JP2002079538A - Method for producing metal-clad laminated plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a metal-clad laminated plate improved in dimensional change ratio in the method in which metal foil is molded by being energized to be resistance-heated. SOLUTION: In the method, a body 4, in which laminates 5 in which the lengthy metal foil 1 is folded repeatedly and strung, and a prepreg body 2 is placed between the parts of the folded foil 1 and molding plates 3 in which insulating coats are applied on the surfaces of aluminum plates are arranged alternately, is pressed, and the laminates 5 are resistance-heated by energizing the metal foil 1 and press-molded. The pressure is released for 5-20 min before cooling is started, and then the body 4 is cooled by increasing the pressure to be 1.1-1.3 times as high as the molding pressure during heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal-clad laminate used for a printed wiring board, and more specifically, to a laminate in which a prepreg body having an inner-layer circuit board is arranged between metal foils. And a pressing plate formed by alternately arranging a forming plate having an insulating coating formed on the surface of an aluminum plate, and pressing the pressurized body, supplying power to the metal foil to heat and heat the laminate by resistance heating. The present invention relates to a method for producing a metal-clad laminate subjected to pressure forming.

[0002]

2. Description of the Related Art A metal-clad laminate used for a printed wiring board is composed of a prepreg or a prepreg composed of a prepreg combined with an inner-layer circuit board and a laminate in which a metal foil is laminated on an outer layer and a molding plate. A molding method in which pressurized bodies formed alternately are pressed and heated and pressed is employed. Examples of the molding method include a method in which a pressurized body is sandwiched between hot plates of a press and pressure is applied while heating by heat transfer from the hot platen, or a method in which a pressurized body as described in JP-A-8-506289 is used. A method has been used in which power is supplied to a metal foil in a pressed state, and pressure is applied while heating by resistance heating.
Note that resistance heating is a method in which a current is applied to a conductor having electric resistance and heating is performed using heat generated by the Joule effect.

As a method of applying pressure while heating by resistance heating, for example, as shown in FIG.
A long metal foil is used as the metal foil 21 and a plurality of the metal foils 21 are folded back and bent, and the metal foils 21 which are bent and face each other are bent.
A plurality of prepregs 22 and molding plates 23 are alternately arranged therebetween to produce a pressure-receiving body 24. Next, in the above-described method, when power is supplied to the metal foil 21 in a state where the pressed body 24 is pressed between the pressurizing plates 11 of the press, the prepreg 22 is heated by resistance heating. In addition, the code | symbol 12 in a figure shows a vacuum tank, and the code | symbol 13 shows a vacuum pump.

[0004] In the above-described forming method by resistance heating, since a metal foil can be directly heated using a heat source, even if a large number of metal-clad laminates are formed on one pressurized body, they must be uniformly heated. Therefore, it is possible to obtain a metal-clad laminate having little variation in quality.

[0005]

In the above-mentioned method using resistance heating, a plate formed by applying an insulating coating to the surface of an aluminum plate is widely used as a forming plate. A metal-clad laminate formed using the above-described aluminum plate forming plate tends to have a large dimensional change rate.

On the other hand, with the recent expansion of the use of electronic equipment and electric equipment, multilayer printed wiring boards including an inner circuit board are frequently used as printed wiring boards. In this multilayer printed wiring board, the circuit width and the circuit between the inner layer and the outer layer are narrower, and high density is adopted.
For multilayer metal-clad laminates used for multilayer printed wiring boards, it is required to improve the positioning accuracy of the inner layer circuit and the outer layer circuit, and therefore, those with a good dimensional change rate are required. Have been.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a metal-clad laminate in which power is supplied to a metal foil and formed by resistance heating. It is an object of the present invention to provide a method for manufacturing a metal-clad laminate, which makes the method more favorable.

[0008]

Means for Solving the Problems As a result of intensive studies conducted by the present inventor to achieve the above-mentioned object, a forming plate having an aluminum plate with an insulating coating on the surface is made of a metal-clad laminated plate. By comparison, the coefficient of linear expansion is large, and the plate for molding expands and contracts greatly during heating and cooling. Due to this effect, stress is accumulated inside the metal-clad laminate, and the dimensional change rate is reduced. As a result of further study, the pressure during molding was released for 5 to 20 minutes immediately before the start of cooling, and thereafter,
It has been found that when a pressure 1.1 to 1 to 3 times the pressure at the time of heating is applied and cooled, the dimensional change rate of the metal-clad laminate is improved, and the present invention has been completed.

In the method for manufacturing a metal-clad laminate according to the first aspect, a long metal foil is folded and folded in multiple layers.
Pressing a pressure-formed body formed by alternately arranging a laminate formed with a prepreg body between the metal foils and a forming plate having an aluminum plate coated with an insulating coating, In the method for producing a metal-clad laminate in which the laminate is heated by resistance heating by supplying power to a metal foil and pressure-molded, the pressure is released for 5 to 20 minutes before starting cooling, and thereafter, when heating is performed. 1.1 to molding pressure
It is characterized in that the pressure object is cooled by applying three times the pressure. The above manufacturing method releases the stress generated by heating and pressurization during molding by releasing for 5 to 20 minutes before starting the cooling, so that the stress is accumulated inside the metal-clad laminate. It can be prevented.

According to a second aspect of the present invention, in the method for manufacturing a metal-clad laminate according to the first aspect, the cooling temperature of the laminate is set such that a glass transition temperature of the metal-clad laminate from the start of cooling. The cooling rate is not less than 0.5 ° C./min and not more than 1 ° C./min.
As described above, it is possible to prevent the metal-clad laminate from receiving stress due to shrinkage of the forming plate.

The above-mentioned glass transition temperature is determined from a heat generation curve (heat absorption) by measuring the heat generation by raising the temperature at a rate of 20 ° C./min using a differential scanning calorimeter (DSC). is there.

According to a third aspect of the present invention, in the method for manufacturing a metal-clad laminate according to the first or second aspect, the molding plate has a coefficient of linear expansion of 19 to 25 ×. It is characterized by being 10 ⁻⁶ cm / cm · ° C.

[0013] The coefficient of linear expansion referred to in the present invention is a coefficient of linear expansion at a temperature of 20 to 100 ° C.

According to a fourth aspect of the present invention, in the method for manufacturing a metal-clad laminate according to any one of the first to third aspects, the prepreg body is used for an inner layer having a circuit formed on a surface thereof. The prepreg is provided outside the circuit board. According to the above, it is possible to form a multilayer metal-clad laminate having a good dimensional change rate and improved positioning accuracy of the inner layer circuit and the outer layer circuit.

[0015]

1 to 3 show an embodiment of the present invention. FIG. 1 is an explanatory view for explaining a method for manufacturing a metal-clad laminate, and FIG. FIG. 3A is a cross-sectional view showing a combined state before forming a multilayer metal-clad laminate, and FIG. 3B is a cross-sectional view of the multilayer metal-clad laminate.

The metal-clad laminate, which is the object of the present invention, supplies power to a long and continuous metal foil 1 that is folded back into multiple layers.
It is molded while heating by resistance heating. The metal-clad laminate is formed by heating a prepreg body 2 and a laminate 5 in which a metal foil 1 is laminated on an outer layer thereof. As shown in FIG. 3 (a), the combination structure of the metal-clad laminate is such that a prepreg 9 is arranged outside a circuit board 7 for an inner layer having a circuit 8 formed on the surface to form a prepreg body 2, and further, an outer layer on both sides thereof is formed. The metal foil 1 is arranged to form a laminate 5. The prepreg 9 is obtained by impregnating a base material such as a glass fabric or non-woven fabric with a thermosetting resin such as an epoxy resin, and semi-curing the resin in a B-stage state. The metal foil 1 is, for example, a copper foil. When the laminate 5 is heated and pressurized, the resin of the prepreg 8 is cured to form an insulating layer 9a, and becomes a multilayer metal-clad laminate.

In the method of manufacturing the metal-clad laminate, a pair of long metal foils 1 and 1 are used. A pair of laminates 5 are formed on the metal foils 1 and 1 with a prepreg body 2 interposed therebetween. The laminated body 4 and the forming plate 3 are alternately arranged while folding the foils 1 and 1 into a plurality of layers, thereby producing the pressure-receiving body 4. Next, in the above-described manufacturing method, the pressure-receiving body 4 is put into the vacuum chamber 12 and set between the pressurizing plates 11, 11, and the power is supplied to the metal foil 1 via the pressurizing plates 11, 11. Connecting. At this time, a cushion material such as aramid fiber or a heat conduction adjusting material may be interposed between the pressing plate 11 and the pressure-receiving body 4 as necessary.

The molding plate 3 used in the above-described manufacturing method is an electrically insulating plate having an aluminum plate coated with an insulating coating on the surface. As the molding plate 3, a plate having a coefficient of linear expansion in the range of 19 to 25 × 10 ⁻⁶ cm / cm · ° C. can be used. For example, a SUS forming plate that is frequently used in a method of heating by heat transfer from a hot plate has a linear expansion coefficient of 15 to 18 × 10 ⁻⁶ cm /.
cm · ° C., and the linear expansion coefficient of the forming plate 3 having the surface of the aluminum plate coated with an insulating material is SUS
It is larger than the linear expansion coefficient of a molding plate made of steel.

In the above manufacturing method, the pressure-receiving body 4 is
Pressure is applied at 1 and 11. At this time, the pressure to be applied is preferably about the contact pressure. Next, in the above manufacturing method, the vacuum pump 13 is operated, and the atmospheric pressure of the vacuum chamber 12 is set to 5,000 to 40.
After a vacuum state of about 000 Pa is reached, power is supplied to the metal foil 1 to heat the laminate 5 by resistance heating.

An example of molding conditions such as temperature and pressure during the above heating will be described with reference to FIG. FIG. 2 (a)
Indicates a lapse of time and a temperature curve T of the laminate, and (b) indicates a pressure curve P. The temperature curve T rises from the point of time (t0) when the metal foil 1 is supplied, and reaches a predetermined molding temperature (symbol B) through a temperature (symbol A) at which the resin in the prepreg 9 melts at time (t1). . The pressure curve P is maintained at a contact pressure (symbol P1) until the temperature of the laminate 5 reaches a temperature (symbol A) at which the resin in the prepreg melts from the start of pressurization, and thereafter, a predetermined molding is performed. Pressure (sign P2)
Press. The molding pressure (P2) is generally about 1 to 3 MPa. The atmospheric pressure in the vacuum chamber 12 is maintained at the above-mentioned vacuum state from the start of pressurization until the temperature of the laminated body 5 reaches the temperature (symbol A) at which the resin in the prepreg melts. Is returned.

The production method of the present invention is carried out by the following method immediately after cooling after heating and before cooling. In the manufacturing method, the pressure of the pressurized body 4 after the completion of the heating is released for 5 to 20 minutes (between t2 and t3 in the figure) before the start of the cooling, and thereafter, the pressure is reduced during the heating. 1.1 to 3 times the pressure of pressure (P2) (symbol P
3) is pressed to cool the pressure-receiving body 4.

In the above manufacturing method, since the stress generated inside the laminate 5 due to heating and pressurization is released during molding by releasing the pressure for 5 to 20 minutes before the cooling is started, the stress is reduced. It can prevent accumulation. As a result, the above manufacturing method can obtain a metal-clad laminate having a good dimensional change rate. Above all, the multilayer metal-clad laminate improves the positioning accuracy of the inner layer circuit and the outer layer circuit. When the pressure release time is less than 5 minutes, the effect of improving the dimensional change rate is insufficient, and when the pressure release time exceeds 20 minutes, the surface roughness of the metal-clad laminate may increase. At the same time, since the start of cooling is delayed, productivity may be reduced.

In the above manufacturing method, a metal having a good dimensional change rate is obtained by applying a pressure (P3) which is 1.1 to 3 times the molding pressure (P2) at the time of cooling during cooling. A laminated board can be obtained. Above all, the multilayer metal-clad laminate improves the positioning accuracy of the inner layer circuit and the outer layer circuit. If the pressure is less than 1.1 times the molding pressure (P2) at the time of heating, the effect of improving the dimensional change rate is insufficient, and the pressure is 3 times the molding pressure (P2) at the time of heating. If the number exceeds twice, there is a possibility that troubles such as deformation of the molding plate may occur.

In the above manufacturing method, the temperature curve T
It is preferable to lower at a cooling rate of 0.5 ° C./min or more and 1 ° C./min or less from the start of cooling until the temperature of the metal-clad laminate reaches the glass transition temperature (C in the figure) or lower. If the temperature curve T is a cooling rate exceeding 1 ° C./min, the warpage of the metal-clad laminate may increase. If the cooling rate is less than 0.5 ° C./min, it takes time to cool. There is a risk of lowering productivity. When the temperature curve T exceeds the glass transition temperature (C in the figure) of the metal-clad laminate, 1
Quench at a cooling rate above ° C / min.

The pressurized body 4 is cooled by the pressing plate 1
Various cooling methods can be adopted, such as cooling water passing through the cooling chambers 1 and 11, cooling air to be conveyed to the dedicated cooling chamber and blowing cool air around, and cooling.

As described above, according to the manufacturing method, the laminate 5 is heated by resistance heating by supplying power to the metal foil 1,
A multilayer metal-clad laminate in which the resin in the prepreg 9 is cured to form the insulating layer 9a can be obtained. The metal-clad laminate has a good dimensional change rate.

In the above-mentioned manufacturing method, two long metal foils 1 are used as a pair. However, one long metal foil is used, and the prepreg is folded between the metal foils. It may be a laminated body sandwiched therebetween. In addition, the prepreg body 2 may be one in which a plurality of inner layer circuit boards 7 are stacked via a prepreg, or one in which the prepreg is alone. In particular, a multilayer metal-clad laminate using a complicated circuit 8 of the inner layer circuit board 7 remarkably exerts the effects of the present invention.

[0028]

EXAMPLES In order to confirm the effects of the present invention, the following Examples and Comparative Examples were carried out to produce multilayer metal-clad laminates.

Example 1 A pressure-receiving member was formed as follows. A prepreg (R1661 manufactured by Matsushita Electric Works, Ltd.) in which glass fabric was impregnated with an epoxy resin and had a thickness of 0.1 mm and a resin amount of 52% by weight was used. The circuit board for the inner layer having a circuit formed on the surface is a copper foil (thickness of 35) on the surface of a copper-clad laminate (R1766, manufactured by Matsushita Electric Works, Ltd.).
μm) was etched, and a 0.1 mm-thick substrate having a circuit with an etching rate of 50% and alignment holes formed on both surfaces was used. The prepreg body was prepared by arranging one prepreg on each side of the inner layer circuit board. The prepreg had a glass transition temperature of 130 ° C. and a melting start temperature of 90 ° C. Also, the molding plate is
1mm thick with insulating coating formed on the surface of aluminum plate
Was used. The linear expansion coefficient of this molding plate is 2
It was 1 × 10 ⁻⁶ cm / cm · ° C.

As the metal foil, a pair of long copper foils having a thickness of 18 μm was used. And, between the pair of copper foils, while forming a laminate sandwiching the prepreg body, while stacking and bending a plurality of the pair of copper foils, the laminate and the forming plate are alternately arranged, A block having 50 sets of laminates was prepared. At this time, a thermocouple was set on the 25th set of stacked bodies from the top, and the temperature at the time of molding was checked. Next, as shown in FIG. 1, the pressure-receiving body is put into a vacuum chamber, and is set between pressurizing plates of a press.
A power supply was connected to the metal foil via a pressing plate of a press.

The pressure of the object to be charged into the vacuum chamber was first set to a contact pressure, and a vacuum pump was operated to make a vacuum state of 6650 Pa. Then, power was supplied to the copper foil. Molding temperature is 90 ° C
, The pressure was increased to 1 MPa, and the atmospheric pressure was released from the vacuum state to normal pressure. The maximum molding temperature was 185 ° C., and the molding was performed by heating for 60 minutes from the start of heating.

Next, after the power supply was stopped, the pressure was released to a non-pressurized state for 5 minutes, and then cooling was performed while the pressure was increased to 1.1 MPa. At this time, the cooling water passed through the pressure plate was adjusted, and the cooling rate was gradually decreased to 1 ° C./min until the temperature of the laminate reached 130 ° C., followed by rapid cooling.
A multilayer metal-clad laminate was obtained.

(Example 2) A multilayer metal-clad laminate was obtained in the same manner as in Example 1, except that after the power supply was stopped, the pressure was released to a non-pressurized state for 20 minutes.

Example 3 A multilayer metal-clad laminate was obtained in the same manner as in Example 1 except that the pressure was increased to 3 MPa during cooling.

Example 4 After the power supply was stopped, the pressure was released to a non-pressurized state for 20 minutes, and then the pressure was increased to 3 MPa.
A multilayer metal-clad laminate was obtained in the same manner as in Example 1 except that cooling was performed in a state where pressure was applied.

Example 5 The temperature of the laminate during cooling was 1
A multilayer metal-clad laminate was obtained in the same manner as in Example 1, except that the cooling rate was 0.5 ° C./min until the temperature reached 30 ° C.

Example 6 A multilayer metal-clad laminate was obtained in the same manner as in Example 5, except that the pressure was increased to 3 MPa during cooling.

Example 7 The same procedure was carried out except that a 1 mm-thick plate in which an insulating coating was formed on the surface of an aluminum plate having a linear expansion coefficient of 23 × 10 ⁻⁶ cm / cm · ° C. was used as the molding plate. A multilayer metal-clad laminate was obtained in the same manner as in Example 1.

Example 8 A multilayer metal-clad laminate was obtained in the same manner as in Example 7, except that the pressure was increased to 3 MPa during cooling.

(Embodiment 9) During the cooling, the temperature of the laminate was 1
A multilayer metal-clad laminate was obtained in the same manner as in Example 1 except that the cooling rate was 2 ° C./min until the temperature reached 30 ° C.

Example 10 Example 1 was repeated except that a 1 mm thick SUS plate insulated with a linear expansion coefficient of 15 × 10 ⁻⁶ cm / cm · ° C. was used as the molding plate. In the same manner as in the above, a multilayer metal-clad laminate was obtained.

(Comparative Example 1) A multilayer metal-clad laminate was obtained in the same manner as in Example 1 except that after the power supply was stopped, the pressure was released to a non-pressurized state for 3 minutes.

(Comparative Example 2) A multilayer metal-clad laminate was obtained in the same manner as in Example 1 except that after the power supply was stopped, the pressure was released to a non-pressurized state for 30 minutes.

(Comparative Example 3) During cooling, the pressure was set to 0.5MPa.
A multilayer metal-clad laminate was obtained in the same manner as in Example 1 except that the pressure was changed to a.

Comparative Example 4 A multilayer metal-clad laminate was formed in the same manner as in Example 1 except that the pressure was increased to 4 MPa during cooling. An abnormality in which the molding plate was deformed after molding occurred.

(Comparative Example 5) As a molding plate, a plate having a thickness of 1 mm in which an insulating coating was formed on the surface of an aluminum plate having a linear expansion coefficient of 23 × 10 ^-6 cm / cm · ° C was used. Further, after the power supply was stopped, the pressure was released to a non-pressurized state for one minute, and thereafter, cooling was performed while the pressure was increased to 1 MPa. The cooling rate was set to 1.5 ° C./min until the temperature of the laminate reached 130 ° C. during cooling. Otherwise in the same manner as in Example 1, a multilayer metal-clad laminate was obtained.

(Evaluation of the dimensional change rate) The pattern position accuracy was measured as the dimensional change rate of the metal-clad laminates obtained in Examples and Comparative Examples. The pattern position accuracy is determined by measuring the distance between the reference point (reference guide hole) and the pattern position at 10 points.
The deviation from the design value was calculated. Table 1 shows the pattern pattern having the largest deviation.

(Evaluation of Other Characteristics) As the characteristics of the metal-clad laminates obtained in Examples and Comparative Examples, the surface roughness, warpage, and appearance wrinkle occurrence rate were measured according to JIS-C-6481. evaluated. The surface roughness was measured by obliquely measuring the surface of the copper foil with a surface roughness meter, and the maximum value (Rmax) was calculated. The warpage was measured by heating a sample prepared by etching the entire surface at 170 ° C. for 1 hour, and then measuring the amount of warpage. The appearance of wrinkles
The surface of 1,000 pieces of copper foil was visually observed, and the presence or absence of wrinkle defects was inspected and calculated. The results were as shown in Table 1.

[0049]

[Table 1]

In each of the embodiments, the pattern position accuracy is 40.
Comparative Examples 1 to 50 μm or less
Samples Nos. 3 and 5 had a large pattern position accuracy of 70 to 100 μm. In Comparative Example 4, an abnormality in which the molding plate was deformed occurred. Further, in Example 1 in which the cooling rate was 1 ° C./min until the temperature reached 130 ° C., the warpage was better than that in Example 9. In Example 10 using a molding plate having a linear expansion coefficient of 15 × 10 ⁻⁶ cm / cm · ° C., the pattern position accuracy was good, but wrinkle defects occurred.

[0051]

According to the method for manufacturing a metal-clad laminate according to claims 1 to 4, a metal-clad laminate having a good dimensional change rate can be obtained. In particular, for multi-layer metal-clad laminates,
It is possible to obtain a product having a good dimensional change rate and improved positioning accuracy between the inner layer circuit and the outer layer circuit.

[Brief description of the drawings]

FIG. 1 is an explanatory view illustrating an example of an embodiment of the present invention and illustrating a method of manufacturing a metal-clad laminate.

FIGS. 2A and 2B are graphs showing the lapse of time, temperature, and pressure according to the present invention, wherein FIG. 2A is a temperature curve, and FIG.

FIG. 3A is a cross-sectional view showing a combination state before forming a multilayer metal-clad laminate, and FIG. 3B is a cross-sectional view of the multilayer metal-clad laminate.

FIG. 4 is an explanatory view illustrating a conventional manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal foil 2 Prepreg body 3 Forming plate 4 Pressed body 5 Laminate 11 Press plate

Claims (4)

[Claims] 1. A laminate comprising a plurality of long metal foils which are folded back and formed, and a prepreg body is formed between the metal foils, and a laminate for forming an insulating coating on the surface of an aluminum plate. In a method for manufacturing a metal-clad laminate, the plate is pressed alternately and a pressure-formed body formed is pressed, and the metal foil is supplied with power to the metal foil to heat the laminate by resistance heating. Before starting cooling 5
A method for producing a metal-clad laminate, comprising releasing the pressurized body by applying pressure that is 1.1 to 3 times the molding pressure at the time of heating, after opening for up to 20 minutes. 2. A cooling rate of 0.5 ° C./min or more and 1 ° C./min or less from the start of cooling until the temperature reaches the glass transition temperature of the metal-clad laminate from the start of cooling. The method for producing a metal-clad laminate according to claim 1. 3. The molding plate has a coefficient of linear expansion.
Is 19-25 × 10 ^-6cm / cm ・ ℃
The production of the metal-clad laminate according to claim 1 or claim 2.
Construction method. 4. The metal-clad laminate according to claim 1, wherein the prepreg body has a prepreg disposed outside a circuit board for an inner layer having a circuit formed on a surface thereof. Manufacturing method.