The electronics industry often uses resin-based materials (such as semi-curing sheets, solder resistance inks, glues, and three anti-paint) to achieve structural bonding or electrical insulation. Whether the resin material can be fully cured directly affects the binding force of the material, and then affects the quality and reliability of the product. Therefore, in the actual use of the process to ensure that this resin material is completely cured, the monitoring of the curing rate is essential. The curing rate is an index to evaluate the chemical and physical state of the resin material from liquid or semi-solid to solid. By measuring the curing rate, the reaction degree of the cured sample can be observed and the performance of the material can be controlled in actual use. There are many commonly used measurement methods, and FTIR Fourier transform infrared spectroscopy is a simple and easy monitoring technology. The following uses UV-curable adhesive as an example to illustrate the application of FTIR infrared spectroscopy in determining the curing rate. 1.1. Test tools and methods Bruker ALPHA II Fourier transform infrared spectrometer was used to place the sample to be tested on the ATR crystal of the sample table, and the test procedure was started to obtain the infrared spectrum. The test was performed three times in parallel at three different locations of the same sample. 1.2. Wave number range of sample test parameters: 4000-400cm-1; Resolution: 4cm-1; Scanning times: 32 times. 1.3. Curing rate calculation principle Quantitative analysis of infrared spectrum is based on the measurement of the peak area of the characteristic absorption spectrum to calculate the content of each component, the theory is derived from Lamberbier's law. In this test, the relative peak ratio method was adopted, the infrared spectrometer was used to test the infrared spectra of uncured raw materials and cured samples respectively, and the software was used to integrate the selected measurement peak and reference peak, and the curing rate was obtained according to the curing rate calculation formula. Uv-curable adhesive is irradiated by ultraviolet light, where -C=C- is polymerized and reacts to form C-C-. The curing rate can be determined by -c =C- change. The shape of the C-H plane on the carbon-carbon double bond is variable and oscillates between 1010-667cm-1. The common peak of UV glue is 810±5cm-1, and the peak in this area is relatively single, easy to distinguish and strong, so it is calculated as the measurement peak. At the same time, in the curing reaction, C=O and C-O in the UV glue do not participate in the reaction, the content is basically unchanged, and C=O (1720 cm-1) or C-O (1150cm-1) is usually used as a reference peak. Due to the high intensity and obvious characteristics of peak C=O measured in practice, the characteristic peak C=O is selected as the reference peak for calculation. The calculation formula is as follows: M'/R' : the ratio of peak area between the cured measurement peak and the reference peak M/R: the ratio of peak area between the uncured measurement peak and the reference peak 1.4. Curing rate calculation results The same sample was tested in parallel for 3 times in this experiment, and the average value was the curing rate result. Table 1: Sample curing rate test data and results 2. Advantages of FTIR in the determination of UV adhesive curing rate • Non-destructive testing: FTIR is a non-destructive test that does not cause any damage to the sample and is suitable for valuable or more limited samples. • Fast response: FTIR is able to complete tests in a short time to meet the needs of rapid quality control. High sensitivity and specificity: FTIR is able to detect small chemical changes, providing precise quantitative analysis of the curing process. 3. FTIR Determination of UV glue curing rate Summary The use of FTIR testing of UV glue curing rate is simple and fast, reliable results, no pre-treatment, no consumption of chemical reagents, and environmental protection and safety. This test method requires a small sample size, basically non-destructive sample, suitable for sample non-destructive testing. In summary, FTIR testing of curing rate is a very valuable technical means for the evaluation of resin electronic materials and processes. In addition, in failure analysis, the technology can also help resolve failure problems caused by insufficient curing of materials. ZESTRON R&S (Reliability and Surface Technology) has extensive global experience in surface interface analysis, risk analysis, failure analysis and more. At ZESTRON's North Asia Analysis Center, The Technical analysis methods used by R&S include but are not limited to high definition digital microscope eye inspection, ion chromatography IC, ion contamination test ROSE, Fourier transform infrared spectroscopy FTIR, coating reliability test CoRe test, particulate matter determination/technical cleanliness Cleanliness, scanning electron microscope/X-ray Energy Spectrum Analyzer (SEM/EDS), X-ray photoelectron Energy Spectrum XPS, Auger electron Energy Spectrum AES, Coating Layer Test, Flux/Resin Test, contact Angle measurement Contact Angle, surface insulation resistance measurement SIR, differential thermal analysis DTA, etc. R&S experts not only assess the risk of failure and recommend preventive measures, but also analyze validation test failures and field failures at the mechanistic and root cause levels. If you are interested, please contact us at academy-china@zestron.com! .
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