JP2013115107A - Ceramic substrate with built-in varistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem of multilayer varistor components, compaction and thinning of which are in progress, that vaporization of the components containing a bismuth oxide in a varistor layer during the burning process may cause degradation of the varistor characteristics and reliability.SOLUTION: In a ceramic substrate 8 with a built-in varistor including at least a varistor layer 2 containing a zinc oxide, a bismuth oxide, and a manganese oxide, a pair of internal conductors 4 formed to sandwich the varistor layer 2, and a first ceramic substrate 1 provided on one side or both sides of the varistor layer 2, the first ceramic substrate 1 contains a manganese oxide, a bismuth oxide, and a niobium oxide as sub-components.

Description

  The present invention relates to a varistor built-in ceramic substrate for mounting an LED (light emitting diode) or a semiconductor.

  In recent years, electronic devices have been rapidly reduced in size and power consumption, and accordingly, the withstand voltage of various electronic components constituting the circuit of the electronic device has been reduced. This is because various electronic components, especially semiconductor devices, etc. are easily damaged by electrostatic pulses generated when the human body and electronic devices are in contact with each other. .

  As this semiconductor device, light emitting diodes (LEDs) are mainly raised, and application to many products such as general lighting fixtures, backlights for televisions, strobe light sources for cameras, etc. is currently being studied, and demand will increase in the future. That is expected.

  As this application expands, there is a great demand for higher brightness and higher output of LEDs and LED packages using the LEDs, and troubles due to electrostatic breakdown such as the PN light emitting layer are a major problem in high brightness LEDs. It has become.

  Patent document 1 etc. are known as an anti-static component for LED packages which are such conventional semiconductor devices. However, the anti-static component described in Patent Document 1 has a structure in which a varistor layer for absorbing static electricity is sandwiched between an insulating ceramic substrate and an insulating glass ceramic layer, and the oxidation contained in the varistor layer. Components necessary for absorbing static electricity, such as bismuth and manganese oxide, evaporate or diffuse into the substrate during firing, resulting in electrostatic absorption effects, so-called varistor characteristic deterioration, and reliability. Will cause a decline.

International Publication No. 2006/106717

  The present invention solves the above-described problems, and an object thereof is to provide a varistor built-in ceramic substrate having excellent varistor characteristics.

  In order to solve the above problems, a varistor-embedded substrate according to the present invention includes at least zinc oxide, bismuth oxide, a varistor layer containing manganese oxide, a pair of internal conductors formed so as to sandwich the varistor layer, and the varistor layer. A varistor-embedded ceramic substrate having a first ceramic substrate provided on one or both sides of the varistor, wherein the first ceramic substrate contains manganese oxide, bismuth oxide and niobium oxide as subcomponents. A substrate was used.

  As described above, the varistor built-in ceramic substrate of the present invention uses the first ceramic substrate containing the same material as the bismuth oxide and manganese oxide contained in the varistor layer as a constituent component on one or both sides of the varistor layer. It is possible to suppress bismuth oxide and manganese oxide contained in the varistor layer from evaporating during the firing step or diffusing into the ceramic substrate provided above and below.

Sectional drawing of the varistor built-in ceramic substrate in one Example of this invention Sectional drawing of the varistor built-in ceramic substrate in one Example of this invention

  The varistor built-in ceramic substrate of the present invention will be described below.

  FIG. 1 is a sectional view showing a varistor built-in ceramic substrate 8 according to an embodiment of the present invention.

  The varistor built-in ceramic substrate shown in FIG. 1 has a configuration in which the upper and lower surfaces of the varistor layer 2 are sandwiched between the first ceramic substrate 1 and the second ceramic substrate 3. A pair of opposed internal conductors 4 are provided inside the varistor layer 2, and the internal conductors 4 are vias penetrating the first ceramic substrate 1, the varistor layer 2, and the second ceramic substrate 3. The electrode 5 is electrically connected. The main surface electrode 6 is disposed on the upper surface of the second ceramic substrate 3, and a semiconductor device such as an LED is mounted on the upper surface of the main surface electrode 6. The terminal electrode 7 is disposed on the upper surface of the first ceramic substrate 1 and serves as an electrode for mounting the varistor built-in ceramic substrate 8 itself. The main surface electrode 6 and the terminal electrode 7 are electrically connected through the via electrode 5. .

  The main surface electrode 6 may be formed on the upper surface of the first ceramic substrate 1, and the terminal electrode 7 may be formed on the upper surface of the second ceramic substrate 3, so that the configuration described above may be turned upside down.

  The material composition of the varistor layer 2 is preferably 80% by weight or more of the main component zinc oxide and 0 to 20% by weight of auxiliary components such as bismuth oxide, manganese oxide, antimony oxide, and cobalt oxide. Excellent varistor characteristics can be obtained by the material composition.

  The first ceramic substrate 1 contains aluminum oxide as a main component and bismuth oxide, manganese oxide, and niobium oxide as subcomponents. The auxiliary component contains the same component as that of the varistor layer 2, so that a low melting point auxiliary component such as bismuth oxide or manganese oxide is evaporated from the varistor layer 2 during firing or is applied to the substrate disposed above and below the varistor layer 2. It is presumed that diffusion can be suppressed. As a result, subcomponents such as bismuth oxide and manganese oxide contained in the varistor layer 2 remain uniformly dispersed in the varistor layer 2 even after firing, so that there is little variation in electrostatic absorption effect and a highly reliable varistor. A built-in ceramic substrate can be obtained.

  As the second ceramic substrate 3, an aluminum oxide substrate, an aluminum nitride substrate, a silicon nitride substrate, or the like can be used, but it is preferable that the second ceramic substrate 3 is made of a material having good heat conductivity and heat resistance and insulation.

  As described above, the varistor built-in ceramic substrate of the present invention uses the first ceramic substrate containing the same material as the bismuth oxide and manganese oxide contained in the varistor layer as a constituent component on one or both sides of the varistor layer. Since bismuth oxide and manganese oxide contained in the varistor layer can be prevented from evaporating or diffusing to the ceramic substrate provided above and below during the firing process, a varistor-embedded ceramic substrate having excellent varistor characteristics can be obtained.

  FIG. 2 is a sectional view showing a varistor built-in ceramic substrate 9 according to an embodiment of the present invention. FIG. 2 is obtained by replacing the second ceramic substrate 3 with the first ceramic substrate 1 in the varistor built-in ceramic substrate 8 shown in FIG. That is, by adopting a configuration in which the varistor layer 2 is sandwiched between the first ceramic substrates 1, evaporation of bismuth oxide and manganese oxide from the varistor layer 2 and diffusion to the upper and lower ceramic substrates can be further suppressed. .

  In addition, the antistatic component described in Patent Document 1 improves the sinterability of the substrate by using ceramic substrates including glass components as the ceramic substrates disposed on the upper and lower surfaces of the varistor layer 2. Since the component has a high thermal resistance, the thermal resistance of the ceramic substrate itself also increases, and it is difficult to sufficiently dissipate the heat generated during the operation of the semiconductor chip. The present invention is an invention that can improve the sinterability of the first ceramic substrate 1 by containing bismuth oxide and manganese oxide, which are the same components as the components of the varistor layer 2, and moreover than the conventional ceramic substrate. Also, the heat resistance is low, and heat generated during semiconductor device operation can be effectively dissipated.

  Next, a method for manufacturing the varistor built-in ceramic substrate 8 shown in FIG. 1 will be described.

  First, a fired aluminum oxide substrate was used as the second ceramic substrate 3. This aluminum oxide substrate is a commonly used aluminum oxide substrate. The aluminum oxide content is about 96%, and silicon oxide or the like is contained as a subcomponent about 4%.

  As a method of producing a hole for forming the via electrode 5, there is a method of drilling using a laser. As will be described later, it can be produced by laminating sheets and integrally firing with the varistor layer 2 in the same manner as the first ceramic substrate 1.

  Next, a varistor layer sheet to be the varistor layer 2 is produced as follows.

  First, when the total varistor powder is 100% by weight, zinc oxide is 80% by weight or more, and minor components such as bismuth oxide, manganese oxide, antimony oxide, cobalt oxide and the like are 20% by weight or less, binder resin, plasticizer , And a solvent, and after mixing and dispersing them, a slurry is prepared. Next, the slurry is applied onto a PET film by a doctor blade method and dried to prepare a varistor layer sheet.

  Next, the 1st ceramic sheet used as the 1st ceramic substrate 1 is produced as follows.

  First, assuming that the total content of aluminum oxide powder as a main component and bismuth oxide, manganese oxide and niobium oxide as subcomponents is 100 wt%, bismuth oxide is 50 wt% or more and 70 wt% or less, and manganese oxide is 15 wt%. After blending the binder resin, the plasticizer, and the solvent with 15 wt% or more and 25 wt% or less of niobium oxide and 15 wt% or less, a slurry is prepared by mixing and dispersing. Subsequently, the said slurry is apply | coated on a PET film by a doctor blade method, and it dries, and produces a 1st ceramic sheet.

  Next, a hole for forming the via electrode 5 is formed in the varistor layer sheet and the first ceramic sheet manufactured as described above. As this method, for example, there is a method of drilling using a mechanical puncher method. Each sheet with holes is filled with a conductive paste for via electrode 5 for forming via electrode 5 on second ceramic substrate 3, varistor layer sheet and first ceramic sheet. As a filling method, there is a method of embedding a conductive paste for the via electrode 5 in the hole of each sheet by a screen printing method. Next, on the varistor layer sheet in which the conductor paste for the via electrode 5 is embedded, the one that is printed by screen-printing the conductor paste for the inner conductor 4 and the one that does not print the conductive paste are prepared.

  A varistor layer sheet laminate is formed by laminating a desired number of the varistor layer sheets formed with the conductor paste for the inner conductor 4 and the varistor layer sheets not formed with the conductor paste for the inner conductor 4, respectively. To do.

  Next, a second ceramic substrate in which one side of the varistor layer sheet laminate is filled with the first ceramic sheet filled with the conductive paste for the via electrode 5 and the other side is filled with the conductive paste for the via electrode 5 is filled. 3 are laminated while heating to form a composite laminate.

  Next, the main surface electrode 6 and the terminal electrode 7 are formed on the main surface of the first ceramic sheet and the second ceramic substrate 3 by screen printing so as to be connected to the end portion of the via electrode. The main surface electrode 6 and the terminal electrode 7 may be formed either at the sheet stage before laminating the composite laminate or at the stage of the composite laminate.

  The via electrode 5, the inner conductor 4, the main surface electrode 6, and the terminal electrode 7 were all electrodes having Ag of 80% and Pd of 20%.

  The composite laminate thus obtained is debindered at a temperature of about 400 to 600 ° C., and finally fired at a temperature of 950 to 1050 ° C. to obtain a ceramic substrate with a built-in varistor.

  Hereinafter, the varistor built-in ceramic substrate of the present invention produced by the manufacturing method described above will be specifically described.

  In Example 1, the thickness of the varistor layer 2 after firing is the same as that of the effective layer (effective layer: the varistor layer 2 interposed between the pair of opposed internal conductors 4) for expressing the varistor characteristics. The thickness of the outer varistor layer formed above and below the effective layer through the opposing internal electrodes was 35 μm. The thickness of the first ceramic substrate 1 after firing is 30 μm. The thickness of the second ceramic substrate 3 disposed on the surface opposite to the first ceramic substrate 1 with respect to the varistor layer 2 was 0.25 mm. The binder removal was performed by baking at 600 ° C. for 2 hours and then at 1000 ° C. for 2 hours to obtain a varistor built-in ceramic substrate 8. The vertical and horizontal dimensions of the ceramic substrate 8 with a built-in varistor after firing were 2.0 mm × 2.0 mm.

  The varistor characteristics and thermal conductivity of the ceramic substrate 8 with a built-in varistor thus obtained were evaluated.

  The varistor characteristic was evaluated by measuring the voltage value when a current was passed through the sample in the range of 1 μA to 1 mA, and the varistor voltage V1 mA and the non-linearity α were obtained from the voltage-current characteristic. The varistor voltage V1 mA was defined as a voltage value when a current value of 1 mA was passed, and the evaluation method was to determine the varistor voltage V1 mA / mm (V) per unit thickness from the thickness of the effective layer described above. Further, the non-linearity α was evaluated by a ratio V1 mA / V10 μA of a voltage value V1 mA when a current value was passed through 1 mA and a voltage value V10 μA when a current value was passed through 10 μA. Therefore, the closer the non-linearity α is to 1, the more ideal and non-linearity is. In this evaluation, a non-linearity α of less than 1.3 is within the scope of the present invention, and a non-linearity α of 1.3 or more is out of the scope of the present invention.

  The thermal conductivity was evaluated by a temperature wave thermal analysis method with a vertical and horizontal dimension of 3.5 mm × 3.5 mm and a thickness dimension of 0.4 mm. In this evaluation, a thermal conductivity of 19.0 W / m · k or more was within the scope of the present invention, and a thermal conductivity of less than 19.0 was outside the scope of the present invention.

  In (Table 1), the evaluation result which examined the material composition ratio of the 1st ceramic substrate 1 is shown. In sample numbers 1 to 3, the composition ratio of the first ceramic substrate 1 was changed. Sample No. 6 has a configuration in which the first ceramic substrate 1 is not provided and one surface of the varistor layer 2 is exposed.

  Samples 1 to 3 each had a non-linearity α of less than 1.30 and good results were obtained. Samples No. 4 and No. 5 were 1.5 or more. From this result, when the ratio of manganese oxide, bismuth oxide and niobium oxide constituting the subcomponents in the first ceramic substrate 1 is 100 wt% of the total amount of subcomponents, the manganese oxide is 15.0 wt% to 25 wt%. 0.02% by weight, bismuth oxide 50.0% by weight to 70.0% by weight, niobium oxide 15.0% by weight to 25.0% by weight, it can be seen that good non-linearity α can be obtained. It was. In Sample No. 6 which did not use the first ceramic substrate 1, the varistor voltage was remarkably increased, and the non-linearity α was also a high value of 1.64. This is presumed that in the firing process, low melting point components such as bismuth oxide and manganese oxide evaporate, so that the sintering of the varistor layer 2 is remarkably reduced, the abnormal increase in varistor voltage and the non-linearity α are deteriorated. The

  In Example 2, the same manufacturing method as in Example 1 was used, and in the obtained varistor built-in ceramic substrate 8, the aluminum oxide content ratio contained in the first ceramic substrate 1 was changed and evaluated.

  Here, when the ratio of manganese oxide, bismuth oxide and niobium oxide constituting the subcomponents in the first ceramic substrate 1 is 100% by weight of the total amount of subcomponents, manganese oxide, bismuth oxide, niobium oxide The ratios were fixed at 20.0 wt%, 60.0 wt% and 20.0 wt%, respectively.

  In Sample No. 7 to No. 11 in which the aluminum oxide content in the first ceramic substrate 1 is 86.0 wt% to 96.0 wt%, the non-linearity α of the varistor is less than 1.30 and good results are obtained. Obtained. When the aluminum oxide content of sample number 12 was 97.0% by weight, the non-linearity α deteriorated to 1.37. This was because the proportion of aluminum oxide increased and bismuth oxide, which is a relatively minor component, was oxidized. It is presumed that the sinterability of the varistor layer 2 has decreased due to the decrease in the manganese ratio.

  As for thermal conductivity, in samples No. 7 to No. 10 in which the aluminum oxide content contained in the first ceramic substrate 1 is in the range of 88.0 wt% to 96.0 wt%, the thermal conductivity is 19 W. Good results were obtained, such as / m · k or more. Sample No. 11 having an aluminum oxide content of 86.0% by weight contained in the first ceramic substrate 1 had a low thermal conductivity of 17.9 W / m · k. This is because the thermal conductivity of aluminum oxide itself is lowered due to an increase in the ratio of subcomponents having low thermal conductivity. Sample No. 12 having an aluminum oxide content of 97.0% by weight contained in the first ceramic substrate 1 had a low thermal conductivity of 16.1 W / m · k. It is considered that this is because the ratio of subcomponents is relatively low and the liquid phase generated in the sintering process is reduced, so that the sintered compactness is lowered and the thermal conductivity is lowered.

  The ceramic substrate with a built-in varistor according to the present invention can exhibit an excellent electrostatic protection effect in a semiconductor device or the like, in particular, an LED mounting substrate in which brightness and output are increasing.

DESCRIPTION OF SYMBOLS 1 1st ceramic substrate 2 Varistor layer 3 2nd ceramic substrate 4 Internal conductor 5 Via electrode 6 Main surface electrode 7 Terminal electrode 8 Ceramic substrate with built-in varistor 9 Ceramic substrate with built-in varistor

Claims (5)

A varistor layer containing at least zinc oxide, bismuth oxide, and manganese oxide;
In a varistor built-in ceramic substrate having a pair of internal conductors formed so as to sandwich the varistor layer and a first ceramic substrate provided on one or both surfaces of the varistor layer,
The ceramic substrate with a built-in varistor, wherein the first ceramic substrate contains manganese oxide, bismuth oxide and niobium oxide as subcomponents. 2. The varistor-embedded ceramic substrate according to claim 1, wherein the content ratio of the subcomponent constituting the first ceramic substrate is in the following ranges when the total amount of the subcomponent is 100 wt%. .
50% by weight ≦ bismuth oxide ≦ 70% by weight
15% by weight ≦ manganese oxide ≦ 25% by weight
15 wt% ≤ niobium oxide ≤ 25 wt% The varistor built-in ceramic substrate according to claim 1, wherein a main component of the first ceramic substrate is aluminum oxide. 4. The varistor built-in ceramic substrate according to claim 3, wherein a content of the aluminum oxide in the entire first ceramic substrate is 88 wt% or more and 96 wt% or less. Placing the first ceramic substrate on one side of the varistor layer;
2. The ceramic substrate with a built-in varistor according to claim 1, wherein any one of an aluminum oxide substrate, an aluminum nitride substrate, and a silicon nitride substrate is provided on the other surface.

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