EM Absorbing Gap Pads Simplify Material Needs, Enable High-Performing ADAS Components

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By 2030, McKinsey estimates 12 percent of vehicles will be equipped with Levels 3 and 4 Autonomous Driving capabilities, compared with only 1 percent in 2025.

This increase in the number of automotive electronic sensors, which tend to use higher radio frequencies (up to 77GHz), coupled with electronic devices becoming more power intensive, creates two critical concerns – electromagnetic interference and overheating.

Both can lead to damaged components, malfunctions, equipment errors, reduced component life, failure and more.

Thermally conductive EM absorbing material combines electromagnetic attenuation and effective heat dissipation in one material – with typical application on ADAS components, such as radars.

Optimizing EM Absorption and Thermal Conductivity

The formation of an efficient thermal pathway combined with good EM absorbing characteristics requires a precise choice of chemistries.

To achieve both, the thermal and EM absorbing properties need a very precise filler ratio with both thermally conductive fillers and EM absorbing fillers dispersed within the polymer matrix. It is desirable to use multifunctional fillers that are both thermally conductive and absorb EM radiation for optimum performance/processing/cost benefits.

Thermal conductivity is achieved by forming an efficient thermal pathway determined by a variety of parameters, including:

EM attenuation is the result of absorption and reflection by EMI Gap Pads, and high absorption is required to maintain in-cavity signal fidelity when resonance is an issue. Data below demonstrates that correct choice of filler systems significantly increases the EM absorption (SEA) between 50-70GHz.

Materials capable of interacting with both the magnetic and electrical components of the radiation effectively absorb incident EM waves and dissipate the energy. As the shielding efficiency by absorption (SEA) and reflection (SER) varies with frequency, it is important to optimize the filler system for target frequency.  

SE vs Frequency Chart Image

Both the EM attenuation (measured at 18GHz) and the apparent thermal conductivity increase as the concentration of multifunctional fillers increases as shown below. Multifunctional fillers give various benefits including lower cost, lower density and better processability due to the lower filler loading required to achieve both thermal and EM attenuation targets. It is challenging to achieve high performance for EMI Gap Pads without multifunctional fillers.

Thermal conductivity and EM attenuation graphic

EMI Thermal Gap Pad Solution for Additional Performance Enhancement

Traditionally, EMI Gap Pads are made using a silicone rubber matrix, as the material offers adequate thermal stability. However, silicone can result in silicone bleed, which can impact electronic component functionality over time.

Henkel’s BERGQUIST TGP EMI 4000 is made of a silicone-free resin that offers thermal conductivity up to 4.0 W/mK and electromagnetic attenuation up to 90dB at 77 GHz.

The highly conformable nature of the material enhances wet-out, resulting in higher thermal performance. Additionally, an inherent natural tack of the material eliminates the need for thermally impeding adhesive layers while improving handling during assembly.

From a sustainability perspective, the silicone-free solution eliminates hazardous D3 to D6 siloxane rings – helping to meet tightening environmental regulations.

Review additional information about BERGQUIST TGP EMI 4000 here.

Product Characteristics