JP3369633B2 - Conductive paste and ceramic multilayer wiring board using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor paste and a ceramic multilayer wiring board using the conductor paste, mainly 950
The present invention relates to a conductor paste used for a ceramic multilayer wiring board which is fired at a low temperature of ℃ or less and a multilayer wiring board using the same.

[0002]

2. Description of the Related Art As a wiring board used in electronic equipment, a ceramic multilayer board has come to be used due to demands for higher speed and higher density. Vias are formed in such a multilayer substrate to establish conduction between the layers. The via is generally formed by forming a through hole in a ceramic green sheet, filling a conductive material, laminating and firing.

Alumina is mainly used for the ceramic multilayer wiring board. A high melting point wiring material such as tungsten is used for the alumina substrate. However, in recent years, a substrate which can be fired at a low temperature using copper, silver, or gold as a conductor has been developed and is being used in response to the demand for higher speed and higher density. Copper, a silver-based conductor, gold, etc. are used as the internal conductor of this low-temperature fired multilayer ceramic substrate, while copper, silver-palladium, silver-platinum, and the like are used as its surface conductor.
Gold or the like is used.

[0004]

By the way, in a low temperature fired multi-layer ceramic substrate, when silver is used inside and a conductor of silver-palladium is used on the surface, silver is formed on either the internal wiring and the via or the via and the surface. It is necessary to connect silver-palladium.

In this connection portion, there was a problem that voids were generated in silver due to the difference in diffusion rate of atoms of silver and palladium. Therefore, it is difficult to obtain a highly reliable connection, and there is a problem that the connection state is deteriorated particularly when the surface conductor is baked and then the resistance or the gold conductor is baked.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems, and an object of the present invention is to provide a conductor paste capable of highly reliable conductor connection and a ceramic multilayer wiring board using the same. .

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a conductor paste for vias, in which a specific amount of Pd, Au and / or Pt is added to Ag.
It is characterized in that a paste containing an appropriate amount of crystallized glass and an organic vehicle necessary for forming a paste is used. As a result, in the ceramic multilayer wiring board formed by connecting the Ag internal wiring and the Ag-Pd surface conductor, the connection between the via and the surface conductor can be ensured, and the internal wiring conductor and The connection of the conductors does not deteriorate, and as a result, it is possible to connect the conductors with high reliability.

That is, the present invention provides "93 to 97 parts by weight of Ag powder.
End, Pd powder 0.5-2 parts by weight, the remaining ingredients Au powder and /
Or Pt powder (however, Au powder is 0-5 parts by weight, Pt powder is 0
It consists to 3 parts by weight), One or, Pd powder, Au powder and Pt powder
A total of 3 to 7 parts by weight of powder, and 0.3 to 3 parts by weight (outer percentage) of crystallized glass and an appropriate amount of organic vehicle, a conductor paste. Is the gist, and also
In the ceramic multilayer wiring substrate formed by connecting the surface conductors of the internal wiring and Ag-Pd of "Ag, the conductor pair - the strike,
A ceramic multilayer wiring board characterized by being used for a via connecting the Ag internal wiring and a surface conductor of Ag-Pd. Is the gist.

[0009]

According to the conductor paste for vias according to the present invention described above, by adding Pd in addition to Ag and further Au and / or Pt as the conductor for vias, the surface Ag-Pd
The effect of reducing the difference in the moving speed of the metal atom at the portion where the conductor and the via conductor contact each other occurs. Therefore, the difference between the amount of diffusion of metal atoms from the surface conductor toward the via conductor and the amount of diffusion in the opposite direction can be reduced, and voids generated around the via conductor can be eliminated, and the connection between the via and the surface conductor can be eliminated. It can be assured.

In addition, if this via conductor is used, the connection with the internal conductor is not deteriorated, so that it is possible to connect the conductor with high reliability. Further, according to the above-mentioned conductor paste of the present invention, the addition of the crystallized glass does not cause adhesion to the setter and does not cause cracks.

The present invention will be described in detail below. Surface Ag
-Pd conductors with a Pd ratio of 10 to 20 wt% are usually used. If it is less than 10 wt%, the probability of electromigration occurring is high, while on the other hand, 20 wt%
This is because not only is the cost higher, but the sheet resistance also increases.

In the present invention, the via conductor in contact with the surface conductor made of Ag-Pd has Ag as a main component and Pd of 0.5 or less.
~ 2 wt% must be included, and the total of Pd, Au and Pt must be 3 to 7 wt%. Pd is effective for improving the connection with the Ag-Pd conductor on the surface, so it must be contained in an amount of 0.5 wt% or more. But 2wt
%, The connection with the Ag conductor inside becomes poor, so it is desirable that the amount be in the range of 0.5 to 2 wt%.

The addition of Au and / or Pt can also improve the connection with the surface Ag-Pd conductor. When Au and / or Pt is added in addition to Pd, the connection with the surface can be improved without making the connection with the Ag conductor inside much worse, so either or both of Au and Pt can be added to 1 wt. % Or more is preferably added. P
If the sum of d, Au, and Pt is less than 3 wt%, the connection with Ag-Pd on the surface will be bad, and conversely, if the total of these exceeds 7 wt%, the connection with the internal Ag conductor will be bad. Therefore, it is not preferable. Further, unless Au and Pt are 5 wt% or less and 3 wt% or less, respectively, the connection of the internal wiring with the Ag conductor is deteriorated, which is not preferable.

In the present invention, the glass is preferably one that crystallizes. This is because there is no softening due to re-baking and the adhesion to the substrate is excellent, and it is difficult to adhere to a setter such as alumina during baking. Any crystallized glass can be used as long as it has a composition capable of precipitating crystals by firing at 850 ° C.
For example, SiO ₂ 33%, Al ₂ O ₃ 18%, B ₂ O ₃ 2
%, ZnO 17%, CaO 17%, and TiO ₂ 13% (glass having a composition that precipitates crystals by firing at 850 ° C.).

If the amount of the crystallized glass is less than 0.3 wt%, it may adhere to the setter used for firing such as alumina, and the adhesion between the via conductor and the substrate is not good, so that voids are generated. Is not preferable. Conversely, 3%
If the amount exceeds 0.1, cracks may occur in the substrate around the via conductor, so in the present invention, it is preferable to use 0.3 to 3 parts by weight (outer ratio) of crystallized glass.

In the present invention, among the raw materials used as the metal component, it is preferable to use spherical Ag powder as the Ag powder. This is because the spherical Ag powder has a small oil absorption amount and is easily formed into a paste, and the solid content and the viscosity are easily adjusted. The particle size of such spherical Ag powder is preferably 0.5 to 2 μm.

Further, in the present invention, as the Pd powder,
It is also spherical, and its particle diameter is preferably 0.2 to 1 μm. On the other hand, Au powder having a particle size of 0.2 to 1.5 μm is suitable, and Pt powder having a particle size of 0.1 to 1.5 μm is suitable.

With respect to the organic vehicle, as long as it can be formed into a paste and has viscosity characteristics such that it can be filled,
Either can be used. For example, ethyl cellulose, methacrylate resin and the like having a high boiling point solvent (e.g., terpineol, butylcarbinol, dibutylphthalate, etc.) dissolved in 10 to 20% can be mentioned. .

The amount of organic vehicle is preferably in the range of 10 to 20% with respect to the metal component. Furthermore, in the present invention, it is also effective to add a dispersant, a viscosity modifier, etc., if necessary, and this is also included in the present invention.

The conductor paste of the present invention can be used as a via conductor for connecting Ag-Pd conductors on the surface and Ag, when Ag is used for the internal wiring. Also, when Ag-Pd conductor and Ag conductor are used together as internal wiring, it can be used as a connecting via.

[0021]

EXAMPLES Examples of the present invention will be given below together with comparative examples.
The present invention will be described in more detail.

(Examples 1 to 7) (1) Raw materials In Examples 1 to 7, the following raw materials were used. -Silver (Ag) powder: A powder made by Mitsui Mining & Smelting Co., Ltd. having a particle size of about 1 μm and a nearly spherical shape.・ Palladium (Pd) powder: Particle size of about 0.5 manufactured by Sumitomo Metal Mining Co., Ltd.
μm powder. -Gold (Au) powder: A powder made by Tanaka Kikinzoku International Co., Ltd. with a particle size of about 1 μm. -Platinum (Pt) powder: A powder made by Tanaka Kikinzoku Kogyo Co., Ltd. with a particle size of about 1 μm. Crystallized glass: SiO ₂ 33%, Al ₂ O ₃ 18%, B ₂ O ₃ 2%, Z
Glass composed of 17% nO, 17% CaO, and 13% TiO ₂ (8
Glass having a composition in which crystals are precipitated by firing at 50 ° C). -Organic vehicle: An organic vehicle prepared by dissolving ethyl cellulose in 15% dibutyl phthalate.

(2) Preparation of conductor paste The above-mentioned silver (Ag) powder, palladium (Pd) powder, gold (Au) powder, platinum (Pt) powder, and crystallized glass are shown in Table 1 in proportions (parts by weight). ), And an appropriate amount of organic vehicle, and then kneaded with a three-roll mill to prepare a conductor paste.

(3) Production of multilayer ceramic substrate Alumina powder: 50% by weight and zinc borosilicate glass: 50% by weight are mixed, and an acrylic resin is added as an organic binder to form a slurry, and the slurry is prepared. Molded into a sheet (thickness: about 0.2 mm) by the doctor blade method,
A ceramic green sheet was obtained.

This green sheet was punched with a 0.15 mm via hole by NC punching. Next, this hole was filled with the conductor paste for vias described in (2) by printing, and an internal wiring pattern was further printed on this.
After thermocompression bonding, the binder was removed at 400 ° C. and baked at 850 ° C. to obtain a multilayer ceramic substrate. Silver-palladium (Pd ratio 20%) paste was printed on the obtained substrate and baked at 850 ° C.
Furthermore, this substrate was re-fired three times at 850 ° C. assuming firing of resistors and gold conductors.

(4) Evaluation To evaluate the continuity, a pattern substrate as shown in FIG. 1 was prepared and the continuity was examined by a tester. 96 conduction points (measurement points) were provided on each of the front and back sides of this substrate, 50 substrates were prepared for each example, and a total of 9600 conduction points were investigated. The results are shown in Table 1.

FIG. 1 is a schematic cross-sectional view of a substrate for evaluating continuity, where 1 is a ceramic layer, 2 is a via, 3 is an internal wiring, and 4 is a surface conductor. The above-mentioned investigation of the continuity is conducted by examining the continuity between the terminal A and the terminal B (front) and between the terminal C and the terminal D (back) in FIG.

(Comparative Examples 1 to 6) For comparison, the same raw materials as those in Examples were used, and conductor pastes having the proportions (parts by weight) shown in Table 1 were prepared in the same manner as in Examples. The obtained conductor paste was evaluated in the same manner as in the example. The results are shown in Table 1. In Comparative Examples 1, 2, and 4, as a result of cross-sectional observation, cavities were observed near the connection between the surface conductor and the via, and in Comparative Example 3, cavities were observed at the connection between the internal wiring and the via.

[0029]

[Table 1]

Regarding the presence or absence of Pd blending, as is clear from Table 1, by blending Pd in Examples 1 to 7, the connectivity with the Ag-Pd conductor on the surface was improved and there was no conduction failure. It was On the other hand, Comparative Example 1 containing no Pd
(Ag: 100 parts by weight of paste), there were 15 conduction failure points. Regarding the amount of Pd compounded, as seen in Comparative Example 3 (Pd amount: 3 parts by weight), it was observed that when the amount of Pd was large, the connection with the internal wiring was adversely affected. In the invention, as in Examples 1 to 7, Pd amount: 0.5 to 2 wt
% Is preferable.

Moreover, as is clear from comparison with Comparative Example 2, in the present invention, the amount of Pd is set to 0.5 to 2 wt%, and the addition of Au and / or Pt further deteriorates the connection with the internal wiring. It was confirmed that the effect of improving the connection with the surface conductor was obtained without doing so. However, when Au exceeds 5 wt%, as is clear from the comparison between Example 6 and Comparative Example 5, it was recognized that the connectivity with the internal wiring also deteriorates. Also,
When Pt exceeds 3 wt%, it was confirmed that the connection with the internal wiring also deteriorates, as is clear from the comparison between Example 7 and Comparative Example 6.

(Embodiments 8 and 9) In order to investigate whether or not there was adhesion to a setter and the occurrence of cracks, conductor pastes having the compounding ratios shown in Table 2 were prepared. (The raw materials used were the same as above.) Compared with the one using this conductor paste, (1) As for the presence or absence of adhesion to the setter, the alumina setter
Was observed with a stereomicroscope. (2) For the presence or absence of cracks, the sample was embedded in epoxy resin, polished so that the cross section could be seen, and observed with a microscope. Table 2 shows the observation results of (1) and (2).

(Comparative Examples 7 and 8) For comparison, crystallized glass was not added (Comparative Example 7) and 5 parts by weight was added (Comparative Example 8).
The conductor paste of Example 1 was prepared in the same manner as in Examples 8 and 9. The above (1) and (2) were observed for the one using this conductor paste. The observation results are shown in Table 2.

[0034]

[Table 2]

As is clear from Table 2, in Comparative Example 7 in which crystallized glass was not added, cracks did not occur, but
Adhesion to the setter was recognized. Further, in Comparative Example 8 in which 5 parts by weight of this crystallized glass was blended, conversely, although adhesion to the setter was not observed, cracks occurred. On the other hand, as seen in Examples 8 and 9, when the compounding amount of the crystallized glass was 0.3 to 3 wt%, neither adhesion to the setter nor crack generation was observed.

[0036]

As described above, the conductor sheet according to the present invention is used.
By using the strike as the conductor paste for vias, the effect that the Ag conductor (internal wiring) and the Ag-Pd conductor (surface conductor) can be well connected is produced. Therefore, it is possible to provide a ceramic multilayer substrate which uses a low-resistance Ag conductor for the internal wiring and has excellent connection reliability. Also,
According to the conductor paste of the present invention, the addition of the crystallized glass does not cause adhesion to the setter, and further, the effect that the substrate around the via conductor is not cracked.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a substrate for evaluating continuity.

[Explanation of symbols]

1 Ceramic layer 2 via 3 Internal wiring 4 surface conductor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H05K 3/46 H05K 3/46 S (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 1/00-1 / 24 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. 93 to 97 parts by weight of Ag powder , 0.5 to 2 parts by weight of
Pd powder , the remaining components are Au powder and / or Pt powder (however, Au powder is 0 to 5 parts by weight, Pt powder is 0 to 3 parts by weight), and the total of Pd powder, Au powder and Pt powder Has 3 to 7 weight
Parts, further comprising 0.3 to 3 parts by weight (outer ratio) of crystallized glass and an appropriate amount of organic vehicle. 2. In a ceramic multilayer wiring board formed by connecting internal wiring of Ag and surface conductor of Ag-Pd, 93 to 97 parts by weight of Ag powder , 0.5 to 2 parts by weight of Pd powder , and the remaining components are Au
Powder and / or Pt powder (however, Au powder is 0 to 5 parts by weight,
Pt powder is 0 to 3 parts by weight), and Pd powder and Au powder.
The total amount of Pt powder is 3 to 7 parts by weight, and a conductor paste composed of 0.3 to 3 parts by weight (outer percentage) of crystallized glass and an appropriate amount of organic vehicle is used for the internal wiring of Ag and Ag-Pd. A ceramic multilayer wiring board characterized by being used for a via connecting to a surface conductor of.