JP2001230151A - Lead-less chip component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve solderability of lead-less chip components used in various kinds of electronic equipment to lead-free solder and improve the reliability of soldered joint surfaces. SOLUTION: On the outside connecting terminal layers 3 of this lead-less chip component, barrier metallic layers 4 are adhesively formed and plated Sn-based binary alloy coating films 5, the Sn of which contains a precipitated metallic element, such as Bi, Ag, Cu, Zn, In, Ni, etc., as metallic layers having high corrosion resistances to the lead-free solder by a barrel electroplating method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leadless chip component used for various electronic devices.
The present invention relates to a leadless chip component having external terminals compatible with lead-free solder.

[0002]

2. Description of the Related Art In recent years, interest in global environmental protection has increased, and a solder material made of a Sn-Pb alloy, which has been widely used in the past, for assembling electronic components and printed wiring boards in assembling various electronic devices. Accordingly, there is an increasing demand for lead-free external terminal plating of various leadless chip components.

In many conventional leadless chip components, a glass-based or resin-based conductive paste containing Ag as a main component is baked on an insulator such as ceramics constituting a circuit element to provide good solderability. So, usually
A barrier metal layer such as nickel or copper is plated thereon, and a metal such as tin (Sn) or solder (Sn-Pb) is plated on the outermost layer to form external terminals.

[0004]

However, leadless chip components in which the outermost layer of such external terminals is plated with tin or solder have the following problems.

[0005] When solder plating is applied, compatibility with many types of lead-free solder is poor, and there has been a problem that the reliability of electrical connection with a printed wiring board is impaired.

On the other hand, when tin plating is applied to the outermost layer, whiskers are generated by long-term storage, and solder wettability is deteriorated by long-term storage due to poor oxidation resistance. There was a problem of lack of sex.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to ensure solder wettability and reliability of electrical connection for various lead-free solders used in assembling electronic equipment circuits. And

[0008]

In order to achieve this object, the present invention provides an external connection terminal formed by baking a conductive paste as a surface treatment of an external terminal of a leadless chip component corresponding to lead-free solder. On the layer, Ni
Or a barrier metal layer such as Cu is deposited, and the outermost layer is formed of Bi, Ag, Cu, Zn, I based on Sn metal.
A Sn-based binary alloy plating layer in which one of metal elements such as n and Ni is eutectoid is deposited.

According to the present invention, Sn is provided on the outermost layer of the external terminal.
Bi, Ag, Cu, Zn, In, Ni based on metal
Coated with a binary alloy plating film that is eutectoid of one of the metal elements, such as whiskers due to long-term storage. Lead-free solder (Sn-Ag, Sn-Cu, Sn-Bi, Sn-
This leads to a leadless chip component having excellent solder wettability and reliability of the joint with respect to Zn-based components.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a barrier metal layer is provided on an external connection terminal layer, and the barrier metal layer is further provided with a Bi, Ag,
A leadless chip component in which an external terminal is formed by providing an Sn-based binary alloy plating film in which one of metal elements such as Cu, Zn, Ni, and In is codeposited, and the outermost layer of the external terminal is plated with Sn. By using a binary alloy plating, generation of Sn whiskers due to long-term storage can be prevented.
By lowering the melting point and improving the moisture resistance of the alloy, it is possible to obtain a leadless chip part having excellent solder wettability and reliability of a joint with various lead-free solders.

According to a second aspect of the present invention, there is provided a leadless chip component according to the first aspect, wherein the Sn-based binary alloy plating film is provided by heating and re-melting.
By providing the n-based binary alloy plating film by heating and re-melting, recrystallization of the Sn-based binary alloy coating occurs, and a leadless chip component with significantly improved wettability to various lead-free solders can be obtained. .

[0012] The invention described in claim 3 of the present invention is characterized in that Sn-
As a Bi-based binary alloy plating layer, the content of Bi is 2-1.
It is a leadless chip component having a range of 0%, and by co-depositing the Bi content in Sn in a range of 2 to 10% by weight, generation of whiskers can be prevented, and various types of lead-free solder can be used. A leadless chip component having excellent matching properties can be obtained.

[0013] The invention according to claim 4 of the present invention provides a method for producing a Sn-
Ag based binary alloy plating layer, Ag content is 1-5%
Lead-free chip parts with a range of 1 to 5%. By co-deposition of Ag content in Sn in the range of 1 to 5% by weight, whisker generation is prevented and matching with various lead-free solders is achieved. A leadless chip component having excellent properties can be obtained.

[0014] The invention according to claim 5 of the present invention provides a method for producing an Sn-
Cu based binary alloy plating layer, Cu content is 0.5 ~
It is a leadless chip part with a range of 10%, and Sn
By eutectoid Cu content in the range of 0.5 to 5% by weight, whisker generation is prevented and leadless chip parts excellent in matching with various lead-free solders are obtained. Can be

[0015] The invention according to claim 6 of the present invention provides a method for producing a Sn-
Zn-based binary alloy plating layer, Zn content 3-10
% Of the leadless chip component. The Zn content in Sn is co-deposited in a range of 3 to 10% by weight to prevent whisker from being generated and to prevent various kinds of lead-free solder. A leadless chip component having excellent matching properties can be obtained.

[0016] The invention according to claim 7 of the present invention provides a method for producing Sn-
An In-based binary alloy plating layer, with an In content of 0.5 to
It is a leadless chip part with a range of 5%. By co-depositing the In content in Sn in a range of 0.5 to 5% by weight, generation of whiskers is prevented, and various types of lead-free are obtained. A leadless chip component excellent in matching property with solder can be obtained.

[0017] The invention according to claim 8 of the present invention provides a method for producing Sn-
Ni-based binary alloy plating layer with Ni content of 0.5 to
This is a leadless chip part with a range of 3%. By co-depositing the Ni content in Sn in a range of 0.5 to 3% by weight, whisker generation is prevented, and various types of lead-free are obtained. A leadless chip component excellent in matching property with solder can be obtained.

An embodiment according to the present invention will be described below in detail with reference to FIG.

(Embodiment 1) FIG. 1 shows a sectional view of a multilayer ceramic capacitor as an example of a leadless chip component according to the present invention.

In FIG. 1, 1 is a dielectric ceramic,
It is made of barium titanate or the like.

Reference numeral 2 denotes an internal electrode layer, which is made of metallic palladium or metallic nickel.

Reference numeral 3 denotes an external connection terminal layer formed by baking a conductive paste. The external connection terminal layer 3 is made of a glass-based conductive material obtained by kneading a metal powder mainly composed of silver and a glass frit in a resin binder. Paste 600
A sintered body of silver and glass fired in a high temperature of ~ 800 ° C,
It is made of a conductive resin cured by baking at 150 to 200 ° C. a resin conductive paste obtained by dispersing and mixing metal powder mainly composed of silver in an epoxy resin.

Reference numeral 4 denotes a barrier metal layer, which is made of a metal such as nickel (Ni) or copper (Cu) deposited by a barrel-type electroplating method or an electroless plating method.

Reference numeral 5 denotes a Sn-based binary alloy plating film having excellent solder corrosion resistance to various lead-free solders.
It is a binary alloy plating film in which at least one kind of metal element is selected from metal elements such as g, Cu, Zn, In, and Ni, or an alloy film obtained by heating and re-melting them.

These binary alloy plating films are made of Sn-B
i, Sn-Ag, Sn-Cu, Sn-Zn, Sn-I
n, Sn-Ni, depending on the eutectoid ratio of various metal elements in Sn, the generation of whiskers, which are Sn needle-like crystals, the wettability to various lead-free solders, the mechanical properties of the solder joint surface, The reliability of the electrical connection is greatly affected.

In this embodiment, 3 to 5 μm is applied to the surface of the external connection terminal layer 3 made of conductive paste of the multilayer ceramic capacitor by barrel electroplating using a Watt bath.
The barrier metal layer 4 made of nickel having a thickness of m is formed, and the Sn-based binary alloy plating film 5 having different contents of the various metal elements described above is formed on the surface thereof by barrel electroplating.
Was formed to a thickness of about 5 μm, and the optimum alloy composition was determined for each alloy plating film.

First, the Sn—Bi-based binary alloy plating film is subjected to barrel electroplating using a methanesulfonic acid bath or a carboxylic acid bath as a plating bath, and the bath composition and current density are adjusted to make the eutectoid of Bi. Various amounts of Sn-
Bi-based alloy plating layers were formed, and the alloy plating films were evaluated for the occurrence of whiskers and their matching with various lead-free solders.

As a result, when the amount of Bi eutectoid was less than 2%, the Sn content was determined by a humidity resistance test (60 ° C., 90% RH).
No whiskers were observed, and the wettability tended to be reduced by the lead-free solder.

When the amount of Bi eutectoid exceeds 10%, the joint surface of the lead-free solder becomes brittle in the heat cycle test (-25 to 125 ° C.), and the reliability of the electrical and mechanical connections decreases. Results were obtained.

Accordingly, it was confirmed that the optimum range of the eutectoid content of Bi was 2 to 10% in the Sn—Bi based binary alloy plating film.

Next, the Sn—Ag alloy plating film is subjected to barrel electroplating using a methanesulfonic acid bath, an organic carboxylic acid bath, etc., and the bath composition, current density, etc. are adjusted to make the eutectoid of Ag. Various Sn-Ag alloy plating films having different amounts were formed, and the alloy plating films were evaluated and evaluated for the occurrence of whiskers and the matching property with various lead-free solders.

As a result, when the eutectoid content of Ag was less than 1%, the S content was determined by a humidity resistance test (60 ° C., 90% RH).
n whiskers were observed, and a tendency that wettability was reduced by the lead-free solder was observed.

When the eutectoid content of Ag was more than 5%, the melting point of the alloy plating film was increased and the wettability to the lead-free solder tended to be slightly reduced.

Therefore, it was confirmed that the optimum range of the eutectoid amount of Ag was 1 to 5% in the Sn—Ag based binary alloy plating film.

The Sn—Cu-based alloy plating film is mainly subjected to barrel electroplating using a methanesulfonic acid bath, and by adjusting the bath composition, current density, etc., various Sn—Cu alloys having different eutectoid amounts of Cu are used. Form a Cu-based alloy plating film,
These alloy plating films were evaluated for the occurrence of whiskers and their matching with various lead-free solders.

As a result, when the amount of eutectoid of Cu is less than 0.5%, the tendency of whisker formation is observed by the humidity resistance test (60 ° C., 90% RH), and the wettability by the lead-free solder tends to decrease. It was observed.

If the eutectoid content of Cu exceeds 10%, the moisture resistance and heat resistance of the alloy plating film are remarkably reduced, and the wettability of the lead-free solder is deteriorated due to the long-term storage property and the heat history in the mounting process. Was significantly reduced.

Accordingly, it was confirmed that the optimum content of Cu in the Sn—Cu-based alloy plating film was 0.5 to 10%.

The formation of the Sn—Zn alloy plating film is as follows.
Mainly performed by barrel electroplating using sulfosuccinic acid bath, citric acid bath, organic carboxylic acid bath, bath composition,
By adjusting the current density and the like, various types of S having different eutectoid amounts of Zn
An n-Zn-based binary alloy plating film was formed, and evaluation was made on the presence / absence of whiskers and the matching property with various lead-free solders.

As a result, when the eutectoid content of Zn was less than 3%, whiskers were observed in a humidity resistance test (60 ° C., 90% RH), and the wettability by the lead-free solder tended to decrease.

In the case of an alloy plating film in which the eutectoid content of Zn exceeds 10%, the moisture resistance and heat resistance are remarkably reduced, the wettability of the lead-free solder is remarkably reduced, and in particular, Sn—Cu, Sn -Poor compatibility with lead-free solder containing Cu such as Ag-Cu, and the result that the reliability of electrical and mechanical connection of the solder joint surface is remarkably reduced due to generation of Cu-Zn intermetallic compound is obtained. Was done.

Therefore, it was confirmed that the optimum range of the eutectoid amount of Zn was 3 to 10% in the Sn—Zn alloy plating film.

The formation of the Sn—In based alloy plating film is as follows.
By adjusting the bath composition, current density, etc., mainly by a barrel electroplating method using a sulfuric acid bath, various alloy plating films with different eutectoid amounts of In are formed, and the presence or absence of whisker generation and various lead-free solder We evaluated the matching.

As a result, when the eutectoid content of In is less than 0.5%, whiskers are observed by a humidity resistance test (60 ° C., 90% RH), and the wettability to various lead-free solders tends to slightly decrease. Obtained.

When the eutectoid content of In exceeds 5%, the reliability of mechanical connection at the lead flow solder joint tends to be slightly lowered.

Accordingly, it was confirmed that the optimum range of the Sn-In alloy plating film was 0.5 to 5% of the eutectoid content of In.

Finally, the Sn—Ni alloy plating film is formed mainly by a barrel electroplating method using a pyrophosphoric acid bath, and the eutectoid amount of Ni is varied by adjusting the bath composition and the current density. Various alloy plating films were formed and evaluated for the occurrence of whiskers and their matching with lead-free solder.

As a result, when the amount of Ni eutectoid was less than 0.5%, a tendency to generate whiskers was confirmed by a humidity resistance test (60 ° C., 90% RH).

When the amount of Ni eutectoid was more than 3%, the result was that the moisture resistance and heat resistance were significantly reduced, and the wettability to all lead-free solders was significantly reduced.

Therefore, it was confirmed that the Ni content in the Sn—Ni-based alloy plating film was in the optimum range of 0.5 to 3%.

In this embodiment, the outermost layer of the external connection terminal of the multilayer ceramic capacitor is plated with a binary alloy film having the above-mentioned various compositions at 250 to 270 ° C.
By immersing in rapeseed oil, coconut oil, silicon oil, etc. maintained at a temperature of and heating and remelting the alloy plating film, the generation of whiskers is completely suppressed regardless of the amount of eutectoid of various metal elements, and As a result, the moisture resistance and heat resistance of the alloy film were significantly improved, and the wettability to the lead-free solder was further improved with respect to the long-term storage of chip components and the heat history in the mounting process.

In this embodiment, a multilayer ceramic capacitor is used as a leadless chip component. However, in the present invention, a leadless chip component is not limited to a multilayer ceramic capacitor, but may be a chip resistor or a chip inductor. For example, the present invention is applied to all electronic components having external connection terminals using a conductive paste.

[0053]

As is apparent from the above description, the leadless chip component according to the present invention has Sn as a base metal in its outermost layer and Bi, Ag, A binary alloy plating film in which at least one metal element of Cu, Zn, In, and Ni is eutectoid is formed.

By optimizing the ratio of Sn to various eutectoid metals, the external connection terminals subjected to these surface treatments can completely prevent the generation of whiskers and greatly improve the moisture resistance and heat resistance of the plating film. Thus, the wettability of various lead-free solders is not deteriorated due to long-term storage, and the effect of significantly improving the reliability of the solder joint is obtained.

Further, by heating and re-melting the Sn-based binary alloy plating film, recrystallization of the alloy film occurs, and even when the content of the eutectoid metal element is small, generation of whiskers is suppressed. In addition, the heat resistance and the moisture resistance of the alloy film were remarkably improved, and the effect of significantly reducing the deterioration of the solder wettability due to long-term storage and the deterioration of the solder wettability due to the heat history of the mounting process was obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multilayer ceramic capacitor as a leadless chip component according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 dielectric ceramic 2 internal electrode layer 3 external connection terminal layer 4 barrier metal layer 5 Sn-based binary alloy plating film

Claims (8)

[Claims] 1. A barrier metal layer is provided on an external connection terminal layer, and one of metal elements such as Bi, Ag, Cu, Zn, Ni, In based on Sn metal is further provided on the barrier metal layer. A leadless chip component, wherein an external terminal is formed by providing an eutectoid Sn-based binary alloy plating film. 2. The leadless chip component according to claim 1, wherein the Sn-based binary alloy plating film is provided by heating and re-melting. 3. The Sn-based binary alloy plating film is formed of Sn-Bi.
The leadless chip part according to claim 1, wherein the leadless chip part is made of a binary alloy, and has an eutectoid content of Bi in a range of 2 to 10%. 4. The Sn-based binary alloy plating film is formed of Sn-Ag.
The leadless chip part according to claim 1, wherein the leadless chip part is made of a binary alloy and has an eutectoid amount of Ag in a range of 1 to 5%. 5. The Sn-based binary alloy plating film is formed of Sn—Cu.
The leadless chip part according to claim 1, wherein the leadless chip part is made of a binary alloy, and the eutectoid content of Cu is in a range of 0.5 to 10%. 6. The Sn-based binary alloy plating film is formed of Sn—Zn.
The leadless chip part according to claim 1, wherein the leadless chip part is made of a binary alloy and has an eutectoid content of Zn in a range of 3 to 10%. 7. The Sn-based binary alloy plating film is formed of Sn-In.
The leadless chip part according to claim 1, wherein the leadless chip part is made of a binary alloy and has an eutectoid content of In in a range of 0.5 to 5%. 8. The Sn-based binary alloy plating film is formed of Sn—Ni.
The leadless chip part according to claim 1, wherein the leadless chip part is made of a binary alloy and has an eutectoid content of Ni in a range of 0.5 to 3%.