JP4099837B2 - Low temperature fired ceramic multilayer substrate manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a low- temperature fired ceramic multilayer substrate, in which a low- temperature fired ceramic multilayer substrate is produced using a conductor paste for low-temperature fired ceramic containing Ag-based metal powder.
[0002]
[Prior art]
Conventionally, in a low-temperature fired ceramic substrate fired at 1000 ° C. or lower, a low melting point metal such as Ag, Au, Ag—Pd, Ag—Pt, or Cu is used as a conductor for simultaneous firing. Among these metals, Au is expensive, so the range of use is limited from the viewpoint of cost, and Ag—Pd and Ag—Pt have a drawback that the resistance value is greatly increased by alloying. Further, since Cu oxidizes when fired in the air (in an oxidizing atmosphere), it must be fired simultaneously in a reducing atmosphere (N ₂ ), resulting in a high firing cost. In this respect, Ag can be baked in air, has a smaller resistance value than Ag—Pd, and Ag—Pt, and is less expensive than Au, which is advantageous in terms of cost.
[0003]
[Problems to be solved by the invention]
However, since Ag has the lowest melting point (960.7 ° C.) among the above-mentioned low melting point metals, when it is simultaneously fired with a low-temperature fired ceramic fired at 850 ° C. or higher, Ag becomes over-sintered and firing shrinkage is large. Become. Therefore, when the Ag paste is used as the conductor paste for simultaneous firing of the low-temperature fired ceramic substrate, the Ag via conductors 12 and 13 filled in the via hole 11 are excessive as shown in FIG. Due to firing shrinkage, and a gap 14 is generated in the interlayer connection portion of the inner via conductor 12 to cause a decrease in connection reliability of the via conductor 12, or directly above the via conductor 13 on the substrate surface layer. A depression is generated in the formed pad 15, causing a reduction in bonding reliability of the semiconductor chip bonded to the pad 15.
[0004]
The present invention has been made in consideration of such circumstances, and the object thereof is to provide a conductor paste for low-temperature fired ceramics that can reduce the amount of firing shrinkage while being an Ag-based conductor paste, Furthermore, it is providing the manufacturing method of the low-temperature baking ceramic multilayer substrate which can improve the reliability of the conductor co-fired with a low-temperature baking ceramic.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the conductor paste for low-temperature fired ceramic used in the method for producing a low-temperature fired ceramic multilayer substrate of the present invention contains an Ag-based metal powder as a conductor, and an oxidation start temperature as a sintering inhibitor. Contains silicide powders of 300 ° C. or higher . Thus, the powder of the oxide starting temperature is 300 ° C. or more silicides by blending the Ag-based conductor paste, the sintering rate of the Ag-based conductor paste in accordance with the sintering rate of the low-temperature fired ceramic during simultaneous firing It is possible to slow down and excessive sintering of the Ag-based conductor can be prevented.
[0006]
In this case, the mixing ratio of the Ag-based metal powder and the silicide is preferably 50 to 99.5% by weight for the Ag-based metal powder and 0.5 to 50% by weight for the silicide. ). If it is this compounding ratio, the low resistance characteristic as an Ag-type conductor and the sintering inhibitory effect by a silicide can be compatible.
[0007]
Then, as in the method for manufacturing a low-temperature fired ceramic multilayer substrate of the present invention, by printing a conductive paste containing a silicide above the plurality of low temperature co-fired ceramic green sheet, by co-firing the stacked them, A good quality low-temperature fired ceramic multilayer substrate with a small difference in firing shrinkage between the conductor and the ceramic can be produced.
[0008]
According to a third aspect of the present invention, via conductors containing the silicide described above are filled into a via hole formed in a green sheet of low-temperature fired ceramic by printing to form a via conductor, and then the via conductor is formed on the via conductor. It is possible to produce a low-temperature fired ceramic multilayer substrate by printing a conductive paste containing no chemical compound to form a pad, laminating the green sheet as the uppermost layer and laminating it with other printed green sheets. good. In this way, excessive sintering of the via conductor can be prevented, and voids and dents due to excessive sintering can be prevented from occurring in the via conductor. Moreover, the pad is to be formed by a conductor containing no silicides, Ru it is possible to suppress an increase in resistance due to silicide.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In one embodiment of the present invention shown in FIG. 1 (a), 50 to 65% by weight of CaO—SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ glass and alumina are used as the ceramic material for the low-temperature fired ceramic green sheet 21. A mixture of 35-50% by weight is used. In addition, a mixture of MgO—SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ glass and alumina powder, a mixture of SiO ₂ —B ₂ O ₃ glass and alumina, PbO—SiO ₂ —B ₂ O _A low-temperature fired ceramic material that can be fired at 800 to 1000 ° C., such as a mixture of ₃ glass and alumina, cordierite crystallized glass, or the like may be used. A via hole 22 having a diameter of 50 to 1000 μm is punched and formed on the green sheet 21 by a punching machine or a punching die.
[0010]
The conductor paste filled in the via hole 22 includes Ag powder as a conductor, and includes silicide powder having an oxidation start temperature of 300 ° C. or higher as a sintering inhibitor. The oxidation initiation temperature of 300 ° C. or more silicide, there is _{CrSi 2, TaSi 2, ZrSi 2} , WSi 2, NbSi 2, TiSi 2, MoSi 2 or the like as shown in FIG. 2, one or among these A plurality of types of silicides may be selected and blended into the conductor paste. Here, it is preferable that the compounding ratio of Ag powder and silicide powder is 50 to 99.5% by weight for Ag powder and 0.5 to 50% by weight for silicide. The conductor paste contains a binder resin and an organic solvent in addition to Ag powder and silicide.
[0011]
The conductor paste containing the silicide is screen-printed and filled in the via hole 22 of the green sheet 21 of each layer to form the via conductor 23. Furthermore, the inner layer wiring pattern 24 is screen-printed on the surface of the inner layer green sheet 21 using a low-temperature fired ceramic conductor paste that does not contain silicide, and on the via conductors 23 of the uppermost layer green sheet 21 as necessary. Accordingly, the pad 25 may be formed by printing a low-temperature fired ceramic conductor paste that does not contain silicide. At this time, an Ag paste, an Ag—Pd paste, an Ag—Pt paste, or the like may be used as the low-temperature fired ceramic conductor paste that does not contain silicide.
[0012]
After completion of the printing process, the green sheets 21 of each layer are stacked and pressure-bonded, and this is fired at 800 to 1000 ° C. in the air. Finally, Ni / Au plating is applied to the surface of the pad 25.
[0013]
As described above, by mixing the silicide into the Ag-based conductor paste filled in the via hole 22, the sintering speed of the Ag-based via conductor 23 can be adjusted in accordance with the sintering speed of the low-temperature fired ceramic at the time of simultaneous firing. The via conductor 23 can be prevented from being excessively sintered, and the firing shrinkage amount of the via conductor 23 can be brought close to the firing shrinkage amount of the low-temperature fired ceramic. Thereby, it is possible to prevent a void due to oversintering from occurring in the interlayer connection portion of the via conductor 23, to improve the connection reliability of the via conductor 23, and to generate a dent in the pad 25 on the via conductor 23. This can be prevented, and the bonding reliability of the semiconductor chip bonded to the pad 25 can be improved.
[0014]
By the way, when a silicide is blended in the conductor paste, the resistance value becomes larger than that containing no silicide, but if the blending amount of the silicide is 50% by weight or less, the resistance value falls within an allowable range. Moreover, as the compounding amount of the silicide decreases, the sintering suppressing effect decreases. However, if the compounding amount of the silicide is 0.5% by weight or more, a certain degree of sintering suppressing effect can be obtained. Therefore, if the mixing ratio of Ag powder and silicide is: Ag powder: 50 to 99.5% by weight, Silicide: 0.5 to 50% by weight, low resistance characteristics as an Ag paste and firing with silicide It is possible to achieve both an anti-settling effect.
[0015]
Furthermore, in the above-described embodiment, only the via conductor 23 in which oversintering is a problem is formed with an Ag paste containing silicide, and the pad 25 and the inner layer wiring pattern 24 in which oversintering is not so much a problem include silicide. Since it is made of a non-conductive paste, it can eliminate problems such as dents in the pad 25 due to oversintering while minimizing the increase in resistance due to silicide, producing a high-quality low-temperature fired ceramic multilayer substrate can do.
[0016]
However, in the present invention, the pad 25 and the inner layer wiring pattern 24 may also be formed of a conductor paste containing silicide. In this case, the resistance value can be lowered by reducing the compounding amount of silicide. can do.
[0017]
【The invention's effect】
As apparent from the above description, according to the present invention, since the oxidation start temperature of the sintering inhibiting material in the conductor paste of Ag system is to use a thing blended with powder of 300 ° C. or more silicides, Although it is an Ag-based conductor paste, excessive sintering during simultaneous firing can be prevented, and the firing shrinkage of the conductor can be brought close to that of the low-temperature fired ceramic.
[0018]
Furthermore, by using a conductor paste in which the compounding ratio of the Ag-based metal powder and the silicide is Ag-based metal powder: 50 to 99.5% by weight, and silicide: 0.5 to 50% by weight, Ag is used. The sintering suppression effect by silicide can be obtained without losing the low resistance characteristic as a system conductor (Claim 2).
[0019]
In addition, via conductors that cause oversintering are formed with a conductor paste containing silicide , and the pad is formed with a conductor paste that does not contain silicide, while suppressing an increase in resistance due to silicide. A sufficient sintering suppressing effect can be obtained (claim 3).
[Brief description of the drawings]
1A is a partially enlarged longitudinal sectional view of a low-temperature fired ceramic multilayer substrate in one embodiment of the present invention, and FIG. 1B is a partially enlarged longitudinal sectional view of a conventional low-temperature fired ceramic multilayer substrate.
Figure showing the relationship between the average particle size and oxidation start temperature of various silicide powders
21 ... green sheet, 22 ... via hole, 23 ... via conductor, 24 ... inner wiring pattern, 25 ... pad.

Claims (3)

Printing a low-temperature fired ceramic conductor paste containing Ag-based metal powder as a conductor and silicide powder with an oxidation start temperature of 300 ° C. or higher as a sintering inhibitor on a plurality of low-temperature fired ceramic green sheets And a method for producing a low-temperature fired ceramic multilayer substrate, wherein these are laminated and fired simultaneously.   As the conductor paste for low-temperature fired ceramic, the mixing ratio of the Ag-based metal powder and the silicide is 50 to 99.5% by weight for the Ag-based metal powder and 0.5 to 50% by weight for the silicide. The method for producing a low-temperature fired ceramic multilayer substrate according to claim 1, wherein a certain one is used. A via hole formed in the green sheet, after forming a via conductor previous SL LTCC conductor paste is filled by printing, on the via conductors, printed LTCC conductor paste containing no silicides The low-temperature fired ceramic multilayer substrate according to claim 1 , wherein a pad is formed, the green sheet is used as an uppermost layer, and the green sheet is laminated with another printed green sheet and simultaneously fired . Production method.

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