JP2002198626A - Manufacturing method of low temperature baking ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low temperature baking ceramic circuit board whose wire bonding strength is ensured. SOLUTION: In a low temperature baking ceramic circuit board 10 for baking a ceramic green sheet lamination, a bonding pad 41 or a flip chip connection pad 42 is formed of conductive paste consisting of an Ag-base metallic element and amorphous glass frit at 800 to 1,000 deg.C, an operation point temperature of amorphous glass frit is lower than a baking temperature of ceramic green sheet, and amorphous glass frit is incorporated in conductive paste 0.5 to 10.0 wt.% (solid content ratio).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-layer glass-ceramic material or a multilayer substrate in which a conductor film serving as an internal wiring conductor is sandwiched and laminated, and a conductor serving as a surface wiring conductor is integrally sintered. And a method for producing a low-temperature fired ceramic circuit board.

[0002]

2. Description of the Related Art A low-temperature fired ceramic multilayer circuit board is made of a glass-ceramic material comprising glass and an inorganic filler such as alumina.
Au, which can be fired at 000 ° C. and is a low-resistance conductor material,
Ag, Cu, etc. can be used as a wiring conductor by integral sintering.

[0003] Regarding the relationship between the substrate material and the conductor film serving as the surface wiring conductor, the substrate must be firmly adhered without delamination or the like, and the substrate must be particularly sinterable so that the sintering behavior is similar and the substrate does not warp. Adjust the glass composition of the material,
In addition, it has been achieved by adjusting the conductive paste material of the conductor film to be the surface wiring conductor.

However, for example, the shrinkage start temperature of a conductive film formed of a conductive paste containing Ag starts at about 600 ° C. or less, and the shrinkage end temperature becomes about 750 to 800 ° C., and a substrate made of a general glass-ceramic material is used. Since the shrinkage on the side does not conform to the behavior of shrinking with a delay of 800 to 1000 ° C., for example, the softening or crystallization reaction of the glass of the glass-ceramic material is performed around the shrinkage end temperature of the conductive film. Warpage occurs.

Japanese Patent Laid-Open Publication No. Hei 10-215046 discloses a low-temperature fired ceramic circuit board formed with a surface wiring conductor using a conductive paste containing a glass frit having a softening point lower than the sintering start temperature of the ceramic substrate. Have been.

According to the structure of the invention, the sintering reaction of the Ag-based conductor material can be delayed at the same time as the sintering reaction of the glass-ceramic material, and as a result, the warpage of the substrate can be prevented. .

[0007]

By the way, the surface wiring conductor mainly constitutes a circuit wiring conductor on the surface of the base and an electrode pad such as a bonding pad to which a fine bonding wire of an IC chip is connected or a flip chip connection pad. Is configured. Here, when the sintering reaction of the Ag-based conductor material is slow, the grain growth of Ag is not sufficiently performed, and many grain boundaries of Ag are present on the surface of the electrode pad after firing. Since the grain boundary contains many impurities, a bonding thin wire is pressed against the bonding pad or Au is used.
When flip-chip connection is performed by pressing the bumps, there has been a problem that pure metal bonding is not performed on the surface and the bonding strength is reduced.

The present invention has been devised in view of the above-mentioned problems, and has as its object to integrate an internal wiring conductor and a dielectric layer together with a surface wiring conductor including a bonding pad or a flip chip connection pad. It is an object of the present invention to provide a method of manufacturing a low-temperature fired ceramic circuit board which can be sintered and has a high bonding strength.

[0009]

According to the present invention, a bonding pad or a flip chip connection pad is formed on a ceramic green sheet substrate by a conductive paste comprising a metal component containing Ag as a main component and an amorphous glass frit. While forming the conductor which becomes the surface wiring conductor film,
In the method for manufacturing a low-temperature fired ceramic circuit board obtained by firing the base and the conductor at 800 to 1000 ° C., the working point temperature of the amorphous glass frit is lower than the firing temperature of the ceramic green sheet base, and 95
0 ° C. and the amorphous glass frit is:
0.5 to 10.0 wt% in the solid content ratio of the conductive paste
% Is a method for producing a low-temperature fired ceramic circuit board.

The work point means a temperature at which the glass frit softens when heated and heated to a predetermined viscosity (about 10 ⁴ poise).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a low-temperature fired ceramic circuit board according to the present invention will be described below with reference to the drawings. FIG.
1 is a sectional view of a low-temperature fired ceramic circuit board according to the present invention. In FIG. 1, reference numeral 10 denotes a low-temperature fired ceramic circuit board, 1 denotes a laminated substrate, 2 denotes an internal wiring conductor formed in the laminated substrate 1, 3 denotes a via-hole conductor formed in the laminated substrate 1, and 4 denotes a laminated substrate. The surface wiring conductors 41 and 42 formed on the surface of the surface wiring conductor 1 are bonding pads and flip chip connection pads which are part of the surface wiring conductor 4, respectively.
5 is an IC chip component, 51 is a bonding thin wire for connecting the IC chip 5 to the bonding pad 41, 6 is a flip chip, 61 is a bump for connecting the flip chip 6 to the connection pad 42, and 7 is another bump. Electronic components.

The laminated substrate 1 has dielectric layers 1a to 1e made of a glass-ceramic material and internal wirings for achieving a predetermined circuit network and generating a capacitance component between the dielectric layers 1a to 1e. The conductor 2 is arranged.

In the dielectric layers 1a to 1e, via-hole conductors 3 penetrating the layers in the thickness direction are formed.

Further, a surface wiring conductor 4 is formed on the surface of the laminated substrate 1 on which the dielectric layers 1a to 1e are laminated.

The dielectric layers 1a to 1e are, for example, 850 to 1
Glass that can be fired at a relatively low temperature of around 050 ° C
-Made of ceramic material. With specific ceramic materials
Are cristobalite, quartz, corundum (α
Insulating ceramics such as mina), mullite and cordierite
Material, BaTiO_Three, Pb_FourFe_TwoNb_TwoO₁₂, TiO _Two
Such as dielectric ceramic materials, Ni-Zn ferrite,
Mn-Zn ferrite (ceramic in a broad sense)
And ceramic materials such as magnetic ceramic materials. What
Incidentally, the average particle size is 1.0 to 6.0 μm, preferably 1.
A material pulverized to 5 to 4.0 μm is used. Also, ceramic
The lock material may be used as a mixture of two or more kinds. In particular,
The use of corundum is advantageous in terms of cost.

More specifically, the glass component frit is subjected to a firing treatment to obtain a crystal of cordierite, mullite, anorthite, serdian, spinel, garnitite, willemite, dolomite, petalite, a substituted derivative thereof, or a spinel structure. What is necessary is just to precipitate the crystal phase of, for example, B ₂ O ₃ , SiO ₂ , Al
Glass frit containing ₂ O ₃ , ZnO, and alkaline earth oxide can be used. Such a glass frit has a wide vitrification range and a sag point of about 600 to 800 ° C.

The thickness of each of the dielectric layers 1a to 1e is, for example, about 100 to 300 μm.

The via-hole conductor 3 is made of an Ag-based material (Ag alone,
Ag-Pd, Ag-Pt, or other Ag alloy) as a main component, and the diameter of the via-hole conductor 3 can be any value. However, in order to increase the diameter and lower the resistance,
It is 80 to 350 μm.

The glass components substantially the same as the glass components in the dielectric layers 1a to 1e may be the same as the glass components contained in the dielectric layers 1a to 1e, or may have a slightly different composition ratio. Additives to improve properties,
The composition may be changed or deleted to the extent that the basic properties (thermal properties) are not significantly changed.

The surface wiring conductor 4 is made of Ag (Ag alone, A
(Ag alloy such as g-Pd, Ag-Pt, etc.) as a main component. A predetermined circuit wiring conductor is mainly formed on the surface of the laminated substrate 1 and an IC is formed through a bonding wire 51 of Al or Au. It serves as a bonding pad 41 to which the chip 5 is bonded, a connection pad 42 to which the flip chip 6 is bonded, a connection pad for the electronic component 7 which is bonded via solder, and a thick film resistor film, a thick film capacitor element. It becomes a terminal electrode. In particular, in connection with the internal wiring conductor 2, the surface wiring conductor 4 is connected to the via-hole conductor 3 exposed from the dielectric layer 1a. The electronic component 7 can be exemplified by an electronic device or a transistor.
Are connected via solder.

The present invention is characterized in that the surface wiring conductor 4
At least, the bonding pad 41 or the flip chip connection pad 42 is composed of a metal component containing Ag as a main component and an amorphous glass frit, and the working point temperature of the amorphous glass frit is lower than the firing temperature of the ceramic green sheet. And in the range of 700 to 950 ° C.,
The amorphous glass frit has a solid content (metal component and glass component) ratio of 0.5 to 10.0 in the conductive paste.
wt%.

Next, a method of manufacturing the low-temperature fired ceramic circuit board 10 will be described.

First, a large-sized green sheet to be used as the dielectric layers 1a to 1e of the laminate 1, an internal wiring conductor 2, a conductive paste of, for example, Ag for forming the via hole conductor 3, and a surface wiring conductor 4 are formed. For example Au system, A
A glass paste for forming a g-based conductive paste is prepared.

Here, the Ag-based conductive paste of the via-hole conductor 3 and the internal wiring conductor film 2 is made of an Ag-based paste (Ag alone, A
Ag alloys such as g-Pd) powder, borosilicate low melting point glass frit, organic binder such as ethyl cellulose,
What mixed the solvent homogeneously is used. In particular, the via-hole conductor 3 is made of an Ag-based material, β-quartz, a dielectric layer 1a.
To 1e are substantially the same as the glass components of the dielectric layer constituting the dielectric layer.

The green sheet has a plurality of circuit board regions so that a plurality of circuit boards can be extracted, and is made of a glass-ceramic material. For example, ceramic powder, frit of low melting glass component, organic binder,
The slurry obtained by uniformly kneading the organic solvent is tape-formed to a predetermined thickness by a doctor blade method, and cut into a predetermined size to form a sheet.

The composition ratio of the above-mentioned ceramic material and glass material is 10 to 98 wt%, preferably 30 to 95 wt%, for firing at a relatively low temperature of 850 to 1050 ° C. 2-90wt
%, Preferably 5 to 70 wt%.

It is necessary to give importance to the wettability of the organic binder with the solid content (ceramic powder, frit of the low melting point glass component), and the organic binder is thermally decomposable so that it can be burned off in a relatively low temperature and short firing step. Excellent ones are preferable, and ethylenically unsaturated compounds having a carboxyl group and an alcoholic hydroxyl group such as acrylic acid or methacrylic acid-based polymers are preferable.

As the solvent, an organic solvent or an aqueous solvent can be used. For example, in the case of an organic solvent,
For example, 2,4-trimethyl-1,3-pentadiol monoisoventate or the like is used. In the case of an aqueous solvent, it needs to be water-soluble, and the monomer and the binder include a hydrophilic functional group such as carboxyl. A group has been added.

The amount of addition is 0.5 to 300 in terms of acid value.
And preferably 0.5 to 100. If the added amount is small, the solubility in water and the dispersibility of the powder of the fixed component deteriorate, and if the added amount is large, the thermal decomposability deteriorates. In consideration of the above, it is appropriately added within the above range.

Next, a through hole serving as a via hole conductor 3 is formed in each circuit board region of the green sheet serving as the dielectric layers 1a to 1e by punching. At the same time, a conductor serving as the via-hole conductor 3 is formed in the through hole by printing and filling with an Ag-based conductive paste, and particularly, a conductor serving as the internal wiring conductor 2 is formed on the green sheet serving as the dielectric layers 1b to 1e. The film is formed by printing and drying an Ag-based conductive paste. On the green sheet serving as the dielectric layer 1a, a conductor film serving as the surface wiring conductor 4 is formed of Ag.
It is formed by printing and drying a system conductive paste.

Next, a via hole conductor 3 is provided in each circuit board area.
, A green sheet that becomes the dielectric layers 1b to 1e on which the conductor film that becomes the internal wiring conductor 2 is formed, and a green sheet that becomes the dielectric layer 1a on which the conductor film that becomes the surface wiring conductor 4 is formed. Laminated according to the order, for example, 60kg
A large-sized laminate is formed by being integrated by pressure bonding at a pressure of f / cm ² .

Next, division grooves are formed in the large-sized laminate in an unfired state so as to divide each circuit board region.

Next, the unfired large-sized laminate is simultaneously fired in an oxidizing atmosphere or an air atmosphere. The firing step includes a binder removal step and a sintering step.

In the binder removal process, the organic components contained in the green sheets serving as the dielectric layers 1a to 1e, the conductor film serving as the internal wiring conductor 2, the conductor serving as the via hole conductor 3, and the conductor film serving as the surface wiring conductor 4 are burned off. Is to let
For example, it is performed in a temperature range of 500 to 600 ° C.

In the sintering process, the glass component of the glass-ceramic green sheet is crystallized and simultaneously dispersed uniformly at the grain boundaries of the ceramic powder to give a certain strength to the laminated body, thereby forming the internal wiring conductor 2. A metal powder and an Ag powder of a conductive material of the conductive film, the conductor to be the via-hole conductor 3 and the conductive film to be the surface wiring conductor 4 are grain-grown to reduce the resistance, and are integrated with the dielectric layers 1a to 1e. is there. This is done until a peak temperature of 850-1050 <0> C is reached.

That is, at a temperature (eg, 550 ° C.) lower than the temperature (about 600 ° C.) at which the glass-ceramic material starts a sintering reaction (sintering shrinkage), the metal powder of the conductive material undergoes (sintering shrinkage). Will start.

Here, in the case of suppressing the warpage of the substrate, if the temperature range in which the glass starts to flow is too low, the sintering of the metal powder in the conductive paste cannot be sufficiently suppressed. A material having a property of decreasing the viscosity in a temperature range is desirable.

As a result, a large-sized circuit board having the internal wiring conductor 2 and the via-hole conductor 3 formed inside each circuit board area and the surface wiring conductor film 4 formed on the surface is achieved.

Next, the bonding fine wire 51 of the IC chip 5 is connected to the bonding pad 41 which is a part of the surface wiring conductor film 4 by wire bonding.
Au bumps 61 of flip chip 6 are provided on connection pads 42.
Is connected to the other part of the surface wiring conductor 4, and a thick film resistance element and various electronic components 7 are joined and mounted by soldering or the like.

Finally, a dividing process is performed along the dividing groove for dividing each circuit board. Thereby, a plurality of low-temperature fired ceramic circuit boards 10 shown in FIG.
Is extracted.

As described above, according to the present invention, the bonding pad 41 or the flip chip connection pad 42
The working point of the amorphous glass frit in the conductive paste is
Since the firing temperature is lower than the firing temperature of the ceramic green sheet, first, in the firing step, the glass frit softens and flows, and contributes to adhesion (joining) with the ceramic green sheet (substrate material). At this time, since the viscosity of the glass frit is sufficiently low, the metal particles which are the main components of the bonding pad 41 and the connection pad 42 are sufficiently wetted, and the growth of the Ag powder particles is promoted from a low temperature. The proportion of grain boundaries is reduced. For this reason, since the bonding fine wire 51 and the bonding pad 41 or the Au bump 61 and the connection pad 42 perform strong metal bonding, a low-temperature fired ceramic circuit board capable of strong bonding strength is obtained.

The glass frit contained in the conductive paste that becomes the bonding pad 41 or the flip chip connection pad 42 is an amorphous glass, for example, borosilicate glass. For example, when the glass frit is made of crystalline glass, crystallization starts before reaching the working point, so that the metal particles in the conductor are not sufficiently wetted and the grain growth cannot be promoted. The same applies to the case where the material does not soften at the firing temperature like quartz glass.

The amorphous glass frit is contained in an amount of 0.5 to 10% by weight based on 100% by weight of the conductor material. That is, if the content is less than 0.5 wt%, the effect of starting the grain growth of the Ag powder from a low temperature of the glass frit and improving the bonding strength cannot be sufficiently obtained. On the other hand, if it is more than 10 wt%, the glass component remains on the bonding pad 41 or the connection pad 42 after firing, and the bonding strength is reduced.

When the metal component is mainly composed of Ag, the firing temperature is selected from 850 ° C. to 950 ° C.
Working point of amorphous glass frit is 750 ° C to 950 ° C
C., preferably 800 ° C. to 900 ° C. That is, when the working point is lower than 700 ° C., the glass frit softens and flows and enters the substrate side, so that the effect of starting the grain growth of the Ag powder from a low temperature and improving the bonding strength is sufficiently obtained. Absent. On the other hand, when the working point is higher than 950 ° C., the glass component remains in the bonding pad 41 or the connection pad 42 after firing,
This is because the bonding strength is reduced.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements may be made without departing from the scope of the present invention.

For example, an amorphous glass frit having a working point temperature in the range of 700 to 950 ° C. has a solid content ratio of 0.5 to 0.5%.
The conductive paste containing 10.0 wt% may be used only for the bonding pad 41 or the connection pad 42, or may be used for all surface wiring conductors.

[0047]

Next, the present invention will be described in more detail with reference to examples.

The inventor manufactured a low-temperature fired ceramic circuit board 10 by the above-described manufacturing method. The thickness of the dielectric layer 1 was 100 μm × 5 layers, and the thickness of the internal wiring conductor 2 and the bonding pad 41 was 10 μm.

Sample Nos. 1 to 5 have a content of amorphous glass frit (borosilicate glass) in the conductive paste of 7
wt% and the glass working point was changed to 680-960 ° C.

Sample Nos. 6 and 7 used crystallized glass or quartz glass as the glass frit.

Sample Nos. 8 to 10 were prepared by setting the glass working point of the amorphous glass frit in the conductive paste to 830 ° C.
The content was changed from 1 to 7 wt%.

In Sample Nos. 11 to 14, the glass working point of the amorphous glass frit in the conductive paste was set to 830 ° C., and the content was changed to 0.3 to 15 wt%.

The wire bonding strength test of the low temperature fired ceramic circuit board 10 thus obtained was measured.
evaluated. Table 1 shows the results.

[0054]

[Table 1]

An Au wire 51 is connected to the bonding pad 41.
The wire bonding was performed at two places by thermocompression bonding while heating at 200 ° C., and a tensile test was performed to measure the wire bonding strength. The method of the tensile test is to hook the vicinity of the center of the part subjected to the first bonding and the second bonding on a jig,
A method of pulling in the vertical direction at a speed of one minute was adopted, and the strength when a break occurred on the second bonding side was defined as the wire bonding strength. Moreover, the tensile test was performed 30 times about each Example and the comparative example. When the average value of the wire bonding strength was 4 g or more, practical conditions were satisfied.

As shown in Table 1, when the content of the amorphous glass frit in the conductive paste is 0 to 10 wt% and the glass working point is in the range of 700 to 950 ° C. (Sample N
o. 2-4, 8-10 and 12-13), the wire bonding strength was 4 g or more.

On the other hand, when the glass working point of the amorphous glass frit was 680 ° C. (sample No. 1), the wire bonding strength was 3 g.

When the glass working point of the amorphous glass frit was 960 ° C. (Sample No. 5), the wire bonding strength was 3 g.

When crystallized glass or quartz glass was used (samples Nos. 6 and 7), the wire bonding strength was 2 g and 2 g, respectively.

When the content of the amorphous glass frit was 0.3 wt% (Sample No. 11), the wire bonding strength was 3 g.

The content of the amorphous glass frit is 1
When the weight was 5 g (Sample No. 14), the wire bonding strength was 3 g.

[0062]

As described above, according to the present invention, since the working point of the amorphous glass frit in the conductive paste is lower than the firing temperature of the ceramic green sheet, the glass frit is first softened in the firing step. Flows and contributes to adhesion (joining) with the ceramic electronic component element. At this time, since the viscosity of the glass frit is sufficiently low, the glass frit migrates to the interface between the metal and the insulator, which are the main components of the bonding pad or flip chip connection pad, to promote the grain growth of the Ag powder and reduce the ratio of the grain boundary. I do. Then, since the bonding fine wires and the bonding pads or the Au bumps and the flip-chip connection pads perform pure metal bonding, a low-temperature fired ceramic circuit board with high bonding strength can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a low-temperature fired ceramic circuit board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Low-temperature firing ceramic circuit board 1 Laminated board 1a-1e Dielectric layer 2 Internal wiring conductor 3 Through-hole conductor 4 Surface wiring conductor 41 Bonding pad 42 Flip chip connection pad 5 IC chip 51 Bonding thin wire 6 Flip chip 61 Bump 7 Electronic component

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H05K 3/46 H01L 23/14 CM F term (Reference) 4E351 AA07 BB31 CC12 CC22 CC31 DD05 EE02 EE03 EE09 GG01 GG11 5E343 AA02 AA23 BB25 BB72 BB74 DD02 ER39 FF11 GG01 GG18 5E346 AA02 AA12 AA15 AA22 AA32 AA51 CC18 CC39 DD13 DD34 EE24 EE27 EE29 FF45 GG06 GG09 HH11 HH13

Claims (1)

[Claims] 1. A ceramic green sheet substrate comprising:
a conductive paste comprising a metal component containing g as a main component and an amorphous glass frit is used to form a conductor serving as a surface wiring conductor film including a bonding pad or a flip-chip connection pad, and the base and the conductor are made 800
A method of manufacturing a low-temperature fired ceramic circuit board, which is fired at a temperature of about 1000 ° C., wherein a working point temperature of the amorphous glass frit is lower than a firing temperature of the ceramic green sheet base;
950 ° C., and the amorphous glass frit has a solid content ratio of 0.5 to 10.0 in the conductive paste.
a method for manufacturing a low-temperature fired ceramic circuit board, wherein