ADVANCED MATERIALS & PROCESSES | OCTOBER 2025 28 The Raman spectral interpretation of failed parts returned from the field is shown in Fig. 5a, and samples that failed in the manufacturing location are shown in Fig. 5b. Both sets of samples predominantly show peaks consistent with the thermal pads in the range of 2700 to 3200 cm-1. Under- standing the main mechanism of failure through root cause analysis in a scientific way is challenging in a manufacturing environment. CONCLUSION This case study demonstrates the power of Raman spectroscopy as a diagnostic tool for detecting silicone contamination in adhesive bonding applications. Its ability to identify specific molecular signatures with high sensitivity makes it an invaluable asset in failure analysis and quality assurance. By integrating Raman spectroscopy into the root cause analysis process, manufacturers can quickly identify contamination sources, implement corrective actions, and prevent costly failures. This approach enhances product reliability and supports continuous improvement in manufacturing practices. As the demand for high-performance, miniaturized, and reliable electronic systems grows, the importance of advanced analytical techniques like Raman spectroscopy will only increase. This innovative application sets a new standard for contamination detection and process control in precision manufacturing. ~AM&P Acknowledgment The author gratefully acknowledges the support of ZF Group in conducting this investigation and the contributions of the materials engineering team. For more information: Aravinda Bommareddy, principal engineer, materials, ZF Group Electronics, 34605 W. 12 Mile Rd., Farmington Hills, MI 48331, aravind.bommareddy@zf.com. References 1. E. Petrie, Addressing Silicone Contamination Issues, Metal Finishing, July 2013. 2. G.D. Davis, Contamination of Surfaces: Origin, Detection, and Effect on Adhesion, Surface and Interface Analysis, 20, p 368-372, 1993. can be performed with minimal sample preparation. Raman spectroscopy is used to observe vibrational, rotational, and other low-frequency modes. Spectral characterization of peaks below 650 cm-1 typically indicates inorganic compounds (e.g., metal oxides, silicates, and SiC); peaks between 1500-2000 cm-1 indicate double bonds; and peaks between 2500-4000 cm-1 indicate single bonds. Initially, Raman spectrum was collected for the thermal pad itself as a control sample, as seen in Fig. 3a. The spectral range from 700 to 3100 cm-1 for the thermal pad matched 95% with the spectral library for silicone oil. Figure 3b shows the spectral intensity collected from the cured adhesive of a good part. Figures 4a and b compare the failed lens mount part with the thermal pad’s spectral signature and the good adhesion spectral signal strength. It was found that the failed part traces matched exactly with the thermal pad C-H bond region, as seen in Fig. 4a. In contrast, the good part traces did not match the silicone spectrum C-H region, as shown in Fig. 4b. (b) (a) Fig. 5 — (a) Raman spectral peaks of orange and green are consistent with the thermal pad (black) in the range of 2700-3200 cm-1. (b) Raman spectral peaks of orange and green of internal failed parts are consistent with the thermal pad (black) in the range of 2700-3200 cm-1.
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