A fiber optic sensor for real time monitoring of the curing/cured state of adhesives

Adhesives are widely used in the assembly of optoelectronic and/or electronic components. Based on the principle of Fresnel reflection, a fiber optic refractometer was set up to monitor the state of adhesives. The determined refractive indices of various liquids were consistent with their reference technical data. When taking a real time monitoring of adhesive refractivity on the refractometer, curing process of the adhesive and thermal expansion of the cured adhesive could be distinguished. Finally, the temperature dependence of the adhesive refractivity was verified with thermo-mechanical analysis through the Lorenz-Lorentz relation. Experimental results show that the setup can be a candidate replacement of thermal analysis apparatus.