Joining material for electronic components, electronic components and a method for manufacturing the same

Abstract: A joining material for an electronic component was disclosed. The component has a plurality of functional layers, each selected from a magnetic layer and dielectric layer and joined with each other. The joining material comprising a glass and a composition of a mol% of ZnO, b mol% of BaO and c mol% of TiO 2 (a=12-45, b=4-45, c=18-81, a+b+c=100 ), wherein 0.1 to 10 weight parts of the glass is added to 100 weight parts of the composition.

Description: Background of the Invention 1. Technical Field The invention relates to a joining material for an electronic component, such as capacitor, inductors, resistors, stacked type and coaxial type dielectric filters, Stacked type LC filters, composite LC components and composite LCR modules, an electronic component and a method for manufacturing the same. 2. Related Arts When manufacturing a stacked type dielectric filter, a paste for an internal layer electrode is printed on each of a predetermined number of greensheets, which are then laminated to produce laminated greensheets. This laminated greensheets are then sintered at a temperature of 700°C to 1100°C to produce a base body with the internal layer electrodes. After the base body is polished, a metal paste for an outer electrode is printed on predetermined regions on the surface of the body and fired to form the outer electrodes. A composite LC filter with an inductor and capacitor is also known. When producing such composite electronic components, a predetermined number of greensheets for, for example, a dielectric layer and magnetic layer are laminated to provide laminated greensheets, which are then co-fired to join the magnetic and dielectric layers. It is also known to provide a greensheet of a joining layer between the greensheets of the magnetic and dielectric layers to provide laminated greensheets which are then co-fired. In Japanese publication Tokkohei 120605/1995, a ceramic material, obtained by firing a mixture of ZnO, TiO 2 and CuO, is used for the joining layer for preventing the peeling between the dielectric layers and magnetic layers and diffusion of the ingredients of both layers with each other. In Japanese patent application publication Tokkaihei 36913/1997, a ceramic material is provided between the dielectric and magnetic layers for improving the adhesive strength of the layers and for preventing diffusion of the ingredients of both layers with each other, the ceramic material being obtained by mixing a glass contained in the dielectric layer with a ceramic of 15 to 40 mol% of BaO and 60 to 85 mol% of TiO 2 and firing. Summary of the Invention However, according to the inventor's research, warp may occur in the magnetic or dielectric layer depending on the compositions of both layers and their firing schedule. When the amount of warp is out of the specification for manufacturing a filter, such filter with impermissible warp is discarded as a defective, thus decreasing its manufacturing yield. The inventors further found that warp was also induced in the layers during sintering process. The object of the invention is, in an electronic component having a plurality of functional layers each selected from a magnetic layer and dielectric layer and joined with each other, to prevent warp in the magnetic layers or the dielectric layer. The invention provides a joining material for an electronic component as indicated in appended claim 1. The invention also provides an electronic component having the functional layers and a joining layer for joining the adjacent functional layers, wherein the joining layer is composed of sintered product of a joining material according to claims 1 to 3. That is, a layer composed of the joining material is fired to form the joining layer. The joining layer is made of the sintered product obtained by firing the joining material. The invention also provides an electronic component having the functional layers and a joining layer, wherein the joining layer is composed of sintered product showing at least one of a peak corresponding to BaNd 2 Ti 5 O 14 and a peak corresponding to BaNd 2 Ti 4 O 12 when measured by means of powdery X-ray diffraction method. The invention also provides a method for manufacturing an electronic component having the functional layers and a joining layer. A method for manufacturing an electronic component according to the present invention is described in appended claims 5, 6 and 7. The inventors researched the above described warp of a dielectric layer or magnetic layer and finally made the following discovery. According to state-of-the-art knowledge, it is possible to improve the adhesive strength and therefore to prevent the peeling of the magnetic and dielectric layers, by adjusting the thermal expansion coefficient of joining ceramics between the magnetic and dielectric layers to those of both layers. However, in actual manufacturing process, depending on the selection of materials for the magnetic and dielectric layers and sintering schedule, even when the thermal coefficient of the joining ceramics is adjusted to those of the magnetic and dielectric layers, warp may be observed during the sintering process. This phenomenon probably means that the magnetic, dielectric and joining layers shrink at different firing shrinkage rates at certain or even almost any time point during the sintering. The inventors, based on the above discovery, successfully provide a solution. That is, the above warp may be considerably decreased or even prevented, on a wide variety of materials for magnetic and dielectric layers, by providing a joining material of each of the above specific compositions. In the above compositions, for further reducing the warp of the magnetic or dielectric layer, a content of ZnO (a mol%) may preferably be 25 to 40 mol%, a content of BaO (b mol%) may preferably be 5 to 15 mol%, and a content of TiO 2 (c mol%) may preferably be 45 to 65 mol%. A glass contained in the inventive joining material may preferably be selected from a group consisting of ZnO-SiO 2 -B 2 O 3 glass, PbO-B 2 O 3 -SiO 2 glass, Al 2 O 3 -CaO-B 2 O 3 -SiO 2 glass, B 2 O 3 -SiO 2 glass, MgO-Al 2 O 3 -SiO 2 cordierite glass, and ZnO-MgO-Al 2 O 3 -SiO 2 cordierite glass, and most preferably be ZnO-SiO 2 -B 2 O 3 glass. These glasses may further contain TiO 2 , ZrO 2 or Y 2 O 3 . The greensheets for the inventive joining layer may be made brown, by adding not more than 10 mol% of MnO to the inventive joining material, to distinguish the brown-colored greensheet from greensheets for magnetic and dielectric layers. The joining layer may also be colored by adding at least one metal oxide selected from a group consisting of Cr 2 O 3 , Fe 2 O 3 and NiO. Not more than 10 mol% of Al 2 O 3 may be added to the inventive joining material to further improve the adhesive strength of functional layers. Not more than 10 mol% of at least one metal oxide selected form a group consisting of Y 2 O 3 and ZrO 2 may be also added to the inventive joining material to further improve the adhesive strength of adjacent functional layers. More than 10 mol% of MnO added to the joining material might reduce the adhesive strength between the functional layers. More than 10 mol% of Al 2 O 3 added to the joining material might increase the warp of functional layers. In the invention, at least one of the functional layers functions as an element in an equivalent circuit, and therefore functions as an electronic device layer. Such electronic device layer includes inductor, capacitor and resistor layers. The inductor layer may preferably comprises a magnetic layer and an inductor, such as a coil, as a conductor embedded within the magnetic layer. The capacitor layer may preferably comprises a dielectric layer and a capacitor as a conductor embedded within the dielectric layer. The magnetic layer means a layer made of a magnetic material, in the invention. The invention is particularly suitable for a composite electronic component, preferably being an LC filter, stacked type dielectric filter or an LCR integrated substrate. The dielectric layer may be preferably made of a TiO 2 , TiO 2 CaO, BaO-TiO 2 , BaO-TiO 2 -Nd 2 O 3 , BaO-TiO 2 -Nd 2 O 3 -Bi 2 O 3 , BaO TiO 2 -ZnO, BaO-Al 2 O 3 -SiO 2 , MgO-CaO-TiO 2 , BaO-MgO-Ta 2 O 5 or Al 2 O 3 series oxide. Such oxide may include a glass, which is preferably selected from B 2 O 3 -SiO 2 , CaO-B 2 O 3 -SiO 2 , CaO-Al 2 O 3 -B 2 O 3 -SiO 2 and CaO-Al 2 O 3 -TiO 2 -SiO 2 series glasses. The magnetic layer may preferably be made of a Fe 2 O 3 -NiO-CuO-ZnO,Fe 2 O 3 -NiO-CuO-ZnO-SiO 2 , NiO-ZnO, or CuO-ZnO or feroux planar series oxide. These magnetic material may contain not more than 5 weight percent of CoO or MnO, and about 1 weight percent of SiO, CaO, PbO, or Bi 2 O 3 constituting a glass. When applying these materials, warp may be induced more often, thus increasing the need for the invention. When the joining layer has a thickness of not smaller than 10µm, an amount of warp may be considerably reduced and the tensile strength thereof may be improved. The upper limit of the thickness is not particularly mentioned, however, the layer with a thickness of not larger than 500 µm is practical. Brief description of the Drawings Figure 1 is a view schematically showing an LC filter suitable for applying the invention, Figure 2 is a perspective view showing greensheets needed for manufacturing the filter of Figure 1, Figure 3 is a view schematically showing a stacked type dielectric filter suitable for applying the invention, Figure 4 is a perspective view showing greensheets needed for manufacturing the filter of Figure 3, Figure 5 is a view schematically showing a stacked type LCR filter suitable for applying the invention, Figure 6 is a perspective view showing greensheets needed for manufacturing the filter of Figure 5, Figure 7 is a photograph showing a polished surface of the filter sintered according to experimental number 16 within the invention, and Figure 8 is a photograph showing a polished surface of the filter sintered according to control experimental number 19 outside of the invention. Figure 1 is a view schematically showing an LC filter, and Figure 2 is a perspective view needed for manufacturing an LC filter of Figure 1. As shown in Figure 2, greensheets 7A, 7B, 7C, 7D, 7E, 7F, 7G, 7H and 7I for an inductor layer, a greensheet 8 for a joining layer, and greensheets 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I and 9J for a capacitor layer are laminated. 13A for conductor paste are printed on the greensheets 7B to 7H for inductor layers, according to a coil pattern designed by a lumped parameter circuit. 14A for conductor paste are printed on the greensheets for a capacitor layer, according to a capacitor pattern designed by a lumped parameter circuit. These greensheets are laminated and heat-pressed to provide laminated greensheets, which are then cut into a predetermined shape to provide a cut body. The cut body is sintered at a temperature of 800 to 950°C and further subjected to barrel polishing. Paste for an outer electrode is printed on the surface of the sintered body according to a predetermined pattern, dried and then fired at a temperature of 500 to 850°C to provide an LC filter shown in Figure 1. The thus obtained LC filter comprises an inductor layer 2A, a joining layer 4A and a capacitor layer 5A. 3A is a coil pattern and 6A is a capacitor pattern. Figure 3 is a view schematically showing a stacked type dielectric filter, and Figure 4 is a perspective view showing greensheets needed for manufacturing the filter of Figure 3. As shown in Figure 4, greensheets 15A and 15B for register layers, a greensheet 8 for a joining layer and greensheets 9A to 9R for a capacitor layer are laminated. 16A for conductor paste are printed on the greensheet 15A, according to an electrode pattern designed for connection with an outer mounting part or inner conductors. 16A for resistor paste are printed on the greensheet 15B, according to a connecting-electrode pattern designed by a distributed constant circuit, or lamped parameter circuit, or the combination thereof. Capacitor patterns 14B, designed by a distributed constant circuit, or lamped parameter circuit, or the combination thereof, are printed on the greensheets 9B, 9C, 9D, 9E and 9F for a capacitor layer. These greensheets are laminated and heat-pressed to provide laminated greensheets, which are then cut into a predetermined shape to provide a cut body. The cut body is sintered at a temperature of 700 to 1100°C and further subjected to barrel polishing. Paste for an outer electrode is printed on the surface of the sintered body according to a desired pattern, dried and then fired at a temperature of 500 to 900°C to provide a filter 10 shown in Figure 5. The thus obtained filter comprises a resistor layer 11A, a joining layer 4B and a capacitor layer 5B. 12 is a connecting electrode pattern and 6B is a capacitor pattern. Figure 5 is a view schematically showing a stacked type LCR filter, and Figure 6 is a perspective view showing greensheets needed for manufacturing the filter of Figure 5. As shown in Figure 6, greensheets 15C and 15D for register layers, a greensheet 8 for a joining layer, greensheets 7J, 7K, 7L, 7M, 7N, 70, 7P, 7Q, 7R and 7S for an inductor layer, another greensheet 8, and greensheets 9S, 9T, 9U, 9V, 9X and 9Y for a capacitor layer are laminated. 16B for conductor paste are printed on the outer greensheet 15C, according to an electrode pattern designed for connection with a surface mount part or inner conductors. Paste regions for electrodes are printed on the greensheet 15D, according to a coil pattern designed by a distributed constant circuit, or lamped parameter circuit, or the combination thereof. Paste regions for electrodes are printed on the greensheets 7L to 7Q for an inductor layer, according to an inductor pattern designed by a distributed constant circuit, or lamped parameter circuit, or the combination thereof. Paste regions for electrodes are printed on the greensheets 9U, 9V, 9W and 9X for a capacitor layer, according to a capacitor pattern designed by a distributed constant circuit, or lumped parameter circuit, or the combination thereof. These greensheets are laminated and heat-pressed to provide a laminated greensheets, which are then cut into a predetermined shape to provide a cut body. The cut body is sintered at a temperature of 700 to 1100°C and further subjected to barrel polishing. Paste for an outer electrode is printed on the surface of the sintered body according to a desired pattern, dried and then fired at a temperature of 700 to 1100°C to provide an LCR filter 20 shown in Figure 5. The thus obtained filter comprises a resistor layer 11B, joining layers 4A and 4B, an inductor layer 2B and a capacitor layer 5C. 12 is a connecting-electrode pattern and 3B is a coil pattern. (Experiment A) Greensheets shown in Figure 2 were prepared. For greensheets for an inductor layer, nickel oxide, zinc oxide, copper oxide and ferrous oxide were weighed to a predetermined composition, mixed and calcined to provide a calcined body, which was then granulated to ceramic powder. To the ceramic powder, an organic binder, a plasticizer, a dispersing material and solvents, such as xylene and butanol, were added, blended and shaped by means of doctor blade method to provide greensheets with a thicknesses of 30 to 200 µm. Paste mainly consisting of silver was printed on some of the greensheets. Zinc oxide, barium oxide and titanium oxide were weighed to a predetermined composition as shown in tables 1 and 2, mixed and calcined to provide a calcined body, which was then granulated to ceramic powder. To the ceramic powder, ZnO-SiO 2 -B 2 O 3 series glass powder already granulated was added (the content was varied as shown in tables 1 and 2), and an organic binder, a plasticizer, a dispersing material and solvents, such as xylene and butanol, were further added, blended and shaped by means of doctor blade method to provide a greensheet 8 with a thickness of 10 to 1000 µm. Titanium oxide and calcium oxide were weighed to a predetermined composition, mixed and calcined to provide a calcined body, which was then granulated to ceramic powder. To the ceramic powder, ZnO-SiO 2 -B 2 O 3 series glass powder already granulated was added, and an organic binder, a plasticizer, a dispersing material and solvents, such as xylene and butanol, were further added, blended and shaped by means of doctor blade method to provide greensheets for a capacitor layer with thicknesses of 10 to 1000 µm. Paste mainly consisting of silver was printed on some of the greensheets. These greensheets were laminated, heat-pressed and cut into a predetermined shape to provide a cut body, which was then sintered at a temperature of not higher than 1100°C. Paste mainly consisting of silver was printed on the thus obtained sintered body according to an outer electrode pattern and fired to provide an LC filter. The color of each greensheet for a joining layer 8 was observed with eyes. Further, the thus obtained LC filter was embedded within a resin body and polished with the surrounding resin. The amount of warp of each filter was measured with an automated dimension measuring apparatus. The specification for the amount of warp of each sintered filter was not larger than 30 µm. The thickness of the joining layer 4A was also measured on each filter. Aluminum rods, for measuring an adhesive strength, were adhered and fixed on the surfaces of the magnetic and dielectric layers, respectively, to provide a sample. The aluminum rods of each sample were fixed in a tensile strength measuring apparatus to measure its tensile strength. The adhesive strength was defined as a value at the moment of fracture. These experimental results were shown in tables 1 and 2. As can be seen from the results, when adjusting a content of zinc oxide to 12 to 45 mol%, a content of barium oxide to 4 to 45 mol%, a content of TiO 2 to 18 to 81 mol% and a content of ZnO-SiO 2 -B 2 O 3 series glass to 0.5 to 10 weight parts, the amount of warp was considerably decreased to not high than 30 µm. X-ray diffraction curve was measured on each sample of experimental numbers of 2, 3, 4, 7, 8, 9, 12, 13, 14, 16, 17 and 18 shown in tables 1 and 2. Consequently, either of or both peaks corresponding to BaNd 2 Ti 5 O 14 and BaNd 2 Ti 4 O 12 was found. Then, when the above cut bodies of experimental numbers 16 and 19 before the sintering were subjected to the sintering, each body's appearance was observed by means of a heating microscope to take a photograph showing the dielectric layer, magnetic layer and joining layer. In the filter of the number 16 fallen within the invention, the amount of warp of each functional layer was up to 30 µm. On the contrary, in the filter of the control experimental number 19, the amount of warp of the whole filter was more than 1000 µm. (Experiment B) LC filters were produced as described in the experiment A, however, manganese oxide or alumina was added to a greensheet for a joining layer. The composition of the greensheet was changed as shown in Figure 3, which also shows the experimental results. Consequently, same as the experiment A, when adjusting a content of zinc oxide to 12 to 45 mol%, a content of barium oxide to 4 to 45 mol%, a content of TiO 2 to 18 to 81 mol% and a content of ZnO-SiO 2 -B 2 O 3 series glass to 0.1 to 10 weight parts, the amount of warp of each filter was decreased to not higher than 80 µm during the sintering, and to not higher than 30 µm after the sintering. Further, the greensheet was colored brown by adding MnO. However, when MnO was added in an amount of more than 10 mol%, the adhesive strength was lowered. Although the addition of alumina increased considerably the adhesive strength, when alumina was added in an amount of more than 10 mol%, the amount of warp of the filter after the sintering was more than 70 µm. (Experiment C) LC filters were manufactured as described in the experiment A, however, the compositions of the greensheets for joining layers were changed as shown in table 4, showing the experimental results. Consequently, same as the experiment A, when adjusting contents of zinc oxide, barium oxide, titanium oxide, manganese oxide and alumina according to the invention and a content of ZnO-SiO 2 -B 2 O 3 series glass to 0.1 to 10 weight parts, the amount of warp of each filter was considerably decreased during the sintering. When the amount of the glass was out of a range of 0.1 to 10 weight parts, the amount of warp was more than 70 µm. (Experiment D) LC filters were manufactured as described in the experiment A, however, the compositions of the greensheets for joining layers were adjusted in the preferred range of the invention and thicknesses of the joining layers were changed. The results were shown in table 5. Consequently, same as the experiment A, the amount of warp of each filter was considerably decreased according to the invention. Further, when the thickness of the joining layer was adjusted to not smaller than 30 µm, the amount of warp was considerably lowered and the adhesive strength was considerably improved. (Experiment E) Greensheets shown in Figure 4 were prepared. In greensheets for a resistor layer, alumina powder and almino-calcium borosilicate glass were mixed with an organic binder, a plasticizer, a dispersing material and solvents such as xylene and butanol, blended and then shaped by means of doctor blade method to provide greensheets with thicknesses of 0.01 to 1.0 µm. Paste mainly consisting of silver was printed on some of the greensheets. 33 mol% of Zinc oxide, 12 mol% of barium oxide and 55 mol% of titanium oxide were weighed, mixed and calcined to provide a calcined body, which was then granulated to ceramic powder. To the ceramic powder, 2 weight parts of ZnO-SiO 2 -B 2 O 3 series glass powder already granulated was added, and an organic binder, a plasticizer, a dispersing material and solvents, such as xylene and butanol, were further added, blended and shaped by means of doctor blade method to provide a greensheet 8 with a thickness of 10 to 1000 µm, Barium oxide, titanium oxide, neodymium oxide and bismuth oxide were weighed, mixed and calcined to provide a calcined body, which was then granulated to ceramic powder. To the ceramic powder, an organic binder, a plasticizer, a dispersing material and solvents, such as xylene and butanol, were further added, blended and shaped by means of doctor blade method to provide greensheets for a capacitor layer with thicknesses of 10 to 500 µm. Paste mainly consisting of silver was printed on some of the greensheets. These greensheets were laminated and heat-pressed to provide a laminated body, which was then cut into a cut body with a predetermined shape. The cut body was sintered at a temperature of not higher than 1100°C to obtain a stacked type dielectric filter, whose amount of warp was found to be not larger than 30 µm. (Experiment F) Greensheets as shown in Figure 6 were prepared. Greensheets for resistor, joining and capacitor layers were manufactured as described in the experiment E. Greensheets for an inductor layer were also manufactured, as described in the experiment A. These greensheets were laminated and heat-pressed to provide a laminated body, which was then cut into a cut body with a predetermined shape. The cut body was then sintered at a temperature not higher than 1100°C to obtain an LCR filter, whose amount of warp was found to be not large than 30 µm.

Claims: A joining material for an electronic component, the component having a plurality of functional layers to be joined with each other by the joining material and each selected from a magnetic layer and dielectric layer, the joining material comprising (i) a glass and (ii) a composition which consists of, in mol %:- ZnO a BaO b TiO 2 c optionally, MnO d optionally, Al 2 O 3 e where a+b+c+d+e = 100 12 ≤ a ≤ 45 4 ≤ b ≤ 45 18 ≤ c ≤ 81 d ≤ 10 e ≤ 10, said composition further comprising (I) optionally, not more than 10 mol % in total of at least one of Cr 2 O 3 , Fe 2 O 3 and NiO, (II) optionally, not more than 10 mol % in total of at least one of Y 2 O 3 and ZrO 2 . The joining material as claimed in claim 1, wherein the content of ZnO is 25 to 40 mol %, the content of BaO is 5 to 15 mol % and the content of TiO 2 is 45 to 65 mol %. The joining material as claimed in claim 1 or 2, wherein the glass is selected from ZnO-SiO 2 -B 2 O 3 glass, PbO-B 2 O 3 -SiO 2 glass, Al 2 O 3 -CaO-B 2 O 3 -SiO 2 glass, B 2 O 3 -SiO 2 glass, MgO-Al 2 O 3 -SiO 2 cordierite glass, and ZnO-MgO-Al 2 O 3 -SiO 2 cordierite glass. An electronic component having a plurality of functional layers each selected from a magnetic layer and dielectric layer and a joining layer joining said layers to each other, wherein the joining layer is composed of sintered product of the joining material as claimed in any one of claims 1 to 3. The electronic component as claimed in claim 4, wherein the joining layer has a thickness of not smaller than 10µm and not larger than 500µm. A method for manufacturing an electronic component having a plurality of functional layers each selected from a magnetic layer and dielectric layer comprising the steps of: laminating said functional layers in sintered form to provide a laminated body having also a layer made of the joining material as claimed in any one of claims 1 to 3 provided between the functional layers, and firing the joining material to form the joining layer joining the functional layers. A method for manufacturing an electronic component having a plurality of functional layers each selected from a magnetic layer and dielectric layer comprising the steps of: laminating green sheets for forming the functional layers, to provide a laminated body having also a layer made of the joining material as claimed in any of claims 1 to 3 provided between the laminated green sheets, and firing the laminated green sheets with the layer made of the joining material to form the functional layers and the joining layer joining the functional layers. The method as claimed in claim 6 or 7, wherein the layer made of the joining material is provided in the form of a green sheet, paste, slurry or thin film.

Inventors: KODA YASUNORI, OOBUCHI TAKESHI, KODA, YASUNORI, OOBUCHI, TAKESHI
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1999
Main classification: C03C8
IPC codes: C03C8, C09J1, C04B37, H01G4