Stock material or miscellaneous articles – Composite – Of epoxy ether
Patent
1995-09-14
1997-07-15
Krass, Frederick
Stock material or miscellaneous articles
Composite
Of epoxy ether
428415, 428417, 428901, 523429, 523466, 528 27, 528103, 528108, 528367, 528368, 528398, 528399, 525502, 525504, 525505, 525507, 525525, C08G 5914, C08G 5950, H05K 103
Patent
active
056481713
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention concerns epoxy resin mixtures for producing prepregs and composites and it also concerns the prepregs and composites produced from said epoxy resin mixtures.
Composites based on epoxy resins and organic or inorganic reinforcing materials have gained an important position in many areas of the industry and daily life. The reasons include first the relatively simple and reliable processing of epoxy resins and secondly the good mechanical and chemical properties of cured epoxy resin molding materials that make it possible to adapt to a variety of applications and permit advantageous utilization of the properties of all the materials that make up the composite.
Epoxy resins are preferably processed to composites by the intermediate step of producing prepregs first. For this purpose, organic or inorganic reinforcing materials or embedding components in the form of fibers, nonwovens and woven fabrics as well as other flat materials are impregnated with the resin. In most cases, this is accomplished with a solution of the resin in a volatile solvent. The resulting prepregs according to this process must not be sticky but they should not be fully cured either. Instead, the resin matrix should simply be prepolymerized. In addition, the prepregs must have sufficient storage stability. Thus, for example, a storage stability of at least three months is required for the production of circuit boards. In further processing to form composites, the prepregs must also melt at higher temperatures and they must form a strong and permanent bond under pressure with both the reinforcing materials or embedding materials and the materials intended for the composite--in other words, the cross-linked epoxy resin material must yield a high interlaminar adhesion with the reinforcing materials or the embedding components and with the materials to be bonded, such as metallic, ceramic, mineral and organic materials.
In general, a high mechanical and thermal strength, good mechanical and thermal stability, thermal undeformability, and good aging resistance are required of composites when cured. For electrotechnical and electronic applications, there is also the requirement that the electric insulation properties must be permanently high, and for many special applications there are numerous additional requirements. For example, good thermal undeformability over a wide temperature range, good adhesion to glass and copper, a high surface resistance, a low dielectric loss factor, good machining properties (punchability, drillability), a low water uptake and high corrosion resistance are required if these materials are to be used as circuit board materials.
With increasing loads and extensive use of the composites, the thermal undeformability requirement becomes especially important. This means that the materials must withstand high temperatures during processing and use without showing any deformation or damage to the composite--due to delamination, for example. In dip soldering, for example, circuit boards are exposed to a temperature of 270.degree. C. Likewise, local temperatures of more than 200.degree. C. may occur briefly during cutting and drilling operations. Materials with a high glass transition temperature T.sub.G have good properties in this regard. If the glass transition temperature is higher than these temperatures, thermal undeformability is assured in the entire temperature range covered during processing, and damage such as warpage and delamination can be largely ruled out. The epoxy resin currently used on a large scale worldwide for FR4 composites has a glass transition temperature of only 130.degree. C. after curing. However, this results in the damage described above and thus leads to rejects in production. Therefore, there has long been a demand for inexpensive materials that can be processed relatively well and have a glass transition temperature higher than about 180.degree. C.
Another requirement that has become increasingly important in recent times is that these materials m
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Huber Jurgen
Kapitza Heinrich
Kleiner Hans-Jerg
Rogler Wolfgang
von Gentzkow Wolfgang
Krass Frederick
Siemens Aktiengesellschaft
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