JPH0737420A - Conductive paste composition and circuit board using conductive paste composition - Google Patents

Abstract

PURPOSE:To provide a conductive paste and a circuit board using such a conductive paste to form a terminal electrode or an external conductor which has a high adhesive strength after a heat cycle, and an excellent solder wettability. CONSTITUTION:This conductive paste is formed by dispersing and mixing Ag or a conductive material mainly of Ag; and an inorganic binder which consists of a glass frit and a metal oxide; in a vehicle. The inorganic binder composition is composed of 20 to 40wt.% of at least one sort selected from PbO and/or ZnO, 6 to 20wt.% if B2O3, 2 to 15wt.% of SiO2, and 30 to 72wt.% of CuO and/or TiO2. The PbO, ZnO, B2O3, and SiO2 of those components are all the glass frit component, and 0.35 to 10 pts.wt. is contained to 100 pts.wt. of the conductive material. The CuO and TiO2 are metal oxides other than the glass frit component, and 5 pts.wt. or less is contained to 100 pts.wt. of the conductive material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in circuit boards in general, and particularly in a conductor paste composition used for forming a terminal electrode or an outer conductor of a dielectric substrate for microwaves and a dielectric substrate of a filter. Regarding

[0002]

BACKGROUND OF THE INVENTION Conductor pastes are obtained by dispersing a conductive material, glass frit and an inorganic binder such as a metal oxide in a vehicle. Among them, the conductive material is made of silver, palladium, gold, platinum, copper, nickel or a mixture thereof. Of these, silver alloys are widely used because they are relatively inexpensive and can be fired in air.
As the number of parts used in the microwave band is increasing, the frequency of use of silver, which has the smallest specific resistance, is increasing.

Further, an inorganic binder such as glass frit and a metal oxide plays a role of adhering a silver sintering aid and a dielectric substrate, and acts as a permanent binder.

These conductor pastes become terminal electrodes or external conductors by a treatment such as baking on a ceramic element or the like, but their names are properly used depending on the application.
The obtained terminal electrodes and the like are soldered in order to secure electrical connection with other components. The adhesive strength after soldering needs to be sufficiently high both in the initial stage and after the heat cycle test, but the heat cycle test causes deterioration of the adhesive strength. This is because the heat cycle test is a test in which abrupt temperature changes are repeated, so that stress is generated at each interface due to the difference in linear expansion coefficient between the solder, the terminal electrode, and the dielectric. .
In particular, the stress from the solder is large, and this stress destroys the bonded portion between the terminal electrode and the dielectric, so that the bonding strength deteriorates.
In general, eutectic solder and high temperature solder are used together in a process that requires soldering several times. Of these, when high-temperature solder is used, the generated stress is larger than that when eutectic solder is used, so the degree of deterioration in adhesive strength also increases. Since the adhesion between the terminal electrode and the dielectric is governed by the reaction between the inorganic binder added to the conductor paste and the dielectric,
Various proposals have been made regarding inorganic binders. For example, in JP-A-1-298090, Bi2O3 is added. In this case, needle-like crystal substances peculiar to Bi2O3 addition are deposited in the reaction layer at the dielectric interface, and the initial strength is large due to the anchor effect. Although improved, it is very fragile against stress and its reaction layer portion is easily broken by the heat cycle. In addition, in JP-A-4-293214, various metal oxides are added in addition to the glass frit, but this not only causes insufficient solder wettability but also inhibits silver sintering. There are drawbacks such as the inability to secure electrical characteristics.

[0005]

SUMMARY OF THE INVENTION The present invention has been made under these circumstances, and has a high adhesive strength, particularly an adhesive strength after a heat cycle, and a terminal electrode or an outer conductor which is excellent in solder wettability. It is an object of the present invention to provide a conductor paste used in the above.

[0006]

The above objects are achieved by the present invention described in (1) to (9) below.

(1) A conductor paste composition in which a conductive material made of Ag or an alloy containing Ag as a main component and an inorganic binder containing a glass frit and a metal oxide are dispersed in a vehicle. The inorganic binder composition is at least one selected from PbO and / or ZnO: 20 to 4
0% by weight, B2O3: 6 to 20% by weight, SiO2: 2 to 15% by weight, at least 1 selected from CuO and / or TiO2
1 or more: 30 to 72% by weight, a conductor paste composition.

(2) The conductor paste composition as described in (1) above, wherein the content of the inorganic binder is 0.5 to 15 parts by weight with respect to 100 parts by weight of the conductive material.

(3) PbO and B2O in the inorganic binder
3, and SiO2 are constituents of the glass frit,
Content of 0.35 to 1 with respect to 100 parts by weight of the conductive material
The conductor paste composition according to claim 1, which is 0 part by weight.

(4) The conductor paste composition as described in any of (1) to (3) above, wherein the glass frit has an average particle size of 0.1 to 20 μm.

(5) CuO and / or TiO2 in the inorganic binder is a metal oxide which is not in a glass state, and the content thereof is 5 parts by weight or less based on 100 parts by weight of the conductive material. The conductor paste composition according to any one of (4).

(6) The average particle size of the metal oxide is 0.1.
The conductor paste composition according to any one of (1) to (5) above, having a thickness of 20 μm.

(7) The conductive material is at least 1 selected from Ag: 70 to 100% by weight and Pd and / or Pt.
1 or more: 0 to 30% by weight, The conductor paste composition according to the above (1) to (6).

(8) A circuit board having a terminal electrode or an external conductor formed by baking the conductor paste composition according to any one of (1) to (7).

(9) The circuit board as described in (8), which has a plating film on the surface of the terminal electrode or the conductor.

[0016]

The glass in the conductor paste composition of the present invention reacts with TiO2 or the like in the dielectric substrate, and P between the substrate and the terminal electrode.
A reaction layer containing bTi3O7 as a main phase is formed. Cu to this
The presence of O or the like in the reaction layer improves the strength of the reaction layer and suppresses the deterioration of the adhesion strength, especially the adhesion strength due to the heat cycle.

(Specific Structure) The specific structure of the present invention will be described in detail below.

The conductor paste composition of the present invention contains a conductive material and an inorganic binder. This inorganic binder serves as a permanent binder for the conductive material and is composed of glass frit and metal oxide.

In the present invention, the inorganic binder composition is at least one selected from PbO and / or ZnO: 20
-40% by weight, preferably 25-38% by weight, B2O3: 6-20% by weight, preferably 8-15% by weight, SiO2: 2-15% by weight, preferably 4-10% by weight, selected from CuO and TiO2. At least one or more:
It contains 30 to 72% by weight, preferably 40 to 68% by weight.

Further, PbO, CuO, and SiO2 are constituent components of the glass frit, and CuO and / or TiO
2 is a metal oxide which is not in a glass state. This inorganic binder contains substantially no Bi oxide or Mn oxide.

The reasons for limiting the composition of the inorganic binder are as follows.

When PbO is less than the above range, the sinterability of Ag is lowered, and good conductivity cannot be obtained. Further, when PbO exceeds the above range, glass float easily occurs on the electrode surface after baking Ag, and the solder wettability deteriorates. Note that part or all of PbO may be replaced with ZnO. Even in this case, the effect is the same, but it is particularly effective in improving the tensile strength after the plating treatment described in the examples. However, when PbO is contained, it is often used for a terminal electrode or the like that is not usually plated, because solder wettability becomes particularly good.

If B2O3 is less than the above range, vitrification becomes difficult, and if it exceeds the above range, the softening point of the glass becomes too low and the glass component excessively diffuses into the substrate, so that sufficient adhesive strength cannot be obtained. .

When SiO2 is less than the above range, vitrification becomes difficult, and when it exceeds the above range, the softening point of the glass becomes too high, and the glass remains in the electrode after baking to cause glass float, resulting in solder wettability. to degrade. The glass softening point having such a composition is about 400 to 650 ° C.

The content of the glass frit in the conductor paste composition is preferably 0.5 to 15% by weight, more preferably 1 to 8% by weight, based on 100 parts by weight of the conductive material. If the content of the glass frit is less than the above range, sufficient adhesive strength cannot be obtained, and if it exceeds the above range, the glass floats on the electrode surface after baking and the solder wettability deteriorates.

The average particle size of the glass frit is 0.1-2.
It is preferably 0 μm.

The inorganic binder includes, in addition to glass frit, inorganic particles such as metal oxides which are not in a glass state. Such inorganic particles include CuO and / or TiO2
Among these, CuO is particularly preferable.
Is preferred. CuO acts as a sintering aid and a strength enhancer for PbTi3O7 which is a reaction product, and improves the strength of the reaction product.

The content of these inorganic particles depends on the conductive material 10.
It is preferably 5 parts by weight or less with respect to 0 parts by weight. When the content exceeds 5 parts by weight, the inorganic particles themselves do not diffuse into the matrix and thus remain in the terminal electrode, and the inorganic particles float on the electrode surface. Therefore, the solder wettability is deteriorated.

The average particle size of these inorganic particles is 0.1 to 2
It is preferably 0 μm.

When Bi oxide is contained, it reacts with TiO2 or the like in the dielectric substrate, and a fragile Bi2Ti2O7 layer is deposited between the terminal electrode and the substrate, so that the adhesive strength is deteriorated. Furthermore, when Mn oxide is added to this, the formation of this layer becomes remarkable, and the adhesive strength deteriorates severely.

In the present invention, Ag is used as the conductive material when used in the microwave band or when high Q characteristics are obtained. When used for other purposes, it may contain Pd and / or Pt. At this time, the content of these should be 30% by weight or less. If it exceeds the above range, the conductor resistance becomes too large, and not only the electrical characteristics of the circuit usually used are not satisfied, but also the solder wettability is extremely lowered. The average particle size of these conductive material particles is preferably about 0.01 to 10 μm. The reason is that if the average particle diameter is less than 0.01 μm, the shrinkage ratio becomes too large, and if it exceeds 10 μm, the printability and dispersibility of the conductor paste composition deteriorate.

The vehicle in which the conductive material and the inorganic binder are dispersed is a binder such as ethyl cellulose, nitrocellulose, acrylic resin, a solvent such as terpineol, butycarbitol, and other dispersants and activators. Are appropriately selected from the above.

Generally, the content of the vehicle in the conductor paste composition is about 10 to 70% by weight.

The conductor paste composition of the present invention is prepared by mixing conductive material particles and an inorganic binder, adding a vehicle such as a binder and a solvent, and kneading these to form a slurry. To be done. The viscosity of the conductor paste composition is 3
It is recommended to prepare about 10,000 to 300,000 cps (centipoise).

The conductor paste composition of the present invention is used for a terminal electrode of a dielectric substrate or an outer conductor. It can also be used for a cylindrical dielectric body in which electrodes are formed entirely or partially by dipping or the like.

Although it is usually used as a terminal electrode or an external conductor which is not plated, plating can also be carried out. Plating is usually Cu plating film, Ni plating film, Sn
The plating film or the Sn-Pb (solder) plating film is formed in this order. The Cu and Ni plating films are provided to prevent the terminal electrode from being Ag-eaten. However, the Cu plating film is appropriately used if necessary. Also, Sn or Sn
The -Pb plated film is provided to improve solder wettability and Ag erosion by solder.

The dielectric constant of a dielectric substrate used for microwave resonators, filters and the like is about 10 to 100, and Mg-Ti oxide, Sr-Ti oxide and Ba are used.
-A desired dielectric constant is obtained by using Ti oxide as a main component and adding various metal oxides as necessary. The conductor paste composition of the present invention is compatible with any dielectric substrate. INDUSTRIAL APPLICABILITY The conductor paste composition of the present invention is used as a terminal electrode or an outer conductor of a dielectric substrate used for a dielectric resonator and a filter for a microwave band, and also an electrode by dipping or the like in whole or in part. External parts such as a wiring board for mounting surface mount parts of various elements such as cylindrical dielectrics, dielectric chips, chip inductors, chip capacitors, etc., semiconductor integrated circuit elements, diodes, etc. It can also be adapted to a conductor. However, since the terminal electrode or the external conductor formed on the dielectric substrate used for the dielectric resonator and filter for the microwave band is required to have strong adhesiveness even after the heat cycle, the present invention The conductor paste composition is particularly suitable for forming a terminal electrode or outer conductor of a dielectric used in the microwave band.

[0038]

EXAMPLES Specific examples of the present invention will be described below.

(Example 1) Preparation of conductor paste composition A conductor paste composition was prepared by kneading a conductive material, an inorganic binder and a vehicle. Ag (average particle size 0.2
glass frit (average particle size 0.7 μm) and metal oxide (average particle size 0.2 μm) as the inorganic binder.
The vehicle used was an ethyl cellulose resin and a high boiling point solvent (terpineol). Table 1 shows the composition ratio of the inorganic binder and the content of the inorganic binder with respect to 100 parts by weight of the conductive material.
Shown in. The vehicle is 2 parts for 100 parts by weight of the conductive material.
0-40 parts by weight was added.

[0040]

[Table 1]

The conductor paste composition was printed on the dielectric substrate by a screen printing method at a reduction ratio of 25% so that the size of the pad after baking was 2 mm × 2 mm and the film thickness was 15 ± 2 μm. Baking at 900 ° C. in air.
The dielectric substrate used was a Ba-Ti-Nd-Bi oxide. The adhesive strength of the terminal electrode at the initial stage and after the heat cycle, and the solder wettability of the terminal electrode were examined as follows.

(A) Adhesive strength test Initial strength was 20 mm measured by soldering a 0.6 mmφ lead wire to the center of the pad and using a tensile tester in the vertical direction.
The load at the time of breaking was read by pulling at a speed of / min. For the strength after heat cycle, a heat cycle test was conducted with a lead wire attached by solder, and then a tensile test was conducted in the same manner to read the load at breakage. The heat cycle test has a lower limit temperature of -40 ° C, an upper limit temperature of + 85 ° C
100 cycles were carried out under the condition of holding time of 30 minutes at each temperature. Two kinds of solder, eutectic solder and high temperature solder, were prepared. Table 2 shows the composition and melting temperature of the solder.

[0043]

[Table 2]

(B) Solder wettability The eutectic solder was dipped in the molten solder at 235 ° C. and the high temperature solder was dipped in the molten solder at 280 ° C. for 2 seconds, and the wetted area ratio of the pad was evaluated. The results of each test are shown in Table 3.

[0045]

[Table 3]

(Example 2) Ni and Sn plating films were formed on the terminal electrodes obtained in Example 1, and the adhesive strength and solder wettability at the initial stage and after the heat cycle were evaluated. Table 4 shows the content of the inorganic binder with respect to 100 parts by weight of the conductive material.

[0047]

[Table 4]

The results of each test are shown in Table 5.

[0049]

[Table 5]

(Embodiment 3) A terminal electrode or an outer conductor is formed on a dielectric substrate by using the conductor paste obtained according to the present invention. As a result, the semi-wetting property is excellent and the initial and heat are obtained. An extremely reliable circuit board having sufficient adhesion strength with the board after the cycle was obtained.

From the above results, the effect of the present invention is clear.

[0052]

EFFECT OF THE INVENTION If the conductor paste composition of the present invention is used to form a terminal electrode or an external conductor of a dielectric substrate used for a microwave resonator, a dielectric resonator, a filter, etc., solder wettability is obtained. It is possible to realize an element or a substrate having good reliability and having a sufficiently high adhesive strength with the substrate in the initial stage and after the heat cycle.

Claims (9)

[Claims] 1. A conductor paste composition in which a conductive material made of Ag or an alloy containing Ag as a main component and an inorganic binder containing a glass frit and a metal oxide are dispersed in a vehicle. The binder composition is at least one selected from PbO and / or ZnO: 20 to 40% by weight, B2O3: 6 to 20% by weight, SiO2: 2 to 15% by weight, at least 1 selected from CuO and / or TiO2.
1 or more: 30 to 72% by weight, a conductor paste composition. 2. The content of the inorganic binder with respect to 100 parts by weight of the conductive material is 0.5 to 15 parts by weight.
The conductor paste composition described in 1. 3. PbO, B2O3 and SiO2 in the inorganic binder are constituents of the glass frit, and the content thereof is 0.35 to 10 parts by weight relative to 100 parts by weight of the conductive material. The conductor paste composition according to item 1. 4. The average particle size of the glass frit is 0.1.
The conductor paste composition according to any one of claims 1 to 3, having a thickness of -20 µm. 5. The CuO and / or TiO2 in the inorganic binder is a metal oxide which is not in a glass state, and the content thereof is 5 parts by weight or less with respect to 100 parts by weight of the conductive material. The conductor paste composition as described in 1. 6. The conductor paste composition according to claim 1, wherein the average particle size of the metal oxide is 0.1 to 20 μm. 7. The conductive paste composition according to claim 1, wherein the conductive material comprises Ag: 70 to 100% by weight, at least one selected from Pd and / or Pt: 0 to 30% by weight. object. 8. A circuit board having a terminal electrode or an external conductor formed by baking the conductor paste composition according to claim 1. Description: 9. The circuit board according to claim 8, wherein a plating film is provided on a surface of the terminal electrode or the outer conductor.