JPH07221453A - Manufacture of multilayer ceramic substrate - Google Patents

Abstract

PURPOSE:To surely enable mass production of a substrate of good dimensional accuracy, etc., by reducing temperature dependency during temporary burning by properly changing density of high melting point metallic paste before temporary burning so that burning contraction coefficient of a high melting point metal and sintering contraction coefficient of ceramics in a temporary burning temperature region almost coincide with each other. CONSTITUTION:A green sheet 1 is manufactured by forming a sheet of slurry containing aluminum nitride powder as a main element. A plurality of through hole formation holes 2 are formed in a specified position of the green sheet 1. Then, tungsten paste P as high melting point paste is printed in the green sheet 1, a through hole inner conductor circuit 3a is formed inside the through hole formation hole 2 of the green sheet 1 and a wiring pattern 3b is formed in a surface of the green sheet 1. A plurality of green sheets 1 are laminated and a green sheet lamination body 4 is acquired by thermocompression. Then, the lamination body 4 is temporarily burned, set at a hot press device 6 and burned.

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 ceramic substrate.

[0002]

2. Description of the Related Art Conventionally, there has been known a method for manufacturing a multilayer ceramic substrate in which ceramic green sheets having a conductor pattern formed by printing a high-melting-point metal paste are stacked, and pre-baking and main baking are performed by hot pressing. Has been. When manufacturing a substrate of this type, it is generally considered preferable to take a plurality of multilayer ceramic substrates from one sintered body. At that time, in order to improve the dimensional accuracy of the substrate, it is necessary to surely prevent the swelling, delamination and cracking of the green sheet laminate during the preliminary firing.

Under these circumstances, the applicant of the present application has found that the temperature range in which the sintering shrinkages of the refractory metal and the ceramics are substantially the same, preferably in the range where the difference in the sintering shrinkages is 0.1% or less. In the separate application, a method of performing calcination in-house was previously proposed. According to this method, the internal stress acting on the green sheet laminate at the time of calcination becomes extremely small, and preferable results such as swelling are surely prevented are obtained.

[0004]

Since the above-mentioned suitable temperature range is about ± 10 ° C. which is the optimum temperature for calcination at the maximum, the calcination is carried out after the furnace temperature is set within a limited range. Required to do. Therefore, it is preferable to use a furnace in which the temperature control of the heater can be surely performed and the temperature unevenness depending on the position is small in the calcination under the condition that the temperature dependency is high.

However, in the case of using a furnace (for example, a large-scale furnace for mass production) in which the temperature unevenness tends to be relatively large, even if the temperature of the heater itself is within a suitable range, all green sheet laminates in the furnace are It becomes impossible to heat to a suitable temperature. Therefore, in the case where the material was pre-baked outside the preferable temperature range, swelling and the like occurred as in the conventional case, and as a result, the non-defective rate was often lowered. For this reason,
At present, it was difficult to mass-produce substrates.

The present invention has been made in view of the above circumstances, and an object thereof is to widen the temperature range suitable for pre-baking to reduce the temperature dependence during pre-baking. Accordingly, it is an object of the present invention to provide a method for manufacturing a multilayer ceramic substrate, which enables reliable mass production of substrates having excellent dimensional accuracy and the like.

[0007]

In order to solve the above problems, according to the invention of claim 1, after laminating ceramic green sheets having a conductor pattern formed by printing a refractory metal paste, In the method for manufacturing a multilayer ceramic substrate in which the laminate is subjected to calcination and main calcination by hot pressing, the calcination shrinkage of the refractory metal and the sinter shrinkage of the ceramic in the calcination temperature range are substantially the same. The gist of the present invention is a method for manufacturing a multilayer ceramic substrate, which is characterized in that the density of the high-melting-point metal paste is appropriately changed and then calcination is performed.

According to the second aspect of the present invention, after the ceramic green sheets having the conductor pattern formed by printing the high melting point metal paste are laminated, the laminated body is subjected to temporary firing and main firing by hot pressing. In the method for producing a multilayer ceramic substrate, the average particle diameter of the refractory metal and the average particle diameter of the ceramic are set so that the firing shrinkage rate of the refractory metal and the sintering shrinkage rate of the ceramic in the calcination temperature range are substantially the same. The gist is a method for producing a multilayer ceramic substrate, which is characterized by performing calcination after appropriately changing at least one selected from the above.

[0009]

According to the invention described in claim 1, if the density of the refractory metal paste is appropriately changed, the firing shrinkage curves of the refractory metal and the ceramics in the calcination temperature range can be made substantially equal to each other. It was made based on the finding that the width of a suitable temperature range can be widened.

According to the second aspect of the present invention, if the average particle size of at least one of the refractory metal and the ceramics is appropriately changed, the sintering shrinkage rate curves of both can be made substantially coincident with each other. This is based on the finding that the width of the temperature range suitable for firing can be widened.

The method of manufacturing the multilayer ceramic substrate of the present invention will be described in detail below with reference to the graphs of FIGS. The graphs of FIGS. 3 and 4 show the relationship between the firing shrinkage and the heating temperature of refractory metals and ceramics during pre-firing. In the graph, C2 is a curve showing the shrinkage rate (%) of refractory metal, and C1 is a curve showing the shrinkage rate (%) of ceramics. C3 is a curve representing the absolute value (%) of the difference between the firing shrinkage of the refractory metal and the firing shrinkage of the ceramics. Ta represents the calcination temperature (about 1560 ° C.) in the conventional method.

As shown in the figure, both the curve C1 and the curve C2 are curves that increase with the heating temperature (increasing to the right). Curve C3 is the calcination temperature T
It is a curve that has a maximum value at a temperature near a. That is, in the conventional method, the calcination was performed in a state where the difference in the calcination shrinkage rate between the two was large. However, if the paste printing area is relatively small as in the conventional case, even if pre-baking is performed at such a temperature, no particular problem occurs. On the contrary, when the proportion of the printing area increases, the green sheet laminate swells when pre-baking is performed at the above temperature,
Delamination and cracking are likely to occur.

By the way, the curves C1 and C2 have a temperature T2 slightly higher and a temperature T1 slightly lower than the calcination temperature Ta.
Are intersecting at two points. this is,
It is considered that neck sintering of refractory metal proceeds at a lower temperature range than neck sintering of ceramics. In the temperature regions Z1 and Z2 near the intersection, the difference in firing shrinkage between the two becomes small, and theoretically becomes zero at the completely intersecting point. Therefore, when the printing area is large, it is necessary to carry out the calcination within the temperature ranges Z1 and Z2 in which the calcination shrinkage rates of both are substantially equal to each other, and more preferably at the temperatures T1 and T2 that completely intersect each other. become. If the above calcination conditions are not satisfied, the inconsistency in the firing shrinkage of the refractory metal and the ceramics cannot be resolved. However, if it is assumed that the difference in firing shrinkage (%) ≦ 0.1 is within the allowable range, both of the temperature ranges Z1 and Z2 are narrow ranges of about 10 ° C. to 20 ° C.

As described above, the gist of the present invention is to appropriately change the density of the high melting point metal paste or the average particle size of at least one of the high melting point metal and the ceramics. Therefore, the reason why such a factor change is performed will be described below.

In other words, the above-mentioned changes can change the degree of neck sintering of the refractory metal to some extent. Similarly, if the above-mentioned changes are made, the progress of neck sintering of the refractory metal or ceramics can be changed to some extent.

For example, it has been experimentally found that when the density of the refractory metal paste is increased, neck sintering of the refractory metal in the paste becomes difficult to proceed. That is, when the density is changed as described above, the sharp increase in the shrinkage ratio observed during the progress of neck sintering occurs at a higher temperature. Then, the firing shrinkage curve C2 of the refractory metal shifts to the position of the curve C4 shown in FIG. 3, and as a result, it approaches the locus of the firing shrinkage curve C1 of the ceramics. The same tendency is observed when the average particle size of the refractory metal is increased.

It has been experimentally known that, when the average particle size of the ceramics is increased, neck sintering of the ceramics becomes difficult to proceed. That is, with the above changes, the sharp increase in shrinkage seen during neck sintering progresses at a lower temperature. Then, the firing shrinkage rate curve C1 of the ceramics shifts to the position of the curve C5 shown in FIG. 4, and as a result, it approaches the locus of the firing shrinkage rate curve C2 of the refractory metal.

When the above changes are made, as shown in FIGS. 3 and 4, the new temperature range Z3 suitable for pre-baking is:
It is certainly wider than the temperature ranges Z1 and Z2 so far. As a result, the temperature dependence during calcination becomes smaller than in the past. Therefore, even when the pre-baking is performed in a furnace or the like where the temperature unevenness is likely to be large, it is possible to reliably manufacture a substrate having excellent dimensional accuracy and the like. That is, this means that the substrate can be mass-produced by performing the calcination in the large-scale mass-production furnace.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is embodied in a method for manufacturing a multilayer aluminum nitride substrate will be described in detail below with reference to FIGS.

In this embodiment, the green sheet (thickness 4
Around 100 μm, 200 mm square 1 is produced by sheet-forming a slurry containing aluminum nitride (hereinafter referred to as AlN) powder as a main component by a doctor blade method. The green sheet 1 has a predetermined position as shown in FIG.
As shown in FIG. 5, a plurality of through-hole forming holes 2 are formed by drilling or punching. Next, a tungsten (hereinafter, W) paste P as a high melting point metal paste is printed on the green sheet 1 by a screen printing machine. And FIG.
As shown in (b), the through hole conductor circuit 3a is formed in the through hole forming hole 2 of the green sheet 1, and the wiring pattern 3b is formed on the surface of the green sheet 1.

As a result of the paste printing, as shown in FIG. 2, there are 8 printing areas R1 of substantially square shape on the green sheet 1.
They are arranged in a unit of 8 columns. On the other hand, each print area R
The non-printed regions R2 are formed in a grid pattern between 1's. In this embodiment, the ratio of the area of the printing region R1 to the surface area of the green sheet 1 is about 70%.
However, this ratio is not limited to 70%.

Further, in this embodiment, as the slurry for producing the green sheet 1, Al having an average particle size of about 1.7 μm is used.
Yttrium oxide powder as a sintering aid, an acrylic binder, a dispersant and a plasticizer are mixed with N powder,
The one that is uniformly kneaded is used. The green sheet 1 thus produced has a density of 2.1 g / cm ³ .

As the W paste P for forming the through-hole conductor circuit 3a and the wiring pattern 3b, the following is used. That is, it is a paste in which W particles having a predetermined average particle size (1.1 μm or 3.0 μm) are mixed with an acrylic binder, a solvent, and uniformly mixed. Of the paste P, the one having an average particle size of W particles of 1.1 μm has a density of 7.5 g / cm ³ , which is 3.0
The density of μm is 11.0 g / cm ³ .

When the paste P is prepared, it is preferable that the W particles have an average particle size of about 0.5 μm to 4.0 μm. If the average particle size of W particles is too small, the sintering temperature of W becomes low. However, in this case, there are the following problems.
As the sintering temperature of W becomes lower, W and AlN
The temperature at which the firing shrinkage percentages are the same is also low. At this time,
When the temperature is about 1450 ° C. or lower, carbonization of W is hindered, so that the sheet resistance may increase. Further, the smaller the average particle size of W particles, the larger the slope of the firing shrinkage ratio curve. Therefore, in the temperature range in which W and AlN have substantially the same firing shrinkage, the smaller the average particle size of W particles, the greater the variation in firing shrinkage due to temperature. Therefore, it becomes easy to be affected by the variation in the temperature in the furnace.

On the contrary, if the average particle size of W particles is too large, the printability is deteriorated, and there is a possibility that a fine wiring pattern 3b cannot be obtained. In the present embodiment, the average particle size of W particles is set in advance within the suitable range for the reasons described above.

The green sheet 1 has a wiring pattern 3
After the temporary pressing for b, a plurality of sheets are laminated as shown in FIG. The green sheet laminate 4 obtained by thermocompression bonding with a laminating device or the like is dried and degreased here.

Next, the green sheet laminate 4 is pre-baked in a non-oxidizing atmosphere. In this example, a predetermined heating temperature (146 as shown in Table 1 was used during calcination.
The time for holding the firing furnace at 0 ° C. to 1600 ° C.) is 10 hours. In addition, in the present embodiment, the preliminary firing is performed by a firing furnace for small lot production with less temperature unevenness.

The calcined green sheet laminate 4 is
Further, it is set in a hot press device 6 as shown in FIG. 1 (d), and is subjected to main firing (1890 ° C., 3 hours) under high temperature pressure. As a result, the green sheet laminated body 4 becomes the sintered body 5.

After the surface grinding, the sintered body 5 is cut at the non-printed area R2 (the portion indicated by the broken line in FIG. 2). The result is a total of 64 pieces of 22
Thus, the multi-layered AlN substrate 7 having a square mm is obtained.

Here, as shown in Tables 1 and 2, the heating temperature was set in 8 steps (1460 ° C, 1480 ° C, 1500 ° C, 1520 ° C, 15
The temperature was set at 40 ° C, 1560 ° C, 1580 ° C, 1600 ° C) and calcined by the same method. As a result, a total of 24 types of samples were obtained. Among the samples, the sample A group is a sample of the example, and the sample B group is a sample of a comparative example (conventional example) which does not belong to the range of the example. Among the samples A1 to A16, eight kinds of samples A1 to A8 shown in Table 1 are set so that the density of the W paste P is higher than that of the sample B group. Further, in the eight kinds of samples A9 to A16 shown in Table 2, the average particle size of W particles is set to be larger than that of the sample B group.

Then, in the tests for these, the difference in firing shrinkage between W and AlN (%), X in the wiring pattern 3b,
The amount of dimensional variation (± μm) in the Y direction, and the presence or absence of swelling, delamination, and cracks were investigated. Further, based on the above results, it was evaluated whether or not the calcination at that temperature is effective.

[0032]

[Table 1]

[0033]

[Table 2]

As is clear from Tables 1 and 2, it was found that the difference in the firing shrinkage of Sample A group was 0.1% or less, which is the allowable range, at any temperature.
When the amount of dimensional variation of the wiring pattern 3b was measured,
In the sample A group, the maximum was 21 μm, while
The sample B group had a value of 20 μm to 45 μm. Further, in sample A group, swelling or the like was not observed at any temperature. On the other hand, in sample B group, it was confirmed that swelling and the like occur at the temperature at which the difference in firing shrinkage rate becomes large. From the above results, it can be seen that the temperature range suitable for the calcination is surely widened by the method of the embodiment as compared with the conventional method. Therefore, it can be said that the temperature dependence during the calcination is also reduced.

In addition, when the laminated body 4 is calcinated in a mass-production firing furnace, temperature variations can occur depending on the mounting position of the laminated body 4, but almost all the laminated bodies 4 have dimensional accuracy. It was possible to obtain an excellent multilayer AlN substrate 7. That is, it was possible to surely improve the non-defective rate as compared with the conventional method.

The present invention is not limited to the above embodiment, but can be modified as follows. For example, (a) instead of the example using the AlN green sheet 1, it is possible to use a green sheet made of alumina, silicon nitride, mullite, boron nitride, or the like.

(B) Further, instead of the embodiment using the W paste P, it is of course possible to use a refractory metal paste other than tungsten, such as molybdenum, niobium, tantalum or the like.

[0038]

As described in detail above, according to the method for manufacturing a multilayer ceramic substrate of the present invention, the width of the temperature range suitable for pre-baking is widened, and therefore the temperature dependence during pre-baking is reduced. Therefore, it is possible to reliably mass-produce a substrate having excellent dimensional accuracy and the like, which is an excellent effect.

[Brief description of drawings]

1A to 1D are schematic cross-sectional views showing a manufacturing procedure of a multilayer aluminum nitride substrate of an example.

FIG. 2 is a schematic plan view showing a green sheet before lamination in a manufacturing procedure of a multilayer aluminum nitride substrate.

FIG. 3 is a graph showing the relationship between the firing shrinkage and the heating temperature of refractory metals and ceramics during pre-firing.

FIG. 4 is a graph showing the relationship between the firing shrinkage and the heating temperature of refractory metals and ceramics during pre-firing.

[Explanation of symbols]

1 ... Green sheet, 3a, 3b ... Conductor pattern, 4 ...
(Green sheet) Laminated body, 7 ... Multilayer aluminum nitride substrate as multilayer ceramic substrate, P ... Tungsten paste as refractory metal paste.

Claims (2)

[Claims] 1. A method for producing a multilayer ceramic substrate, comprising stacking ceramic green sheets having a conductor pattern formed by printing a high-melting-point metal paste, and then subjecting the stacked body to pre-baking and main baking by hot pressing. , So that the firing shrinkage of the refractory metal and the sintering shrinkage of the ceramics in the calcination temperature range substantially match,
A method for manufacturing a multi-layer ceramic substrate, which comprises calcination after appropriately changing the density of the high melting point metal paste. 2. A method for manufacturing a multilayer ceramic substrate, comprising stacking ceramic green sheets having a conductor pattern formed by printing a high-melting-point metal paste, and then subjecting the stacked body to pre-baking and main baking by hot pressing. , So that the firing shrinkage of the refractory metal and the sintering shrinkage of the ceramics in the calcination temperature range substantially match,
A method for manufacturing a multilayer ceramic substrate, which comprises performing appropriate firing after appropriately changing at least one selected from an average particle diameter of refractory metal and an average particle diameter of ceramics.