JPH0361357B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a highly reliable multilayer printed board without inner layer voids and with little deviation of inner layer patterns in a short time. Multilayer printed boards are produced by forming a conductive layer pattern on a copper-clad laminate made of epoxy-glass cloth or polyimide-glass cloth by performing etching or other processing, or by forming a conductive layer pattern on a copper-clad laminate made of epoxy-glass cloth or polyimide-glass cloth. The substrate is a laminate such as a laminate with a conductive layer pattern formed by electroless plating, and an adhesive sheet made of these substrates and a prepreg made by impregnating glass cloth with a thermosetting resin to a semi-cured state. Alternately overlap the
It is manufactured by inserting it into a press via a jig plate and heat-pressing it. Although an electrically heated press is also used, a steam press is usually used. One of the drawbacks of the method of manufacturing multilayer printed boards using electric heating or steam heating presses is the problem of warpage of the jig plate. When the jig plate is placed on the hot plate of the heated press,
The surface in contact with the hot platen expands, and the jig plate warps toward the side opposite to the hot platen. Therefore, the multilayer printed board whose upper and lower sides are sandwiched between two jig plates has a bulged center. In order to correct the warpage of this jig plate, extremely high pressure is required, and the
Even a pressure of Kg/cm ² is not sufficient. Therefore,
After heat and pressure bonding, the multilayer printed board will have a slightly different thickness at the center and at the edges. This causes a difference in the thickness of the insulating layer between the inner conductive layers, resulting in poor electrical characteristics such as impedance. Also, if the jig plate is pressurized in a warped state, the pressure in the center will drop more than necessary, so
Inner layer voids are likely to occur. Furthermore, since the pressure applied to the inner layer substrate is non-uniform, abnormal deformation occurs, resulting in misalignment of patterns between layers. These are serious drawbacks for multilayer printed boards. When the pressure is increased to correct the warpage of the jig plate, local deformation of the inner layer substrate increases, and when the pressure is lowered, inner layer voids occur. Therefore, when manufacturing a multilayer printed board with 8 to 10 layers, for example, a board on which a power layer pattern and a ground layer pattern are formed is bonded and
Then, while aligning with this substrate, the substrate with the signal layer pattern formed thereon is secondarily bonded to the outside thereof, or the prepreg and copper foil are secondarily bonded and the signal layer pattern is formed on the copper foil. After that, a method such as tertiary bonding of copper foil and prepreg is used. By doing this, the deviation of the inner layer pattern is made as small as possible. In order for epoxy resin to be completely cured,
130℃~140℃ for 15~20 minutes, then 170℃~180℃
Since heating for 50 to 70 minutes is required, the total time for primary adhesion and secondary adhesion is usually 100 to 120 minutes. The second reason is that this long work time is
And this is the biggest drawback. Polyimide resins and prepregs that cure under the same curing conditions as epoxy resins have recently been commercially available, but they generally require post-curing, which requires two to three times the working time described above. The present invention has been made to improve these drawbacks, and provides a method for manufacturing a highly reliable multilayer printed board in a short time, with no inner layer voids and little interlayer misalignment. To summarize the present invention, the present invention provides a method for producing a multilayer printed board by heating and pressurizing a component obtained by alternately stacking a substrate and an uncured adhesive sheet serving as a prepreg. , a method for manufacturing a multilayer printed board, characterized in that the component is heated under pressure using a pressure device incorporating a microwave oscillation device. That is, in the present invention, when pressing and heating a component made by laminating substrates and adhesive sheets alternately,
Instead of using a conventional electric heating or steam heating pressurizing device, a pressurizing device with a built-in microwave oscillation device is used. Along with this, in order to allow microwaves to penetrate into the component, the position of the microwave-impermeable substrate, such as the substrate on which the power supply layer or the ground layer is formed, should be devised, and the material of the jig plate etc. should be changed. This is the selected one. The wavelength of the microwave oscillation device used in the present invention is 300 MHz to 30000 MHz, preferably around 900 MHz. This configuration example will be explained below with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view showing an example of how components made of a substrate and an adhesive sheet are stacked together in the present invention. In FIG. 1, 1 is a signal layer substrate, 2 is a power layer or earth layer substrate, and 3 is a prepreg. That is, FIG. 1 shows an example in which a microwave-impermeable substrate on which a power supply layer or a ground layer is formed is placed inside. In the present invention, the substrate may be located on the outside of one of the substrates instead of the inside, and in that case, there is no problem because the microwave will penetrate from the opposite side. That is, it is sufficient that the substrate does not occupy both outer sides. Next, FIG. 2 shows an example of the arrangement of this component in an apparatus for pressurizing and heating. FIG. 2 is a longitudinal sectional view showing an example of the arrangement of each member when the component is pressurized and heated according to the present invention. In FIG. 2, 4 is an upper bolster, 5 is a lower bolster, 6 is a microwave oscillator, 7 is a pressure plate, 8 is a component to be pressurized and heated, 9 is a jig plate,
10 indicates a tooth-shaped high frequency leakage prevention plate. In the present invention, what is used as the jig plate 9 needs to be a material that is transparent to microwaves. These materials may be well-known materials that have been used in conventional microwave oscillation devices. Examples of such substances include non-polar polymers such as polyethylene, polystyrene, polyisobutylene, polytetrafluoroethylene, and polypropylene;
There are materials with low dielectric loss, such as quartz, crystalline alumina, and boronitrate glass. The material of the pressure plate 7 that comes into contact with the pressurized object of the pressure device with a built-in microwave oscillator is also a microwave-transparent substance, such as the above-mentioned non-polar polymer,
Or made of a material with low dielectric loss. In this case, the jig plate 9 can also be omitted. The degree to which microwave energy is absorbed by an object and gradually attenuated is expressed by the distance at which the power is halved, that is, the power halving depth D, as shown in equation (1) below. In equation (1), ε ₀ is the vacuum permittivity, μ ₀ is the magnetic permeability, and ω
is the angular velocity and is expressed as ω=2π. tanδ
If ≪1, ε ₀ = 1/4π×9×10 ⁹ (F/m), μ ₀
By substituting =4π×10 ^-7 (H/m) into equation (1), the following equation (2) can be approximately obtained. In equation (2), ε _r is the relative dielectric constant. Since the power half-life depth D is inversely proportional to the product of √ and tanδ, that is, the constant related to dielectric loss, for polytetrafluoroethylene, polyethylene, quartz, etc., when the frequency is 400 MHz or more, D is 300 m or more,
In fact, it can be said that it is almost transparent to microwaves. Therefore, the jig plate 9 and/or the pressure plate 7
It doesn't matter how thick it is. In the present invention, a microwave-transparent material with small dielectric loss may be selected based on the above formula. After pressurizing and heating, the components are depressurized and cooled. The multilayer printed board is then completed by drilling through holes and forming patterns inside and outside the through holes by electroless plating or electroless plating + electrolytic plating. So,
The steps after the through-hole step are omitted, and the board before this step is referred to as a multilayer printed board. The present invention will be illustrated below based on Examples.
The present invention is not limited to these. Example 1 MCL-E608 (registered trademark) manufactured by Hitachi Chemical Co., Ltd. was used as an epoxy-glass cloth copper-clad laminate.
Then, a base material with a thickness of 0.2 mm and a copper foil on both sides with a thickness of 70 μm was processed using an etching method to form patterns for a power layer and a ground layer. Similarly,
A single-sided copper foil laminate MCL-E608 with a base material thickness of 0.2 mm and a copper foil thickness of 70 μm was processed by an etching method to form a signal layer pattern on one side. First, the two substrates 2 with the power layer and earth layer patterns are made of epoxy-glass cloth Bripreg GEA-608N3 (registered trademark) manufactured by Hitachi Chemical Co., Ltd. with a thickness of 0.1 mm.
After sandwiching two sheets of thick material through each other and fixing them with a 0.5 mm thick iron jig plate, they were laminated and bonded using a steam press. In addition, the resin of Buripreg used was 130
The minimum viscosity measured at a constant temperature of 250 poise was 250 poise. The bonding conditions were a pressure of 30 Kg/cm ² and a temperature of 130° C. for 15 minutes, followed by 170° C. for 15 minutes. Then place this thing in the center and each
The substrate 1 with a signal layer pattern formed on one side was placed from both sides through three sheets of Bripreg GEA-608N (minimum viscosity 250 poise at 130°C) with a thickness of 0.1 mm, as shown in Fig. 1. Configure. Next, in accordance with the present invention, this component was fixed with a jig plate 9 made of polytetrafluoroethylene having a thickness of 5 mm, and inserted into a pressurizing device containing a microwave oscillator 6. After that, it was pressurized to 4Kg/cm ² and 915M
Hz microwave was irradiated. After 2 minutes, reduce the pressure to 30
Kg/cm ² , microwave irradiation continued, and irradiation was stopped after a total irradiation time of 15 minutes. At the same time, the pressure was released, and the laminated and bonded component 8 was cooled under pressure at 10 kg/cm ² for 10 minutes together with the jig plate 9 in a water-cooled press. Results will be displayed together. Example 2 A multilayer printed board was manufactured using the same materials and procedures as in Example 1. However, the conditions in the pressurizing device are 4 Kg/cm ² for 2 minutes + 20 Kg/cm ² for 13 minutes. And microwave irradiation is 915MHz for 15 minutes. Example 3 A multilayer printed board was manufactured using the same materials and procedures as in Example 1. However, the conditions for the pressurizing device are 2.
Kg/cm ² for 2 minutes + 10Kg/cm ² for 13 minutes. Example 4 A multilayer printed board was produced using the same copper-clad laminate as in Example 1 and following the same procedure. However, the prepreg resin used when bonding the two substrates with the power layer and earth layer patterns formed using a steam press
The minimum viscosity at 130°C is 250 voids, and when this laminated adhesive product is laminated with a substrate on which a signal layer pattern is formed and pressurized in a pressurizing device by the method described in Example 1, it can be used. The minimum viscosity of the prepared prepreg resin at 130°C is 400 poise. The pressurizing conditions during the 915 MHz microwave irradiation were 2 Kg/cm ² for 2 minutes + 10 Kg/cm ² for 13 minutes. Example 5 The minimum viscosity at 130°C of the prepreg resin used when bonding the substrates on which the power layer and earth layer patterns were formed using a steam press was 250 poise. A multilayer printed board was manufactured under the same conditions as Example 4, except that the prepreg resin used had a minimum viscosity of 80 poise at 130°C when laminated with a substrate and pressurized in a pressurizing device. Example 6 A polyimide-glass cloth copper-clad laminate MCL-I67 (registered trademark) manufactured by Hitachi Chemical Co., Ltd. was used as the substrate material, and a polyimide-glass cloth prepreg GIA-67N manufactured by Hitachi Chemical Co., Ltd. was used as the prepreg material. A multilayer printed board was manufactured in exactly the same manner as in Example 3, except that (registered trademark) was used, except for the viscosity of the prepreg resin, the procedure, and other aspects. In addition,
GIA-67N is a polyimide resin prepreg that cures under the same curing conditions as epoxy resins. Comparative Example 1 A power layer and earth layer pattern board was made using the same materials and methods as in Example 1, and this was used as Example 1.
Laminated and bonded using a steam press using the same prepreg and method. Next, using the same materials and methods as in Example 1, a substrate with a signal layer pattern formed thereon was made, and the laminated adhesive of the power layer and earth layer patterns was bonded to it as in Example 1, as shown in FIG. They were arranged as shown in Figure 1, and unlike the examples of the present invention, they were fixed with a 5 mm thick iron jig plate and heated under pressure using a steam press to produce a multilayer printed board. Pressure conditions were 4 Kg/cm ² for 6 minutes + 30 Kg/cm ² for 85 minutes, and temperature conditions were 130°C for 15 minutes + 170°C for 60 minutes. Thereafter, it was cooled for 10 minutes in the same press. The results will be summarized and displayed later. Comparative Example 2 A multilayer printed board was manufactured using the same materials and the same procedure as Comparative Example 1. However, the pressurization conditions were 4 Kg/cm ² for 6 minutes + 20 Kg/cm ² for 85 minutes. Comparative Example 3 A multilayer printed board was manufactured using the same materials and the same procedure as Comparative Example 3. However, the pressurization conditions were 2 Kg/cm ² for 6 minutes + 10 Kg/cm ² for 85 minutes. Comparative Example 4 A multilayer printed board was manufactured using the same material with exactly the same characteristics as in Example 4, using the same procedure and under the same pressure conditions as in Comparative Example 3. Comparative Example 5 A multilayer printed board was manufactured using the same material with exactly the same characteristics as in Example 5, using the same procedure and under the same pressure conditions as in Comparative Example 3. Comparative Example 6 A multilayer printed board was manufactured using the same material with exactly the same characteristics as in Example 6, using the same procedure and under the same pressure conditions as in Comparative Example 3. The results of each example above are summarized in the table below.

【table】

[Table] Inner layer voids occur or disappear depending on the melt viscosity and pressure of the prepreg resin. In that sense, the comparative example according to the conventional manufacturing method has a melt viscosity that does not generate voids (minimum viscosity at 130℃)
However, in the embodiments of ^{the present invention, voids do not occur not only at high pressures but also at low pressures such as 10 kg/cm 2 .} , the melt viscosity of the prepreg resin can be varied over a wide range without causing voids. This applies not only to epoxy materials but also to polyimide materials. The maximum deviation between layers relative to the drill position when drilling a through hole tends to be larger as the pressure is higher, and the epoxy material shows a larger value than the polyimide material. However, even in that case,
The amount of deviation is smaller in the example of the present invention, and it is recognized that the method of the present invention is a stable method for the inner layer substrate. The most significant effect of the method of the present invention is a reduction in working time. In the comparative example, the total lamination bonding time, including the primary bonding of the substrates on which the power layer and earth layer patterns were formed, was 105 minutes for the epoxy material and 115 minutes for the polyimide material. On the other hand,
In the embodiment of the present invention, 45
50 minutes for polyimide materials. This proves that the work time has been reduced to less than half of the conventional work time. That is, it was demonstrated that the present invention is an excellent method for producing a multilayer printed board.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an example of how components made of a substrate and an adhesive sheet are stacked together in the present invention. FIG. 2 is a longitudinal sectional view showing an example of the arrangement of each member when the component is pressurized and heated according to the present invention. 1: Signal layer board, 2: Power layer or earth layer board, 3: Prepreg, 4: Upper bolster, 5: Lower bolster, 6: Microwave oscillator, 7: Pressure plate, 8: Components to be pressurized and heated , 9: Jig plate, 10: Tooth-shaped high frequency leak prevention plate.

Claims (1)

[Claims] 1. A method for producing a multilayer printed board by pressurizing and heating a component obtained by alternately laminating a substrate and an uncured adhesive sheet called Buri Preg, in which the component is heated. A method for manufacturing a multilayer printed board, characterized in that pressure heating is performed using a pressure device having a built-in microwave oscillation device. 2. The component is made of a microwave-impermeable substrate,
The method for manufacturing a multilayer printed board according to claim 1, wherein the multilayer printed board is configured so as not to occupy both outer sides. 3. The method for manufacturing a multilayer printed board according to claim 1 or 2, wherein the jig plate and/or the pressure plate in the pressure device is made of a microwave-transparent material.