JPH03153318A - Manufacture of laminated board - Google Patents

Abstract

PURPOSE:To prevent generation of a void due to an insufficient outflow of resin by fixing a board thickness by preventing an excessive outflow of the precured resin, by a method wherein the precure of impregnated resin of both side edge parts of a laminated body with preheating is advanced more than that of the other part. CONSTITUTION:A resin-impregnated base is manufactured as a continued long-sized matter, a plurality of sheets of which are piled upon one another, resin is regulated into a fixed resin content at need and then a metallic foil or a cover film and one side or both the sides of the base are stuck together. Although this laminated body 6 is preheated and the impregnated resin is precured, for example, a heating part corresponding to an axial direction of the laminated body 6 is divided into at least three heating zones as this preheating furnace, temperature of the respective heating zones can be controlled individually and both the end heating zones are set up at a higher temperature than that of the central heating zone. Then an extent of precure of both side fringe parts of widthwise direction of the laminated body 6 is advanced more than that of the other part. The preheated laminated body 6 finally cured by a continuous heating and pressurizing machine such as a double belt press, becomes a laminated plate and post-cured at need.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved method of manufacturing a laminated board suitable for printed circuit boards used particularly in electrical and electronic equipment.

[Conventional technology]

Laminated boards are widely used as the main body of printed circuit boards used in electrical and electronic devices.

One of the manufacturing methods for this laminate is to stack a predetermined number of long resin-impregnated base materials such as glass cloth with a thermosetting resin, and to attach a long metal plate to one or both sides of the long resin-impregnated base materials. A continuous laminate in which a laminate is obtained by bonding foils or cover films together, the laminate is preheated to precure the impregnated resin, and then heated and pressure molded using a double belt press to fully cure the precured resin. The manufacturing method is known (Japanese Unexamined Patent Publication No. 155440/1983, etc.).

Preheating in this method of manufacturing continuous laminates involves controlling the temperature gradient so that the temperature increases toward the front in the direction of travel of the laminate; however, such temperature control is not possible in the direction of the radial direction of the laminate. This is not done and the temperature setting is the same between both sides.

[Problem to be solved by the invention]

However, although a laminate preheated under such conditions is preferable in terms of uniform heating, if the pre-curing of the impregnated resin by pre-heating is too small, it will cause problems during the main curing of the next step of hot-press molding. There is a problem in that an excessive amount of pre-cured resin flows out from both side edges, and the thickness of the obtained laminate at both side edges becomes thinner than that at the center, resulting in a decrease in thickness accuracy. In addition, if the precuring by preheating becomes excessive, too little of the precured resin flows out during the above-mentioned main curing, and the air that escapes with the flow of resin cannot escape, resulting in voids in the resulting laminate. The problem arises. In this way, in the hot-pressure molding process, in order to properly flow out the resin and obtain a laminate with a uniform thickness and no voids, the range of options available under conventional preheating conditions is narrow. Ta.

[Means to solve the problem]

In order to solve such problems, the present inventors have made a
As a result of the VR research, it was found that the pre-curing of the impregnated resin on both side edges of the laminate by preheating progresses more than other parts, for example, the heating part in the preheating furnace is heated 3 times in the width direction of the laminate.
By dividing the laminate into two or more zones, making it possible to individually control the temperature, and setting the temperature so that preferably the side edges of the laminate are heated at a higher temperature than the center, We have discovered that it is possible to prevent excessive outflow of pre-cured resin during pressure molding to maintain a constant plate thickness, and also to prevent the occurrence of voids due to insufficient outflow of the resin, leading to the creation of the present invention. It is something.

That is, the present invention provides a method for producing a laminate in which a laminate having a material in which a plurality of elongated resin-impregnated base materials are laminated is pre-cured, and then cured by heating and pressure. The present invention provides a method for manufacturing a laminate, characterized in that the degree of preliminary curing progresses more than in other parts.

At this time, it is also preferable to pre-cure the laminate in a heating furnace in which the pre-curing temperature of both edges in the width direction of the laminate is set higher than the temperature of other parts, and furthermore, the heating furnace It is also preferred to have more than one individually temperature controllable heating zone, and it is also preferred that the heating furnace is an infrared heating furnace.

The present invention will be explained in detail below.

The resin-impregnated base material in the present invention is a base material impregnated with a liquid resin, and the liquid resin is not particularly limited, and may be one dissolved in a solvent, but a liquid thermosetting resin that does not contain a solvent (however, , excluding reactive diluents such as polymerizable vinyl nitrates) are preferred, and typical examples include epoxy resins, unsaturated polyester resins, epoxy vinyl ester resins, diallyl phthalate resins, and the like.

Typical examples of the base material for the resin-impregnated base material include kraft paper, linter paper, glass cloth, glass nonwoven fabric, etc., but the present invention is not limited to these.

The metal foil used on one or both sides of the resin-impregnated base material is typically an electrolytic or rolled copper foil with a thickness of 100 μm or less, and other materials such as aluminum foil may also be used. Examples of the film include polyester film and polyimide film.

The resin-impregnated base material can be produced by impregnating the base material with the resin using a conventionally known method.

These resin-impregnated base materials are manufactured as continuous long products, and after stacking multiple sheets and adjusting the resin content to a predetermined value as necessary, the metal foil or cover film is coated on one or both sides of the resin-impregnated base material. By laminating them together, a continuous laminate of resin-impregnated base materials is obtained.

This laminate is preheated to pre-cure its impregnated resin, but the preheating furnace is divided into three or more heating zones, each corresponding to the width direction of the laminate. It is preferable that the temperature of the zones can be controlled individually, and the heating zones at both ends can be set to a higher temperature than the central heating zone.Heating methods include hot air heating, infrared heating (including far-infrared heating and near-infrared heating), High frequency heating and the like are used, and these can also be used in combination.

In the case of the hot air heating method, by dividing the hot air outlet provided across the width of the laminate to be heated into three or more outlets and blowing out hot air at different temperatures, the temperature at both ends can be raised. , a temperature gradient can be created by lowering the temperature in the center. In addition, in the infrared heating method, the temperature gradient can be easily controlled by dividing the planar or rod-shaped heater into parts along the width direction of the laminate to be heated, and adjusting the temperature of each separately by adjusting the voltage. From that point of view,
Infrared heating method is preferred.

When performing the above preheating, cut out the central part of the precured laminate and heat it at 170°C and 20kg/cIll.
The whole laminate except the upper and lower metal foils or cover films was cured by heating and pressure molding under the following conditions. Percentage of resin flowing out of the laminate during main curing (
The flow rate) is 3 to 20ilf%, 8 and the both side edges of the pre-cured laminate are cut and 170% is
℃ and 20 kg/- under the conditions that the outflow rate when fully cured is 1 to 15% by weight and smaller than the outflow rate of the resin in the center part. Preferably, it is cured.

One method for this purpose is to increase the preheating temperature at both side edges of the laminate and lower the preheating temperature at the center.1. In this case, how to set the temperature difference depends on the type of resin used, but it is usually 2 to 30 t, preferably 4 to 20°C, and the preheating temperature in the center is usually 70 to 180 t. ℃, and the preheating time is usually 1 to 15 minutes.

Here, the term "both side edges" refers to a portion where the ratio of the combined length of both side edges of the total length in the width direction is 60% or less, preferably 5 to 50%.

In the above, the degree of pre-curing was adjusted by the temperature difference, that is, the temperature gradient, but it is also possible to keep the temperature constant and adjust the heating time, or it is also possible to provide a temperature gradient and a heating time difference, and use both together. , or change the air volume,
The degree of pre-curing can also be varied by changing the amount and type of curing agent in the resin.

The preheated laminate is fully cured using a continuous heating and pressure forming machine such as a double belt press to form a laminate.
Post-cure if necessary. Pressure systems such as a roll pressure system, curved surface pressure system, and air surface pressure system are used as double belt presses, but those with a structure that can transfer the laminate while heating and pressurizing it with a pair of endless belts are used. The conditions for this main curing are not particularly limited, and the preferred temperature is usually 90 to 200°C and 1 to 50 kg/-.

〔Example〕

Next, the present invention will be explained in detail.

Incidentally, parts are parts by weight, and % is weight %. Unless otherwise specified, all glass cloths with a thickness of 0.18 strips were used.

Example 1 Epoxy resin with epoxy equivalent of 190 obtained by reaction of bisphenol^ and epichlorohydrin 16.9
26.5 parts of an epoxy resin with an epoxy equivalent of 370 obtained by the reaction of tetrabromobisphenol^ and epichlorohydrin, 26.6 parts of methyltetrahydrophthalic anhydride, 0.7 parts of benzyldimethylamine,
30 parts of an epoxy vinyl ester resin consisting of methacrylate (60%) of an epoxy resin with an epoxy equivalent of 370 obtained by the reaction of tetrabromobisphenol A and epichlorohydrin and styrene monomer (40%) and .-perhexa 3M) ( Polymerization initiator manufactured by NOF ■)
0.6 parts were mixed to prepare a solvent-free liquid resin at room temperature.

This resin is impregnated into each of eight continuous glass cloths each having a width of 1020 cm so that the weight ratio of resin to glass cloth is 43=57. Eight of these resin-impregnated base materials were pressed together, and electrolytic copper foil with a thickness of 35 μm was bonded to both sides of this stacked body to obtain a laminate.

On the other hand, as shown in FIG.
Five heaters are arranged along the width direction as shown in FIG. 1, and the total width of the heaters is 1140w5. Similarly, the same heaters l'', 2°, 3'', 4°, 5
The heater 2.3.4 and 2°, 3°,
4° to the same output, and adjust the heaters 1, 5, 1', and 5' to higher outputs, and 1 minute after both side edges 6a, 6b of the 8-layer body are heated, the temperature reaches 125°C. The temperature reached 120° C. one minute after the central portion 6c was heated, and the temperature was then set to be kept constant and heated at that temperature for 5 minutes.

Note that the temperature was measured inside the laminate by inserting a thermocouple into the center of the laminate in the thickness direction.

When parts of the above-mentioned both side edge parts 6a, 6b and the center part 6C were cut out and heated and press-molded at 170° C. and 20 kg/cIll, the resin flow rates were 2.0 g% and 5.0%, respectively.

Next, the preheated laminate was heated and pressure-molded for 5 minutes under a pressure of 20 g/- using a double belt press set at 170 DEG C. using a high-temperature, high-pressure surface pressure method. Cut the molded product and remove the resin protruding from both sides (trimming)
A laminate with a size of 1,000 cranes x iooom x 1.6 n was obtained. This material was post-cured at 170° C. for 60 minutes without pressure. The following physical property tests were conducted and the results are shown in Table 1.

■ Resin outflow rate (%) from the laminate The laminate was cut into a length of 11,000 tons after being heated and formed.
The amount of resin A (g) flowing out from both sides (width 10200) before trimming and the total weight B (g) of the laminate excluding the upper and lower copper foils are calculated from the following formula.

A(gn/B(g)
5, inward from the center of one side on the left in the length direction of the +n laminate, and 12 ~ inward from the center of one side on the left.
The thickness was measured at the position of the 500 fl part (2) and the 995 fl part (2) inward from the center of one side on the left side.

■ Presence of voids The presence or absence of blistering of the copper foil on the surface of the laminate was visually determined.

Example 2 Based on FIG. 1 in Example 1 (the output settings of the heater for preheating were set as follows).

3.3″ x 212″, 4.4°<1. 1", 5,5゛, and the heating temperature of the laminate by the heater 3.3° in the center is 120°C, and the heaters 2,2'4.4" in the middle on both sides
The heating temperature of the laminate was set to 123℃, and the heater l at both ends was heated to 123℃.
A laminate was obtained in the same manner as in Example 1, except that the heating temperature of the laminate by , 1', 5, 5' was 126°C. After pre-curing, the laminate was cut out from both side edges (the part heated to 126°C?!) and the center part (the part heated to 120°C), and then heated and pressure-molded at 170°C and 20 g/cd. The resin flow rate was They were 1.0% and 5.0%, respectively. The above laminate was measured in the same manner as in Example I, and the results are shown in Table 1.

Comparative Example 1 A laminate was obtained in the same manner as in Example 1 except that the outputs of all the heaters shown in FIG. 1 were the same and the heating temperature of the laminate was 120°C. This laminate was also measured in the same manner as in Example 1, and the results are shown in Table 1.

〔Effect of the invention〕

According to the present invention, in the method for manufacturing a laminate, the preliminary curing of the laminate having the resin-impregnated base material is progressed on both side edges of the laminate more than the other parts, so that the laminate is molded under heat and pressure in a later step. During curing, excessive outflow of resin is suppressed, and the thickness of the resulting laminate is kept constant, with good precision.
In addition, pre-curing progresses slowly in the central part of the laminate, so during the above-mentioned heat and pressure molding, the resin in this part flows smoothly and the air contained in the resin can be removed, allowing the laminate to The generation of voids can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of an apparatus used in carrying out the method of the present invention. In the figure, 1-5.1゛-5° is the heater, 6 is the laminate, 6a
, 6b are both side edges, and 6c is the center. November 1999 105-

Claims (1)

[Scope of Claims] 1. A method for manufacturing a laminate in which a laminate comprising a plurality of elongated resin-impregnated substrates is precured, and then cured by heating and pressure, wherein both edges in the width direction of the laminate are cured by heat and pressure. A method for manufacturing a laminate, characterized in that the degree of pre-curing in some parts is more advanced than in other parts. 2. The method for producing a laminate according to claim 1, wherein the laminate is pre-cured in a heating furnace in which the pre-curing temperature of both edges in the width direction of the laminate is set higher than the temperature of other parts. 3. Pre-curing at least 3 times corresponding to the width direction of the laminate
2. A method for producing a laminate according to claim 1, which is carried out in a heating furnace having two individually temperature controllable heating zones. 4. The method for manufacturing a laminate according to claim 1, 2 or 3, wherein the preliminary curing is performed in an infrared heating furnace.