Two Novel Applications of Adhesives for Optical Microelectronics

Most of HEI’s custom and standard optical switches require one lens to focus light from an LED and another to collect and concentrate that light onto a photoelectric diode. Plastic lenses are typically glued into apertures in polycarbonate housings using a two ‐part room temperature cured adhesive. To reduce cost and increase productivity, lenses are fabricated in the apertures using an ultraviolet cured clear adhesive. This process eliminates the cost of moulded plastic lenses and reduces cure time from 24 hours to less than a minute. One of the custom optical applications requires bonding a coated glass cover over a cavity containing optical sensors and circuitry. Gas expansion causes ‘blow‐outs’ when heat cured adhesives are used and room temperature cured adhesives add a day to turnaround time. An ultraviolet cured adhesive increases productivity by eliminating blow‐outs and reducing turnaround time. A unique process has been developed in which the glass cover is placed over the cavity in a vacuum bell jar.