3M™ EMI Absorber AB5020HF is part of the AB Series of halogen-free sheet material made from polymeric resins, with various fillers designed to absorb a broad range of RF energy frequencies. AB5020HF consists of a 200µm thick flexible polymeric resin with magnetic metal flake fillers. Magnetic flakes aid in attenuating magnetic fields due to their high permeability and act to oppose electromagnetic interference by generating induced eddy currents. The loaded polymer resin is backed with a 50µm thick non-conductive pressure sensitive acrylic adhesive, which is subsequently backed with a 130µm silicone-coated paper release liner. A diagram depicting the layers of AB5020HF is shown in Figure 1.
Figure 1. 3M EMI Absorber AB5020HF diagram illustrating the polymeric resin with metal filler (200µm), the pressure sensitive adhesive (50µm), and the paper release liner (130µm).
3M EMI Absorber AB5020HF is used to absorb electromagnetic interference and helps suppress radiated noise from interrupting electronic devices. EMI absorbers are commonly used to reduce these EMI and RF emissions in electronics and are applied to noisy traces, ICs, and reflective surfaces in an enclosure. This material is most effective at absorbing frequencies between 200 MHz and 10 GHz. The non-contact nature of laser processing enables 3M EMI Absorber AB5020HF applications with small features and fine geometry to be processed without deforming the material, which may be difficult to achieve with traditional mechanical methods. AB5020HF is only suitable for laser cutting, which produces consistent edges and minimal heat-affected zones. MultiWave Hybrid™ technology, available from Universal Laser Systems, makes it possible to consistently and repeatedly process AB5020HF to a high degree of dimensional accuracy. Other laser processes are not suggested as they are not conducive to the intended use of this material.
Laser Processing Notes
3M EMI Absorber AB5020HF was tested to assess laser processing compatibility and determine the best configuration of peak laser power and wavelength. The polymeric resin, adhesive layer, and paper release liner that comprises AB5020HF absorbs 9.3µm wavelength laser energy more efficiently than other wavelengths, while the metal filler absorbs 1.06µm laser energy more efficiently than other wavelengths. Laser cutting of this material can be performed at higher processing speeds with minimal discoloration by using a MultiWave Hybrid configuration, in which 9.3µm and 1.06µm wavelengths of laser energy are simultaneously combined into a single beam to process the materials. A 300x magnification microscopy image of the edge after laser cutting the AB5020HF material is shown in Figure 2. The 3D image in Figure 3 depicts how the edge of the epoxy adhesive responds to laser cutting with the ULS MultiWave Hybrid configuration of a 75 watt 9.3µm CO2 laser source combined with a 50 watt 1.06µm fiber laser.
Figure 2. Microscopy image (300x) depicting the edge of AB5020HF after laser cutting. The heat-affected zone measures 40µm. The material was processed with both the adhesive layer and release liner in place.
Figure 3. 3D-rendered microscopy image (300x) illustrating the ledge of AB5020HF after laser cutting.
3M EMI Absorber AB5020HF was also tested with a single 9.3µm CO2 laser source and a single 10.6µm fiber laser source. The results of these tests were compared by analyzing the heat effects, the processed edge quality, and post-processing requirements. The results of the comparison of these system configurations are listed in tabular form in Table 1 and shown photographically in Figure 4. The 9.3µm and 1.06µm hybrid configuration produces a noticeably better edge when laser cutting this material and is the recommended configuration.
Table 1. System Configuration Comparison
System Configuration
Heat-Affected Zone
Process Characteristics
Post-Processing Requirements
MultiWave Hybrid 9.3µm + 1.06µm (Recommended)
Minimal heat-affected zone of approximately 40µm
This configuration results in a smooth, clean edge with minimal heat effects and minimal discoloration
No post-processing required
9.3µm
Increased heat-affected zone of approximately 75µm
This configuration results in increased discoloration and heat effects along the edge
10.6µm
Increased heat-affected zone of approximately 100µm
This configuration results in increased discoloration and heat effects along the edge.
Figure 4. Microscopy images (300x) of the edge of AB5020HF using the MultiWave Hybrid technology, with combined 9.3µm and 1.06µm wavelengths (left), the 9.3µm wavelength alone (middle), and the 10.6µm wavelength alone (right).
Processing Example
3M EMI Absorber AB5020HF applications requiring fine geometry and intricate detail without degrading the physical properties of the material can be achieved with the MultiWave Hybrid technology. An example demonstrating the results of laser cutting AB5020HF using the recommended system configuration is shown in Figure 5.
Figure 5. Example of the geometry possible when laser cutting AB5020HF.
Conclusion
3M EMI Absorber AB5020HF is suitable for laser processing and was extensively tested to determine the optimal processing configuration. Through this testing, it was determined that laser cutting is viable with this material and that using MultiWave Hybrid technology with both a 75 watt 9.3µm CO2 laser source and a 50 watt 1.06µm fiber laser source is the recommended system configuration. AB5020HF efficiently absorbs the 9.3µm and 1.06µm wavelengths to produce an edge that has only slight discoloration and a minimal heat-affected zone.
