Ultraviolet Polymerization of Gaseous Monomers
Gaseous monomers adsorbed onto a surface may be polymerized by exposure to uv light either in the presence or absence of air. The most
*A Lewis acid is defined as a compound whose electron orbitals can accept electrons, e.g., boron trifluoride. Conversely, a Lewis base is an electron donor, e.g., triethylamine or other tertiary amines.
Microwave Curing
Variable frequency microwave (VFM) curing is a recently developed process for rapid curing of polymer coatings, adhesives, and encapsulants.[56] It differs from conventional microwave processing in using swept frequencies rather than a fixed frequency. Variable frequency microwave utilizes three parameters: central frequency, frequency bandwidth, and sweep rate. Through the sweeping process, problems of non-uniformities in temperature and arcing associated with conventional microwave ovens are avoided. Variable frequency microwave curing is reported to be 2 to 10 times faster than conventional heat curing. A further advantage is that it permits uniform distribution and precise control of microwave energy and heats large sections uniformly. Compared with conventional heat curing, VFM curing was found to offer similar die stress levels and reliability and reduced warpage of FR-4 laminate substrates onto which it was applied.[57] Since 1994, Lambda Technologies has pioneered the VFM process and has commercialized it through the development of microwave equipment.