JPH0795628B2 - Method for manufacturing multilayer ceramic printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A method for manufacturing a multilayer ceramic printed circuit board, comprising: forming a via-hole conductor and a circuit conductor on a green sheet formed into a sheet shape; stacking the green sheet; and firing the green sheet. For the purpose of a method for manufacturing a multilayer ceramic printed circuit board in which the shrinkage ratio of the ceramic substrate after firing is controlled within a predetermined range, a reference hole and a via hole are formed in a green sheet formed into a sheet shape, and After forming a conductor layer in the via hole and on the surface of the green sheet, the green sheet is pressure-laminated and then fired to produce a ceramic substrate, wherein the density of the green sheet is 1.42 ± 0.02 g / cm 2. ³
In addition, the pressing force at the time of stacking is set in the range of 200 to 300 kg / cm ³ .

[Field of Industrial Application] The present invention relates to a method for manufacturing a multilayer ceramic printed circuit board.

A multilayer formed by forming via holes in a green sheet containing alumina and glass to be melted as a main component, and press-laminating a printed circuit board forming member in which conductor layers are formed in the via holes and on the green sheet into a multilayer structure and then firing the multilayer structure. The thermal conductivity of the ceramic printed circuit board is almost the same as that of the semiconductor element, and the tab and the chip of the element can be directly mounted,
Higher density mounting is possible, and it is used in printed circuit boards that form electronic circuits for large-scale electronic computers.

[Conventional technology]

A method of manufacturing such a multilayer printed circuit board will be described. As shown in FIG. 5A, alumina and a green sheet forming material 1 such as borosilicate glass powder were mixed with an organic solvent such as acetone. After that, this mixture is stirred and kneaded by using a stirrer 2 such as a ball mill to form a slurry.

Next, as shown in FIG. 5 (b), this slurry-like green sheet forming material is applied to a predetermined thickness on a polyester film using a doctor blade method or the like, and dried in a drying oven to a predetermined thickness. The green sheet 3 having a thickness is formed and processed.

Next, as shown in FIG. 5 (c), a reference hole 4 and a via hole 5 are opened in the molded green sheet 3 using a punching machine.

Next, as shown in FIG. 5D, a via hole conductor 6 is formed by filling the via hole 5 with a conductor made of paste-like copper powder by using a screen printing method.

Further, as shown in FIG. 5 (e), a circuit conductor 7 made of the copper paste having a predetermined circuit pattern is formed on the green sheet by a screen printing method.

Further, as shown in FIG. 5 (f), the green sheet 3 on which the via-hole conductor 6 and the circuit conductor 7 are formed is
The green sheet 3 is laminated while pressurizing the green sheet 3 with a predetermined pressure using a pressure plate 8 in a laminating jig (not shown) as a reference position in the formed reference hole 4.

With the pressure plate removed, pressure is not applied to the green sheet, and the green sheet is fired at a predetermined temperature in a firing furnace 9 as shown in FIG. 5 (g) to form a multilayer ceramic printed circuit board. .

[Problems to be Solved by the Invention]

By the way, when the above-mentioned slurry-like green sheet forming material 1 is kneaded by using the stirrer 2, bubbles are easily generated in the slurry-like green sheet forming material during kneading, and the density of the green sheet formed by the content of the bubbles is high. There are different problems.

When the number of rotations of the stirrer 2 is large and the stirring time (kneading time) is long as shown in FIG. 6 (a), it is formed by the above kneading as shown in FIG. 6 (b). The diameter of the alumina particles 13 is larger than the diameter of the bubbles 12, so that the formed green sheet 3 as shown in FIG. 6 (c).
Density tends to increase.

On the contrary, as shown in FIG. 7 (a), when the rotation speed of the stirrer 2 is small and the stirring time (kneading time) is short,
The diameter of the alumina particles 13 is smaller than the diameter of the bubbles 12 as shown in FIG. 7 (b), and the density of the green sheet 3 tends to be smaller as shown in FIG. 7 (c).

When the densities of the green sheets are different as described above, there is a problem that the shrinkage ratio between the green sheet before firing and the green sheet after firing does not become a constant value. Therefore, when a via hole is formed on a green sheet by using a punching machine and then fired, there is a problem that the position of the via hole after firing does not reach the predetermined designed position. There is a problem that a highly reliable multi-layer ceramic substrate cannot be obtained due to displacement or the like.

It is an object of the present invention to eliminate the above-mentioned problems and provide a method for manufacturing a multilayer ceramic printed circuit board in which a green sheet before firing has a predetermined shrinkage rate when it becomes a ceramic substrate after firing. .

[Means for Solving the Problems]

The method for producing a multilayer printed circuit board of the present invention to achieve the above object, a reference hole in a green sheet formed into a sheet, and after opening a via hole, after forming a conductor layer in the via hole and the green sheet surface, the green In the method of manufacturing a ceramic substrate by pressure-laminating sheets and firing, the density of the green sheet is 1.42 ± 0.02 g / cm ³
Further, the pressing force at the time of stacking is set in the range of 200 to 300 Kg / cm ³ .

[Work]

When kneading the green sheet forming material, it was experimentally confirmed that the amount of bubbles generated depends on the rotation speed of the stirrer for kneading the green sheet forming material and the kneading time. It is possible to form a green sheet having a density such that the generation of bubbles is suppressed within a certain range by keeping it at a predetermined value, and thereby the shrinkage rate of the green sheet before and after firing falls within a certain range. it can.

In addition, the pressure applied when stacking the green sheets and the variation in shrinkage of the green sheets before and after firing were experimentally investigated,
By controlling the pressing force during lamination within a predetermined range based on this value, the shrinkage rate of the green sheet can be kept within a predetermined range.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

Table 1 shows the number of revolutions of the stirrer for kneading and stirring the green sheet forming material used in the method of the present invention, the stirring time, the density of the green sheet to be formed, and the before and after firing of this green sheet. The relationship of shrinkage is shown.

As shown in Table 1, the density of the green sheet tends to decrease as the rotation speed and rotation time of the stirrer are increased.

This means that the particles of alumina of the green sheet forming material become finer as they are agitated, and the ratio of the diameter of the alumina to the diameter of the bubbles entering the kneaded green sheet becomes smaller when the agitating time and the rotating speed of the agitator are reduced. It is considered that this is smaller than

Further, FIG. 1 shows a relationship diagram between the density and the shrinkage rate of the green sheet.

As a result of experiments, the inventors of the present invention showed that when the density of the green sheet was 1.40 or less, the shrinkage rate during firing was 17.5% or more, disconnection of the inner layer pattern was generated, and the density of the green sheet was 1.44 or more, The ceramic substrate after firing has cracks, cracks, and peeling of the conductor layer. From this, it was confirmed that if the shrinkage ratio is set within a predetermined range, the density of the green sheet should be set within the range of 1.42 ± 0.02.

FIG. 2 shows the relationship between the density of the green sheet and the amount of bubbles, and FIG. 3 shows the relationship between the rotational speed of the ball mill and the amount of bubbles in the green sheet.

From Fig.2, in order to make the density of the green sheet 1.42 ± 0.02, it is necessary to set the bubble amount to 28-30%.
In order to achieve 28 to 30%, it is necessary to set to 32 to 50 RPM when the stirring time is 12 hours as shown in Fig. 3. By adjusting the rotation speed of the ball mill and the stirring time, the required density can be obtained. A green sheet is obtained.

Further, the green sheet having the density of 1.42 ± 0.02 thus formed is temporarily pressure-laminated with the pressure plate 8 as shown in FIG. 5 (f), and then the pressure is stopped and the green sheet is fired. The pressure applied to the pressure plate 8 during the pressure lamination and the shrinkage ratio between the laminated green sheet and the fired green sheet (the rate of shrinkage in the length direction before and after firing of the green sheet is%.
4) is shown in FIG.

As shown in the figure, the minimum shrinkage is 17.5% and the maximum shrinkage is 17.8% when the applied pressure is 200 kg / cm ² . Pressing force 300K
In the case of g / cm ² , the maximum contraction rate of the sample is 17.2% and the minimum contraction rate is 16.9%, so the fluctuation range of the contraction rate is 17.8-1.
6.9 = 0.9%, which means that it will fluctuate by about 0.9 mm for a size of 100 mm, which is sufficiently practical.

The relationship between the stacking pressure and the shrinkage ratio was tested using a green sheet having a density of 1.42 ± 0.02, but similar results can be obtained by using a green sheet having a density within the range of the present invention. .

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the shrinkage rate before and after firing of the green sheet can be controlled and suppressed to a predetermined value, so that a via hole or the like having a dimension corresponding to this shrinkage rate can be formed. Designing a punching jig or the like having an opening has an effect of obtaining a multilayer ceramic substrate having a desired via hole pattern with highly accurate dimensions.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the green sheet density and shrinkage in the method of the present invention, FIG. 2 is a diagram showing the relationship between the density of the green sheet and the amount of bubbles, and FIG. 3 is the number of revolutions of the ball mill and the amount of bubbles. FIG. 4 is a relationship diagram between the stacking pressure and the shrinkage ratio, a relationship diagram between the conductor thickness and the viscosity of the conductor layer forming material in the present invention, FIG. 5 (a) to FIG. 5 (g) Up to FIG. 6 (a) to FIG. 6 (c), a state diagram of a green sheet kneaded at multiple rotation speeds and a long kneading time, and from FIG. 7 (a). Up to FIG. 7 (c), a state diagram of a green sheet kneaded at a low rotation speed and a short kneading time is shown. In the figure, 1 is a green sheet forming material, 2 is a stirrer, 3 is a green sheet, 4 is a reference hole, 5 is a via hole, 6 is a via hole conductor, 7 is a circuit conductor, 8 is a pressure plate, 9 is a firing furnace, 12 Indicates bubbles and 13 indicates alumina particles.

Claims (2)

[Claims] 1. A green sheet (3) formed into a sheet.
After opening the reference hole (4) and the via hole (5) in the above, after forming the conductor layer (6, 7) in the via hole and on the surface of the green sheet, the green sheet is laminated while being pressed, and then fired. A method for producing a ceramic substrate, wherein the green sheet has a sheet density of 1.42 ± 0.02 g / cm ³ . ^2. The method for manufacturing a multilayer ceramic printed circuit board according to claim 1, wherein the pressure applied when the green sheets (3) are laminated is in the range of 200 to 300 kg / cm ² .