JP2958492B2 - Method for manufacturing multilayer wiring circuit board - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic multilayer wiring circuit board, and more particularly to a multilayer wiring having a low-temperature fired ceramic substrate composed of a vitreous frit and a ceramic component as a substrate material. A circuit board and a method of manufacturing the same.

[Prior art] Generally, a multilayer printed circuit board is formed by laminating and crimping a sheet on which a desired pattern is printed on a ceramic green sheet with a conductive paste of a high melting point metal such as molybdenum or tungsten as an internal wiring, and then laminated at 1400 ° C. It was baked to the extent.

However, molybdenum, tungsten, and the like have high firing temperatures leading to cost increases, and have relatively high conductor resistance, making it difficult to increase the speed of circuit signals.

Recently, gold (Au) and silver (A
The use of a material having a relatively low melting point and low resistance, such as g) and copper (Cu), has been studied. As for the substrate material, use of a glass-ceramic substrate (ceramic substrate for low-temperature firing) composed of a vitreous frit and a ceramic component that can be fired at a firing temperature of about 140 ° C. to a low temperature of less than 1000 ° C. has been studied.

In such a situation, Ag is promising as an internal wiring of a multilayer wiring circuit board using a ceramic for low-temperature firing. Although Ag has the problem of migration, it is extremely inexpensive compared to Au, and the debinding (debinding) process of the organic binder in the paste is simpler than that of Cu. Is small.

[Problems to be solved by the invention]

However, the biggest problem when using Ag as the internal wiring of the multilayer wiring board of the low-temperature firing ceramic is that there is a large difference in the degree of the sintering reaction between the low-temperature firing ceramic green sheet and the Ag paste. There is a problem that warpage occurs in the entire laminated substrate and a conductor resistance value increases. That is, an internal wiring pattern of Ag is formed on a green sheet of a low-temperature fired ceramic, and after laminating and pressing, firing at about 900 ° C. to sinter integrally,
After the completion of the sintering reaction, sintering is continued, and Ag oversintering occurs, and pores are generated in the conductor.

The present invention has been devised in view of the above-described problems, and has as its object to reduce the warpage of the substrate caused by the difference in the degree of sintering between the substrate and the internal wiring when using Ag as the internal wiring. Another object of the present invention is to provide a multilayer wiring circuit board having a resistance internal wiring.

[Specific means to achieve the purpose]

The specific means of the present invention carried out to solve the above-mentioned problems is that the average particle size is 5 to 180 ° C. by calcination at 250 ° C.
A desired internal wiring pattern is printed on a ceramic green sheet composed of a vitreous frit component and a ceramic component using a conductive paste obtained by mixing a silver powder grown in a substantially spherical shape of 25 μm and an organic vehicle. This is a method for manufacturing a multilayer wiring circuit board, comprising a step of laminating a plurality of ceramic green sheets and then performing a firing treatment.

[Action]

By means of the above means, a ceramic green sheet comprising a vitreous frit having a desired internal wiring pattern printed on the surface of the ceramic green sheet and a ceramic component is laminated and sintered to form a multilayer wiring circuit board. Since the conductive material printed as a pattern is formed by printing a conductive paste of a substantially spherical Ag powder having an average particle size of 5 to 25 μm, the Ag powder does not become an over-sintered state and is sintered. The later internal wiring conductor becomes dense, low resistance is achieved, and the substrate does not warp.

The particle size of the above-mentioned Ag powder is usually about 10 times as large as (1 to 2 μm). As a result, when sintering simultaneously with the laminated substrate of ceramic green sheets,
The sintering of the Ag powder is delayed, approximating the sintering temperature of the ceramic green sheet, and the difference in behavior is reduced. For example,
The sintering temperature of the ceramic green sheet varies slightly depending on the components of the vitreous frit, but the temperature ranges from 850 to 9
50 ° C. On the other hand, about 300 ~
The sintering reaction is completed at about 400 ° C., and the state of Ag sintering occurs between 850 and about 900 ° C.

In the present invention, the average particle size of 5 to 25 μm substantially spherical
By using Ag powder, the sintering start temperature is 700-800
° C, which can be approximated to the sintering temperature of the ceramic green sheet.

Further, since the sintered conductor does not become over-sintered, voids are not generated in the fired Ag fired conductor, and internal wiring having lower resistance than molybdenum and tungsten can be achieved.

Usually, Ag powder having a particle diameter of 2 μm or less is formed by the chemical reduction method as described above. In particular, 1μ
In the case of a conductive paste obtained by forming an Ag powder having a particle size of less than m into a paste, when printing and sintering integrally with the ceramic green sheet, the oversintering state of the Ag powder becomes extremely large, and the volume shrinks. As a result, voids are generated in the conductor after sintering, and the conductor resistance is increased. With respect to warpage, the voids act to prevent warpage, but are used fundamentally for the problem of conductor resistance. It is difficult.

In the case of a conductive paste obtained by forming an Ag powder having a particle size of about 1 to 2 μm into a paste, although porosity is small in the conductor, the sintering behavior is lower than the sintering temperature of the ceramic green sheet of glass ceramic. In the first place, the multilayer substrate after firing is warped.

In addition, there is another manufacturing method, a spherical powder manufactured by an electrolytic method, but the spherical powder formed by this method has a large particle size of several tens of μm, and further, in the case of flake powder, the particle size is not uniform and is flat. In this case, the mesh of the screen is clogged at the time of printing the internal wiring pattern, so that a wiring pattern with high accuracy cannot be obtained.

After all, it is optimal to use a substantially spherical Ag powder having an average particle size of 5 to 25 μm as the conductive paste for the internal wiring of the ceramic green sheet containing the vitreous frit.

Such an approximately spherical Ag powder having an average particle diameter of 5 to 25 μm is achieved by calcining the Ag powder by a chemical reduction method. That is, it is important to calcine before growing a small Ag powder having a particle size of 2 μm or less into a paste to grow the particle size of the Ag powder. The calcining temperature is 150 ~ 300 ℃
And preferably 180 to 250 ° C. As a result, the object of the present invention is to achieve a multilayer wiring circuit board with low internal wiring resistance and less warpage.

〔Example〕

Hereinafter, a multilayer wiring circuit board of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a multilayer wiring circuit board according to the present invention.

The multilayer wiring circuit board 10 of the present invention includes ceramic insulating layers (hereinafter, referred to as ceramic substrates) 1a, 1b... And internal wirings 2a, 2b. The internal wiring 2a on the ceramic substrate 1a and the internal wiring 2b on the ceramic substrate 1b
Is electrically connected through a through hole (shown by a solid line) 3b filled with a conductive material (the same material as the internal wiring 2b) formed on the ceramic substrate 1b. On the front and back surfaces of the multilayer wiring circuit board 10 formed as described above, a desired thick film circuit wiring 4, an electronic component 5, and the like are attached and mounted as necessary.

The method for manufacturing the above-described multilayer wiring circuit board 10 is as follows.

Ceramic substrates 1a and 1b constituting the multilayer wiring circuit board 10
... is a glass-ceramic material obtained by kneading a mixture consisting of a vitreous frit and a ceramic component with an organic component,
It is formed by sintering a ceramic green sheet formed by a doctor blade method. Specifically, the vitreous frit has, for example, magnesium oxide, aluminum oxide, and silicon oxide as main components, and the ceramic component is, for example, alumina, and is mixed at a ratio of 70 wt% and 30 wt%, respectively. As the organic component, the binder is, for example, an acrylic resin, the plasticizer is, for example, dibutyl phthalate, and the vehicle is, for example, toluene. Then, the mixture of the above-mentioned vitreous frit and the ceramic component and the organic component are homogeneously kneaded by a ball mill.

Are formed by sintering a conductive paste mainly composed of Ag. The conductive paste is formed by homogeneously kneading a metal powder mainly composed of Ag and an organic component. Ag powder, which is a metal powder, is formed by calcining a substantially spherical powder having a small particle size (less than 2 μm) formed by a chemical reduction method. This gives a substantially spherical powder having an average particle size of 5 to 25 μm. In particular
Ag powder calcined is Ag exposed by chemical reduction
The powder is placed in a crucible and heated in a thermostat at 150 to 300 ° C. for 1 hour.

As the organic vehicle, the organic binder is, for example, ethyl cellulose, and the organic solvent is, for example, 2.2.4-trimethyl-1.3-pentanediol monoisobutyrate.
Knead with this roll. For example, the average particle size is 5 to 25 μm
87-93% by weight of approximately spherical Ag powder and 7-
8% by weight, and 10% by weight of a binder and 90% by weight of a solvent are used in an organic vehicle.

Here, if the average particle size of Ag is increased, the specific surface area is reduced, so that the weight of Ag is increased. For example, the average particle size
For a 10 μm Ag powder, it is desirable to set the Ag powder to 90% by weight.

The ceramic green sheets formed by the above-mentioned doctor blade method are pressed and cut into a predetermined shape to produce single semi-green sheets 11a, 11b,....
And the ceramic green sheets 11a, 11b
.. Are formed at predetermined positions, through holes 3a, 3b... Are formed, and desired conductive wiring is formed on ceramic green sheets 11a, 11b. . At this time, the through holes 3a, 3b
-Also fill the conductive paste of A. As a filling method, the printing pressure of a screen printing squeegee is used, or air is drawn from the opposite side of the printing surface through the through holes 3a, 3b.
a, 3b ...

The ceramic green sheets 11a, 11b,... On which the desired internal wiring pattern is formed by the conductive paste as described above.
・ The required number of sheets are laminated and crimped.

Finally, sintering is performed at a peak temperature of 900 ° C. for 30 minutes to manufacture a multilayer wiring circuit board.

According to the multilayer wiring circuit board 10 described above, since the Ag powder of the conductive paste printed as a desired internal wiring pattern has an average particle size of 5 to 25 μm, the internal wirings 2a, 2b,.
・ Becomes dense, low resistance is achieved, and the substrate 1a,
The multilayer wiring circuit board 10 having no warp in 1b.

By using a conductive paste having an average particle size of 5 to 25 μm of the Ag powder, the temperature of the sintering reaction of the Ag powder is 700 to 800 ° C.
Becomes The sintering reaction temperature of the vitreous ceramic green sheets 11a, 11b,.
Since it is 50 ° C. and the sintering reaction temperatures can be approximated to each other, there is little difference in the sintering behavior, and the warpage of the entire substrate is reduced.

The fact that there is no warping of the whole substrate means that, when the pattern of the internal wiring 2a, 2b Also.

On the other hand, a normal conductive paste having an Ag powder having an average particle size of 2 μm or less has a sintering start temperature of the Ag powder of 300 μm.
400400 ° C., and the sintering reaction ends before the sintering reaction of the ceramic green sheet. Since the temperature is further increased, the Ag powder is in an over-sintered state.

In the present invention, since over-sintering of the Ag powder can be prevented, volume shrinkage is small, voids are not generated in the conductor, low-resistance internal wiring can be achieved, a dense conductor can be achieved, and the conductor resistance can be reduced. .

Further, in preparing such a conductive paste of Ag for internal wiring, the average particle size is stabilized by calcining and forming a substantially spherical Ag powder formed by a chemical reduction method to have a mean particle size of 5 to 25 μm. Can form a substantially spherical Ag powder.

Here, the Ag powder is scaly particles or the particle size is 20μ.
If it exceeds m, clogging occurs in the mesh of the screen during printing.

The present inventors have prepared a conductive paste having a different average particle size of Ag powder on a single plate of the above-described ceramic green sheet (approximately 0.8 mm thick and sintering temperature of 900 ° C.) of 300 mm × 35 mm.
Two patterns (thickness: 13 μm) of mm × 20 mm (for measuring warpage) and 0.3 mm × 10 mm (for measuring resistance) were formed, and the warpage and resistance were measured. The results are shown in Table 1.

In the measurement of the warpage, the height of the central portion of the substrate was obtained with a warp gauge, and the value obtained by subtracting the thickness of the substrate from this height was used as the warpage. The resistance was measured by an ohmmeter by a four-terminal method.

As is apparent from the sample numbers 1 to 3, the average particle size of Ag is 5
If it is 2525 μm, the warp is 0.02 mm or less, which can be substantially ignored, and can be used without any problem even with a multilayer wiring circuit board 10 on which a required number of ceramic green sheets are laminated.

In addition, no voids are formed in the wiring conductor, the wiring conductor is in a dense state, the resistance value is extremely low at 3.0 to 3.5 mΩ / mm, the variation is small, and it is easy to cope with a high-speed signal of the circuit.

On the other hand, the average particle size of Ag is 0.5 to 2.0 μm as in Sample Nos. 4 to 6 and smaller in comparison with the invention, the warpage is as large as 0.58 to 3.05 mm and the resistance value is 3.5.
As a whole, it is as large as 〜30 mΩ / mm, and there is a lot of variation. In a circuit board on which a required number of ceramic green sheets are laminated, disconnection of internal wiring due to warpage, poor appearance, and the like occur. In addition, in sample numbers 4 and 5,
Although the warpage is larger than that of the product of the present invention, the reason why the size is smaller than that of the sample No. 6 is that if the particle size of Ag is 1 μm or less as described above, it easily becomes a sintered state and the volume shrinks. As a result, voids are generated in the conductor, and in an extreme case, the sintered conductor is scattered on the substrate, and no extreme warpage occurs.

In order to form the particle diameters of Sample Nos. 1 to 3, Sample No. 1 (Ag average particle diameter of 56 μm) was prepared in Comparative Example 5.
Ag powder was calcined for 180 hours for 1 hour. For Sample No. 2 (Ag average particle size 15 μm), the Ag powder of Comparative Example 5 was
Calcination was performed for 1 hour at ℃. Sample No. 3 (Ag average particle size 25 μm)
Then, the Ag powder of Comparative Example 5 was calcined at 250 ° C. for 1 hour.

Although the above-mentioned ceramic green sheet has been described using magnesium oxide, aluminum oxide, and silicon oxide as main components as a glassy frit and using alumina as a ceramic component, such a glassy ceramic is
It is used as a material that can be sintered at a low temperature of about 800 to 950 ° C, and can be used for any glassy ceramic and green sheet as long as it is a glass ceramic material for low temperature firing within the above temperature range. The invention is applicable.

Further, the above-mentioned conductive paste is an Ag paste using Ag powder.
A system conductive paste, for example, an Ag-Pd paste may be used.

〔effect〕

As described above, according to the present invention, as the internal wiring of the multilayer wiring circuit board composed of the glass ceramic component, the conductive paste of Ag made of substantially spherical silver powder having an average particle diameter of 5 to 25 μm was used. , With the substrate material of the multilayer wiring circuit board
The difference in the behavior of the sintering reaction with Ag is small, there is no warpage of the entire substrate, and a dense conductor is achieved, resulting in a low-resistance multilayer wiring circuit substrate.

Also, as the internal wiring of the multilayer wiring circuit board, 150 to 300
Ag powder with an average particle size of 5 to 25 μm can be easily and accurately produced without warpage, and has a dense conductor because it is manufactured by using silver powder calcined at ℃ as a conductive paste. This is a method for manufacturing a low-resistance multilayer wiring circuit board.

[Brief description of the drawings]

 FIG. 1 is a sectional view of a multilayer wiring circuit board according to the present invention. 10 Multilayer wiring circuit board 1a, 1b Ceramic substrate 2a, 2b Internal wiring 3a, 3b Through hole 11a, 11b Ceramic green sheet

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05K 3/46 H05K 1/09

Claims (1)

(57) [Claims] 1. An average particle size of 5 to 180 ° C. by calcining at 180 to 250 ° C.
A desired internal wiring pattern is printed on a ceramic green sheet composed of a vitreous frit component and a ceramic component using a conductive paste obtained by mixing a silver powder grown in a substantially spherical shape of 25 μm and an organic vehicle. A method for manufacturing a multilayer wiring circuit board, comprising a step of laminating a plurality of ceramic green sheets and then performing a firing treatment.