JPH0632356B2 - Mullite Ceramic Multilayer Wiring Board Conductor Paste - Google Patents

Description

The present invention relates to a ceramic multilayer wiring board, and is particularly suitable for forming a wiring conductor of a mullite (3Al ₂ O ₃ .2S _i O ₂ ) ceramic multilayer wiring board. Regarding conductor paste.

[Conventional technology]

At present, as a substrate for mounting semiconductor components at a high density, an alumina multilayer wiring substrate having multilayer wiring is often used. However, this alumina multilayer wiring board has a drawback that the signal propagation speed is slow. The signal propagation speed is
It is inversely proportional to the dielectric constant of the insulator surrounding the signal line (wiring conductor) and the resistance of the signal line. In order to increase the signal propagation speed, attention has been paid to mullite ceramics having a small relative dielectric constant. This material has a coefficient of thermal expansion between alumina and silicon, has a small difference in thermal expansion with semiconductor parts such as silicon chips, and has many advantages in terms of thermal stress, so various proposals have been made for practical use. There is
-23672, JP-A-55-139709). However, the mullite ceramic substrate does not have the same thermal and mechanical strength as the alumina substrate, and the wiring conductor layer is peeled off and cracks are generated in the through holes during the sintering and heat treatment processes. Has many problems.

On the other hand, the formation of the wiring conductor on the ceramic substrate is
As shown in FIGS. 3 and 4, through holes 2 are formed in an unsintered mullite ceramic sheet (mullite green sheet) 1, and the through holes 2 are densely filled with a conductor paste to form a through hole filling conductor paste 3 After forming, the wiring conductor paste 4 to be the signal line is formed. However, the conductor paste used for the conventional alumina green sheet (conductor paste containing metal powder such as tungsten and molybdenum as a conductor metal) has poor wettability with the mullite green sheet 1, and therefore the metal powder and the mullite are poor. The binding force with the green sheet 1 is reduced, and the conductor metal is detached with a slight force. In order to eliminate this drawback, a sintering aid is added to the conductor paste. However, when the sintering aid is used, the viscosity of the conductor paste becomes high, and the conductor paste is filled in the through hole. Becomes difficult to flow in, for example, the fourth
As shown in Fig. (A), it is not possible to fill densely and the void 7
Occurs. Therefore, by increasing the proportion of the solvent in the conductor paste and decreasing the viscosity to fill the through holes with the conductor paste, the solvent in the filled conductor paste is absorbed by the green sheet, and the volume of the conductor paste filled in the through holes is reduced. Decreased, as shown in FIG. 4 (b) or FIG. 4 (c),
The through-hole filling conductor paste 3 has a drawback that the recess 5 and the cavity 6 are easily generated.

[Problems to be solved by the invention]

As described above, in the prior art, no consideration has been given to the conductor paste used for forming the multilayer wiring of the mullite ceramic substrate, the printability of the conductor paste and the filling property into the through holes are poor, and the mullite green The warpage of the substrate due to the difference in sintering contraction with the sheet is large, and in the processes such as plating, sintering (sintering) and wire bonding performed after sintering, the wiring conductors may destroy the surface of the mullite substrate, There is a problem that the conductor is partially dropped and the wiring conductor pattern is broken.

An object of the present invention is to improve the viscosity of a conductor paste by adding a sintering aid and a titanate coupling agent having a specific composition that have been calcined at a specific temperature in order to solve the above problems. With proper adjustment, the content of conductive metal powder is increased to improve the printability of wiring conductor patterns and the fillability of through holes, and the warpage of the substrate due to the difference in sintering shrinkage between the conductor paste and mullite green sheet. It is an object of the present invention to provide a conductor paste having excellent properties in which the wiring conductor pattern is not broken even in the plating, sintering and wire bonding steps after sintering.

[Means for solving problems]

The above-mentioned purpose is obtained by calcining a mixture of magnesium carbonate, alumina and silica at a temperature of 1000 to 1400 ° C. with 100 parts by weight of a high melting point metal powder having an average particle diameter of 1 to 6 μm as a conductor metal or 1000 to 1400. 0.1-10 parts by weight of a sintering aid consisting of a mixture of alumina and silica in magnesium carbonate calcined at a temperature of 10 ° C, a vehicle of 10-20 parts by weight, and a titanate coupling agent of 0.1-2 parts by weight. And a gelling agent in an amount of 0.5 to 3 parts by weight.

[Action]

The conductor paste for a mullite ceramic multilayer wiring board according to the present invention is (1) sintered shrinkage by optimizing the average particle size of a refractory metal powder such as W or Mo, which is a wiring conductor metal,
It is possible to match the sintering shrinkage of the mullite green sheet, and it is possible to prevent the warp of the substrate and the dropping of the wiring conductor pattern due to the sintering. Also, (2) the viscosity of the conductor paste can be lowered by optimizing the calcination temperature of the sintering aid, thereby increasing the blending ratio of the wiring conductor metal powder and improving the filling property into the through holes. You can Furthermore, (3) By optimizing the compounding amount of the conductor paste raw material, it is possible to reduce the wiring resistance by improving the printability of the wiring conductor pattern, filling the through holes, and increasing the mixing ratio of the wiring conductor metal powder. it can. Also, (4)
Addition of titanate coupling agent can improve the wettability of sintering aid and vehicle, increase the amount of paste transfer in the printing of wiring conductors, and the phenomenon of skinning of the conductor paste surface (paste surface dries quickly). It is possible to prevent the phenomenon that a large amount of solvent remains inside, and to eliminate the dents and cavities that are likely to occur inside the conductor filled in the through holes. The coupling agents include isopropyl triisostearoyl titanate and tetra (2
-2-diallyloxymethyl-1-butyl) phosphite titanate, bis (dioctylpyrophosphite)
Oxyacetate titanate is effective.

〔Example〕

 Hereinafter, one embodiment of the present invention will be described in detail.

(Example 1) W powder (average particle diameter 1.5 μm): 100 g Sintering aid (calcination temperature: 1200 ° C.): 2 g Vehicle ……………………………… 15g Titanate coupling agent 1 g [Isopropyltriisostearoyl titanate] Gelling agent 1.5 g [Dibenzylidene-D-sorbitol] The conductive paste having the above content was kneaded with a three-roll mill for 2 hours for preparation. Apply this conductor paste to a mullite green sheet (with a size of 200 mm × 200 mm × 0.23 mmt, and
The through holes of about 40,000 through holes each having a diameter of 0.13 mm were formed at a grid point of 0.5 mm by an NC punch device) and were filled by a screen printing method. The conditions for this screen printing were as follows.

Squeegee attack angle: 30 degrees Squeegee speed: 3 cm / sec Squeegee load: 10 kg / 14 (squeegee length) Thus, 10 to 30 mullite green sheets filled with the conductive paste are pressed at a pressure of 120 kg / cm ^{2 and} a temperature of 150 ° C.
1600 ~ 1 after thermocompression bonding with hot press equipment at the temperature of
Firing was performed in a hydrogen reducing atmosphere furnace at a temperature of 660 ° C. for 1 hour.
The sintered mullite multilayer board had a warp of 0.3 mm / 100 mm and a through hole diameter of 0.1 mm. The surface of the W conductor in the through hole is silver gray and the surface roughness is 2-3 μmRma.
x, the W conductor inside the through hole was well connected to each other by W particles, densely sintered, and even when the cross section was polished, the W powder particles did not fall off, and there was no cavities in the through hole. . In addition, the N ₁ -B
After plating the electroless plating film of 2 to 10 μm in thickness,
After the sintering treatment was performed at a temperature of 850 ° C. for 10 minutes, the plated film in the through hole portion did not peel off. Further, no crack was generated in the mullite substrate portion near the through hole, and the resistance of the through hole portion was as small as 2 mΩ / layer.

Next, it is appropriate that the amount of the conductive paste material is 0.1 to 10 g with respect to 100 g of W powder and the amount of the sintering aid is less than this range. There is a tendency that W particles tend to settle down, and there are many gaps between W particles, so that the treatment liquid permeates in the next plating step and the surface of the plating film is discolored during sintering or the plating film is easily peeled off. On the contrary, when the amount of the above-mentioned sintering aid is larger than the above range, the sintering shrinkage is large, and a gap is apt to occur between the mullite ceramic and the W conductor. In addition, the electric resistance value becomes high, the plating does not easily deposit, the adhesion of the plating film is poor, and the plating film tends to peel off during the sintering treatment. Further, when the amount of vehicle is less than 10 g, the viscosity of the paste becomes high and the through hole cannot be filled. Further, if the amount exceeds 20 g, the amount of solvent increases, and the conductor paste filled in the through holes is likely to be recessed or cavities are generated. If the titanate-based coupling agent is less than 0.1 g, the sintering aid is poorly dispersed, so that the sintering aid is aggregated and the W powder is weakly sintered. On the other hand, when the amount exceeds 2 g, the viscosity of the conductor paste is greatly reduced, and the solvent is exuded more during the printing of the wiring conductor, or the adhesive force of the conductor paste is increased, resulting in the plate separation property (screen from the substrate The mullite green sheet is not easily separated from the screen surface, and the mullite green sheet tends to be damaged. The gelling agent
If the amount of benzylidene-D-sorbitol is less than 0.8 g, it is difficult to gel, so that the solvent of the filled paste is absorbed by the mullite green sheet, the volume of the conductive paste is reduced, and dents or cavities are generated in the through holes. . Further, when it exceeds 3 g, the viscosity of the conductor paste sharply increases, and it becomes difficult to fill the through hole. Furthermore, since the gap between the W particles becomes large, the W particles cannot be combined with each other at the time of termination, which tends to increase the electric resistance value of the W conductor.

Regarding the calcination temperature of the sintering aid, as shown in Fig. 1, the viscosity tends to be extremely high between 600 ° C and 900 ° C.
Above, the viscosity drops sharply. However, if the temperature exceeds 1400 ° C., the sintering aid itself is strongly sintered, an expensive device is required for crushing, and a long time is required for crushing, which is not preferable.

(Example 2) Instead of W powder at the compounding ratio of Example 1, an average particle size of 5 μm was used.
A conductor paste using M ₀ powder was prepared, and the conductor paste was filled in the through holes under the mullite green sheet and printing conditions in which the through holes were formed as in Example 1.
Sintering, plating, and sintering treatment were performed in the same manner as in Example 1. As a result, good results could not be obtained as with the W powder. In the case of M _o powder, if the average particle size of the powder is smaller than 3 μm, the sintering shrinkage is larger than that of mullite ceramics, and cracks occur on the mullite surface near the wiring conductor. On the other hand, if the average particle size is larger than 6 μm, irregularities on the surface of the conductor are large (surface roughness 6 to 20 μmR _max ), resulting in problems such as plating failure and wire bonding failure.

Example 3 W powder (average particle size 1.2 μm) 100 g Sintering aid (calcination temperature 1000 ° C.) 0.5 g Vehicle …………………… …………… 20g Titanate Coupling Agent: 1 g (Tetra (2.2-diallyloxymethyl-1-butylphosphaitotitanate)) A conductor paste having the above composition was kneaded with a three-roll mill for 2 hours for preparation.

Next, a mullite green sheet shown in Table 1 was prepared by the doctor blade method, through holes were formed in the same manner as in Example 1, and then the through holes were filled with the conductor paste used in Example 1.

A wiring pattern having a line width of 0.1 mm or a screen plate capable of solid printing on the entire surface of the sheet was used to form a wiring conductor layer by the screen printing method using the conductor paste in this example. Thus the sheet produced with 10 to 30 sheets, after firing by thermocompression bonding under the same conditions as in Example 1, the N _i -B plated film formed by electroless plating, followed by the annealing treatment I did. as a result,
The warp of the substrate was small as in Example 1, the wiring conductor was not peeled off and the substrate was not cracked, and a mullite ceramic multilayer wiring substrate having a wiring resistance of 0.5 to 0.8 mΩ / cm could be manufactured.

If the average particle size of the W powder is less than 1 μm, the shrinkage during firing is large and it is not suitable for a mullite substrate. If it exceeds 3 μm, the unevenness of the conductor surface becomes large and bonding cannot be performed. The amount of the sintering aid, the calcination temperature, the amount of the vehicle, and the titanate-based coupling agent are in the same applicable range as in Example 1.
The amount of dibenzylidene-D-sorbitol is 0.5 g.
If the amount is less than the above, there is no problem even if added. As for the M _o, results to prepare paste having an average particle size 3 to 6 [mu] m, with similar results as in the case of W powder. For this _Mo conductor paste, bis (dioctylpyrophosphite) oxyacetate titanate was used as a titanate coupling agent. As a result, it was effective because it had an effect on the dispersion of _Mo powder that easily aggregates.

〔The invention's effect〕

As described in detail above, the conductor paste for a mullite-based ceramic multilayer wiring board of the present invention is particularly excellent in wettability with a mullite green sheet, so that the printability of the wiring conductor pattern and the fillability in the through-hole portion are improved. well,
The yield in wiring conductor formation was about 5% in the conventional conductor paste, but it can be improved to 80% or more, and the yield can be further increased to 3 to 8 by performing simple repair. % Can be improved.

Further, the conductor paste of the present invention has a small difference in sintering shrinkage from the mullite green sheet, so that the warp of the substrate can be made extremely small. mm / 100mm, mullite-based ceramic multilayer with excellent performance by simple process similar to conventional alumina multilayer wiring board, with almost no drop of wiring conductor pattern in plating and sintering process after sintering. A wiring board can be manufactured.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the calcination temperature of a sintering aid and the viscosity of a conductor paste in Example 1 of the present invention, and FIG. 2 is a perspective view showing through holes of a mullite green sheet.
FIG. 3 is a perspective view showing a through hole and a wiring conductor paste filled with a conductor paste, and FIGS. 4 (a), (b), and (c) are filling states of a through hole portion when a conventional conductor paste is used. FIG. 1 ... Mullite green sheet 2 ... Through hole 3 ... Through hole filling conductor paste 4 ... Wiring conductor paste 5 ... Recess 6 ... Cavity 7 ... Void

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Seiichi Machida, Inventor Seiichi Hamada, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Hitachi, Ltd. Institute of Industrial Science (72) Inventor Tatsuji Noma 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa House number Production company Hitachi, Ltd. Production Technology Research Laboratory (72) Inventor Takeshi Fujita No. 292 Yoshida-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture

Claims (1)

[Claims] 1. As a conductor metal, 100 parts by weight of a refractory metal powder having an average particle size of 1 to 6 μm and a mixture of magnesium carbonate, alumina and silica calcined at a temperature of 1000 to 1400 ° C. or 1000 to 0.1-10 parts by weight of a sintering aid consisting of a mixture of alumina and silica in magnesium carbonate calcined at a temperature of 1400 ° C, a vehicle of 10-20 parts by weight, and a titanate coupling agent of 0.1-2 parts by weight. And a gelling agent in an amount of 0.5 to 3 parts by weight, a conductor paste for a mullite-based ceramic multilayer wiring board.