*Polyimide in Electronics: Applications and Processability Overview DOI: http://dx.doi.org/10.5772/intechopen.92629*


**Table 3.** *Main physical properties of aromatic and fluorinated*

 *polyimides*

 *(*data taken from *[8]).*

### *Polyimide for Electronic and Electrical Engineering Applications*

*Polyimide in Electronics: Applications and Processability Overview DOI: http://dx.doi.org/10.5772/intechopen.92629*

Microwave heating of polymers occurs because of dielectric loss mechanisms. When an external electric field is applied to a dielectric material, three types of polarization can occur [24]. These ones are the electronic, ionic or atomic, and orientational or dipolar polarization mechanisms. The main coupling mechanism between microwave radiation and polymer dielectrics is through dipole orientation under the applied electric field. The efficiency of coupling microwave energy into a polymer depends on different factors, which include the dipole strength, the dipole mobility and the dipole mass.

The VFM curing principle is to subject the deposited films to very high frequency waves (>1 GHz) causing the macromolecular structure to vibrate (see **Figure 11**). The vibrations then locally heat the coating which thus polymerizes. The advantages of the VFM curing method are the short annealing time. It is around 10 minutes only compared to a few hours for a conventional full thermal cycle. Moreover, the lower associated temperature (200°C) during the application of microwaves enables shorter curing cycles (see **Figure 12**). The industrial interest could be to replace standard thermal curing techniques with faster and lower cost VFM method.
