JP3093601B2 - Ceramic circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic circuit board having on its surface an external resistor covered with overcoat glass. More particularly, the present invention relates to a ceramic circuit board having an external resistor that stably maintains an accurate resistance value obtained by trimming.

[0002]

2. Description of the Related Art In a ceramic circuit board used for an integrated circuit, in addition to a built-in resistor provided between layers of a multilayer circuit board, a circuit comprising a conductor pattern printed on the surface of the ceramic circuit board, an external resistor, and the like. Are provided, contributing to higher performance and lower cost of the ceramic circuit board. When a resistor is formed on the surface of a substrate, generally, a resistor obtained by adding a conductive material to a glass composition to form a paste is printed and sintered to form a resistor. At this time, for the purpose of protecting the resistor and improving the weather resistance, overcoating is performed by printing the resistor with a glass-based material and baking the resistor. Further, the resistance value is finely adjusted using a technique such as laser trimming.

Generally, a resistor used for a ceramic circuit board is fired at 800 to 900 ° C., printed with a low melting point overcoat glass, and fired at 500 to 600 ° C. However, with the miniaturization and high density of electronic devices, ceramic substrates also tend to be multilayered for high density and have low thermal expansion due to mounting of silicon chips. A low-temperature fired substrate is used for such a circuit board. Ag and Cu are often used for the inner layer of low-temperature fired substrates.
In order to reduce the number of thermal expansion and contraction and obtain a highly reliable circuit board, it is necessary to reduce the number of firings as much as possible. Further, in order to match the thermal expansion with the circuit board, it is necessary to use a glass having a low thermal expansion as the overcoat glass, but a glass having a low melting point has a drawback in terms of weather resistance. For this reason, it is inevitable to use glass whose temperature is about the firing temperature of the resistor.
Therefore, it is desirable to use an overcoat and a co-fired resistor for a ceramic circuit board having a multilayer structure or low thermal expansion. However, when the resistor and the overcoat are fired at the same time, the overcoat glass tends to trap bubbles generated from the resistor, and the bubbles tend to remain inside the sintered resistor. When the bubble in the resistor is very close to the bubble at the trimming tip during laser trimming, there is a problem that a crack is generated between the trimming tip and the bubble, and the resistor becomes a resistor having an unstable resistance value.

FIG. 1 is a plan view of a conventional external resistor provided on a ceramic circuit board, and FIG. 2 is a sectional view thereof. A conductor pattern 2 on the surface is formed by printing a metal paste or the like as a wiring material on the surface 1 of the ceramic substrate, and a part of the conductor pattern 2 serves as an electrode to a resistor. The resistor 3 is formed by adding a conductive material such as a metal to a glass component, and the glass material is overcoated 4 so as to cover the upper part thereof. The external resistor 7 is formed by the resistor 3 and the overcoat 4. The overcoat 4 may be covered so as to be slightly wider than the individual resistors 3, or the plurality of resistors 3 may be covered uniformly over a wide area including the conductor pattern 2. When overcoating over a wide area, via holes can be provided at necessary places to further establish electrical continuity with the outside. When the overcoat 4 and the resistor 3 are fired at the same time, the bubbles 6 generated in the resistor become overcoated.
Is present and cannot escape to the outside, but is trapped inside. When such an external resistor 7 is laser-trimmed, a trimming groove 5 as shown is formed in the overcoat 4 and the resistor 3. Normally, laser trimming is performed while measuring the resistance value. However, the presence of the bubbles 6 not only makes such precise trimming difficult, but also causes microcracks when the tip of the trimming groove approaches the bubbles 6. Will happen. Further, even if no crack is generated during trimming, a crack may occur during use as a product due to bubbles. Thus, the presence of bubbles in the resistor makes the resistance value inaccurate and renders it unstable.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic circuit board with an external resistor, in which the resistor hardly contains air bubbles and which has an overcoat co-fired with the resistor. is there.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above object is achieved when the resistor and the overcoat glass have a specific relationship, and have reached the present invention. That is, the present invention is a ceramic circuit board having the following configurations (1) to (4) . (1) Resistor and overcoat glass
With external resistor made by co-firing
In the circuit board, the content of the Ag-based component contained in the resistor is 0 to 1%, and the sag point of the glass of the resistor is less than the sag point of the overcoat glass. substrate. (2) Simultaneous firing of resistor and overcoat glass
A ceramic circuit board having an external resistor
A ceramic circuit board, wherein the resistor contains 1% or more of an Ag-based component, and the temperature of the resistor, which is lower by 10 ° C. than the glass deformation point, is lower than the deformation point of the overcoat glass. (3) the glass component of the resistor is CaO-Al ₂ O ₃ -S
wherein which is a iO ₂ -B ₂ O ₃ based glass
The ceramic circuit board according to (1) or (2) . (4) The component of the overcoat glass is CaO-Al
_{2 O 3 -SiO 2 -Cr 2 O} 3 -B 2 O 3 based glass powder 60
Containing 90% by weight and 10 to 40% by weight of alumina powder,
The glass circuit board according to the above (1) or (2), wherein the glass has a sag point of 720 to 740 ° C.

According to the present invention, even when the overcoat glass and the resistor are co-fired, no bubbles remain in the resistor and a low-bubble resistor can be obtained. Is 0 to 1%, and by making the glass of the resistor have a lower deformation point than the deformation point of the overcoat, sintering of the resistor is accelerated and bubbles generated are released to the overcoat glass side. And secondly, R
In addition to the electric resistance component of uO ₂ system and Bi ₂ Ru ₂ O ₇ system, Ag
Ag is combined with this resistor material to promote sintering by positively adding 1% or more of, and the sintering of the resistor is accelerated in the same manner as described above, and bubbles generated are generated on the overcoat glass side. Because they let go. In this case, the resistor
The temperature 10 ° C lower than the yield point of the lath
It should be lower than the yield point of glass. The yield point used in the present invention, as the glass material is heated, the coefficient of thermal expansion increases almost linearly, but corresponds to the softening temperature of the glass when the increase stops at a certain temperature and starts to decrease. Things. The method of measuring the coefficient of thermal expansion itself is defined in Japanese Industrial Standards.

The ceramic circuit board of the present invention may be a single layer or a multilayer as long as it uses ceramic as an insulator. In the case of a multilayer ceramic circuit board, the manufacturing method thereof is a green sheet laminating method, a green sheet printing. Law. Further, a circuit board having only one side of the board or a double-sided circuit board may be used. The ceramic material used in the present invention is not particularly limited, and may be alumina (Al ₂ O ₃ ),
Examples include aluminum nitride (AlN), silicon carbide (SiC), and various ceramics containing these as main components. or,
A low-temperature fired ceramic in which glass powder is mixed with alumina powder can also be used. The conductor material used for the inner layer depends on the substrate material, and alumina or aluminum nitride uses a high melting point metal such as molybdenum or tungsten. When the substrate material can be fired at a relatively low temperature,
Metals such as gold, silver, silver-palladium alloy, copper, and nickel are used. One of the co-fired ceramic circuit boards, which simultaneously fires the ceramic green sheet and the wiring conductor paste, uses W or Mo as a wiring conductor of a substrate such as alumina or aluminum nitride in a reducing atmosphere so that the conductor is not oxidized. There are co-fired ceramic circuit boards. However, when a highly reliable RuO ₂ -based or Bi ₂ Ru ₂ O ₇ -based resistor which needs to be fired in an oxidizing atmosphere is formed, there is a problem that the conductor is oxidized.

On the other hand, Ag, Ag-Pd, Ag-
Ag-based conductors such as Pt and Ag-Pd-Pt, which have low conduction resistance and can be oxidized and fired, were used, and a ceramic material which could be fired at a melting point (900 to 1200 ° C.) or lower of these conductor materials was used as an insulator. Low-temperature fired ceramic multilayer wiring boards have been developed and are particularly preferred as the ceramic substrate of the present invention. Generally, a ceramic substrate fired at about 1200 ° C. or lower is referred to as a low-temperature fired ceramic substrate, and an Ag-based or Cu-based material is used for the inner layer and the surface layer as conductors. As described above, as the low-temperature fired ceramic insulator material, it is preferable to use a material that can be fired at a temperature lower than the melting point of, for example, an Ag-based conductor material contained therein. When an Ag conductor or an Ag alloy-based conductor having a low content of Pd and Pt is used, the melting point of the metal formed in such a multilayer is as low as about 900 to 1200 ° C., and thus 800 to 1100 ° C.
It is necessary to use a material that can be fired by borosilicate glass, and typical examples thereof include borosilicate glass and several types of oxides (eg, MgO, CaO, Al ₂ O ₃ , PbO, K ₂ O,
Na ₂ O, ZnO, Li ₂ O, etc.) and a mixture of glass powder and a ceramic powder such as alumina or quartz as a raw material, or a glass powder in which cordierite-based or α-spodumene-based crystallization occurs. There is.

Although such a material can be used as a single layer as described above, a green sheet laminating method using a green sheet is used for laminating a multilayer substrate. For example, a solvent, a resin, and the like are added to the ceramic insulator material powder, and molded by a doctor blade method,
A green sheet having a thickness of about 0.1 to 0.5 mm is obtained.
The necessary wiring patterns are defined as Ag, Ag-Pd, Ag-
Screen printing is performed using a conductive material paste such as Pt or Ag-Pd-Pt. Further, a through-hole of about 0.1 to 2.0 mmφ is formed in the green sheet by a punching die or a punching machine so that another conductor layer can be connected. The wiring via hole is filled with an Ag-based conductor material. Print wiring patterns on other green sheets as needed to form circuits in a similar manner. After accurately stacking these green sheets using the positioning holes drilled in each green sheet, 80 to 1
Thermocompression bonding is performed under the conditions of 50 ° C. and 10 to 250 kg / cm ² to be integrated. If the circuit includes an internal resistor, a resistor of RuO ₂ or Bi ₂ Ru ₂ O ₇ fired in an oxidizing atmosphere is formed. In that case, it is printed on the inner layer green sheet together with the resistance electrode.

The above-mentioned components are simultaneously fired in an oxidizing atmosphere to obtain a conductor-embedded ceramic multilayer substrate. The low-temperature fired ceramic has been described above as an example, but these are preferred embodiments of the present invention, but are not limited thereto. The resistor used in the present invention is composed of a RuO ₂ -based or Bi ₂ Ru ₂ O ₇ -based electrical resistance component and a glass component, and is usually printed on a ceramic circuit board in paste form by a thick film method. . Overcoat glass component over the printed resistor, for example, CaO-Al ₂ O ₃ -Si
In O ₂ -B ₂ O ₃ based glass still thick film methods, usually printed. Then, in the present invention, these resistors and the overcoat glass are simultaneously fired. This firing is performed in normal air.

[0012]

The present invention will be described in more detail with reference to Examples and Comparative Examples. As the ceramic circuit board, a low-temperature fired ceramic prepared by the following method was used. Weight composition is C
_{aO27%, Al 2 O 3 5} %, SiO 2 59%, B 2 O 3 9
% Of glass powder and 40% by weight of Al ₂ O ₃ powder having an average particle size of 1.0 μm were mixed to obtain a powder component.

The ceramic green sheet is composed of 10% of acrylic resin, 30% of toluene, 10% of isopropyl alcohol and 5% of dibutyl phthalate in a weight ratio with the above powder components.
Were mixed by a ball mill, and a green sheet having a thickness of 0.4 mm was formed by a doctor blade method. Next, a hole was formed in a predetermined position in the green sheet with a mold, and the Ag paste was filled in the hole by a screen printing method. After drying, a wiring pattern was formed by a screen printing method using an Ag paste.
A green sheet on which another wiring pattern was printed was prepared in the same manner, and was overlaid on a predetermined layer and thermocompression-bonded. The laminate was fired at 900 ° C. for 20 minutes to obtain a ceramic circuit board. A resistor having the composition shown in Table 1 was printed on the ceramic substrate so that the resistor portion had a width of 1 mm and a length of 2 mm. As the overcoat material, A in Table 2
To those having the glass composition and yield point shown in
_A mixture of ₂ O ₃ powder was printed on the resistor.

[Table 1]

[Table 2] Various combinations of these resistors and overcoat glass were simultaneously fired in air at 890 ° C. for 10 minutes. The ratio of RuO _{2 in} the resistor material shown in Table 1 is% by weight based on the total amount of the resistor including the glass component, and the ratio of Ag is also the weight based on the total amount of the resistor including the glass component and RuO _2. %. Here, the load test shown in Table 3 means that a load of 1/32 W
This is the maximum change rate of the resistance value when given time.

[0014]

[Table 3]

Table 3 shows the maximum value of the rate of change of the resistance value as a result of the load test when the resistors 1 to 24 and the overcoat glasses A to H are combined. Observation with a microscope shows the number of bubbles having a diameter of 5 μm or more included in a section of 300 μm × 15 μm.

[0016]

[Table 4] In the combination of the resistors 1 to 24 and the overcoat glasses A to H in Tables 3 and 4, the content of the Ag-based component was 0%.
Examples of the invention of the yield point of the glass of the resistor according to claim 1 is less than the yield point of the overcoat glass, A. 3 to the
8, 11 to 14, B to 5 to 8, 13, 14, C to 1 to 1
4, 3-8 of D, 13, 14, E 3-8, 11-1
4, F 1 to 14, 16, 18, 21, 23, G 3 to
8,11～14, 7 and 8 are H, 13,14. or,
By adding 1.0% or more of Ag, an effect equivalent to a temperature lowered by 10 ° C. from the sagging point of the resistor is obtained, but the examples of A, 15, 17, 19, 20, 22, 24,
15, 17, 19, 20, 24 of B, 15, 17, C of
19, 20, 22, 24, 15, 15, 19, 2 of D
0,22,24,15,17,19,20,22 of E,
24, F 15, 17, 19, 20, 22, 24, G 15, 17, 19, 20, 22, 24, H 17, 24
It is. Other than the above are comparative examples of the present invention. From Tables 3 and 4, for example, when the overcoat glass G is used, when the sag point of the glass of the resistor is equal to or less than the sag point of the overcoat glass according to the combination example with the resistors 1 to 14, Since the sintering of the resistor is faster, the number of bubbles is very small, and the rate of change is 1% or less, indicating that the load test is good. In general, as a standard for evaluating the reliability of the thick film resistor, a standard value is within ± 1% in an accelerated test. Also, for example, the resistors 15, 17 and 1
By comparing a combination example of 9, 20, 22, 24 with a combination example of resistors 16 and 18, 21, 23, which are comparative examples, sintering of the resistor is promoted by adding Ag, As a result, it can be seen that the load test is good because the number of generated bubbles is zero or very small. It can be seen that adding 1.0% or more of Ag promotes the sintering of the resistor with an effect equivalent to a temperature lowered by 10 ° C. from the yield point. If it exceeds 10%, Ag particles are precipitated and the resistance value becomes low.

[0017]

As described above, according to the present invention, a ceramic circuit board having a low-bubble external resistor and an overcoat co-fired with the external resistor can be obtained, and the protection of the resistor after trimming is sufficient, and the weather resistance is improved. It exhibits low resistance and excellent stability and stability.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a conventional external resistor;

FIG. 2 is a sectional view of FIG.

[Explanation of symbols]

 Reference Signs List 1 ceramic substrate 2 surface conductor 3 external resistor 4 overcoat glass 5 trimming groove 6 bubble 7 external resistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 1/18 H05K 1/03 610 H05K 3/28

Claims (4)

(57) [Claims] 1. A method for simultaneously using a resistor and an overcoat glass.
For ceramic circuit boards with fired external resistors
Here, the content of the Ag-based component contained in the resistor is 0
A ceramic circuit board, wherein the sag point of the resistor glass is less than the sag point of the overcoat glass. 2. Simultaneous use of the resistor and the overcoat glass
For ceramic circuit boards with fired external resistors
Oite, the resistor contains at least 1% of Ag-based component, a ceramic circuit board 10 ° C. lower temperature in the yield point of the glass of the resistive element antibodies, and less than the yield point of the overcoat glass . 3. The glass component of the resistor is CaO-Al.
Claim 1 or claim 2 ceramic circuit board, wherein the a _{2 O 3 -SiO 2 -B 2 O} 3 based glass. 4. The component of the overcoat glass is Ca
_{O-Al 2 O 3 -SiO 2} -Cr 2 O 3 -B 2 O 3 system containing glass powder 60 to 90 wt% and 10-40 wt% of alumina powder, and deformation point of the glass is at seven hundred twenty to seven hundred forty ° C. claim 1 or claim 2 ceramic circuit board according to wherein there.