JPH0127100B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to electrical grade self-extinguishing glass-based epoxy resin laminates.
The present invention includes electrically insulating quality laminates made using epoxy resin compositions and laminates made from B-stage prepregs. Fire-resistant and self-extinguishing reinforced resin laminates have long been known to those skilled in the art. Many prior art laminates use glass fiber or cloth, mica, or other inorganic reinforcing materials in conjunction with a resin component as a binder. In some instances, the resin binder was one of a flame retardant chlorinated or brominated epoxy resin in combination with one or more curing agents. For example, reference may be made to US Pat. No. 3,378,434, US Pat. No. 3,523,037, US Pat.
These entries are quoted here for reference. Although such laminates are fire resistant, they usually have deficiencies in some physical properties, such as machinability, especially drilling performance. It is clear that glass plays a major role in drill wear. It has now been discovered that some of the abrasive glass can be replaced by a very soft material, hydrated alumina, and surprisingly advantageous improvements in properties are obtained. The hydrated alumina is believed to act as a crosslinker between the silanol groups on the glass (or the silyl ether groups on the silanized glass) and the secondary hydroxy groups on the polymeric epoxy backbone. This epoxy glass interaction is evidenced by improved wetting of the glass fibers in drilled through holes made with this product and excellent insulation and volume resistance. Improved machinability of laminates made using hydrated alumina in epoxy to replace a portion of the glass results in reduced drill wear, improved hole quality and increased productivity, all of which of fundamental importance to the printed circuit board industry). Although the use of hydrated alumina in combination with epoxy resins has been known in the art, the prior art does not teach that superior laminated laminates can be made. For example, The Encyclopedia of Polymer Science and Technology, Volume 6, John Wiley & Sons, New York, pages 241 and 242, lists epoxy as a filler among many other fillers. Hydrated alumina is listed as a typical commercially available filler for resins, and US Pat. It is stated that when placed between conductors it provides insulation with excellent resistance to arc tracking. Both of these publications (both of which are incorporated herein by reference) state that hydrated alumina improves resin-to-glass wetting, intermolecular bonding, and that hydrated alumina improves glass bonding in laminates. No suggestion is given that partial substitutions may be made. Hydrated alumina is also unique in the amounts used here relative to other common additives or fillers, because after forming a laminate from an epoxy resin containing hydrated alumina, it becomes translucent. This is because the self-extinguishing property shows an improvement in flame resistance and significantly reduces smoke intensity and toxic gases, without any loss in properties. In accordance with the present invention, in its broad aspects, an epoxy resin for making a prepreg suitable for consolidation under heat and pressure into an insulating substrate for flame retardant glass-reinforced printed circuit boards with improved drilling properties. using a resin composition, the composition comprising: (a) a flame retardant amount of a chlorinated or brominated epoxy resin; (b) an effective amount of (i) a curing agent for (a); or (ii) a curing agent. A curing agent for (a) in combination with a catalyst; (c) from about 10 to about 40% hydrated alumina, based on the weight of (a) and (c); and (d) a suitable solvent. The present invention also includes, as an article of manufacture, a glass fiber sheet impregnated with the B-stage epoxy resin composition described above. Alternatively, among the important features of the present invention is an insulating substrate for a flame retardant printed circuit board comprising a number of saturated glass fiber sheets of the above epoxy resin composition united into an integral structure under heat and pressure. . Epoxy resin component (a) provides flame resistance,
It has at least a significant proportion of halogens such as chlorine or bromine, especially bromine. Halogenated epoxides can also be used with halogenated curing agent component (b), such as dichloromaleic anhydride, chlorendic anhydride, tetrachlorophthalic anhydride, etc., but as discussed below, this is not a necessary requirement. It should also be understood that non-halogenated (or standard) epoxy resins may also be used in the compositions in any proportion up to 100% by weight of the flame retardant halogenated epoxy used herein. It has been found that in the resin component of the composition, from about 12 to about 50 weight percent or more must consist of halogen to obtain the flame retardant benefits of the present invention. Preferably, when using bromine, the range is about 12 to about 19%. These amounts are conventional and well known amounts. The epoxy resins contemplated by the present invention are those produced from the reaction of at least one polyhydric phenol and at least one epihalohydrin in an alkaline medium. Phenols suitable for use include those containing at least two phenolic hydroxyl groups per molecule. Polynuclear phenols that have been found to be particularly suitable are those in which the phenol nuclei are linked by carbon bridges, e.g. 2,2-
Bis(4-hydroxyphenyl)propane (known as bisphenol-A), 4,4'-
Includes dihydroxydiphenylmethane, tetra-bis(hydroxyphenyl)ethane, and mixtures thereof. Although epichlorohydrin is commonly used as the epihalohydrin in making polymeric epoxides, analogs thereof such as epibromohydrin may be substituted. In preparing the highly halogenated epoxides of this invention, the desired epichlorohydrin is reacted with tetrachlorobisphenol-A or tetrabromobisphenol-A. In this reaction, the halogen content of the polymer is adjusted to yield the halogen content described above. By way of example, resinous polymeric epoxides (or glycidyl polyethers) suitable for use in accordance with the present invention may be prepared in the presence of at least 1 to 2 moles of alkali, based on the amount of halogen that can be substituted. It may be prepared by mixing and reacting a proportion of epihalohydrin, preferably epichlorohydrin, with about 1 molar proportion of tetrabromobisphenol-A. Polymeric epoxides can be made in solid or liquid form. Commercially available glycidyl polyethers (epoxides) that are solids are cheaper than their liquid counterparts, so the use of solid materials offers significant cost savings. However, in the present invention, the epoxy resin can be used in either solid or liquid form. In each case a solvent, such as toluene or one of the ketones, is present in an amount sufficient to form an impregnating varnish. Preferably the solvent comprises an alkylene glycol mono- or di-ester or ether, N-alkyl formamide, di(lower _C1 - _C6 ) alkyl ketone, or any mixture thereof. Specific such solvents include mixtures of ethylene glycol monomethyl ether, dimethyl formamide and acetone. Conventional hardeners can be used as component (b) in conventional amounts, for example acid anhydride hardeners such as the halogenated acid anhydrides or phthalic anhydrides or other polyanhydrides mentioned above are generally used as component (a) of the epoxy resin component (a). ) can be used in an amount of 20 to 30% by weight. On the other hand, amine type curing agents such as diethylenetriamine, triethanolamine, etc. can be used in an amount of 5 to 25% by weight. A preferred curing agent is dicyandiamide alone or in combination with a tertiary amine or tetraalkylguanidine catalyst. These are described in some of the aforementioned patent specifications, in particular US Pat. No. 3,391,113, the disclosures of which are hereby incorporated by reference. Generally, dicyandiamide is about 1 to about 20 parts by weight per 100 parts by weight of resin component (a).
Preferably, it is used in an amount of about 1 to about 5 parts by weight, and the tertiary amine or tetraalkylguanidine is used in an amount of about 0.01 to about 0.5 parts by weight per 100 parts by weight of epoxy resin component (a). Hydrated alumina is a reinforcing filler whose function is to help improve machinability. Although its exact nature is unknown, its action appears to be physical or chemical. The amount used is 10-40 based on the weight of (a) and (c)
%, preferably 25-30%. hydrated alumina
It is believed that _the bound water in _Al2O3.3H2O acts to form bonds between the epoxy resin secondary hydroxyl groups and the hydroxyl groups on _the glass toughener. Non-hydrated aluminum oxide is not effective in this invention. A preferred commercially available hydrated alumina is grade C-311 available from Aluminum Company of America. Obviously, the compositions according to the invention can contain additional conventional additives in conventional amounts. Chlorinated phenyls, aromatic phosphates, antimony trioxide, etc. can be used to minimize residual flame, improve dielectric properties, suppress flames, etc. In practicing the present invention, a selected glass fiber web (glass mat, glass paper, glass cloth, etc.) is passed through a varnish containing a resin/hydrated alumina impregnation agent. Any type of glass can be used, but those with the best electrical qualities are preferred and the glass is preferably pretreated with conventional coupling agents such as silane. The impregnating device can be of any type, such as a two-zone dip-squeeze type processor. Typical processing conditions are approximately
Includes a 0.010 inch squeeze roll set, a wet zone temperature of about 100°C for 2 minutes, a dry zone temperature of about 160°C for about 4 minutes (web speed of about 100-200 inches). Resin varnishes are usually about 50-70% resin and filler solids and 50-30% solvent. These conditions typically result in about 40 to about 70 weight percent resin composition in the processed glass web. The impregnated B-stage and dried prepreg is cut to desired size and then stacked to obtain the desired thickness. Particularly intended for multilayer structures, metal foils such as aluminum, copper, etc. can be applied to either or both sides with or without conventional adhesives before consolidation. When consolidating prepreg stacks,
Pressures from about 200 to 2000 psi and from about 130 to
Use a temperature of 185°C. Press cycles can vary from a few minutes to about 75 minutes depending on the number of stacks to be compacted in each press opening and the thickness of the laminate. The stacked sheets are placed in a cold press,
Consolidate under the compression conditions described above, take out and ca.
Cool to 150㎓. The present invention will be explained below with reference to Examples. It is to be understood that each example is given by way of example only. Example 1 A resin varnish having the following composition was applied to a silanized woven glass fabric in a four-zone vertical processor. After drying, the prepreg contained approximately 60% by weight impregnating agent. The prepreg was cut and six sheets were stacked to form a stack. Copper foil was placed on the outside of each stack. Eight stacks were consolidated within each press opening. The compression conditions were a pressure of 1000 pai, a temperature of 175°C, and a compression cycle of 50 minutes. Standard FR-4 laminates containing no hydrated alumina were made, but seven prepreg sheets were used in each stack. Each laminate was tested for physical properties, electrical properties and flammability. The compositions used and the results obtained are shown in Table 1.

【table】

Table: When drilled, it showed substantially less drill wear than the 7 layer control (1A). The quality of the holes made in laminate (1) was much better than the quality of the holes made in (1A). Another resin varnish was made with a different type of additive, and the same improvements were obtained. For example, non-halogenated epoxy resins could be eliminated. For example, instead of epichlorohydrin-bisphenol-A resin, a polyglycidyl ether of tetraphenylethane or an epoxylated novolak could be used. Tetramethylguanidine could be used instead of benzyldimethylamine. Instead of glass cloth, glass mat or glass paper could be used. Hydrated alumina 10, 15, 20, 25, 35 and 40 instead of 30% by weight hydrated alumina (epoxy basis)
% could be used. Those skilled in the art will appreciate that the above description is illustrative of a family of flame retardant electrical quality glass-based laminates that have greatly improved machinability and other properties over prior art laminates. Its manufacturing method is simple and can be carried out with conventional equipment. The new family of laminates represents a distinct improvement over conventional glass-based electrical quality laminates and provides those skilled in the art with the means to create fire-resistant, easily processable printed circuit substrates. ing.

Claims (1)

Claims: 1. (a) a flame retardant amount of a chlorinated or brominated epoxy resin; (b) an effective amount of (i) a curing agent for (a), or (ii) in combination with a curing catalyst ( a curing agent for a); and (c) a glass fiber sheet impregnated with a B-stage epoxy resin composition containing from about 10 to about 40% hydrated alumina, based on the weight of (a) and (c). product. 2. The product according to claim 1, wherein the glass fiber sheet is made of glass cloth. 3. The article of claim 1, wherein the epoxy resin composition contains not more than about the same amount, by weight, of (a) non-chlorinated or non-brominated epoxy resin. 4. The product of claim 1, wherein component (a) comprises a bifunctional reaction product of tetrabromobisphenol-A and epichlorohydrin. 5 Component (a) is a bifunctional reaction product of bisphenol-A and epichlorohydrin, a tetrafunctional reaction product of tetra-bis(hydroxyphenyl)ethane and epichlorohydrin, or a mixture thereof. A product according to claim 1 containing a difunctional reaction product of tetrabromobisphenol-A and epichlorohydrin in combination. 6. The product according to claim 1, wherein component (b)(i) contains dicyandiamide. 7. The article of claim 6, wherein component (b)(i) comprises from about 1 to about 5 parts by weight per 100 parts by weight of epoxy resin component (a). 8. The product of claim 1, wherein component (b)(ii) contains dicyandiamide in combination with a tertiary amine or a tetraalkylguanidine curing catalyst. 9 In component (b)(ii), epoxy resin component (a) 100
9. The article of claim 8 containing from about 1 to about 5 parts by weight of dicyandiamide and from about 0.1 to about 0.5 parts by weight of tertiary amine or tetraalkylguanidine. 10. The article of claim 1, wherein said hydrated alumina component (c) is present in an amount of about 10 to about 40% by weight based on the weight of (a) and (b). 11 An insulating substrate for a flame retardant printed circuit board comprising a plurality of epoxy resin composition impregnated glass fiber sheets united into an integral structure under heat and pressure, the epoxy resin composition comprising (a ) a flame retardant amount of a chlorinated or brominated epoxy resin; (b) an effective amount of (i) a curing agent for (a) alone, or (ii)
A curing agent for (a) in combination with a curing catalyst; and (c) an insulating substrate containing from about 10 to about 40% hydrated alumina, based on the weight of (a) and (c). 12. The insulating base material according to claim 11, comprising a gold layer foil laminated on one or both surfaces of the insulating base material. 13 Claim 12, wherein the metal is copper
The insulating base material described in . 14. The insulating base material according to claim 11, wherein the glass fiber sheet is made of glass cloth. 15. Claim 11, wherein the epoxy resin composition includes (a) approximately the same weight or less of non-chlorinated or non-brominated epoxy resin based on the weight of (a) alone.
The insulating base material described in . 16 Component (a) is tetrabromobisphenol-A
The insulating substrate according to claim 11, which contains a bifunctional reaction product of epichlorohydrin and epichlorohydrin. 17 Component (a) is a bifunctional reaction product of bisphenol-A and epichlorohydrin, a tetrafunctional reaction product of tetra-bis(hydroxyphenyl)ethane and epichlorohydrin, or a mixture thereof. 12. The insulating substrate of claim 11 containing a difunctional reaction product of tetrabromobisphenol-A and epichlorohydrin in combination. 18. The insulating substrate according to claim 11, wherein component (b)(i) contains dicyandiamide. 19. The insulating substrate according to claim 18, wherein component (b)(i) comprises about 1 to about 5 parts by weight based on 100 parts by weight of epoxy resin component (a). 20. The insulating substrate of claim 11, wherein component (b)(ii) contains dicyandiamide in combination with a tertiary amine or a tetraalkylguanidine curing catalyst. 21 In component (b)(ii), epoxy resin component (a)
per 100 parts by weight of dicyandiamide, about 1 to 1
21. The insulating substrate of claim 20, comprising about 5 parts by weight and about 0.1 to about 0.5 parts by weight of the tertiary amine or tetraalkylguanidine. 22. The insulating substrate of claim 11, wherein the hydrated alumina component (c) is present in an amount of about 10 to about 40% by weight based on parts by weight of (a) and (c). .