Laser Processing of 3M™ VHB™ Tape 4926

Introduction

3M™ VHB™ Tape 4926 is part of a product line of foam core double-sided adhesives including 4919F, 4936(F), 4941(F), 4974F, 4956(F), 4991, and 4991B. The 3M™ VHB™ Tape 4926 product is a three layer material consisting of a core layer of closed cell acrylic foam that is placed between two layers of densified kraft paper release liner. The acrylic foam core of the 3M™ VHB™ Tape 4926 is 381 micron thick and each kraft paper release liner is 76 micron thick. A diagram depicting the 3M™ VHB™ Tape 4926 material is shown in Figure 1.

Figure 1. 3M™ VHB™ Tape 4926 diagram showing the 76µm densified kraft paper release liners on the top and bottom of the 381µm thick acrylic foam adhesive.

3M™ VHB™ Tapes are viscoelastic adhesives, having both elastic and viscous characteristics, along with being resistant to both chemicals and moisture. The viscoelasticity along with the tacky nature of this material makes it challenging to process using conventional mechanical methods. The non-contact nature of laser processing overcomes this difficulty, enables the processing of applications with fine geometry and intricate detail. 3M™ VHB™ materials are only suitable for laser cutting which produces smooth laser-processed edges and minimal heat-affected zones, without degrading the physical properties of the materials. Other laser processes are not suggested as they are not conducive to the intended use of these materials. Universal Laser Systems makes it simple to consistently and repeatedly process these materials to a high degree of dimensional accuracy, since the non-contact nature of laser processing eliminates material deformation during processing.

Laser Processing Notes

3M™ VHB™ Tape 4926 was tested to assess laser processing compatibility and to determine the best configuration of laser peak power and wavelength. The three layers of the 3M™ VHB™ Tape 4926 absorb 9.3 micron energy more efficiently than other wavelengths, meaning less peak power was necessary to produce good results with minimal heat affects. Laser processing of 3M™ VHB™ Tape 4926 produces a small amount of debris that adheres to the processed edge, requiring some cleaning by wiping the processed edge with a solvent such as isopropyl alcohol. Microscopy images taken at 300x magnification of the processed edge of the 4926 after post-processing with the liners in place and the liners removed are shown in Figures 2 and 3, respectively. These images show that the kraft paper release liners contain most of the heat affects and discoloration, leaving the acrylic foam layer relatively free of adverse heat effects.

Figure 2. Microscopy image (300x) of the laser-processed edge of 3M™ VHB™ Tape 4926 with the kraft paper release liners in place. The heat-affected zone measures 135µm

Figure 3. Microscopy image (300x) of the laser- processed edge of 3M™ VHB™ Tape 4926 with the kraft paper release liners removed from the material. The heat affected zone measures 65µm

Further analysis of the laser-processed material shows that the kraft paper release liner and acrylic adhesive layer is cleanly processed along the processed path, the the best configuration being a 75 watt 9.3µm CO2 laser source. Figures 4 and 5 depict 3D-rendered microscopy images of the processed surfaces shown in Figures 2 and 3. Figure 4 shows how the kraft paper release liner layer reacts to the laser energy by forming a consistent edge along the processed path (red area). In Figure 5, the kraft paper release liners are removed from the material, showing the smooth flat surface and laser-processed edge of the acrylic foam adhesive layer, free of adverse heat effects.

Figure 4. 3D-rendered microscopy image (300x) of the laser-processed edge of the 3M™ VHB™ Tape 4926 with the kraft paper liners in place.

Figure 5. 3D-rendered microscopy image (300x) of the laser-processed edge of the 3M™ VHB™ Tape 4926 with the kraft paper liners removed.

3M™ VHB™ Tape 4926 was also tested with an alternate system configuration of 10.6 micron laser energy at equivalent laser power level for comparison and determination of the effectiveness of each system configuration. The results of these tests were compared by analyzing the heat effects, quality of the processed edge 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 6. Both system configurations appear viable with some reduction in quality of the results for the 10.6 micron configuration as stated in the comparison.

Table 1 System Configuration Comparison

System ConfigurationHeat-Affected ZoneProcess CharacteristicsPost-Processing Requirements
9.3 Micron (Recommended)Minimal heat-affected zone of approximately The 9.3 micron laser energy Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
10.6 MicronLorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

Figure 6. Comparison microscopy images (300x) of the processed edge resulting from 9.3 micron processing (left), and 10.6 micron processing (right). Heat-affected zones measure 104µm for the 9.3 micron process and 156 micron for the 10.6 micron process.

Processing Example

3M™ VHB™ Tape 4926 applications requiring fine geometry and intricate detail without degrading the physical properties of the material can be accomplished with Universal Laser Systems technology. An example demonstrating the results of laser processing of 3M™ VHB™ Tape 4926 material is shown in Figure 4.

Figure 4. Example of the geometry possible with laser processing 3M™ VHB™ Tape 4926.

Conclusion

3M™ VHB™ Tape 4926 is suitable for laser processing and was extensively tested to determine the most efficient processing configuration. Through this testing it was determined that laser processing is viable with this material, and a 75 watt 9.3 micron CO2 laser source is the best configuration of wavelength and power for the processing of this material. The kraft paper release liner and acrylic adhesive layer efficiently absorb the 9.3 micron wavelength laser energy, and coupled with the peak power of the 75 watt laser source, produce a smooth clean processed edge that has a minimal heat-affected zone and discoloration. Other materials in this VHB™ product line are expected to process similarly.