JP2002050875A - Low-temperature sintered ceramic multilayer substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce resistance change over aging of a thick-film resistor (occurrence/expansion of micro crack) even if an inner-layer wiring conductor is wired in a region directly below the thick-film resistor, related to a low- temperature sintered ceramics multilayer substrate where the thick-film resistor is formed on the substrate surface. SOLUTION: The relationship between a thermal expansion coefficient T1 of an inner-layer wiring conductor 13, a thermal expansion coefficient T2 of a ceramics layer 22, and a thermal expansion coefficient T3 of a thick-film resistor 24 of a low-temperature sintered ceramics multilayer substrate 21 is T1>T2 while 2.5×10-6/ deg.C>=T2-T3>=0.5×10-6/ deg.C. The thick-film resistor 24 has, as main components, RuO2 and SiO2-B2O3-K2O glass. Related to the composition of the glass, 60 wt.%<=SiO2<=85 wt.%, 15 wt.%>=B2O3<=40 wt.%, 0.1 wt.%<=K2O<=10 wt.%, impurity >=3 wt.%. The ceramics layer 22 is formed by mixing a CaO-Al2O3-SiO2-B2O3 glass with Al2O3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low temperature fired ceramic multilayer substrate having a thick film resistor formed on a substrate surface.

[0002]

2. Description of the Related Art A low-temperature fired ceramic multilayer substrate fired at 800 ° C. to 1000 ° C. has a lower dielectric constant than a alumina substrate fired at around 1600 ° C., enables a high-speed signal processing, and has a high performance. There is an advantage that an Ag-based conductor having a low conduction resistance and a low-melting-point metal such as Cu can be used as a wiring conductor co-fired, and the demand has been increasing in recent years. As shown in FIG. 8, this low-temperature fired ceramic multilayer substrate has an inner layer wiring conductor 11 formed in the inner layer of the substrate and a thick film resistor 12 formed on the substrate surface. As the thick film resistor 12, for example, RuO ₂
A thick film resistor pattern is printed using a system thick film resistor paste, which is fired at around 900 ° C. is used. In general, the resistance of the fired thick film resistor 12 varies, so that after firing, the thick film resistor 12 is trimmed by a laser trimming method or the like to form a trimming groove 14 (see FIG. 9), and the resistance value is increased. To adjust.

[0003]

The recent demand for high-density wiring requires that the distance between the inner wiring conductors 11 be narrowed. In many cases, the wiring of the parts is increasing. However, this configuration has a drawback that the microcracks generated around the trimming groove 14 during the trimming of the thick film resistor 12 are easily extended in a relatively short period of time. Less than,
The reason will be described.

Conventionally, the thermal expansion coefficient of the thick film resistor 12 is determined by the thermal expansion coefficient of the low-temperature fired ceramic 13 (for example, 5.8 × 1).
0 ⁻⁶ / ° C.), but the thermal expansion coefficient of the inner-layer wiring conductor 11 is considerably larger than the thermal expansion coefficient of the low-temperature fired ceramic 13 (for example, the thermal expansion coefficient of an Ag 100 wt% conductor is 19 × 10 ^−6). / ° C). For this reason, the stress distribution of the fired low-temperature ceramic 13 is such that a compressive stress is generated due to shrinkage of the inner wiring conductor 11 in a region directly above the inner wiring conductor 11, and a compressive stress is generated in a region between the inner wiring conductors 11 on both sides thereof. Since the distance between the inner wiring conductors 11 is widened by the shrinkage of the inner wiring conductor 11, the tensile stress is generated.

On the other hand, since the thick-film resistor 12 receives a tensile force and a compressive force from the low-temperature fired ceramic 13, the stress distribution of the thick-film resistor 12 becomes the same as the stress distribution of the low-temperature fired ceramic 13. In the body 12, the inner layer wiring conductor 11
The tensile stress acts on the region between them. in this way,
When a tensile stress is applied to the thick film resistor 12, micro cracks are easily generated around the trimming groove 14 due to thermal strain during laser trimming, and the micro cracks are extended in a relatively short time due to the tensile stress. Cheap. The occurrence and extension of such micro cracks
The resistance value of the thick film resistor 12 is changed over time, which causes deterioration of the electrical characteristics of the circuit.

In order to avoid this problem, the thick film resistor 1
It is conceivable to design such that the inner layer wiring conductor 11 is not wired in the area immediately below the second wiring conductor 2. However, in this case, the area immediately below the thick film resistor 12 cannot be used as a wiring space for the inner layer wiring conductor 11. The wiring density decreases, and the demand for high-density wiring cannot be satisfied.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and accordingly, it is an object of the present invention to provide a semiconductor device in which an internal wiring conductor is provided in a region immediately below a thick film resistor. A low-temperature fired ceramic multilayer substrate that can reduce the time-dependent change (generation and extension of microcracks) of the thick film resistor and can satisfy the demand for high-density wiring while securing the resistance stability of the thick-film resistor. It is in.

[0008]

The present inventors analyzed the stress generated in the thick film resistor by variously changing the thermal expansion coefficient of the inner layer wiring conductor, the low temperature fired ceramic, and the thick film resistor. In order to achieve the above object, the relationship between the thermal expansion coefficient T1 of the inner wiring conductor, the thermal expansion coefficient T2 of the low-temperature fired ceramic, and the thermal expansion coefficient T3 of the thick film resistor is as follows. It turned out that it should be set to. T1> T2 and 2.5 × 10 ⁻⁶ /°C≧T2−T3≧0.5×10 ⁻⁶ / ° C

In the conventional structure, the thermal expansion coefficient T1 of the inner layer wiring conductor is larger than the thermal expansion coefficient T2 of the low-temperature fired ceramic, but the thermal expansion coefficient T2 of the low-temperature fired ceramic and the thermal expansion coefficient T3 of the thick film resistor are different. Were almost the same, and tensile stress was generated in the thick film resistor.

On the other hand, as in the present invention, the thermal expansion coefficient T3 of the thick film resistor is changed to the thermal expansion coefficient T
If it is smaller than 2, compressive stress will act on the thick-film resistor from the low-temperature fired ceramics without the influence of the inner layer wiring conductor. Therefore, the thermal expansion coefficient T of the thick film resistor
3 is smaller than the thermal expansion coefficient T2 of the low-temperature fired ceramic, even if a tensile stress acts on the low-temperature fired ceramic from the inner layer wiring conductor, the difference in the thermal expansion coefficient between the low-temperature fired ceramic and the thick film resistor results. The compressive stress can reduce or cancel the tensile stress acting on the thick film resistor from the inner wiring conductor via the low-temperature fired ceramic.

According to the test results of the present inventors, T 2 −T
If 3 ≧ 0.5 × 10 ⁻⁶ / ° C., the tensile stress acting on the thick-film resistor can be reduced to a level that has little effect in practical use, and the resistance value of the thick-film resistor over time can be reduced. Changes (generation / extension of microcracks) can be reduced.

[0012] In this case, as T2-T3 is increased,
The tensile stress acting on the thick film resistor is reduced, and T2-
If T3 is further increased, the stress acting on the thick film resistor becomes only the compressive stress. Therefore, as T2 -T3 is increased, the effect of preventing the generation and extension of microcracks increases, and Resistance stability is improved. However, if T2 -T3 becomes too large, the compressive stress acting on the thick film resistor becomes too large, and the periphery of the trimming groove is chipped by the compressive stress during laser trimming (chipping), resulting in a significant decrease in yield. .

According to the test results of the present inventors, T 2 -T
If 3 ≦ 2.5 × 10 ⁻⁶ / ° C., it is confirmed that the compressive stress acting on the thick film resistor does not become too large, and that no chipping occurs during laser trimming.

In general, a thick film resistor is generally made of a mixture of Ru oxide and glass because of its temperature characteristics and wide range of resistance value. However, the glass used in the conventional thick film resistor contains lead (Pb) for the following reasons.

(1) The electric resistance of the thick film resistor is made up of both the resistance due to the contact between the fine powders of the conductive material (Ru oxide) and the resistance obtained through a thin glass film between the conductive materials. . However, when forming a high-resistance thick-film resistor of 100 kΩ / □ or more, the resistance obtained through a glass film between the conductive materials becomes dominant in order to reduce the amount of the conductive material. The resistance value is easy to change. As a countermeasure for this, by using a Ru composite oxide such as Pb ₂ Ru ₂ O ₆ or Bi ₂ Ru ₂ O ₇ having a higher resistivity than RuO ₂ as a conductive substance, and increasing the compounding ratio of the conductive substance, A method of increasing the ratio of electric conduction due to contact with a conductive substance has been adopted.

However, the Ru composite oxide is partially decomposed during the firing process, and makes the characteristics of the thick film resistor unstable.
For example, in the case of Bi ₂ Ru ₂ O ₇ , the decomposition is performed as follows. Bi ₂ Ru ₂ O ₇ → 2RuO ₂ + Bi ₂ O _{3 By} this decomposition, RuO ₂ and Bi ₂ Ru ₂ O ₇ are contained in the thick film resistor.
And are mixed. In order to prevent such decomposition, it is necessary to use PbO-containing glass for the glass of the thick film resistor.

(2) When PbO is contained in the glass of the thick film resistor, characteristics such as the melting point and the thermal expansion coefficient of the glass can be easily adjusted, and the characteristics of the thick film resistor can be easily adjusted.
However, due to environmental concerns, the use of lead is not preferred,
It is desirable to use a thick film resistor that does not use lead.

Therefore, the thick film resistor is made of a mixture of RuO ₂ and SiO ₂ —B ₂ O ₃ —K ₂ O glass, and the composition of this glass is as follows. good. 60 wt% ≦ SiO ₂ ≦ 85 wt% 15 wt% ≦ B ₂ O ₃ ≦ 40 wt% 0.1 wt% ≦ K ₂ O ≦ 10 wt% Impurities ≦ 3 wt%

Thick film resistors are usually 900 ° C.
It is fired below, and is generally often fired at about 850 ° C. This is because a low-melting-point metal such as Ag or Au is used as the surface conductor of the ceramic substrate.
_This is to prevent evaporation of ₂ . In order to fire the thick film resistor at 850 ° C., it is desirable that the glass included in the thick film resistor has a transition point of 650 ° C. or less.

The SiO ₂ -B ₂ contained in the thick film resistor
With the above composition, the O ₃ -K ₂ O glass has a glass transition point of 650 ° C. or less and can be fired at 850 ° C. In this case, since K ₂ O in glass plays a role of lowering the glass transition point, if K ₂ O is less than 0.1 wt%, the glass transition point becomes higher than 650 ° C. At 850 ° C. is difficult. Other K ₂ O, Na ₂ O, it is possible to lower the glass transition point in the Li ₂ O, etc., Na ₂ O and Li ₂ O
Is used, since the temperature coefficient of resistance greatly changes to the negative side, the temperature characteristics of the thick film resistor deteriorate. In this regard,
If K ₂ O is used, the glass transition point can be lowered without deteriorating the temperature characteristics of the thick film resistor.

However, if the amount of K ₂ O in the glass is too large, the coefficient of thermal expansion of the glass becomes large.
It is not preferable to increase the amount of ₂ O unnecessarily.
If the amount of K ₂ O in the glass is 10 wt% or less,
The glass has a thermal expansion coefficient of 6.0 × 10 ⁻⁶ / ° C. or less,
The thermal expansion coefficient T3 of the thick film resistor mixed with RuO ₂ (coefficient of thermal expansion: 5 to 6 × 10 ⁻⁶ / ° C.) is 6.0 × 10 ⁻⁶ / ° C. or less. As a result, the thermal expansion coefficient T3 of the thick film resistor is made smaller than the thermal expansion coefficient T2 of the low-temperature fired ceramic, and 2.5 × 10 ^-6 / ° C ≧ T2 -T3 ≧ 0.5 × 10 ^-6
/ ° C can be satisfied.

Further, as a low-temperature firing ceramic, CaO-Al ₂ O ₃ -SiO ₂ -B ₂ O ₃
It is preferable to use a mixture of glass and Al ₂ O ₃ . Low-temperature fired ceramics of this composition can be fired at a high speed, have characteristics such as a low dielectric constant (high-speed signal), a low coefficient of thermal expansion (direct bonding of Si chips), and have high heat resistance at the end of sintering. Because it generates sites, it is also strong in heat treatment. Therefore, even if the thick film resistor is post-fired on the sintered ceramic substrate, the characteristics of the ceramic substrate do not deteriorate. Of course, the ceramic substrate and the thick film resistor can be simultaneously fired.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure of a low-temperature fired ceramic multilayer substrate 21 according to an embodiment of the present invention will be described with reference to FIGS.

The ceramic layer 22 of the low-temperature fired ceramic multilayer substrate 21 is made of CaO--Al ₂ O ₃ --SiO ₂ --B ₂ O
₃ series glass: 50 to 65 wt% (preferably 60 wt%
%) And Al ₂ O ₃ : 50 to 35 wt% (preferably 40 wt%).
(wt.%) and a plurality of green sheets obtained by tape-forming a slurry of the low-temperature fired ceramic by a doctor blade method. Other low-temperature fired ceramics include, for example, MgO—Al ₂ O ₃ —SiO ₂ —B ₂
A mixture of an O ₃ -based glass powder and an Al ₂ O ₃ powder, or a mixture of a SiO ₂ -B ₂ O ₃ -based glass powder and an Al ₂ O ₃ powder, a crystallized glass, or the like may be used. In short, a low-temperature fired ceramic that can be fired at 800 to 1000 ° C. may be used.

An inner wiring conductor 23 is formed in an inner layer of the low-temperature fired ceramic multilayer substrate 21. This inner layer wiring conductor 23 is made of A such as Ag, Ag / Pd, Ag / Pt or the like.
A paste of a low-melting-point metal such as a g-based conductor, an Au-based conductor, or a Cu-based conductor is printed on the ceramic layer 22 (green sheet) and fired simultaneously with the ceramic layer 22. Further, via holes (not shown) for electrically connecting the layers are formed in the ceramic layer 22 of each layer, and the via holes are filled with the paste of the low-melting-point metal and fired simultaneously.

On the surface of the low-temperature fired ceramic multilayer substrate 21, a thick film conductor such as an electrode pattern 25 or a wiring pattern for connecting the thick film resistor 24 is printed and fired. Thick film conductors such as the electrode pattern 25 are made of Ag, Ag / P
d. A paste of a low melting point metal such as an Ag-based conductor such as Ag / Pt, an Au-based conductor, or a Cu-based conductor is printed and fired. The thick film conductor such as the electrode pattern 25 may be printed and fired after the low temperature fired ceramic multilayer substrate 21 is fired, or may be fired simultaneously with the low temperature fired ceramic multilayer substrate 21.

Further, on the surface of the low-temperature fired ceramic multilayer substrate 21, a thick film resistor 24
Are printed and fired. This thick film resistor 24 is made of Ru
O ₂ and SiO ₂ —B ₂ O ₃ —K ₂ O glass are the main components, and the composition of SiO ₂ —B ₂ O ₃ —K ₂ O glass is 60
wt% ≦ SiO ₂ ≦ 85 wt%, 15 wt% ≦ B ₂ O ₃
≦ 40 wt%, 0.1 wt% ≦ K ₂ O ≦ 10 wt%, and impurities ≦ 3 wt%. This thick film resistor 24 is
Printing and firing of thick film conductors such as electrode pattern 25
It may be fired or fired simultaneously with the thick film conductor. Since the thickness of the thick film resistor 24 after firing varies, the thickness of the thick film resistor 24 is trimmed by laser trimming or the like after firing to form a trimming groove 26 (see FIG. 2), and the resistance is adjusted. I am trying to do it.

The glass contained in the thick film resistor 24 is as follows.
The glass is not limited to SiO ₂ —B ₂ O ₃ —K ₂ O glass, and a glass having another composition may be used, or a low conductive component other than RuO ₂ may be used.

At least a part of the inner-layer wiring conductor 23 is wired in a region immediately below the thick film resistor 24. Furthermore,
In the present embodiment, in order to reduce the change with time of the resistance value of the thick film resistor 24 (the occurrence and extension of microcracks), the thermal expansion coefficient T1 of the inner wiring conductor 23 and the thermal expansion coefficient T2 of the ceramic layer 22 are determined. Thermal expansion coefficient T of the film resistor 24
The relationship with 3 is set as follows.

T1> T2 and 2.5 × 10 ⁻⁶ / ° C. ≧
At T2-T3 ≥ 0.5 x 10 ^-6 / ° C, the tensile stress that causes the change of the resistance value of the thick-film resistor 24 with time (generation / extension of microcracks) depends on the thickness of the inner-layer wiring conductor 23. It changes depending on the length t, width a, and interval b.
It also changes depending on the thickness h of the ceramic layer 22. The present inventors conducted a test for examining this relationship, and the test results are shown in FIGS.

The stress measurement data shown in FIGS. 3 to 6 show that the thermal expansion coefficient T2 of the ceramic layer 22 and the thermal expansion coefficient T3 of the thick film resistor 24 are the same (T2 = T3 = 5.8.times.10.sup.- ⁶ / .degree. C.). )
And the stress acting on the thick film resistor 24 of the substrate manufactured according to the standard wiring rule of Table 1 below is set to a standard value (100
%), The stress acting on the thick film resistor 24 of each sample substrate was measured, and the plus side is the tensile stress and the minus side is the compressive stress.

[0032]

[Table 1]

FIG. 3 shows the relationship between the thickness t of the inner wiring conductor 23 and the stress acting on the thick film resistor 24 (T2 = T3 = 5.8.times.10.sup.- ⁶ / .degree. C.). As the thickness t of the inner-layer wiring conductor 23 increases, the compressive force of the entire inner-layer wiring conductor 23 increases, and the tensile stress acting on the ceramic layer 22 from the inner-layer wiring conductor 23 increases. The tensile stress acting on the film resistor 24 increases.

FIG. 4 shows the relationship between the width a of the inner wiring conductor 23 and the stress acting on the thick film resistor 24 (T2 = T3 = 5.8 × 10 ^-6 / ° C.). As the width a of the inner-layer wiring conductor 23 increases, the compressive force of the entire inner-layer wiring conductor 23 increases, and the tensile stress acting on the ceramic layer 22 from the inner-layer wiring conductor 23 increases. The tensile stress acting on the resistor 24 increases.

FIG. 5 shows the relationship between the distance b between the inner-layer wiring conductors 23 and the stress acting on the thick film resistor 24 (T2 = T3 = 5.8 × 10 ^-6 / ° C.). When the distance b between the inner wiring conductors 23 is in the range of 0.2 to 0.3 mm (a range close to the value of the standard wiring rule), the tensile stress acting on the thick film resistor 24 becomes almost maximum, and is 0.2 mm or less. In the range, as the distance b becomes smaller, the tensile stress becomes smaller, and in the range of 0.3 mm or more, as the distance b becomes larger, the tensile stress becomes smaller.

FIG. 6 shows the relationship between the thickness h of the ceramic layer 22 and the stress acting on the thick film resistor 24 (T2 = T3 = 5.8.times.10.sup.- ⁶ / .degree. C.). Since the mechanical strength of the ceramic layer 22 increases as the thickness h of the ceramic layer 22 increases, the tensile stress acting on the thick-film resistor 24 from the inner wiring conductor 23 via the ceramic layer 22 decreases.

As apparent from the stress measurement data shown in FIGS. 3 to 6, the thermal expansion coefficient T2 of the ceramic layer 22 and the thermal expansion coefficient T3 of the thick film resistor 24 are the same (T2 = T3).
In the case of, the stress acting on the thick film resistors 24 of all the sample substrates becomes the tensile stress. As described above, when the tensile stress is applied to the thick film resistor 24, micro cracks are easily generated around the trimming groove 26 due to thermal strain during laser trimming, and the micro cracks are generated for a relatively short time by the tensile stress. Easy to stretch between. The occurrence and extension of such microcracks cause the resistance value of the thick-film resistor 24 to change with time, causing deterioration of the electrical characteristics of the circuit.

Therefore, in the present embodiment, the inner layer wiring conductor 2
3. Thermal expansion coefficient T of ceramic layer 22 and thick film resistor 24
By optimizing the relationship among 1, T2, and T3, the tensile stress acting on the thick-film resistor 24 is reduced to a level at which the effect is practically small, and the resistance value of the thick-film resistor 24 changes with time. (Generation and extension of microcracks). The present inventors have calculated thermal expansion coefficients T1, T2, T3.
A test was conducted to consider the appropriate relationship between the two, and the test results will be described below.

FIG. 7 shows the thermal expansion coefficient T3 of the thick film resistor 24.
And a relationship between the stress acting on the thick film resistor 24 and the stress acting on the thick film resistor 24. In this test, t = 0.015 mm, h =
0.10 mm, a = 1.0 mm sample substrate, and t =
0.010 mm, h = 0.15 mm, a = 0.15 mm
The relationship between the coefficient of thermal expansion T3 of the thick film resistor 24 and the stress acting on the thick film resistor 24 was measured for each of the sample substrates. The coefficient of thermal expansion T2 of the ceramic layer 22 of each sample substrate is 5.8.times.10.sup.- ⁶ / .degree.

As apparent from the test results, the thermal expansion coefficient T3 of the thick-film resistor 24 must be reduced by reducing the thermal expansion coefficient T3 of the ceramic layer 22 in order to reduce the tensile stress which causes the micro-cracks to occur and extend in the thick-film resistor 24. Must be smaller than the thermal expansion coefficient T2 of the ceramic layer 22.
2 is 5.8 × 10 ⁻⁶ / ° C., in order to reduce the tensile stress acting on the thick-film resistor 24 to a practically small level, the thermal stress of the thick-film resistor 24 must be reduced. The expansion coefficient T3 needs to be at least 5.5 × 10 ⁻⁶ / ° C. or less, more preferably 4.5 × 10 ⁻⁶ / ° C. or less.

The inventors of the present invention have prepared a sample substrate having the structure shown in Table 2 below, which shows the thermal expansion coefficients T1, T2, T3 of the inner wiring conductor 23, the ceramic layer 22, and the thick film resistor 24.
Was changed to measure the maximum value of the rate of change in the resistance value of the thick film resistor 24 and the presence or absence of chipping during laser trimming. The measurement results are shown in Tables 3 and 4.

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

The ceramic layer 22 of each sample substrate is made of C
_{aO-Al 2 O 3 -SiO 2} -B 2 O 3 based glass (60
wt%) and Al ₂ O ₃ (formed of a low-temperature fired ceramic mixed with 40 wt%) and, CaO-Al ₂ O ₃ -SiO
By changing the composition of ₂ -B ₂ O ₃ based glass was adjusted thermal expansion coefficient T2 of the ceramic layer 22.

The inner wiring conductor 23 of each sample substrate
g (100 wt%) or a mixture of Ag and Ag-Pd. In the case of Ag (100 wt%), the coefficient of thermal expansion T1 is 19 × 10 ⁻⁶ / ° C.

The thick film resistor 24 of each sample substrate is made of Ru
It is formed from a mixture of O ₂ and SiO ₂ —B ₂ O ₃ —K ₂ O glass, and by changing the mixing ratio of RuO ₂ and glass or changing the glass composition, the heat of the thick film resistor 24 is The expansion coefficient T3 was adjusted. The size of the thick film resistor 24 is a length 2
mm and a width of 1 mm. The trimming condition of the thick film resistor 24 is such that the laser output is 1.0 W and the trimming speed is 2
0 mm / sec. After the trimming, each sample substrate was immersed in liquid nitrogen three times, and the rate of change in the resistance value of the thick film resistor 24 was measured.

In both the embodiment shown in Table 3 and the comparative example shown in Table 4, the thermal expansion coefficient T1 of the inner layer wiring conductor 23 is larger than the thermal expansion coefficient T2 of the ceramic layer 22. Regarding the difference (T2 -T3) from the coefficient of thermal expansion T3 of the thick film resistor 24, in the embodiment of Table 3, 2.5
× 10 ⁻⁶ / ° C ≧ T 2 −T 3 ≧ 0.5 × 10 ⁻⁶ / ° C. In the comparative example of Table 4, T 2 −T 3 = 3.0 × 1
0 ⁻⁶ / ° C., or 0, or −0.5 × 10 ⁻⁶ / ° C.

When the thermal expansion coefficient T3 of the thick film resistor 24 is made smaller than the thermal expansion coefficient T2 of the ceramic layer 22, a compressive stress is applied from the ceramic layer 22 to the thick film resistor 24 without the influence of the inner wiring conductor 23. Will work. Therefore, the thermal expansion coefficient T3 of the thick film resistor 24 is
2 is smaller than the thermal expansion coefficient T2, the tensile stress acts on the ceramic layer 22 from the inner-layer wiring conductor 23.
Reduction or cancellation of the tensile stress acting on the thick-film resistor 24 from the inner-layer wiring conductor 23 via the ceramic layer 22 by the compressive stress due to the difference in the coefficient of thermal expansion between the ceramic layer 22 and the thick-film resistor 24. Can be.

In the embodiment shown in Table 3, T2−T3 ≧ 0.5 ×
Since the temperature is 10 ⁻⁶ / ° C., the tensile stress acting on the thick film resistor 24 from the inner wiring conductor 23 via the ceramic layer 22 becomes sufficiently small. As a result, the maximum value of the rate of change of the resistance value of the thick film resistor 24 was 0.6% or less, and it was confirmed that the change with time of the resistance value of the thick film resistor 24 (generation and extension of microcracks) was small. .

Further, in the embodiment shown in Table 3, T2-T3 ≤
Since it was 2.5 × 10 ⁻⁶ / ° C., the compressive stress acting on the thick film resistor 24 did not become too large, and chipping caused by the compressive stress around the trimming groove 26 during laser trimming did not occur.

On the other hand, in the comparative example of Table 4, T2-T
In the case of 3 = 3.0 × 10 ⁻⁶ / ° C., since a large compressive stress acts on the thick film resistor 24 from the ceramic layer 22, the maximum change rate of the resistance value of the thick film resistor 24 is 0.1. %, And the change with time of the resistance value of the thick film resistor 24 (generation and extension of microcracks) is very small.
The chipping occurred around the trimming groove 26 at the time of laser trimming because the compressive stress acting on the groove became too large.

T2-T3 = 0 or -0.5 × 10
^In the case of ⁻⁶ / ° C., the tensile stress acting on the thick-film resistor 24 becomes large, so that the maximum value of the rate of change of the resistance value of the thick-film resistor 24 becomes 1.1 to 3.5%. The change with time of the resistance value of the film resistor 24 (generation and extension of microcracks) is large.

As is clear from the above test results, T1
> T2 and 2.5 × 10 ⁻⁶ / ° C ≧ T2−T3 ≧ 0.
At 5 × 10 ⁻⁶ / ° C., even if the inner-layer wiring conductor 23 is wired in a region immediately below the thick-film resistor 24, the resistance value of the thick-film resistor 24 changes over time (generation / extension of microcracks) Can be reduced, and the demand for high-density wiring can be satisfied while the resistance stability of the thick film resistor 24 is secured.

The present invention can be applied irrespective of the type of the thick-film resistor 24. As the glass contained in the RuO ₂ -based thick-film resistor 24 as in this embodiment, SiO ₂ —B ₂ O ₃ —
If K ₂ O glass is used, the firing temperature of the thick film resistor 24 can be reduced and the thermal expansion can be reduced without using a Pb component, and a high-quality Pb-free thick film resistor 24 can be formed. Can be.

The RuO film included in the thick film resistor 24 is
_It is good to use ₂ having a specific surface area of 30 to 80 m ² / g. That is, in RuO ₂ , as the specific surface area becomes smaller, charges are more likely to concentrate, and the ESD (electrostatic
discharge) characteristics tend to decrease. According to the test results of the present inventors, if the specific surface area of RuO ₂ is 30 m ² / g or more, preferable ESD characteristics can be secured. However, the specific surface area of RuO ₂ exceeds 80 m ² / g, the oxidation catalysis of RuO ₂ and becomes stronger, because organics which may be pyrophoric, the specific surface area of RuO ₂ or less 80 m ² / g Is preferred.

[0057] In addition, on the surface of RuO _2, RuO _2: 10
0.8 to 4 wt% of K ₂ O may be attached to 0 wt%. K ₂ O on the surface of RuO ₂ is SiO ₂ -B ₂
Improves the wettability between O ₃ -K ₂ O glass and RuO ₂ ,
It stabilizes conduction obtained through glass, reduces the change in resistance value (dependence on firing temperature) due to the change in firing temperature, and also plays a role in preventing charge concentration and improving ESD characteristics. .

Further, an additional glass containing an oxide of a transition metal and B ₂ O ₃ may be added to the thick film resistor 24. The borate containing the transition metal in the added glass has conductivity due to electron conduction and exhibits semiconductor properties. Therefore, when the surge voltage is applied, the added glass serves to prevent the charges from being locally concentrated and to prevent the glass of the thick film resistor 24 from being broken. From this characteristic, when the sheet resistance value is large, the effect of adding the added glass increases. However, since the added glass exhibits semiconductor properties, the temperature coefficient of resistance shifts to a negative value. Therefore, in order to satisfy both the temperature coefficient of resistance and the ESD characteristics, for example, in the case of a thick film resistor of 100 kΩ / □, it is preferable that the addition amount of the additional glass is 3 to 15 wt%.

Further, the thick film resistor 24 has 5 wt%
The following transition metal oxides may be added. Thick film resistor 2
If the addition amount of the transition metal oxide to No. 4 is 5 wt% or less, the temperature coefficient of resistance of the thick film resistor 24 can be arbitrarily adjusted by adjusting the addition amount of the transition metal oxide.

The SiO ₂ − in the thick film resistor 24 is
1 to 20 wt% ZrO ₂ particles in B ₂ O ₃ -K ₂ O glass
% May be added. The ZrO ₂ particles have higher thermal conductivity than glass, and at the firing temperature (900 ° C. or lower) of the thick film resistor 24, the ZrO ₂ particles and the SiO ₂ —B ₂
Since it does not react with O ₃ -K ₂ O glass, SiO ₂ -B
_{If an} appropriate amount of ZrO ₂ particles is added to the ₂ O ₃ —K ₂ O glass, the heat conductivity of the thick film resistor 24 is increased without deteriorating the electrical characteristics of the thick film resistor 24 and the heat dissipation is improved. And the power durability can be improved.

[0061]

As is clear from the above description, according to the low-temperature fired ceramic multilayer substrate of the first aspect of the present invention, the thermal expansion coefficient T1 of the inner wiring conductor and the thermal expansion coefficient of the low-temperature fired ceramic (ceramic layer). The relationship between T2 and the thermal expansion coefficient T3 of the thick film resistor is defined as T1> T2 and ^{2.5.times.10.sup.-6.}
/ ° C ≧ T 2 −T 3 ≧ 0.5 × 10 ⁻⁶ / ° C. Therefore, even if an inner layer wiring conductor is wired in a region directly below the thick film resistor, the change over time in the resistance value of the thick film resistor ( The generation and extension of microcracks) can be reduced, and the demand for high-density wiring can be satisfied while securing the resistance stability of the thick-film resistor.

Further, according to claim 2, the thick film resistor is made of Ru.
It is composed of a mixture of O ₂ and SiO ₂ —B ₂ O ₃ —K ₂ O glass, and the amount of K ₂ O in the glass is 0.1 wt% ≦ K
_{Since 2} O ≦ 10 wt%, the glass transition point can be lowered without deteriorating the temperature characteristics of the thick film resistor, and the thick film resistor can be fired at 850 ° C. Is made smaller than the thermal expansion coefficient T2 of the low-temperature fired ceramic by 2.5 × 10 ^-6 /
The condition of ° C ≧ T2−T3 ≧ 0.5 × 10 ⁻⁶ / ° C can be satisfied.

[0063] In claim 3, the low-temperature fired ceramic. Thus a mixture of _{CaO-Al 2 O 3 -SiO 2} -B 2 O 3 glass and Al ₂ O _3, a low dielectric constant (signal Speed), low thermal expansion coefficient (direct bonding property of Si chip) and the like, and to generate anorthite having high heat resistance at the end of sintering. Even if the film resistor is post-baked, the characteristics of the ceramic substrate do not deteriorate.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a low-temperature fired ceramic multilayer substrate showing an embodiment of the present invention.

FIG. 2 is a plan view of a thick film resistor and its peripheral portion.

FIG. 3 is a graph showing a relationship between a thickness t of an inner wiring conductor and a stress acting on a thick film resistor.

FIG. 4 is a graph showing the relationship between the width a of the inner wiring conductor and the stress acting on the thick film resistor.

FIG. 5 is a graph showing the relationship between the distance b between inner wiring conductors and the stress acting on the thick film resistor.

FIG. 6 is a graph showing a relationship between a thickness h of a ceramic layer and a stress acting on a thick film resistor.

FIG. 7 is a graph showing the relationship between the thermal expansion coefficient T3 of a thick film resistor and the stress acting on the thick film resistor.

FIG. 8 is a longitudinal sectional view of a main part of a conventional low-temperature fired ceramic multilayer substrate.

FIG. 9 is a plan view of a conventional thick film resistor and its peripheral portion.

[Explanation of symbols]

21: low temperature fired ceramic multilayer substrate, 22: ceramic layer (low temperature fired ceramic), 23: inner layer wiring conductor, 24
... thick film resistors, 25 ... electrode patterns, 26 ... trimming grooves.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 41/87 H01C 7/00 M H01C 7/00 H05K 1/09 Z H05K 1/09 C04B 35/16 Z F-term (reference) 4E351 AA07 BB05 BB31 DD20 DD31 DD45 4G030 AA08 AA35 AA36 AA37 BA12 GA35 5E033 AA18 AA25 BA01 BB06 BG02 5E346 AA02 AA12 AA14 AA25 AA28 AA32 AA34 AA37 BB01 CC18 GG01 GG01 GG01 CC18

Claims (3)

[Claims] An internal wiring conductor is formed on an inner layer of a multilayer substrate formed of a low-temperature fired ceramic, a thick-film resistor is formed on a surface of the substrate, and the inner-layer wiring conductor is formed in a region immediately below the thick-film resistor. In a low-temperature fired ceramic multilayer substrate at least partially wired, T1 is the thermal expansion coefficient of the inner wiring conductor, T2 is the thermal expansion coefficient of the low-temperature fired ceramic, and T3 is the thermal expansion coefficient of the thick film resistor. A low-temperature fired ceramic multilayer substrate characterized by satisfying the following relationship:> T2 and 2.5 × 10 ⁻⁶ / ° C ≧ T2 −T3 ≧ 0.5 × 10 ⁻⁶ / ° C. 2. The method according to claim 1, wherein said thick film resistor is made of RuO ₂ and SiO _2.
-B ₂ O ₃ -K ₂ and a O glass, the SiO ₂ -B
The composition of the ₂ O ₃ -K ₂ O glass is as follows: 60 wt% ≦ SiO ₂ ≦ 85 wt% 15 wt% ≦ B ₂ O ₃ ≦ 40 wt% 0.1 wt% ≦ K ₂ O ≦ 10 wt% Impurity ≦ 3 wt% The low-temperature fired ceramic multilayer substrate according to claim 1. 3. The low-temperature fired ceramic is CaO-A.
_{l 2 O 3 -SiO 2 -B 2} O 3 low-temperature co-fired ceramic multilayer substrate according to claim 1 or 2, characterized in that a mixture of glass and Al ₂ O _3.