JPH0333095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for molding multilayer printed wiring boards and laminates such as copper-clad laminates and non-copper-clad laminates in an autoclave.

BACKGROUND ART Conventionally, a hot platen press method is generally known as a technique for forming multilayer printed wiring boards and laminates such as copper-clad laminates and non-copper-clad laminates used in multilayer printed wiring boards.

In the hot platen press method, a large number of sheets of the material to be formed are stacked between hot plates via multiple plate molds (also called mirror plates), and then the prepreg in the material to be formed is heated and pressurized in the atmosphere. The resin part is once softened and then hardened to bond and harden the material to be molded.

Furthermore, a technique is also known in which a material to be molded is vacuum-heated and pressurized to shape it.

This technique involves stacking and arranging the to-be-formed materials 1 in multiple stages on a surface plate (platen) 20 with a mirror plate 24 in between.
Further, the breather 28 is placed on top of the breather 28, and a heat-resistant and flexible vacuum bag film 30 is coated and sealed, and the vacuum bag film 30 is placed in a pressure vessel and sealed, and then the pressure inside the vacuum bag film is reduced, and the vacuum bag film 30 is sealed. A high-pressure gas is supplied inside the mold, and the gas is heated to heat and pressurize the material to be molded to harden the adhesive and mold it.

Problems to be Solved by the Invention However, these techniques have the following problems.

In general, the prepreg material to be molded is heated and pressed while containing some moisture, air during lamination, air contained in the coated paper fabric, and volatile substances from unreacted wood raw materials as air bubbles. As a result, voids are generated inside the laminate (material to be formed), which significantly deteriorates the properties of the laminate.

Therefore, in the hot plate press method, in order to eliminate the air bubbles, an attempt has been made to flow the impregnated resin of the prepreg, which has been softened by heating, at high pressure and push out the air bubbles contained in the prepreg. Heat is radiated from the edge (periphery), and the heating temperature is lower.

On the other hand, the central part of the prepreg accumulates heat and the heating temperature becomes high. Therefore, at this time, the central part of the prepreg is heated to a high temperature and the melt viscosity of the impregnated resin becomes high, but the end part of the prepreg is heated. Since the temperature is not high, the molten viscosity of the impregnated resin is high, and the high pressure (generally 40 kg/cm ² or more) from the hot plate causes a large amount of the molten resin of the prepreg to flow out, making the edge of the laminate thicker than the center. In addition, since the board is subjected to high pressure, it shrinks significantly due to stress, and as a result, the circuit wires on the multilayer circuit board become misaligned, and in addition, warping and twisting occur, causing the product to deteriorate. There is a problem as.

Therefore, in the past, JP-A-56-121734, JP-A-59
Although various improvements have been made, such as those shown in Japanese Patent Application Laid-open No. 59-62113 and Japanese Patent Application Laid-open No. 59-76257, each has advantages and disadvantages, and appropriate improvement measures are desperately needed.

In addition, in the vacuum heating and pressurizing molding technology, for example, when a material to be molded is heated and pressurized according to a heating and pressing program, the material to be molded is generally around 1 to 2 mm even if it is formed into 4 or 6 layers. Although it is thin, the area is 330mm x 500mm, 500mm x 500mm, 600mm
It is wide, such as mm x 600 mm, and because hot air is used for heating, the material to be formed is heated from the surface. Therefore, the material to be formed is heated from the upper and lower surfaces and the four sides of the material to be formed stacked in multiple stages as shown in FIG. The heat transfer to the part 36 is slow, therefore, the end part (periphery part) 35 and the central part 36 of the material to be formed are
As shown by the solid line and the two-dot chain line in the graph of FIG. 11, a large temperature difference occurs.

Due to the temperature difference, the prepreg material to be molded is impregnated with thermosetting resin, so
Due to its characteristics, even though the edges (periphery) 35 of the material to be formed are melted, the center part 36 is not yet melted, and therefore, pressure from above due to pressurization and from the side due to reduced pressure occur. Even if a means of vacuuming is used, the bubbles (gas) contained in the prepreg cannot be pushed out, and therefore it is difficult to expel them into the vacuum outside the prepreg, and the bubbles remain inside the prepreg. do.

Therefore, in order to eliminate the remaining air bubbles, the rate of temperature rise of the material to be formed 1 is slowed down to reduce the temperature difference between the edges (periphery) 35 and the center 36 of the material to be formed, thereby eliminating the remaining air bubbles. However, on the other hand, a new problem has arisen in that the temperature rise is slow, which lengthens the molding time and reduces production efficiency.

Furthermore, since vacuum bag film is used,
It is not economical because it cannot be reused, and it also has problems such as poor sealing efficiency and not being compatible with automation.

The present invention was developed with the aim of solving the various problems mentioned above.

Means for Solving the Problems The method for forming a laminate according to the present invention is such that when a laminate is vacuum-heated and pressure-molded in an autoclave, the material to be formed can be accommodated with a gap, and the material to be formed can be placed on the upper surface. An airtight chamber that can be opened and closed is provided so that pressure can be increased and pressure from the sides can be prevented, and a decompression means for reducing the pressure inside the airtight chamber is detachably provided. The molded material is carried into a container, the airtight chamber is connected to a pressure reducing means to reduce the pressure inside the airtight chamber, and then high pressure gas is supplied into the container to pressurize the material to be formed from the upper surface,
The high-pressure gas is heated and the heated gas is circulated to heat the material to be formed from the upper and lower surfaces to harden the adhesive and form it.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First, prior to the explanation, the laminate as used in the present invention will be explained.

The laminate used in the present invention refers to a multilayer printed wiring board and a laminate such as a copper-clad laminate, a non-copper-clad laminate (for example, an aluminum-clad laminate), etc. used in the multilayer printed wiring board.

The material to be molded is a material for molding the laminate, includes an inner layer circuit board, and is made of prepreg, copper foil, or the like.

Prepreg is made by impregnating a base material such as paper or glass cloth with thermosetting resin varnish such as phenol resin varnish or epoxy resin varnish to create a resin-impregnated sheet, and then drying this resin-impregnated sheet to make it B-stage. It is something.

A copper-clad laminate is obtained by cutting the above prepreg to a fixed size, stacking a plurality of sheets of the prepreg, pasting copper foil on one or both sides of the prepreg, and applying heat and pressure to adhesively cure and mold.

Examples of multilayer printed wiring boards include single-sided copper-clad laminates, prepregs, inner layer circuit boards, prepregs,
Single-sided copper-clad laminates are sequentially laminated, heated and pressed to harden the adhesive, and then formed.After that, various processing steps such as drilling, honing, plating, laminating, baking, development, secondary copper plating, etc. are carried out. After that, it becomes a product.

Furthermore, special terms used in the present invention will be explained.

Voids are air bubbles that are contained in the prepreg used for laminates, such as some moisture, air during lamination, air contained in coated paper cloth, and volatile substances from unreacted resin raw materials. This is a gaseous substance that is generated inside the laminate when it is heated and pressure-molded in its original state. The remaining voids significantly deteriorate the properties of the laminate.

A vacuum bag film is a heat-resistant and flexible film that isolates a material to be molded from the outside and brings it into close contact with the material by vacuum pressure. And generally, nylon 6, nylon
66, plastic films such as polytetrafluoroethylene are used.

A breather is a device that allows air and gas (bubbles) generated by reaction to pass through to maintain a uniform pressure load even when the pressure inside the vacuum bag film is reduced and pressure is applied to the container. Generally, heat-resistant glass cloth is used.

A sealant is used to seal the material to be formed on a surface plate (platen).
A sticky clay-like substance is generally used to completely seal the mold and ensure airtightness during molding.

A surface plate (platen) is a flat jig that stacks materials to be formed and receives pressure from the top surface of the materials. A flat, smooth metal plate is used.

Next, the configuration of the embodiment will be explained.

As shown in Figures 1 and 2, 1 is a material to be molded such as an inner layer circuit board, prepreg, copper foil, etc., 2 is a pressure vessel that accommodates the material to be molded, and 3 is an opening/closing device for airtightly closing the container 2. It is a door for use.

A is a high-pressure gas supply means for supplying high-pressure gas (for example, high-pressure nitrogen gas, high-pressure carbon dioxide gas, high-pressure air, etc.) into the pressure vessel 2.

B is a heating/cooling means that heats or cools the gas supplied into the container 2 via the heat exchanger 4.

C is a circulation means that blows and circulates the gas heated or cooled by the heating/cooling means into the airtight chamber introduced into the container 2.

D is an airtight chamber that can accommodate the material to be formed with a gap and is equipped with a pressing member that presses the material to be formed from the upper surface, and is also detachably provided with a pressure reducing means for reducing the pressure in the airtight chamber. .

E is a pressure reducing means for reducing the pressure inside the airtight chamber.

Next, details of each means and each member will be explained.

The high pressure gas supply means A is generally provided within the container 2.
High pressure chitso gas less than 20Kg/ ^cm2 , high pressure carbon dioxide gas,
A high-pressure gas such as high-pressure air is supplied through an automatic valve 6, and the gas is heated or cooled through a heat exchanger 4. And automatic valve 7
Exhausted through. Furthermore, a safety valve 11 is provided to reduce the pressure inside the container 2 when it exceeds a predetermined pressure.

The heating and cooling means B is designed to supply high pressure steam from the outside of the container 2 to the heat exchanger 4 inside the container 2 as shown in FIGS. 1 and 2. An automatic valve 9 for supplying water is provided to penetrate the container 2 and communicate with the heat exchanger 4, and an automatic drain valve 10 is further provided in communication with the lower part of the container 2 from below the heat exchanger. It is.

In addition, as another example of the heating and cooling means, a means for heating and cooling may be provided outside the container 2, and the heating and cooling gas may be supplied into the container 2. Also, the heat source may be an electric heater or the like. May be used.

The circulation means C includes a fan 12 provided inside the container 2, and a motor 13 for driving the fan installed outside the container 2 so as to be airtight. The heating or cooling gas sent by the fan 12 passes through the outer periphery of the wind barrel plate 14 shown in FIG. It is configured like this.

As shown in FIG. 3, in the airtight chamber D, the workpiece 1 loaded on the surface plate 20 is surrounded by a side pressure prevention member F made of a rectangular frame with an appropriate gap provided.
The lateral pressure prevention member F is sealed with a sealing member J, and in order to make the material 1 to be formed airtight, a flat pressing member C that presses the material 1 to be formed is placed on the upper part of the lateral pressure prevention member F to prevent lateral pressure. The lateral pressure prevention member F is installed on the member F so as to be movable up and down, and sealed with the seal member H.
The inside of the chamber is airtight, and the molded material 1 can be easily inserted and removed, and the airtight chamber can be easily disassembled and assembled. Further, the surface plate 20 is provided with a vacuum path 21 for reducing the pressure in the airtight chamber, and is connected to and disconnected from a pressure reducing means E, which will be described later, by a coupler 27.

FIG. 4 shows a top view of FIG. 3, and the airtight chamber D has a rectangular shape slightly larger than the material 1 to be formed.

FIG. 5 shows another embodiment of the airtight chamber D, in which a sealing member H is interposed on the upper surface of the side pressure preventing member F and on the outer periphery of the pressing member G, and is configured to be movable up and down.

As shown in FIGS. 1 and 2, the pressure reducing means E is a vacuum pump 17 installed outside the container 2, which is connected via an automatic valve 18 to the inside of the container 2 via piping. And the coupler 27 at the tip is
Vacuum path 2 of surface plate 20 to reduce pressure inside airtight chamber D
It is provided so that it can be attached to and detached from the coupler 27 of the first piping section.

The pressing member G of the surface plate 20 is a flat plate having good thermal conductivity and having a flat surface in contact with the material to be formed 1 and a smooth surface.

Here, in the present invention, a state in which the materials to be formed are stacked and placed will be explained.

As shown in FIG. 6, there is a vacuum path 21 on the surface plate 20.
The ventilation plate 26 provided with
4 ~ Release film 31 ~ Copper foil 32 ~ Prepreg 3
3 ~ Inner layer circuit board 34 ~ Prepreg 33 ~ Copper foil 32
~ Release film 31 ~ Mirror plate 24 ~ Release film 31 ~ Copper foil 32 ~ Prepreg 33 ~ Inner layer circuit board 3
4 ~ Prepreg 33 ~ Copper foil 32 ~ Release film 3
1 to 24 are stacked one after another, and this stacking is performed in multiple stages.

Then, the material to be formed 1 is surrounded by a lateral pressure prevention member F and sealed with a sealing member J, furthermore, a pressing member G is placed on the material to be formed 1, and the material to be formed 1 is airtighted by a sealing member H, Check its air seal condition.

As a means for sealing, the lateral pressure prevention member F, the pressing member G, and the sealing member H may be first assembled integrally and placed over the molded material 1 loaded on the surface plate 20 for sealing. Also, removal after molding may be performed using any of the above methods, and is not limited to the above methods.

Next, the operation will be explained according to the heating and pressurizing program shown in FIG.

The material to be formed 1, which has been prepared by being housed and sealed inside the airtight chamber D, is placed on a shelf of a cart 38 shown in FIGS. 1 and 2 and carried into the pressure vessel 2. Next, surface plate 2
The piping section of the vacuum path No. 0 is connected to the container internal piping section of the pressure reducing means E with a coupler 27, and the door 3 is closed to seal the container 2.

Next, the vacuum pump 17 and automatic valve 18 are operated to reduce the pressure in the airtight chamber D. Next, the automatic valve 6 is operated to supply high-pressure gas into the container 2, and the automatic valve 8 is operated to supply high-pressure steam to the heat exchanger 4 in the container 2, thereby heating the high-pressure gas.

Next, by driving the motor 13 and rotating the fan 12, the heated high-pressure gas is circulated through the airtight chamber via the wind barrel plate 14.

Then, the material to be formed 1 is pressed by pressure from above and heated from the upper and lower surfaces.

Then, the material to be formed 1 is heated and pressurized.

In this way, the material to be formed 1 is heated from above and below, and heat is transferred from the upper and lower surfaces of the material to be formed 1, but since the gap 37 in the airtight chamber D is in a high vacuum, the material to be formed 1 There is no heat dissipation from the edges (periphery) of the prepreg plane of the material 1 to be formed, and the upper end (periphery) 35 and center 36 of the prepreg plane of the material 1 to be formed can be heated almost uniformly. The temperature difference between the upper central part 36 and the edge (peripheral part) 35 is eliminated, and the central part 3 on the prepreg plane of each stage is
The melt viscosities of the melt viscosity at the end portion 6 and the end portion (periphery portion) 35 are approximately equal.

Then, as the heating of the laminated material 1 to be formed progresses and the melt viscosity of the prepreg resin portion reaches its minimum, the air bubbles existing in the prepreg resin portion will be removed.
It will float above the resin part, but due to pressure from above and vacuum from the side, it will pass between the prepreg and copper foil, move to the edge (periphery) of the prepreg, and be discharged into the vacuum. be done.

Subsequently, the temperature of the material to be formed 1 is further increased, and once it reaches a specified temperature, that temperature is maintained for a while, and the material to be formed 1 is bonded and hardened.

Next, the automatic valve 8 is operated in reverse to stop the supply of high-pressure steam, and then the automatic valve 9 is operated to supply cooling water to the heat exchanger 4 to cool the gas circulating in the container 2. The molded material 1 in the airtight chamber D is cooled.

Next, the automatic valve 6 is operated in reverse to gradually reduce the pressure inside the container 2.

When the material to be formed 1 is cooled, all operations are stopped, the door 3 is opened, and the material to be formed 1 is carried out to the outside, completing one process.

Note that during cooling, if a means for introducing air into the airtight chamber D is used, the cooling heat of the cooled gas is transmitted from the airtight chamber to the air to the workpiece 1, thereby cooling the workpiece in a short time. can do.

Here, the prepreg, copper foil, and inner layer circuit board with dimensions: 330 mm x 500 mm are sandwiched between mirror plates as shown in Fig. 6, and stacked one on top of the other to a height of about 60 mm. At this time, the temperature detector 25 is appropriately inserted into the end portion (periphery portion) 35 and center portion 36 of the material to be formed 1 .
Then, when molding was performed under the conditions of the heating and pressing program shown in FIG. 7, there was no temperature difference between the center part and the edge part (periphery part) of the prepreg of the material to be molded 1, as shown in FIG. As a result, it was possible to form a void-free four-layer copper-clad laminate with a uniform thickness within a predetermined time.

Note that the heating and pressurizing program used in the present invention may be under conditions other than those shown in FIG. 7, such as the one shown in FIG. 9, and is not limited to the embodiments of the present invention.

Effects of the Invention As described above, the present invention provides the following effects.

An openable and closable airtight chamber capable of accommodating a material to be formed with a gap in vacuum heating and pressure forming of a laminate in an autoclave, and capable of pressurizing the material from the top and preventing pressure from the sides. A depressurizing means for reducing the pressure inside the airtight chamber is detachably provided, a material to be formed is accommodated in the airtight chamber, sealed and carried into a pressure vessel, and the airtight chamber is connected to the pressure reducing means to remove the inside of the airtight chamber. The pressure is reduced, and then high-pressure gas is supplied into the container to pressurize the material to be formed, and the high-pressure gas is heated and circulated to heat the material to be formed, harden the adhesive, and form the material. The pressurization of the material is prevented by the side pressure prevention member in the airtight chamber, and the pressure is evenly applied from the upper surface of the material to be formed by hydrostatic pressure.

Furthermore, since the airtight chamber is kept in a vacuum during heating of the material to be formed, heat is not transferred from the side surfaces, and there is no heat dissipation from the ends of the material to be formed, and heat is evenly transferred from the upper and lower surfaces.

Therefore, the temperature difference between the center and the ends of each prepreg of the material to be molded disappears, and the resin becomes uniformly molten and becomes easier to flow. Therefore, by vacuuming, the molten resin of the prepreg flows from the center to the ends. It is possible to uniformly move to flow out an appropriate amount and exhaust air bubbles into a vacuum, and it is possible to form a bide-free laminate with a uniform thickness within a predetermined time.

In addition, because the pressure applied to the material to be formed is lower than that of the conventional hot platen press method, there is less shrinkage due to stress, eliminating misalignment of circuit wires on multilayer circuit boards, reducing warping and twisting, and increasing board thickness. This combination of uniformity and dimensional stability results in a high-quality laminate with good dimensional stability.

In addition, since it is reusable and has an airtight chamber that allows the material to be molded to be easily inserted and removed, the conventional vacuum bag film that cannot be reused is no longer necessary, making it economical and easier to work with, allowing for automation. We can also expect to respond to this.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway schematic side view showing one embodiment of the device according to the present invention. FIG. 2 is a schematic vertical sectional view of the apparatus shown in FIG. 1. FIG. 3 is a schematic longitudinal cross-sectional view of an airtight chamber that accommodates the material to be formed. FIG. 4 is a top view of FIG. 3. FIG. 5 is a schematic vertical sectional view of another embodiment of the airtight chamber. FIG. 6 is a schematic longitudinal cross-sectional view showing a state in which materials to be formed are stacked and placed in the present invention. FIG. 7 is a diagram showing an embodiment of a heating and pressing program for molding a material to be molded according to the present invention. FIG. 8 shows the molded material of the present invention in the seventh
This figure shows actual measurement values obtained by molding according to the heating and pressing program set in the figure. FIG. 9 is a diagram showing another embodiment of the heating and pressing program for molding the material to be molded according to the present invention. FIG. 10 is a schematic vertical cross-sectional view showing a conventional method of loading materials to be formed, covering them with a vacuum bag film, and sealing them. FIG. 11 is a diagram showing an example of a prior art heating and pressing program for molding a material to be molded. In these figures, A: high pressure gas supply means;
B: heating and cooling means, C: circulation means, D: airtight chamber,
E: pressure reduction means, F: lateral pressure prevention member, G: pressing member, H: sealing member, J: sealing member, 1: molded material, 2: pressure vessel, 3: door, 4: heat exchanger,
6, 7, 8, 9: automatic valve, 10: safety valve, 12:
Fan, 13: Motor, 14: Wind body plate, 17: Vacuum pump, 18, 19: Automatic valve, 20: Surface plate, 2
1: Vacuum path, 24: Mirror plate, 25: Temperature detector,
26: ventilation plate, 27: coupler, 28: breather, 29: sealant, 30: vacuum bag film, 31: release film, 32: copper foil, 33: prepreg, 34: inner layer circuit board, 35: molded material End part, 36: Center part of the material to be formed, 37: Gap part,
38: Trolley.

Claims (1)

[Claims] 1. In vacuum heating and pressure forming of a laminate in an autoclave, an openable and closable gas chamber is used that can accommodate the material to be formed with a gap and can pressurize the material from the top surface while preventing pressure from the sides. A closed chamber is provided, and a pressure reducing means for reducing the pressure in the airtight chamber is detachably provided, the material to be formed is accommodated in the airtight chamber, sealed, and carried into a pressure vessel, and the airtight chamber is connected to the pressure reduction means to be removed from the airtight chamber. is depressurized, and then high-pressure gas is supplied into the container to pressurize the material to be formed, and the high-pressure gas is heated and circulated to heat the material to be formed, harden the adhesive, and form the material. How to form a board.