JPH04329207A - Conductor composition and wiring substrate - Google Patents

Abstract

PURPOSE:To increase the adhesion strength both at the initial time and after aging by causing the conductor of the conductor composition containing Ag, Pd and Pt to contain one kind selected from the group consisting of Au, Ru, Rh, and Ir. CONSTITUTION:A multi-layer wiring substrate 1 has an insulator substrate 4 consisting of an insulator prepared by laminating a plurality of layers and making them integral by burning. Within the substrate 4, an internal conductor 2 of a specified pattern is formed, and external conductors 3 are formed at positions where the conductor 2 is exposed on the surface of the substrate 4. Conductor composition is applied to the external conductor 3 prepared by dispersing into vehicle the conductor 2 containing Ag, Pd and Pt and inorganic binder, the conductor 2 further containing 0.1 to 5wt% of one kind selected from the group consisting of Au, Ru, Rh and Ir. The relative density of the conductor composition after burning is set to be 96% or less.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor composition for forming an external conductor on a wiring board on which an element such as a semiconductor integrated circuit is mounted, and a wiring board having an external conductor formed from this conductor composition.

0002

[Prior Art] In recent years, substrate materials and conductors have been heated to approximately 1000°C.
Development of wiring boards that can be obtained by co-firing at the following low temperatures is underway. The substrate material of such a low-temperature fired wiring board is mainly composed of an alumina glass composite. On the other hand, as the conductor material, instead of the conventional W or Mo, it is now possible to use an Ag-based material with low conduction resistance.

The internal conductor of such a wiring board is A.
However, since the outer conductor is soldered to the mounted component, the outer conductor is required to have good solder wettability, and Ag alloy-based materials are mainly used.

[0004] Furthermore, the adhesive strength after soldering must be sufficiently high both at the initial stage and after aging. Generally, aging deterioration is thought to be caused by the diffusion of Sn in the solder into the Ag. It needs to be something.

By the way, the conductor composition is obtained by dispersing conductive metal powder such as Ag-based metal powder and an inorganic binder containing glass frit in a vehicle.

[0006] For this reason, various proposals have been made to improve the aging characteristics by adjusting the glass composition and additives of the glass frit in a conductor composition for an external conductor (Japanese Patent Publication No. 62-32562). , Japanese Patent Publication No. 6
3-207001, JP-A-64-86404, JP-A-1-298090, etc.).

However, even with this method, the aging characteristics are still not sufficient, and further improvement is desired.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductor composition and a wiring board that have particularly excellent aging characteristics.

[0009]

[Means for Solving the Problems] Such objects are achieved by the following configurations (1) to (4).

(1) Ag and Pd and/or Pt
and an inorganic binder dispersed in a vehicle, the conductor comprising:
A conductor composition further comprising 0.1 to 5 wt% of at least one selected from Au, Ru, Rh, and Ir.

(2) The conductor composition according to (1) above, which has a relative density of 96% or less after firing.

(3) An alloy powder obtained by alloying the Ag, Pd and/or Pt, and at least one selected from Au, Ru, Rh, and Ir and pulverizing the alloy, and an inorganic binder. and dispersed in a vehicle (
The conductor composition according to 1) or (2).

(4) A wiring board in which an external conductor is formed using the conductor composition according to any one of (1) to (3) above.

[0014]

[Operation] In the present invention, in the conductor composition, Ag and Pd
For conductors containing Au, R and/or Pt,
at least one selected from u, Rh and Ir.
It is contained in an amount of 1 to 5 wt%. Therefore, when this is fired to form an external conductor and soldered, the presence of the above elements prevents Sn in the solder from forming an intermetallic compound with Ag, so Sn diffuses into the Ag. is prevented. In addition, the presence of the above elements increases the sintering temperature and inhibits the sinterability of the conductor, so the conductor film becomes porous (relative density 96% or less) and P between Sn and Pd.
Intermetallic compounds such as dSn3 .PdSn2 or PtSn2 between Sn and Pt are easily formed, thereby relieving the stress associated with the diffusion of Sn into Ag. Originally, Pd and Pt were considered to be the main components of conductors for the purpose of alleviating this stress.
The presence of Au etc. makes this effect extremely high.

[0015] This greatly improves the effect of preventing aging deterioration. At this time, the above elements can be added separately from the conductor, but Ag, Pd and/or Pd
It is preferable to form an alloy with t, and it is preferable to crush this to produce a conductor composition.

Furthermore, JP-A-1-274308 states that ``at least 95% by weight of silver powder, 1 to 1% by weight of ruthenium powder,
A conductive paste composition comprising a conductive powder comprising 4% by weight and 1-4% by weight of palladium powder, and a printing vehicle. ' has been disclosed.

[0017] It is said that this makes it possible to obtain a material that is inexpensive, has a low resistivity, and has a firing temperature high enough to be fired at the same time as the green sheet.

[0018] The composition disclosed in the above-mentioned publication and the composition of the present invention are identical in terms of their structure when a conductor containing Ag and Pd is used and Ru is contained in the present invention.

However, the material disclosed in the above-mentioned publication is used as an internal conductor, as shown in the examples thereof, and its purpose is clearly different from that of the present invention, which is used as an external conductor.

[0020] Therefore, the aging characteristics of the present invention are not even suggested.

[0021]

[Specific Configuration] The specific configuration of the present invention will be explained in detail below. The conductor composition of the present invention contains Ag and Pd and/or Pt, which are the basic composition of the conductor. That is, it contains any one of Ag-Pd, Ag-Pt, and Ag-Pd-Pt alloys.

[0022] As described above, by using an Ag alloy, it is possible to obtain the effect of improving migration resistance and solder eating resistance in the case of Pd, compared to using Ag alone.
In the case of t, the effect of extremely good solder wettability can be obtained by adding a small amount.

[0023] In such an Ag alloy, Ag, Pd,
The proportion of Pt is determined appropriately depending on the purpose, but Ag-
In the Pd alloy, the Pd content is preferably 5 to 25 wt%. When the Pd content is less than 5 wt%,
This is because the effect of adding Pd cannot be obtained, and if it exceeds 25 wt%, the conductivity of the conductor deteriorates.

[0024] Furthermore, in the Ag-Pt alloy, the Pt content is preferably 0.5 to 5 wt%. If the Pt content is less than 0.5 wt%, the effect of Pt addition cannot be obtained, and if it exceeds 5 wt%, the conductivity of the conductor deteriorates, resulting in high cost.

[0025] In the Ag-Pd-Pt alloy, the Pd content is 5 to 25 wt%, and the Pt content is 0.5 wt%.
It is preferable to set it to 5 wt%. With such a content, the effects of adding Pd and Pt can be obtained, and the conductor can also have sufficient electrical conductivity.

The conductor composition of the present invention is in the form of a paste, and in such a state Ag, Pd and/or Pt may exist separately. In this case, an Ag alloy is formed by subsequent firing.

[0027] Such an Ag alloy, or a metal that becomes an Ag alloy as described above, is usually present in the form of particles in a paste-like composition.

[0028] The average particle size of the Ag alloy particles is 0.01 to 1
It is preferable to set it to about 0 μm. This is because if the average particle diameter is less than 0.01 μm, the shrinkage rate of the conductor becomes too large, and if it exceeds 10 μm, the printability and dispersibility of the conductor composition deteriorate. Further, it is preferable that the average particle size of the metal particles forming the Ag alloy is approximately 0.01 to 10 μm for all of the Ag particles, Pd particles, and Pt particles. The reason for this is that if the average particle size is less than 0.01 μm, the shrinkage rate will be insufficient, as in the case of the Ag alloy particles mentioned above, and if it exceeds 10 μm, the effect of improving migration resistance due to the addition of Pd will be reduced. This is because it becomes smaller.

[0029] In the present invention, Au, Ru, R
0.1 to 5 of at least one selected from h and Ir
wt%, preferably 0.5 to 4 wt%. With such a content, aging characteristics can be improved.

[0030] If the content of the above elements is less than 0.1 wt%, the effect of improving aging properties cannot be obtained, and 5 wt%
%, the initial adhesive strength will not be sufficient and the conductivity will not be sufficient.

[0031] The above elements have a high melting point (1000 to 2500
℃), and is not oxidized even when the firing temperature is reached. For this reason, it changes the properties of the conductor, prevents the formation of intermetallic compounds between Sn and Ag, and inhibits the diffusion of Sn into Ag. The membrane structure of the membrane is porous,
The formation of Sn--Pd or Sn--Pt intermetallic compounds can be facilitated and stress can be alleviated.

In fact, when fired to form a conductive film (layer), the relative density is 96% or less, preferably 85 to 94%, indicating that the film structure is porous.

[0033] Here, the relative density is the ratio (%) of the actually measured density to the theoretical density calculated theoretically from the composition of the conductor.
It is defined as The measured density at this time is
A conductor composition is layered on a substrate made of a material that does not allow the conductor components to diffuse and is fired.The volume (V) of the subsequent conductor layer is determined based on the Archimedes method, while the conductor layer is peeled off from the substrate to form a conductor. Determine the weight (W) of the layer and calculate W(g)/V(c
m3).

[0034] The metal elements Au, Ru, Rh, and Ir in the present invention include Ag-Pd, Ag-Pt, and Ag-Pd-P.
Although these metal elements may be separately added to the conductor of the t-alloy, it is preferable that these metal elements are alloyed with the conductor and added.

The effect of the present invention is further improved by alloying. Note that the average grain size of the alloy grains is 0 as described above.
．． 01 to 10 μm.

Vehicles used in the present invention include binders such as ethyl cellulose, nitrocellulose, and acrylic resins, solvents such as terpineol and butyl carbitol, other dispersants, and activators. Any one of these may be used. It is added as appropriate depending on the purpose.

[0037] Generally, the content of the vehicle in the conductor composition is about 10 to 70 wt%.

Further, the conductor composition may contain glass frit as an inorganic binder. The glass composition of glass frit is

[0039] PbO-B2 O3 -SiO2, Pb
O-B2 O3 -SiO2 -ZnO, PbO-B2
O3 -SiO2 -ZnO, etc., and the content thereof in the conductor composition is about 10 to 20 wt%.

Further, the glass is used as a powder having an average particle size of 0.1 to 10 μm.

When the average particle size is less than 0.1 μm, contamination with impurities during pulverization becomes significant, and when it exceeds 10 μm, printability tends to deteriorate.

Furthermore, additives other than glass frit include Al2 O3, Cr2 O3, CuO, Ti
O2, CoO, Bi2 O3, etc. can be mentioned. Note that among these, Bi2 O3 is vitrified during firing, and may be added after being vitrified depending on the case.

[0043] The conductor composition of the present invention preferably uses a pulverized alloy of the conductor and the above-mentioned metals, mixes this with an inorganic binder such as glass frit, and adds a binder and a solvent to this. It can be obtained by adding a vehicle such as and kneading these to form a slurry. Here, the viscosity of the paste composition is preferably adjusted to about 30,000 to 300,000 cps.

The conductor composition of the present invention is used by printing a predetermined pattern on a substrate and baking it.

FIG. 1 shows an example of the structure of a multilayer wiring board in which the conductor composition of the present invention is used as an external conductor. FIG. 1 is a partial cross-sectional view of a multilayer wiring board.

As shown in the figure, the multilayer wiring board 1 is made up of an insulating board 4 in which a plurality of layers are laminated and integrated by firing.
An internal conductor 2 having a predetermined pattern is formed inside the substrate 4, and an external conductor 3 is formed at a portion of the internal conductor 2 exposed on the surface of the substrate 4.

The constituent materials of the substrate 4 include alumina-borosilicate glass, alumina-lead borosilicate glass, alumina-barium borosilicate glass, alumina-calcium borosilicate glass, and others that can be fired simultaneously with the internal conductor 2 and the like. Low temperature sintered materials containing oxide aggregate and glass such as alumina-strontium borosilicate glass and alumina-magnesium borosilicate glass are preferred.

[0048] In such a substrate material, the glass content is generally preferably about 50 to 80 wt%.

The internal conductor 2 is usually multilayered and connected to the substrate 4.
They are electrically connected to each other via a through hole 5 formed in the thickness direction.

The outer conductor 3 is formed on the surface of the substrate 4,
It is used as a pad for soldering surface-mounted components 7 such as chip components such as chip inductors and chip capacitors, semiconductor integrated circuit elements, elements such as diodes, etc. with solder 6, or for conduction to resistor 8. . Note that an insulating coating layer may be formed to cover the surface.

The conductor composition of the present invention is applied to form the above-mentioned outer conductor 3.

[0052] The internal conductor 2 is preferably made of a conductor mainly composed of Ag, particularly Ag, since good conductivity is given priority. The internal conductor composition may contain a conductor and a glass frit in an amount of about 5 to 10 wt% based on the conductor.

Further, the film thickness of the internal conductor 2 is usually 5 to 20
The film thickness of the outer conductor 3 is usually 5 to 20 μm.
It is considered to be a degree. The conduction resistance of the inner conductor and outer conductor depends on their composition, but generally the former is 2 to 1
The latter is preferably about 10 to 30 mΩ/□.

Furthermore, the resistor 8 may contain a resistor such as ruthenium oxide, lead ruthenium pyrochlore, and glass frit.

Such a multilayer wiring board is manufactured, for example, as follows.

First, a green sheet to be used as a substrate material is prepared.

This green sheet is made by mixing a predetermined amount of aggregate such as alumina powder, which is a raw material for the substrate, and glass powder (for example, borosilicate glass), adding a binder resin, a solvent, etc. to this, and kneading these. The slurry is made into a slurry, and a predetermined number of green sheets having a thickness of about 0.1 to 0.3 mm are produced by, for example, a doctor blade method.

Next, through holes 5 are formed in the green sheets using a punching machine or a die press, and then a composition for internal conductors is printed on each green sheet by, for example, screen printing to form internal conductors in a predetermined pattern. A layer is formed and the through hole 5 is filled.

[0059] Next, the green sheets were stacked and heat pressed (approximately 40 to 120°C, 50 to 1000 kgf/c).
m2) to form a laminate of green sheets, and if necessary, the binder is removed, cutting grooves are formed, etc.

[0060] Thereafter, the green sheet laminate is baked and integrated in normal air at a temperature of about 800 to 1000°C to obtain a multilayer wiring board in which the internal conductor 2 is formed on the board 4.

Then, the external conductor paste is printed by screen printing or the like and fired to form the external conductor 3. Furthermore, the resistor material paste is printed and fired to form a resistor. Note that the external conductor 3 and the resistor 8 may be formed by co-firing together with the substrate.

Thereafter, predetermined surface mount components 7 are soldered to the external conductor 3, and if necessary, an insulating coating layer is formed to obtain the multilayer wiring board 1 shown in FIG. 1.

Note that the substrate may also be produced by a printing method instead of the green sheet method described above.

[0064] The above describes an example in which the present invention is applied to a multilayer wiring board, but the present invention is not limited to this, but can also be applied to a single layer board such as a co-fired wiring board. can.

[0065]

[Examples] Specific examples of the present invention will be described below.

Example 1 (1) Preparation of conductor composition Ag, Pd,
Pt is used, and for this conductor, Au, Ru, Rh, Ir
were added in the proportions shown in Table 1, melted and alloyed using a carbon melting furnace, and then pulverized using a ball mill or the like to obtain alloy particles with an average particle size of 0.1 to 10 μm.

[0067] 15 wt% of Bi2 O3 was added to this material.
, PbO-B2 O3 -SiO2 glass 1.5
wt%, and further added 20 to 40 parts by weight of an acrylic resin and a high boiling point solvent (terpineol) as a vehicle to 100 parts by weight of the conductor and kneaded to obtain conductor compositions 1 to 17 in Table 1. Ta.

(2) Preparation of green sheet The composition is α-alumina: 40 wt%, glass powder: 60 wt%, and the thickness is 1.
A green sheet with a diameter of 00 to 300 μm was produced (the glass in this case was Al2 O3 -B2 O3 -SiO
2 -MO system, where M=Ca, Ba, Sr, Mg).

(3) Preparation of wiring board After forming an Ag internal conductor on the green sheet, the green sheets were laminated by hot pressing to obtain a green sheet laminate. after that,
After degreasing this laminate, a wiring board was obtained by co-firing in air at a temperature of 900°C.

[0070] A conductor composition was applied to this wiring board by screen printing at a shrinkage rate of 15% and the dimensions after firing were 2 mm x
The pad was printed to a thickness of 2 mm and a film thickness of 12±2 μm, and baked at 850° C. in air.

[0071] For each of the obtained substrates, the adhesion strength of the conductor at the initial stage and after aging was examined as follows. In addition, the relative density was determined as follows.

(a) Adhesive strength test The test was conducted according to DuPont's peel test. Stretch a copper wire with a diameter of 0.8 mm in the horizontal direction of the conductor film and solder the part that overlaps with the conductor film, and then connect the copper wire extending from one end of the soldered end to the conductor film almost perpendicular to the surface to which the conductor film is applied. The membrane was pulled in the direction of peeling using a tensile tester, and the load at the time of peeling was read. For aging, the sample was left in a constant temperature bath at 150° C. for a predetermined period of time, and the load was read in the same manner.

(b) Using a relative density Pt substrate, the conductor composition is applied to the substrate in a size of 5 mm x 5
mm, 0.5 mm thick, and baked at 850°C.

[0074] The volume (V) of the conductor after firing was determined by the Archimedes method, the conductor was peeled off from the substrate, its weight (W) was measured, and the actual density was determined from W (g)/(cm3). Ta. Measurements were performed on five samples for each composition, and the average value was taken as the average value.

On the other hand, the theoretical density (g/cm3) calculated theoretically from the conductor components after firing was determined, and the actual density/theoretical density (%) was defined as the relative density.

[0076] These results are shown in Table 1. Table 1 also shows the values of conductor resistance.

[0077]

[Table 1]

From the results in Table 1, the effects of the present invention are clear. In addition, the product of the present invention has good solder wettability, etc.
There were no practical problems as an external conductor.

[0079]

[Effects of the Invention] The outer conductor of the present invention has high adhesive strength both initially and after aging, and has excellent aging characteristics.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a multilayer wiring board manufactured using the conductor composition of the present invention.

[Explanation of symbols]

1 Multilayer wiring board 2 Internal conductor 3 External conductor 4 Board 5 Through hole 6 Solder 7　Surface mount parts 8 Resistor

Claims (4)

[Claims] 1. A conductor composition for an outer conductor comprising a conductor containing Ag, Pd and/or Pt, and an inorganic binder dispersed in a vehicle, wherein the conductor further contains Au, Ru, Rh, and an inorganic binder. A conductor composition containing 0.1 to 5 wt% of at least one selected from Ir and Ir. 2. The conductor composition according to claim 1, which has a relative density of 96% or less after firing. 3. The Ag, Pd and/or Pt
and at least one selected from Au, Ru, Rh and Ir, and an alloy powder obtained by pulverizing the alloy and an inorganic binder are dispersed in a vehicle. Conductor composition. 4. A wiring board having an outer conductor formed using the conductor composition according to any one of claims 1 to 3.