JPS63265632A - Manufacture of laminated sheet - Google Patents

Abstract

PURPOSE:To constitute the title laminated sheet so that the same turns superior in heat resis tance to solder and surface smoothness and an interlaminar prepreg can be managed with a single sheet of the same, by a method wherein a thickness of a base material of the prepreg is made thinner than a desired thickness between conductor layers by a specific thickness. CONSTITUTION:Lamination is performed in order of a copper foil 1, a prepreg 2, an inner layer circuit board 3, the prepreg 2 and the copper foil 1. Now the prepreg 2 is obtained by impregnating a base material with resin and performing solidification or semi-cure of the same. Insulation between conductor layers is assured by making a thickness of the prepreg 2 0.2mm or thicker. When the base material is impregnated with the resin by making the base material thinner at least by 5mum then a desired thickness between the conductor layers, a difference between the desired thickness and a thickness of the base material is filled with the resin and along with adhesion between the base material and conductor layer, the surface of the base material is flattened. A fibrous material is used for the base material and either of thermoplastic resin or thermosetting resin may be good for impregnating resin. With this construction, heat resistance to solder is improved and surface roughness can be made 4mum or finer. Then in the case where the conductor layer constitutes a circuit, insulation between conductor layers becomes reliable by filling out an air space between circuits also.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a method for manufacturing a laminate.

[Background technology]

Laminated boards for printed boards are currently used in many OAIl devices, and there has been a shift to multilayer boards for higher density.

Currently, in order to obtain interlayer thicknesses (intervals between conductor layers) in steps of 0.20 Wm, a plurality of prepregs each having a thickness of 0.10 m are combined. For this reason, the problem arises that the number of required prepregs increases and the cost increases. There is an urgent need to reduce the amount of materials used.

However, even if this problem can be solved, it is undesirable to have other inconveniences.For example, when mounting electronic components on a laminate, the laminate is floated or immersed in a solder bath, so it is not desirable to solder the laminate. It is necessary to prevent heat resistance from deteriorating. Furthermore, in order to achieve higher density, it is necessary to make the circuit pattern finer. To meet this requirement, it is necessary that the surface roughness of the laminate be excellent.

[Purpose of the invention]

In view of the above, an object of the present invention is to provide a method for manufacturing a laminate that can inexpensively produce a laminate with excellent solder heat resistance and surface smoothness.

[Disclosure of the invention]

In order to reduce the amount of material used, the inventors did not combine multiple sheets of thin prepreg (0.10 m thick) as in the past, but instead created a material with a desired glabellar thickness (for example, 0.20 m thick).
We proceeded with our research with the idea that we should use a prepreg that satisfies the above requirements with just one sheet.

However, when producing a laminate, especially a multilayer board, using a prepreg thicker than conventional prepreg, two problems arose: (1) poor solder heat resistance, and (2) poor surface roughness.

The practical problem caused by the above item (2) is that when electronic components are soldered onto the laminate, peeling occurs between the eyebrows of the laminate. Since the base material of thick prepreg is also thick, impregnation of the resin into the base material becomes poor. When such thick prepreg is used in a multilayer board, the base material of the prepreg comes into direct contact with the inner layer circuit and its substrate after molding, and the resin necessary for adhesion may not exist between the two. . For this reason, solder bath (
It cannot withstand a thermal shock at a temperature of, for example, 260° C., resulting in peeling between the eyebrows. Furthermore, since the resin is not sufficiently impregnated into the base material, air may remain in the base material, and when this air expands thermally, it causes blisters.

The practical problem with (2) above is that unless the surface roughness is 4 μm or less, a fine pattern cannot be produced, and it becomes impossible to produce a high-density pattern required for a multilayer board. In order to increase the thickness of the base material, thick threads must be woven, which increases the unevenness of the base material surface. In addition, if a base material of that thickness (for example, 0.20 m1m) is used to obtain the desired glabellar thickness (for example, 0.20 m), there will be only a corresponding amount of resin, and the unevenness of the base material becomes more likely to appear on the surface.

As a result of research aimed at solving these two problems, we found that by using a base material that is at least 5 μm thinner than the required glabellar thickness and impregnating it with the amount of resin necessary for the desired interlayer thickness, it is possible to achieve solder heat resistance with conventional thin prepreg. It has been found that the material has excellent properties of hardness and surface smoothness.

Therefore, the present invention provides a method for manufacturing a laminate in which a prepreg for forming an insulating layer that also serves as an adhesive layer is interposed between conductor layers and laminated. The gist of the present invention is a method for manufacturing a laminate, characterized in that the thickness is 5 μm or more thinner than the desired thickness between the conductor layers.

The present invention will be explained in detail below.

A prepreg for forming an insulating layer that also serves as an adhesive layer is obtained by impregnating a base material with a resin and solidifying or semi-curing the prepreg. It is desirable that the prepreg has a total thickness of 0.2 mm or more, because if the prepreg is thinner than 0.2 mm, it becomes difficult to guarantee the insulation between the conductor layers.

The base material used is one that is 5 μm or more thinner than the desired thickness between the conductor layers.

When such a base material is impregnated with a resin so that the resin content is the same as that of a conventional prepreg, the resin layer on the surface becomes thicker as the base material is thinner. This resin layer fills the difference between the desired thickness and the thickness of the base material, adheres the base material and the conductor layer, and flattens the unevenness on the surface of the base material. The resin layer is preferably formed with a uniform thickness on both sides of the base material, but the thickness does not have to be uniform on both sides, as long as the thickness of the base material is not less than 5 μm thinner than the desired thickness. In some cases, the resin layer attached to the surface of the base material is so thin that the resin necessary for adhesion is not present, and the surface roughness becomes poor. If the desired thickness between the conductor layers is, for example, 0.
In the case of 20 m, the thickness of the base material is 0.195 m or less. In this case, the thickness of the base material is 0.18 to 0.1951
) m range is preferred.

Further, when the desired thickness between the conductor layers is 0.25 fin, the thickness of the base material is 0.245 °C m or less,
If the desired thickness between the conductor layers is 0.39 am, then the thickness of the substrate is less than or equal to 0.2951)n.

The base material used is fibrous. The fibrous base material is not particularly limited, but examples thereof include glass cloth, paper, synthetic fiber cloth, and natural fiber cloth. The cloth may be woven or non-woven. The resin impregnated into the fibrous base material is not particularly limited, and may be either a thermoplastic resin or a thermosetting resin. Further, the resin to be impregnated may contain one or more other substances, such as a crosslinkable substance, a curing agent, a curing accelerator, and a filler, as necessary. The thermoplastic resin is not particularly limited, and examples thereof include polyphenylene oxide, fluororesin, and the like. The thermosetting resin is not particularly limited, and examples thereof include epoxy resin, fluororesin, polyimide resin, and the like.

The conductor layer may be a metal foil such as a copper foil, a circuit formed on an insulating substrate (so-called inner layer material), but is not limited to these.

The prepreg used in this invention uses a base material that is 5 μm or more thinner than the desired interlayer thickness, so after molding, the resin layer is reliably applied to the difference between the interlayer thickness and the base material thickness. is formed. Therefore, the resin is reliably interposed between the base material and the conductor layer or the substrate of the conductor layer (inner layer material, outer layer material, etc.), which improves soldering heat resistance and improves surface roughness. The thickness can also be reduced to 4 μm or less. Also, if the conductor layer is a circuit,
It can also fill gaps between circuits. If a prepreg with a total thickness of 0.2 W or more is used, the insulation between the conductor layers will be ensured.In addition, in conventional molding using prepreg, it is necessary to squeeze out the resin in the prepreg, making the molding process difficult. The pressure was high, for example, about 40 kg/cd. For this reason, the conductor layer, especially the circuit, has been displaced by the molding pressure. However, in the manufacturing method according to the present invention, since the above-mentioned prepreg is used, the extent of squeezing out the resin is small, and the molding pressure is low (for example,
(approximately 1/4 of 1.10 kg/-). Therefore, according to the manufacturing method according to the present invention, it is possible to prevent circuit misalignment, and even fine patterns can be handled. In particular, when the laminate is made into a multilayer board, the accuracy can be improved.

EXAMPLES Hereinafter, this invention will be explained in more detail with reference to Examples and Comparative Examples, but this invention is not limited to the following Examples.

(Examples 1 to 4) Glass cloths having the thicknesses shown in Table 1 were impregnated with resin to produce prepregs as shown in Table 1. Using this prepreg, as shown in FIG. 1, copper foil 1, prepreg 2, inner layer circuit board 3, prepreg 2, and copper foil 1 are laminated in this order, and molded under the following molding conditions, each with an interlayer thickness of 0. Laminated plates of 2n type, 0.25 mm type, and 0.3 m type were obtained. The inner layer circuit board 3 consisted of an insulating substrate 4 with a thickness of 1.0 fi and inner layer circuits (conductor layers) 5.5 with a thickness of 70 μm formed on both sides of the insulating substrate 4. This inner layer circuit 5 has a thickness of 70
A thin layer of .mu.m metal was etched to form a grid-like shield pattern.

Molding conditions> Temperature: 120°C for 30 minutes, then 170°C for 70 minutes.

Pressure: 4kg/cnl for 10 minutes, then 40kg/cnl
until the end with al.

(Comparative Examples 1 to 3) Glass cloths having the thicknesses shown in Table 1 were impregnated with resin to produce prepregs as shown in Table 1. In the same manner as in Example 1 except that this prepreg was used instead of prepreg 2 in Example 1, the interlayer thickness was 0.2.
Laminated plates of tm type, 0.25m type, and 0.3m type were obtained.

The measurement results of the characteristics of each laminate obtained in Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 1. The thickness of the glass cloth was measured according to JIS-R-3420. Furthermore, the solder heat resistance was evaluated by immersing it in solder at 260° C. for 20 seconds and evaluating the presence (x) and absence (OK) of blistering or peeling.

As is clear from Table 1, the examples are superior in heat resistance and surface smoothness to the comparative examples in all of the 0.2 fi type, 0.25 m type, and 0.3 m interlayer thickness types.

In the above example, the molding pressure was the same as that of the comparative example, but according to the method for manufacturing a laminate according to the present invention, molding can be performed at a much lower molding pressure than conventionally. For example, it can be molded at a molding pressure of about 1/4.10 kg/i.

〔Effect of the invention〕

As described above, the method for producing a laminate according to the present invention uses a prepreg whose base material is 5 μm or more thinner than the desired thickness between the conductor layers, so that it has good soldering heat resistance. It is possible to obtain a laminate with excellent surface smoothness, and since only one prepreg is required between the eyebrows, the number of required prepregs can be reduced.
It can be constructed at low cost.

[Brief explanation of drawings]

FIG. 1 is an exploded side view of the structure of the laminate. 2...Prepreg

Claims (2)

[Claims] (1) In a method for manufacturing a laminate in which a prepreg for forming an insulating layer that also serves as an adhesive layer is interposed between conductive layers and laminated molding is performed, the thickness of the base material of the prepreg is 5 than the desired thickness between the conductor layers
A method for manufacturing a laminate, characterized by using a material thinner than μm. (2) The method for manufacturing a laminate according to claim 1, wherein the entire thickness of the prepreg is 0.2 mm or more.