JP3364145B2 - Manufacturing method of multilayer printed wiring board - Google Patents

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 multilayer printed wiring board.

[0002]

2. Description of the Related Art A multilayer printed wiring board is manufactured by stacking a plurality of inner layer circuit boards and prepregs, stacking metal foils such as copper foils on both surfaces thereof, and heating and pressurizing them to form a laminate. In carrying out the above-mentioned lamination molding, it is general to carry out a so-called multi-stage hot press, in which the combination material in which the inner layer circuit board, the prepreg and the metal foil are laminated is stacked in a multi-stage, and this is set between hot plates and pressed. is there.

However, in a multi-stage hot press using a heating plate, the heating temperature is different between the combination material close to the heating plate and the combination material far from the heating plate, and the heating temperature is non-uniform. The quality of the multilayer printed wiring board may vary. Therefore, in the multi-stage hot press, the number of stages of the combination material that can be stacked is limited.

In the field of manufacturing laminated sheets, a new technique has been developed in consideration of such a problem. It is a method in which a power source is connected to all the metal foils and the metal foil is energized to heat the metal foil to heat a laminate such as a prepreg (Japanese Patent Publication No. 7-508940). . FIG. 1 shows an example thereof, in which two long metal foils 2 are used, and a laminated body in which a prepreg 1 and an inner circuit board 3 are stacked between the two metal foils 2 is used as a metal foil 2. A long combination material 4 composed of a prepreg 1, an inner layer circuit board 3, and upper and lower metal foils 2 by sandwiching a plurality in the longitudinal direction of the
To form. This long combination material 4 is bent in a meandering shape, and an insulating mirror plate 5 is inserted between the bent portions,
The laminated body of the prepreg 1 and the inner circuit board 3 is sandwiched by the metal foils 2 and stacked in multiple stages. Then, this is set between the pressure plates 6, the power source 7 is connected to the metal foil 2,
When the metal foil 2 is energized while cold pressing with the pressure plate 6, the metal foil 2 generates heat due to Joule heat, and this heat generation heats the laminate of the prepreg 1 and the inner layer circuit board 3 while
This is a method of performing pressure molding.

According to this method, since the laminated body of each stage can be directly heated by using the metal foil 2 as a heat source, each prepreg 1 of the laminated body laminated in multiple stages can be remarkably uniformly heated. Therefore, the multilayer printed wiring board can be obtained by multistage molding without variation in quality. This direct heating method is an excellent method in principle as a uniform heating method, but it is still insufficient in view of variations in appearance, moldability, resin flow, and product temperature.

[0006]

Therefore, an object of the present invention is to obtain satisfactory results in appearance, moldability, resin flow, and product temperature variation when manufacturing a multilayer printed wiring board by a direct heating method. It is to provide a method for manufacturing a multilayer printed wiring board.

[0007]

Means for Solving the Problems The present inventor has reached various points of the present invention through various studies and experiments in order to solve the above problems by finding optimum conditions for a heating method. That is, the method for manufacturing a multilayer printed wiring board according to the present invention, the inner layer circuit board and the prepreg by bending a long combination material sandwiching the laminate of the inner layer circuit board and the prepreg with a long metal foil. The laminated body is stacked in multiple stages in a state of being sandwiched by metal foils, and while heating the laminated body by energizing the metal foils to generate heat in the metal foils, by press molding, the inner layer circuit board and the prepreg are formed. In a method for obtaining a multilayer printed wiring board by laminating and integrating a metal foil, the temperature rising rate at the time of heating the laminate is 8 to 10 ° C / until the internal temperature of the laminate reaches 90 ° C.
1.5 to 2.5 minutes from 90 ℃ to 140 ℃
℃ / min, and 5 from 140 ℃ to 180 ℃
It is characterized in that it is adjusted to be ~ 7 ° C / min.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION First, preferred prepregs used in the method of the present invention will be described in detail below.
The prepreg may be a normal prepreg, that is, paper, cloth, glass woven cloth, non-woven cloth, etc. impregnated with epoxy resin or phenol resin, but for the following reasons, this prepreg is more suitable for this direct heating method. Is a glass cloth base material impregnated with an epoxy resin.
A prepreg having a melt viscosity at 0 ° C. of 1500 to 50,000 poises. In this prepreg, the melt viscosity of the epoxy resin at 130 ° C. is more preferably 4000-10000 poise. Melt viscosity of epoxy resin in prepreg at 130 ℃ is 1500 (4000)
If it is less than poise, the flow of resin at the time of molding becomes too large, and there is a possibility that molding defects such as variations in plate thickness, scrapes at the end of the product, and measling will occur. Conversely, the melt viscosity of the epoxy resin in the prepreg at 130 ° C is 5000.
When it exceeds 0 (10000) poise, the resin flow during molding is poor, and voids may occur between the surface of the inner layer circuit board and the insulating layer formed by the prepreg when laminating the inner layer circuit board. In addition, the measurement of the melt viscosity is performed by the prepreg 1
Approximately 2 g of resin powder separated from the glass cloth base material is rubbed and made into a cylindrical pipette, and a 0.5 mmφ nozzle is used by a Shimadzu Corporation advanced flow tester “CFT-100”. Pressure 3-40kg
It can be performed by measuring the viscosity at a temperature of 130 ° C. under the condition of / cm 2.

In the conventional multi-step hot pressing method,
Since the heating temperature for the prepregs in each stage becomes non-uniform, a prepreg is devised so that the failure occurrence rate is reduced with respect to the non-uniform heating temperature. But,
In the method of heating by energizing the metal foil to generate heat, the heating temperature for the prepreg in each stage becomes uniform.Therefore, if the prepreg that has been conventionally used is used as it is, the flow of resin becomes rather large. As a result, there is a risk of variations in the thickness of the product between the center and the edge of the product, or defective molding such as scraping or measling at the edge of the product. Therefore, the above-mentioned prepreg was developed by the present applicant. By using this new prepreg, variations in plate thickness, scrapes on the product edge,
The multilayer printed wiring board can be manufactured by the direct heating method without the problem of molding defects such as measling.

The novel prepreg is prepared by impregnating a glass cloth base material made of a woven or non-woven cloth of glass fiber with an epoxy resin varnish and drying it to form a glass cloth base material with B
It is prepared as containing an epoxy resin semi-cured in a stage state. The prepreg is preferably impregnated with an epoxy resin so that the resin content is in the range of 40 to 70% by weight.

A multi-layer printed wiring board can be manufactured by the method shown in FIG. 1 by using the prepreg 1 whose melt viscosity is adjusted as described above. That is, two long metal foils 2 such as copper foil are used, and between the two metal foils 2,
By sandwiching a plurality of laminates of the prepreg 1 and the inner layer circuit board 3 in the longitudinal direction of the metal foil 2, a long combination material 4 composed of the prepreg 1, the inner layer circuit board 3 and the upper and lower metal foils 2 is formed. The long combination material 4 is bent in a meandering shape via the insulating mirror surface plate 5 to stack the stacked bodies in multiple stages. Then, after setting this between the pressure plates 6, the power source 7 is connected to each of the two metal foils 2,
While cold pressing with the pressure plate 6, the metal foil 2 is energized to directly heat the stacked body of each stage. In this way, the laminated body of each stage and the metal foil are pressure-molded to be laminated and integrated.

Here, during molding, the temperature rising rate at the time of heating the laminate is 8 to 10 ° C./minute until the internal temperature of the laminate reaches 90 ° C., or from 90 ° C. to 140 ° C. 1.5-2.5 ° C / min, and 140 ° C to 180
The temperature is adjusted to reach 5 to 7 ° C / minute until the temperature reaches 0 ° C.
Preferably, the maximum current amount during energization is adjusted to a set temperature rising rate (° C./min)×a laminate area (cm ² ) × 0.020. The pressure molding is performed under a vacuum of 100 torr or less. No pressure is applied to the stack until a vacuum of 100 torr is reached. Moreover, the pressure at the time of the pressure molding is 1 kg / cm ² or less until the internal temperature of the laminate reaches 110 ° C., and 8 to 15 kg after that.
It is adjusted to / cm ² . As described above, by performing the pressure molding in the vacuum chamber under reduced pressure conditions, it becomes easy to obtain a voidless product.

In the above-mentioned molding, since the metal foil 3 is heated by energizing the metal foil 3 to generate heat, the prepreg 1 in each stage can be directly heated using the metal foil 2 as a heat source, and the prepreg 1 is stacked in multiple stages. The prepreg 1 of the laminated body can be uniformly heated, and the multilayer printed wiring board can be formed without quality variations.

When a prepreg in which the melt viscosity of the impregnated epoxy resin at 130 ° C. is 1500 to 50000 poise is used as the prepreg 1, the flow of the resin at the time of molding is optimized, and variations in plate thickness and products are achieved. A multilayer printed wiring board can be molded without defective molding such as scraping of edges and measling.

[0015]

EXAMPLES Next, the present invention will be specifically described by way of examples. (Preparation of epoxy resin varnish) Brominated epoxy resin ("YDB500K EK80" manufactured by Tohto Kasei Co., Ltd.) 90.
0 parts by weight, novolac type epoxy resin ("YDCN220 EK75" manufactured by Tohto Kasei Co., Ltd.) 10.0 parts by weight, dicyandiamide ("DICY" manufactured by Nippon Carpide Co., Ltd.) 2.
0 parts by weight, dimethylformamide 10.0 parts by weight, 2-
Ethyl-4 methyl imidazole ("2E4" manufactured by Shikoku Kasei Co., Ltd.
MZ ") 0.2 parts by weight of the formulation was dissolved in methyl ethyl ketone to prepare an epoxy resin varnish having a concentration of 60% by weight.

(Example 1) WEA116E manufactured by Nitto Boseki Co., Ltd.
Type epoxy resin varnish is impregnated into a glass cloth base material of a type to a resin content of 48% by weight and dried in a dryer at a temperature of 170 ° C. for 150 seconds to give a thickness of 0.
A long prepreg 1 having a melt viscosity at 10 mm and 130 ° C. of 1500 poise was obtained.

Next, the prepreg 1 was formed on both sides of the inner layer circuit board 3 which was prepared by providing inner layer circuits 3a with copper foil having a thickness of 35 μm on both sides of an epoxy resin laminated plate having an area of 510 mm × 340 mm and a thickness of 1.10 mm. Two sheets each were stacked and sandwiched between two long metal foils 2 formed of a copper foil having a thickness of 18 μm to prepare a long combination material 4 having a laminated structure as shown in FIG. Then, this long combination material 4 is bent in a meandering manner through the mirror surface plate 5 so that the laminated body of the prepreg 1 and the inner layer circuit board 3 is superposed in multiple stages, and this is combined with the pressure plate as shown in FIG. 6 and the power source 7 was connected to the metal foil 2.

After that, heat and pressure molding was performed by heating utilizing the heat generation of the metal foil 2 and pressing by the pressure plate 6. As the molding condition, the vacuum pressure in the press is 100
No pressure applied until Torr, then energization starts,
The temperature was raised at 9 ° C / minute until the product temperature reached 90 ° C.
The maximum current value (A) to be applied at that time is 312 A, and 9
After reaching 0 ° C., the temperature was raised at 2.0 ° C./minute until reaching 140 ° C. The maximum current value (A) that can be applied at that time is 70A
Met. After reaching 140 ° C, the temperature was raised at 6 ° C / min until reaching 180 ° C. At that time, the maximum current value (A) to be energized is set to 208 A to heat and raise the temperature of the product to 110
Pressurized at 1 kg / cm ² until reaching ℃, then 10
The pressure was applied at kg / cm ² to obtain a 4-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 1. (Example 2) The materials used and the molding method are the same as in Example 1,
No pressure was applied until the vacuum pressure in the press reached 50 Torr, then energization was started, and a four-layer printed wiring board was obtained under the same conditions as in Example 1 for temperature increase and pressure increase after temperature increase. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 1. (Example 3) The materials used and the molding method are the same as in Example 1,
No pressure was applied until the vacuum pressure in the press reached 100 Torr, then energization was started, and the temperature was raised at 8 ° C / minute until the product temperature reached 90 ° C. At that time, the maximum current value (A) to be energized was 277 A, and after reaching 90 ° C., the temperature was raised at 1.5 ° C./min until reaching 140 ° C. At that time, the maximum current value (A) to be energized was 52A. After reaching 140 ° C, the temperature was raised at 5 ° C / min until reaching 180 ° C. At that time, the maximum current value (A) to be energized is set to 173 A, the temperature is raised by heating, and 1 kg / cm ^{2 is} required until the product temperature reaches 110 ° C.
And then 10 kg / cm ² to obtain a four-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 1. (Example 4) The materials used and the molding method are the same as in Example 1,
No pressure was applied until the vacuum pressure in the press reached 100 Torr, then energization was started, and the temperature was raised at 10 ° C / minute until the product temperature reached 90 ° C. At that time, the maximum current value (A) to be energized was 347 A, and after reaching 90 ° C., the temperature was raised at 2.5 ° C./min until reaching 140 ° C. At that time, the maximum current value (A) to be energized is set to 87 A and heated to 140 ° C
The temperature was raised at 7 ° C / min until the temperature reached 180 ° C. At that time, the maximum current value (A) to be energized is set to 243 A, the temperature is increased by heating, and 1 kg until the product temperature reaches 110 ° C.
/ Cm ² and then 10 kg / cm ² to obtain a 4-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 1. (Example 5) The materials used, the molding method, and the heating temperature are the same as those in Example 1.
Same as above, 1kg / until the product temperature reaches 110 ℃
The pressure was applied at cm ² and thereafter at 8 kg / cm ² , to obtain a 4-layer printed wiring board. The characteristics of the obtained 4-layer printed wiring board are shown in Table 1. (Example 6) The materials used, the molding method, and the heating temperature were set in Example 1.
Same as above, 1kg / until the product temperature reaches 110 ℃
The pressure was applied at cm ² and thereafter at 15 kg / cm ² , to obtain a 4-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 1.

[0019]

[Table 1]

(Comparative Example 1) The material used and the molding method are the same as in Example 1, no pressure was applied until the vacuum pressure in the press reached 150 Torr, and then energization was started to bring the product temperature to 90 ° C. The temperature was raised to 9 ° C./minute until the temperature reached. At that time, the maximum current value (A) to be energized is 312 A, after reaching 90 ° C,
The temperature was raised at 2.0 ° C / minute until the temperature reached 140 ° C. At that time, the maximum current value (A) to be energized is set to 70 A, the temperature is raised by heating, and after reaching 140 ° C., it is 6 ° C. until reaching 180 ° C.
The temperature was raised at a rate of / minute. The maximum current value (A) to be applied at that time is 2
The temperature is raised to 08 A, the temperature is raised, and pressure is applied at 1 kg / cm ² until the product temperature reaches 110 ° C., then 10 kg / cm ²
Then, pressure was applied to obtain a 4-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2. (Comparative Example 2) The materials used and the molding method are the same as in Example 1,
No pressure was applied until the vacuum pressure in the press reached 100 Torr, then energization was started, and the temperature was raised at 7 ° C / minute until the product temperature reached 90 ° C. At that time, the maximum current value (A) to be energized was 243 A, and after reaching 90 ° C., the temperature was raised at 1.0 ° C./min until reaching 140 ° C. At that time, the maximum current value (A) to be energized was set to 35 A to heat and raise the temperature, and after reaching 140 ° C., the temperature was raised at 4 ° C./min until reaching 180 ° C. At that time, the maximum current value (A) to be energized is set to 139A to heat up the temperature, and 1kg until the product temperature reaches 110 ° C.
/ Cm ² and then 10 kg / cm ² to obtain a 4-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2. (Comparative Example 3) The materials used and the molding method are the same as in Example 1,
No pressure was applied until the vacuum pressure in the press reached 100 Torr, then energization was started, and the temperature was raised at 11 ° C / minute until the product temperature reached 90 ° C. At that time, the maximum current value (A) to be energized was 381 A, and after reaching 90 ° C., the temperature was raised at 3.0 ° C./min until reaching 140 ° C. At that time, the maximum current value (A) to be energized is set to 104 A and the temperature is raised by heating to 140
After reaching 180 ° C., the temperature was raised at 8 ° C./min until reaching 180 ° C. At that time, the maximum current value (A) to be energized is set to 277 A to heat and raise the temperature, and 1 k is required until the product temperature reaches 110 ° C.
Pressurize at g / cm ² , then press at 10 kg / cm ² 4
A layer printed wiring board was obtained. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2. (Comparative Example 4) The maximum current value (A) to be energized at the time of temperature rise is uniformly 1
000 A and all other conditions were the same as in Example 1 to obtain a 4-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2. (Comparative Example 5) The materials used and the molding method are the same as in Example 1,
1kg before the vacuum pressure in the press reaches 100 Torr
/ Cm ² pressurized, the Atsushi Nobori caused by the subsequent energizing Example 1
10k after the product temperature reaches 110 ℃
A pressure of g / cm ² was applied to obtain a 4-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2. (Comparative Example 6) The materials used and the molding method are the same as in Example 1,
10k before the vacuum pressure in the press reaches 100 Torr
The pressure was increased to g / cm ² and then the same heating as in Example 1 was performed to obtain a four-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2. (Comparative Example 7) The materials used and the molding method are the same as in Example 1,
1kg before the vacuum pressure in the press reaches 100 Torr
/ Cm ² and then 20 kg / cm ²
A layer printed wiring board was obtained. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2. (Conventional example) The material used and the molding method are the same as in Example 1, and pressure is applied at 1 kg / cm ² at the same time when the vacuum in the press is started, and then pressure is applied at 10 kg / cm ² at the same time as the start of temperature rise due to energization. 3 ℃ / mi until the temperature reaches 180 ℃
The temperature was raised at n and the pressure was applied to obtain a four-layer printed wiring board. The quality characteristics of the obtained 4-layer printed wiring board are shown in Table 2.

[0021]

[Table 2]

As shown in Table 1, according to the manufacturing method of the present invention, a four-layer printed wiring board having excellent appearance, moldability, resin flow and product temperature variation can be obtained by molding in a short time.

[0023]

According to the method for manufacturing a multilayer printed wiring board according to the present invention, it is possible to obtain a multilayer printed wiring board which gives satisfactory results in appearance, moldability, resin flow, and product temperature variation.

[Brief description of drawings]

FIG. 1 is a schematic front view showing an example of an embodiment of the present invention.

FIG. 2 is a schematic front view showing a laminated structure of a prepreg, a metal foil and the like.

[Explanation of symbols]

1 prepreg 2 metal foil 3 inner layer circuit board 3a inner layer circuit 4 combined materials 5 mirror plate 6 Pressure plate 7 power supply

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H05K 3/46 H05K 3/46 B // B29K 105: 08 B29K 105: 08 B29L 31:34 B29L 31:34 (58) Field (Int.Cl. ⁷ , DB name) B29C 43/00-43/58 B32B 15 / 08,31 / 20

Claims (5)

(57) [Claims] 1. A laminate comprising an inner layer circuit board and a prepreg sandwiched between elongated metal foils is bent so that the laminate of the inner layer circuit board and prepreg is sandwiched between the metal foils. While stacking in multiple stages, while heating the laminate by heating the metal foil by energizing the metal foil,
In the method for obtaining a multilayer printed wiring board by laminating and integrating the inner layer circuit board, the prepreg, and the metal foil by pressure molding, the temperature rising rate at the time of heating the laminate is 8 ~ until the temperature reaches 90 ℃
10 ℃ / min, 1.5 to 90 ℃ to 140 ℃
A method for producing a multilayer printed wiring board, which comprises adjusting the temperature to be 2.5 ° C./min, and from 140 ° C. to 180 ° C. to be 5 to 7 ° C./min. 2. The multilayer printed wiring board according to claim 1, wherein the maximum current amount when energized is adjusted to a set temperature rising rate (° C./min)×a laminate area (cm ² ) × 0.020. Production method. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the pressure molding is performed under a vacuum of 100 torr or less. 4. Until a vacuum of 100 torr is reached,
The method for manufacturing a multilayer printed wiring board according to claim 3, wherein pressure is not applied to the laminate. The pressure during wherein said pressing, the laminate 1 kg / cm ² until the internal temperature reached 110 ° C. below, adjusting the subsequent to 8~15kg / cm ^2, claim 1 4. The method for manufacturing a multilayer printed wiring board according to any one of 1 to 3.