Curing thermal

In addition to heat, some adhesives require the simultaneous application ofpressure. Examples include the bonding of substrates with thermoplastic film adhesives and the bonding of flip-chip and TAB devices with anisotropic 

Thermal Low cost Uses existing equipment Long cycle times for most formulations Incomplete cure may occur with fast cure, snap cure adhesives, depending on thermal mass 

Infrared Uses existing SMT equipment in place High throughput May require post curing 

Microwave Fast curing rates (fector of 10) over forced convection heating Reduced stress from CTE mismatched materials Cure schedules require optimization of many parameters Specialized equipment 

UV/visible Rapid curing increases production throughput Good for heat-sensitive devices Low production costs Reduced ena gy requirements Line of site process shadow area may require a thermal post-cure Requires photosensitive formulations 

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Adding amines to coating compounds containing other polymers of hydantoin derivatives permits thermal curing of the coating compounds, which are useful as electrical insulators of wires under a broad range of conditions without loss of coating flexibiUty (101). 

Fig. 2. Conventional thermally cured, organic solvent base coating system.

Hydrosilation silicones or addition cure systems utilize a hydride functional crosslinker with a vinyl functional base polymer and a noble metal catalyst. While the cure can be initiated with UV [48,49], thermal cure versions dominate the commercial market [23,50]. In thermal cure systems, inhibitors are necessary for processing and anchorage additives are common. 

Advantages of the hydrosilation system (Fig. 3) include the elimination of solvent, improved cure speed, and potential for UV or thermal cure. Drawbacks to the system include more expensive multiroll coating methods, potential poisoning of the Pt catalyst (with Sn, S, Cr, amines, etc.), poor anchorage to some films, and a need to carefully balance the hydride to vinyl ratio employed for cure to avoid detrimental interactions with acid containing adhesives [23,53]. 

Epoxy cured silicones were developed to be photo initiated rather than thermally cured [54]. The chain length of these materials ranges to 200 monomer repeat units, but the majority component of most formulations is significantly shorter. The structure of a typical base polymer is shown in Fig. 4. The chain can be terminal and/or pendant functional, with degree and type of epoxy function-... 

Thermal cure system. The thermal cure system is based on a hydrosilylation addition reaction between vinyl-functionalized and silicon-hydrido functionalized polysiloxanes [32,33,35], Unsaturated organic groups react with a Si-H functionality in the presence of a platinum-based catalyst (Scheme 10). 

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. 

Theoretically, this system offers the advantages of the thermal cure systems that include fast cure and low temperature processing. However, these systems are sensitive to atmospheric humidity and the possible toxicity of the catalyst may represent an issue. 

Preparation and thermal crosslinking reactions of oc, -vinylbenzyl terminated polysulfone-b-polydimethylsiloxane, ABA type block copolymers have been discussed 282,313) However, relatively little characterization was reported. Molecular weights of polysulfone and PDMS segments in the copolymers were varied between 800-8,000 and 500-11,000 g/mole, respectively. After thermal curing, the networks obtained showed two phase morphologies as indicated by the detection of two glass transition temperatures (—123 °C and +200 °C) corresponding to PDMS and polysulfone phases, respectively. No mechanical characterization data were provided. 

Polymeric phthalocyanines 3 are available from 1,2,4,5-tetracyanoben ne 2 by deposition from the vapor phase on hot substrate surfaces, or by thermal curing of its tetramer, octacyanophthalocyanine 4 in the presence of metal cations (Scheme 2... 

On the whole, curing procedures appear a promising way to obtain very stable polymer films. Thus, the structure of already mentioned polylysine has been revised as a block polymer involving either the a or e amino groups of lysine Vitamin Bj2 modified carbon electrodes were prepared by thermal curing of a mixture of a diamino functionalized derivative 5 and an epoxy prepolymer 6 of the araldite... 

An epoxy resin made by thermal curing of an araldite prepolymer with the 3,5-diaminophenylester of a peripherically modified vitamin as hardener on carbon... 

Chemicals like polyorthoaminophenol, diphenylamine in small amounts have been found to decrease the yield of cross-linking [388]. The tensile strength of the carbon black-filled polychloroprene compounds has been found to be comparable to the conventional thermally cured one. The physical properties [389] have been observed to improve on adding cross-linking promoters like A,A -hexamethylene-bis-methacrylamide into the polymer matrix. 

The physical properties of radiation and peroxide cured polysiloxanes have been compared by several investigators [402]. Vinyl-substituted (0.14 mol%) radiation-cured polysiloxane is found to have better strength properties than the chemically cured analogue. The phenyl substitution (7.5 mol%) has only marginal effect. The physical properties of radiation and thermally cured sUica-filled polyvinylethyldimethylsiloxane compounds are found to be similar. 

This work discusses the thermal crosslinking and isomerization reactions occurring in the acetylene terminated isoimide prepolymer Thermid IP600. The techniques of Fourier Transform Infrared Spectrometry and Differential Scanning Calorimetry are used to determine the contribution of these two reactions during the thermal cure including their kinetics at 183° C. 

NLO active molecules can be embedded in or chemically anchored to a sol-gel-matrix without changing the optical absorption spectrum. Disperse Red 1, a very efficient molecule for NLO applications, was embedded in a sol-gel-matrix, synthesized by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane in the presence of N-methylimidazole. The dye-doped gel was applied to glass substrates and thermally cured to form a layer of perfect optical transparency. Currently, poling experiments and NLO measurements with these layers are being performed. 

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