JP2015065332A - Ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic electronic component having a terminal electrode using a base metal with good bondability of a substrate and good platability, even if bonding to a substrate by a lead-free solder.SOLUTION: In a ceramic electronic component, a terminal electrode of the ceramic electronic component is provided on a surface of a ceramic body, the terminal electrode contains Cu, Ni and Al, when an element ratio of three components of Cu, Ni and Al is set to be a:b:c(a+b+c=100), a composition range of (a, b, c) is in a domain(including lines connecting each point) enclosed by A(79, 1, 20), B(39, 1, 60), C(20, 20, 60), and D(40, 40, 20) on a composition diagram of the three components.

Description

  The present invention relates to a ceramic electronic component including a terminal electrode.

  In recent years, with the improvement in performance of electronic devices, the amount of noble metal used as an electrode material for electronic components to be mounted is increasing year by year. In particular, precious metals have a small reserve and production is unevenly distributed in specific minority countries, but there is a problem that it is difficult to recover from used products, so electrodes using base metals as electrode materials have been developed. ing.

  A general ceramic electronic component such as a varistor and a capacitor includes a ceramic body and a terminal electrode provided on the surface thereof. The terminal electrode is formed by baking an external electrode paste in which a metal powder such as copper (Cu) and glass frit are mixed. Furthermore, for the purpose of improving solder wettability and solder heat resistance when mounting ceramic electronic components on a circuit board or the like, two layers of a Ni plating layer on the outer surface of the terminal electrode and an Sn plating layer on the outer surface thereof Patent Documents 1 and 2 propose that a plating layer made of

JP-A-8-298018 JP 2001-345231 A

  The terminal electrode of the ceramic electronic component is required to have good conductivity as a terminal and bonding strength with the substrate. However, in the case of using base metal Cu as the electrode material of the terminal electrode of the ceramic electronic component, when joining with the pad on the board of the electronic device by solder, particularly when using lead-free solder, Due to the erosion of Cu, there is a portion where the terminal electrode and the internal electrode cannot be electrically connected, and there is a problem that the characteristics of the ceramic electronic component are lowered.

  In addition, when base metal Cu is used as the electrode material of the terminal electrode, there is a problem that the surface is oxidized by oxygen in the air with time, and the characteristics of the ceramic electronic component cannot be obtained sufficiently. For this reason, it is generally known to form a metal layer by plating on the surface of the terminal electrode, thereby suppressing Cu solder erosion and the progress of oxidation. There are also ceramic electronic components.

  Further, when base metal Al, which does not proceed with oxidation, is used as the electrode material of the terminal electrode of the ceramic electronic component, there is a problem that bonding to the pad of the substrate with a generally used solder is not possible.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a ceramic electronic component including a terminal electrode having good oxidation resistance without causing solder erosion even when lead-free solder is formed. And

  In order to achieve the above object, a ceramic electronic component of the present invention is a ceramic electronic component including a terminal electrode provided on the surface of a ceramic body, wherein the terminal electrode includes Cu, Ni, and Al, and Cu When the element ratio of the three components of Ni and Al is a: b: c (a + b + c = 100), the composition range of (a, b, c) is A (79, 1, 20) on the composition diagram of the three components. , B (39, 1, 60), C (20, 20, 60), and D (40, 40, 20) (including the line connecting the points).

  Within the range of the composition of the present invention, even when the substrate is joined with lead-free solder, the solder erosion does not occur, and a ceramic electronic component including a terminal electrode having good oxidation resistance can be provided.

  Furthermore, in the ceramic electronic component, it is preferable that the terminal electrode includes a glass component of 15% by volume or less. Thus, it is possible to provide a ceramic electronic component including a terminal electrode using a base metal having good adhesion to the ceramic body.

  The present invention can provide a ceramic electronic component including a terminal electrode having good oxidation resistance without causing solder erosion even when bonded to a substrate by lead-free solder.

It is sectional drawing which shows typically suitable one Embodiment of the ceramic electronic component of this embodiment. It is a figure which shows the ratio of Cu-Ni-Al of this embodiment.

  In the following, preferred embodiments of the present invention will be described with reference to the drawings as the case may be. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted. Unless otherwise specified, the positional relationship such as up / down / left / right is based on the positional relationship of the drawings.

  The ceramic electronic component according to the embodiment of the present invention is not particularly limited, but examples thereof include capacitors, piezoelectric elements, inductors, varistors, thermistors, resistors, transistors, diodes, crystal oscillation elements and composite elements thereof, and other ceramic electronic components. Is done.

  In the present embodiment, a ceramic electronic component 100 including the terminal electrode 10 is illustrated in FIG. As shown in FIG. 1, the ceramic electronic component 100 of the present embodiment includes a ceramic body 20 (hereinafter referred to as “element body 20”) and a terminal electrode 10 provided on a main surface 20 a of the body 20. The element body 20 has a laminated structure in which ceramic layers 21, 22, and 23 are laminated in this order. Through-hole electrodes 31 are formed in the through-holes provided in the ceramic layers 21, 22, and 23. The through-hole electrode 31 provided on the ceramic layer 21 disposed on the main surface 20 a side that is the mounting surface of the element body 20 is in electrical contact with the terminal electrode 10. The terminal electrode 10 is electrically connected to the through-hole electrode 31 of the ceramic layers 21, 22, and 23 via an internal electrode 32 embedded between the ceramic layers 21, 22, and 23.

  The terminal electrode 10 of the ceramic electronic component 100 can be joined to a pad of the substrate or the like with solder. The solder used for joining is not particularly limited. For example, lead-based Sn-Pb (lead) -based solder, Sn-Ag (silver) -based, Sn-Cu (copper) -based lead-free solder, or the like can be used. . When joining with lead-free solder, the melting temperature for the joining is higher than that of lead-based solder, and the effect of the terminal electrode 10 of the present invention is further obtained from the viewpoint of suppressing solder erosion.

The terminal electrode 10 of the present embodiment includes Cu, Ni, and Al. When the element ratio of the three components of Cu, Ni, and Al is a: b: c (a + b + c = 100), Cu− shown in FIG. On the three-component composition diagram showing the Ni—Al ratio, it is in the region surrounded by the following A, B, C, and D (including the line connecting the points).
(Cu, Ni, Al) = (79, 1, 20) (A)
(Cu, Ni, Al) = (39, 1, 60) (B)
(Cu, Ni, Al) = (20, 20, 60) (C)
(Cu, Ni, Al) = (40, 40, 20) (D)

  In the composition of the terminal electrode 10, the ratio of Cu in the three components of Cu, Ni, and Al is preferably from the viewpoint of forming the terminal electrode 10 having higher bondability even when bonded to the substrate by lead-free solder. 20 to 79 atomic%. If the Cu ratio becomes too high, solder erosion tends to occur. On the other hand, if the Cu ratio is too low, the conductivity is lowered. Furthermore, the range of 50 to 60 atomic% is a more preferable range from the viewpoint of conductivity.

  In the composition of the terminal electrode 10, the ratio of Ni in the three components of Cu, Ni and Al is from the viewpoint of forming the terminal electrode 10 having higher oxidation resistance and suppressing the solder erosion of the terminal electrode 10. Preferably it is 1-40 atomic%. If the Ni ratio becomes too high, the conductivity will decrease. Furthermore, the range of 5 to 20 atomic% is a more preferable range from the viewpoint of conductivity.

  In the composition of the terminal electrode 10, the ratio of Al in the three components of Cu, Ni and Al is preferably 20 to 60 atomic% from the viewpoint of forming the terminal electrode 10 having higher oxidation resistance and from the viewpoint of conductivity. It is. When the ratio of Al becomes too high, voids in the terminal electrode 10 increase, and the terminal electrode 10 is likely to be eroded by solder, resulting in a decrease in conductivity. On the other hand, when the ratio of Al becomes too low, the adhesiveness between the terminal electrode 10 and the ceramic body decreases. Furthermore, the range of 30 to 40 atomic% is a more preferable range from the viewpoint of conductivity.

In the three component ratio of Cu, Ni, and Al showing good characteristics of the terminal electrode 10, it is more preferable that Cu is the largest and then the ratio of Al and Ni is the smallest.

  The outer shape and dimensions of the element body 20 of the ceramic electronic component 100 according to the present embodiment are not particularly limited and can be appropriately set according to the application. The normal outer shape is a substantially rectangular parallelepiped shape, and the dimension is vertical (0.2 ˜5.6 mm) × width (0.1 to 5.0 mm) × height (0.1 to 1.9 mm).

  Although the thickness of the terminal electrode 10 according to the present embodiment may be appropriately determined according to the use or the like, it is usually preferably about 1 to 50 μm.

  The illustrated ceramic electronic component 100 is a multi-terminal type having two terminal electrodes 10 on the same surface, but the present invention can also be applied to a two-terminal type ceramic electronic component.

  Next, in the method of manufacturing the ceramic electronic component 100 shown in FIG. 1, the element body 20 is manufactured according to the procedure, and the terminal electrode 10 is formed on the main surface 20 a of the element body 20. 100.

The ceramic electronic component 100 is
A green laminated body having a plurality of ceramic green sheets (ceramic layers 21, 22, 23) and an electrode layer (internal electrode layer 32) embedded between adjacent ceramic green sheets is formed, and a through hole is formed. A first step of injecting an electrode there to form a through-hole electrode 31, firing and forming the element body 20;
And a second step of forming the terminal electrode 10 on the main surface 20a that is the mounting surface of the obtained element body 20. Hereinafter, details of each process will be described.

  The first step is a step for preparing the element body 20. The element body 20 here is not particularly limited, but, for example, zinc oxide can be used as a main component in order to obtain varistor characteristics.

  Next, the ceramic green sheets on which various electrode patterns to be the desired internal electrode layer 32 are formed are stacked in a predetermined order. Further, a ceramic green sheet on which no electrode pattern is formed may be appropriately inserted and stacked. In this process, a through hole is formed, and an electrode is injected therein to form a through hole electrode 31. In this manner, a green laminate having a plurality of ceramic green sheets, an electrode layer embedded between adjacent ceramic green sheets, and the through-hole electrode 31 can be obtained. The electrode at this time is not particularly limited, and the same electrode may be used for the internal electrode layer 32 and the through-hole electrode 31, or different electrodes may be used.

  Next, the obtained green laminated body is heated at 180 to 400 ° C. for 0.5 to 24 hours to perform binder removal. Then, the element | base_body 20 is obtained by baking at 850-1400 degreeC for 0.5 to 8 hours.

  The second step is a step of forming the terminal electrode 10 on the main surface 20 a of the element body 20. The method for forming the terminal electrode 10 is not particularly limited, and the terminal electrode 10 can be formed by a coating electrode forming method, a sputtering method, a vapor deposition method, or a combination thereof.

  At this time, for example, when the terminal electrode 10 is formed by baking the coating electrode, the metal powder of each element is weighed so as to be in the composition range, and then mixed to prepare an external electrode paste.

  An alloy powder may be used instead of the metal powder of each element. The produced external electrode paste is applied to the main surface 20a of the element body 20 by printing or dipping and fired to form the terminal electrode 10. The firing conditions for the external electrode are preferably about 600 to 800 ° C. and about 10 minutes to 1 hour, for example.

  In addition, when the terminal electrode 10 is formed by, for example, a sputtering method or a vapor deposition method, Cu, Ni, and Al targets and alloy targets made of the respective elements can be used.

Furthermore, a glass component containing SiO ₂ or B ₂ O ₃ may be included in the external electrode paste used when the terminal electrode 10 is formed as a coating electrode. The ratio of the glass component to the terminal electrode 10 is preferably 15% by volume or less from the viewpoint of adhesiveness between the element body and the terminal electrode 10. Furthermore, the range of 5 to 10% by volume is a more preferable range from the viewpoint that there is no glass floatation on the surface of the terminal electrode 10 to be joined with the solder and that a better bond is obtained.

Furthermore, when the terminal electrode 10 has a structure having a glass component, the glass component may contain Cu, Ni, and Al. In this case, Cu, Ni, and Al contained in the glass component are not conductive and are distinguished from Cu, Ni, and Al of the terminal electrode 10, and are three components of Cu, Ni, and Al in the terminal electrode 10. It is not included in the element ratio. In other words, Cu, Ni, and Al of the terminal electrode 10 are all metals and are distinguished from glass components. As a method for distinguishing between glass components Cu, Zn, and Ni and terminal electrode 10 Cu, Ni, and Al, a method of observing a cross section of terminal electrode 10 with EPMA (Electron Probe Micro Analyzer) and determining an element distribution Is exemplified. In this case, if SiO ₂ or B ₂ O ₃ is co-deposited, it can be judged and distinguished as the terminal electrode 10 if it is a glass component, Cu, Ni and Al components and mixtures thereof.

Incidentally, the components referred to here are simple substances and oxides, and for example, the Cu component indicates Cu, Cu ₂ O, CuO, etc. containing Cu element. The Ni component indicates Ni and NiO containing Ni element. The Al component indicates Al containing Al element, Al ₂ O _{3 and the} like. And glass component indicates that the oxide mainly composed of SiO ₂ or _B 2 _{O 3.}

  The ceramic electronic component according to the embodiment of the present invention thus manufactured is mounted on a printed circuit board or the like with solder or the like, and can be used for various electronic devices.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on examples with reference to the drawings.

Example 1
The slurry for forming the varistor element body was prepared by the following procedure. Zinc oxide powder, an organic binder, an organic solvent, and an additive were blended and mixed for 24 hours using a ball mill to obtain a slurry for a varistor element body.

  A conductive paste for forming an external electrode was prepared by the following procedure. Cu powder, Ni powder and Al powder were prepared as conductive powder. These powders are mixed so as to have the element ratios shown in Table 1, and 80 parts by mass of the total powder is mixed with 20 parts by mass of acrylic resin and terpineol, mixed using a three-roll mill, and terminal electrode A conductive paste for 10 was prepared.

  In order to further improve the adhesion between the terminal electrode 10 and the element body, 10 vol% glass frit was added to the conductive paste.

  A varistor (ceramic electronic component) having the same structure as the ceramic electronic component shown in FIG. 1 was prepared using the slurry for the varistor element body and the conductive paste. Specifically, first, a slurry for a varistor element body was applied onto a film made of polyethylene phthalate by a doctor blade method, and then dried to form a green sheet having a thickness of 30 μm.

  Next, an electrode pattern corresponding to the internal electrode 32 and the through-hole electrode 31 was formed on the green sheet. The electrode pattern was formed by applying or pasting a conductive paste containing palladium powder into a through-hole by a screen printing method and drying. Next, green sheets on which electrode patterns were formed were stacked to form a sheet laminate. The sheet laminate thus obtained was subjected to a heat treatment to remove the binder, and then fired to obtain an element body 20.

  On the main surface 20a of the element body 20 where the end surface of the through-hole electrode 31 was exposed, a conductive paste was applied by screen printing so as to cover the end surface of the through-hole electrode 31. The applied conductive paste was dried with hot air and then baked to produce a terminal electrode 10 to obtain a varistor of Example 1.

(Examples 2-17, Comparative Examples 1-6)
Except that the conductive paste was mixed with Cu, Ni, and Al conductive powders in the proportions shown in Table 1, varistors were produced in the same manner as in Example 1 to give Examples 2 to 17 and Comparative Examples 1 to 6. .

[Evaluation of terminal electrode]
<Evaluation of terminal electrode components>
The obtained varistor is polished so that the cross sections of both the terminal electrode 10 and the element body 20 as shown in FIG. 1 can be observed, and the distribution of metal elements in the entire cross section of the terminal electrode 10 is confirmed and the elements are quantified by EPMA. The evaluation results obtained by averaging the quantitative results are shown in Table 1. In addition, as a result of quantifying the elements separately in the surface region, the central region, and the vicinity of the interface with the element body, the amount of the elements is the same regardless of the position of the terminal electrode 10. It was confirmed that the composition was uniformly distributed throughout the cross section. The portion where SiO ₂ or B ₂ O ₃ which is the main component of glass is co-deposited was distinguished from the glass phase, and it was confirmed that the glass phase existed independently of the metal element.

<Evaluation of solder erosion>
The produced terminal electrode 10 of the varistor was joined to the pad (electrode) of the substrate with lead-free solder (96.5Sn / 3.0Ag / 0.5Cu) by reflow at 260 ° C., and a sample for evaluating solder erosion was produced. . The varistor is polished so that the cross sections of both the terminal electrode 10 and the element body 20 as shown in FIG. 1 can be observed, and the entire cross section excluding the vicinity of the joint interface between the terminal electrode 10 and the lead-free solder by EPMA It was confirmed whether a compound was formed. The case where the Sn compound was not formed was evaluated as “A” as good as no solder erosion occurred, and the case where the Sn compound was formed as “B” as poor as solder erosion occurred. The evaluation results are shown in Table 1.

<Oxidation resistance evaluation>
Regarding the oxidation resistance, the produced varistor was heat-treated in an air atmosphere at 150 ° C. for 24 hours, and the conductivity of the terminal electrode 10 before and after the heat treatment was evaluated, and the oxidation resistance was evaluated from the rate of change in specific resistance. The resistance value between both ends of the terminal electrode 10 of the varistor was measured using a digital multimeter, and the specific resistance was calculated from the obtained resistance value and the distance between measurements. When the resistivity change rate is less than 10%, the oxidation resistance is good and “good”, and when the resistivity change rate is 10% or more, the oxidation resistance is “bad”. It was shown in 2.

<Electrical evaluation of terminal electrode>
When the conductivity of the terminal electrode 10 is low, the characteristics of the ceramic electronic component when mounted on the substrate may be deteriorated. Therefore, the conductivity evaluation of the terminal electrode 10 was performed. For evaluating the conductivity of the terminal electrode 10, the resistance value between both ends of the terminal electrode 10 of the varistor was measured using a digital multimeter, and the specific resistance was calculated from the obtained resistance value and the distance between measurements. When the specific resistance is less than 10 ⁻² Ω · cm, it is practically good and “good” in the conductivity evaluation, and when the specific resistance is 10 ⁻² Ω · cm or more, the conductivity is insufficient and “bad”, The evaluation results are shown in Tables 1 and 2.

<Judgment>
The final “determination” of the terminal electrodes shown in Tables 1 and 2 is evaluation of solder erosion and oxidation resistance of the terminal electrode 10, both evaluations being “good” and conductivity evaluation being “good”. The sample that became became “good”. Moreover, the sample in which any evaluation of the solder erosion evaluation, the oxidation resistance evaluation, and the conductivity evaluation of the terminal electrode 10 was “defective” was defined as “defective”.

  When Cu, Ni and Al are included, the composition range in which the Cu content is in the range of 20 to 79 atomic%, the composition range in which the Ni content is in the range of 1 to 40 atomic%, and the Al content is 20 to 60 atomic% When the composition range within the range of 3 and the above three composition ranges are satisfied, solder erosion does not occur and sufficient oxidation resistance is obtained. Furthermore, the composition range in which the Cu content is in the range of 50 to 79 atomic%, the composition range in which the Ni content is in the range of 5 to 20 atomic%, the composition range in which the Al content is in the range of 20 to 60 atomic%, When the above three composition ranges were satisfied, it was confirmed that high conductivity was obtained and the characteristics as a favorable terminal electrode were exhibited.

(Examples 18 to 24, Comparative Examples 7 to 10)
Samples of varistors were produced in the same manner as in Example 1 except that the terminal electrode 10 was produced by sputtering, and designated as Examples 18 to 24 and Comparative Examples 7 to 10. For sputtering, an alloy target having a ratio of element ratios of Cu, Ni and Al components shown in Table 2 was used. After the chamber was evacuated to high vacuum, Ar gas was introduced to form the terminal electrode 10 on the varistor surface. Table 2 shows the element ratios of the targets used.

  In the same manner as in Example 1, the elements were quantified separately for the surface region of the terminal electrode 10, the central region, and the vicinity of the interface with the element body, and the components of the terminal electrode 10 were evaluated. Table 2 shows the evaluation results obtained by averaging the quantitative results. All samples confirmed that the composition of the terminal electrode 10 was the same composition as the target used. Table 2 shows the results of the evaluation of solder erosion of the terminal electrode 10, the evaluation of the oxidation resistance of the terminal electrode 10, and the conductivity evaluation.

  Similarly to the terminal electrode 10 produced by the coating electrode forming method, the terminal electrode 10 produced by the sputtering method, when containing Cu, Ni and Al, has a composition range in which the Cu content is in the range of 20 to 79 atomic%, Ni A composition range in which the content is in the range of 1 to 40 atomic%, a composition range in which the Al content is in the range of 20 to 60 atomic%, and satisfying the above three composition ranges, solder erosion does not occur and is sufficient. Oxidation resistance is obtained. Furthermore, the composition range in which the Cu content is in the range of 50 to 79 atomic%, the composition range in which the Ni content is in the range of 5 to 20 atomic%, the composition range in which the Al content is in the range of 20 to 60 atomic%, When the above three composition ranges were satisfied, it was confirmed that high conductivity was obtained and the characteristics as a favorable terminal electrode were exhibited.

In FIG. 2, Examples 1 to 24 are plotted as ● and Comparative Examples 1 to 10 as ◯, respectively. Assuming that the element ratio of the three components of Cu, Ni, and Al is a: b: c (a + b + c = 100), the composition range of (a, b, c) is the following A, B on the composition diagram of the three components: , C and D (including the line connecting the points).
(Cu, Ni, Al) = (79, 1, 20) (A)
(Cu, Ni, Al) = (39, 1, 60) (B)
(Cu, Ni, Al) = (20, 20, 60) (C)
(Cu, Ni, Al) = (40, 40, 20) (D)
Then, it was confirmed that the characteristics as a good terminal electrode were exhibited.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, the multilayer varistor is exemplified as the ceramic electronic component according to the present invention, but as the ceramic electronic component according to the present invention, a multilayer ceramic capacitor, a capacitor, a piezoelectric element, an inductor, a thermistor, a resistor, a transistor, Examples include diodes, crystal oscillation elements, composite elements thereof, and other surface-mount electronic components.

  The present invention can be applied to any ceramic electronic component in which terminal electrodes are formed on the outer surface.

10 Terminal electrode 20 Element body (ceramic element)
20a Main surface 21, 22, 23 Ceramic layer 31 Through-hole electrode 32 Internal electrode 100 Ceramic electronic component

Claims (2)

  A ceramic electronic component including a terminal electrode provided on a surface of a ceramic body, wherein the terminal electrode includes Cu, Ni, and Al, and the element ratio of three components of Cu, Ni, and Al is a: b: When c (a + b + c = 100), the composition range of (a, b, c) is A (79, 1, 20), B (39, 1, 60), C (20, 20, 60), D (40, 40, 20) in a region (including a line connecting each point) surrounded by a ceramic electronic component having a terminal electrode.   The ceramic electronic component according to claim 1, wherein the terminal electrode contains a glass component of 15% by volume or less.

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