JP3123310B2 - Conductive paste for chip-type electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste for chip-type electronic parts, and more particularly to a conductive paste for forming terminal electrodes of chip-type electronic parts such as chip capacitors, chip resistors, chip thermistors, chip inductors and the like. Regarding paste. More specifically, the present invention relates to a conductive paste for a chip-type electronic component to which an inorganic oxide crystal is added.

[0002]

2. Description of the Related Art In chip-type electronic components such as chip capacitors, chip resistors, chip thermistors, and chip inductors, terminal electrodes are formed on the surface of a bare chip made of a ceramic material constituting the chip-type electronic component.
To form this terminal electrode, first, a conductive paste prepared by kneading a metal powder, a glass frit and an inert organic vehicle is applied to the surface of the bare chip, dried, and then dried.
It is fired at a temperature of about 0 ° C to 850 ° C. Thereafter, Ni, Cu, Sn, and the like are formed by electrolytic barrel plating or electroless plating.
A plating film of a Sn / Pb alloy or the like is formed. The chip-type electronic component manufactured in this manner is used by soldering its terminal electrodes to a substrate.

That is, conventionally, glass frit has been added to a conductive paste for a chip-type electronic component in order to promote sintering of a metal and increase a bonding force at an interface between a bare chip and a terminal electrode.

[0004]

The glass frit in the conventional conductive paste has a terminal electrode baking temperature of 500 ° C. or less.
The glass composition must be softened and flow at 850 ° C. However, if the glass composition is designed to exhibit softening and flowing behavior in this temperature range, the coefficient of thermal expansion becomes a high coefficient of thermal expansion of 5 × 10 ⁷ or more. It is difficult to reduce the coefficient of thermal expansion. When the terminal electrode is formed of a conductive paste to which such a glass frit is added, there is a problem that compatibility of the thermal expansion and contraction with the element body is poor and a thermal shock level is low.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and has excellent thermal shock resistance, excellent plating solution resistance and moisture resistance, and also has excellent conductivity for forming a terminal electrode of a chip-type electronic component having good plating film forming property. It is intended to provide a conductive paste.

[0006]

The conductive paste for a chip-type electronic component according to the first aspect is a conductive paste containing a metal powder, an inorganic oxide crystal, and an inert organic vehicle,
In the conductive paste for a terminal electrode of a chip-type electronic component in which a terminal electrode is formed by baking after being applied to the surface of a bare chip made of a ceramic fired body, the inorganic oxide crystal contains 10 to 55 mol% of ZnO and B ₂ O ₃ 20-5
5 mol%, SiO _{2 0 to} 30 mol% , PbO 3
0 mol% or less, and the inorganic powder is mixed with the metal powder in an amount of 1 to 15% by weight.

According to a second aspect of the present invention, in the conductive paste of the first aspect, the chip type electronic component is a ceramic capacitor.

According to a third aspect of the present invention, there is provided the conductive paste for a chip-type electronic component according to the second aspect, wherein the ceramic dielectric constituting the ceramic capacitor comprises a lead-based perovskite, barium titanate or strontium titanate as a main component. It is characterized by doing.

Hereinafter, the present invention will be described in detail.

[0010] The conductive pace for chip-type electronic parts of the present invention.
The inorganic oxide crystals contained in the₂: 0 to 30 mol% B₂O₃: 20 to 55 mol% ZnO: 10 to 55 mol%PbO: 30 mol% or less  Containing, if necessary, further containing other inorganic oxide components.
It is.

The reasons for limiting the proportion of the inorganic oxide component will be described below.

[0012] SiO ₂ is added in order to obtain plating solution resistance, but if its ratio exceeds 30 mol%, sintering of the metal is delayed. Therefore, SiO ₂ is 0-30.
mol%.

B ₂ O ₃ is added to adjust the melting point of the obtained inorganic oxide crystal. When the content is less than 20 mol%, the effect is not sufficient. Has poor plating solution resistance. Accordingly, B ₂ O ₃ is a 20~55mol%.

[0014] ZnO is added in order to obtain an adhesive strength with the element, but if its proportion is less than 10 mol%, its effect is not sufficient. Become scarce. Therefore, ZnO
Is set to 10 to 55 mol%.

In the present invention, the inorganic oxide crystal further comprises 3
Contains 0 mol% or less of PbO, and A
_{l 2 O 3, ZrO 2,} TiO 2, may contain other oxides GeO ₂ or the like, in this case, A _l 2 _{O 3} is 20m
ol% or less, ZrO ₂ and TiO ₂ are each 10 mol
% Or less, and GeO ₂ is preferably 40 mol% or less. These, if the content ratio of the other components PbO
It is desirable that the total amount be 50 mol% or less.

In the conductive paste for a chip-type electronic component of the present invention, Ag, Au, Pd, P
A noble metal such as t, a base metal such as Cu or Ni, or a powder obtained by mixing these is used. The metal powder sinters to provide conductivity to the terminal electrodes.

As the inert organic vehicle, those obtained by dissolving methylcellulose, ethylcellulose and the like in an organic solvent such as butyl carbitol and terpineol are used. Generally, the above celluloses are 5 to the above organic solvent.
３０30% by weight. The organic vehicle is used for adjusting the viscosity of the obtained conductive paste and facilitating the application to the bare chip surface.

The conductive paste of the present invention is preferably 65 to 80% by weight when the paste weight is 100% by weight.
, Metal oxide of 1 to 15% by weight with respect to the metal powder, and the remainder is composed of an organic vehicle. If the metal powder is less than 65% by weight, the conductivity of the terminal electrode formed is poor, and if it exceeds 80% by weight, the viscosity characteristics of the conductive paste deteriorate.

In the present invention, the preferred compounding ratio of the inorganic oxide crystals in the conductive paste depends on the type of the sintered body constituting the bare chip, but the compounding ratio of the inorganic oxide crystals to the metal powder is less than 1% by weight. Therefore, when forming the terminal electrode, the sintering of the metal does not proceed and the sintered metal becomes porous, so that the plating solution can easily enter and the adhesive strength between the terminal electrode and the bare chip is reduced. As a result, the moisture resistance of the terminal electrode deteriorates. In particular, in the case of a multilayer ceramic capacitor, the dielectric loss tangent (tan δ) and the insulation resistance (IR) deteriorate. Conversely, when the compounding ratio of the inorganic oxide crystal exceeds 15% by weight, the inorganic oxide crystal floats on the surface of the electrode layer at the time of baking, and when the plating layer is further provided on the surface of the baked electrode layer, the amount of the plating film increases. Formation is inhibited. Therefore, the mixing ratio of the inorganic oxide crystal contained in the conductive paste is preferably set to 1 to 15% by weight based on the metal powder.

The conductive paste for a chip-type electronic component of the present invention is a multilayer ceramic capacitor, a chip inductor,
Chip thermistor, used for the terminal electrode formation of the chip-type electronic component chip resistors, etc., in particular, multilayer ceramic con
It is preferably used for forming a terminal electrode of a capacitor . in this case,
As dielectrics that constitute multilayer ceramic capacitors,
A ceramic dielectric material containing lead-based perovskite or barium titanate or strontium titanate as a main component is preferable. Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Fe
_1/2 Nb _1/2 ) O ₃ , PbTiO _{3 and the} like.

[0021]

The inorganic oxide crystal in which SiO ₂ , B ₂ O ₃ , ZnO , PbO and other components are blended at a predetermined ratio can easily be reduced in thermal expansion. A terminal electrode formed by baking the conductive paste used in the mixing ratio on the bare chip surface has excellent thermal shock resistance. In addition, it has excellent plating solution resistance and moisture resistance, and it is easy to form a plating film.

[0022]

Next, the present invention will be described more specifically with reference to examples and comparative examples.

Embodiment 14  As a chip-type electronic component, a chip-type multilayer ceramic as shown in FIG.
Making a mic capacitor 10 and examining its characteristics
, Various conductive pastes were evaluated. As shown in FIG.
The ceramic capacitor 10 has a bare chip 11
Electrodes formed on both ends of the chip 11 (inorganic oxidation)
Ag electrode containing a crystal). Chip 11
Lead perovskite (Pb (Mg_1/3Nb_2/3) O
₃), Which is composed of the noble metal Ag70 / Pd30
Having a part electrode 13, length 3.2 mm, width 1.6 mm, thickness
Only has a size of 0.85 mm. Ag base terminal electrode 1
2 is composed of a baked electrode layer, and N
The i-plated film 14 and the Sn / Pb-plated film 15 are arranged in this order.
Is formed.

The terminal electrodes were formed under the following conditions.

When the conductive paste is 100% by weight,
A conductive paste was prepared by kneading 75% by weight of a metal powder, an inorganic oxide crystal having a compounding ratio shown in Table 1 with respect to the metal powder, and an inert organic vehicle having a balance shown in Table 1 as a balance.

Here, the metal powder is 100% by weight of Ag, and the inorganic oxide crystals are SiO ₂ , B ₂ O ₃ , ZnO , P
four bO or be one containing other components, Table 1
At the composition ratio shown in Table 1. The organic vehicle used was a mixture of ethyl cellulose and butyl carbitol and terpineol.

The paste has a thickness of 90 μm after baking.
Is applied to both ends of the bare chip by a dip method, the temperature is raised to 650 to 850 ° C. under the atmospheric pressure, kept at this temperature for 5 minutes, and then cooled to room temperature at a rate of 20 ° C./min to obtain Ag. Was obtained.

Next, a Ni plating film and a Sn / Pb plating film were formed under the following conditions. pH 4.0, temperature 50
° C nickel sulfamate (Ni (NH ₂ SO ₃ ) ₂
(4H ₂ O) Using a bath having a composition of 120 g / l, a Ni plating film having a thickness of 1 to 3 μm was formed on the surface of the base electrode by electrolytic barrel plating. Furthermore, using a bath having a composition of 15 g / l of tin (Sn) and 6 g / l of lead (Pb) at a pH of 4.5 and a temperature of 25 ° C., an electrolytic barrel plating method was used to coat 10 g of Ni on the surface of the Ni plating film.
A Sn / Pb plating film having a thickness of about 15 μm was formed. Thus, a multilayer ceramic capacitor in which two more plating films were formed on the base electrode was obtained.

Various characteristics of the obtained multilayer ceramic capacitor were measured by the following methods, and the results are shown in Table 2. The numerical value n in parentheses is the number of tested samples.

(A) Capacitance (nF) and dielectric loss tangent (%) (n = 30) Measured at 1 KHz and 1 Vrms.

(B) Insulation Resistance (Ω) (n = 15) After applying a DC voltage of 25 V, the resistance was measured 30 seconds later.

(C) Reliability (moisture resistance load test) (n = 2
0) A DC voltage of 16 V was applied at a temperature of + 85 ° C. and a relative humidity of 85%, and the presence or absence of deterioration after 1000 hours was examined.

(D) Tensile strength (kgf) (n = 10) 0.8 mm is applied to the underlying external electrode of the multilayer ceramic capacitor.
A φ soldered steel wire was adhered on a hot plate at 230 ° C. by eutectic cream solder, and the steel wire was pulled to measure the tensile strength.

(E) Thermal shock test (n = 2
0) The sample was sandwiched with tweezers in Sn63 / Pb37 eutectic solder (H63A) melted at a temperature of 300 ° C., immersed for 3 seconds without preheating, and the presence or absence of cracks was observed with a stereoscopic microscope.

Comparative Examples 1 to 3 As shown in Table 1, pastes were prepared in the same manner except that the composition and the amount of the inorganic oxide crystals added to the conductive paste were out of the above examples. This paste was baked and plated in the same manner as in the example to obtain a multilayer ceramic capacitor, and various characteristics were similarly examined. The results are shown in Table 2.

[0036]

[Table 1]

[0037]

[Table 2]

As shown in Tables 1 and 2, the multilayer ceramic capacitor of the embodiment has no deterioration in electric characteristics, is excellent in thermal shock resistance, has a high tensile strength, and has a high quality stability as compared with the comparative example. It turned out to be excellent and reliable.

[0039]

As described in detail above, the conductive paste for a chip-type electronic component of the present invention has excellent thermal shock resistance, excellent plating solution resistance and moisture resistance, and has good plating film forming properties. The present invention provides a conductive paste for forming a terminal electrode of a chip-type electronic component.

Therefore, according to the conductive paste for a chip-type electronic component of the present invention, the plating film can be easily formed and the plating solution does not enter the terminal electrodes. High bonding strength with bare chip. There is no deterioration in electrical characteristics after plating. It has excellent moisture resistance and high reliability. It is possible to form a high-performance terminal electrode such as that described above, which is extremely advantageous industrially.

The conductive paste for a chip-type electronic component of the present invention is extremely effective particularly for forming terminal electrodes of a ceramic capacitor composed of a ceramic dielectric containing lead perovskite, barium titanate or strontium titanate as a main component.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor manufactured in an example and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Multilayer ceramic capacitor 11 Bare chip 12 Terminal electrode 13 Internal electrode 14 Ni plating film 15 Sn / Pb plating film

Claims (3)

(57) [Claims] 1. A chip-type electronic device comprising a conductive paste containing a metal powder, an inorganic oxide crystal, and an inert organic vehicle, which is applied to the surface of a bare chip made of a fired ceramic body and then baked to form a terminal electrode. In the conductive paste for terminal electrodes of a component, the inorganic oxide crystal is ZnO 10 to 55 mol%.
And B ₂ O ₃ 20 to 55 mol%, and SiO ₂ 0 to 30
% of PbO and 30 mol% or less of PbO , wherein 1 to 15% by weight of the inorganic oxide crystal is blended with respect to the metal powder. 2. The conductive paste according to claim 1, wherein the chip-type electronic component is a ceramic capacitor. 3. The conductive material for a chip-type electronic component according to claim 2, wherein the ceramic dielectric constituting the ceramic capacitor contains lead-based perovskite, barium titanate or strontium titanate as a main component. Paste.