JP4438090B2 - Glass powder for conductor paste - Google Patents

Description

The present invention is a capacitor, relates to a glass powder for a conductive paste suitably used for the conductor paste suitable for forming terminal electrodes of multilayer ceramic electronic components (hereinafter simply referred to as "multilayer electronic component") such as an inductor.

  A laminated electronic component is generally manufactured as follows.

  First, a conductor paste for internal electrodes is printed in a predetermined pattern on an unfired ceramic sheet such as a dielectric or magnetic material. A plurality of sheets are stacked and pressure-bonded to obtain an unfired laminate in which ceramic sheets and internal electrode paste layers are alternately laminated. The obtained laminated body is cut into chips having a predetermined shape, and then fired at a high temperature to form a ceramic body (hereinafter simply referred to as “element body”). Next, various methods such as dipping, brushing and screen printing of terminal electrode paste in which conductive powder and inorganic binder such as glass powder are dispersed in an organic vehicle are exposed on the exposed end face of the internal electrode of the element body After coating, drying and baking at a high temperature, a terminal electrode electrically connected to the internal electrode is formed. Thereafter, a nickel plating layer is formed on the terminal electrode as necessary, and then a plating layer made of tin or an alloy thereof having good solderability is formed by electroplating. Conventionally, noble metals such as Pd, Ag, Ag—Pd, and Pt have been used as the internal electrode material, and in recent years, base metal materials such as Ni and Cu have also been used.

  On the other hand, for the terminal electrode, a metal that easily forms a good electrical connection with these internal electrode materials is used, and Ag, Au, Pd, Pt, Ni, Co, Cu, and alloys thereof are used. In particular, when a base metal is used as the terminal electrode material, in order to prevent the base metal from being oxidized and lowering the conductivity, in a non-oxidizing atmosphere, that is, in an inert atmosphere or reducing atmosphere such as nitrogen or hydrogen-nitrogen. Inside, baking is performed at a peak temperature of about 700 to 900 ° C. In order to form a terminal electrode having excellent electrode characteristics such as conductivity and adhesiveness even when baked in such a non-oxidizing atmosphere, an inorganic binder contained in the terminal electrode is used in the non-oxidizing atmosphere. It is necessary to use a reduction-resistant glass that is stable even when fired.

  In addition, when electroplating the terminal electrode film, the glass component may be altered and dissolved by the acidic electroplating solution, thereby destroying the glass structure and greatly reducing the adhesive strength with the element body. In addition, at this time, due to the plating solution infiltrated into the electrode film from the melted portion of the glass component or the void in the fired film, the insulation resistance was lowered and the cracks of the element body were caused. The plating solution is heated and gasified during solder reflow, which may cause a so-called “solder explosion phenomenon” in which molten solder scatters. For this reason, the glass used for the conductor paste forming the terminal electrode of the laminated electronic component is required to have a characteristic that it is difficult to be affected by the acidic plating solution and can form a dense fired film.

Conventionally, for these purposes, Ba-based and Zn-based glasses have been generally used for terminal electrodes (Patent Document 1). In addition, the use of alkali silicate glass with a large amount of Si component has been studied (Patent Documents 2 and 3).
JP 2003-246644 A JP 2003-347148 A JP 2002-25337 A

  In recent years, demands for higher capacity, higher performance, and higher reliability for multilayer ceramic parts have become increasingly severe. In particular, in a small-sized and large-capacity multilayer ceramic capacitor, there is an increasing demand for thinning of the terminal electrode with downsizing, and a thin film having a film thickness of 50 μm or less and a thin film with a film thickness of 20 μm is also required It has become. In order to obtain excellent electrode characteristics equal to or better than those of conventional electrodes with such a thin electrode film, it is necessary to be denser, have higher adhesion strength to the element body, and have excellent plating solution resistance. .

  However, the paste using Ba-based glass or Zn-based glass has a problem that sufficient characteristics cannot be obtained when the terminal electrode is thinned in response to such a requirement, and Zn having relatively good acid resistance. Even when the glass is used, the plating solution resistance is insufficient. This is considered as follows.

  That is, conventional Ba-based glass and Zn-based glass are not so high in acid resistance of the glass itself. However, when these glasses are baked together with conductive powders, by forming a dense fired film structure with few voids, the penetration of the plating solution into the film is suppressed, and particularly in the case of Zn-based glass It is considered that a strong reaction layer is formed between the glass and the element body, and the adhesive strength and the film strength are increased, so that the strength deterioration is less likely to occur even when the plating solution penetrates. Therefore, in the Ba-based glass and Zn-based glass, when the electrode film has a certain thickness, the entire fired film has a plating solution resistance due to the fired film structure. As they get thinner, these glasses have limitations.

  On the other hand, when the alkali silicate glass is used, the acid resistance of the glass itself is large, and the plating solution resistance of the electrode film is improved to some extent. However, since it contains a large amount of an alkali metal component in order to lower the softening point, the fluidity is large, and the glass is likely to soak into the element body and cause a decrease in element strength and cracks. In addition, there is a problem that glass floats on the electrode surface and plating and soldering are difficult to adhere.

  The inventors of the present invention are particularly thin when the terminal electrode is electroplated using an acidic plating solution and the glass itself has sufficient acid resistance and the terminal electrode fired film does not have sufficient denseness. It was considered that sufficient plating solution resistance could not be obtained when forming the electrode film, and the reliability of the laminated part was lowered. And, it is found that the resistance of the plating solution is improved by using a glass having a low solubility in the plating solution of glass and exhibiting appropriate flow characteristics at the time of firing. As a result of investigation, the present invention has been achieved.

The object of the present invention based on the above-mentioned background is to form a terminal electrode that is dense, has high adhesive strength with the element body, has extremely excellent plating solution resistance, and can cope with thinning. and to provide a glass powder for a conductive paste suitably used for can Ru conductors paste it.

  The present invention has the following configuration.

(1) For conductor paste containing SiO ₂ , Al ₂ O ₃ , R ₂ O (R is an alkali metal) and R′O (R ′ is an alkaline earth metal), or B ₂ O ₃ in these components . a glass powder, the following components the glass powder at a content by weight%
_{SiO 2 42.0~65.0%, R 2 O} 8.0~18.0%, R'O 4.0~20.0%, B 2 O 3 0~18%, Al 2 O 3 3. 0 to 18.0%, La ₂ O _{3 0 to} 15%, satisfying the following formula (1), and the glass powder has a softening point Ts [° C.] and a glass transition point Tg [° C.] of 130 ≦ A glass powder for conductor paste , characterized by satisfying (Ts−Tg) ≦ 280.
(R ₂ O + R′O + B ₂ O ₃ ) / SiO ₂ ≦ 0.95 (1)

(2) The glass powder for a conductor paste according to the above (1), which is used for a conductor paste containing copper or a metal powder containing copper as a main component .

(3) The glass powder for a conductor paste according to (1) or (2) above, which is a conductor paste used for forming an electrode that is subjected to an acid plating treatment after firing in a non-oxidizing atmosphere .

The glass powder for conductor paste of the present invention has sufficient acid resistance as a characteristic of the glass itself. Resistant Therefore, the terminal electrodes of the multilayer electronic component of the glass powder is formed by using a including conductive paste, as well as adhesive strength between compactness and ceramic body are good, excellent even thin Provided is a highly reliable multilayer electronic component that exhibits a plating solution property and does not cause problems such as a decrease in adhesion strength and peeling due to the penetration of the plating solution. Moreover, the conductor paste can be fired even in a non-oxidizing atmosphere.

  In the conductor paste of the present invention, the conductive powder is not particularly limited, and metal powders such as Au, Ag, Pt, Pd, Cu, Ni, and Co that are usually used in the conductor paste for forming terminal electrodes of laminated electronic components are used. However, in particular, when the conductive powder containing Cu is used, the effects of the present invention can be enjoyed more. The conductive powder containing Cu may be Cu powder, Cu alloy powder, mixed powder of these and other conductive metals, or inorganic material such as metal oxide, glass, ceramic on the surface of Cu powder. It is also possible to use metal-inorganic composite powder in which Cu is present, metal-inorganic composite powder obtained by coating a metal oxide, glass, ceramic powder or other metal powder with Cu.

The glass powder used for the conductor paste of the present invention is a SiO ₂ —Al ₂ O ₃ -based glass containing an alkali metal component and an alkaline earth metal component, the ratio of specific glass components, and further the glass softening point Ts. The temperature difference (Ts−Tg) between the glass transition point Tg and the glass transition point Tg is controlled.

  Hereinafter, a description will be given based on FIG. FIG. 1 is a DTA curve obtained by placing a commercially available glass powder in a sample pan and conducting differential thermal analysis. As can be seen in FIG. 1, when heat is applied to the glass powder, endotherm and heat generation occur at specific temperatures such as the glass transition point Tg and the yield point. It is known that the initial temperature of the endotherm that appears first is the glass transition point Tg.

  Therefore, in the following description, the transition point Tg of the glass powder is the one obtained from the DTA curve obtained by differential thermal analysis, and specifically, the tangent of the baseline on the DTA curve and the glass transition. A value obtained from an intersection with a tangent at a steep position after bending in the endothermic region is described.

  Further, in FIG. 1, when the glass powder passes the glass transition point Tg, the sintering starts, and the shape of the powder is maintained and the surface is rough until the temperature Ts. Immediately before the temperature Ts, the powders are in the most compacted state. However, when the temperature Ts is exceeded, the powder begins to flow, and the shape of the powder cannot be maintained rapidly, and the sample surface begins to show gloss. The situation is observed.

  Therefore, in the following, the softening point Ts of the glass powder means a temperature Ts at which such a state change appears. Specifically, it is subtracted at a steep position before and after the bending point caused by glass softening on the DTA curve. The values obtained from the intersections of the tangent lines are shown.

  In the glass powder of the present invention, the difference (Ts−Tg) between the glass softening point Ts and the glass transition point Tg must be within a range of 130 ° C. or higher and 280 ° C. or lower. The value of (Ts−Tg) corresponds to the temperature from the start of the glass flow until the glass starts to flow. When this value is less than 130 ° C., the glass is likely to penetrate into the element body, and the element body is easily damaged. Moreover, when it exceeds 280 degreeC, it will become difficult to flow at high temperature, sintering of metal powder will be inhibited and a terminal electrode will become difficult to become dense. Preferably, (Ts−Tg) is in the range of 150 ° C. or more and 250 ° C. or less. Moreover, it is preferable that the glass transition point Tg is 500 degrees C or less.

  In general, glass containing a large amount of alkali metal components and alkaline earth metal components is considered to have poor acid resistance and water resistance. However, according to the study by the present inventors, by controlling each of the above-mentioned components to a specific ratio, it has excellent acid resistance and water resistance, is stable even in non-oxidizing atmosphere firing, and has an adhesive strength with a ceramic body. A glass powder capable of forming a dense fired film having a large thickness was obtained.

  Hereinafter, the composition range of the glass used in the present invention will be described. In addition, unless otherwise indicated, the content rate% of each component which comprises the glass of this invention below is the weight percentage based on the total weight of glass.

SiO ₂ and B ₂ O ₃ function as glass forming components, preferably SiO ₂ is included in the range of 42.0 to 65.0%, and B ₂ O ₃ is included in the range of 0 to 18%. When SiO ₂ is below this range, the acid resistance of the glass powder is lowered, and when it is above, the viscosity becomes high and sintering becomes difficult. The acid resistance when B ₂ O ₃ exceeds this range, the water resistance is poor, plating solution resistance decreases. B ₂ O ₃ / SiO ₂ is desirably 0.25 or less.

R ₂ O and R′O act as a flux and have the effect of lowering the glass softening point and improving fluidity. When one of R ₂ O and R′O is not included, a problem that the glass crystallizes or the fired film is too clogged and the glass floats easily occurs. Preferably, R ₂ O is included in a range of 8.0 to 18.0% and R′O is included in a range of 4.0 to 20.0%.

Although the kind of alkali metal of R ₂ O is not limited, it is desirable to include two or more kinds selected from Li, Na, K, Rb, Cs and the like because higher acid resistance can be expected due to the mixed alkali effect. Moreover, although the kind of alkaline-earth metal of R'O is not limited, it is desirable that two or more kinds selected from Be, Mg, Ca, Sr, Ba and the like are included for the same reason.

In the present invention, it is important that the following formula (1) holds for the above-described SiO ₂ , B ₂ O ₃ , R ₂ O, and R′O.
(R ₂ O + R′O + B ₂ O ₃ ) / SiO ₂ ≦ 0.95 (1)
In the formula (1), if the value of (R ₂ O + R′O + B ₂ O ₃ ) / SiO ₂ exceeds 0.95, the acid resistance and water resistance are deteriorated, and both the plating solution resistance and the denseness of the terminal electrode are compatible. It becomes difficult. Further, (R ₂ O + R′O + B ₂ O ₃ ) / SiO ₂ is desirably 0.30 or more. Below this value, the fluidity will deteriorate.

Both Al ₂ O ₃ and La ₂ O ₃ improve chemical durability such as acid resistance. In particular, Al ₂ O ₃ promotes vitrification as a typical intermediate oxide. Preferably, Al ₂ O ₃ is contained in a range of 3.0 to 18.0%, and La ₂ O ₃ is contained in a range of 0 to 15%. When Al ₂ O ₃ falls below this range, it becomes easy to crystallize, and when it exceeds, the glass softening point rises, making it difficult to control the value of (Ts−Tg) within the range of 130 to 280 ° C. Become. La ₂ O ₃ has the effect of lowering the melting temperature of the glass, but when it is contained in an amount of 15% or more, penetration of the glass into the body is promoted.

  In addition, as a component contained in the glass powder of the present invention, one or more of manganese oxide and copper oxide may be included. Manganese oxide and copper oxide have the effect of increasing the wettability with Cu powder, and also improve the binder removal property. Both are included in the glass at about 5%, so that there is a sufficient effect, and the range of 0 to 10% is preferable.

  In addition to these, the glass powder of the present invention may contain a small amount of other oxides such as Sn, Ni, Fe, Co and the like within a range not affecting the characteristics.

  In addition, when ZnO is contained in glass powder, glass powder will react with the titanium oxide contained in a board | substrate, and will become easy to produce a reaction layer. Therefore, for example, when used as a conductor paste for terminal electrodes of multilayer ceramic capacitors, it reacts with dielectric materials such as barium titanate and titanium oxide to contribute to the improvement of the adhesive strength between the ceramic body and glass. When the internal electrode is not sufficiently exposed at the end of the element body and the end of the internal electrode is covered with ceramic, the ceramic is dissolved to improve the bondability between the internal electrode and the terminal electrode. Can also be expected. On the other hand, however, since ZnO is contained, a crystal phase that is a reaction phase with titanium oxide is excessively generated, and conversely, there arises a problem that the adhesive strength and the strength of the ceramic body are deteriorated. It can also be a cause.

  Therefore, in the conductor paste of the present invention, in addition to the glass powder of the present invention, it is desirable to mix and use a Zn-based glass powder containing ZnO as a main component. In this case, since the behavior during firing of each glass powder is different, the above-described problem does not occur, and both the adhesion strength to the laminated electronic component containing the titanium oxide component and the improvement of the plating solution resistance can be achieved.

Various known R′O—ZnO—B ₂ O ₃ system, R′O—ZnO—B ₂ O ₃ —MnO ₂ system, R′O—ZnO system, and R′O—ZnO are known as Zn glass powder. -MnO ₂ -based, R'O-ZnO-SiO ₂ -based, ZnO-B ₂ O ₃ -based glass powder (R and R 'are alkali metal and alkaline earth metal as described above) are used. Among them, a borosilicate zinc-based Pb-free glass powder containing 40-60% ZnO, 15-35% B ₂ O ₃ and 1-16% SiO ₂ described in Patent Document 1 is used. It is preferable to do.

  When mixing the glass powder of this invention and Zn-type glass powder, it is preferable that the ratio exists in the range of 6: 1-3: 2 by weight ratio.

  However, the present invention does not exclude the inclusion of ZnO in the glass powder itself of the present invention, and may be included as long as it does not affect the characteristics.

  The glass powder of the present invention can be produced by a method such as a sol-gel method, a spray pyrolysis method, an atomizing method, etc. in addition to a general method of producing by mixing, melting, quenching, and pulverizing raw material compounds of each component. .

  Although the magnitude | size of the glass powder of this invention is not specifically limited, Usually, a thing with an average particle diameter of 0.1-10 micrometers is used. In addition, when glass floating tends to occur on the surface of the terminal electrode, it may be prevented by controlling the particle size of the glass powder. Therefore, the glass powder of the present invention preferably has an average particle size of 0.5 to 5 μm, more preferably 1 to 4 μm.

  In the conductive paste containing the glass powder of the present invention, the mixing ratio of the glass powder to the conductive powder is not particularly limited, but is usually about 1 to 20 parts by weight with respect to 100 parts by weight of the conductive powder. The

  The vehicle in the conductor paste is not particularly limited, and usually used organic binders and solvents are appropriately selected and blended. For example, as organic binders, celluloses, acrylic resins, phenol resins, alkyd resins, rosin esters, etc., and as solvents, alcohol-based, ether-based, ester-based, hydrocarbon-based organic solvents, water, and mixed solvents thereof Is mentioned. In addition, plasticizers that are usually added, dispersants such as higher fatty acids and fatty acid esters, surfactants, and the like can be appropriately blended. The blending amount of the vehicle is not particularly limited, and is an appropriate amount capable of retaining the inorganic component in the paste, and is appropriately adjusted according to the use and application method.

  In addition to the above components, the conductive paste of the present invention usually contains inorganic components such as alumina, silica, copper oxide, manganese oxide, barium titanate, titanium oxide and the like, and the same quality as the dielectric layer. The ceramic powder, montmorillonite, and the like can be appropriately added depending on the purpose.

  Hereinafter, the present invention will be specifically described based on examples.

Example 1
Each glass raw material was prepared so as to have the oxide composition shown in Table 1, and melted at about 1300 to 1450 ° C. using a platinum crucible, and then the glass obtained by flowing out onto graphite and air-cooling was obtained with a stamp mill. After roughly pulverizing to an average particle size of about 35 μm, glass powders A to M having an average particle size of about 4 μm were obtained by pulverizing with a ball mill using an alumina ball. A glass powder N was produced in the same manner except that the average particle size was about 1.5 μm. Furthermore, a zinc-based glass powder Z was produced in the same manner except that the glass raw material was melted at about 1150 ° C. and the average particle size was about 1.5 μm. The glass powders marked with * in Table 1 are outside the scope of the present invention.

  Further, DTA measurement was performed on the coarsely pulverized glass powders A to N and Z to obtain a glass transition point Tg and a glass softening point Ts, and (Ts−Tg) was calculated.

  Next, the glass plating solution resistance test was performed as follows.

  A paste in which 10 parts by weight of each glass powder is dispersed in 3 parts by weight of an organic vehicle in which an acrylic resin binder is dissolved in benzyl alcohol is prepared, printed on a flat plate made by sintering barium titanate, and dried. After that, it was baked at 800 ° C. in a nitrogen atmosphere having an oxygen concentration of about 5 ppm to form a glass film having a thickness of about 20 μm. Thereafter, the substrate on which the glass film was formed was immersed in an organotin plating bath having a pH of about 4 for 2 hours, the change in weight before and after the immersion was examined, and the residual rate of the glass film was used as an index of the plating solution resistance.

  The results are shown in Table 1.

<Example 2>
Next, 100 parts by weight of Cu powder and 7 parts by weight of glass powder A were kneaded by a roll mill together with 40 parts by weight of a vehicle in which an acrylic resin binder was dissolved in terpineol to prepare a conductor paste.

  Samples 2 to 13 were produced in the same manner as Sample 1 except that the glass powder was changed to glass powders B to M.

Next, samples 1 to 13 were fired to a thickness of 40 μm on the terminal portion on the surface of the barium titanate-based multilayer ceramic capacitor body having a Ni internal electrode and an outer dimension of 2.0 mm × 1.2 mm × 1.2 mm. After being applied by dipping method and dried as described above, it was baked at 800 ° C. in a nitrogen atmosphere having an oxygen concentration of about 5 ppm to form a terminal electrode. Next, an Ni plating film and an Sn plating film are formed on the terminal electrode by electroplating, and the film density (denseness), presence / absence of penetration into the element body, thermal shock resistance, and tensile strength are as follows. The capacity defect was measured. The results are shown in Table 2.
[Film Density] The cross section near the terminal electrode of each capacitor chip (hereinafter simply referred to as “chip”) was observed with a scanning electron microscope to examine the state of pores in the fired film.
[Presence / absence of penetration into the element body] A cross section of each chip near the terminal electrode was observed with a scanning electron microscope to examine the presence or absence of microcracks generated in the element body due to penetration of the glass element body. .
[Thermal shock resistance] 20 chips were immersed in a solder bath set at 350 ° C. for 10 seconds, and then naturally air-cooled. When the ratio of cracks in each chip was 0%, it was less than 10%. In some cases, Δ, and more than 10%, ×.
[Tensile strength] Solder each of the two terminal electrodes facing each other so that the lead wire is perpendicular to the electrode surface, and pull the lead wire in the opposite direction using a strength measuring instrument. The value when the interface with the body was destroyed was examined.
[Capacity failure] In order to check the bondability with the internal electrode, the electrostatic capacity of each chip was measured, and a chip within ± 10% of the design value was marked with ◯, and a chip far apart was marked with ×.

<Example 3>
Sample 14-1 was produced in the same manner as Sample 1 except that glass powder N was used.

  Further, the sample 14 was the same as the sample 14-1, except that the glass powder was 7 parts by weight of the mixed glass obtained by mixing the glass powder N and the zinc-based glass powder Z at a weight ratio of 5: 2, 1: 1. -2 and 14-3 were produced.

  Next, each sample was fired under three firing conditions: 800 ° C. in a nitrogen atmosphere with an oxygen concentration of about 5 ppm, 780 ° C. in a nitrogen atmosphere with an oxygen concentration of about 5 ppm, and 780 ° C. in a nitrogen atmosphere with an oxygen concentration of about 10 ppm. After forming the terminal electrode and forming the Ni plating film and the Sn plating film in the same manner as in Example 2, the film density, presence / absence of penetration into the element body, thermal shock resistance, tensile strength, capacity failure of each chip Table 3 shows the results of the test.

It is the DTA curve obtained by putting glass powder generally marketed in a sample pan, and performing a differential thermal analysis.

Claims (3)

SiO ₂ , Al ₂ O ₃ , R ₂ O (R is an alkali metal) and R′O (R ′ is an alkaline earth metal), or a conductive paste glass powder further containing B ₂ O ₃ in these components. The glass powder has the following components in content by weight%
_{SiO 2 42.0~65.0%, R 2 O} 8.0~18.0%, R'O 4.0~20.0%, B 2 O 3 0~18%, Al 2 O 3 3. 0 to 18.0%, La ₂ O _{3 0 to} 15%, satisfying the following formula (1), and the glass powder has a softening point Ts [° C.] and a glass transition point Tg [° C.] of 130 ≦ A glass powder for conductor paste , characterized by satisfying (Ts−Tg) ≦ 280.
(R ₂ O + R′O + B ₂ O ₃ ) / SiO ₂ ≦ 0.95 (1) 2. The glass powder for a conductor paste according to claim 1, wherein the glass powder is used for a conductor paste containing copper or a metal powder containing copper as a main component . The glass powder for a conductor paste according to claim 1 or 2, wherein the glass powder for a conductor paste is used for a conductor paste used for forming an electrode subjected to an acid plating treatment after firing in a non-oxidizing atmosphere .

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