JPH0426798B2 - - Google Patents

Description

[Detailed description of the invention]

[Summary] Borosilicate glass with alumina powder added in the range of 5 to 10% by weight is used as a substrate material with a thermal expansion coefficient similar to that of silicon semiconductor ICs and a low dielectric constant. A glass-ceramic multilayer circuit board obtained by making green sheets, laminating them, and firing them under pressure. [Industrial Application Field] The present invention relates to the structure of a glass ceramic substrate suitable for mounting a silicon IC. Information processing technology that rapidly processes large amounts of information has made remarkable progress. In other words, semiconductor devices, which make up the main part of information processing equipment, are increasing in capacity due to miniaturization of unit elements, and the number of elements is even larger than that of conventional ICs and LSIs.
VLSI has been put into practical use. Further, advances in packaging technology have made it possible to directly attach semiconductor chips to wiring boards, and die bonding and flip-chip bonding are now being used. A large number of such semiconductor chips are densely arranged and mounted on a wiring board, but since each semiconductor chip has a large number of terminals, conductor lines are formed on the wiring board on which it is mounted. The number of devices becomes enormous, and a multilayer wiring structure is inevitably required. On the other hand, since the power consumption of a semiconductor chip during operation reaches several watts, the amount of heat generated by a multilayer wiring board on which a large number of semiconductor chips are mounted is also enormous, and therefore heat-resistant insulating materials such as ceramics are used. The present invention relates to the composition of such a multilayer wiring board material. [Prior Art] Ceramics such as glass ceramics and alumina (α-Al ₂ O ₃ ) are used as constituent materials for multilayer wiring boards on which semiconductor chips such as ICs and LSIs are mounted. The reason why ceramics are used here is that they have excellent heat resistance and a coefficient of thermal expansion that is compatible with silicon (Si), which is used to form most semiconductor chips. In other words, the coefficient of thermal expansion of a printed wiring board made of synthetic resin such as polyimide or epoxy is 10 ^-5 /
The value is on the order of ℃, while the thermal expansion coefficient of Si is 3.5×
In contrast, the temperature of ceramics is close to ^{10 -6 /} ℃, which makes it possible to directly mount chips. Next, glass ceramics are more commonly used than alumina for multilayer wiring boards, and the reason for this is that alumina has a high melting point of 2015°C, and requires a firing temperature of about 1800°C, and green sheets with wiring patterns are printed on them. When firing gold (Au)
The melting point of materials with excellent electrical conductivity, such as copper and copper (Cu), is lower than the firing temperature, so such metal materials cannot be used. On the other hand, the firing temperature for glass ceramics is 1000℃.
Accordingly, a conductor pattern made of the above-mentioned metal can be formed. For these reasons, multilayer wiring boards that are used with a large number of semiconductor chips installed are made by screen-printing Au or Cu paste on green sheets made of glass ceramics to form wiring patterns, and then laminating these. After being integrated, it is fired. Typical glass-ceramics are made of borosilicate glass with alumina added, and because they are composed of aggregates of microcrystals, their mechanical strength is significantly improved. There is a problem that the amount of glass is increasing more than that of glass. In other words, as the speed of information processing increases, the frequency of signals has reached the level of light, but the multilayer substrate on which electronic circuits that process high-speed electrical signals are formed has a delay time τ of electrical signals as small as possible. It is necessary for the characteristic impedance of an electronic circuit to be large and for crosstalk between multilayer wiring to be small. To achieve this, it is necessary that the dielectric constant ε of the material used be small, as is clear from the following equation. τ≒3.33ε ^1/2 (n seconds/m) Z ₀ = 60/ε ^1/2・l _o 5.98b/π (0.8w+t) However, b is the thickness of the board, w is the width of the wiring pattern, t is the wiring Pattern Thickness However, since conventional glass ceramics are composed of borosilicate glass containing about 50% by weight of alumina, the dielectric constant is as high as 5.5 to 5.6, and there has been a desire to reduce this. [Problems to be Solved by the Invention] As described above, it is necessary to form a ceramic multilayer substrate that forms an electronic circuit that processes high-speed signals using glass ceramics with a low dielectric constant. The challenge is how to maintain the composition ratio of alumina to form a multilayer circuit board. [Means for solving the problem] The above problem is solved by using borosilicate glass powder and alumina powder as the main ingredients, adding a binder and a solvent to these ingredients, kneading them to make a green sheet, and adding a conductor to this green sheet. A multilayer circuit board made by printing a paste to make a conductor pattern, laminating the green sheets, applying pressure and firing, is characterized in that the amount of alumina added to the borosilicate glass powder is 5 to 10% by weight. This problem can be solved by constructing a glass-ceramic multilayer circuit board. [Function] The requirements for a multilayer circuit board on which electronic circuits that process high-speed electrical signals are formed are that it be made of a material with a low dielectric constant ε, that its coefficient of thermal expansion is compatible with that of Si, and that it has good mechanical strength. The firing temperature of the green sheet is below 1000℃, which is compatible with the firing conditions of the conductive paste. Here, as mentioned earlier, materials with a high dielectric constant of 5.5 to 6.5 have been used because the alumina content is about 50%. Therefore, in order to lower the dielectric constant, the alumina content should be reduced within the range that satisfies the above conditions. That is, the dielectric constant ε of alumina is 10, while the dielectric constant of borosilicate glass is 4.1 to 4.8, depending on the composition ratio of the constituent materials. Therefore, the composite dielectric constant is determined by the quantitative ratio of the two, and as the amount of alumina added decreases, the dielectric constant decreases, and finally reaches the dielectric constant of borosilicate glass. Furthermore, the coefficient of thermal expansion should change linearly as the amount added decreases, approaching that of borosilicate glass. However, when borosilicate glass containing alumina is heated to about 1000℃,
It was found that when the amount of alumina added was less than about 5%, the amount of alumina increased abnormally when heat treated. FIGS. 1 and 2 show the relationship between the thermal expansion coefficient and the dielectric constant of glass ceramics prepared by adding alumina to borosilicate glass made of raw materials having the composition shown in the table.

〔Example〕

The composition is 70% SiO ₂ and 26% B ₂ O ₃ by weight.
95 parts by weight of borosilicate glass powder consisting of 1% Al ₂ O ₃ , 1.5% Na ₂ O, and 1.5% K ₂ O was added with 3 μm particle size.
Add 5 parts by weight of Al ₂ O ₃ powder, add 10 parts by weight of polyvinyl butyral (abbreviated as PVB) as a binder and 110 parts by weight of acetone as a solvent, mix well using a ball mill, and then mix using a doctor blade method. A green sheet with a thickness of 300 μm was formed. After punching out this green sheet into 100 mm squares and drilling through holes, we screen printed a conductive paste made of Cu to form a wiring pattern, aligned it, and stacked 10 layers.
They were bonded and integrated at a temperature of 130° C. and then fired in a nitrogen (N ₂ ) stream at a temperature of 1000° C. for 4 hours to form a multilayer ceramic circuit board. As a result of the measurements, the dielectric constant of this substrate was as small as 4.2, and the coefficient of thermal expansion was 3×10 ^-6 /°C, which was close to that of the Si substrate. [Effects of the Invention] As described above, by carrying out the present invention, it is possible to form a multilayer circuit board that has a thermal expansion coefficient close to that of a Si substrate and has a low dielectric constant and is suitable for high-speed signal processing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the coefficient of thermal expansion and the amount of alumina added, and FIG. 2 is a diagram showing the relationship between the dielectric constant and the amount of alumina added.

Claims (1)

[Claims] 1 The main ingredients are borosilicate glass powder and alumina powder, a binder and a solvent are added to the ingredients, kneaded to make a green sheet, a conductive paste is printed on the green sheet to create a conductive pattern, and the green sheet is 1. A glass-ceramic multilayer circuit board formed by laminating, pressurizing and firing, wherein the amount of alumina added to the borosilicate glass powder is 5 to 10% by weight.