Temporary Bonding of Wafers, Displays, and Components

Abstract

Packaging practices are conducted on work unit substrates while they are temporarily held in place. This requires a simple adhesion process that enables easy removal without the burdens of complex cleaning. Substrates may be wafers, flexible displays, or components, organic or inorganic, and may contain topography such as solder bumps. The choice of a temporary bonding medium is dependent upon its ability to resist exposure to heat and chemicals. Thermal resistant materials as polyimide (PI), bisbenzocyclobutene (BCB, DOW CycloteneTM), or silicone can support processes that exceed 300°C, depending upon exposure conditions. In building flexible displays, PI materials are popular choices as a substrate processed from liquid and film forms. [1] These products may use silicone polymers, providing low outgas and inert character with an adhesive force tuned to allow substrate removal by peeling without a loss of integrity. Similar approaches are used for discrete, thin, fragile components, attached by dry bonding, processed, and removed by simple peeling practices without observed residue. Examples of die temporary bonding include encapsulation during bumping, permanent bonding, or vacuum deposition of EMI/RFI shielding. [2] The success in these and other technologies depend upon the use of the proper adhesive but most importantly, the tuning of the adhesion force. Successful tuning depends upon many factors, including substrate surface energy, texture, and the bonding process. Daetec has created adhesives used in temporary bonding processes for nearly 20yrs, applying to multiple wafer types, OLED and TFT displays, printed electronics, solar, thinning down to 4um, and thermal resistance >600°C. [3] Our experience in creating solutions for these and other industry needs will be discussed as well as the criteria to temporarily support flexible and rigid substrates of all types, sizes, and shapes.