Multilayer glass ceramic substrate and process for producing the same

Abstract: A multilayer glass ceramic substrate having a plurality of conductor layers each laminated through a glass ceramic layer. The glass ceramic layer has a composition comprising of alumina, borosilicate magnesium glass and cordierite crystal produced by chemical reaction between alumina and borosilicate magnesium glass. The content of alumina is 12 to 59.6 wt%, the content of borosilicate magnesium glass is 18 to 69.6 wt%, the content of the cordierite crystal is 1 to 50 wt% and the sum of components is 100 wt%. The multilayer glass ceramic substrate shows improved mechanical strength.

Description: Background of the Invention Field of the Invention The present invention relates to a multilayer glass ceramic substrate used for high density implementation of LSI elements and more specifically to a multilayer glass ceramic substrate which can be sintered at low temperatures and to a process for producing the same. Description of the related arts Development of semiconductor technology requires down-sizing and high-speed of electronics devices and systems. In fact, as the semiconductor elements are integrated into VLSI and ULSI of high density, very high density and fine-processing are required in the implementation technique for assembling the elements. In particular, it is requested to increase the wiring density of the substrate on which semiconductor elements are implemented so as to comply with finer pattering and higher operation speed and to lower the dielectric constant of substrate materials. Alumina multilayer substrate has been used widely. This substrate is produced by a thick film printed multilayer technique or a green sheet lamination technique. The litter technique is more advantageous so as to satisfy the requirement of high-density integration. In the green sheet lamination technique, a plurality of thin ceramic green sheets each on which wiring lines are printed are laminated before being integrated, so that it is easy to increase the wiring layers to a desired number and hence the wiring density can be increased compared to the thick film printed multilayer technique. Alumina ceramic, however, has the disadvantage that sintering must be carried out above 1,500 °C which requires to use, as wiring conductor, Mo, W metal having a relatively high electric resistance and hence it is difficult to realize fine wiring. Still more, the dielectric constant of alumina is about 10 which is too high for high-speed operation of signals. Recently, ceramic materials which can be sintered at relatively lower temperatures have been developed so that low resistance conductors such as Au, Ag-Pd, Ag or Cu can be used. For example, a composite material consisting of alumina and borosilicate lead glass can be sintered at a low temperature below 1,000°C to produce a multilayer substrate in which Au, Ag-Pd or Ag can be used as a wiring conductor. However, in this composite material, it is difficult to use wiring of Cu which is a base metal because the composite material contains lead and hence sintering can not be carried out in a reduction atmosphere. Still more, the electric constant of this composite material can not be lowered below 7.5. Glass ceramic material using borosilicate glass is also known. This glass ceramic material can be sintered at a temperature lower than 1,000°C in a reduction atmosphere and has lower dielectric constant of about 5.5, so that a multilayered structure having wiring lines of Cu can be realized simultaneously at the sintering of glass ceramic. Known glass ceramic material, however, possess very poor mechanical strength because no crystallization occur by the sintering. The mechanical strength is a very important factor of the substrate. In fact, in the case of a multi-chip implementation substrate on which a large number of semiconductor elements are implemented, the substrate size increases and input/output terminals or pins are connected at different levels, and therefore, if the mechanical strength of the substrate is poor, problems of breakage of the substrate, junction failure or the like occur during the assembly stage and on the finished product. The documents JP-A-3060443 (WPI/DERWENT AN 91-121370) and JP-A-2225339 (Chemical Abstracts 114 (1991) No. 18) each disclose a low temperature firing and/or high-strength glass ceramic product as defined in the preamble part of claims 1 and 2. In each case the cordierite which contributes to the improved mechanical strength of the glass ceramic product is incorporated by using it as one of the starting materials for preparing the powder mixture which is subsequently compressed and fired to obtain the glass ceramic body. It is an object of the invention to further improve the glass ceramic substrate known from this prior art. According to the invention this object is solved by a multilayer glass ceramic substrate as defined in claim 1 or 2 and by a method as defined in claim 3 or 4. The invention differs from the afore mentioned prior art in that the cordierite is not used as a starting product but is obtained by chemical reaction during the sintering process. In the process according to the present invention, cordierite crystals are produce when alumina powder and borosilicate magnesium glass powder are sintered. Alumina powder has preferably the average particle size of 0.5 to 3 µm and borosilicate magnesium glass powder has preferably the average particle size of 1 to 5 µm. The third powder referred to in claim 4 has preferably the average particle size of 0.5 to 10 µm. The content of magnesium in the borosilicate magnesium glass is preferably more than 5 wt% in term of magnesium oxide. In the process according to the present invention, the material powders or green sheets are sintered below 1,000 °C to produce a multilayer glass ceramic substrate having improved properties because of following reason. In the sintering, borosilicate magnesium glass start to be softened at about 700°C. The resulting liquidized glass penetrate into and fill in spaces or clearances among ceramic powders of alumina, among ceramic powders of alumina and cordierite crystals and among ceramic powders of alumina, cordierite crystals and quartz glass, α-quartz or mullite to produce packed structure and a completely compacted glass ceramic body is formed finally at a temperature range form 800 to 1,000 °C. The material powders or green sheets of the present invention can be sintered in a reduction atmosphere because the material powders of the present invention do not contain an element that is reduced to elemental metal from oxide under the sintering condition. To the contrary, in the case of known material powders containing for example lead oxide, lead oxide is converted, in the reduction atmosphere, to metal lead which seriously deteriorate the insulation properry of the resulting glass ceramic body obtained. The multilayer glass ceramic substrate according to the present invention possesses improved mechanical strength which is one of very important properties required in implementation of semiconductor elements. Usually, a bending strength of higher than 2,000 kg/cm 2 is required in the substrate for implementing semiconductor elements. The multilayer glass ceramic substrate according to the present invention satisfies this strength because a compacted fine structure is realized by the sintering. In fact, the reaction between alumina and liquidized glass produces the cordierite crystal, so that the resulting glass ceramic obtained by the sintering possess a fine strong structure in which particles of alumina, particles of cordierite crystal (and also particles of quartz glass, α-quartz or mullite, if they exist) and glassy mass are bonded three-dimensionally and which has an improved bending strength. In the process according to the present invention, sintering can be effected below 1,000 °C, the multilayer structure can be easily realized by the green sheet lamination technique and any conductor including basic metals such as Cu, Ni, their alloys or those that must be sintered in neutral or reduction atmosphere in addition to noble metals of Au, Ag, Pd, Pt or the like can be used. The multilayer glass ceramic substrate according to the present invention possesses improved mechanical strength or bending strength of higher than 2,000 kg/cm 2 and low dielectric constant and makes it possible to realize fine wiring with high implementation density. Description of the Preferred Embodiment Now, Examples of the present invention is explained but the present invention is not limited to the Examples. Example 1 (Alumina + borosilicate magnesium glass) As material powders, alumina powder and borosilicate magnesium glass powder were used. Alumina powder having the average particle size of 0.5 µm to 3 µm and borosilicate magnesium glass powder having the average particle size of 1 to 5 µm were intimately mixed at a proportion range from 30 wt% : 70 wt% to 60 wt% : 40 wt%. Borosilicate magnesium glass used have following composition by weight: B 2 O 5 15 CaO 1 SiO 2 65 BaO 1 MgO 12 TiO 2 1 Na 2 O 2 ZrO 2 1 K 2 O 2 The resulting mixed material powder was dispersed together with an organic binder of polyvinyl butyral, polyvinyl alcohol or polyacrylic resin in a solvent to prepare a slurry from which a green sheet was molded by slip casting technique. The thickness of the green sheet was adjusted in a range from 10 to 400 µm. Then, via halls connecting upper and lower conductors were formed in the green sheet by a punching machine. A wiring pattern was printed by screen printing technique with conductor past and the via halls were filled with the conductor past. The conductor past used consisted mainly of Au, Ag, Ag-Pd, Cu, Ni or Ag-Pt. Predetermined numbers of green sheets each on which the conductor pattern was printed and of which the via hall was filled were laminated and compacted under heat. Then, the laminated green sheets were heated to a temperature of 400 to 700 °C to remove the organic binder and the solvent (elimination of binder). Finally, the laminated green sheets were sintered at a temperature ranging form 800 to 1,000 °C to obtain a multilayer glass ceramic substrate. During this sintering stage, the cordierite crystal is produced by a chemical reaction between alumina and borosilicate magnesium glass and the softened glass mass penetrate into and fill spaces or clearances among particles so as to promote compacted structure. Composition of glass ceramic layer of sintered substrates obtained are summarized in Table 1. The composition was determined by usual X-ray diffraction method. The contents of alumina and cordierite crystal which are determined by comparing their peaks to a peak of silicon used as a reference and a proportion of borosilicate magnesium glass is calculated by subtracting their contents from the total. Conductor, sintering conditions, numbers of layers and wiring specification used for manufacturing multilayer glass ceramic substrates as well as the results obtained are summarized in Tables 2 and 3. The sample numbers in Table 1 correspond to those in Tables 2 and 3. Alumina + borosilicate magnesium glass Sample Number Composition ratio (wt %) Alumina Borosilicate glass Cordierite crystal 1 12 38 50 2 12 43 45 3 12 48 40 4 17.4 32.6 50 5 18.1 37.6 44.3 6 18.2 50.1 31.7 7 22.0 29.1 48.9 8 23.2 39.5 37.3 9 23.3 48.7 28.0 10 23.5 57.3 19.2 11 27.9 29.8 42.3 12 28.1 41.0 30.9 13 28.1 50.5 21.4 14 28.3 61.8 9.9 15 33.2 18.9 47.8 16 33.3 31.6 35.1 17 33.3 35.3 31.4 18 33.5 46.9 19.6 19 38.4 27.7 33.9 20 38.4 31.4 30.2 21 38.7 34.7 26.6 22 38.8 50.7 10.5 23 42.0 18.0 40 24 42.1 33.8 24.1 25 42.1 37.3 20.6 26 42.3 43.2 14.5 27 46.3 38.2 15.5 28 46.3 43.7 10.0 29 48.4 18.0 33.6 30 48.6 20.9 30.5 31 48.7 29.8 21.5 32 48.7 35.2 16.1 33 52.5 21.8 25.7 34 52.5 27.4 20.1 35 52.6 30.3 17.1 36 52.8 34.1 13.1 37 56.1 29.8 14.1 38 56.3 33.7 10 39 56.3 38.5 5.2 40 56.5 42.5 1.0 Tables 2 and 3 reveal such facts that multilayer glass ceramic substrates having the compositions according to the present invention shown in Table 1 posses improved properties required in practical uses including satisfactory mechanical strength and that fine wiring of high-density can made easily. On the contrary, when the content of alumina is less than 12 wt%, the bending strength of substrate become lower than 2,000 kg/cm 2 and is insufficient. If the alumina content exceed 59.6 wt%, sintering can not be carried out below 1,000 °C so that the insulation resistance decrease and that the bending strength become lower than 2,000 kg/cm 2 and the dielectric constant becomes higher than 7, which is disadvantageous for high-speed circuits. In these cases, practical multilayer glass ceramic substrate can not be produced. When the content of borosilicate magnesium glass is not higher than 18 wt%, it is impossible to obtain a glass phase sufficient to fill spaces or clearances among alumina particles, so that the strength become lower and the reliability can not be expected. If the content of borosilicate magnesium glass exceed 69.6 wt%, the strength intrinsic to glass dominates so that the bending strength become less than 2,000 kg/cm 2 . If the content of the cordierite crystal is less than 1 wt%, the effect for reinforcing the strength obtained by the presence of cordierite crystals can not be expected so that it is impossible to obtain the bending strength of more than 2,000 kg/cm 2 . If the content of the cordierite crystal exceed 50 wt%, the multilayer glass ceramic substrate does not shrink uniformly and hence the reliability is lost. If the content of magnesium in the borosilicate magnesium glass used as a material powder becomes less than 5 wt% in term of magnesium oxide, no or little cordierite crystal is produced by sintering operation. If the particle size of alumina powder used becomes lower than 0.5 µm or higher than 3 µm, and if the particle size of borosilicate magnesium glass powder become lower than 1 µm or higher than 5 µm, the mixed material powder can not be sintered satisfactorily, so that the resulting multilayer glass ceramic substrate shows very poor reliability and hence can not be used in practical uses. Example 2 (Alumina + borosilicate magnesium glass + silica glass) Example 1 is repeated except silica glass was added to the material powders of alumina powder and borosilicate magnesium glass powder. Namely, alumina powder having the average particle size of 0.5 µm to 3 µm, borosilicate magnesium glass powder having the average particle size of 1 to 5 µm and silica glass powder having the average particle size of 0.5 µm to 10 µm were intimately mixed at a proportion of (alumina + silica glass) : borosilicate magnesium glass of from 30 wt% : 70 wt% to 60 wt% : 40 wt%. The proportion of alumina powder was adjusted above 10 wt %. Composition of glass ceramic layer of sintered substrates obtained are summarized in Table 4 and conductor, sintering conditions, numbers of layers and wiring specification used for manufacturing multilayer glass ceramic substrates as well as the results obtained are summarized in Tables 5 and 6. The sample numbers in Table 4 correspond to those in Tables 5 and 6. Alumina + borosilicate magnesium glass + silica glass Sample Number Composition ratio (wt%) Alumina Silica glass Borosilicate type Glass Cordierite crystal 101 12.0 21.0 37.0 30.0 102 12.0 30.0 33.0 25.0 103 12.4 11.0 69.6 20.0 104 17.0 25.0 32.0 26.0 105 17.0 10.0 23.0 50.0 106 18.0 21.0 40.0 21.0 107 22.0 18.0 25.0 35.0 108 23.0 15.0 27.0 35.0 109 23.0 19.0 38.0 20.0 110 23.0 24.0 20.0 33.0 111 28.0 20.0 19.0 33.0 112 28.0 11.0 51.0 10.0 113 28.0 17.0 40.0 15.0 114 28.0 17.0 35.0 20.0 115 33.0 17.0 36.0 14.0 116 33.0 12.0 25.0 30.0 117 33.0 18.0 20.0 29.0 118 34.0 10.0 45.0 11.0 119 38.0 19.0 18.0 25.0 120 38.0 24.0 24.0 14.0 121 39.0 15.0 28.0 18.0 122 39.0 11.0 40.0 10.0 123 42.0 11.0 18.0 29.0 124 42.0 12.0 28.0 18.0 125 42.0 10.0 30.0 18.0 126 42.5 13.0 34.5 10.0 127 46.0 10.0 31.0 23.0 128 46.0 11.0 33.0 10.0 129 48.0 11.0 18.0 23.0 130 48.0 12.0 21.0 19.0 131 49.0 10.0 21.0 20.0 132 49.0 15.0 26.0 10.0 133 52.0 12.0 18.0 18.0 134 52.0 12.0 20.0 16.0 135 53.0 11.0 22.0 14.0 136 53.0 11.0 24.0 12.0 137 56.0 10.0 25.0 9.0 138 56.0 10.0 21.0 13.0 139 57.0 10.0 24.0 9.0 140 59.6 10.0 19.4 11.0 When the content of silica glass powder is less than 10 wt%, the dielectric constant become higher than 7. On the other hand, if the content of silica glass powder exceed 30 wt%, satisfactory sintering can not be carried out so that the insulation resistance becomes lower and the bending strength become lower than 2,000 kg/cm 2 . When the particle size of alumina powder used becomes lower than 0.5 µm or higher than 3 µm, the particle size of borosilicate magnesium glass powder become lower than 1 µm or higher than 5 µm and the particle size of silica glass powder become lower than 0.5 µm or higher than 10 µm, the mixed material powder can not be sintered satisfactorily, so that the resulting multilayer glass ceramic substrate shows very poor reliability and hence can not be used in practical uses. By the same reason as Example 1, practical multilayer glass ceramic substrate can not be obtained outside the proportions according to the present invention (12 to 59.6 wt% of alumina, 18 to 69.6 wt% of borosilicate magnesium glass and higher than 1 wt% of cordierite crystal). By the same reason as Example 1, if the content of magnesium in the borosilicate magnesium glass used becomes less than 5 wt% in term of magnesium oxide, no or little cordierite crystal is produced by sintering operation. Example 3 (Alumina + borosilicate magnesium glass + mullite) Example 2 is repeated except silica glass was replaced by mullite powder. Namely, alumina powder, borosilicate magnesium glass powder and mullite powder having the average particle size of 0.5 µm to 10 µm were intimately mixed at a proportion of (alumina + mullite) : borosilicate magnesium glass of from 30 wt% : 70 wt% to 60 wt% : 40 wt%. The proportion of alumina powder was adjusted above 10 wt %. Composition of glass ceramic layer of sintered substrates obtained are summarized in Table 7 and conductor, sintering conditions, numbers of layers and wiring specification used for manufacturing multilayer glass ceramic substrates as well as the results obtained are summarized in Tables 8 and 9. The sample numbers in Table 7 correspond to those in Tables 8 and 9. Alumina + borosilicate magnesium glass + mullite Sample Number Composition ratio (wt%) Alumina Mullite Borosilicate type Glass Cordierite crystal 201 12.0 21.0 37.0 30.0 202 12.0 30.0 33.0 25.0 203 12.4 11.0 69.6 20.0 204 17.0 25.0 32.0 26.0 205 17.0 10.0 23.0 50.0 206 18.0 21.0 40.0 21.0 207 22.0 18.0 25.0 35.0 208 23.0 15.0 27.0 35.0 209 23.0 19.0 38.0 20.0 210 23.0 24.0 20.0 33.0 211 28.0 20.0 19.0 33.0 212 28.0 11.0 51.0 10.0 213 28.0 17.0 40.0 15.0 214 28.0 17.0 35.0 20.0 215 33.0 17.0 36.0 14.0 216 33.0 12.0 25.0 30.0 217 33.0 18.0 20.0 29.0 218 34.0 10.0 45.0 11.0 219 38.0 19.0 18.0 25.0 220 38.0 24.0 24.0 14.0 221 39.0 15.0 28.0 18.0 222 39.0 11.0 40.0 10.0 223 42.0 11.0 18.0 29.0 224 42.0 12.0 28.0 18.0 225 42.0 10.0 30.0 18.0 226 42.5 13.0 34.5 10.0 227 46.0 10.0 31.0 23.0 228 46.0 11.0 33.0 10.0 229 48.0 11.0 18.0 23.0 230 48.0 12.0 21.0 19.0 231 49.0 10.0 21.0 20.0 232 49.0 15.0 26.0 10.0 233 52.0 12.0 18.0 18.0 234 52.0 12.0 20.0 16.0 235 53.0 11.0 22.0 14.0 236 53.0 11.0 24.0 12.0 237 56.0 10.0 25.0 9.0 238 56.0 10.0 21.0 13.0 239 57.0 10.0 24.0 9.0 240 59.6 10.0 19.4 11.0 When the content of mullite powder is less than 10 wt%, the dielectric constant become higher than 7. On the other hand, if the content of mullite powder exceed 30 wt%, satisfactory sintering can not be carried out so that the insulation resistance becomes lower and the bending strength become lower than 2,000 kg/cm 2 . When the particle size of alumina powder used becomes lower than 0.5 µm or higher than 3 µm, the particle size of borosilicate magnesium glass powder become lower than 1 µm or higher than 5 µm and the particle size of mullite powder become lower than 0.5 µm or higher than 10 µm, the mixed material powder can not be sintered satisfactorily, so that the resulting multilayer glass ceramic substrate shows very poor reliability and hence can not be used in practical uses. By the same reason as Example 2, practical multilayer glass ceramic substrate can not be obtained outside the proportions according to the present invention (12 to 59.6 wt% of alumina, 18 to 69.6 wt% of borosilicate magnesium glass and higher than 1 wt% of cordierite crystal). By the same reason as Example 2, if the content of magnesium in the borosilicate magnesium glass used becomes less than 5 wt% in term of magnesium oxide, no or little cordierite crystal is produced by sintering operation. Example 4 (Alumina + borosilicate magnesium glass + α-quartz) Example 2 is repeated except silica glass was replaced by α-quartz powder. Namely, alumina powder, borosilicate magnesium glass powder and α-quartz powder having the average particle size of 0.5 µm to 10 µm were intimately mixed at a proportion of (alumina + α-quartz) : borosilicate magnesium glass of from 30 wt% : 70 wt% to 60 wt% : 40 wt%. The proportion of alumina powder was adjusted above 10 wt %. Composition of glass ceramic layer of sintered substrates obtained are summarized in Table 10 and conductor, sintering conditions, numbers of layers and wiring specification used for manufacturing multilayer glass ceramic substrates as well as the results obtained are summarized in Tables 11 and 12. The sample numbers in Table 10 correspond to those in Tables 11 and 12. Alumina + borosilicate magnesium glass + α-quartz Sample Number Composition ratio (wt%) Alumina α-quartz Borosilicate type Glass Cordierite crystal 301 12.0 21.0 37.0 30.0 302 12.0 30.0 33.0 25.0 303 12.4 11.0 69.6 20.0 304 17.0 25.0 32.0 26.0 305 17.0 10.0 23.0 50.0 306 18.0 21.0 40.0 21.0 307 22.0 18.0 25.0 35.0 308 23.0 15.0 27.0 35.0 309 23.0 19.0 38.0 20.0 310 23.0 24.0 20.0 33.0 311 28.0 20.0 19.0 33.0 312 28.0 11.0 51.0 10.0 313 28.0 17.0 40.0 15.0 314 28.0 17.0 35.0 20.0 315 33.0 17.0 36.0 14.0 316 33.0 12.0 25.0 30.0 317 33.0 18.0 20.0 29.0 318 34.0 10.0 45.0 11.0 319 38.0 19.0 18.0 25.0 320 38.0 24.0 24.0 14.0 321 39.0 15.0 28.0 18.0 322 39.0 11.0 40.0 10.0 323 42.0 11.0 18.0 29.0 324 42.0 12.0 28.0 18.0 325 42.0 10.0 30.0 18.0 326 42.5 13.0 34.5 10.0 327 46.0 10.0 31.0 23.0 328 46.0 11.0 33.0 10.0 329 48.0 11.0 18.0 23.0 330 48.0 12.0 21.0 19.0 331 49.0 10.0 21.0 20.0 332 49.0 15.0 26.0 10.0 333 52.0 12.0 18.0 18.0 334 52.0 12.0 20.0 16.0 335 53.0 11.0 22.0 14.0 336 53.0 11.0 24.0 12.0 337 56.0 10.0 25.0 9.0 338 56.0 10.0 21.0 13.0 339 57.0 10.0 24.0 9.0 340 59.6 10.0 19.4 11.0 When the content of α-quartz powder is less than 10 wt%, the dielectric constant become higher than 7. On the other hand, if the content of α-quartz powder exceed 30 wt%, satisfactory sintering can not be carried out so that the insulation resistance becomes lower and the bending strength become lower than 2,000 kg/cm 2 . When the particle size of alumina powder used becomes lower than 0.5 µm or higher than 3 µm, the particle size of borosilicate magnesium glass powder become lower than 1 µm or higher than 5 µm and the particle size of α-quartz powder become lower than 0.5 µm or higher than 10 µm, the mixed material powder can not be sintered satisfactorily, so that the resulting multilayer glass ceramic substrate shows very poor reliability and hence can not be used in practical uses. By the same reason as Example 2, practical multilayer glass ceramic substrate can not be obtained outside the proportions according to the present invention (12 to 59.6 wt% of alumina, 18 to 69.6 wt% of borosilicate magnesium glass and higher than 1 wt% of cordierite crystal). By the same reason as Example 2, if the content of magnesium in the borosilicate magnesium glass used becomes less than 5 wt% in term of magnesium oxide, no or little cordierite crystal is produced by sintering operation.

Claims: A multilayer glass ceramic substrate having a plurality of conductor layers and glass ceramic layer laminated on each other, each of said glass ceramic layers having a composition consisting of alumina, borosilicate magnesium glass and crystalline cordierite, characterized in that all said cordierite is in the form of crystals produced by chemical reaction between said alumina and said borosilicate magnesium glass, and that the content of alumina is 12 to 59.6 wt%, the content of borosilicate magnesium glass is 18 to 69.6 wt% and the content of reaction produced cordierite crystal is 1 to 50 wt%, the sum of components being 100wt%. A multilayer glass ceramic substrate having a plurality of conductor layers and glass ceramic layers laminated on each other, each said glass ceramic layer having a composition consisting of alumina, borosilicate magnesium glass, crystalline cordierite and a fourth component selected from quartzglass, α-quartz and mullite, characterized in that all said codierite is in the form of crystals produced by chemical reaction between said alumina and said borosilicate magnesium glass, and that the content of alumina is 12 to 59.6 wt%, the content of borosilicate magnesium glass is 18 to 69.6 wt%, the content of said forth component is 10 to 30 wt% and the content of reaction produced cordierite crystal is 1 to 50 wt%, the sum of components being 100 wt%. A process for producing a multilayer glass ceramic substrate by the steps of mixing material powders, preparing green sheets from slurry of the mixed material powders, forming via -holes in said green sheets, printing wiring conductors on said green sheets and filling said via -holes with conductor, laminating a plurality of such printed green sheets, compressing the laminated sheets under heat and then sintering the compressed sheets at a temperature below 1,000°C, characterized in that said material powders consist of 30 to 60 wt% of alumina powder and 70 to 40 wt% of borosilicate magnesium glass powder, and that said sintering is performed such that cordierite crystals are produced by chemical reaction between alumina and borosilicate magnesium glass. A process for producing a multilayer glass ceramic substrate by the steps of mixing material powders, preparing green sheets from slurry of the mixed material powders, forming via -holes in said green sheets, printing wiring conductors on said green sheets and filling said via -holes with conductor, laminating a plurality of such printed green sheets, compressing the laminated sheets under heat and then sintering the compressed sheets at a temperature below 1,000°C, characterized in that said mixed material powders consist of 10 to 50 wt% of alumina powder, 40 to 70 wt% of borosilicate magnesium glass powder and 10 to 50 wt% of third powder selected from quartzglass, α-quartz and mullite, the sum of all powders being 100 wt%, and that said sintering is performed such that cordierite crystals are produced by chemical reaction between alumina and borosilicate magnesium glass. The process set forth in claim 3 or 4 wherein alumina powder has an average particle size of 0.5 to 3 µm, borosilicate magnesium glass powder has an average particle of 1 to 5 µm. The process set forth in claim 4 wherein said third powder has an average paricle size of 0.5 to 10 µm. The process set forth in claim 3 or 4 wherein the content of magnesium in said borosilicate magnesium glass is more than 5 wt% in term of magnesium oxide.

Inventors: IKUINA KAZUHIRO, SHIMADA YUZO, IKUINA, KAZUHIRO, SHIMADA, YUZO
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1993
Main classification: C03C10
IPC codes: H01L23, C03C14, C03C17