JPH0131320B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer ceramic substrate. In particular, it relates to an improved method for solving problems caused by directional shrinkage of green sheets.

The common method of manufacturing multilayer ceramic substrates is
First, the ceramic material is formed into a flexible tape (green sheet) (casting).
Punch out a suitable size such as 200mm x 200mm square. At the same time as the green sheet is punched, positioning guide holes are also punched out. At this time, the punched green sheet is oriented in the casting direction due to the positional relationship between the punching device and the casting device. Using a guide hole as a positioning axis, holes are punched or drilled at the required positions in a green sheet punched to the required size, and a circuit pattern is printed using conductive paste of a high-melting point metal such as tungsten or molybdenum. At this time, the drilled holes are filled with conductive paste, forming electrical paths between the top and bottom of the green sheet. Then, a plurality of green sheets on which various circuit patterns are printed in this manner are aligned with guide holes, stacked, and pressed under appropriate pressure and temperature. The stacked green sheets are cut into the final shape of the multilayer ceramic substrate and then proceed to the sintering process. Sintering consists of two stages, the first stage is
The organic binder of the green sheet is thermally removed in an oxidizing atmosphere at 500-700℃, and the second stage is at 1500-1600℃.
Alumina and conductive materials such as tungsten or molybdenum are sintered in a cyclic atmosphere at ℃.
During this sintering, shrinkage occurs due to ceramic grain growth and organic binder scattering. This shrinkage rate varies depending on the composition of the ceramic raw material, particle size, amount of binder, or sintering conditions, but is generally around 15%. Therefore,
The circuit pattern and external cutting dimensions printed on the green sheet must be corrected to be larger by this shrinkage.

One of the problems in manufacturing multilayer ceramic substrates has been the fact that the shrinkage rate is different between the casting direction of the green sheet and the direction perpendicular to it. The reason for this is that multilayer ceramic substrates have become larger and more dense, and the difference in shrinkage rate depending on the direction, which was not considered a problem in the past, has become impossible to ignore. Shrinkage of green sheets occurs not only during sintering, but also due to drying during sheet storage before and after printing. The drying shrinkage rate during sheet storage before and after printing and the shrinkage rate during sintering differ by about 0.1 to 0.8% between the casting direction of the green sheet and the direction perpendicular to it. For this reason, there is a problem in that the dimensional accuracy of ceramic substrates larger than a certain size deteriorates to a degree that cannot be ignored, making post-processes such as lead attachment difficult. The difference in drying shrinkage rate depending on the direction varies greatly, ranging from 0.1 to 0.8%, so the accuracy of positional misalignment between the upper and lower layers during lamination (lamination accuracy) deteriorates, causing problems such as disconnection and shorting of wiring. be.

One solution to these problems is to correct the circuit pattern to be printed and the external cut dimensions by changing the dimensional ratio in the casting direction of the green sheet and in the direction perpendicular to it. However, in this method, the correction rate varies depending on casting conditions, sheet storage conditions, etc., and the correction is also time-consuming and extremely difficult.

An object of the present invention is to provide a method for manufacturing a multilayer ceramic substrate with high dimensional accuracy by eliminating the directivity of shrinkage rate.

The present invention is characterized in that a plurality of green sheets are stacked so that their casting directions are substantially perpendicular to each other, and then sintered. According to this, the green sheets are stacked so that their casting directions are substantially orthogonal, so that the directionality of the shrinkage rate can be eliminated.

Further, according to a specific embodiment of the present invention, the method for manufacturing a multilayer ceramic substrate includes casting a green sheet, printing a circuit pattern on the green sheet, and rolling a plurality of green sheets with the circuit patterns printed thereon in the casting direction. The green sheets are stacked so that they are substantially perpendicular to each other, and the stacked green sheets are sintered. According to this specific example, the directionality of the sintering shrinkage rate can be particularly eliminated.

According to another embodiment of the present invention, the manufacturing method includes casting green sheets, stacking the plurality of green sheets so that their casting directions are substantially orthogonal, and patterning a circuit on the stacked green sheets. The circuit pattern is printed, the laminated green sheets printed with this circuit pattern are further laminated, and this is sintered.
According to this, in particular, it is possible to eliminate the directionality of the drying shrinkage rate of the green sheet and to reduce its variation. Of course, it is also possible to eliminate the directionality of the sintering shrinkage rate.

The present invention will be explained below with reference to the drawings.

1 and 2 are diagrams for explaining one embodiment of the present invention, in which FIG. 1 is a diagram schematically showing the steps from casting to sintering of a green sheet, and FIG. The figure shows the state of the green sheet at each step in FIG. 1.

The casting device 1 is made of alumina, talc,
A ceramic raw material mixture 2 in which clay, binder, and organic filler are thoroughly mixed and dispersed using a ball mill or the like is stored inside the blade 3. The casting device 1 moves the carrier tape 4 to draw out the mixed liquid in the form of a sheet from the gap between the blade 3 and the carrier tape 4 using the doctor blade method so that it has a uniform thickness on the carrier tape 4, and then dries it in a drying oven 5. Let it harden. The cured green sheet 14 is peeled off from the carrier tape 4, and a molded green sheet 15 is formed from the continuous green sheet 14 using a guide hole/outline punching machine 6. In this process,
As shown in FIG. 2a, guide holes 20 for positioning are punched out in the green sheet 15 after the molding, and a casting direction mark 21 indicating the casting direction is marked.

Next, the required holes 22 are punched in the green sheet 15 after the molding using the punching machine 7. Figure 2b
As shown in the figure, the green sheet 23 for the X layer and the Y
Holes are made at positions where the casting direction marks 21 are perpendicular to each other so as to create a layer green sheet 24. This is an important point of the present invention, as will be understood from the description that follows.

After drilling, a desired circuit pattern 25 is printed on the green sheet 16 by a printing machine 8 using a conductive paste. Green sheet 17 after printing as shown in Figure 2c
However, in this step as well, the X-layer green sheet 23 and the Y-layer green sheet 24 are printed at positions where the casting direction marks are perpendicular to each other.

The green sheets 17 after printing are stacked and pressed using a lamination press 9 at an appropriate temperature and pressure. FIG. 2d shows the stacked green sheets 18, and the green sheets 18 are stacked so that the casting direction marks 21 of the printed green sheets 17 are perpendicular to each other. Of course, the casting direction mark 21
Since the green sheets 23 for the X layer and the Y layer are printed so that they are at right angles to each other,
The positional relationship is such that the circuit pattern of the layer green sheet 24 is compatible.

The green sheet 18 after lamination is cut out by an external shape punching machine 1
The green sheet 19 is punched out to the required external dimensions using a cutting method 0 and cut to the external shape as shown in FIG. 2e. After cutting the outer shape, the green sheet 19 is put into the sintering furnace 11. The sintering furnace 11 has a two-chamber structure: a front chamber 12 and a rear chamber 13. In the front chamber 12, the temperature ranges from room temperature to 700°C.
The temperature is appropriately controlled in an oxidizing atmosphere to heat remove the organic binder, and the temperature is raised from 700℃ to 1600℃ in the rear chamber 13, and then to room temperature, the ring element is heated to prevent conductive materials such as tungsten or molybdenum from being oxidized and lost. Appropriate temperature control in the atmosphere,
Co-sintering alumina and conductor material.

According to this example, since the green sheets are stacked and sintered so that their casting directions are perpendicular to each other, the shrinkage rate after lamination, in this example, the sintering shrinkage rate is independent of the casting direction. The shrinkage rate of the multilayer ceramic substrate is the same in both the vertical and horizontal directions. This is because the green sheets are stacked so that their casting directions are perpendicular to each other, so the shrinkage of the green sheets interacts with that of other green sheets that are in contact with each other and whose casting directions are different, thereby eliminating the directivity of the shrinkage rate.

In the embodiments shown in FIGS. 1 and 2, a total of two green sheets 23 and one green sheet 24, whose casting direction is in the X direction and one in the Y direction, respectively, are used.
Although the green sheets are stacked and laminated, the present invention is not limited to this, and the present invention can also be applied to the case where a large number of green sheets are laminated. That is, X-direction green sheets and Y-direction green sheets are stacked alternately,
It is also possible to have four or more. Furthermore, it is not necessary to stack the sheets alternately in the X direction and the Y direction. For example, substantially the same effect can be obtained by stacking two sheets alternately in the X direction, X direction, Y direction, and Y direction from above in the casting direction.

3 and 4 are diagrams for explaining other embodiments of the present invention, and FIG. 3 is a diagram schematically showing the steps from casting to sintering of a green sheet. FIG. 4 is a diagram showing the state of the green sheet in each step of FIG. 3.

The casting device 31 is similar to the casting device 1 shown in FIG.
Ceramic raw material mixture 32 stored inside 3
is drawn out into a sheet shape with a uniform thickness onto a carrier tape 34 using a doctor blade method, and dried and hardened in a drying oven 35. The cured green sheet 44 is peeled off from the carrier tape 34, and a green sheet 45 is cut out from the continuous green sheet 44 using a guide hole/outline punching machine 36. The molded green sheet 45 is shown in Figure 4a.
As shown in , a guide hole 51 for positioning is punched out and a casting direction mark 52 indicating the casting direction is marked.

After making the mold, the green sheet 45 is placed 2 so that the casting direction marks 52 are perpendicular to each other.
The sheets are stacked and pressed using a two-sheet press 37 under appropriate pressure and temperature. After pressing the two sheets, the green sheet 46 is shown in FIG. 4b.

After pressing two sheets, the required holes 55 are punched in the green sheet 46 using a punching machine 38. After drilling, the green sheet 47 includes a green sheet 53 for the X layer and a green sheet 5 for the Y layer, as shown in FIG. 4c.
4, and the casting direction mark 52 is bored at the same position. However, the 2 shown in Figure 4b
Since the sheets are laminated in the sheet pressing process so that the casting directions are perpendicular to each other, there is no problem in this process even if the X layer and Y layer are used at right angles to each other. However, in this embodiment, the explanation will be made assuming that the casting direction marks are made by drilling at the same position.

Next, after drilling, the printing machine 39 prints on the green sheet 47.
The circuit pattern 56 is printed. FIG. 4d shows the green sheet 48 after printing. Even in this process,
The layer green sheet 53 and the Y layer green sheet 54 are printed at the same position with the casting direction mark 52.

The green sheets 48 after printing are pressed in a stacking and laminating press 40 under appropriate temperature and pressure. FIG. 4e shows the green sheet 49 after lamination. Of course, the lamination is the green sheet 48 after each printing.
so that the casting direction marks 52 are at the same position. At this time, since the green sheets are stacked so that the casting direction is perpendicular to the process shown in Figure 4b, the drying shrinkage rate up to the process shown in Figure 4e has no dependence on the casting direction. , and the variation thereof is small, and the lamination accuracy between the upper and lower layers in the process shown in FIG. 4e is extremely high.

The green sheet 49 after lamination is cut out by an external shape punching machine 5
7. Punch out to the required external dimensions. The green sheet 50 after cutting is shown in FIG. 4f. After cutting the outer shape, the green sheet 50 is put into a sintering furnace 41. The sintering furnace 41 consists of a front chamber 42 and a rear chamber 43, and functions similarly to the sintering furnace 11 shown in FIG. The sintering shrinkage rate at this time also has no dependence on the casting direction, and the shrinkage rate is the same in both the vertical and horizontal directions of the multilayer ceramic substrate.

According to this example, the sintering shrinkage rate is not only the same regardless of the casting direction as in the example shown in FIGS. 1 and 2, but also as shown in FIG.
Since the two sheets are laminated so that the casting directions are perpendicular to each other from the pressing process shown in FIG. 1, the drying shrinkage rate up to sintering does not depend on the casting direction, and its variation can be reduced.

In the embodiments shown in FIGS. 3 and 4, two green sheets were laminated in the process shown in FIG. They may be stacked so that they are perpendicular to each other. in this case,
It is not necessarily necessary to stack one layer at a time so that the casting directions are alternately orthogonal to each other, but two layers may be stacked so that the casting directions are alternately orthogonal to each other. Furthermore, the fourth
Although FIG.

As described above, according to the present invention, it is possible to manufacture a multilayer ceramic substrate with high dimensional accuracy without dependence of shrinkage rate on the casting direction. This makes it possible to provide a large ceramic substrate to which leads can be attached with high density and minute pitches. Furthermore, since the lamination accuracy is improved, fine wiring becomes possible.

A comparison will be made between a case where green sheets having the same shrinkage rate are laminated and sintered only in the casting direction as in the past, and a case where green sheets are laminated and sintered in the casting direction and a direction perpendicular to it according to the present invention.

The green sheet used in the experiment had a shrinkage rate of 15.0% in the casting direction and 15.6% in the orthogonal direction.
It was hot.

In this case, the conventional method Shrinkage rate in casting direction 15.0% Orthogonal shrinkage rate 15.6% Therefore, the difference between the two was 0.6%.

On the other hand, according to the present invention, the shrinkage percentage is averaged in both directions, so the shrinkage percentage in the casting direction is 15.3% and the shrinkage percentage in the orthogonal direction is 15.35%. The difference between the two is 0.05%.

Therefore, according to the present invention, the circuit pattern and external cutting dimensions may be designed with a shrinkage rate of 15.3% in mind. By doing so, the error due to shrinkage rate can be suppressed to 0.05%.

On the other hand, in the conventional example, if the circuit pattern and external cutting dimensions are designed with a shrinkage rate of 15.3% in mind,
-0.3% in the casting direction, 0.35 in the orthogonal direction
% error will occur.

In this way, since the sintering shrinkage rate is isotropic as in the present invention, it is possible to experimentally confirm the shrinkage rate in advance and create a larger circuit pattern accordingly, making it easier to design. Easy to control.

On the other hand, in the conventional example, the difference in shrinkage rate is not averaged out as in the present invention, and the difference in shrinkage rate directly becomes an error.

In the above example, a maximum error of 0.35% will occur, which is 0.35 mm for a 100 mm square board. Since the center of the board serves as the reference, there will be an error of 0.175 mm at the edges of the board.

In recent years, as the density has increased and substrates with a pitch of 1.8 mm or more have been adopted, the error of 0.175 mm in the conventional example described above is no longer acceptable.

The present invention can make this error extremely small, and is highly practical.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams for explaining one embodiment of the present invention. FIG. 1 is a diagram schematically showing the steps from casting to sintering of a green sheet, and FIGS. e is a diagram showing the state of the green sheet in each process in Figure 1, Figures 3 and 4.
The figures are diagrams for explaining other embodiments of the present invention, FIG. 3 is a diagram schematically showing the steps from casting to sintering of a green sheet, and FIGS.
f is a diagram showing the state of the green sheet at each step in FIG. 3; 1 and 31...Casting device, 6 and 36...Guide hole/outline punching machine, 7 and 3
8...Punching machine, 8 and 39...Printing machine,
9 and 40...Lamination press machine, 10 and 57
...Outline punching machine, 11 and 41...Sintering furnace,
15 and 45... Green sheet after molding, 1
6 and 47...green sheet after perforation, 17 and 48...green sheet after printing, 18 and 49...green sheet after lamination, 19 and 50
...green sheet after cutting the outer shape, 37...two-sheet press machine, 46...green sheet after pressing two sheets.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a multilayer ceramic substrate, which comprises laminating a plurality of green sheets so that their casting directions are substantially orthogonal and sintering them. 2. The method of manufacturing a multilayer ceramic substrate according to claim 1, wherein the green sheets are alternately stacked so that their casting directions are substantially orthogonal to each other.