JPH0226798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer circuit board in which not only wiring conductors but also resistors are multilayered, and a method for manufacturing the same.

In recent years, circuit boards equipped with semiconductor ICs have been used in electronic circuits. As semiconductor ICs, so-called sealed ICs, which are sealed with ceramic or the like, are used.

The miniaturization of a circuit board on which a semiconductor IC is mounted can be achieved by installing the IC chip itself on the circuit board for the following reasons (a) and (b).

(a) The chip element itself is smaller than the encapsulated IC.

(b) The spacing between connection terminals becomes narrower.

In this case, the spacing between the IC connection conductors on the board is 200μ
It is necessary to make it as fine and dense as about m. However, such fine patterns are produced using thick film technology in which conductor paste is printed on a ceramic substrate, dried, and fired, but due to printing sag and bleeding due to the lower viscosity of the printing paste during drying, the conductor spacing is 400 μm.
It was not possible to manufacture the product due to the poor quality.

On the other hand, the so-called green sheet method, in which a conductive paste is printed on a green sheet (unsintered board) whose main component is alumina, dried, and fired, produces fine and high-quality materials for the following reasons (a) and (b). Suitable for forming dense wiring conductors.

(a) The solvent in the printed paste soaks into the green sheet, causing the printed paste to sag and
Does not cause smudging.

(b) The green sheet has a sheet content of 10-20% during sintering.
Shrink.

However, alumina green sheet costs 1500~
In order to sinter at 1600℃, the conductor must be made of a high melting point metal such as molybdenum, tungsten, or manganese, which does not change in quality during sintering.If the resistor is installed in the inner layer of a multilayer structure, the quality will change during green sheet sintering. In the case of a multilayer board, it was necessary to sinter it and then form the resistor on the top layer.

Here, if we use an insulating material that is sintered at temperatures below about 1000°C as a green sheet or interlayer insulating layer instead of alumina, various thick film materials such as conductors and resistors can be applied, and fine, high-density wiring can be formed. It seems possible to create multi-layered resistance circuits made up of conductors and resistors.

Such materials include crystallized glass which precipitates microcrystals with β-spodyroxene as the main component and lithium metasilicate as a sub-component, and microcrystals with α-cordierite as the main component and clinopyroxene as a sub-component. Crystallized glass that precipitates is known. These materials have a heating rate of 2℃/
Minutes or less, high temperature holding time 1 to 5 hours, cooling rate 4
The heating time was long, less than 0.degree. C./min, and the conductor sometimes peeled off from the substrate when heated for a short time.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a novel compact multilayer circuit board that has fine, high-density conductor wiring using the green sheet method and that has resistors formed between the layers, and that can be fired in a short time. The object of the present invention is to provide a method by which the above multilayer circuit board can be manufactured.

The above object is that the insulating layer is a mixed insulating material of amorphous glass and insulating oxide crystal fine particles, the thick film conductor is made of metal particles or metal particles and the amorphous glass, and the thick film resistor is a conductive material. particles and the amorphous glass, the printing substrate is a green sheet made of the above insulating material and a polymeric binder, and a mixture (vehicle) of the polymeric binder and an organic solvent is made of the above insulating material. , add the powders constituting the thick film conductor and the thick film resistor to form an insulating paste, a conductor paste, and a resistor paste, respectively, and repeat printing these pastes on the green sheet, or paste the conductor paste and the resistor paste. A multilayer structure made by laminating printed green sheets and forming resistors between and on the layers is heated to 1000℃.
This is achieved by heat treatment at the following temperatures.

The features of the invention will be explained in detail below. In the insulating material for the green sheet and insulating layer constituting the multilayer structure, preferably 60% by weight from 50 to 80% by weight in the mixture of amorphous glass powder and insulating oxide crystal fine particles.
~70% by weight is amorphous glass, and the remainder is oxide crystal fine particles. When the amount of amorphous glass is less than 50% by weight, the sintered body becomes porous and has significantly high hygroscopicity, and fine foaming occurs in the resistive film formed thereon. Moreover, if the amount exceeds 80% by weight, the influence of glass flow will be large, causing deformation of the conductor/resistance pattern formed on the sheet. One or more types can be used for the remaining oxide crystals, but
These should each have a coefficient of thermal expansion in the range of +30×10 ⁻⁷ to −10×10 ⁻⁷ /deg relative to the amorphous glass. Combinations of thermal expansion coefficients outside this range will cause cracks in the multilayer structure.

The composition of the amorphous glass to be used is not limited, but lead aluminoborosilicate glass containing BaO, CaO, ZnO, SrO, TiO ₂ , Bi ₂ O ₃ etc. is suitable for practical use.
A small amount of alkali metal oxide such as Na ₂ O, Li ₂ O, K ₂ O, etc. may be added. The softening point as a thermal property of amorphous glass determines the range of sintering temperatures of the multilayer structure. For heat treatment below 1000°C, the temperature should be at least 150°C lower, preferably 250°C lower.
It is best to have a softening point below 750℃. Note that the softening point of the amorphous glass that can be used in the present invention is preferably 400°C or higher, and the sintering temperature is preferably 550°C or higher.

Further, the oxide crystals are preferably fine particles with a maximum particle size of 10 μm and an average particle size of 0.5 to 3.0 μm in order to ensure surface smoothness of the printed substrate and the sintered body.
_{Al2O3 , SiO2} , MgO, SrO, BaO, CaO, _ZrO2 ,
Insulating metal oxides such as TiO ₂ , MgAl ₂ O ₃ ,
CaZrO ₃ , Mg ₂ SiO ₄ , ZrSiO ₄ , BaAl ₂ Si ₂ O ₈ ,
Aluminates, zirconates such as CaAl ₂ Si ₂ O ₈ ,
Among fine particles of oxide crystals such as silicate and aluminosilicate, those within the range defined by the coefficient of thermal expansion of amorphous glass are used.

For the conductors for wiring and resistor electrodes, noble metals such as gold, silver, palladium, and platinum are used as metal components. At this time, as a so-called binder glass,
The amorphous glass used as the insulating material can be contained up to 5% by weight at most. For conductors containing more glass than this, the heat treatment causes the glass in the insulating material to penetrate into the conductor layer, making solder connections completely impossible. Even when a conductor paste consisting of metal particles and vehicle without binder glass is used, the conductor adheres well to the insulating material.

The resistor is made of amorphous glass used as an insulating material as a binder glass, such as RuO ₂ , Bi ₂ Ru ₂ O ₇ ,
It consists of a main conductive component such as Pb ₂ Ru ₂ O ₆ and contains 50 to 90% by weight of glass to adjust the resistance value.
To improve resistor characteristics such as TCR and noise characteristics,
Precious metal particles such as gold and platinum, and MnO ₂ , CdO,
Semiconductor oxides such as NiO may also be added.

In the method for producing a multilayer structure using the above-mentioned materials, the production of amorphous glass powder, the production of green sheets, and the production of various pastes themselves are performed by conventionally well-known methods, as shown in the examples below. I did it. The most distinctive feature of the present invention is that the multilayer structure including the resistor formed according to the present invention is sintered under exactly the same temperature conditions as a thick film circuit formed on a normal sintered substrate. That is,
Maintain a temperature 150℃ or more higher than the softening point of amorphous glass for 5 to 10 minutes, and increase and decrease the temperature at a rate of 50 to 100℃/min.
Sintering is performed under conditions where the total heat treatment time is 30 minutes to 1 hour. If the temperature is increased or decreased at a faster rate than this, non-uniform shrinkage, curvature, or cracking of the multilayer substrate will occur.

Even in such short cycle heat treatment,
The green sheet of the present invention shows uniform shrinkage and can form a good multilayer structure without warping, curvature, cracks, etc. In addition, various defects such as peeling of the conductor, cracks in the resistive film, constrictions and cracks at the bonding interface between the conductive electrode and the resistive film, and bubbling at the overlapping portion of the electrode and the resistive film do not occur at all.

This will be explained in detail below using specific examples.

Example 1 A green sheet and an insulator material for insulation were prepared as follows. By weight percentage, SiO ₂ is 55%,
Oxides such _{that PbO is 17%, Al2O3 is 9%, CaO is 8%, B2O3 is 5} %, MgO is ₁ %, _Na2O is 3%, and _K2O is 2%. , carbonate or hydroxide are mixed in a ball mill and placed in a platinum beaker.
It is melted at 1500°C, then poured into water and rapidly cooled to produce a coarse glass material. This was ground in an agate mortar and a whole mill to produce an amorphous glass fine powder with an average particle size of 2.5 μm. This glass had a coefficient of thermal expansion of 60×10 ^-7 /°C and a softening point of 690°C.

Next, as an insulating oxide having a coefficient of thermal expansion of 90 to 50×10 ⁻⁷ /° C., 65 g of the amorphous glass was added to and mixed with 35 g of alumina powder having an average particle size of 0.6 μm.

The vitreous green sheet is produced by a widely known method. It was prepared as follows. After adding and mixing polyvinyl bityral to a mixture of alumina and amorphous glass, a mixed solvent of butylphthalyl butyl glycolate and tricrene-percrene-alcohol is added and kneaded in an alumina ball mill to form a slurry. This was passed through a doctor blade to create a sheet with a dry film thickness of 0.8 mm, which was cut into appropriate pieces to obtain printing green sheets (unfired substrates) for circuit formation.

A paste for interlayer insulation was prepared by adding an organic vehicle for thick film to the mixture of alumina and amorphous glass used for the green sheet and kneading the mixture.

The resistance paste was prepared by adding 80 wt % of the amorphous glass to RuO ₂ having an average particle size of 0.8 μm, adding an organic vehicle for thick film paste, and kneading.

The conductive paste was prepared by mixing Ag powder and Pd powder at a weight ratio of 7:3, adding 5 wt % of the amorphous glass, adding an organic vehicle for thick film paste, and kneading.

Next, the configuration of the present invention will be explained with reference to FIG.
The green sheet made of amorphous glass and fine alumina particles is used as the printing substrate 1, and the prepared conductive paste is printed to form resistor electrodes 3 and first layer wiring 2.
was formed. After air drying, the prepared resistor paste was printed at a predetermined position to form a first layer resistor 4. Next, an insulating glass paste prepared having the same components as the green sheet was printed to form an interlayer insulating layer 5. At this time, through holes 6 are formed to electrically connect the top and bottom of the thickness. Next, a conductive paste is printed to obtain interlayer conduction through the through holes, and the second layer wiring 7 and the resistor electrode 3 are formed in the same manner as the first layer, and the resistor paste is printed to form the second layer resistor. Body 8 was formed.

In FIG. 1, since the resistor has two layers, external connection terminals 9 and element connection terminals 10 such as IC elements and chip capacitors are formed in this layer. If the resistor is to be made into multiple layers, printing of insulating paste, conductive paste, and resistive paste is repeated as described above.

The unsintered substrate printed and laminated in this way is
A multilayer circuit board with built-in resistors was created by firing in air using a belt furnace for thick film firing, which was maintained at 900°C for 10 minutes. This heat treatment caused the green sheet to shrink by 15%.

In the resistor constructed according to the present invention, although the resistance value of the interlayer resistor is slightly larger than that of the resistor on the insulating layer, there are no defects such as cracks in the resistor on the layer or constrictions at the joint with the electrode. It was possible to form a good resistive film.

In the material system of this example, good results were obtained within the specified composition range. That is, (1) If the amorphous glass component in the insulator is more than 80wt%, the insulator becomes non-porous, but the conductor resistance pattern formed between and on the layers is deformed, and the conductor's substantial As the glass content increases, it becomes difficult for solder to adhere to the external element connection terminals. on the other hand,
If it is less than 50wt%, the insulator becomes porous,
This results in unfavorable results such as a significant decrease in interlayer insulation.

(2) The glass content in the resistive composition mainly determines its resistance value, and the range for obtaining a sheet resistance value of 10 to 1 Ml/mouth, which is highly practical, is 50 to 90 wt%.

(3) Even if the conductive paste composition does not contain glass, it is possible to form a good resistance film with no defects at the joint. However, when the glass content increases, although the resistive film is good, when the glass content exceeds 5 wt%, solder does not stick to external element connection terminals.

If a resistive paste or a conductive paste other than the amorphous glass component in the insulating material is used in accordance with the present invention, defects such as cracks in the resistive film and constrictions at the joints with the electrodes occur.

Furthermore, similar to the ceramic multilayer wiring board formed by the green sheet method using alumina, in the present invention, due to the solvent absorption effect of the green sheet, finer conductors can be formed compared to thick film hybrid integrated circuits using sintered alumina substrates. The wiring has been completed.

Example 2 The thermal expansion coefficient prepared in Example 1 is 60×10 ^-7 /
℃, 70 g of amorphous glass with a softening point of 690℃ and an average particle size of 2.5 μm, and 10 g of alumina with an average particle size of 0.6 μm as a crystalline oxide with a coefficient of thermal expansion of 90 to 50 × 10 ^-7 /℃. , 10 g of magnesia spinel (MgAl ₂ O ₄ ) with an average particle size of 2.0 μm and 10 g of calcium zirconate (CaZrO ₃ ) with an average particle size of 2.5 μm were added and mixed to produce an amorphous glass for green sheets. and crystalline oxide mixtures were prepared.

Using the green sheet of this mixture, the conductive paste and the resistor paste prepared in Example 1,
The multilayer circuit board shown in FIG. 2 was produced in the following manner.

A conductive paste is printed on the printed base 1-1 of the green sheet to form the first layer wiring 2 and the resistor electrode 3, and the resistor paste is printed to form the first layer resistor 4.
was formed. Next, a printing substrate 1-2 of a green sheet with through holes formed as shown in 6 in FIG.
Then, the second layer wiring 7, the second layer resistor 8, the external connection terminal 9, and the element connection terminal 10 are formed, and the through holes are filled with a conductor to provide continuity between the upper layer and the lower layer, and the resistor is formed. Printed and formed. These two green sheets were stacked on top of each other, heated to 100°C, pressed together under a load of 500 kg/cm ² , and heat-treated in a conventional air firing thick film belt furnace that held the temperature at 900°C for 10 minutes. The revenue was 16%.

In this multilayer circuit board, although the resistance value of the resistor between the layers was slightly larger than that of the resistor on the layer, there were no defects such as cracks in the resistor on the layer or constrictions at the joints with the electrodes. .

Example 3 As the crystalline oxide added to the amorphous glass of Example 1, other fine particles having a coefficient of thermal expansion of 90 to 50 × 10 ^-7 /°C, such as zirconate, silicate,
Good effects were obtained even when aluminates were used alone or in combination with others.

Example 4 A green sheet and an insulator material for insulation were prepared as follows. 40% _SiO2 by weight percentage;
28% BaO, 9% Al ₂ O ₃ , 10% Pb ₃ O ₄ ,
5% Bi ₂ O ₃ , 3% CaO and 5% Na ₂ B ₂ O ₇
Raw material powders such as oxides and carbonates were mixed, melted and crushed to prepare a fine powder of amorphous glass with an average particle size of 3.0 μm. This thermal expansion coefficient is 80×
10 ^-7 /℃, and the softening point was 600℃. 60g of this amorphous glass has a coefficient of thermal expansion of 110 to 70×10 ^-7 /℃
As a crystalline oxide, 25 g of zirconia (ZrO ₂ ) with an average particle size of 3.0 μm and 15 g of forsterite (Mg ₂ SiO ₄ ) with an average particle size of 1.5 μm were added and mixed. A mixture of amorphous glass and crystalline oxide was prepared. A green sheet and an insulating paste were prepared as shown in Example 1.

Next, this amorphous glass is 80wt% and 0.8μm
A resistive paste consisting of 20wt% Bi ₂ Ru ₂ O ₇ ;
An Ag/Pd-based conductive paste containing 5 wt% of this amorphous glass was prepared.

A conductive paste, a resistive paste, and an insulating paste were printed on a green sheet, multilayered according to the procedure of Example 1, and heat treated in a thick film belt furnace maintained at 850°C for 10 minutes to create the circuit board shown in Figure 1. .

The resistor formed on this glassy insulating layer had no defects such as cracks, and together with the resistor formed between the layers, it had various properties suitable for practical use.

Example 5 As a crystalline oxide in the amorphous glass of Example 4, alumina, which has a coefficient of thermal expansion in the range of 110 to 70 × 10 ^-7 /°C, for example, used in Examples 1 and 2,
Good results were also obtained when magnesia spinel, calcium zirconate, and other zirconates such as magnesium zirconate, silicates, and aluminates were used alone or in combination.

Example 6 A green sheet and an insulator material for insulation were prepared as follows. 64% _SiO2 by weight percentage;
24% _B2O3 , 4% _{Al2O3 ,} 3 _% ZnO, _Na2O
Mix raw material powders such as oxides and carbonates so that _K2O is 2% and K2O is 3%, melted and crushed to obtain an average particle size.
Amorphous glass fine powder of 2.5 μm was prepared. The coefficient of thermal expansion was 45×10 ^-7 /°C, and the softening point was 720°C.
60g of this amorphous glass has a coefficient of thermal expansion of 75 to 35×
10 ^-7 /℃ as a crystalline oxide with an average particle size of 3.5μm
5g of zircon (ZrSiO ₄ ), average particle size 2.0μm
It was prepared by adding and mixing 15 g of Celsian (BaAl ₂ Si ₂ O ₈ ) and 20 g of alumina with an average particle size of 0.6 μm.

Green sheet and insulation paste were prepared in Example 1.
It was prepared as described in . Next, a resistance paste consisting of 80 wt % of this amorphous glass and 20 wt % of RuO ₂ having an average particle size of 0.5 μm and an Ag/Pd based conductive paste not containing this amorphous glass were prepared. A conductive paste, a resistive paste, and an insulating layer paste were printed on a green sheet, and multilayers were formed in the same manner as in Example 1. Then, in an air-fired thick-film belt furnace,
Heat treatment was performed under conditions of holding the temperature at 950°C for 10 minutes.

The resistor formed on this glassy insulating layer did not cause any cracks, and together with the resistor formed between the layers, it achieved various properties suitable for practical use.

Example 7 Mullite (3Al ₂ O ₃ .
2SiO ₂ ), 10 g of anorthite (CaAl ₂ Si ₂ O ₈ ) with an average particle size of 2.0 μm, and 15 g of alumina with an average particle size of 0.6 μm were added and mixed in the same manner as in Example 1 to form a green sheet. and an insulation paste was prepared.

The conductive paste and resistive paste prepared in Example 6 were printed on this green sheet, and then the insulating layer paste prepared in this example was printed, and the sheet was multilayered in the same manner as in Example 2. Firing in the air
The test was carried out under conditions of holding at 950°C for 10 minutes. Good results were also obtained in this example.

As described above, according to the present invention, a multilayer structure having fine, high-density wiring conductors and having a resistor formed between the layers can be created by a short heat treatment. It has become possible to manufacture compact multilayer hybrid integrated circuit boards on which semiconductor ICs and other components can be mounted at high density.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a multilayer circuit board according to the present invention, and FIG. 2 is a cross-sectional view of another example of the present invention. 1, 1-1, 1-2: Printed substrate, 2: First layer wiring, 3: Resistor electrode, 4: First layer resistor, 5:
Interlayer insulating layer, 6: Through hole, 7: Second layer wiring, 8: Second layer resistor, 9: External connection terminal, 1
0: Element connection terminal.

Claims (1)

[Scope of Claims] 1. A substrate on which a resistor circuit is provided, an insulating layer provided on the entire surface of the circuit formation surface of the substrate except for the connecting portion, and a substrate connected to the circuit at the connecting portion on the insulating layer. In a multilayer circuit board in which an insulating layer and a resistor circuit are provided at least once in the same manner as described above, each of the substrate and the insulating layer is amorphous with a softening point of 750°C or less. glass 50~80wt
%, insulating oxide 50 to 20 wt%, and the difference in coefficient of thermal expansion between this insulating oxide and this amorphous glass is in the range of +30 × 10 ^-7 to -10 × 10 ^-7 /deg. All the conductor paths of the resistance circuit are made of 95wt% or more of metal and 5wt% or less of the amorphous glass, and all the resistors of the resistance circuit are made of a conductive material and the amorphous glass. A multilayer circuit board characterized by comprising: 2. Print a conductor paste and a resistance paste on a green sheet, dry them to form an unfired resistance circuit in which a resistor is connected by a conductor circuit, and then remove the connection part on the resistance circuit forming surface of the green sheet. An insulating paste is printed on the entire surface and dried to form an unfired insulating layer, and then an unfired conductor circuit is printed and dried on this insulating layer to be connected to the resistor circuit using a conductor paste, and a resistor paste is formed. is printed and dried to form an unfired second resistance circuit, and if necessary, an unfired insulating layer and an unfired resistance circuit are provided at least once each in the same manner as above to form a multilayered unfired circuit board. , and then firing the same. 3 The green sheet consists of 50-80wt% amorphous glass powder with a softening point of 750℃ or less, and 50-20wt% insulating oxide powder.
%, and the difference in thermal expansion coefficient between the amorphous glass and the insulating oxide is in the range of +30×10 ^-7 to -10×10 ^-7 /deg. The conductor paste is made from metal powder and green sheets.
The resistor paste is made of the above amorphous glass powder and a vehicle, the resistance paste is made of the resistor powder, the above amorphous glass powder, and the vehicle, and the insulating paste is made of the above amorphous glass and an insulating oxide. blend,
3. The method of manufacturing a multilayer circuit board according to claim 2, wherein the firing is performed in a vehicle at a temperature of 150 to 250[deg.] C. higher than the softening point of the amorphous glass.