JP2001077511A - Manufacture of ceramic board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a ceramic board, where generation of cracks of a metal conductor later to be caused by partial thickening is prevented. SOLUTION: In this manufacturing method, an alumina board, the main body on which a first conductor paste dried member is formed (S2) is baked (S3), and a first metal conductor layer is formed on the surface of the alumina board main body and stuck stiffly and closely to the alumina board main body. After that, a conductor paste is spread on the first metal conductor layer (S4) and dried (S5), and a second conductor paste dried member is formed and baked (S6). At this baking, even if partial thickening is performed by forming a second metal conductor later on the first metal conductor layer, only baking contraction is generated on the second metal conductor layer, the stress is not concentrated in a boundary part between the second metal conductor layer and the first metal conductor layer, i.e., a boundary part between a thickened part and a non-thickened part, generation of craks on the first metal conductor layer is prevented, and generation of disconnection can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a ceramic substrate, and more particularly to a method for manufacturing a ceramic substrate used as a ceramic package for electronics and a circuit board.

[0002]

2. Description of the Related Art In recent years, electronic devices have become more and more sophisticated, compact, and high-density, and semiconductor devices mounted on them have become multi-pin and multi-chip.
Along with this, wire bonding and TAB (Tape Aut) have been used as bonding methods for IC chips and LSI chips.
The flip chip method is more often used than the omated bonding method. The flip chip method is a method in which a solder bump is further formed on a pad formed on one surface of an LSI, and the solder bump is connected to a substrate-side electrode pad. In the flip chip method, the connection length can be shortened, the electrical characteristics can be improved, more pads can be formed without a narrow pitch, and LS
It has such advantages that the ratio between the I area and the package area can be increased and the mounting thickness can be reduced.

In a semiconductor device, an IC chip or L
2. Description of the Related Art A semiconductor element such as an SI chip is mounted on a semiconductor element mounting portion provided on a substrate and put to practical use. Ceramics such as alumina are suitable as a material for this substrate because they have excellent heat resistance, durability, thermal conductivity, and the like, and ceramic semiconductor substrates are currently being used actively.

[0004]

When a conductive pattern is formed on such a ceramic substrate, conductive particles such as W, Mo, Ni, Au, Ag, Ag / Pd alloy, Ag / Pt alloy, Cu, etc. Is used. With the increase in density of electronic equipment, conductor patterns formed on ceramic substrates have been miniaturized, and the width of wiring has been narrowed, so that conductor metals used for conductor wiring should have the lowest possible electrical resistance. preferable.
Among the above metals, low-resistance metals include Au, Ag,
Ag / Pd alloy, Ag / Pt alloy, and Cu can be mentioned. However, Au is expensive, and Ag has problems such as easy migration in a humid atmosphere. , Ag / Pd alloy is preferred. In addition, when the above-mentioned metal conductor layer is prevented from being oxidized, and when the solder is joined to the metal conductor layer, the adhesion between the metal conductor layer and the ceramic substrate due to the reaction between the solder layer and the metal conductor layer is prevented from being reduced. In order to ensure the solder wettability to the layer, the surface of the metal conductor layer is usually plated with Ni and Au after forming the conductor pattern.

The method of forming a conductive pattern on a ceramic substrate is roughly classified into a thin film method, a plating method, a thick film method, and the like. A conductor pattern having a sufficient adhesion strength can be formed at low cost.

When a conductive pattern is formed on a ceramic substrate by printing, a so-called partial thickening is sometimes performed in which a metal conductive layer is partially printed in multiple layers in order to reduce conduction resistance. Generally, the partial thickening is performed by repeating printing and drying a plurality of times, and performing baking after multilayer printing. However, during the sintering process of the metal conductor layer, the upper and lower metal conductor layers shrink before an anchor effect of mechanical engagement for joining the lower metal conductor layer to the ceramic substrate body is developed. It is said that stress is concentrated on the boundary between the upper metal conductor layer and the lower metal conductor layer due to the contraction force, that is, the boundary between the thickened part and the non-thickened part, and cracks are generated in the lower metal conductor layer. There was a problem. Further, there is a problem that when the crack is enlarged, the lower metal conductor layer is disconnected.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a method of manufacturing a ceramic substrate for preventing a metal conductor layer from being cracked by applying a partial thickness. I do.

[0008]

According to the method of manufacturing a ceramic substrate according to the first aspect of the present invention, a conductor paste is applied to the surface of a ceramic substrate body and dried to form a first dried conductor paste. The ceramic substrate body on which the first conductor paste dried body is formed is fired to form a first metal conductor layer on the surface of the ceramic substrate body, and a conductor paste is applied on the first metal conductor layer, dried and dried. The second dried conductor paste is formed on the first metal conductor layer, and the ceramic substrate body having the second dried conductor paste formed on the first metal conductor layer is fired to form a second metal conductor layer on the first metal conductor layer. Form.

The ceramic substrate body of the present invention is not particularly limited. For example, various ceramic materials such as an alumina substrate main body, an aluminum nitride substrate main body, a mullite substrate main body, and a low-temperature fired glass substrate main body can be used. The ceramic substrate body is not particularly limited in structure, form, and manufacturing method. It may be a single layer or a multilayer. Examples of a method for producing a multilayer ceramic molded body include a thick film multilayer printing method and a green sheet multilayer laminating method.

[0010] As a method of applying the conductive paste to the ceramic substrate body, a printing method such as screen printing is suitable. The first and second metal conductor layers may be formed on only one surface of the ceramic substrate main body, or may be formed on both surfaces of the ceramic substrate main body. When the first and second metal conductor layers are formed only on one surface of the ceramic substrate main body, the wiring substrate is formed on only one surface of the ceramic substrate, and the first and second metal conductor layers are formed on both surfaces of the ceramic molded body. And a double-sided wiring board.

The first metal conductor layer is joined to the ceramic substrate body by firing the ceramic substrate body on which the first conductor paste dried body has been formed to form a first metal conductor layer on the surface of the ceramic substrate body. The first metal conductor layer firmly adheres to the ceramic substrate main body due to the mechanical meshing anchor effect. Then, a conductor paste is applied on the first metal conductor layer and dried to form a second conductor paste dry body, and when firing, a second metal conductor layer is formed on the first metal conductor layer. Even if partial thickening is performed, firing shrinkage only occurs in the second metal conductor layer.
Stress is not concentrated on the boundary between the first metal conductor layer and the first metal conductor layer, that is, the boundary between the thickened portion and the non-thickened portion, and cracks are generated in the first metal conductor layer. Can be prevented, and disconnection can be prevented. Therefore, the characteristics of the ceramic substrate are improved, and the reliability is enhanced, and a ceramic substrate with stable quality can be manufactured.

According to the method of manufacturing a ceramic substrate according to the second aspect of the present invention, the conductive paste is made of Cu or A
Since the g-type conductive particles are contained, the electrical resistance of the metal conductive layer can be reduced and the conductive pattern can be made finer. Therefore, it is possible to cope with higher performance, smaller size, and higher density of electronic devices. The conductor paste used in the present invention contains, for example, glass powder, a binder, a solvent, and the like, in addition to the conductor particles described above.

The average particle size of the conductive particles is 0.5 to 10 μm
Is preferably within the range. When the average particle size of the conductive particles is less than 0.5 μm, the bulk specific gravity of the conductive particles becomes small and a large amount of solvent is required for forming a paste, and as a result, the content of the conductive particles in the conductive paste decreases. However, when baked on a ceramic substrate, a densely sintered metal conductor layer is not formed. The average particle size of the conductive particles is 10 μm.
If it exceeds, it becomes difficult to form a fine conductor pattern.

The content of the conductive particles in the conductive paste is 80
~ 90 wt% is preferred. If the content of the conductive particles in the conductive paste is less than 80 wt%, the conductivity of the formed conductive layer will be small. In addition, the content of the conductive particles is 90 wt.
%, The adhesiveness of the metal conductor layer to the ceramic substrate body decreases.

The conductor paste usually contains a glass powder. As the glass powder, a known paste which has been conventionally used for a conductor paste, such as borosilicate glass to which various metals are added, is used. can do. As the borosilicate glass, a lead borosilicate glass having relatively excellent chemical durability is preferable. Further, the average particle size of the glass powder is preferably in the range of 0.5 to 10 μm. When the average particle size of the glass powder is less than 0.5 μm, the adhesive strength between the metal conductor layer and the ceramic substrate main body becomes small. If the average particle size of the glass powder exceeds 10 μm, it becomes difficult to form a fine conductor pattern. Note that, in addition to the glass powder, a powder of a metal oxide such as copper oxide or zinc oxide which has a function of bonding the metal conductor layer to the ceramic substrate may be added.

The content of the glass powder in the conductor paste is preferably 0.1 to 10% by weight. When the content of the glass powder is less than 0.1 wt%, the adhesive strength of the formed metal conductor layer to the ceramic substrate body becomes small. Also,
When the content of the glass powder exceeds 10% by weight, the electrical conductivity decreases.

In the conductor paste, a binder, a solvent and the like are usually used as a vehicle for dispersing the conductor particles and the glass powder. As a binder for the conductor paste, for example, acrylic resin, cellulose resin,
Known resins such as methacrylic resin are exemplified. Examples of the solvent for the conductive paste include known solvents such as toluene, xylene, terpineol, and dibutyl phthalate. The content of the binder in the conductive paste is preferably 0.5 to 6% by weight, and the content of the solvent is 2 to 10% by weight.
wt% is preferred.

When the content of the binder is less than 0.5 wt%, the viscosity of the conductor paste required for printing is too small, so that the dispersibility of the conductor paste is reduced, and the conductor paste is easily aggregated or precipitated. The dried body cannot be adhered to the ceramic substrate body. On the other hand, if the content of the binder exceeds 6% by weight, the viscosity of the conductive paste increases and the fluidity decreases, so that printing cannot be performed well.

On the other hand, if the content of the solvent is less than 2 wt%, the fluidity of the conductor paste is reduced, and printing cannot be performed satisfactorily. If the content of the solvent exceeds 10 wt%,
Since the solid content is low, shrinkage increases when the printed conductor paste is fired. The conductive paste can be prepared by a known preparation method such as a method using three rolls.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. (First Embodiment) A first embodiment in which the present invention is applied to a method for manufacturing an alumina substrate will be described with reference to FIGS.

First, a method for manufacturing an alumina substrate body will be described. Add a sintering aid such as magnesia, silica, calcined talc, calcium carbonate, etc. to alumina powder and a small amount of coloring agent such as titanium oxide, chromium oxide, molybdenum oxide. And a solvent such as toluene, xylene, alcohol, etc., and sufficiently kneaded to obtain a viscosity of 2,000 to 4,000.
A slurry of 0 cps is prepared, and a green sheet of, for example, 0.3 mm thick alumina is formed by a doctor blade method. By firing this alumina green sheet at 1500 to 1600 ° C. in a nitrogen-hydrogen mixed gas atmosphere, an alumina substrate body is obtained.

Next, a method for forming a conductor pattern on the surface of the alumina substrate body will be described. (1) As shown in FIG. 2, a conductor paste containing Cu powder, glass powder, a binder, a solvent and the like as conductor particles is printed on the surface of the alumina substrate body 1 by a screen printing method (Step S1 in FIG. 1). ) And dried (step S2 in FIG. 1) to form the first dried conductor paste body 2.

(2) Using an electric continuous belt furnace, the alumina substrate body 1 having the first conductor paste dried body 2 formed on the surface is held at 900 ° C. for 10 to 20 minutes in a nitrogen atmosphere. By firing (Step S3 in FIG. 1), a first metal conductor layer is formed on the surface of the alumina substrate body 1.

(3) As shown in FIG. 3, a conductor paste similar to that used in the above (1) is printed on the first metal conductor layer 20 by a screen printing method (step S in FIG. 1).
4) After drying (Step S5 in FIG. 1), the second dried conductor paste 3 is formed.

(4) Using an electric continuous belt furnace, the first
The alumina substrate main body 1 having the second conductor paste dried body 3 formed on the metal conductor layer 20 of Example 1 was heated at 900 ° C. in a nitrogen atmosphere.
Firing is performed under the holding conditions of 10 to 20 minutes (step S in FIG. 1).
6).

According to the above steps (1) to (4), the second metal conductor layer 3 is formed on the first metal conductor layer 20 as shown in FIG.
Thus, the alumina substrate 10 on which 0 is formed is obtained. And
If necessary, the first and second metal conductor layers 20 and 3
0 is plated with Ni and Au.

The alumina substrate 1 manufactured as described above
0 indicates that the first metal conductor layer 20 is firmly adhered to the ceramic substrate main body 1 by an anchor effect of mechanical engagement for joining the first metal conductor layer 20 to the ceramic substrate main body 1. , The second on the first metal conductor layer 20.
Even if the metal conductor layer 30 is formed and partially thickened, only the second metal conductor layer 30 shrinks during firing, and the second metal conductor layer 30 and the first metal conductor layer 20 The stress does not concentrate on the boundary portion 25, that is, the boundary portion between the thickened portion and the non-thickened portion, so that the first metal conductor layer 20 is prevented from being cracked and disconnected. can do.

Next, on the alumina substrate 10 shown in FIG. 4, the thickness of the first metal conductor layer 20 was made constant and the thickness of the second metal conductor layer 30 was changed to measure the crack generation rate. Is shown in FIG.

In FIG. 5, the print thickness of the first metal conductor layer 20 is fixed at 20 μm, and the print thickness of the second metal conductor layer 30 changes from 5 μm to 30 μm. The number of measurement points is 1,000. As shown in FIG. 5, in the first embodiment, the second metal conductor layer 30
No crack is generated in the first metal conductor layer 20 irrespective of the film thickness of the first metal conductor layer 20.

Next, Comparative Example 1 in which printing and drying of the conductive paste were repeated twice on the alumina substrate body to form a two-layer dried conductive paste and then baked once was shown in FIG.
8 and 9. In Comparative Example 1, an alumina substrate was manufactured using the alumina substrate body 1 of the first embodiment shown in FIG. 2 and the same conductor paste used in the first embodiment.

In Comparative Example 1, as shown in FIG.
A conductor paste is printed on the surface of the alumina substrate main body 1 by a screen printing method (Step S11 in FIG. 7), and after drying (Step S12 in FIG. 7), the conductor paste is further printed by a screen printing method (FIG. 7). Step S1
3) and drying (Step S14 in FIG. 7), a two-layer dried conductor paste 4 was formed. Then, using an electric continuous belt furnace, the alumina substrate main body 1 having the two-layer dried conductor paste 4 formed on the surface thereof was heated at 900 ° C. in a nitrogen atmosphere.
Baking is performed under the holding conditions of 10 to 20 minutes (Step S1 in FIG. 7)
5) As shown in FIG. 9, two metal conductor layers 40 were formed on the surface of the alumina substrate body 1.

In the comparative example 1 thus manufactured, an anchor of mechanical engagement for joining the lower metal conductor layer 40 to the alumina substrate body 1 in the process of sintering the two metal conductor layers 40. Before the effect is developed, the upper and lower metal conductor layers 40 shrink, and the contraction force causes the boundary 4 between the upper metal conductor layer 40 and the lower metal conductor layer 40.
5, that is, stress is concentrated on the boundary between the thickened portion and the non-thickened portion, and a crack 50 is generated in the lower metal conductor layer 40. Further, when the crack 50 expands, the lower metal conductor layer 40 may be disconnected.

Next, in Comparative Example 1, the results of measuring the crack generation rate while keeping the thickness of the lower metal conductor layer 40 constant and changing the thickness of the upper metal conductor layer 40 are shown in FIG.

In FIG. 5, the print thickness of the lower metal conductor layer 40 is fixed at 20 μm, and the print thickness of the upper metal conductor layer 40 changes from 5 μm to 30 μm. The number of measurement points is 1,000.

As shown in FIG. 5, in Comparative Example 1,
When the print thickness of the lower metal conductor layer 40 is 5 μm, the crack generation rate is 10%. When the print thickness of the lower metal conductor layer 40 is 10 μm, the crack generation rate is 49%. The printed film thickness of the metal conductor layer 40 is 20 μm and 30 μm
In this case, the crack generation rate is 100%.

On the other hand, in the first embodiment, the cracks do not occur in the first metal conductor layer 20 irrespective of the thickness of the second metal conductor layer 30, so that the characteristics of the alumina substrate 10 are improved. Alumina substrate 10 with improved reliability and stable quality
Can be manufactured.

(Second Embodiment) In the second embodiment, the Cu powder contained in the conductor paste used in the first embodiment is replaced with Ag / Pt powder or Ag / Pd powder as conductor particles. Yes, except that the sintering is performed in an oxidizing atmosphere, it is the same as in the first embodiment, so that the description of the manufacturing process is omitted, the film thickness of the first metal conductor layer is made constant, and the film thickness of the second metal conductor layer is increased. FIG. 6 shows the results of measuring the crack generation rate with changing the thickness.

In FIG. 6, the printed film thickness of the first metal conductor layer is fixed at 20 μm, and the printed film thickness of the second metal conductor layer changes from 5 μm to 30 μm. In addition,
There are 1000 measurement points. As shown in FIG. 6, in the second embodiment, no crack is generated in the first metal conductor layer regardless of the thickness of the second metal conductor layer.

Next, using the same conductive paste containing Ag / Pt powder or Ag / Pd powder as in the first embodiment, printing and drying were performed on the same alumina substrate body as used in the second embodiment. After repeating twice, forming a two-layer dried conductor paste and firing it once, in Comparative Example 2, the thickness of the lower metal conductor layer was made constant, and the thickness of the upper metal conductor layer was changed. FIG. 6 shows the results of measuring the crack occurrence rate.
Shown in

In FIG. 6, the print thickness of the lower metal conductor layer is fixed at 20 μm, and the print thickness of the upper metal conductor layer changes from 5 μm to 30 μm. In addition,
There are 1000 measurement points.

As shown in FIG. 6, in Comparative Example 2,
When the printed thickness of the lower metal conductor layer is 5 μm, the crack occurrence rate is 10%, and the printed thickness of the lower metal conductor layer is 10%.
When the thickness is μm, the crack generation rate is 49%, and when the printed film thickness of the lower metal conductor layer is 20 μm and 30 μm, the crack generation rate is 100%.

On the other hand, in the second embodiment, the cracks did not occur in the first metal conductor layer regardless of the thickness of the second metal conductor layer, so that the characteristics of the alumina substrate were improved, and the reliability was improved. And an alumina substrate with stable quality can be manufactured.

In the embodiments of the present invention described above,
Baking the alumina substrate body on which the first conductor paste dried body is formed to form a first metal conductor layer on the surface of the alumina substrate body, thereby joining the first metal conductor layer to the alumina substrate body; The first metal conductor layer firmly adheres to the alumina substrate main body due to the anchor effect of mechanical engagement. Thereafter, a conductor paste is applied on the first metal conductor layer and dried to form a second conductor paste dry body,
In the case of firing, even if the second metal conductor layer is formed on the first metal conductor layer and partially thickened, only the firing shrinkage occurs in the second metal conductor layer. Stress is not concentrated on the boundary between the first metal conductor layer and the first metal conductor layer, that is, at the boundary between the thickened portion and the non-thickened portion, thereby preventing the first metal conductor layer from cracking. Disconnection can be prevented. Therefore, the characteristics of the alumina substrate are improved, and the reliability can be increased to produce an alumina substrate with stable quality.

In the present invention, the present invention is not limited to the alumina substrate, and may be applied to any method of manufacturing a ceramic substrate such as an aluminum nitride substrate, a mullite substrate, and a low-temperature fired glass substrate. Needless to say, the present invention can be applied to a method of manufacturing a ceramic substrate having a wiring or the like formed therein.

[Brief description of the drawings]

FIG. 1 is a process chart showing a first embodiment in which the present invention is applied to a method for manufacturing an alumina substrate.

FIG. 2 is a schematic cross-sectional view for explaining a method of manufacturing an alumina substrate according to a first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view for explaining a method of manufacturing an alumina substrate according to a first embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view for explaining a method for manufacturing an alumina substrate according to the first embodiment of the present invention.

FIG. 5 is a data diagram showing the results of measuring the crack occurrence rates of the first example of the present invention and the comparative example 1.

FIG. 6 is a data diagram showing the results of measuring the crack occurrence rates of the second example of the present invention and the comparative example 2.

7 is a process chart showing a method for manufacturing an alumina substrate according to Comparative Example 1. FIG.

FIG. 8 is a schematic cross-sectional view for explaining a method for manufacturing an alumina substrate according to Comparative Example 1.

FIG. 9 is a schematic cross-sectional view illustrating a method for manufacturing an alumina substrate according to Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alumina substrate main body 2 1st conductor paste dried body 3 2nd conductor paste dried body 10 Alumina substrate 20 1st metal conductor layer 25 Boundary part 30 2nd metal conductor layer 50 Crack

Continued on front page F term (reference) 4E351 AA07 BB01 BB31 BB35 CC12 CC13 CC23 CC35 DD04 DD05 DD52 EE01 EE10 EE13 EE24 GG02 5E343 AA02 AA24 BB23 BB24 BB25 BB44 BB48 BB72 DD03 DD32 ER33 ER35 ER37 GG01

Claims (2)

[Claims] 1. A method for manufacturing a ceramic substrate comprising a ceramic substrate main body and a conductor pattern provided on a surface of the ceramic substrate main body, wherein a conductor paste is applied to the surface of the ceramic substrate main body and dried. Forming a first dried conductor paste body by heating the ceramic substrate body on which the first dried conductor paste body is formed, and forming a first conductor paste dried body on the surface of the ceramic substrate body.
Forming a metal conductor layer, applying a conductor paste on the first metal conductor layer, and drying to form a second conductor paste dried body; and forming a second conductor paste dried body on the first metal conductor layer. Baking the ceramic substrate body on which the second conductor paste dried body has been formed to form a second metal conductor layer on the first metal conductor layer. Method. 2. The method according to claim 1, wherein the conductive paste is Cu based or A
The method for producing a ceramic substrate according to claim 1, further comprising g-type conductive particles.