JPH04193762A - Raw material powder for simultaneous calcination of ceramic substrate and its production - Google Patents

Abstract

PURPOSE:To prevent the generation of cristobalite by simultaneous calcination after forming a green sheet as substrate and a circuit pattern using a paste containing a codielite powder coated with Al2O3, a glass powder and an organic binder. CONSTITUTION:After mixing codielite powder into aluminum alkoxide solution followed by drying and calcining to prepare a codielite powder coated with Al2O3, the codielite powder and a glass powder such as borosilicate, etc., expressed as CaO-SiO2-B2O3 forming anorthite by reacting with Al2O3 and an organic binder are mixed in an organic solvent such as ethanol to prepare a pasty raw material incorporating the glass powder coated with about >0.01mum film thickness of Al2O3 (1wt.% based on glass powder). This paste is applied to a green sheet for substrate by using Docter blade method, and a silver base circuit pattern is screen-printed on to the surface thereon. This printed sheets are calcined in atmosphere to obtain simultaneous the objective calcined ceramic substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic substrate for co-firing.

[Conventional technology and its problems] Conventional co-firing substrates are made by forming a raw material paste with aluminum oxide powder, making a green sheet with this raw material paste, drawing a circuit pattern on it, and combining the green sheet and the circuit pattern. It was formed by simultaneous firing in a high temperature atmosphere of 1500 degrees Celsius or higher.

However, in the above-mentioned conventional method for producing ceramic substrates for co-firing, since the 2M degree firing of aluminum oxide powder is a high temperature of over 1,500 degrees Celsius, the circuit pattern is made of a high-melting point metal that can withstand high-temperature firing, such as tungsten or molybdenum. I have to. Since these high melting point metals have high resistivity, they have the disadvantage of deteriorating circuit characteristics of hybrid integrated circuits and the like formed on ceramic substrates.

Therefore, we would like to propose a ceramic substrate that can be fired at a low temperature so that circuit patterns can be drawn using silver thread or copper-based conductive paste with low resistivity.
JP-A-60-260465, etc.). This green sheet for ceramic substrates is made of a paste containing aluminum oxide and glass powder, and can be fired at about 900 degrees Celsius.

Therefore, it can be fired simultaneously with the silver thread or copper-based conductor paste, and a circuit pattern with low resistivity can be realized.

However, when a silicon semiconductor integrated circuit is mounted on the ceramic substrate fired at a low temperature, the silicon semiconductor integrated circuit tends to fall off and the circuit characteristics deteriorate. This is because the ceramic substrate is mainly composed of aluminum oxide, and as a result, when the hybrid integrated circuit repeatedly functions and stops, it is repeatedly subjected to thermal stress, causing the silicon semiconductor integrated circuit to fall off. In addition, the deterioration of circuit characteristics is due to the high dielectric constant of aluminum oxide (9.5 to 10.5).
), and a large parasitic capacitance is added to the conductor pattern.

In order to solve this problem with ceramic substrates whose main component is aluminum oxide, a paste made of cordierite powder and silicate glass powder is used to form a green sheet, and this is coated with silver thread or copper. A method for manufacturing ceramic substrates for low-temperature firing on which conductor patterns are drawn has been proposed. Although ceramic substrates containing cordierite as a main component can improve circuit characteristics, they still have problems in that silicon semiconductor integrated circuits often fall off, resulting in low substrate reliability. The coefficient of thermal expansion of Cope and Yellite is approximately 2 x 10-6/°C, and although it is relatively close to silicon, some flaking occurred.

[Means for Solving the Problems] The inventor of the present invention researched the cause of the above-mentioned silicon semiconductor integrated circuit falling off, and found that the cause was cristobalite produced by the reaction between cordierite and silicate glass during firing. I discovered that. That is, cordierite (2MgO-'2A I 2O3-5 S i 0
When 2) and borosilicate glass (B2O3-5i○2) are fired, excess silicon dioxide (S i O2) is precipitated as cristobalite.

The second cristobalite has a coefficient of thermal expansion of 6X10-6/°
C, which worsened the coefficient of thermal expansion of the ceramic substrate.

The present inventor researched a method to prevent the generation of cristobalite during firing, and combined excess silicon with calcium oxide and aluminum oxide to form anorthite (CaO-
Since anorthite has a thermal expansion coefficient of 4.5XIO-6/'C, the inventors have come up with the idea that the thermal expansion coefficient of a ceramic substrate can be brought close to that of silicon by generating Al2O22SiO2).

Therefore, the gist of the first invention of the present application is to provide powder in which each particle of cordierite powder is coated with aluminum oxide;
A raw material powder for producing co-fired ceramic substrates containing a mixed powder with glass powder that combines with aluminum oxide to form anorthite.

The gist of the second invention is that each particle of cordierite powder is coated with aluminum oxide, and the raw material powder coated with aluminum oxide is mixed with glass powder that combines with aluminum oxide to produce anorthite. Add an organic binder to form a raw material paste, form a substrate green sheet with the raw material paste, form a circuit pattern on the substrate green sheet, and co-fire the substrate green sheet and the circuit pattern. It is to be.

The glass powder that produces the above anorthite is (CaO-
51o2-B2O3) or (CaO-Al2O2S
i02).

[Operations and Effects of the Invention] In the above-mentioned raw material powder, each particle of cordierite powder is coated with aluminum oxide, so that during simultaneous firing, the glass powder comes into direct contact with cordierite and generates cristobalite. prevent. Further, since aluminum oxide reacts with the glass powder to generate anorthite, the coefficient of thermal expansion of the ceramic substrate can be made close to that of silicon. The reason why the average film thickness of aluminum oxide is set to 0.01 μm or more per 1% by weight of glass powder is because a film thickness smaller than this cannot prevent the generation of cristobalite.

According to the above manufacturing method, a raw material paste is formed from the mixed powder, and a green sheet for a substrate is formed from the raw material paste. A circuit pattern is formed on the substrate green sheet, and the substrate green sheet and the circuit pattern are co-fired. Glass powder in the raw material paste combines with aluminum oxide to produce anorthite. Since anorthite has a coefficient of thermal expansion close to that of silicon, the coefficient of thermal expansion of the ceramic substrate is close to that of a silicon semiconductor integrated circuit, and the silicon semiconductor integrated circuit will not fall off even after long-term use.

[Example 1] Hereinafter, a method for manufacturing a ceramic substrate according to an embodiment of the present invention will be described. First, cordierite (2MgO-2
Prepare powder of AI2O3). Any powder (hereinafter,
The average particle size of the raw material powder (referred to as raw material powder) is approximately 1 micron.

Next, Table 3. 1. Mix the raw material powders in the weights shown in -1 into aluminum alkoxide liquid (81I! degree is about 10W1%). After that, after drying in the air for about 1 hour,
It is fired for about 60 minutes or more in an atmosphere of about 500 degrees Celsius or more. By this calcination, the powder changes from a gel state to consisting of particles coated with 1 cum of aluminum oxide, which is an oxide.

The average film thickness of aluminum oxide covering each particle is determined from the increased weight of the calcined powder. That is, the weight of the powder after calcination is measured, the difference from the weight of the raw material powder is determined, and the increased weight is determined. Since the increased weight is the weight of aluminum oxide covering the powder, the volume of aluminum oxide is calculated from the increased weight. The volume of the raw material powder is similarly determined from the weight of the raw material powder, and the surface area of the entire particle is calculated from the average particle diameter of the particles and the volume. Assuming that aluminum oxide evenly covers the surface area of the entire particle, the average thickness of the aluminum oxide film covering each particle can be calculated by dividing the volume of aluminum oxide by the surface area of the entire particle. can. The average film thickness thus determined is shown in Table 1-1.

No. Powder I AI liquid Average thickness bone 1 10g 5g 0.00
52 10g 10g 0.0
13 10g 110g 0.1
4 10g 243g 0.25
10g 399g O, 361
0792σ 0. 5. Powder 1 is cordierite powder, and A1 liquid is alkoxide liquid of Al and Miniram.

(Hereinafter in the margin) 110- Next, powder coated with aluminum oxide (hereinafter referred to as oxide powder) was mixed with powder of silicate glass (CaO-B2O3 Si 02) containing calcium oxide (hereinafter referred to as oxide powder).
glass powder 1) and an organic binder (e.g. P
VB) in a solvent (e.g., ethanol) with Table 2-1
The slurries 1-1 to 6-3 are obtained by mixing in the proportions shown in . The first number in the slurry number indicates that it was obtained from the powder indicated by the same number in Table 2-1. Note that PVB, PUA, acrylic, etc. may be used as the organic binder. Further, as the solvent, ethanol, toluene, hexane, methyl ethyl ketone, etc. can be used.

(Hereafter, blank space) No. Oxidized powder Glass powder 1 Organic binder No.
σ (- 3-130'70 5 = 12- Next, the slurries 1-1 to 6-3 were made into green sheets 1-1 to 6-3, respectively, by the doctor blade method, and silver thread paste was applied to the surfaces of the green sheets. Screen print a conductor pattern.The dimensions of the green sheet are 5 cm long, 5 cm wide, and 0.5 mm thick.

Also, the conductor pattern has a width of 0. 5mm, length 4
0 mm and 10 microns thick.

The green sheet with the conductive pattern printed thereon was fired for about 20 minutes in an atmosphere at 900 degrees Celsius, and then the coefficient of thermal expansion was measured. The measured coefficients of thermal expansion are shown in Table 3-1 along with the ratio of glass powder l to oxidized powder. Note that the numbers in Table 3-1 indicate that slurries with the same numbers in Table 2-1 were used.

(Margins below) ~No. 13- Content of glass powder 1 Coefficient of thermal expansion - weight %
X 10-6/'C1-1705,9 1-260゛5.6 1-3 50 -5.42-170
5.7 2-2 60 5. 52-3
50 4. 93-1
70 4. 63-2 60
4. 23-3 50
4. 04-1 70 3.
64-2 60 3. 44-3
50 3. 55-1
70 3. 45-2 60
3. 55-3503.4 6-1 70 4.46-2
60 4. 16-3
50 4. 0 As is clear from Table 3-1, the thermal expansion coefficients of the substrates using Slurries 1-1 to 2-2 were far from that of silicon, and the generation of cristobalite could not be sufficiently suppressed. However, the thermal expansion coefficient of the other substrates is close to that of silicon, indicating that the generation of cristobalite was suppressed and anorthite was generated.

Therefore, approximately 0°01 per 1% content of glass powder 1
It is clear that a comparison of micron aluminum oxide is needed.

In the second embodiment of the strategy, (Ca0-Al2O
2-S i 02), and the other steps were the same as in the first example to produce a ceramic substrate. Glass powder (
Ca 0-Al2O2-3i 02) is hereinafter referred to as glass powder 2. Table 4-1, Table 5-1, Table 6-1 are Table 1-1
, Table 2-1, and Table 3-1.

No. Powder I AI liquid Average film thickness = 1 10 5 0.0052 1
0 10 0.013 10 1
10 0.14 10 243
0.25 10 399 0.36
10 792 No. 0.5 Oxidized powder
Glass powder 2 Organic binder 6-130
．． 70 No. 5 Content of glass powder 2 Coefficient of thermal expansion 0 Weight %
7℃1-1 70 6. 31-
2 60 5. 91-3
50 5. 82-1 70
6. 22-2 60
F5. 82-3 50
5.33-1 70 5.03
-2 60 4. 53-3
50 4. 34-1 7
0 4. 04-2 60
3. 74-3 50
3. 75-1 70 3. 6
5-2 60 3. 65-35
03.6 6-1 70 4
．． 76-2 60
4. 26-3 50
4. As is clear from Table 6-1, it is clear that the second example also requires an aluminum oxide comparison of about 0.01 microns per 1% of the glass powder 2 content.

Patent applicant: Mitsubishi Metals Corporation

Claims (5)

[Claims] (1) A raw material powder for producing co-fired ceramic substrates containing a mixed powder of cordierite powder particles coated with aluminum oxide and glass powder that combines with aluminum oxide to form anorthite. (2) The above aluminum oxide is 1% by weight of the above glass powder.
The raw material powder of claim 1, wherein each particle is coated with an average thickness of about 0.01 micron or more. (3) A process of coating each particle of cordierite powder with aluminum oxide, and mixing glass powder that combines with aluminum oxide to produce anorthite with the raw material powder coated with aluminum oxide, and adding an organic binder. In addition, a step of forming a raw material paste, a step of forming a board green sheet with the raw material paste, a step of forming a circuit pattern on the board green sheet, and a step of simultaneously forming the board green sheet and the circuit pattern. A method for manufacturing a ceramic substrate for co-firing, including a step of firing. (4) The above glass powder is (CaO-SiO_2-B_2
A method for manufacturing a ceramic substrate for co-firing according to claim 3, which is represented by O_3). (5) The above glass powder is (CaO-Al_2O_3-S
iO_2) A method for manufacturing a ceramic substrate for co-firing according to claim 3.