TABLE OF CONTENTS After dispensing the adhesive and placing the devices, the adhesive must be cured, that is, it must be advanced from a liquid or semi-solid state to a solid state for full development of its adhesive strength and dielectric properties. In the broad sense, curing is the processing that is involved in altering the state of the adhesive material so that it can adequately bond two surfaces. In most cases, this involves polymerization of low-molecular-weight monomers or polymers through the application of heat or other form of energy. With prepolymerized materials, such as many thermoplastics, curing simply involves evaporation of the solvent (if there is a solvent) and heating to bring the adhesive up to its melt temperature. In other cases, as with polyimides, curing involves the formation of ring structures along a prepolymerized molecular chain by heating.
In a stricter sense, curing involves polymerization of monomer resins by reaction with a hardener or by initiation with catalysts and, generally, requires heat or another form of energy. Epoxy resins and other thermoset resins cure by forming a highly cross-linked structure either by condensation or an addition of polymerization (see Ch. 3). Some hardeners and catalysts for epoxy resins are so reactive that, upon mixing, curing takes place in a matter of minutes, even at room temperature. Among these fast curing agents are the primary and secondary aliphatic amines and the boron trichloride or trifluoride amine complexes. Other hardeners such as aromatic anhydrides require elevated cure temperatures for a...
