JPH0360862B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a printed circuit laminate having excellent high frequency characteristics, workability, and reliability of through-hole plating. [Prior art] As a copper-clad laminate for printed circuits, a laminate (hereinafter referred to as a composite laminate) is impregnated with epoxy resin and heated and pressurized with a structure in which a nonwoven glass fabric is used as an intermediate layer base material and a glass woven fabric is used as a surface layer base material. ) has come to be used extensively. The laminate, which is made by impregnating only the woven glass fabric base material with epoxy resin, has excellent mechanical strength and
It has excellent dimensional stability, moisture resistance, heat resistance, and high reliability for through-hole plating, so it is widely used in industrial electronic equipment such as computers, communications equipment, and electronic exchanges. However, since only glass woven fabric is used as the base material, punching is not possible in the drilling process, which is one of the processing steps for printed circuit boards, and the reality is that drilling is required. On the other hand, composite laminates are economically cheaper than woven glass fabric laminates and have the advantage of being able to be punched and punched, and have attracted attention as glass-based laminates with good workability. The reliability of through-hole plating was evaluated to be lower than that of glass woven fabric base laminates. The reason for this is that the structure of the glass woven fabric base epoxy laminate plate has a weight ratio of about 40:60 between the epoxy resin, which is an organic substance, and the glass woven fabric, which is an inorganic substance. In this case, it is thought that the epoxy resin mainly provides excellent electrical performance, and the glass woven fabric provides excellent mechanical performance such as bending strength and dimensional stability. By the way, in general composite laminates, the total amount of inorganic base materials that contribute to mechanical performance, ie, glass woven fabric and glass nonwoven fabric, is smaller than that in glass woven fabric laminates. The ratio of organic matter to inorganic matter is approximately 60:40, which is the opposite of that of glass woven laminates, so it was thought that dimensional stability and reliability of through-hole plating were low. The present inventors have studied how to improve these drawbacks while taking advantage of the excellent characteristics of composite laminates, and by adding a large amount of inorganic filler to the composition of general composite laminates, we have created a composite laminate that is of a single composition. We have obtained a new composite laminate with characteristics that cannot be obtained previously. (Special Application No. 115118/1982). The alumina hydrate (so-called aluminum hydroxide) used as this inorganic filler contains gibbsite (α-type trihydrate Al ₂ O ₃ 3H ₂ O) and bayerite (β-type trihydrate) as crystalline hydrates. ), nordstrandite, boehmite (α-type monohydrate Al ₂ O ₃・H ₂ O), diaspore (β-type monohydrate), toadite (5Al ₂ O ₃・
_H2O ) is known. Gibbsite-type aluminum hydroxide (hereinafter referred to as gibbsite) releases water in the range of 200°C to 500°C. Since the amount of heat absorbed at this time is large, it is used as a filler in general synthetic resins to maintain flame retardancy. However, laminates are frequently exposed to high heat conditions during printed circuit and assembly processes, such as soldering processes, which typically
Since it is immersed in a solder bath at 260°C, composite laminates using gibbsite as a filler will suffer from blistering if the immersion time is too long. The cause of this is the release of water from the gibbsite. In order to overcome this drawback, the present inventors have obtained a laminate with significantly improved soldering heat resistance by filling the resin for composite laminates with heat-treated gibbsite (Japanese Patent Application No. 59501/1982). . However, in recent years, advances in processing technology for laminated plates, higher circuit densities, and diversification of applications have led to demands for even higher reliability and high-frequency characteristics. [Object of the Invention] An object of the present invention is to provide a printed circuit laminate that has excellent high frequency characteristics that cannot be obtained with conventional composite laminates, has high reliability, and has good workability. [Structure of the Invention] In the present invention, the surface layer contains bisphenol A having an epoxy equivalent of 700 to 1200 as an epoxy resin component.
It consists of a glass woven fabric impregnated with a varnish containing type epoxy resin and novolac type epoxy resin as the main components, and an aromatic diamine curing agent added as a curing agent.
The intermediate layer is made of a glass nonwoven fabric impregnated with a varnish mainly composed of the epoxy resin and containing aluminum hydroxide as an inorganic filler, and the surface layer and the intermediate layer are molded under heat and pressure. This is a method for manufacturing a laminate for printed circuits. The bisphenol A type epoxy resin used in the present invention has an epoxy equivalent of 700 to 1,200. Laminated plates using low molecular weight epoxy resins are unable to absorb mechanical and thermal shocks during the processing process, often leading to breakage. If the molecular weight of the epoxy resin used is increased and an epoxy equivalent of 700 or more is used, the molecular weight between the crosslinking points will be larger than before, which will absorb the mechanical and thermal shock during processing as molecular movement, and the laminate will be Destruction is less likely to occur. On the other hand, when the molecular weight of bisphenol A type epoxy resin is increased, the viscosity does not decrease even when heated during pressure molding, and the resin is difficult to penetrate into the interface with glass fibers and metal foil, leaving bubbles to strengthen the bond. lower. Therefore, the decrease in crosslinking density due to increase in molecular weight can be suppressed by using a novolak type epoxy resin in combination. When this novolac type epoxy resin is used in combination, a bisphenol A type epoxy resin having an epoxy equivalent of 1200 or less can be used. If an epoxy resin with a higher molecular weight than this is used, even if a novolak type epoxy resin is used in combination, it will not be possible to obtain a material that has practical properties such as solvent resistance. In the present invention, a brominated bisphenol epoxy resin is usually used, and the bromine content is preferably 15 to 30% (weight %, the same hereinafter). In the present invention, it is preferable to use a bisphenol A novolak type epoxy resin as the novolak type epoxy resin. The use of bisphenol A novolac type epoxy resins provides increased flexibility and less distortion during curing compared to the use of regular phenol or cresol novolac type epoxy resins, making molding easier. The resulting laminate has excellent properties such as high frequency properties, heat resistance, thermal shock resistance, and solvent resistance. The bisphenol A novolac type epoxy resin preferably has a molecular weight of 450 to 1,400 from the viewpoint of the above characteristics. In addition, the ratio of blending with bisphenol A type epoxy resin is not particularly limited, but bisphenol A
Bisphenol A novolak type epoxy resin for 60 to 90 parts (parts by weight, same below) of type epoxy resin
40 to 10 parts is preferred. In the present invention, even if a part of the bisphenol A type epoxy resin having an epoxy equivalent of 700 to 1200 is replaced with an epoxy compound having a lower epoxy equivalent, the high frequency properties, heat resistance, thermal shock resistance, and Since a useful improvement in dimensional stability is observed, this case is also included in the invention. The aromatic diamine curing agent used in the present invention is preferably contained in an amount of 0.3 to 0.7 equivalents of the epoxy resin. If it is above or below this range, the heat resistance and moldability will deteriorate, which is undesirable from the practical point of view. An appropriate gel time can be obtained depending on the type and amount of the curing accelerator, and the varnish used in the present invention preferably has a gel time of 120 to 240 seconds/170°C for moldability. The content of aluminum hydroxide used in the present invention is preferably 10 to 200%, particularly preferably 20 to 200%, based on the resin of the intermediate layer. Below 10%, the effect of improving heat resistance is small;
% or more, the resin viscosity when mixed with gibbsite becomes too high, making it difficult to impregnate the glass nonwoven fabric base material. When the content is 20% or more, the effect of improving heat resistance becomes more reliable. Inorganic fillers other than aluminum hydroxide (eg silica) can also be used in the intermediate layer. The ratio of the entire inorganic filler to the intermediate layer resin is
80-200% is preferred. If it is less than 80%, the dimensional stability and reliability of through-hole plating decreases, which is not preferable. If it is 200% or more, the viscosity becomes too high when the inorganic filler is mixed with the resin, making it difficult to impregnate the glass nonwoven fabric. [Effects of the Invention] The printed circuit laminate of the present invention has the following features. (1) Compared to laminates using conventional aromatic diamine curing agents, high frequency characteristics and moisture absorption drift properties are significantly improved. (2) Improved glass transition temperature improves thermal shock resistance and significantly improves reliability. [Example] Examples of the present invention and comparative examples (conventional examples) will be shown.
The composition of the epoxy resin-containing varnish is as follows.

[Table] A uniform varnish was prepared by mixing the above materials.
Next, the varnish blended for the surface layer was impregnated into a glass woven fabric (WE-18K-RB84 manufactured by Nittobo Co., Ltd.) to a resin content of 42 to 45% and dried to obtain a glass woven fabric prepreg. Subsequently, an inorganic filler in the following formulation was added to 100 parts of resin to a varnish similarly formulated for the intermediate layer, and the mixture was stirred and mixed to produce an inorganic filler-containing varnish. Silica (Tatsumori Crystallite VX-3) 25 parts Gibbsite type aluminum hydroxide (Al ₂ O ₃
2.4H ₂ O) 70 parts ultrafine powder silica (Carplex, manufactured by Shionogi Pharmaceuticals) 5 parts This inorganic filler-containing varnish is applied to glass nonwoven fabric (Ep-4075, manufactured by Nippon Vilene) so that the content of resin and inorganic filler is 90%. Impregnated and dried,
A glass nonwoven fabric prepreg was obtained. Next, the glass nonwoven fabric prepreg is used as an intermediate layer, the glass woven fabric prepreg is placed on the upper and lower surface layers, and a copper foil is layered on top of that, and the molding temperature is
Lamination molding was carried out for 90 minutes at 165° C. and a pressure of 60 kg/cm ² to obtain a copper-clad laminate with a thickness of 1.6 mm. [Comparative example (conventional example)] The composition of the epoxy resin-containing varnish for the surface layer and intermediate layer was a brominated epoxy resin (Ep-1046 manufactured by Yuka Ciel)
A copper-clad laminate was obtained in the same manner as in the example except that the following ingredients were used: 100 parts dicyandiamide 4 2 ethyl 4 methylimidazole 0.15 methyl cellosolve 36 acetone 60. Table 2 shows the comparison results of each characteristic in the above Examples and Comparative Examples.

[Table] Measurement method Soldering heat resistance, bending strength when heated = according to JIS C 6481. Glass transition temperature = Find the temperature of the peak value of tan δ using the viscoelastic method. Dielectric constant, dielectric loss tangent = according to JIS C 6481. Moisture drift resistance = Moisture absorption treatment is performed using a test piece with comb-shaped electrodes (interval 0.5 opposite length 160mm) printed and wired on the surface (C-240/60/90) to determine capacitance change due to moisture absorption treatment (frequency 1MHz) . In addition, other general property items were also measured, but no differences were found between the examples and comparative examples. As described above, it has been found that the printed circuit laminate of the present invention is an excellent laminate that maintains the characteristics of a composite laminate and has significantly improved high frequency characteristics.

Claims (1)

[Claims] 1 Epoxy equivalent as epoxy resin component 700~
A varnish whose surface layer is a glass woven cloth impregnated with a varnish containing a bisphenol A type epoxy resin and a novolac type epoxy resin having a hardening agent of 1200 and an aromatic diamine hardening agent added thereto as a hardening agent, and a varnish whose main component is the above-mentioned resin. A method for manufacturing a laminate for printed circuits, characterized in that the intermediate layer is a glass nonwoven fabric impregnated with a varnish containing aluminum hydroxide as an inorganic filler, and the surface layer and the intermediate layer are heated and press-molded.