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Patent US4626394 - Method of manufacturing low temperature sintered ceramic materials for use ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA ceramic composition capable of sintering at a sufficiently low temperature to enable the use of a low cost base metal as the electrode material in the fabrication of capacitors. The major ingredient of the composition is expressed as Bak-x Mx Ok TiO2, where M is at least either of magnesium and zinc...http://www.google.com/patents/US4626394?utm_source=gb-gplus-sharePatent US4626394 - Method of manufacturing low temperature sintered ceramic materials for use in solid dielectric capacitors or the likeAdvanced Patent SearchPublication numberUS4626394 APublication typeGrantApplication numberUS 06/753,240Publication dateDec 2, 1986Filing dateJul 9, 1985Priority dateNov 30, 1983Fee statusPaidAlso published asDE3475063D1, EP0155366A2, EP0155366A3, EP0155366B1, US4610969Publication number06753240, 753240, US 4626394 A, US 4626394A, US-A-4626394, US4626394 A, US4626394AInventorsTakeshi Wada, Hiroshi Nakamura, Masami Fukui, Nobutatsu YamaokaOriginal AssigneeTaiyo Yuden Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (11), Referenced by (2), Classifications (15), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetMethod of manufacturing low temperature sintered ceramic materials for use in solid dielectric capacitors or the like
US 4626394 AAbstract
A ceramic composition capable of sintering at a sufficiently low temperature to enable the use of a low cost base metal as the electrode material in the fabrication of capacitors. The major ingredient of the composition is expressed as Bak-x Mx Ok TiO2, where M is at least either of magnesium and zinc and where k and x are numerals in the ranges of 1.00 to 1.04 and of 0.02 to 0.05, respectively. To this major ingredient is added a minor proportion of a mixture of lithium oxide, silicon dioxide, and, possibly, at least one of barium oxide, calcium oxide, and strontium oxide. For the fabrication of coherently bonded bodies of this composition, as for use as the dilectric bodies of capacitors, the moldings of the mixture of the major ingredient and additive in finely divided form are sintered in a reductive or neutral atmosphere and then reheated at a lower temperature in an oxidative atmosphere. The sintering temperature can be so low (typically from 1050� to 1200� C.) that the moldings can be co-sintered with base metal electrodes buried therein without difficulties encountered heretofore.
1. A process for the fabrication of coherently bonded bodies of a low temperature sintered ceramic material, for particular use as the dielectric bodies of capacitors, which comprises:forming green bodies of desired shape and size from a mixture of 100 parts by weight of Bak-x Mx Ok TiO2 in finely divided form, where M is at least either of magnesium and zinc and where k is a numeral in the range of 1.00 to 1.04 and x a numeral in the range of 0.02 to 0.05, and 0.2 to 10.0 parts by weight of an additive in finely divided form consisting essentially of 25 to 50 mole percent lithium oxide and 50 to 75 mole percent silicon dioxide for providing upon firing coherently bonded dielectric bodies with a specific dielectric constant in excess of 2000, dielectric losses of less than 2.5 percent, resistivity of over 1�106 megohm-centimeters and capacitance temperature dependence of + or -10% in a temperature range of -25� to +85� C.; sintering the green bodies to maturity in a nonoxidative atmosphere at a temperature not to exceed 1300� C.; and reheating the sintered bodies in an oxidative atmosphere at a temperature lower than said preceding sintering temperature. 2. A process for the fabrication of coherently bonded bodies of a low temperature sintered ceramic material, for particular use as the dielectric bodies of capacitors, which comprises:forming green bodies of desired shape and size from a mixture of 100 parts by weight of Bak-x Mx Ok TiO2 in finely divided form, where M is at least either of magnesium and zinc and where k is a numeral in the range of 1.00 to 1.04 and x a numeral in the range of 0.02 to 0.05, and 0.2 to 10.0 parts by weight of an additive in finely divided form consisting essentially of lithium oxide and silicon dioxide and a metal oxide selected from the group consisting of barium oxide, calcium oxide, strontium oxide, and combinations thereof, wherein the range of the relative proportions of lithium oxide, silicon dioxide, and the selected metal oxide constituting the additive is in that region of the tenary diagram of FIG. 4 attached hereto which is bounded by the lines sequentially connecting:the point A where the additive consists of 5 mole percent lithium oxide, 70 mole percent silicon dioxide, and 25 mole percent metal oxide; the point B where the additive consists of 10 mole percent lithium oxide, 50 mole percent silicon dioxide, and 40 mole percent metal oxide; the point C where the additive consists of 49 mole percent lithium oxide, 50 mole percent silicon dioxide, and one mole percent metal oxide; and the point D where the additive consists of 24 mole percent lithium oxide, 75 mole percent silicon dioxide, and one mole percent metal oxide; for providing upon firing coherently bonded dielectric bodies with a specific dielectric constant in excess of 2000, dielectric losses of less than 2.5 percent, resistivity of over 1�106 megohm-centimeters and capacitance temperature dependence of + or -10% in a temperature range of -25� to +85� C.; sintering the green bodies to maturity in a nonoxidative atmosphere at a temperature not to exceed 1300� C.; and reheating the sintered bodies in an oxidative atmosphere at a temperature lower than said preceding sintering temperature. 3. A process for the fabrication of coherently bonded bodies of a low temperature sintered ceramic material as set forth in claim 5 or claim 7, wherein the bodies are sintered in a temperature range of 1050� to 1200� C.
This is a division of application Ser. No. 676,796, filed 11/30/84.
A solution to this problem is found in Sakabe et al. U.S. Pat. No. 4,115,493 issued Sept. 19, 1978. This patent proposes a method of making a monolithic ceramic capacitor with use of a base metal such as a nickel, iron or cobalt, or an alloy thereof, as the electrode material. According to this prior art method, a paste of a powdered base metal is screened on green dielectric sheets, and the pasted sheets are stacked, pressed together, and fired in a temperature range of 1300� to 1370� C. in a reductive atmosphere containing hydrogen. The oxidation of the pasted base metal particles is thus avoided.
Stated in brief, a low temperature sintered ceramic matrial in accordance with our invention consists essentially of 100 parts by weight of Bak-x Mx Ok TiO2, where M is at least either of magnesium (Mg) and zinc (Zn) and where k is a numeral in the range of 1.00 to 1.04 and x a numeral in the range of 0.02 to 0.05, and 0.2 to 10.0 parts by weight of an additive mixture of lithium oxide (Li2 O) and silicon dioxide (SiO2). The additive mixture may, or may not, additionally comprise at least one metal oxide (MO) selected from the group consisting of barium oxide (BaO), calcium oxide (CaO), and strontium oxide (SrO).
According to the method of our invention, for the fabrication of coherently bonded bodies of the above low temperature sintered ceramic material, there are first prepared the major ingredient, Bak-x Mx Ok TiO2 and the additive mixture of Li2 O and SiO2, with or without MO, in the above suggested proportions. After having been intimately mixed together, the major ingredient and additive are molded into bodies of desired shape and size. The moldings are subsequently sintered in a nonoxidative (i.e. neutral or reductive) atmosphere and then reheated in an oxidative atmosphere.
In addition to the advantages already set forth, our invention makes possible the provision of capacitors having specific dielectric constants of over 2000, dielectric losses of less than 2.5 percent, resistivity of over 1�106 megohm-centimeters, and temperature dependences of capacitance of plus or minus 10 percent in a temperature range of -25� to +85� C.
FIG. 4 is a ternary diagram depicting the proportions of some ingredients of the ceramic compositions in accordance with our invention.
We have illustrated in FIG. 1 one of many similar multilayered ceramic capacitor fabricated in various Examples of our invention by ay of a possible application of our invention, each capacitor having its dielectric body formulated in accordance with the composition and method of our invention. Generally designated by the reference numeral 10, the representative capacitor is shown to have an alternating arrangement of three dielectric ceramic layers 12 and two film electrodes 14. The dielectric layers 12 have, of course, the low temperature sintered ceramic material of our invention. The film electrodes 14, which can be of a low cost base metal such as nickel, extend into the middle of the dielectric body 15, composed of the three dielectric layers 12, from the opposite sides thereof into a partly opposed relation with each other. A pair of conductive terminations 16 contact the respective film electrodes 14. Each termination 16 comprises a baked on zinc layer 18, a plated on copper layer 20, and a plated on solder layer 22.
In this Example we fabricated 21 different sets of multilayered ceramic capacitors, each constructed as in FIG. 1, having their dielectric bodies 15 formulated in accordance with the compositions and firing temperatures set forth in Table 1. The major ingredient of the ceramic compositions in accordance with our invention has been expressed as Bak-x Mx Ok TiO2, where M is at least either of Mg and Zn. Accordingly, in Table 1, we have given the specific atomic numbers, as represented by k-x, x, and k, of the elements Ba, M (Mg and/or Zn), and O of the major ingredient, as well as the total atomic numbers of Mg and Zn. We employed a mixture of only Li2 O and SiO2 as an additive in this Example. Table 1 specifies the amounts, in parts by weight, of this additive with respect to 100 parts by weight of the major ingredient, and the relative proportions, in mole percent, of Li2 O and SiO2.
TABLE 1__________________________________________________________________________Ceramic CompositionsMajor Ingredient (100 wt. parts)               Additive         FiringTest    -x          Amount                     Composition (mole %)                                Temp.No.    -k -  -x  Mg Zn Total             -k               (wt. part)                     Li2 O                           SiO2                                (�C.)__________________________________________________________________________ 1 0.95  0.03     0.02        0.05            1.00               3.0   45    55   1110 2 0.97  -- 0.05        0.05            1.02               1.0   25    75   1160 3 0.98  0.05     -- 0.05            1.03               0.2   40    60   1180 4 0.95  0.02     0.01        0.03            0.98               1.0   30    70   1180 5 0.96  0.03     0.03        0.06            1.02               0.2   37    63   1180 6 0.97  0.02     0.02        0.04            1.01               1.0   20    80   1250 7 0.97  -- 0.04        0.04            1.01               1.0   43    57   1150 8 0.98  0.01     0.02        0.03            1.01               --    --    --   1250 9 0.98  0.02     0.01        0.03            1.01               0.2   50    50   117010 0.99  0.04     -- 0.04            1.03               1.0   37    63   115011 0.99  0.03     -- 0.03            1.02               3.0   35    65   112012 0.99  0.01     0.03        0.04            1.03               12.0  40    60   107013 0.99  0.01     0.01        0.02            1.01               7.0   32    68   107014 1.00  -- 0.03        0.03            1.03               10.0  48    52   107015 1.00  -- 0.02        0.02            1.02               5.0   28    72   112016 1.01  0.03     0.01        0.04            1.05               5.0   50    50   125017 1.01  0.02     -- 0.02            1.03               3.0   55    45   111018 1.01  0.02     -- 0.02            1.03               1.0   50    50   114019 1.01  -- 0.01        0.01            1.02               10.0  28    72   107020 1.02  -- 0.02        0.02            1.04               0.2   30    70   119021 1.02  0.01     -- 0.01            1.03               3.0   48    52   1110__________________________________________________________________________
Thus, according to Test No. 1 of Table 1, for instance, the major ingredient was Ba0.95 M0.05 O1.00 TiO2 or, more exactly, Ba0.95 Mg0.03 Zn0.02 O1.00 TiO2. One hundred parts by weight of this major ingredient was admixed with 3.0 parts by weight of a mixture of 45 mole percent Li2 O and 55 mole percent SiO2. The firing temperature (i.e. the temperature for sintering the molded bodies of the specified composition to maturity) of Test No. 1 was 1110� C.
For the fabrication of test capacitors of Test No. 1, we started with the preparation of the major ingredient, Ba0.95 Mg0.03 Zn0.02 O1.00 TiO2. We first prepared 903.77 grams of BaCO3, 5.86 grams of MgO, 7.88 grams of ZnO, and 385.93 grams of TiO2. Expressed in mole parts, with the impurities contained in the start materials disregarded, the relative proportions of the above prepared BaCO3, MgO, ZnO, and TiO2 were 0.95, 0.03, 0.02, and 1.00, respectively. These start materials were wet mixed together for 15 hours. Then the mixture was dried at 150� C. for four hours, pulverized, and calcined in air at about 1200� C. for two hours. The major ingredient was thus obtained in finely divided form.
We prepared the additive of Test No. 1 by first preparing a mixture of 50.15 grams (45 mole percent) of Li2 CO3 and 49.85 grams (55 mole percent) of SiO2. To this mixture was added 300 cubic centimeters of alcohol, and the resulting mixture was agitated for 10 hours in a polyethylene pot with alumina balls. Then the mixture was air fired at 1000� C. for two hours. Then, charged into an alumina pot together with 300 cubic centimeters of water, the mixture was crushed with alumina balls for 15 hours. Then the crushed mixture was dried at 150� C. for four hours. There was thus obtained the desired additive mixture of 45 mole percent Li2 O and 55 mole percent SiO2 in finely divided form.
Then 1000 grams of the above prepared major ingredient and 30 grams of the above prepared additive was mixed together. Further, to this mixture, we added 15 percent by weight (154.5 grams) of an organic binder and 50 percent by weight (515 cubic centimeters) of water with respect to the total amount of the major ingredient and the additive. The organic binder was an aqueous solution of acrylic ester polymer, glycerine, and condensed phosphate. All these were ball milled into a slurry. Then this slurry was defoamed in vacuum. Then the deformed slurry was introduced into a reverse roll coater thereby to be shaped into a thin, continuous strip on an elongate strip of polyester film. Then the continuous strip of the slurry was dried at 100� C. on the polyester film. The green (unsintered) ceramic strip thus obtained, about 25 microns thick, was subsequently cut into "squares" sized 10 by 10 centimeters.
For the fabrication of the base metal film electrodes 14, we prepared 10 grams of nickel in finely divided form, with an average particle size of 1.5 microns, and a solution of 0.9 gram of ethyl cellulose in 9.1 grams of butyl "Carbitol" (trademark for diethylene glycol monobutyl ether). Both were agitated for 10 hours to provide an electroconductive paste. Then this paste was "printed" on one surface of each green ceramic sheet, which had been prepared as above, through a screen having approximately 50 rectangular perforations sized 7 by 14 millimeters. Then, after drying the printed paste, two green ceramic sheets were stacked, with their printings directed upwardly, and with the printings on the two sheets offset from each other to an extent approximately one half of their longitudinal dimension. Further, four green ceramic sheets each with a thickness of 60 microns were stacked on each of the top and bottom surfaces of the two printed ceramic sheets. Then the stacked sheets were pressed in their thickness direction under a pressure of approxmately 40 tons at 50� C., thereby bonding the stacked sheets to one another. Then the bonded sheets were cut in a latticed pattern into approximately 100 pieces.
We employed a furnace capable of atmosphere control for co-firing the above prepared green dielectric bodies and what were to become film electrodes buried therein. The bodies were first air heated to 600� C. at a rate of 100� C. per hour, thereby driving off the organic binder that had been used for providing the slurry of the powdered major ingredient and additive. Then, with the furnace atmosphere changed from air to a reductive (nonoxidative) atmosphere consisting of two percent by volume of molecular hydrogen and 98 percent by volume of molecular nitrogen, the furnace temperature was raised from 600� C. to 1110� C. at a rate of 100� C. per hour. The maximum temperature of 1110� C., at which the ceramic bodies could be sintered to maturity, was maintained for three hours. Then the furnace temperature was lowered to 600� C. at a rate of 100� C. per hour. Then the furnace atmosphere was again changed to air (oxidative atmosphere), and the temperature of 600� C. was maintained for 30 minutes in that atmosphere for the oxidative heat treatment of the sintered bodies. Then the furnace temperature was allowed to lower to room temperature. There were thus obtained the dielectric ceramic bodies 15, FIG. 1, co-sintered with the film electrodes 14 buried therein.
We have so far described the method of fabricating multilayered ceramic capacitors in accordance with the composition of Test No. 1. As regards the other ceramic compositions of Table I, designated Tests Nos. 2 through 21, we manufactured similar multilayered ceramic capacitors through exactly the same procedure as that of Test No. 1 except for changes in the temperature of firing in the reductive (non-oxidative) atmosphere.
The multilayered ceramic capacitors of Tests Nos. 1 through 21 were then tested as to their specific dielectric constants, dielectric losses, resistivities, and percent changes in capacitances from thoese at +20� C. to those at -25� C. and +85� C. We measured these electrical properties of the test capacitors as follows:
Table 2 gives the results of the measurements by the above methods. It will be seen from this table that the specific dielectric constants of the Test No. 1 capacitors, for instance, averaged 2690, their dielectric losses 1.3 percent, their resistivities 7.4�106 megohm-centimeters, and their percent variations of capacitances from those at +20� C. to those at -25� and +85� C., -9.1 and -8.7 percent, respectively.
FIG. 2 graphically represents the average percent variations of the capacitances of the Test No. 1 capacitors at the above specified temperatures with respect to their capacitances at 20� C. It will be noted that the capacitance variations in the temperature range of -25� to -85� C. are all in the range of plus or minus 10 percent. This capacitance-temperature characteristic was typical of all the test capacitors of Example I; that is, if the percent variations of the capacitances of any groups of test capacitors at -25� and +85� C. were within plus or minus 10 percent, so were their capacitance variations at the other temperatures in between.
TABLE 2______________________________________Capacitor Characteristics                CapacitanceSpecific  Dielectric                    Resistivity                            VariationsTest Dielectric          Loss      (megohm-                            At     AtNo.  Constant  (%)       cm)     -25� C.                                   +85�  C.______________________________________ 1   2690      1.3       7.4 � 106                            -9.1   -8.7 2   2830      1.5       4.1 � 106                            -9.2   -7.2 3   2870      1.7       5.2 � 106                            -9.3   -9.5 4   3180      8.6       6.2 � 103                            -7.5   -3.8 5   2780      1.7       2.5 � 106                            -14.5  -10.5 6   Not coherently bonded on firing. 7   2980      1.4       3.8 � 106                            -7.2   -4.8 8   Not coherently bonded on firing. 9   3170      1.9       2.4 � 106                            -7.8   -4.510   2880      1.8       4.5 � 106                            -7.5   -7.411   2930      1.2       6.5 �  106                            -8.0   -5.612   2710      3.5       7.4 � 105                            -6.8   -8.713   2870      2.3       5.2 � 106                            -9.0   +3.514   2850      2.3       2.6 � 106                            -7.2   -4.215   2940      1.4       6.8 � 106                            -7.8   +2.416   Not coherently bonded on firing.17   2860      3.2       8.3 � 105                            -9.5   -1.318   3020      2.0       3.0 � 106                            -9.8   +1.619   2780      2.4       1.5 � 106                            -12.5  +6.820   3170      1.8       2.6 � 106                            -7.6   +0.821   2860      1.4       4.5 � 106                            -13.2  +2.3______________________________________
A reconsideration of Table 2 in light of the above established criteria of favorable capacitor characteristics will reveal that the capacitors of Tests Nos. 4, 5, 6, 8, 12, 16, 17, 19, and 21 do not meet these criteria. Accordingly, the corresponding ceramic compositions of Table 1 fall outside the scope of our invention.
Now, let us study the ceramic compositions of Table 1 and the corresponding capacitor characteristics of Table 2 in more detail. The ceramic composition of Test No. 8 contained no additive specified by our invention. The dielectric bodies formulated accordingly were not coherently bonded on firing at a temperature as high as 1250� C. Consider the ceramic composition of Test No. 9 for comparison. It contained 0.2 part by weight of the additive with respect to 100 parts by weight of the major ingredient. Even though the firing temperature was as low as 1170� C. the Test No. 9 capacitors possess the desired electrical characteristics. We set, therefore, the lower limit of the possible proportions of the additive at 0.2 part by weight with respect to 100 parts by weight of the major ingredient.
As regards the major ingredient, Bak-x Mx Ok TiO2, the value of x was set at 0.01 in Tests Nos. 19 and 20. In the resulting capacitors, the average variations of capacitances at -25� C. are -12.5 and -13.2 percent, both outside the desired range of plus or minus 10 percent. However, when the value of x was increased to 0.02, as in Test No. 18, then the desired electrical characteristics could be obtained. Thus the lowermost possible value of x is 0.02. The Test No. 5 composition had the value of x set at 0.06. In the resulting capacitors, the average variation of capacitance at -25� C. is -14.5 percent, which also is outside the desired range of plus or minus 10 percent. In Test Nos. 1, 2 and 3, the value of x was set slightly lower, at 0.05, and the resulting capacitors possess the desired electrical characteristics. The uppermost possible value of x is therefore 0.05.
The value of k in the formula of the major ingredient was set at 0.98 in Test No. 4, with the result that the average resistivity of the associated capacitors is 6.2�103 megohm-centimeters, much lower than the desired value. However, the desired value of resistivity was obtained when k was set at 1.00 as in Test No. 1. The lowermost possible value of k is therefore 1.00. On the other hand, when the value of k was increased to 1.05, as in Test No. 16, the resulting dielectric bodies were not coherently bonded on firing. As in Test No. 20, however, the desired electrical characteristics resulted when the value of k was set at 1.04. Accordingly, the uppermost possible value of k is 1.04.
Concerning the composition of the additive, the mixture of Li2 O and SiO2, it will be observed from Test No. 17 that when the proportion of SiO2 with respect to that of Li2 O was set at 45 mole percent, the average dielectric loss of the resulting capacitors is 3.2 percent, much higher than the desired value of 2.5 percent. The desired electrical characteristics were obtained, however, when the SiO2 proportion is 50 mole percent as in Tests Nos. 9 and 182. However, when the SiO2 proportion was increased to 80 mole percent as in Test No. 6, the dielectric bodies of the resulting composition were not coherently bonded on firing. The desired electrical characteristics were obtained when the SiO2 proportion was up to only 75 mole percent as in Test No. 2. We conclude from these findings that the acceptable range of the proportions of SiO2 is from 50 to 75 mole percent and, consequently, that the acceptable range of the proportions of Li2 O is from 25 to 50 mole percent.
TABLE 3__________________________________________________________________________Ceramic CompositionsMajor Ingredient (100 wt. parts)               AdditiveTest    -x          Amount                     Composition (mole %)                                MO (mole %)No.    -k -  -x  Mg Zn Total             -k               (wt. part)                     Li2 O                         SiO2                            MO  BaO                                   CaO                                      SrO__________________________________________________________________________22 1.01  0.01     0.01        0.02            1.03               0.2   20  70 10  20 80 --23 1.02  0.02     0.01        0.03            1.05               5.0   20  55 25  30 50 2024 1.01  0.01     -- 0.01            1.02               1.0   15  50 35  -- 75 2525 1.01  -- 0.01        0.01            1.02               10.0  25  65 10  15 15 7026 1.02  -- 0.02        0.02            1.04               0.2   15  55 30  70 -- 3027 1.00  0.02     -- 0.02            1.02               3.0    5  70 25  35 -- 6528 1.00  0.01     0.01        0.02            1.02               3.0    5  75 20  40 30 3029 1.00  0.03     -- 0.03            1.03               3.0   25  70  5  60 30 1030 1.00  0.01     0.03        0.04            1.04               5.0   35  50 15  30 15 5531 0.99  -- 0.03        0.03            1.02               12.0  45  50  5  10 80 1032 0.99  0.01     0.02        0.03            1.02               1.0   25  60 15  100                                   -- --33 0.99  0.01     0.02        0.03            1.02               1.0   25  60 15  -- 100                                      --34 0.99  0.01     0.02        0.03            1.02               1.0   25  60 15  -- -- 10035 0.99  0.01     0.02        0.03            1.02               1.0   30  50 20  40 30 3036 0.99  0.03     0.01        0.04            1.03               10.0  10  50 40  10 75 1537 0.99  0.04     0.01        0.05            1.04               1.0   30  60 10  40 20 4038 0.99  0.03     0.02        0.05            1.04               1.0   25  50 25  50  5 4539 0.98  0.01     0.01        0.02            1.00               7.0   40  55  5  45 50  540 0.98  0.03     0.01        0.04            1.02               3.0   15  80  5  40 30 3041 0.98  0.02     0.02        0.04            1.02               3.0   45  40 15  40 30 3042 0.98  0.01     0.03        0.04            1.02               --    --  -- --  -- -- --43 0.98  0.01     0.03        0.04            1.02               1.0   34  65  1  60 15 2544 0.98  0.04     -- 0.04            1.02               3.0   --  55 45  40 30 3045 0.97  0.02     0.01        0.03            1.00               0.2   24  75  1  15 30 5546 0.97  -- 0.04        0.04            1.01               1.0   10  65 25  25 65 1047 0.97  -- 0.05        0.05            1.02               3.0   25  70  5   5 70 2548 0.97  0.03     0.02        0.05            1.02               3.0   20  40 40  40 30 3049 0.97  0.02     0.03        0.05            1.02               1.0   15  70 15  30 25 4550 0.97  0.01     0.04        0.05            1.02               10.0  25  55 20  45 45 1051 0.97  0.03     0.03        0.06            1.02               1.0   10  55 35  10 10 8052 0.96  0.01     0.03        0.04            1.00               1.0   10  70 20  65 35 --53 0.96  0.04     0.01        0.05            1.01               1.0   10  60 30  25  5 7054 0.96  0.01     0.04        0.05            1.01               1.0   20  65 15  -- 65 3555 0.95  0.05     -- 0.05            1.00               0.2   39  60  1  55 20 2556 0.95  0.02     0.03        0.05            1.00               1.0   49  50  1  45 20 3557 0.94  0.02     0.02        0.04            0.98               5.0   15  65 20  70 20 10__________________________________________________________________________
TABLE 4__________________________________________________________________________Firing conditions &amp; Capacitor Characteristics       Capacitor CharacteristicsFiring Conditions       Specific             DielectricTest   H2 Propn   Temp.       Dielectric             Loss  Resistivity                          Capacitance Variations (%)No.   (%)  (�C.)       Constant             (%)   (megohm-cm)                          At -25� C.                                 At +85� C.__________________________________________________________________________22 2.0  1190       3160  1.3   2.5 � 106                          -9.6   +1.623 2.0  1250       Not coherently bonded on firing.24 2.0  1160       2970  1.0   4.2 � 106                          -13.5  +7.825 2.0  1070       2750  0.9   4.5 � 106                          -11.2  +9.626 2.0  1190       3170  1.2   2.6 � 106                          -9.7   +2.827 2.0  1130       2890  0.7   7.8 � 106                          -9.2   -1.528 2.0  1250       Not coherently bonded on firing.29 0.0  1130       2930   0.7  7.5 � 106                          -7.5   -3.630 0.0  1100       2850  1.1   5.4 � 106                          -7.2   -5.231 2.0  1070       2750  2.9   6.8 � 105                          -8.1   -7.532 2.0  1150       3010  1.2   3.1 � 106                          -8.2   -2.533 2.0  1150       3020  1.1   3.4 � 106                          -8.5   -2.134 2.0  1150       3000  0.9   3.7 � 106                          -8.0   -2.835 2.0  1150       3020  1.0   3.5 � 106                          -8.3   -2.436 2.0  1080       2670  2.4   2.5 � 106                          -9.6   -9.737 2.0  1150       2780  1.3   3.8 � 106                          -9.3   -9.538 5.0  1150       2810  1.2   3.6 � 106                          -9.2   -9.339 5.0  1060       2850  1.5   4.3 � 106                          -9.3   -1.740 2.0  1250       Not coherently bonded on firing.41 2.0  1250       Not coherently bonded on firing.42 2.0  1250       Not coherently bonded on firing.43 2.0  1150       2950  1.8   3.8 �  106                          -7.5   -4.844 2.0  1250       Not coherently bonded in firing.45 5.0  1190       3180  1.9   2.4 � 106                          -8.0   -3.546 5.0  1160       2970  1.1   4.2 � 106                          -7.4   -4.947 5.0  1130       2740  0.8   6.8 � 106                          -9.2   -7.448 2.0  1250        Not coherently bonded on firing.49 2.0  1160       2800  1.2   3.1 � 106                          -9.4   -8.550 2.0  1070       2590  2.3   1.8 � 106                          -9.7   -8.751 2.0  1160       2670  1.4   1.5 � 106                          -13.2  -10.552 5.0  1160       2930  0.9   4.2 � 106                          -7.4   -5.553 5.0  1160       2750  1.0   4.1 � 106                          -9.5   -9.154 2.0  1150       2800  1.1   3.7 � 106                          -9.3   -7.855 2.0  1170       2860  1.4   7.2 � 106                          -9.8   -9.356 2.0  1140       2810  1.2   3.6 � 106                          -9.6   -9.257 2.0  1110       2820  7.6   2.8 � 103                          -7.2   -6.3__________________________________________________________________________
The Test No. 42 composition contained no additive, and the resulting dielectric bodies were not coherently bonded on firing at a temperature as high as 1250� C. However, when 0.2 part by weight of the additive (mixture of Li2 O, SiO2, BaO, and CaO) was added to 100 parts by weight of the major ingredient, as in Test No. 22, the capacitors of the desired electrical characteristics could be obtained by firing at a lower temperature of 1190� C. The lower limit of the possible proportions of the additive is thus set at 0.2 part by weight with respect to 100 parts by weight of the major ingredient even when the additive contains MO, just as when it does not. When as much as 10 parts by weight of the additive (mixture of Li2 O, SiO2, BaO, CaO, and SrO) was added to 100 parts by weight of the major ingredient, as in Test No. 23, the resulting capacitors had the average dielectric loss of as much as 2.9 percent. Capacitors of the desired characteristics could be obtained when the proportion of the additive was reduced to 10 parts by weight, as in Test No. 36. The upper limit of the possible proportions of the additive (including MO) is, therefore, also 10 parts by weight with respect to 100 parts by weight of the major ingredient, just as in cases where the additive contains no MO.
As for the major ingredient, Bak-x Mx Ox TiO2, the value of x was set at 0.01 in Tests Nos. 24 and 25. The resulting percent variations of capacitances at -25� C. from those at +20� C. were -13.5 and -11.2 percent, both outside the desired range of plus or minus 10 percent. The desired electrical characteristics resulted, however, when the value of x was set at 0.02 as in Test No. 26. Thus the lowermost possible value of x is 0.02, just as in cases where the additive contains no MO. When the value of x was set at as high as 0.06 as in Test No. 51, the resulting percent variations of capacitance at -25� C. and +85� C. were -13.2 and -10.5 percent, respectively. The desired electrical characteristics could be obtained only when the value of x was reduced to 0.05 as in Tests Nos. 53 through 56. The highest possible value of x is therefore 0.05, just as in cases where the additive contains no MO.
The value of k in the formula of the major ingredient was set at 0.98 in Test No. 57. The average resistivity of the resulting capacitors became as low as 2.8�103 megohm-centimeters. The desired electrical characteristics could be obtained when the value of k was set at 1.00 as in Tests Nos. 55 and 56. The lowest possible value of k is therefore 1.00, just as in cases where the additive contains no MO. On the other hand, when the value of k was set at as high as 1.05 as in Test No. 23, the resulting dielectric bodies were not coherently bonded on firing. The desired electrical characteristics could be obtained when the value of k was reduced to 1.04 as in Test No. 30. Thus the highest possible value of k is 1.04, just as in cases where the additive contains no MO.
We have ascertained from the results of Table 4 that, when the additive mixture contains MO (one or more of BaO, CaO, and SrO), the acceptable relative proportions of Li2 O, SiO2, and MO can be determined in accordance with the indications of the ternary diagram of FIG. 4. The point A in this diagram indicates the Test No. 27 additive composition of 5 mole percent Li2 O, 70 mole percent SiO2, and 25 mole percent MO. The point B indicates the Test No. 36 additive composition of 10 mole percent Li2 O, 50 mole percent SiO2, and 40 mole percent MO. The point C indicates the Test No. 56 additive composition of 49 mole percent Li2 O, 50 mole percent SiO2, and one mole percent MO. The point D indicates the Test No. 45 additive composition of 24 mole percent Li2 O, 75 mole percent SiO2, and one mole percent MO. The relative proportions of the additive mixture of Li2 O, SiO2, and MO in accordance with our invention all fall within the region bounded by the lines sequentially connecting the above points A, B, C and D.
Table 4 proves that the additive compositions within this region makes possible the provision of capacitors of the desired electrical characteristics. The additive compositions of Tests Nos. 28, 40, 41, 44, and 48 are all outside that region, and the corresponding dielectric bodies were not coherently bonded on firing. The above specified recommended range of the relative proportions of the additive mixture holds true regardless of whether only one of BaO, CaO, and SrO is employed as MO, as in Tests Nos. 32, 33 and 34, or two or all of them are employed in suitable proportions as in the other tests.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4101952 *Aug 17, 1976Jul 18, 1978Sprague Electric CompanyMonolithic base-metal glass-ceramic capacitorUS4106075 *Mar 17, 1976Aug 8, 1978Draloric Electronic GmbhCeramic capacitorUS4115493 *Aug 19, 1977Sep 19, 1978Murata Manufacturing Co., Ltd.Method for making a monolithic ceramic capacitor employing a non-reducing dielectric ceramic compositionUS4223369 *Jul 3, 1978Sep 16, 1980Sprague Electric CompanyMonolithic capacitor with low firing zirconate and nickel electrodesUS4283753 *Sep 28, 1979Aug 11, 1981Sprague Electric CompanyLow firing monolithic ceramic capacitor with high dielectric constantUS4308570 *Feb 25, 1980Dec 29, 1981Sprague Electric CompanyHigh Q monolithic capacitor with glass-magnesium titanate bodyUS4386985 *Jun 18, 1981Jun 7, 1983North American Philips CorporationMethod of making ceramic dielectric for base metal electrode capacitorsUS4451869 *May 5, 1983May 29, 1984Murata Manufacturing Co., Ltd.Laminated ceramic capacitorUS4477401 *Sep 2, 1982Oct 16, 1984U.S. Philips CorporationMethod of manufacturing a dielectricUS4568650 *Jan 17, 1984Feb 4, 1986The United States Of America As Represented By The Secretary Of The NavyOxidation of reduced ceramic productsUS4571276 *Jun 22, 1984Feb 18, 1986North American Philips CorporationMethod for strengthening terminations on reduction fired multilayer capacitors* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS5217754 *Oct 23, 1990Jun 8, 1993Trustees Of The University Of PennsylvaniaOrganometallic precursors in conjunction with rapid thermal annealing for synthesis of thin film ceramicsEP0312923A1 *Oct 14, 1988Apr 26, 1989Tam Ceramics, Inc.Low-firing dielectric composition* Cited by examinerClassifications U.S. Classification264/620, 264/662, 264/82, 361/320, 361/321.4International ClassificationC04B35/468, H01G4/12, H01G4/232, C04B35/00Cooperative ClassificationC04B35/4682, H01G4/2325, H01G4/1227European ClassificationC04B35/468B, H01G4/12B2B, H01G4/232BLegal EventsDateCodeEventDescriptionMay 21, 1998FPAYFee paymentYear of fee payment: 12May 16, 1994FPAYFee paymentYear of fee payment: 8Mar 12, 1990FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services