JP3150932B2 - Conductive paste for ceramic multilayer circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste for a ceramic multilayer circuit board, and more particularly, to a conductive paste capable of providing a multilayer circuit board with less warpage even when fired simultaneously with a ceramic green sheet.

[0002]

2. Description of the Related Art Conventionally, an alumina multilayer circuit board has been mainly used as a ceramic multilayer circuit board. In order to manufacture an alumina multilayer circuit board, a high temperature of 1500 ° C. or more is required for sintering alumina, and a Mo-Mn or W-based high-temperature sintering material is used as a conductor material to withstand the temperature. Was used.

On the other hand, recently, a low-temperature fired substrate that can be fired at a lower temperature than alumina has been gradually used. In this low-temperature fired substrate, sintering can be performed at a firing temperature of 800 to 1000 ° C., so that the conductor material is also Mo-
Ag and Cu having lower resistance than Mn and W can be used, and application development to CSP (chip size package) as a high-density mounting board or MCM (multi-chip module) is being started.

[0004] A low-temperature fired substrate is generally a mixture of a glass frit component and a ceramic component, and is sintered at a low temperature using a low melting point of the glass frit to form a substrate.

A method of manufacturing such a ceramic multilayer circuit board is to print a conductive paste on a green sheet serving as a ceramic substrate, and to form a via hole in a ceramic green sheet to make electrical connection between ceramic layers. This is a method in which a conductive paste is filled, a plurality of green sheets are stacked, and then fired at once.

[0006]

However, the ceramic multilayer circuit board manufactured in this manner has a problem that the board is warped after firing. This is a phenomenon that occurs because ceramic green sheets, which are materials having different shrinkage rates during firing, and a conductive paste are simultaneously fired. If warpage occurs, it cannot be used as a substrate.

This warping phenomenon is caused by the fact that shrinkage of the conductive paste occurs earlier than shrinkage of the ceramic green sheet.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to form a ceramic circuit capable of forming a conductor circuit with very little warpage even when fired simultaneously with a ceramic green sheet. An object of the present invention is to provide a conductive paste for a multilayer circuit board.

[0009]

Means for Solving the Problems To achieve the above object, the present invention relates to a method for producing a powder having an average particle diameter of 3 produced by an atomizing method.
By forming a multilayer circuit board using a conductive paste containing a conductive powder whose main component is 50% by weight or more of an Ag powder having a maximum particle size of 40 μm or less and having a maximum particle size of 40 μm or less, a ceramic green sheet and Even after firing, a conductor circuit with very little warpage can be formed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a conductive paste which is printed on ceramic green sheets when a ceramic multilayer circuit board is manufactured by stacking and firing a plurality of ceramic green sheets. The first invention is a conductive paste for a ceramic multilayer circuit board having a manufactured average particle diameter of 3 to 10 μm and a maximum particle diameter of 40 μm or less, and the Ag powder as a conductive powder, in the first invention, As the conductive powder other than the Ag powder, a powder of one or more metals selected from Pd, Pt, Au, Ni or Cu is used in combination, and the Ag powder is 50% by weight or more of the conductive powder. The conductive paste for a ceramic multilayer circuit board described above is a second invention.

By using the Ag powder having a specific particle size produced by the atomizing method as described above, the shrinkage ratio of the Ag powder can be adapted to the shrinkage ratio of the ceramic green sheet. A circuit board can be manufactured.

The Ag powder generally used for the conductive paste is produced by a chemical reduction method, and has an average particle size of 0.1.
1-2 μm is common. However, when these powders are used for the purpose of the present invention, the sintering of the Ag powder proceeds much faster than the sintering of the ceramic green sheet, so that the occurrence of warpage cannot be suppressed.

As described in JP-A-3-284896, an Ag powder produced by a usual chemical reduction method and calcined to increase the average particle size is also used in the present invention. Is effective, but the calcined Ag powder has a form in which the original particles are gathered, and the calcined particles have many cavities. Therefore, the sintering of the calcined particles proceeds faster than that of the non-hollow particles having the same particle diameter. Therefore, Ag powder having a large particle size obtained by calcining after chemical reduction is not suitable for the use of the present invention.

The atomization method referred to in the present invention is a method in which Ag is melted at a high temperature, and the Ag liquid is sprayed from a nozzle at a high speed to form spherical fine powder. When a gas is used as a medium for spraying an Ag liquid from a nozzle at a high speed, a gas atomization method is used, or when water is used, a water atomization method is called. However, atomized powder that can be used in the present invention is either method. Can also be obtained by

The reason why the average particle size of the atomized Ag powder of the present invention is specified to be 3 to 10 μm is that the particle size is 3 to 10 μm.
If the particle size is smaller than μm, it is difficult to eliminate the warpage when firing simultaneously with the ceramic green sheet.
This is because, although the warpage of the g powder is reduced, the Ag powder is crushed into a foil when the Ag powder is formed into a paste, which causes clogging of the screen during printing.

Similarly, the reason why the maximum particle size of the Ag powder is set to 40 μm or less is that if an Ag powder having a size larger than 40 μm is used, the powder is crushed into a foil when it is made into a paste, and the size of the screen during printing is reduced. This is because it causes clogging.

The conductive paste of the present invention can be applied as a conductive paste for an inner layer of a ceramic green sheet, as a paste for filling a via, or as a paste for a surface layer.

In the conductive paste of the present invention, the Ag powder having an average particle size of 3 to 10 μm and a maximum particle size of 40 μm or less, which is produced by an atomizing method, may be 50% by weight or more of the conductive powder. preferable. 50 Ag powder
If the amount is less than the weight percentage, the warpage cannot be eliminated when the ceramic green sheet is fired simultaneously.

It is also possible to add a conductive powder other than Ag. For example, Pt, Pd, Au, Ni or Cu can be used in combination. Further, it is also possible to use powder of one or more of these metals and Ag powder in combination.

In addition to the conductive powder, it is also possible to add various additives, for example, inorganic compounds, glass frit, organometallic compounds and the like in a fixed amount within a range that does not deteriorate the properties as a conductive paste.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples. The details of the Ag powder used in the examples are as shown in Table 1 below.

[0022]

[Table 1]

The green sheet used was a mixture of 50 parts by weight of a glass frit mainly composed of silicon oxide, aluminum oxide and boron oxide and 50 parts by weight of aluminum oxide. Green sheet thickness is 200
μm.

On the other hand, the conductive paste having the composition shown in Table 2 below was preliminarily kneaded with a planetary mixer and then kneaded with three rolls.

Then, a conductive paste having each composition shown in Table 2 is screen-printed on a green sheet in a size of 10 mm □, five of them are stacked and hot-pressed, and then fired at a maximum temperature of 900 ° C. for 1 hour. Thus, a multilayer circuit board was produced, and the warpage of the board was measured.

In the measurement of the warpage, the amount of warpage of the entire substrate is obtained using a warp gauge, and the value obtained by subtracting the thickness of the substrate from the amount of warpage is defined as the amount of warpage. The warpage shown in Table 2 is preferably 20 μm or less.

[0027]

[Table 2]

The following points are clear from Table 2. (1) Since Examples 1 and 2 are Ag powders having an average particle size of 3 to 10 μm manufactured by the atomizing method of the present invention, the warpage of the substrate is good.

(2) In Examples 3 and 4, Pt powder or Pd powder and glass powder were further added to Ag powder having an average particle diameter of 3.6 μm produced by the atomizing method, but both of them had a small amount of warpage. Good.

(3) However, Ag having an average particle size of 2.7 μm
Comparative Example 1 using powder has a large amount of warpage.

(4) In Comparative Example 2, since the average particle size of the Ag powder was too large, 10.5 μm, clogging of the screen plate occurred during screen printing after the paste was produced, so that the paste was excellent. I could not print.

(5) In Comparative Example 3, since the average particle size of the Ag powder is too small at 1.6 μm, the amount of warpage is very large.

(6) Further, A having an average particle size of 1.6 μm
In Comparative Examples 4 and 5, in which the average particle size was increased by calcining the g powder, the amount of warpage was improved as compared with Comparative Example 3, but it was still not at a satisfactory level.

The above results show that the green sheet material used was a glass frit component containing silicon oxide, aluminum oxide, and boron oxide as main components and aluminum oxide as a ceramic component. The present invention is also applicable to a glass ceramic green sheet for a low-temperature fired substrate fired at ℃.

[0035]

According to the present invention, it is possible to provide a conductive paste for a ceramic multilayer circuit board capable of forming a conductive circuit having very little warpage even when fired simultaneously with the ceramic green sheet.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Ogura 19-19 Nishi-Shichijo Higashikubocho, Shimogyo-ku, Kyoto-shi, Kyoto (56) References JP-A-6-349315 (JP, A) JP-A-57-70243 ( JP, A) JP-A-5-114328 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 1/09 H01B 1/16

Claims (2)

(57) [Claims] 1. A laminate of a plurality of ceramic green sheets
And firing to produce a ceramic multilayer circuit board.
Printing on ceramic green sheets when manufacturing
A conductive paste having an average particle size of 3 to 10 μm manufactured by an atomizing method and a maximum particle size of 40 μm.
The following conductive paste for a multilayer ceramic circuit board using Ag powder as conductive powder . 2. The conductive powder other than Ag powder is P
d, Pt, Au, Ni or Cu, in combination with one or more metal powders , wherein the Ag powder is a conductive powder
2. The conductive paste for a ceramic multilayer circuit board according to claim 1 , wherein the content is 50% by weight or more .