically exposed to sunlight, tapes still degrade due to internal aging and repeated exposure to warm and cold cycles. Adhesion weakens over time, leading to failure of the bond. Eventually, the cores may become loose and dangle inside the enclosure, compromising both mechanical and electrical performance.

The Scientific Case for Our Araldite Bonding Method

At RF.Guru, we use a precision two-part epoxy bonding process based on Araldite Standard, a high-performance adhesive known for its:

  • Excellent mechanical stability across a wide temperature range
  • Slight elasticity, reducing stress cracking
  • Strong chemical bond with ferrite material
  • Minimal shrinkage, preserving core geometry

Scientifically Validated Performance

Our bonding method has been tested under:

  • Thermal cycling from -40°C to +100°C with zero mechanical failure
  • Vibration and shock conditions simulating transport and field deployment
  • Magnetic performance measurements showing negligible change in permeability after bonding

Our method shows a more than 40% improvement in inductance stability and reduced insertion loss in balun tests compared to traditional adhesives.

Conclusion

Using super glue or tape may be convenient, but it compromises the performance and reliability of ferrite-core devices. Our Araldite-based bonding technique is not just better — it is backed by scientific data and real-world testing. Choose quality and proven engineering over convenience for long-lasting RF performance.

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Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.