Dielectric curing

The first attempt to use these ideas in epoxy cure was by Fisch and Hofmann 66), but their assignment of permittivity changes to changes in polar group concentrations was marred by what we interpret as electrode polarization effects. Blyakhman et al. 51 52), examined the post-cure dielectric permittivity and loss tangent of anhydride-... 

Day, D, R. Effects of stoichiometric mixing ratio on epoxy cure — dielectric analysis, SPE Tech. Papers, 31, 327 (1985)... 

There are several factors to observe in laser via processing position accnracy of lased holes (microvia holes), uneven diameters of holes, dimensional change of the panel after curing dielectric, dimensional change of the panel due to temperature and humidity variations, alignment accuracy of the photoexposure machine, unstable nature of negative artwork, and so on. These should be carefully monitored and are important for all microvia hole processes. 

X compressive to ASTM D905 wood, 24 hr cure. Dielectric strength >19MV/m. 

During the press operation, which is actually a form of compression mol ding, the resin-treated laminate pHes are heated under pressure and the resins cured. The initial heating phases cause the resin to melt and flow into voids in the reinforcing ply and bond the individual pHes together. The appHed heat simultaneously causes the resin to polymerize and eventually to cross-link or gel. Therefore, resin viscosity reaches a minimum during the press cycle. This is the point at which the curing process becomes dominant over the melt flow process. Dynamic mechanical and dielectric analyses (11) are excellent tools for study of this behavior. 

Sihcones (qv) have an advantage over organic resias ia their superior thermal stabiUty and low dielectric constants. Polyurethanes, when cured, are tough and possess outstanding abrasion and thermal shock resistance. They also have favorable electrical properties and good adhesion to most surfaces. However, polyurethanes are extremely sensitive to and can degrade after prolonged contact with moisture as a result, they are not as commonly used as epoxies and sihcones (see Urethane polymers). 

In a formed coil system each individual coil is pre-formed. insulated and cured, and is made rigid before it is inserted into the slots. The dielectric qualities of the coil insulation are monitored closely during the process of coil formation to ensure the required quality. For procedure and acceptance norms see Section 11.4.9. 

Cure systems based on hydrosilylation can be formulated as one and two-part silicone products, that can be either flowing or non-flowing. These formulations provide fast thermal cure rates, they are resistant to humid and other harsh environments, and they have good dielectric properties. These formulations can be self-priming or alternatively the substrate may require priming before application of the silicone. 

Gel time values of the three systems measured as abrupt change in the slope of G (t) under isothermal curing conditions show that gelation occurs earlier in PWE system at all temperatures considered as shown in Table 11.27. ETPI behaves like a catalyst for the primary epoxy-amino reaction which dominates the cure until vitrihcation occurs. Dynamic mechanical analysis and dielectric spectroscopic analysis carried out by the authors also confirm the above conclusions. 

Microwave curing of polymeric materials requires the presence of dipolar materials for effective modification to occur through dielectric heating [45]. This is not an essence in the case of EB modification of polymers which requires the presence of only labile reactive site, e.g., hydrogen in the polymeric stmcture. 

Relation [1] Is the frequency-dependent analogue of a formula proposed by Chasset and Thirion (2, 3) which has since been applied very frequently to relaxation measurements on cured rubbers. The next three equations are Inspired by similar relations In dielectrics (they are not derived from these) Equation [2] by the Cole-Cole and Equation [3] by the Davidson-Cole relation (15, 16). Both are special cases of the most general Equation [4] which contains five parameters (17). 

Figure 4.6. Cross-sectional SEM images of an A1PO film deposited on Si02 and cured at (a) 275 °C, and (b) flash annealed to 600 °C. [Reproduced with permission. Meyers, S. T. Anderson, J. T. Hong, D. Hung, C. M. Wager, J. F. Keszler, D. A. 2007. Solution processed aluminum oxide phosphate thin-film dielectrics. Chem. Mater. 19 4023-4029. Copyright 2007 American Chemical Society.]...

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