JPH11162253A - Conductive powder and method for producing conductive part using the powder - Google Patents

Abstract

(57) Abstract: Provided is a method for manufacturing a conductive part using a conductive powder excellent in solder wettability and solder heat resistance and a conductive powder capable of reducing the number of steps. SOLUTION: The conductive powder has a Pd content of 20% by weight or less with respect to Ag, and both are alloyed. AgPd
The particle size of the alloy powder is set to 5 μm or less. The conductive powder is of a high dispersion type in which AgPd alloy powder is dispersed. Wirings and electrodes manufactured using the AgPd alloy powder have excellent solder wettability and solder heat resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Ag (silver) and Pd
The present invention relates to a conductive powder which is alloyed with (palladium) and has excellent wettability and solder heat resistance, and a method for producing a conductive portion using the powder.

[0002]

2. Description of the Related Art With the miniaturization, light weight, and personalization of electronic devices and communication devices, bare chip mounting of LSIs and surface mounting of many passive components are rapidly increasing. As a substrate which is a constituent material of the above, a substrate using a glass ceramic having a low dielectric constant suitable for a high frequency has been proposed. Then, a required wiring pattern is printed on the surface of a green sheet made of glass ceramic before firing with a conductive paste made of conductive metal powder, resin and a solvent, and is made of a conductive material by simultaneously firing. There is a technique for manufacturing a glass ceramic substrate on which wiring is manufactured.

As the metal powder of the conductive paste for forming the wiring, it is optimal to use Ag alone in terms of conductivity. However, migration (Ag of the positive electrode becomes Ag ion and moves toward the negative electrode, Ag precipitates in a dendritic manner in the insulating portion between circuits, and if this symptom progresses, the circuit may be short-circuited), which is not preferable for the densification of the wiring pattern. Therefore, migration is suppressed by mixing Pd with Ag at a required ratio.

[0004]

The metal powder in the conductive paste has been in a coprecipitated or mixed state in which Ag and Pd are separated. For this reason, due to the difference in melting point between Ag and Pd, there is a problem that distortion, cracks, and the like occur due to the difference in the coefficient of thermal expansion during firing of the conductive paste. When firing, Pd
It is pointed out that O (palladium oxide) is generated, which causes a decrease in solder wettability and solder heat resistance. If good solder wettability or solder heat resistance cannot be obtained with the wiring fabricated on the board in this way, especially on a board that requires high precision, the wiring must be plated as required before soldering. However, there is a drawback that the number of steps is increased and the material cost is increased.

[0005] Further, electrodes of electronic parts such as multilayer ceramic capacitors are also manufactured using the conductive paste. However, as described above, distortion and cracks are generated, and good solder wettability is obtained. And the soldering heat resistance was not obtained, and complicated work such as pre-plating the electrodes was required.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks inherent in the prior art, and has been proposed to solve the problem in a favorable manner. It is an object of the present invention to provide a method for manufacturing a conductive part using conductive powder and a conductive powder capable of reducing the number of steps.

[0007]

Means for Solving the Problems In order to overcome the above-mentioned problems and appropriately achieve the intended purpose, the conductive powder according to the present invention has a Pd content of 20% by weight or less based on Ag, and the two are alloyed. And a high dispersion type having a particle size of 5 μm or less.

In order to overcome the above-mentioned problems and achieve the intended object, a method for producing a conductive part using a conductive powder according to another invention of the present application uses a method in which the content of Pd with respect to Ag is 20% by weight or less. Is alloyed, and a resin and a solvent are mixed in a required ratio to a high dispersion type conductive powder having a particle size of 5 μm or less to form a conductive paste. A required pattern is printed on the surface of the green sheet, and the green sheet printed with the conductive paste is fired at a required temperature, so that a wiring made of the conductive powder is produced on a glass ceramic substrate. And

In order to overcome the above-mentioned problems and achieve the intended object, a method for producing a conductive part using a conductive powder according to still another invention of the present application has a Pd content of 20 w
% Or less are alloyed, and a resin and a solvent are mixed in a required ratio to a high dispersion type conductive powder having a particle size of 5 μm or less to form a conductive paste, and the conductive paste is used as an electrode of an electronic component. By applying the conductive paste applied to the electronic component and firing the conductive paste applied to the electronic component at a required temperature,
An electrode made of the conductive powder is formed on the electronic component.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a conductive powder according to the present invention and a method of manufacturing a conductive portion using the powder will be described below with reference to the accompanying drawings. In the present invention, as a conductive powder for producing wirings (conductive portions) on a substrate and electrodes (conductive portions) of electronic components, the content of Pd relative to Ag is 20%.
The content of the findings is that the alloy is formed into an alloy at w% or less, and the use of a highly dispersed AgPd alloy powder having a particle size of 5 μm or less provides excellent solder wettability and solder heat resistance in the conductive portion. The appropriate values such as the Pd content and the particle size with respect to Ag were found by the following tests conducted under various conditions.

First, the manufacture of a glass ceramic substrate and an alumina substrate on which wirings are manufactured under various conditions will be described. That is, AgPd alloy powder, a mixture of Ag powder and Pd powder (hereinafter referred to as “mixed powder”) and A
g-Pd coprecipitated powder, each powder and resin (ethyl cellulose), solvent (α-terpineol) and inorganic oxide
(Bismuth oxide, copper oxide, etc.) are kneaded to form a conductive paste (see FIG. 1). By the way, the compounding ratio of the conductive paste is as follows: each powder: 60 to 80 wt%, resin: 3 to 10 wt%
%, Solvent: 10 to 20 wt%, inorganic oxide: 1 to 5 wt%
%. With this conductive paste, glass ceramics (SiO ₂ : 35 wt%, Al ₂ O ₃ : 23 wt%, Ca
A required wiring pattern is printed on the surface of the green sheet before firing by using a material of O: 20 wt% and MgO: 22 wt%) by a screen printing method. Then, the printed green sheet was fired in a box furnace at 950 ° C. for 120 minutes to produce a glass-ceramic substrate on which wiring made of conductive powder was formed.

A wiring pattern is printed on a previously fired alumina substrate with a conductive paste in the same manner as described above, and the wiring pattern is fired in a box furnace at 950 ° C. × 10 minutes to obtain a conductive powder. An alumina substrate on which a wiring made of was prepared was manufactured.

[0013]

Test Example 1 First, using the alumina substrate, a test was conducted on the influence of the form and shape of the powder.

For the metal powder of the conductive paste, Ag
SEM (scanning type) of a wiring prepared on an alumina substrate with the conductive paste of Examples and Comparative Examples 1 to 4 using a powder whose Pd content was set to 10 wt% with respect to Fig. 2 (electron microscope)
Shown in Example: Ag and Pd are alloyed,
High dispersion type whose particle diameter is set to 3 μm Comparative example: Ag and Pd are co-precipitated, and high dispersion type whose particle diameter is set to 3 μm Comparative example: Ag and Pd are alloyed That
Aggregation type whose particle diameter is set to 1 μm Comparative example: Ag and Pd are in a co-precipitated state, and aggregation type whose particle diameter is set to 1 μm Comparative example: Ag and Pd are in a mixed state , Agglomerated type whose particle size is set to 0.8 μm

That is, as is apparent from FIG. 2, when comparing the embodiment and the comparative example, which are the same alloy powder, it was observed that the high dispersion type example was more dense than the agglomeration type comparative example. In addition, when comparing the same high dispersion type Examples and Comparative Examples, no remarkable difference was observed between the Examples in terms of crystal size and compactness. However, in the comparative example which was a coprecipitated powder, cracks were observed in the wiring depending on the firing lot. This is considered to be due to the difference in thermal expansion behavior between the alloy powder and the coprecipitated powder. Note that the comparative example has a larger crystal size than the example and is inferior in denseness.

When comparing the embodiment with the comparative example,
It was observed that the example which was an alloy powder was denser than the comparative example which was a mixed powder. As for the mixed powder, a composition of Ag + Ag 20 wt% Pd was also considered as a comparative example. As a result, as the content of Pd, which is one of the materials constituting the mixed powder, increases, the denseness deteriorates. Was observed. That is, it is considered that the denseness of the wiring is affected by the difference in melting point between the two kinds of powders to be mixed, and it was confirmed that the smaller the difference in melting point, the denser the wiring was formed.

[0017]

Test Example 2 With respect to the above Examples and Comparative Examples, tests were conducted on the solder wettability and solder heat resistance (corrosion) using the alumina substrate. In addition,
Solder wettability and solder heat resistance test is 62% Sn3
For solder wettability, 6% Pb 2% Ag solder solution was used. For solder wettability, the alumina substrate was dipped in a 230 ° C. solder solution for 3 seconds, and evaluated by the ratio (area of solder / area of wiring) at that time. As to the properties, the alumina substrate was dipped in a solder liquid at 230 ° C. for 60 seconds, and the result of evaluation at the ratio (area of solder / area of wiring) at that time is shown in Table 1. At this time, the thickness of the wiring was 1.5 × 1.5 mm.

[0018]

That is, Table 1 shows that AgP having a particle size of 3 μm was obtained in both solder wettability and solder heat resistance.
The d alloy powder (high dispersion type) was found to be the most excellent. However, regarding the particle size of the AgPd alloy powder, 3 μm
m is optimal, but if it is 5 μm or less, it is industrially practical.

[0020]

Test Example 3 Next, using the above-mentioned glass ceramic substrate, a test was conducted on the effect of the Pd content in the powder limited to the AgPd alloy powder having a particle size of 3 μm.

Regarding the metal powder of the conductive paste, A
The content of Pd is 30 wt%, 20 wt%, 10 g
FIG. 3 shows an SEM photograph of the wiring fabricated on the glass ceramic substrate in Examples 1 to 5 in which the weight was changed to 5% by weight.

That is, as can be seen from FIG. 3, it was observed that the lower the Pd content in the alloy powder, the larger the crystal size and the more dense the wiring. When the Pd content in the alloy powder is 30 wt%, the interface between adjacent crystals is not clearly observed. Further, as a result of measuring the resistance value of the wiring in each of Examples 1 to 3, as the Pd content in the alloy powder increases, the resistance value of the wiring increases. In addition,
When the X-ray diffraction of the wiring is performed, a PdO diffraction line is observed when the Pd content in the alloy powder is more than 20% by weight, and when the Pd content in the alloy powder is 20% or less, PdO is
Was not detected.

[0023]

Test Example 4 In each of Examples 1 to 3, tests for solder wettability and solder heat resistance were performed under the same conditions as in Test Example 2 described above, and the results are shown in Table 2. The results of measuring the conductivity of each example are also shown.

[0024]

That is, in a glass ceramic substrate,
When the content of Pd in the alloy powder is more than 20 wt%, the solder wettability sharply decreases. This is considered to be due to the following two causes overlapping. (1) The lower the Pd content in the AgPd alloy powder, the lower the melting point. Therefore, the powder is sintered densely and the contact area between the solder and the wiring is reduced, so that the solder is hardly eroded. (2) When the Pd content in the alloy powder is> 20 wt%, PdO starts to be present on the surface of the thick film, so that the solder is hardly wet on the wiring and the contact area between the solder and the wiring is reduced, so that the apparent solder is formed. Hard to eat. The solder heat resistance decreases when the Pd content in the alloy powder is close to 20 wt%, but since the solder wettability at this point is sufficiently excellent, it can be implemented industrially without any problem.

From the results of the above-described tests, Ag and Pd were alloyed, and the particle size was 5 μm or less.
It has been clarified that by using an AgPd alloy powder in which d is set to 20 wt% or less, solder wettability and solder heat resistance can be improved without generating distortion, cracks, and the like in the wiring. Therefore, it is not necessary to pre-plate the wiring on a substrate that requires accuracy, and the number of steps and material cost can be reduced.

The AgPd alloy powder of the embodiment can be used as an electrode of an electronic component, for example, a multilayer ceramic capacitor. Also in this case, as shown in FIG. 4, a conductive paste containing the AgPd alloy powder set under the above-mentioned conditions is applied to a portion to be an electrode of the multilayer ceramic capacitor, and the paste is fired at a required temperature to obtain the laminate. An electrode made of the conductive powder is formed on a ceramic capacitor. Since this electrode is excellent in solder wettability and solder heat resistance, even when precision is required, the electrode can be reliably soldered without plating. Further, the electronic component is not limited to the multilayer ceramic capacitor, and AgPd alloy powder can be adopted as an electrode material of various components.

[0028]

As described above, according to the conductive powder according to the present invention and the method of manufacturing a conductive part using the powder, the conductive powder is formed by alloying Ag and Pd and reducing the Pd content. Since the content is set to 20 wt% or less, PdO is not easily generated when the conductive paste is baked to produce wiring of a glass ceramic substrate or an electrode of an electronic component, and it is possible to suppress the occurrence of distortion, cracking, and the like. In addition, conductive parts such as wiring and electrodes made of conductive powder are excellent in solder wettability and solder heat resistance, so conductive parts such as wiring and electrodes should be plated in advance to improve solder adhesion. Therefore, good soldering can be achieved, and the number of steps can be reduced to reduce running costs. Further, since the wiring can be formed densely, the wiring pattern can be suitably densified.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a process for producing a wiring on a glass ceramic substrate.

FIG. 2 is an explanatory diagram showing an SEM photograph of a wiring on an alumina substrate.

FIG. 3 is an explanatory view showing an SEM photograph of a wiring on a glass ceramic substrate.

FIG. 4 is a process chart showing a process for producing an electrode on the multilayer ceramic capacitor.

Claims (3)

[Claims] 1. A conductive powder characterized in that both are alloyed when the content of Pd with respect to Ag is 20% by weight or less and the particle size is 5 μm or less. 2. A resin and a solvent are mixed at a required ratio with a highly dispersed conductive powder having a Pd content of 20% by weight or less with respect to Ag and a particle size of 5 μm or less. A paste is prepared, a required pattern is printed on the surface of a green sheet before firing using glass ceramic as a material by the conductive paste, and the green sheet printed with the conductive paste is fired at a required temperature, thereby forming a glass ceramic substrate. A method of manufacturing a conductive part using a conductive powder, wherein a wiring made of the conductive powder is manufactured. 3. A resin and a solvent are mixed at a required ratio with a highly dispersed conductive powder having a Pd content of 20% by weight or less with respect to Ag and a particle size of 5 μm or less. A paste is prepared, the conductive paste is applied to a portion to be an electrode of an electronic component, and the conductive paste applied to the electronic component is fired at a required temperature, so that the electrode made of the conductive powder is applied to the electronic component. A method for manufacturing a conductive part using a conductive powder, wherein the conductive part is manufactured.