Hidden Corrosion of Conductive Silicone Rubber: How Micro-Scale Electrochemistry Undermines EMI Reliability
In communication base stations and new energy vehicles operating under high temperature and humidity, even advanced conductive silicone rubber (also called electrically conductive rubber or conductive foam rubber) may suffer sudden EMI performance degradation after 18–24 months.
Failure analysis often reveals white flocculent oxides on metal surfaces, blackened edges of conductive fabric, and sharp increases in contact resistance. Surprisingly, the issue is not material aging itself, but micro-scale electrochemical corrosion—a hidden but critical reliability threat.
This article explores how micro-condensation, dissimilar metal contact, and DC bias together form localized galvanic cells at the conductive rubber interface, leading to ion migration, oxide deposition, and eventual EMI shielding failure.
As Precision Mounting Technology of SMT Gaskets: Reflow Soldering Compatibility and Micro-Stress Control focused on mechanical reliability, this article shifts to the electrochemical dimension: when water, electricity, and metals meet, the true test of EMI reliability begins.
The “Three-Element Model” of Electrochemical Corrosion
Corrosion initiates only when these three conditions coexist:
-
Electrolyte presence: Condensed moisture forms thin liquid films (RH > 60%).
-
Dissimilar metals: Nickel–copper conductive fabric in contact with aluminum housings creates a potential difference (ΔV > 150mV).
-
DC bias path: Grounding differences generate micro-currents that drive corrosion.
At this point, the interface behaves like a miniature galvanic cell:
-
Anode (aluminum housing): Al → Al³⁺ + 3e⁻ (oxidation, forming white Al(OH)₃).
-
Cathode (nickel–copper layer): O₂ + 2H₂O + 4e⁻ → 4OH⁻ (alkaline environment accelerating copper corrosion).
Corrosion Pathway: From Pitting to Shielding Failure
-
Micro-porous penetration – Moisture infiltrates through conductive fabric into the foam’s metallic coating.
-
Ion migration – Cu²⁺ and Ni²⁺ ions migrate under bias, forming conductive filaments or insulating oxides.
-
Contact degradation – Oxides accumulate at interfaces, increasing resistance and reducing EMI shielding.
Case Study: In one automotive T-Box test, contact resistance rose from 0.2Ω to 8.7Ω after damp heat exposure, with shielding effectiveness dropping by 20dB in the 300MHz–1GHz band.
Engineering Countermeasures: From Conductivity to Electrochemical Isolation
-
Material-level solutions
-
Replace nickel–copper coatings with silver plating (lower oxidation tendency).
-
Add nano-oxide diffusion barriers between conductive fabric and foam.
-
-
Structural design strategies
-
Equipotential grounding: eliminate DC bias by aligning housing and PCB ground.
-
Hydrophobic sealing: apply water-repellent coatings at joints to block film formation.
-
-
Environmental protection
-
Upgrade sealing from IP54 to IP67 to block moisture ingress.
-
Add internal desiccants to absorb residual humidity.
-
Detection and Early Warning of Corrosion Risk
-
Electrochemical Impedance Spectroscopy (EIS): Detects interface resistance changes at low frequency.
-
Micro X-ray Diffraction (μ-XRD): Identifies corrosion products such as Cu₂O or Al(OH)₃.
-
Accelerated DC-biased damp heat testing (85℃/85%RH + 5V): Simulates long-term degradation.
EMI Failures: An Electrochemical Accident in Disguise
The failure of conductive silicone rubber is often not due to material defects, but to overlooked electrochemical interactions at the system level.
Konlida is collaborating with clients to develop interface corrosion risk assessment models, making electrochemical stability a new benchmark in EMI shielding material selection.
As SMT Gaskets Design for Manufacturability: Ensuring Seamless Integration into Automated Production Lines emphasized precision in placement and compression, remember this: true reliability means surviving the electrochemical triangle of water, voltage, and metal—the ultimate test of precision electronics.
ABOUT US