JPH11251503A - Electronic part and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solder parts easily firmly, by depositing a metal layer made of Sn containing Bi less than predetermined in percent on an electrode lead wire to be connected to the outside. SOLUTION: A metal layer made of Sn containing by weight less than 4% Bi is deposited on an electrode lead wire 5 connected to the outside as an outermost metal layer 6. A semiconductor element is die-bonded on a Cu lead frame and is provided with a wiring connected to an external electrode. An underlayer Ni-plated film is formed on the electrode lead wire 5 to be connected to the outside of the semiconductor device subjected to plastic sealing and lead forming, and then Bi is deposited on the metal underlayer as an Sn-Bi alloy film. This can make it possible to easily mount electronic parts on a printed substrate or a circuit substrate with solder at a low temperature and to improve the reliability of the portion bonded with solder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component such as a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a lead-tin (Pb-Sn) -based solder layer is previously formed on an electrode lead wire for external connection in a semiconductor device, so that the semiconductor device can be easily mounted on a printed circuit board or a circuit board. Can be attached by soldering. Therefore, most semiconductor devices contained Pb in the electrode lead wires for external connection. The Pb-Sn-based solder layer was formed by plating or dipping.

[0003]

However, soldering a semiconductor device using Pb-containing solder is not preferable in terms of environmental measures. Therefore, in recent years, a semiconductor device that does not require Pb-free soldering after assembling by preliminarily attaching and forming palladium (Pd), which is an easily solderable metal, to a lead frame has been introduced. (For example, Nikkei Electronics: no. 622, p17, 1
994). However, when Pd plating is applied to an iron-based material, a corrosion reaction occurs due to a potential difference, and there is a problem that the lead frame material is limited to a copper material.

The present invention provides an electronic component which is preferable in terms of environmental measures, is not limited to a lead made of copper, and can be easily and firmly soldered, and a method of manufacturing the same.

[0005]

According to the electronic component of the present invention, Bi is contained in Sn at 4% by weight in the electrode lead wire for external connection.
Characterized in that a metal layer containing less than 10% is formed by adhesion. According to the electronic component of the first aspect, since the metal layer does not contain Pb, it is preferable from an environmental measure, and
n is a material containing Bi and its application is not limited to a lead made of a copper material. In addition, Bi can lower the melting point of Sn serving as an adhesive, and can easily attach an electronic component to a printed circuit board or a circuit board by soldering at a low temperature. In addition, the metal layer can have sufficient mechanical strength, has little deterioration against thermal fatigue, and can be firmly soldered to printed circuit boards and circuit boards.
The reliability of the solder joint can be improved.

In the electronic component according to the second aspect of the present invention, the external connection electrode lead wire contains less than 4% by weight of Bi in Sn, Ag and Cu.
In a total amount of less than 4% by weight. According to the electronic component of the present invention, Pb is not contained in the metal layer, which is preferable from an environmental measure. Further, the electronic component contains Bi in Sn and its application is not limited to a lead made of copper. In addition, Bi can lower the melting point of Sn serving as an adhesive,
Electronic components can be easily attached to a printed circuit board or a circuit board by soldering at a low temperature. In addition, the metal layer can have sufficient mechanical strength, is less deteriorated against thermal fatigue, can be firmly soldered to a printed circuit board or a circuit board, and can increase the reliability of a solder joint. . Further, by including Ag and Cu in the metal layer, soldering is further facilitated.

According to a third aspect of the present invention, there is provided an electronic component in which a metal layer having a multilayer structure of a simple substance or an alloy of Sn, Bi, Ag, and Cu is attached to an external electrode lead wire, and the overall composition of the metal layer Wherein Bi is less than 4% by weight, Ag and Cu are less than 4% by weight in total, and the balance is Sn. According to the electronic component according to the third aspect, since the metal layer does not contain Pb, it is preferable for environmental measures, and Sn
And Bi is contained therein, and the application object is not limited to the lead of the copper material. In addition, Bi can lower the melting point of Sn serving as an adhesive, and can easily attach an electronic component to a printed circuit board or a circuit board by soldering at a low temperature. In addition, the metal layer can have sufficient mechanical strength, is less deteriorated against thermal fatigue, can be firmly soldered to a printed circuit board or a circuit board, and can increase the reliability of a solder joint. . Further, by including Ag and Cu in the metal layer, soldering is further facilitated.

According to a fourth aspect of the present invention, in the electronic component according to the first, second, or third aspect, the metal layer attached to the external connection electrode lead wire is formed on a base metal layer made of Cu or Ni. It is characterized by having been done. According to the electronic component of the fourth aspect, the first aspect
Alternatively, in addition to the function of the second or third aspect, by forming the metal layer on the underlying metal layer made of Cu or Ni, it is possible to obtain a junction with little change over time.

According to a fifth aspect of the present invention, there is provided a method of manufacturing an electronic component according to the first, second, third or fourth aspect, wherein the current density is 1.5 A / dm ² or less by an electroplating method. It is characterized in that a layer is formed by adhesion. According to the method of manufacturing an electronic component according to claim 5,
By forming the metal layer by electroplating with a current density of 1.5 A / dm ² or less, the particle size of the metal layer adhered to the external connection electrode lead wire is reduced, and the circuit of the external connection electrode lead wire is reduced. Soldering to a board or a printed board can be easily performed.

According to a sixth aspect of the present invention, there is provided a method of manufacturing an electronic component according to the first, second, third, or fourth aspect, wherein an annealing process is performed after a metal layer is formed. Is what you do. According to the electronic component manufacturing method of the present invention, by performing an annealing treatment after the formation of the metal layer, Sn diffuses into the material to form an alloy layer, thereby reducing the Sn concentration on the surface and preventing whiskers. be able to.

According to a seventh aspect of the present invention, there is provided a method of manufacturing an electronic component according to the first, second, third, or fourth aspect, wherein the Au layer is formed after the metal layer is formed. It is a feature. According to the method for manufacturing an electronic component according to the seventh aspect, it is possible to prevent oxidation of the external connection electrode lead wire, and to easily attach the external connection electrode lead wire to a circuit board or a printed board by soldering. be able to.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An electronic component according to the present invention has an outermost metal layer adhered to an electrode lead wire for external connection.
Instead of the conventional Pb-Sn-based solder, an Sn-Bi-based alloy obtained by mixing bismuth (Bi) as a metal for lowering the melting point with Sn (melting point: 232 ° C) mainly serving as an adhesive is used. Further, Ag and Cu were selected as additive metals for facilitating soldering of the external connection electrode lead wires. That is, a Sn—Bi-based alloy is used as the outermost metal layer of the external connection electrode lead wire of the electronic component, and Ag is used.
And Cu are added. In addition, about Ag and Cu,
Either one or both of them may be added, or neither may be added. When adding
At the same amount, Ag is more effective than Cu.

The reason why the addition of Ag or Cu facilitates soldering is that Ag or Cu is easily dissolved in Sn. That is, Ag and Cu on the lead wire side are easily dissolved in Sn in the solder paste at the time of soldering, and soldering is facilitated. On the other hand, since the content of Bi is as small as less than 4% by weight, the solderability is improved by forming an Au plating film to prevent the oxidation of Sn.

Here, the reason why the content of Bi is set to less than 4% by weight is that if the content is more than 4% by weight, plating cracks in which the base material of the electrode lead wire is visible during bending (see Table 1). ).

[0015]

[Table 1]

When the base material of the electrode lead is visible, the base material is oxidized, the bonding with the solder paste becomes insufficient, and the bonding strength is greatly affected. Therefore, the Bi content greatly affects the reliability of the solder bonding portion. Affect. In addition, at 3% by weight in Table 1, it is a mere crack in which the base material is not visible, and there is no particular influence on the reliability of the solder joint. 2 and 3 show the results of the bonding strength test. This joint strength test
This test takes into account the period from when a semiconductor package is actually manufactured to when it is mounted by a set manufacturer. FIG.
Is a case where the material of the electrode lead wire for external connection is iron-based, and when 10% of Bi is added, the bonding strength is greatly reduced. FIG. 3 shows a copper-based material, and the current Sn-Pb
When the content of Bi exceeds 4%, the bonding strength decreases. The "after mount" in the figure is an example in which a semiconductor package is manufactured, mounted immediately after that, and the bonding strength is measured. Other pre-processing assumes storage from manufacturing to mounting.

In order to improve solderability, at least one of Ag and Cu is added within a total range of less than 4% by weight, such as less than 3% by weight of Ag and about 1% by weight of Cu. did. Also, for example, Cu may be added to less than 4% by weight to make 0% by weight of Cu, or Cu may be added to less than 4% by weight to make Ag to 0% by weight. If the total amount of addition is the same, the effect is higher when Ag is increased.

The reason why the addition amount of Ag and Cu is less than 4% by weight is that if the addition amount is more than 4% by weight, the precipitation becomes faster, the surface becomes uneven and rough, and an electrical short failure occurs due to the migration phenomenon. This is because the effect of improving soldering becomes weaker. When a Sn-Bi metal layer is formed on the external connection electrode lead wire by a dipping method (penetration method), the metal layer is easily oxidized at the time of adhesion formation, so it is better to add Ag and Cu. When a metal layer is formed by electroplating, electroless plating, or the like, oxidation of the metal layer during adhesion formation is small, and Ag and C
It is not necessary to add u. However, Ag and Cu are preferably added because they may be oxidized when left for a long time or when connected to a substrate in a later step.

In addition, when forming on the electrode lead wire for external connection, not only one alloy layer but also S
A metal layer having a multilayer structure such as a simple substance or an alloy of n, Bi, Ag, and Cu may be used. In this case, the metal layers are melted and mixed at the time of soldering the electrode lead wires for external connection, resulting in a uniform composition. Before the metal layer is attached to the external connection electrode lead, Cu
Alternatively, by forming a base metal layer of Ni or the like and attaching and forming a metal layer on the base metal layer, it is possible to achieve a junction with little change with time. In other words, below the underlying metal layer (Ni or Cu) is generally an Fe / Ni alloy or Cu. This Fe / Ni alloy or Cu
Deterioration (formation or oxidation of a compound) due to the progress of the process, the adhesion of the metal layer is deteriorated, and cracks may be generated at the joints due to aging, leading to disconnection. Such a problem can be avoided by providing a base metal layer.

As a method of manufacturing an electronic component, a metal layer is electroplated under a current density of 1.5 A / dm ² or less. The current density is set to 1.5 A / dm ² or less because the particle size changes depending on the current density, and the solderability deteriorates. In other words, when the current density is large, the particle diameter becomes large and the solderability deteriorates, and the current density becomes 1.5 A / d
By setting m ² or less, the particle diameter of the particles constituting the metal layer adhered to the external connection electrode lead wire can be reduced, and as a result, the external connection electrode lead wire can be easily soldered. Become.

The above is summarized as follows. That is, a metal layer containing less than 4% by weight of Bi in Sn as an outermost metal layer is formed on the electrode lead wire for external connection by adhesion, that is, covered. Then, the metal layer containing less than 4% by weight of Bi in Sn further contains Ag in a range of less than 4% by weight, or contains Cu in a range of less than 4% by weight, or a total of less than 4% by weight. It contains Ag and Cu in the range. Further, since the Bi content is reduced, an annealing process is performed to prevent whiskers, and an Au film is formed by adhesion for the purpose of improving solderability. Note that an Au film is attached and formed within 0.1 μm or less from the unit atomic layer. The purpose of depositing the Au film is to reduce the oxidation of Sn-Bi,
The reason why the adhesion is formed between the unit atomic layer and 0.1 μm or less is to prevent the Au film from becoming thick and increasing the cost, and 0.1 μm or less has sufficient oxidation resistance. Also, the content range of Ag and / or Cu is less than 4% by weight, which means more than 0% by weight and less than 4% by weight.

Here, the action of the addition of Ag and Cu will be described. The configuration of Ag + Cu solves the following three problems of Sn oxidation progress in the order of steps, and also solves four problems of solderability after Sn oxidation comprehensively. A: At the time of forming a metal layer A1: Dipping method (Sn is easily oxidized because it is immersed in a molten material) To prevent the oxidation of Sn, less than 4% by weight of Ag + Cu is contained. Ag and Cu may be used alone. The effect of preventing oxidation is higher for Ag if the amount is the same.

A2: Electroplating method (Sn is less oxidized) Ag + Cu is desirably contained in consideration of the post-process. B: From the time the lead is manufactured until it is actually used,
In a long-term test of 85 ° C / 85% / 16 hours, equivalent to one year's worth of daily life,
Oxidation is observed in Sn of the lead metal layer. To prevent the oxidation, it is preferable to contain less than 4% by weight of Ag + Cu. Ag
And Cu may be used alone. The effect of preventing oxidation is higher for Ag if the amount is the same.

C: Problems when soldering electronic components to a substrate or the like C1: The solder paste and Sn of the lead metal layer are oxidized.
To prevent the oxidation, it is preferable to contain less than 4% by weight of Ag + Cu. Ag and Cu may be used alone. The effect of preventing oxidation is higher for Ag if the amount is the same. C2: If Sn is oxidized, it is difficult to solder the electronic component with a solder paste, and the reliability is reduced. As a solution, it is preferable to contain less than 4% by weight of Ag + Cu.
Ag and Cu may be used alone. Ag + Cu acts as follows. In other words, Ag + Cu in the lead metal layer dissolves in Sn in the solder paste, and even if the Sn is oxidized, soldering becomes easy, the adhesion strength between the lead, the substrate and the solder paste is high, and the reliability is improved.

As described above, the effect of Ag + Cu is finally as described in the section of C2.
The antioxidant effect in the steps of 1, B and C1 is also combined. In other words, Sn in each term of A, B, C
Prevention of oxidation means that soldering is easy, so the bonding strength between the lead, the board and the solder paste is high,
Reliability is improved.

[0026]

Next, a specific embodiment will be described with reference to FIG. FIG. 1 shows a front view of a semiconductor device as an electronic component, wherein 1 is a semiconductor element, 2 is a metal wire, 3 is a die bonding agent, 4 is a molding resin, 5 is an external connection electrode lead wire, and 6 is This is a metal layer for facilitating attachment to a printed circuit board or a circuit board.

Example 1 A semiconductor element is die-bonded on a copper lead frame, wiring to external electrodes is performed, and the thickness of the external connection electrode lead wire of the semiconductor device after resin sealing and lead processing is completed. 1 to 3 μm underlying Ni plating film (underlying metal layer)
Is formed, a Sn—Bi alloy film (metal layer) containing 2% by weight of Bi is further formed on the underlying metal layer with a current density of 1.0 A.
/ Dm ² and a thickness of 10 μm.

Embodiment 2 A semiconductor element is die-bonded on a lead frame made of an iron-nickel material, wiring with an external electrode is also performed, and an external connection electrode lead wire of a semiconductor device after resin sealing and lead processing is completed. After forming an underlying Cu plating film (underlying metal layer) having a thickness of 1 to 2 μm, a Sn—Bi alloy film (metal layer) containing 2% by weight of Bi was further formed on the underlying Cu plating film with a current density of 1.5 A / dm. ² and formed to a thickness of 12 μm.

Example 3 In the same manner as in Example 1, a base Ni film (base metal layer) was formed on an external connection electrode lead wire of a copper material after resin encapsulation and lead processing was completed, and then the temperature was reduced to 280 degrees. Dipping was performed in the heated Sn-Bi-Ag (85-10-5% by weight), and a metal layer having a thickness of 20 μm was deposited.

[0030]

According to the electronic component according to the first aspect, since the metal layer does not contain Pb, it is preferable from the viewpoint of environmental measures.
n is a material containing Bi and its application is not limited to a lead made of a copper material. In addition, Bi can lower the melting point of Sn serving as an adhesive, and can easily attach an electronic component to a printed circuit board or a circuit board by soldering at a low temperature. In addition, the metal layer can have sufficient mechanical strength, has little deterioration against thermal fatigue, and can be firmly soldered to printed circuit boards and circuit boards.
The reliability of the solder joint can be improved.

According to the electronic component according to the second aspect, since the metal layer does not contain Pb, it is preferable from an environmental measure, and Sn
And Bi is contained therein, and the application object is not limited to the lead of the copper material. In addition, Bi can lower the melting point of Sn serving as an adhesive, and can easily attach an electronic component to a printed circuit board or a circuit board by soldering at a low temperature. In addition, the metal layer can have sufficient mechanical strength, is less deteriorated against thermal fatigue, can be firmly soldered to a printed circuit board or a circuit board, and can increase the reliability of a solder joint. . Further, by including Ag and Cu in the metal layer, soldering is further facilitated.

According to the third aspect of the present invention, since the metal layer does not contain Pb, it is preferable in terms of environmental measures, and Sn
And Bi is contained therein, and the application object is not limited to the lead of the copper material. In addition, Bi can lower the melting point of Sn serving as an adhesive, and can easily attach an electronic component to a printed circuit board or a circuit board by soldering at a low temperature. In addition, the metal layer can have sufficient mechanical strength, is less deteriorated against thermal fatigue, can be firmly soldered to a printed circuit board or a circuit board, and can increase the reliability of a solder joint. . Further, by including Ag and Cu in the metal layer, soldering is further facilitated.

According to the electronic component of the fourth aspect, in addition to the effects of the first, second, or third aspect, the metal layer is formed on the underlying metal layer made of Cu or Ni, so that the change with time can be reduced. Less bonding can be obtained. According to the method of manufacturing an electronic component according to claim 5, the metal layer is formed by an electroplating method having a current density of 1.5 A / dm ² or less, so that the particles of the metal layer adhere to the external connection electrode lead wire. The diameter is reduced, and the electrode lead wires for external connection can be easily soldered to a circuit board or a printed board.

According to the electronic component manufacturing method of the present invention, the annealing is performed after the formation of the metal layer, so that Sn diffuses into the material to form an alloy layer, and the S on the surface is formed.
The whisker can be prevented by decreasing the n concentration. According to the method for manufacturing an electronic component according to the seventh aspect, it is possible to prevent oxidation of the external connection electrode lead wire, and to easily attach the external connection electrode lead wire to a circuit board or a printed board by soldering. be able to.

[Brief description of the drawings]

FIG. 1 is a front view of an electronic component according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a Bi content in a Sn—Bi alloy and a joining strength in an iron-based material.

FIG. 3 is a characteristic diagram showing a relationship between a Bi content in a Sn—Bi alloy and a bonding strength in a copper-based material.

[Explanation of symbols]

 5 Electrode lead wire for external connection 6 Metal layer

Continuing from the front page (72) Inventor Tomizo Sawada 1-1, Sachimachi, Takatsuki-shi, Osaka Prefecture Inside Matsushita Electronics Corporation (72) Inventor Kazuhiro Aoi 1-1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics Corporation Inside

Claims (7)

[Claims] 1. An electrode lead wire for external connection;
An electronic component characterized in that a metal layer containing less than 4% by weight is formed by adhesion. 2. An electrode lead wire for external connection;
An electronic component, wherein a metal layer containing less than 4% by weight and a total of less than 4% by weight of Ag and Cu is deposited. 3. An electrode lead wire for external connection, wherein Sn, B
A metal layer having a multilayer structure of a simple substance or an alloy of i, Ag, and Cu is adhered and formed.
i is less than 4% by weight, Ag and Cu are less than 4% by weight in total,
An electronic component, the balance being Sn. 4. The metal layer attached to the external connection electrode lead wire is formed on a base metal layer made of Cu or Ni.
Or the electronic component according to claim 3. 5. The method according to claim 1, 2 or 3.
5. The method for manufacturing an electronic component according to claim 4, wherein the metal layer is formed by electroplating having a current density of 1.5 A / dm ² or less. 6. The method according to claim 1, wherein said first and second means are different from each other.
5. The method for manufacturing an electronic component according to claim 4, wherein an annealing process is performed after the metal layer is attached and formed. 7. The method according to claim 1, 2 or 3.
5. The method for manufacturing an electronic component according to claim 4, wherein after forming the metal layer, an Au film is formed.