JPH01152138A - Production of laminate for printed circuit - Google Patents

Abstract

PURPOSE:To obtain a laminate for printed circuits, improved in high-frequency characteristics, reliability and processability, by using woven glass cloths impregnated with a varnish based on an epoxy resin having a specified composition as surface layers and a nonwoven glass cloth impregnated with a varnish formed by adding aluminum hydroxide to said varnish as an intermediate layer and molding these layers under applied heat and pressure. CONSTITUTION:This laminate for printed circuits is prepared by the following process. Namely, woven glass cloths impregnated with a varnish formed by using an epoxy resin component based on a bisphenol A epoxy resin having an epoxy equivalent of 700-1,200 and a novolac epoxy resin and an aromatic diamine as a curing agent are used as surface layers, while a nonwoven glass cloth impregnated with a varnish formed by adding aluminum hydroxide as an inorganic filler to a varnish based on said resins is used as an intermediate layer. These surface and intermediate layers are molded under applied heat and pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing 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, there are many laminates (hereinafter referred to as composite laminates) that are impregnated with epoxy resin and heated and pressed, with a structure in which a nonwoven glass fabric is used as an intermediate layer base material and a woven glass fabric is used as a surface layer base material. became the most used. The laminate, which is made by impregnating only the glass woven fabric base material with epoxy resin, has excellent mechanical strength, dimensional stability, moisture resistance, and heat resistance, and is highly reliable for through-hole plating, so it can be used in electronic computers, communication equipment, electronic exchange equipment, etc. It is widely used in industrial electronic equipment.

However, since only glass woven fabric is used as the base material, it is impossible to use a punching method 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 glass woven fabric base epoxy resin plate has a weight ratio of about 40:60 between the organic epoxy resin and the inorganic glass woven fabric. 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, that is, woven glass fabric and glass nonwoven fabric, is smaller than that in woven glass fabric laminates.

The ratio of organic matter to inorganic matter is about 60:40, which is the opposite of that of lath woven laminated sandalwood, so it was thought that the dimensional stability and reliability of through-hole plating were low.

The present inventors have studied 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, they have achieved We have obtained a new composite laminate with characteristics that cannot be obtained previously. (Patent application 1151/1982)
No. 18). Alumina hydrate (so-called aluminum hydroxide) used as this inorganic filler contains gibbsite (α-type trihydrate A12o3・3day20) as a crystalline hydrate.
, bayerite (β-type trihydrate), nordstrandite, boehmite (α-type monohydrate Al2O3・H2O),
Diasboa (β-type monohydrate), Todite (5A12
03.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 temperatures during the printed circuit and assembly process, for example during the soldering process, where they are typically immersed in a 260°C solder bath, so composite laminates using gibbsite as a filler may swell over extended immersion times. Defects occur due to

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. 59-59501). .

However, in recent years, advances in processing technology for laminated boards, higher density circuits,
With the diversification of applications, even higher reliability and high frequency characteristics are now required.

(Objective 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) The present invention provides a varnish in which the surface layer is mainly composed of a bisphenol A epoxy resin and a novolak epoxy resin having an epoxy equivalent of 700 to 1200 as an epoxy resin component, and an aromatic diamine curing agent is 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.The surface layer and the intermediate layer are heated. This is a method for manufacturing a printed circuit laminate, which is characterized by pressure molding.

The bisphenol A type epoxy resin used in the present invention has an epoxy weight of 1700 to 1200.

Laminated boards made using low-molecular 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, and the mechanical and thermal shocks during processing described above will be absorbed as molecular movement, and the laminate will be Destruction is less likely to occur. On the other hand, as the molecular weight of bisphenol A 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 that reduce adhesive strength. Lower it.

Therefore, the decrease in crosslinking density due to increase in molecular weight can be suppressed by using a novolac type epoxy resin in combination. When this novolak type epoxy resin is used in combination, a bisphenol A type epoxy resin having an epoxy Wi of 1200 or less can be used. If an epoxy resin with a higher molecular weight than this is used, even if a novolac 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 15 to 30%.
(Mold set %, same below) is preferable.

In the present invention, it is preferable to use a bisphenol A novolac type epoxy resin as the novolac type epoxy resin. The use of bisphenol A novolac type epoxy resin increases flexibility and reduces distortion during curing compared to the use of ordinary phenol or talesol novolac type epoxy resins.
The moldability is good, and the obtained 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 blending ratio with bisphenol A type epoxy resin is not particularly limited, but bisphenol A type epoxy resin 6
It is preferable to use 40 to 10 parts of bisphenol A novolak type epoxy resin per 0 to 90 parts (mold recess, same hereinafter).

In the present invention, even if a part of the bisphenol A type epoxy resin having an epoxy equivalent of 1,700 to 1,200 is replaced with an epoxy compound having a lower epoxy equivalent than this, it still maintains the high-rise properties, heat resistance, and thermal shock resistance that are the objectives of the present invention. This case is also included in the present invention since an effective improvement is observed in terms of properties and dimensional stability.

It is desirable that the aromatic diamine curing agent used in the present invention is contained in an amount of 0.3 to 0.7 equivalents of the epoxy resin. If it exceeds or falls below this range, the heat resistance and moldability will deteriorate, making it undesirable in terms of practicality. Type of curing accelerator and ω
The varnish used in the present invention can obtain an appropriate gel time with 1
20 to 240 seconds/170°C is preferable in terms of moldability.

The aluminum hydroxide used in the present invention is preferably 10 to 200%, particularly preferably 2% to the resin of the intermediate layer.
Contains 0-200%.

If it is less than 10%, the effect of improving heat resistance will be small, and if it is more than 200%, 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 preferably 80 to 200%. If it is less than 80%, the dimensional stability and the reliability of through-hole plating deteriorate, 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.

〔Effect of the invention〕

The printed circuit laminate of the present invention has the following features.

(1) High frequency characteristics and moisture absorption drift properties are significantly improved compared to laminates using conventional aromatic diamine curing agents.

(2) Improved glass transition temperature improves thermal shock resistance and significantly improves reliability.

〔Example〕

Examples of the present invention and comparative examples (conventional examples) are shown.

The composition of the epoxy resin-containing varnish is as follows.

Next, the varnish blended for the surface layer was applied to a glass woven fabric (Nittobo WE-18-RB84) with a resin content of 42 to
It was impregnated and dried to a concentration of 45% to obtain a glass woven prepreg. Subsequently, an inorganic filler of 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 prepare an inorganic filler-containing varnish.

Silica (Tatsumori Crystallite VX-3>25 parts Gibbsite type aluminum hydroxide (A1203/2.4H20) 70 parts Ultrafine powder silica (Giotsugi Pharmaceutical Carplex)
5 parts of this inorganic filler-containing varnish was applied to a glass nonwoven fabric (Ep-407 manufactured by Nippon Vilene Co., Ltd.).
5) was impregnated and dried so that the content of resin and inorganic filler was 90% to obtain a glass nonwoven fabric prepreg.

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 the body tube is further stacked on top of the glass nonwoven fabric prepreg, and the molding temperature is 165°C and the pressure is 60 kg/kg.
Lamination molding was carried out for 90 minutes using CRI to obtain a copper-clad laminate having a thickness of 1.6 m.

[Comparative example (conventional example)]

The composition of the epoxy resin-containing varnish for the surface layer and intermediate layer is brominated epoxy resin 2 ethyl 4 methyl imidazole 0.15 methyl cellosolve 36 acetone
A copper-clad laminate was obtained in the same manner as in the example except that the thickness was 60.

Table 2 shows the comparison results of each characteristic in the above Examples and Comparative Examples.

Measurement method: Solder heat resistance, bending strength when heated = according to JISC6481. The temperature at the peak value of tan δ is determined by the glass transition humidity-viscoelasticity method.

Dielectric constant, dielectric loss tangent = according to JISC6481.

Moisture drift resistance = Moisture absorption treatment is performed using a test piece with comb-shaped electrodes (interval 0.5 opposing length 160AI11) printed and wired on one surface of the table (C-240/60/90). Frequency 1).

In addition, other film characteristic 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] Epoxy equivalent as epoxy resin component 700-1200
The surface layer is a glass woven fabric impregnated with a varnish containing bisphenol A type epoxy resin and novolac type epoxy resin as the main components, and an aromatic diamine curing agent added as a curing agent. A method for manufacturing a laminate for printed circuits, characterized in that a glass nonwoven fabric impregnated with a varnish containing aluminum hydroxide as a filler is used as an intermediate layer, and the surface layer and the intermediate layer are formed under heat and pressure.