JPH06139814A - Conductive paste - Google Patents

Abstract

(57) [Abstract] [Purpose] A glass ceramic substrate using copper as a wiring material is required for a ceramic multilayer wiring board for an electronic computer on which a large number of LSIs are mounted in order to shorten a signal delay time between the LSIs. It is an object to provide a conductor paste suitable for this substrate. [Constitution] Copper paste has been used as a thick film paste for a long time, but it was found to be unsuitable for use in multi-layer wiring. As a countermeasure against drying shrinkage, flow characteristics, and thermal stress, gelling agent, crystal Cellulose or Zn, Mo
A powder-added conductor paste was produced. [Effect] The yield of printing and board production is improved, and the glass-ceramic multilayer wiring board can be put to practical use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductor paste used for producing a ceramic multilayer wiring board using a green sheet.

[0002]

2. Description of the Related Art Conventional ceramic multilayer wiring boards are mainly made of alumina or mullite.
A glass-ceramic multilayer wiring board made of glass is suitable for satisfying the requirements for increasing the size of I and reducing the signal propagation delay between LSIs, and its practical use has been announced.
The reason is that low thermal expansion and low dielectric constant are possible,
Furthermore, since it can be sintered at a temperature of about 600 to 950 ° C,
That is, copper having a low electric resistance can be used as a wiring material. This paste using copper has been used for a long time in a dry process thick film substrate for wiring on a sintered alumina substrate. However, it cannot be used as it is for a hot multi-layer wiring board that is manufactured by wiring and stacking on a green ceramic sheet that is not sintered. Japanese Patent Publication No. 3-3416 and Japanese Patent Publication No. 4-20280 have been reported as a copper paste used for this warm type multilayer wiring board. In these, up to 15 wt% of copper oxide is mixed with copper powder. 50% by weight of an inorganic binder having a softening point of 300 to 700 ° C
Compound or add silver. See also 4-2028
In No. 0, borosilicate glass having the same composition and components as the green sheet and alumina were added to the copper paste.
However, with such a paste, the diameter of 0.05-
When the screen printing method is used to fill a 0.1 mm through hole, if the paste has a low viscosity, it may be filled during or after filling.
The solvent is absorbed by the green sheet (1) to form a recess. Further, when the viscosity of the paste is high, as shown in FIG. 2, the paste (3) does not flow in the middle of the through hole (2) and is not filled as it is. In either case, it may cause electrical connection failure and a multilayer wiring board cannot be manufactured. Further, when the amount of the metal powder is small, a gap is generated in the through hole portion or the ceramic near the through hole is cracked due to the difference in sintering shrinkage with the ceramic. Conversely, when the amount of metal powder is large and when an inorganic sintering additive is added, the difference in thermal expansion causes cracks in the vicinity of the through holes, and the optimum raw material mix of paste and the process margin are very narrow. The yield is bad. It is also a big problem in terms of product reliability.

[0003]

In the case of a wet multilayer wiring board, the optimum conditions for the ceramic and the conductor differ depending on the raw materials, the compounding ratio and the process conditions. Therefore, when the conductor paste shown in the patent publication method is applied, looking at the state of filling the through holes of the green sheet, as described above, the dent due to drying shrinkage, the filling failure or the sintering or the subsequent process There is a big problem that the product yield is bad such as the generation of cracks in the heat treatment process. In view of these problems, the present invention is to provide a conductor paste capable of producing a multilayer wiring board with a good yield.

[0004]

In order to achieve the above object, a conductor paste having good fluidity, small drying shrinkage, and cracking due to thermal stress is required. There are three ways to do this. First, a gelling agent is used to improve fluidity and dry shrinkage. Second, crystalline cellulose is used to improve fluidity and form closed pores with controlled size in the conductor, increasing the deformability of the conductor and reducing thermal stress. Thirdly, the deformability by adding zinc is increased. Alternatively, Mo is added to reduce the thermal expansion of the body and reduce the thermal stress.

[0005]

[Function] By using a gelling agent in the paste, thixotropy,
Improves dry shrinkage. By adding crystalline cellulose, closed pores are formed in the conductor and the proportion of pores in the conductor is controlled. Furthermore, by adding Zn and Mo powders, the through holes can be easily filled and the thermal stress can be reduced, so that the ceramic multilayer wiring board can be manufactured with high yield.

[0006]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 A ceramic multilayer wiring board was prepared by thermocompressing 30 to 60 green sheets with conductor wiring, and then 850 to 1000 ° C.
It is manufactured by sintering in an atmosphere with controlled oxygen concentration. If necessary, the surface of this substrate is polished, smoothed and flattened, and then multilayer wiring using thin films is performed. In the production of this ceramic multilayer wiring board, first, a raw material powder of glass ceramics, a binder, a dispersant, a solvent and the like are mixed by a ball mill or the like to produce a slurry. A green sheet having a thickness of 0.1 to 0.3 mm is manufactured from this slurry by the doctor blade method, and then attached to a frame used in a later step, and a through hole (needed for electrical connection between layers is formed by an NC punch or the like). A hole diameter of 0.05 to 0.15 mm) is formed. This through hole was filled with a paste containing the raw materials shown below by a screen printing method.

[0008] The Cu powder used in this paste may be either spherical or lumpy powder having a particle size of 1 to 3 μm, or may be powder surface-treated with an amine compound. As the vehicle, ethyl cellulose, nitrocellulose, acrylic resin, polyvinyl butyral resin, or the like is used as the binder, and α-terpineol, n-butyl carbitol acetate, phthalic acid (2-ethylhexyl) or 2.
2.4-Trimethyl-1.3-pentanediol monoisobutyrate or the like was used. As the crystalline cellulose, fine particles having a particle size of 1 to 25 μm were used. For mixing and dispersing these raw materials, a raikai machine or a three-roll mill was used. Next, regarding the raw material mixing ratio, when the Cu powder was 60 wt% or less, the electric resistance was high, and when it was 80 wt% or more, the viscosity of the paste was high and the through holes could not be filled. The vehicle ratio is
If it is 20 wt% or less, the viscosity of the paste is high and the filling of the through holes is insufficient, and if it is 40 wt% or more, the viscosity of the paste is low and the drying shrinkage of the filled paste is large.
Further, if the proportion of crystalline cellulose is 3 wt% or less relative to A, there is no effect in reducing the thermal stress, and if it is 20 wt% or more, the fluidity of the paste becomes poor and the filling of the through holes becomes insufficient. As described above, after filling the through-holes with the conductor paste described above, a Cu paste for wiring on the surface (a commercially available paste may be used) is printed, and then the required number of layers is 30 to 30.
Accurately align and stack 60 sheets, 50-300kg
/ Cm ² ; After thermocompression bonding at 100 to 150 ° C. for 5 to 30 minutes, sintering is performed in a sintering furnace whose oxygen concentration is controlled. In this case, calcination (binder removal), which is a general method, may be performed. The thus-sintered substrate was also used as a thick film / thin film mixed substrate for surface polishing and multilayer wiring by the thin film method. In the substrate manufactured in this manner, as shown in FIG. 1, since the crystalline cellulose (4) is uniformly dispersed in the paste filled in the through holes (2), uniform closed pores are formed after sintering. . Therefore, cracks do not occur in the ceramics near the conductor due to thermal stress.

Example 2 For the compounding ratio A of the paste for filling the through holes of Example 1, dibenzylidene-D was used instead of the crystalline cellulose of B.
-Used 2-8 wt% sorbitol. In this case, when the compounding ratio is 2 wt% or less, a dent occurs after filling the through hole, and when it is 8 wt% or more, thixotropy is strong and unfilled. Even when this paste was used, cracks did not occur as in the example.

Example 3 A conductive paste having the following raw materials and compounding amounts was used as B with respect to the compounding ratio A of the through hole filling paste of Example 1.

Crystalline cellulose: 3 to 10 wt% Dibenzylidene-D-sorbitol: 0.5 to 5 wt% In this case, when the ratio of crystalline cellulose is 3 wt% or less, the occurrence of closed pores is small and 10 wt% or more. Then, the flow of the paste is poor and the filling becomes insufficient. The compounding ratio of dibenzylidene-D-sorbitol is 0.5 w.
When it is t% or less, the thixotropy is weak and the filled paste is dried and shrunk to cause dents. If it is 5 wt% or more, the thixotropy is too strong and the filling of the conductive paste into the through holes becomes insufficient. Even when this conductor paste was used, cracks did not occur as in Examples 1 and 2.

Example 4 To the through holes of Example 1, Zn and Mo are contained in an amount of 12 to 60 wt% of the Cu powder of 60 to 80 wt% as the conductor paste material.
A conductor paste was used that was mixed and did not contain crystalline cellulose. In this case, if the proportion of Zn and Mo is 12 wt% or less, there is no effect in reducing thermal stress, and if it is 60 wt% or more,
Electric resistance increases. The multilayer wiring board using this paste did not generate cracks as in Example 1.

[0013]

When the conductor paste of the present invention is used, the conductor paste can be easily filled in the through holes, cracks do not occur in the multilayer wiring board, and the conventional yield of 2% is 8%.
We were able to improve it to 6%, which enabled mass production.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view in which a through hole of a green sheet is filled with a conductive paste, for explaining the present invention.

FIG. 2 is a schematic sectional view of a green sheet filled with a conductor paste for explaining a conventional method.

[Explanation of symbols]

1 ... Green sheet, 2 ... Through hole, 3 ... Conductor paste, 4 ... Crystalline cellulose, 5 ... Depression due to drying shrinkage,
6 ... Cavity due to drying shrinkage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromi Tozaki 1 Horiyamashita, Hadano City, Kanagawa Hitachi Ltd. Kanagawa Plant (72) Inventor Shoichi Iwanaga 292 Yoshidacho, Totsuka-ku, Yokohama Hitachi Manufacturing Co., Ltd. (72) Inventor Etsuko Takane 292 Yoshida-cho, Totsuka-ku, Yokohama-shi Hitachi Production Engineering Laboratory (72) Inventor Norihiro Ami 292 Yoshida-cho, Totsuka-ku, Yokohama Hitachi-production Engineering Laboratory Co., Ltd.

Claims (4)

[Claims] 1. In manufacturing a glass-ceramic multilayer wiring board using an aqueous green sheet. A conductive paste characterized by comprising crystalline cellulose in the range of 3 to 20 wt% B with respect to A. 2. A conductor paste comprising dibenzylidene-D-sorbitol in an amount of 2 to 8 wt% in place of the additive B in claim 1. 3. A conductor paste comprising crystalline cellulose as an additive B according to claim 1 ... 3 to 10 wt% dibenzylidene-D-sorbitol ... 0.5 to 5 wt%. 4. As A of claim 1. A conductor paste comprising: