JPH03284896A - Multilayer interconnection circuit substrate and manufacture thereof - Google Patents

Abstract

PURPOSE:To remove curvature of a substrate for reducing resistance of internal wiring by forming an internal wiring pattern inside a circuit substrate made of glass ceramics by using conductive paste consisting of specific silver powder and an organic vehicle. CONSTITUTION:Almost spheric Ag powder calcined at 150 to 250 deg.C and having an average powder diameter of 5 to 25mum and an organic vehicle are mixed and kneaded in homogeneity to obtain conductive paste. The subject substrate consists of hyaline frit formed by a doctor blade method and a ceramic component. A ceramic green sheet is press-cut in a prescribed shape to manufacture ceramic green sheets 11a, 11b... of a single plate. Next, through holes 3a, 3b... are formed in these prescribed positions, further, aforesaid conductive paste of Ag is screen-printed as the desired internal wirings 2a, 2b. The through holes 3a, 3b... are filled with this paste. A required number of these ceramic green sheets 11a, 11b... are laminated, compression.bonded and sintered.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a ceramic multilayer wiring circuit board, and particularly to a multilayer wiring having a low-temperature fired ceramic substrate made of a glassy frit and a ceramic component as the substrate material. A circuit board and a method for manufacturing the same.

[Conventional technology]

Generally, a multilayer wiring circuit board is made by laminating and pressing a sheet with a desired pattern printed on a ceramic green sheet using conductive paste of a high-melting point metal such as molybdenum or tungsten as internal wiring, and then baking it at about 1400℃. Ta.

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

Recently, gold (Au), silver (A
g) The use of a material with a relatively low melting point and low resistance, such as copper (Cu), is being considered.

Regarding substrate materials, the use of glass ceramic substrates (ceramic substrates for low-temperature firing) consisting of glassy frit and ceramic components that can be fired at low temperatures ranging from around 1400°C to less than 1000°C is being considered.

Under these circumstances, Ag is considered to be promising for internal wiring of multilayer wiring circuit boards using ceramics for low-temperature firing. Although Ag has the problem of migration, it is extremely inexpensive compared to Au, and compared to Cu, the depyriding (debinding) process for the organic binder in the paste is easier, and there are no manufacturing constraints. One example is that there are few.

[Problem to be solved by the invention]

However, the biggest problem when using Ag as the internal wiring of a ceramic multilayer wiring board for low-temperature firing is that there is a large difference in the degree of sintering reaction between the ceramic green sheet for low-temperature firing and the Ag paste. There are problems in that the entire laminated substrate may be warped and the conductor resistance value may become large. That is, an internal wiring pattern of Ag is formed on a green sheet of low-temperature fired ceramic,
After lamination and pressure bonding, when the conductor is fired at about 900° C. to integrally sinter, sintering continues even after the sintering reaction of Ag is completed, resulting in oversintering of Ag and generation of pores in the conductor.

The present invention has been devised in view of the above-mentioned problems,
The purpose is to use Ag as internal wiring.
It is an object of the present invention to provide a multilayer wiring circuit board having low-resistance internal wiring without any warping of the board due to a difference in the degree of sintering between the board and internal wiring.

[Specific means to achieve the purpose]

The specific means of the present invention taken to solve the above-mentioned problems is to use a conductive paste made of approximately spherical silver powder with an average particle size of 5 to 25 μm and an organic vehicle in a circuit board made of glass ceramic. This is a multilayer wiring circuit board characterized by having a formed internal wiring pattern.

In addition, a desired internal wiring pattern is printed on a ceramic green sheet consisting of a glassy frit and a ceramic component using a conductive paste made by kneading silver powder calcined at 180 to 250°C and an organic vehicle. This is a method for manufacturing a multilayer wiring circuit board, which comprises the steps of laminating a required number of ceramic green sheets and then firing them.

[Effect]

By the above-mentioned means, ceramic green sheets made of glass frit and ceramic components with a desired internal wiring pattern printed on the surface of the ceramic green sheets are laminated and sintered to form a multilayer wiring circuit board. The conductive material printed with the pattern is formed by printing a conductive paste of approximately spherical Ag powder with an average particle size of 5 to 25 μm, so the Ag powder does not become extremely oversintered, and the sintering The subsequent internal wiring conductor becomes dense, low resistance is achieved, and the substrate only warps.

The particle size of the above-mentioned Ag powder is about 10 times the normal particle size (1 to 2 μm). As a result, when the ceramic green sheet laminate is sintered at the same time, the sintering of the Ag powder is delayed compared to normal, and the temperature approximates the sintering temperature of the ceramic green sheet, reducing the difference in behavior. For example, the sintering temperature for ceramic green sheets varies slightly depending on the ingredients of the glass frit, but the temperature is 8.
The temperature is 50-950°C. On the other hand, with ordinary Ag powder, the sintering reaction is completed at about 300 to about 400'C;
Between 0°C and about 900°C, Ag is in an oversintered state.

In the present invention, by using approximately spherical Ag powder with an average particle size of 5 to 25 μm, the sintering start temperature is 700 μm.
~800°C, which can be approximated to the sintering temperature of ceramic green sheets.

Furthermore, since no over-sintering occurs, no voids are generated in the fired Ag conductor, and internal wiring with lower resistance than molybdenum or tungsten can be achieved.

Generally, Ag powder having a particle size of 2 μm or less is formed by a chemical reduction method as described above. In particular, 1μ
In the case of a conductive paste made by pasting Ag powder with a particle size of less than m, when it is sintered integrally with a ceramic green sheet after printing, the oversintering state of the Ag powder becomes extreme and the volume shrinks. As a result, pores are generated in the conductor after sintering, increasing the conductor resistance. As for warpage, these pores act to help prevent warpage, but it is fundamentally difficult to use due to the problem of conductor resistance.

In addition, although a conductive paste made by pasting Ag powder with a particle size of about 1 to 2 μm has fewer pores in the conductor, its sintering behavior is lower than the sintering temperature of glass-ceramic ceramic green sheets. As a result, warping initially occurs in the multilayer substrate after firing.

In addition, there is spherical powder produced by another manufacturing method, electrolytic method, but the spherical powder formed by this method has a large particle size of several tens of μm, and the scaly powder has irregular particle sizes and is flat. Because of this, the screen mesh becomes clogged when printing internal wiring patterns, making it impossible to print highly accurate wiring patterns.

As a result, as a conductive paste for internal wiring of a ceramic green sheet containing glassy frit, the average particle size was 5.
It is optimal to use approximately spherical Ag powder with a diameter of ~25 μm.

Such a substantially spherical Ag powder with an average particle diameter of 5 to 25 μm is achieved by calcining Ag powder using a chemical reduction method. That is, before turning small Ag powder with a particle size of 2 μm or less into a paste, it is important to calcinate it to grow the particle size of the Ag powder. The temperature of the calcination is 15
The temperature is 0 to 300C, preferably 180 to 2506C. As a result, the object of the present invention, which is a multilayer wiring circuit board with low internal wiring resistance and less warpage, can be achieved.

〔Example〕

Hereinafter, the multilayer wiring circuit board of the present invention will be explained in detail based on the drawings.

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

The multilayer wiring circuit board 10 of the present invention includes a ceramic substrate 1a.
, lb... and internal wirings 2a, 2b... Note that the internal wiring 2a on the ceramic substrate 1a and the internal wiring 2b on the ceramic substrate lb are made of a conductive material (same material as the internal wiring 2b) formed on the ceramic substrate 1b or filled through holes (shown by solid lines). It is electrically connected at 3b. Desired thick film circuit wiring 4, electronic components 5, etc. are adhered to and mounted on the front and back surfaces of the multilayer wiring circuit board 10 formed in this way, as necessary.

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

a ceramic substrate 1a constituting the multilayer wiring circuit board 10;
lb... is formed by sintering a ceramic green sheet formed by a doctor blade method using a glass-ceramic material obtained by kneading a mixture of a glassy frit and a ceramic component with an organic component. 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 each has a content of 70 wt% and 30 wt%, respectively.
It is mixed in the ratio of %. Further, as organic components, 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 glassy frit and the ceramic component described above and the organic component are homogeneously kneaded in a hole mill.

The internal wirings 2a, 2b, etc. described above are formed by sintering a conductive paste containing Ag as a main component. The conductive paste is constituted by homogeneously kneading a metal powder containing Ag as a main component and an organic component. Ag powder, which is a metal powder, has a small particle size (~
(less than 2 μm) is formed by calcining approximately spherical powder. This results in a substantially spherical powder with an average particle size of 5 to 25 μm.

Specifically, the calcination method for Ag powder involves putting Ag powder formed by a chemical reduction method into a crucible, and heating it in a constant temperature bath for 150 min.
Heat in the range of ~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-bentanediol monoisobutyrate, and the binder and vehicle are weighed and mixed,
Knead using three rolls. For example, the average particle size is 5-2
87 to 93% by weight of approximately spherical Ag powder of 5 μm, 7 to 8% by weight of an organic vehicle, and 10% by weight of a binder and 90% by weight of a solvent in the organic vehicle.

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

The ceramic green sheet formed by the above-described doctor blade method is press-cut into a predetermined shape to produce a single ceramic green sheet 11a111b... And each veneer ceramic green sheet lla
, llb... have a through hole 3 a- in a predetermined position.
, 3b, . . . are formed, and the above-mentioned Ag conductive paste is screen printed on the ceramic green sheets lla, 11b, . . . as desired internal wiring. At this time, the through holes 3a, 3b, . . . are also filled with Ag conductive paste. The filling method is to use the printing pressure of a screen printing squeegee, or to draw air under reduced pressure from the opposite side of the printing surface through the through holes 3a, 3b, etc., to apply the conductive paste to the through holes 3a, 3b, etc. ...,
to be sucked into.

Ceramic green sheets 11a and 11b on which desired internal wiring patterns are formed using conductive paste in this way.
Laminate the required number of sheets and press them together.

Finally, it is sintered at a peak temperature of 900° C. for 130 minutes to produce 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 the desired internal wiring pattern has an average particle size of 5 to 25 μm, the internal wiring 2a after sintering,
2b... becomes dense, low resistance is achieved, and the substrates 1aS lb... have no warpage, resulting in a multilayer wiring circuit board construction of 0.

By using a conductive paste with an average particle size of Ag powder of 5 to 25 μm, the temperature of the sintering reaction of Ag powder can be increased to 700 °C.
~800℃. In addition, the sintering reaction temperature of the glassy ceramic green sheets 11a, llb, etc. that can be fired at a low temperature is 850 to 950°C, and since the sintering reaction temperatures can be approximated, the sintering behavior There is less difference between the two, and there is less warping of the entire board.

The fact that there is no warping of the entire board, not only the external shape, but also
When the patterns of the internal wirings 2a, 2b, etc. are precisely formed, a stable multilayer wiring circuit board without any wiring breaks can be achieved.

On the other hand, in a normal conductive paste containing Ag powder with an average particle size of 2 μm or less, the sintering start temperature of the Ag powder is about 300 to 4006 C, and the sintering starts before the ceramic green sheet undergoes the sintering reaction. The binding reaction is completed. Since the temperature is further increased, the Ag powder becomes oversintered.

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

In addition, when creating such a conductive Ag paste for internal wiring, by calcining approximately spherical Ag powder formed by a chemical reduction method, it is possible to stably maintain an average particle size of 5 to 25 μm. substantially spherical Ag powder can be formed.

Here, the Ag powder may be scaly particles or have a particle size of 20
If it exceeds μm, the screen mesh will become clogged during printing.

The present inventors developed the above-mentioned ceramic green sheet of 30 mm x 35 mm (with a thickness of about 0.8 mm and a sintering temperature of 90 mm).
Conductive pastes with different average particle sizes of Ag powder were placed on a single plate at 0°C), measuring 20mm x 20mm (for measuring warpage) and 0°C.
．． Two patterns (thickness: 13 μm) of 3 mmXlOmm (for resistance measurement) were formed, and warpage and resistance were measured.

The results are shown in Table 1.

Regarding the measurement of warpage, the height of the center portion of the substrate was determined using a warp gauge, and the value obtained by subtracting the thickness of the substrate from this height was defined as the warpage. Further, the resistance value was measured using an ohmmeter using a four-terminal method.

As is clear from sample numbers 1 to 3 in Table 1, the average particle size of Ag is 5.
~25 μm, the warpage is 0.02 mm or less,
This can be substantially ignored, and even a multilayer wiring circuit board 10 in which a required number of ceramic green sheets are laminated can be used without any problem.

In addition, there are no holes in the wiring conductor, it is in a dense state, the resistance value is extremely low at 3.0 to 3.5 mΩ/IDO], and the variation is small, making it easy to support higher signal speeds in the circuit. Become.

On the other hand, for samples like sample numbers 4 to 6, which have an average Ag particle diameter of 0.5 to 2.0 μm, which is smaller than the invented product, the warpage is large, 0.58 to 3.05 mm. ,
In addition, the resistance value is generally large at 3.5 to 30[IlΩ/m], and there are many variations, and a circuit board made by laminating the required number of ceramic green sheets may have internal wiring breakage due to warping or poor appearance. etc. will occur.

In sample number 4.5, the warpage is larger than that of the product of the present invention, but the reason why it is smaller than that of sample number 6 is that as mentioned above, when the grain size of Ag is 1 μm or less, it is easily over-warped. The conductor becomes sintered, its volume shrinks, and voids occur in the conductor, and in extreme cases, the sintered conductor ends up scattered on the board, preventing extreme warping. .

In order to form the particle sizes of sample numbers 1 to 3, for sample number 1 (average particle size of Ag 5 μm), the Ag powder of Comparative Example 5 was calcined at 180'C for 1 hour. Sample number 2
(Average particle size of Ag 15 μm), A of Comparative Example 5
The g powder was calcined for 200'CI hours. Sample number 3 (Ag
(average particle size of 25 μm), the Ag powder of Comparative Example 5 was calcined at 250'C for 1 hour.

The above-mentioned ceramic green sheet was explained using magnesium oxide, aluminum oxide, and silicon oxide as the main components as the glassy frit, and alumina as the ceramic component.
It is used as a material that can be sintered at a low temperature of about 00 to 950°C, and the present invention can be applied to glass-ceramic green sheets of any material as long as it is a glass-ceramic material for low-temperature firing within the above-mentioned temperature range. is applicable.

Moreover, the above-mentioned conductive paste is made of Ag powder using Ag powder.
It may be a paste or an Ag-based conductive paste containing Ag as a main component as a conductor material, such as an Ag-Pd paste.

〔effect〕

As described above, according to the present invention, an Ag conductive paste made of approximately spherical silver powder with an average particle size of 5 to 25 μm is used as the internal wiring of a multilayer wiring circuit board made of a glass ceramic component. , there is little difference in the behavior of the sintering reaction between the board material of the multilayer wiring circuit board and Ag, there is no warping of the entire board, and a dense conductor is achieved, resulting in a low resistance multilayer wiring circuit board.

In addition, 150 to 3
Since the conductive paste is manufactured using silver powder calcined at 00℃, it is possible to easily and accurately produce Ag powder with an average particle size of 5 to 25 μm, without warping, and to create a dense conductor. The present invention provides a method for manufacturing a multilayer wiring circuit board with low resistance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a multilayer wiring circuit board of the present invention. 10 ・ ・ ・ la, 1b 2a, 2b a13b 11a,llb ・Multilayer wiring circuit board ・・・・・・Ceramic substrate ・・・・・・Internal wiring ・・・・・・Through hole ・・・Ceramic green sheet

Claims (2)

[Claims] (1) A multilayer wiring circuit board comprising a circuit board made of glass ceramic and having an internal wiring pattern formed from a conductive paste made of approximately spherical silver powder with an average particle size of 5 to 25 μm and an organic vehicle. (2) A desired internal wiring pattern is printed on a ceramic green sheet consisting of a glassy frit and a ceramic component using a conductive paste made by kneading silver powder calcined at 180 to 250°C and an organic vehicle. A method for manufacturing a multilayer wiring circuit board, which comprises the steps of laminating a required number of ceramic green sheets and then firing them.