JPH10242623A - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic circuit board for suppressing a warp deformation of the board by improving sintering properties of an insulating film covering a conductor formed on a board surface, and improving electric insulation of the film. SOLUTION: In the ceramic circuit board 10 obtained by covering a conductor 2 formed on a board surface with an insulating film 5, the film 5 is obtained by adding 35 to 60wt.% of glass component containing at least SiO2 , PbO, CaO and Na2 O, 40 to 60wt.% of Al2 O3 as ceramic filler and 0.001 to 0.02 pts.wt. of ZrO2 to 100 pts.wt. of the glass component and baking it. In this case, alumina and labradorite are existed as crystal phase.

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, and more particularly to a ceramic circuit board in which a conductor formed on the surface of a substrate is covered with an insulating film.

[0002]

2. Description of the Related Art Conventionally, when a conductor such as Ag, Cu, Au, W, or Mo is used as a wiring conductor for a circuit board,
In order to maintain the electrical insulation of the substrate, to protect the conductor formed on the surface of the substrate, to prevent short-circuiting due to solder, to prevent migration, etc., the conductor is covered with an insulating film.

For example, a ceramic circuit board is roughly divided into a ceramic substrate formed of alumina or the like, and the conductor is pasted, printed and fired, and an insulating material such as alumina or glass is formed on a circuit pattern formed by the paste. Is a multi-layer circuit in which a thick film circuit board on which an insulating film is formed by printing, baking, and firing, and a conductor film to be used as internal wiring are sandwiched and laminated with ceramic such as taped alumina, and the surface conductor is covered with an insulating film There is a substrate.

In recent years, cost reduction, high reliability,
From the viewpoint of high performance, a glass ceramic material that can be fired at a low temperature for the substrate material, and a conductor such as Ag that can be fired in the air for the conductor material and that has a low conductor resistance value are used for the inner layer and the surface layer conductor. Low-temperature fired multilayer substrates obtained by firing are mainly used.

[0005] The insulating film used for these ceramic multilayer circuit boards is an insulating film sintered at a low temperature,
An insulating film that can ensure electrical insulation, an insulating film that does not cause warpage of the substrate after firing, and the like can be given.

These characteristics are caused by the sintering property of the insulating film. If the sintering property becomes poor, poor insulation and warpage of the substrate occur. Therefore, the sintering property of the insulating film is an important factor. is there.

As a glass ceramic material used for a conventional low-temperature fired multilayer substrate, SiO ₂ 4 is used as a weight percentage.
0-65%, CaO 5-15%, PbO 10-25
%, MgO 0.5-10%, Na ₂ O 1-10%,
K ₂ O 1 to 10%, Al ₂ O ₃ 0 to 20%, B ₂ O
A composition comprising 35 to 60% of glass powder having a composition of _{30 to} 10% and ZnO of 0 to 5% and 40 to 65% of alumina powder is known (see Japanese Patent Publication No. 4-49497).

In the conventional ceramic circuit board, a molded body for a substrate is manufactured using a glass ceramic material, and a conductor paste serving as a surface conductor is applied to the surface of the molded body. It is produced by coating with a paste made of a glass ceramic material described above, and thereafter integrally firing a molded body for a substrate, a conductor paste as a surface conductor, and a glass ceramic paste as an insulating film.

[0009]

However, when an insulating film is formed using the above-mentioned glass ceramic material, a molded body for a substrate, a conductor paste serving as a surface conductor, and a glass ceramic paste serving as an insulating film are integrally fired. Then
Variations in sintering during firing occur in the insulating film, and there is a problem in that electrical insulation of the insulating film deteriorates due to insufficient sintering, and warpage of the substrate increases.

The ceramic circuit board according to the present invention improves the sinterability of an insulating film covering a conductor formed on the surface of the board,
An object of the present invention is to improve electrical insulation of an insulating film and suppress warpage of a substrate.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the deterioration of electrical insulation caused by poor sintering of an insulating film and the warpage of a substrate.
By adding a small amount of ZrO ₂ to a glass containing SiO ₂ , PbO, CaO, and Na ₂ O,
ZrO ₂ becomes a nucleus and promotes crystallization of the glass to a certain level, and can secure the melting property of the glass, thereby solving the density variation of the insulating film, especially the density reduction,
The inventors have found that the insulating property can be improved and the warpage of the substrate can be suppressed, and the present invention has been achieved.

That is, a ceramic circuit board according to the present invention is a ceramic circuit board in which a conductor formed on a substrate surface is covered with an insulating film.
35-60% by weight of a glass component containing O ₂ , PbO, CaO, and Na ₂ O, and A as a ceramic filler component
l ₂ O ₃ and 40 to 65 wt%, the by firing a composition to the glass component to 100 parts by weight obtained by adding a ZrO ₂ in an amount of 0.001 to 0.02 parts by weight, as a crystal phase At least Labradorite is present.

[0013]

According to the ceramic circuit board of the present invention, there is provided a ceramic circuit board comprising a conductor formed on a substrate surface covered with an insulating film, wherein at least SiO ₂ , PbO, C
aO-, with respect to the glass component containing Na ₂ O, ZrO
By adding a small amount of ₂ , ZrO
₂ acts as a nucleus to promote the crystallization of the glass component into labradorite, and by limiting the amount of ZrO ₂ to a certain amount or less, suppresses excessive crystallization of the glass component into labradorite and secures the meltability of the glass component. And Al ₂ O ₃
It is possible to improve the wettability with the particles.

As a result, even when the film is fired at a low temperature of 1050 ° C. or less, it is possible to obtain an insulating film having no variation in the density of the insulating film and having a high fired body density. Thus, warpage of the substrate on which the insulating film is formed can be suppressed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The insulating film of the ceramic circuit board of the present invention is made of at least SiO ₂ , PbO, CaO, Na ₂
35 to 60% by weight of a glass component containing O, 40 to 65% by weight of Al ₂ O ₃ as a ceramic filler component,
0.001 parts by weight of ZrO ₂ with respect to 100 parts by weight of the glass component
It is obtained by calcining a composition added at a ratio of about 0.02 parts by weight, and at least labradorite is present as a crystal phase.

The ceramic circuit board of the present invention has a conductor such as Ag, Cu, Au or the like formed on the surface, and a part or all of the conductor is covered with an insulating film. The ceramic circuit board of the present invention only needs to cover the conductor on the surface with an insulating film, and does not need to have internal wiring, internal conductors, and internal electrodes inside. Therefore,
The ceramic circuit board may be a single-layer body or a laminate having internal wiring, internal conductors, and internal electrodes.

Here, SiO ₂ , PbO, CaO, Na
_The reason why the glass component containing ₂ O is contained in an amount of 35 to 60% by weight is that when the glass component is less than 35% by weight (when Al ₂ O ₃ is more than 65% by weight), 10%
When calcined at a low temperature of 50 ° C. or less, a dense sintered body cannot be obtained, and when it is more than 60% by weight (when Al ₂ O ₃ is less than 40% by weight), a dense sintered body is obtained. I ca n’t
This is because sufficient material strength cannot be obtained. The ratio of the glass component to alumina is 44 to 50% by weight of the glass component and A in terms of obtaining a sufficient material strength from a dense sintered body.
It is desirable to l ₂ O ₃ containing 56 to 60 wt%.

Further, Z is based on 100 parts by weight of the glass component.
The reason for containing 0.001 to 0.02 parts by weight of rO _{2 is} that when the amount of ZrO ₂ is less than 0.001 part by weight, the crystallization of the glass does not proceed, the glass is deformed at the time of refiring, and If the amount is more than 0.02 parts by weight, crystallization of the glass proceeds excessively, hinders the fluidity of the glass required for densification, and a dense sintered body cannot be obtained. It is. ZrO ₂ moderately promotes crystallization,
From the viewpoint of obtaining a dense sintered body, the glass component 100
It is desirable to add 0.005 to 0.015 parts by weight based on parts by weight. In order to obtain such an amount of ZrO ₂ , it is necessary to strictly control so that ZrO ₂ is not mixed in the manufacturing process.

In the insulating film of the present invention, Al ₂ O ₃ , SiO ₂ , PbO, CaO, Na ₂
Labradorite composed of O and Al ₂ O ₃ precipitates. This labradorite phase has a Z
Crystallization is promoted by rO _{2 serving} as a nucleus. However, by the ZrO ₂ amount to be added to or less than 0.02 part by weight, labradorite phase, crystallization speed is moderately suppressed, Al ₂ to ensure the meltability of the glass component
It sufficiently wets the O ₃ particles, improves sinterability and promotes densification. Then, a Labradorite phase is precipitated between the Al ₂ O ₃ particles, and a sintered body in which ZrO ₂ particles are present in the Labradorite phase is obtained. Incidentally, a small amount of amorphous may be present.

Labradorite is used from Ab ₅₀ An _{50 to} Ab ₃₀ A
n ₇₀ (Ab: NaAlSi ₃ O ₈ , An: CaAl ₂ S
i ₂ O ₈ ). That is, Labradorite contains 30 to 50 mol% of NaAlSi ₃ O ₈ and CaA
The l ₂ Si ₂ O ₈ is made of 50 to 70 mol%.

In the insulating film of the present invention, as a glass component, 40 to 60% by weight of SiO ₂ and Al ₂ O in a weight ratio (when the glass component is 100) in the glass component.
₃ 0-20 wt%, CaO, 5.5 to 30 wt% ZnO and MgO are in total (CaO is an essential component), 10 to 25 wt% of _{PbO, Na 2 O, K 2} O and B ₂ O ₃ Is preferably a crystallized glass consisting of 2 to 30% by weight (Na ₂ O is an essential component). This is for the following reasons.

If the amount of SiO ₂ is less than 40% by weight in the glass component, the amount of precipitated crystals of the glass will be small, and a fired body with sufficient strength cannot be obtained. On the other hand, 60% by weight
In the above case, the melting property of the glass is deteriorated, the softening point is increased, and it is difficult to perform low-temperature firing at 1050 ° C. or lower.

Also, by incorporating Al ₂ O ₃ as a glass component, the wettability with the Al ₂ O ₃ filler during firing can be promoted and the crystallinity can be improved.
When the l ₂ O ₃ content is 20% by weight or more, the melting property of the glass becomes difficult and the softening temperature of the glass during firing becomes high. Labradorite is composed of Al ₂ O _{3 as} a filler component and SiO ₂ , PbO, and C as glass components.
It may be produced by reacting with aO and Na ₂ O.

In the glass component, CaO, ZnO and Mg
O (CaO is an essential component) is included because they can adjust the viscous properties of the glass. The reason why the total amount is 5.5 to 30% by weight is that C
When the total amount of aO, ZnO and MgO is less than 5.5% by weight or more than 30% by weight, it is not possible to obtain an appropriate viscosity of glass, and vitrification and crystallization are inhibited, resulting in a dense structure. This is because a sintered body cannot be obtained.

10 to 25% by weight of PbO in the glass component
When the content is less than 10% by weight, crystallization of the glass is difficult, and the content is 25% by weight.
If the amount is larger than the above range, the softening point of the glass becomes too low.

In the glass component, Na ₂ O, K ₂ O and B ₂
The total content of O ₃ from 2 to 30% by weight is less than 2% by weight or more than 30% by weight.
The softening point of the glass increases, and A
This is because the l ₂ O ₃ particles cannot be sufficiently wetted.

The insulating film of the present invention can be obtained as follows.

First, SiO ₂ powder, Al ₂ O ₃ powder, C
ACO ₃ powder, ZnO powder, prepared MgCO ₃ powder, PbO powder, Na ₂ CO ₃ powder, a K ₂ CO ₃ powder and B ₂ O ₃ powder, they were weighed in a predetermined amount as described above, these were mixed Put in a crucible, 1500 ~ 1600 ℃ 2
Melt for ~ 3 hours to produce mother glass. The mother glass is pulverized to a predetermined particle size.

Then, this glass powder and Al ₂ O ₃ powder are mixed, and a predetermined amount Zr is added to the glass powder.
Add and mix O ₂ powder. Here, the average particle size of the ZrO ₂ powder is desirably 3 μm or less. This is Zr
When the O ₂ powder is larger than 3 μm, the surface activity of the ZrO ₂ powder is small, so that it hardly becomes a nucleus during firing,
This is because crystallization to labradorite cannot be promoted.
ZrO ₂ has an average crystal grain size of 3 even in the sintered body.
It exists as μm or less. An organic binder and an organic solvent are added to the glass ceramic powder and mixed by a three-roll mill to form the glass ceramic powder into a paste. The glass ceramic paste is printed on a target surface conductor (including a wiring exposed on the surface layer) by a known printing method such as screen printing. Then, in an optimal firing atmosphere such as the air, at a firing temperature of 1050 ° C. or less,
Firing for up to 5 hours, simultaneously firing the substrate, the surface conductor, and the insulating film.

FIG. 1 is a sectional view of a ceramic circuit board using an insulating film. The substrate is a multilayer ceramic circuit board in which a plurality of glass ceramic layers are multilayered.

In FIG. 1, reference numeral 10 denotes a low-temperature fired ceramic circuit board. The low-temperature fired ceramic circuit board 10 includes a laminate (substrate) 1 and surface conductors 2, inner-layer conductors 3, and via-hole conductors 4 formed on the surface. The laminated body 1 including the insulating film 5 includes, for example, seven glass ceramic layers 1a to 1g, and an inner conductor 3 is formed between the layers 1a to 1g. In each of the glass ceramic layers 1a to 1g, a via-hole conductor 4 for connecting the inner layer conductor 3 in the thickness direction thereof and for connecting the inner layer conductor 3 and the surface layer conductor 2 is formed.

The method of manufacturing the ceramic circuit board 10 will be briefly described. First, a green sheet to be a glass ceramic layer is manufactured. For example, green sheet
A predetermined glass ceramic powder, an organic binder, an organic solvent and, if necessary, a plasticizer are mixed to form a slurry. The slurry is formed into a tape by a doctor blade method or the like, and cut into a predetermined size to produce a green sheet.

Next, through holes serving as via hole conductors 4 for connecting the inner layer conductors 3 and connecting the inner layer conductors 3 and the surface layer conductors 2 are formed at predetermined positions of the green sheet by punching or the like.

A conductive paste is filled into the through holes of the green sheets to be the glass ceramic layers 1a to 1f on the inner side, and a conductor film to be the inner conductor 3 having a predetermined shape is formed on the green sheets by printing.

Next, using a conductive paste, a conductor film serving as a surface conductor 2 having a predetermined shape is formed by printing on green sheets serving as the surface glass ceramic layers 1a and 1g. In addition, a glass ceramic paste that becomes the insulating film 5 having a predetermined shape is printed and dried so as to cover a part of the conductor film exposed on the surface.

The green sheets thus obtained are laminated according to the laminating order to form a laminated molded body, which is integrally fired. The ceramic circuit board 10 is manufactured by the above manufacturing steps.

[0037]

EXAMPLE First, SiO ₂ powder having a purity of 99% or more, Al
₂ O ₃ powder, CaCO ₃ powder, ZnO powder, MgCO ₃
A powder, a PbO powder, a Na ₂ CO ₃ powder, a K ₂ CO ₃ powder and a B ₂ O ₃ powder were prepared, and weighed in a predetermined amount so as to have a composition shown in Table 1 in terms of an oxide shown in Table 1. These are mixed in a ball mill using Al ₂ O ₃ balls,
It was put in a platinum crucible and melted at 1550 ° C. for 2 hours to prepare a mother glass. The mother glass was pulverized by the above-mentioned ball mill until it reached a predetermined particle size.

Then, this glass powder and Al ₂ O ₃ powder were mixed, and ZrO ₂ powder having an average particle size shown in Table 1 was added to the glass powder to obtain a glass component of 100%.
The amount shown in Table 1 was added to the parts by weight and mixed with the above-mentioned ball mill. Ethyl cellulose as an organic binder and 2,2.4-trimethyl-3,3-pentadiol monoisobutyrate as an organic solvent are added to the obtained glass ceramic powder, and three pieces are added until the aggregate of the powder and the organic binder disappears. The mixture was mixed by a roll mill, and the glass powder was made into a paste to prepare a glass ceramic paste for an insulating film.

Next, Al ₂ O is used as a ceramic filler.
₃ is a paste obtained by adding the above organic binder and organic solvent to a glass ceramic material containing lead borosilicate glass as a glass component, a ceramic filler at 55% by weight, and a glass component at a ratio of 45% by weight. ,
The layer was thinned by a doctor blade method to produce a green sheet for a substrate.

Thereafter, a through hole for forming a via hole conductor is formed at a predetermined position of the green sheet by punching or the like, and a conductive paste made of Ag is filled in the through hole to form an inner layer conductor having a predetermined shape. A conductor film was formed by printing.

On the other hand, a conductive film of a predetermined shape is printed and formed on a green sheet as an uppermost layer and a lowermost layer using a conductive paste made of Ag as a surface layer conductor, and covers a part of the conductive film exposed on the surface. Thus, the glass ceramic paste for an insulating film was printed and dried.

A plurality of green sheets filled with a conductive paste and formed with a conductive film having a predetermined shape were laminated, and the uppermost layer and the lowermost layer were partially covered with a conductive film serving as a surface conductor with a glass ceramic paste. Green sheets were laminated to produce a laminated molded body.

Thereafter, a binder removal treatment was carried out at 400 ° C. in the air, and the resultant was baked at 900 ° C. to produce a ceramic circuit board as shown in FIG. In addition, the glass ceramic layer 1
The thickness of a to 1 g is 1.5 mm, and the size of the ceramic circuit board is 10 mm in length, 10 mm in width, and 12 mm in thickness.
Met.

The warpage of the ceramic circuit board was evaluated by using a warp gauge, shifting the surface of the ceramic circuit board in the vertical direction, and obtaining the maximum value of the warp. The results are shown in Table 1.

The glass ceramic paste for forming the above-mentioned insulating film is applied by a doctor blade method, and is applied for about 1 m.
An m-thick coating film was produced. The coating film was dried, punched out to a diameter of 30 mm by a die press, and 400 ° C. in air.
, And fired at 900 ° C., and the fired body density was evaluated by Archimedes' method.

[0046]

[Table 1]

From Table 1, the density of the fired body of the insulating film of the sample of the present invention is as high as 3.17 to 3.20 g / cm ³ , which is stable. Is as small as 40 μm or less.

On the other hand, in Sample No. 13, the amount of ZrO _{2 was} 0.1%.
Since the amount is more than 02 parts by weight, excessive ZrO ₂ becomes a nucleus for crystallization during firing and inhibits densification, so that the density of the fired body is as low as 3.10 g / cm ^{3 as} compared with the sample of the present invention. I understand. Also, it can be seen that the density of the fired body decreases as the amount of ZrO ₂ increases.

Further, ZrO ₂ having an average particle diameter of 3 μm or more
In Samples Nos. 6 and 8 using powder, crystallization of glass did not proceed and the density of the fired body was low, but Zr having an average particle size of 3 μm or less was used.
It can be seen that the density of the fired body is higher in the sample using the O ₂ powder. In addition, about the insulating film of the sample of this invention, it was confirmed by X-ray diffraction that labradorite was precipitated.

For samples Nos. 3 to 13 and 19 in Table 1,
FIG. 2 is a graph showing the amount of ZrO ₂ on the horizontal axis and the density of the fired body on the vertical axis. From FIG. 2 and Table 1, by controlling the amount of ZrO ₂ , the variation in the density of the fired body of the insulating film,
In particular, it can be understood that a decrease in density can be solved, and warpage of a ceramic circuit board using the insulating film can be suppressed.

[0051]

According to the ceramic circuit board of the present invention, the composition of the insulating film is at least SiO ₂ , PbO, CaO, N
a small amount of ZrO _{2 with} respect to the glass component containing a ₂ O
By containing ZrO ₂ as a nucleus at a low temperature to promote crystallization of the glass component into labradorite, and by including a certain amount or less of ZrO ₂ , excessive crystallization of the glass component into labradorite is suppressed. In addition, the melting property of the glass component can be ensured, and the wettability with the Al ₂ O ₃ particles can be improved. As a result, it is possible to solve the unevenness of the density of the insulating film after firing, especially the decrease in the density, suppress the warpage of the ceramic circuit board, and provide a stable ceramic circuit board.

[Brief description of the drawings]

FIG. 1 shows a sectional view of a ceramic circuit board of the present invention.

FIG. 2 is a graph showing the amount of ZrO ₂ on the horizontal axis and the density of the fired body on the vertical axis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laminated body 2 ... Surface conductor 3 ... Inner layer conductor 4 ... Via hole conductor 5 ... Insulating film 10 ... Ceramic circuit board

Claims (1)

[Claims] 1. A ceramic circuit board comprising a conductor formed on a substrate surface covered with an insulating film, wherein the insulating film is
35 to 60% by weight of a glass component containing at least SiO ₂ , PbO, CaO and Na ₂ O, 40 to 65% by weight of Al ₂ O ₃ as a ceramic filler component, and ZrO ₂ to 100 parts by weight of the glass component 0.001
A ceramic circuit board, characterized in that at least labradorite is present as a crystal phase by firing a composition added at a ratio of 0.02 parts by weight.