Characterizing adhesives for optoelectronics

Optoelectronic packages are made with materials systems comprising ceramics, metal alloys, glasses, and polymers. The interplay between the properties of these materials determines stability and reliability of optoelectronic packages. A major reliability concern is the fact that optoelectronic packages exhibit extreme sensitivity to minute changes in the geometry of the system. Misalignment of optical components at the submicron scale can result in significant optical losses. As a result, the interplay of material properties may limit the short-term life of a unit that has no physical defects otherwise. Materials most likely to be involved with such misalignment issues are organic adhesives. The thermal expansion coefficients of organic materials are significantly higher than that of the inorganic materials used in optoelectronic packaging. In addition to large CTEs, organic materials are prone to creep since their glass transition temperatures are close to the operating temperatures of the package. This paper summaries our efforts in characterizing the dimensional stability of adhesives.