TWI882875B - Glass composition and copper paste for terminal electrode, multilayer ceramic capacitor and method of forming the same - Google Patents

Abstract

A glass composition and a copper paste for terminal electrodes, a multilayer ceramic capacitor and a method of forming the same are provided. The glass composition includes a first main ingredient, a first minor ingredient and a second minor ingredient. The first main ingredient includes alkaline earth metal oxides; the first minor ingredient includes zinc element; and the second minor ingredient includes aluminum element and silicon element. Based on the glass composition as 100 wt%, the first main ingredient is 70 wt% to 75 wt%. Based on the first main ingredient is 100 wt%, the first minor ingredient is 25 wt% to 30 wt%, and the second minor ingredient is 7 wt% to 11 wt%. Therefore, the terminal electrodes can have acid corrosion resistance, and a curing temperature during a manufacturing process of the multilayer ceramic capacitor can be decreased.

Description

Terminal electrode glass composition, terminal electrode copper paste, multi-layer ceramic capacitor and manufacturing method thereof

The present invention relates to a terminal electrode glass composition, in particular to a terminal electrode glass composition, a terminal electrode copper paste, a multi-layer ceramic capacitor and a manufacturing method thereof.

Multilayer Ceramic Capacitor (MLCC) can be divided into base metal electrode (BME) and noble metal electrode (NME) processes according to the electrode materials. The terminal electrodes of BME MLCC are usually made of copper, nickel and tin from the inside to the outside. The copper is sintered by sintering copper paste to form an alloy with the nickel of the inner electrode at high temperature to form the terminal electrode.

The copper paste raw material mentioned above must contain a glass component to act as a medium for the ceramic material in the ceramic capacitor element. The constituent elements of the glass component will affect the quality and electrical performance of the resulting terminal electrode.

Due to the current trend of product miniaturization, the thickness of MLCC components is also becoming thinner, and the number of layers is increased in response to the demand for high capacitance. However, this design will cause MLCC to accumulate stress, thereby reducing the reliability of MLCC. In addition, after the electroplating process, it was found that the electroplated nickel penetrated into the terminal electrode, causing component abnormalities and the proportion of product cracking also increased.

The terminal electrode can cover the nickel of the inner electrode, so it also has a protective effect. Therefore, the terminal electrode must be resistant to the subsequent acid plating process to prevent the electroplated nickel from penetrating into the inner electrode. In addition, the internal stress of the MLCC can be reduced by lowering the sintering temperature of the terminal electrode, thereby improving the reliability level of the thin-layer MLCC.

In view of this, it is urgent to provide a terminal electrode glass composition and a terminal electrode copper paste to enhance the acid resistance of the terminal electrode and reduce the sintering temperature of the terminal electrode.

One aspect of the present invention is to provide a terminal electrode glass composition, which contains specific constituent elements and contents to achieve the effects of lowering the sintering temperature and resisting acid corrosion.

Another aspect of the present invention is to provide a terminal electrode copper paste, which comprises the terminal electrode glass composition of the above aspect.

Another aspect of the present invention is to provide a method for manufacturing a multi-layer ceramic capacitor, which is manufactured by using a lower sintering temperature.

Another aspect of the present invention is to provide a multi-layer ceramic capacitor, which is manufactured using the method of the above aspect.

According to one aspect of the present invention, a terminal electrode glass composition is provided, which includes a first main component, a first auxiliary component and a second auxiliary component. The first main component includes an alkali metal oxide; the first auxiliary component includes a zinc element; and the second auxiliary component includes an aluminum element and a silicon element. Based on the terminal electrode glass composition being 100 wt%, the first main component is 70 wt% to 75 wt%. Based on the first main component being 100 wt%, the first auxiliary component is 25 wt% to 30 wt%, and the second auxiliary component is 7 wt% to 11 wt%.

According to one embodiment of the present invention, based on the first main component being 100 wt%, the content of the aluminum element is 5 wt% to 7.9 wt%.

According to one embodiment of the present invention, based on the first main component being 100 wt%, the content of silicon element is 2 wt% to 3.1 wt%.

According to one embodiment of the present invention, the content ratio of the silicon element to the aluminum element is no more than 1/2.

According to one embodiment of the present invention, the content ratio of the silicon element to the aluminum element is 1/5 to 1/2.

According to another aspect of the present invention, a terminal electrode copper paste is provided, which includes copper powder and the terminal electrode glass composition of the above aspect.

According to one embodiment of the present invention, based on the copper powder being 100 wt%, the terminal electrode glass component is 9 wt% to 11 wt%.

According to another aspect of the present invention, a method for manufacturing a multi-layer ceramic capacitor is provided. The method includes providing a multi-layer capacitor element; applying the terminal electrode copper paste of the above aspect on the multi-layer capacitor element to obtain a multi-layer ceramic capacitor semi-finished product; and performing a sintering process on the multi-layer ceramic capacitor semi-finished product to obtain the multi-layer ceramic capacitor, wherein the sintering temperature of the sintering process is less than 850°C.

According to one embodiment of the present invention, the sintering temperature is 760°C to less than 850°C.

According to another aspect of the present invention, a multi-layer ceramic capacitor is provided, which is manufactured using the manufacturing method of the multi-layer ceramic capacitor of the above aspect.

The terminal electrode glass composition, terminal electrode copper paste, multi-layer ceramic capacitor and the manufacturing method thereof of the present invention are applied to improve the acid corrosion resistance of the terminal electrode by using the terminal electrode glass composition having specific composition elements and contents, and reduce the sintering temperature in the multi-layer ceramic capacitor manufacturing process, thereby improving the reliability of the obtained multi-layer ceramic capacitor.

The following disclosure provides many different embodiments or examples to implement different features of the invention. The specific examples of components and configurations described below are intended to simplify the disclosure. These are of course only examples and are not intended to be limiting. For example, a description of a first feature formed on or above a second feature includes embodiments in which the first feature and the second feature are in direct contact, and also includes embodiments in which other features are formed between the first feature and the second feature, so that the first feature and the second feature are not in direct contact. In addition, the disclosure repeats component symbols and/or letters in various specific examples. The purpose of this repetition is to simplify and clarify the description and does not represent a relationship between the various discussed embodiments and/or configurations.

The making and using of embodiments of the present invention are discussed in detail below. However, it will be appreciated that the embodiments provide many applicable inventive concepts that can be implemented in a wide variety of specific contexts. The specific embodiments discussed are for illustration only and are not intended to limit the scope of the present invention.

As used in the present invention, "around", "about", "approximately" or "substantially" generally means within 20%, within 10%, or within 5% of the stated value or range.

As described above, the present invention provides a terminal electrode glass composition, a terminal electrode copper paste, a multi-layer ceramic capacitor and a manufacturing method thereof, so as to enhance the acid corrosion resistance of the terminal electrode by using a terminal electrode glass composition having specific composition elements and contents, and reduce the sintering temperature in the multi-layer ceramic capacitor manufacturing process, thereby enhancing the reliability of the obtained multi-layer ceramic capacitor.

The terminal electrode glass composition of the present invention comprises a first main component, a first auxiliary component and a second auxiliary component. The first main component comprises an alkali earth metal oxide, wherein the alkali earth metal oxide comprises an oxide of benzene (Be), magnesium (Mg), calcium (Ca), strontium (Sr) and/or barium (Ba). In some embodiments, based on the terminal electrode glass composition being 100 wt%, the content of the first main component is about 70 wt% to about 75 wt%. If the content of the first main component is too small (e.g., less than about 70 wt%), the temperature of the subsequent terminal electrode during sintering is too high, and the thinned multi-layer ceramic capacitor may crack due to excessive internal stress; conversely, if the content of the first main component is too large (e.g., greater than about 75 wt%), the acid corrosion resistance of the obtained terminal electrode is poor, which will lead to a decrease in the reliability of the multi-layer ceramic capacitor.

The first subcomponent mentioned above includes zinc element. The addition of zinc element helps to reduce the sintering temperature of the terminal electrode and has the function of bonding with the ceramic material of the ceramic capacitor element. In some specific examples, the source of the zinc element may be zinc oxide. In some embodiments, based on the first main component being 100 wt%, the addition amount of the first subcomponent is about 25 wt% to about 30 wt%. If the addition amount of the first subcomponent is too small (for example, less than about 25 wt%), the sintering temperature of the terminal electrode cannot be effectively reduced, and the bonding effect with the ceramic is not good; on the contrary, if the addition amount of the first subcomponent is too much (for example, greater than about 30 wt%), the resulting terminal electrode has poor acid corrosion resistance, which will lead to a decrease in the reliability of the multi-layer ceramic capacitor.

The second subcomponent includes aluminum and silicon. The addition of aluminum and silicon contributes to the ability to resist acid corrosion. In some specific examples, the source of aluminum may be aluminum oxide, and the source of silicon may be silicon oxide. In some embodiments, based on the first main component being 100 wt%, the amount of the second subcomponent added is about 7 wt% to about 11 wt%. If the amount of the second subcomponent added is too little (e.g., less than about 7 wt%), the resulting terminal electrode has poor acid corrosion resistance; conversely, if the amount of the second subcomponent added is too much (e.g., greater than about 11 wt%), the sintering temperature of the terminal electrode cannot be effectively reduced.

In some embodiments, based on the first main component being 100 wt%, the content of aluminum is 5 wt% to 7.9 wt%, and the content of silicon is 2 wt% to 3.1 wt%. Since aluminum and silicon have better resistance to different types of acids, when the addition amounts of aluminum and silicon are respectively within the aforementioned ranges, the acid corrosion resistance of the terminal electrode can be better.

In some embodiments, the content ratio of silicon to aluminum is no more than 1/2, preferably about 1/5 to about 1/2. When the content ratio of silicon to aluminum is controlled within the above range, the effect of reducing the sintering temperature due to excessive silicon can be avoided.

The terminal electrode copper paste of the present invention comprises copper powder and a terminal electrode glass composition dispersed in the copper powder. In some embodiments, based on 100 wt% of the copper powder, the terminal electrode copper paste comprises about 9 wt% to about 11 wt% of the terminal electrode glass composition. The terminal electrode glass composition having the above content range can make the terminal electrode copper paste have a higher surface density and appropriate conductivity after sintering.

Please refer to FIG. 1, which is a cross-sectional view of a multilayer ceramic capacitor 100 according to some embodiments of the present invention. The manufacturing method of the multilayer ceramic capacitor is described below using FIG. 1. First, a multilayer capacitor element 110 is provided, wherein the multilayer capacitor element includes an inner electrode 120. The terminal electrode copper paste mentioned above is applied on both sides of the multilayer capacitor element 110 to obtain a multilayer ceramic capacitor semi-finished product. Then, a sintering process is performed on the multilayer ceramic capacitor semi-finished product to sinter the terminal electrode copper paste into a terminal electrode 130 to obtain a multilayer ceramic capacitor 100.

In some embodiments, the sintering temperature of the sintering process is less than about 850°C, preferably about 760°C to less than about 850°C, and more preferably about 760°C. It is known that a sintering temperature of more than 850°C is required to make the terminal electrode have a 95% density level, but the stress accumulation will increase dramatically, resulting in an increased risk of cracking of the obtained multi-layer ceramic capacitor, and the reliability test has only a 50% yield. In contrast, the present invention can still make the terminal electrode have a density level of more than 95% under the condition of lowering the sintering temperature, and the reliability test has a passing level of 95%. It should be noted that the aforementioned reliability test mainly refers to the insulation resistance of the electrical property, which is tested at a rated voltage of 85°C for 500 hours. If the insulation resistance does not decrease, it is defined as a passing level.

It is known that if a multi-layer ceramic capacitor with a dielectric layer thickness of only about 0.8 μm and an effective area of nearly 200 layers is to be manufactured, the risk caused by residual stress is relatively high and the reliability test yield is not high. However, the application of the terminal electrode glass composition and the terminal electrode copper paste of the present invention can reduce the influence of stress by lowering the sintering temperature.

Furthermore, in addition to sintering copper, the terminal electrode also needs to use an electroplating process to electroplate nickel and tin on copper. After sintering, the terminal electrode glass composition and the terminal electrode copper paste of the present invention can be corroded less than 1% in an electroplating acid solution with a pH lower than 5. Therefore, the multi-layer ceramic capacitor produced can have high reliability and is conducive to mass production.

Several examples are used below to illustrate the application of the present invention, but they are not intended to limit the present invention. Those with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. Experimental Examples 1 to 9

Experimental Examples 1 to 9 are to mix alkaline earth metal oxide, zinc oxide, aluminum oxide and silicon oxide to prepare the terminal electrode glass composition. Alkaline earth metal oxide is 100 wt%, and Experimental Examples 1 to 9 are respectively mixed with zinc oxide, aluminum oxide and silicon oxide in different proportions, and the mixing ratios are shown in Table 1.

The terminal electrode glass composition of Experimental Examples 1 to 9 was mixed with copper powder to form a terminal electrode copper paste, wherein the content of the terminal electrode glass composition relative to the copper powder was 12 wt%. Then, the surface density of the copper layer of the terminal electrode was measured by sintering at a temperature of 760°C (±5°C). The measurement results are shown in Table 1 below.

It should be noted that the measurement step of the copper layer surface density includes photographing the end electrode surface with a scanning electron microscope (SEM) at a magnification of 3k after the end electrode is burned. Then, the surface density is obtained by calculating the hole ratio with drawing software. The fewer the holes, the greater the surface density. If there is overburning, a large amount of glass precipitation can be observed on the surface of the end electrode, which will increase the surface resistance of the end electrode and reduce the subsequent electroplating efficiency.

Table 1 Zinc Aluminum Silicon Surface density(%) Ratio relative to the first principal component (%) Experimental Example 1 30 5 2 Overburned Experimental Example 2 25 7.5 4.5 95% Experimental Example 3 30 20 10 85% Experimental Example 4 40 10 10 88% Experimental Example 5 20 20 20 80% Experimental Example 6 55 5 3 Overburned Experimental Example 7 50 7.5 5.5 92% Experimental Example 8 40 3 6 95% Experimental Example 9 35 5.5 8.5 90% Experimental Examples 1-1 to 1-5 and Experimental Examples 6-1 to 6-5

According to Table 1, although the surface density of the terminal electrode glass composition of Experimental Examples 1 and 6 is over-burned, over-burning means that there is a chance to obtain a surface density that is more in line with the standard (i.e., 95%~100%). Therefore, the formula of the terminal electrode glass composition of Experimental Examples 1 and 6 is used, and the mixing ratio of the terminal electrode glass composition and the copper powder is changed to prepare the terminal electrodes of Experimental Examples 1-1 to 1-5 and Experimental Examples 6-1 to 6-5. The surface density of the copper layer is measured using the same conditions as above. The mixing ratio and surface density are shown in Table 2 below.

Table 2

According to Table 2, the results of the surface density test of Experimental Examples 1, 6 and 6-1 are over-burned, which means that a large amount of glass is precipitated, which may cause the conductivity to decrease; while Experimental Examples 1-4, 1-5, 6-4 and 6-5 cannot reach the surface density that meets the standard because they contain too little end electrode glass composition. Therefore, Experimental Examples 1-1 to 1-3, Experimental Examples 6-2 and Experimental Examples 6-3 were selected for further testing.

The sintered terminal electrodes of Experimental Examples 1-1 to 1-3, Experimental Examples 6-2 and Experimental Examples 6-3 were placed in an electroplating acid solution with a pH lower than 5, and the area ratio of the copper layer surface etched by acid was observed. It is to be noted that the test step of the area ratio of copper layer etched by acid includes first immersing the sintered terminal electrodes in an electroplating nickel acid solution at a temperature of 60°C for 2 hours. After immersion, the electrodes were cleaned and dried, and then photographed with a scanning electron microscope, and then the changes in surface density after acid etching were calculated using a mapping software. In addition, the terminal electrodes of Experimental Examples 1-1 to 1-3, Experimental Examples 6-2 and Experimental Examples 6-3 were subjected to reliability testing after sintering, that is, the test was conducted at a rated voltage of 85°C for 500 hours to measure the degradation ratio of the insulation resistance. The above two test results are shown in Table 3 below.

Table 3 Copper layer acid corrosion area ratio (%) Insulation resistance degradation ratio (%) Experimental Example 1-1 <1% ≤5% Experimental Example 1-2 <1% ≤5% Experimental Example 1-3 <1% ≤5% Experimental Example 6-2 11% 30% Experimental Example 6-3 9% 25%

According to Table 3, the acid etched area ratios of Experimental Examples 1-1 to 1-3 are all less than 1%, and the insulation resistance degradation ratios are all no more than 5%; in contrast, the acid etched area ratios and insulation resistance degradation ratios of Experimental Examples 6-2 and 6-3 are both higher. Therefore, it can be seen from the above experimental examples that the terminal electrode copper paste prepared by mixing the terminal electrode glass composition with copper powder in a specific ratio in Experimental Examples 1-1 to 1-3 can still have a high surface density, a low acid etched area ratio, and a low insulation resistance degradation ratio under long-term high temperature after a relatively low temperature sintering process.

According to the above embodiments, the terminal electrode glass composition, terminal electrode copper paste, multi-layer ceramic capacitor and the manufacturing method thereof provided by the present invention can enhance the acid corrosion resistance of the terminal electrode by using the terminal electrode glass composition having specific composition elements and contents, and reduce the sintering temperature in the multi-layer ceramic capacitor manufacturing process, thereby enhancing the reliability of the obtained multi-layer ceramic capacitor.

Although the present invention has been disclosed as above with several embodiments, they are not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be defined by the scope of the attached patent application.

100: Multi-layer ceramic capacitor 110: Multi-layer capacitor element 120: Internal electrode 130: Terminal electrode

The present disclosure is best understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, as is standard practice in the industry, many features are not drawn to scale. In fact, for the sake of clarity of discussion, the dimensions of many features may be arbitrarily scaled. [Figure 1] shows a cross-sectional view of a multi-layer ceramic capacitor according to some embodiments of the present invention.

Domestic storage information (please note in the order of storage institution, date, and number) None Foreign storage information (please note in the order of storage country, institution, date, and number) None

100: Multi-layer ceramic capacitor

110: Multi-layer capacitor element

120: Inner electrode

130: terminal electrode

Claims (10)

A terminal electrode glass composition comprises: a first main component comprising an alkali earth metal oxide, wherein the first main component is 70 wt% to 75 wt% based on the terminal electrode glass composition being 100 wt%; a first secondary component comprising a zinc element, wherein the first secondary component is 25 wt% to 30 wt% based on the first main component being 100 wt%; and a second secondary component comprising an aluminum element and a silicon element, wherein the second secondary component is 7 wt% to 11 wt% based on the first main component being 100 wt%. The terminal electrode glass composition as described in claim 1, wherein based on 100 wt% of the first main component, the content of the aluminum element is 5 wt% to 7.9 wt%. The terminal electrode glass composition as described in claim 1, wherein based on the first main component being 100 wt%, the content of the silicon element is 2 wt% to 3.1 wt%. The terminal electrode glass composition as described in any one of claims 1 to 3, wherein the content ratio of the silicon element to the aluminum element is not more than 1/2. The terminal electrode glass composition as described in any one of claims 1 to 3, wherein the content ratio of the silicon element to the aluminum element is 1/5 to 1/2. A terminal electrode copper paste comprising: copper powder; and a terminal electrode glass composition as described in any one of claims 1 to 5. The terminal electrode copper paste as described in claim 6, wherein based on the copper powder being 100 wt%, the terminal electrode glass component is 9 wt% to 11 wt%. A method for manufacturing a multi-layer ceramic capacitor comprises: providing a multi-layer capacitor element; applying the terminal electrode copper paste as described in claim 6 or 7 on the multi-layer capacitor element to obtain a multi-layer ceramic capacitor semi-finished product; and performing a sintering process on the multi-layer ceramic capacitor semi-finished product to obtain the multi-layer ceramic capacitor, wherein a sintering temperature of the sintering process is less than 850°C. A method for manufacturing a multi-layer ceramic capacitor as described in claim 8, wherein the sintering temperature is 760°C to less than 850°C. A multi-layer ceramic capacitor is manufactured using the manufacturing method of the multi-layer ceramic capacitor described in claim 8 or 9.

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