Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-11-21
1999-07-06
Marquis, Melvyn I.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
528 51, C08K 332, C08L 6302
Patent
active
059198435
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to flame-resistantly formulated, flowable, latently reactive, phenolically curable epoxy-resin moulding compounds for the encapsulation of electronic components.
BACKGROUND OF THE INVENTION
In electronics, filler-containing moulding compounds based on epoxy resins are used for the encapsulation of active and passive components. Examples of such applications are the encapsulation of capacitors, diodes, transistors, power semiconductors, optocouplers, memory chips and microprocessors. Suitable epoxy-resin moulding, compounds for this purpose must fulfil high requirements relating to the processing and moulded-material properties. This relates, in particular, to the purity of the moulding compounds and also to the rheological behaviour and the curing properties during processing as transfer moulding compounds by means of transfer moulding processes and, furthermore, to the mechano-thermal properties of the epoxy-resin moulded materials and to the stable long-term protection of the components against aggressive environmental influences. In addition, the epoxy-resin moulded materials must fulfil the high requirements of electronics relating to the flame-resistant behaviour and achieve the classification V-0 for a layer thickness of .ltoreq.1.6 mm in the internationally standard flammability test according to UL 94 V.
The curing of epoxy-resin moulding compounds can in principle be carried out with chemically varied hardener components, for example with carboxylic anhydrides, amines or phenols. However, phenolically curable epoxy-resin transfer moulding compounds heavily filled with synthetic silica flour have gained acceptance for the encapsulation of electronic components by means of transfer moulding processes.
The phenolically curable epoxy-resin transfer moulding compounds at present used industrially contain, as a rule, 10 to 30% of organic components and 70 to 90% of inorganic components. In most cases, the chemical basis of the resin components is composed of cresol-novolak epoxy resins. Phenol novolaks are predominantly used to cure the epoxy resins; the reaction is accelerated, for example, with triphenylphosphine, phenylphosphonium borate and 2-ethyl-4-methylimidazole. Silicone-modified epoxy-resin components are used in the moulding compounds to improve the low-stress behaviour (in this connection, see German Offenlegungsschrift 42 23 632).
The flame-resistant formulation of the compression-moulding compounds is carried out using aromatic bromine compounds, in particular with tetra-bromobisphenol A epoxy resins, which are chemically incorporated in the epoxy-resin moulded material during curing. In addition, antimony trioxide increases the effectiveness of the brominated flame retardants as a synergist. The flame-resistant properties of the epoxy-resin moulded materials are further promoted by a high content of silanized synthetic silica fillers; in this connection, both splintery fillers and mixtures of splintery and spherical fillers are used. Recently, synthetically produced .alpha.-radiation-free synthetic silica fillers have been used to avoid so-called soft errors in large-scale-integrated circuits. The high content of silanized synthetic silica filler also serves to improve the mechano-thermal properties of the epoxy-resin moulded materials, in particular to adjust the coefficients of expansion. The compression-moulding compounds also contain, in addition, small amounts of additives, in particular soot, and processing aids, such as stearates and waxes.
To produce the phenolically curable epoxy-resin transfer moulding compounds, the resin and hardener components are converted into a pre-reacted state (B stage) and pulverized, as a rule, at temperatures up to approximately 120.degree. C., in particular by kneading on a roll mill or by extrusion, for example by means of a screw compounder. To process the transfer moulding compounds by means of transfer moulding processes, the moulding-compound powder is generally pelletized and, if necessary, the p
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Donner Peter
Kretzschmar Klaus
Schreyer Michael
von Gentzkow Wolfgang
Aylward D.
Marquis Melvyn I.
Siemens Aktiengesellschaft
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