JPH11238840A - Lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the reliability of a bonding of lead parts in a semiconductor device to a packaging board, such as a printed wiring board, without using a Pb film by a method wherein a Pd film formed on the surface of an Sn-Ni alloy film consisting of an Sn film and an Ni film is formed on the surface of a base material consisting of a Cu material. SOLUTION: A lead frame base material 10 is constituted of a Cu material. An Sn-Ni alloy film 12 containing 50 wt.% of Sn is formed on the surface of the base material 10 in a chickness of 1 to 2 μm of thereabouts by plating and moreover, a Pd film 14 is formed on the surface of the film 12 in a thickness of 0.1 μm or thereabouts by plating. In such a way, by providing the film 12 between the base material 10 and the film 14, the good adhesiveness of the Pd film 14 to the base material 10 is ensured. As a result, the corrosion resistance and wear resistance of a lead frame can be enhanced. Accordingly, the reliability of a bonding of lead parts in a semiconductor device to a packaging board can be enhanced. Moreover, in the case where the alloy film 12 is formed on the surface of the base material as a base film, the better adhesiveness of the film 12 is obtained than the case where an Ni film is formed on the surface of the base material in the same film thickness as that of the alloy film as a base film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lead frame, and more particularly to a lead frame provided with a metal film made of Pd or a metal film made of an alloy containing Pd.

[0002]

2. Description of the Related Art In general, as shown in FIG. 6, a lead frame on which a semiconductor element is mounted has a die pad support 44 to which a die pad 40 on which a semiconductor element is mounted is connected to a center, and a plurality of lead portions (inner parts). And a plurality of outer leads 42b) and a plurality of metal ribbons. This lead frame has a role of heat dissipation, structure retention, and the like, in addition to a current conduction function. From these facts, the lead frame has a high electric conductivity and a high heat conductivity.
A material or a Cu material (a metal composed of Cu and a trace amount of another metal component) is used, and is selected according to the purpose.

Conventionally, in a semiconductor device, a semiconductor element is mounted on a lead frame, sealed with resin or ceramic, an outer lead serving as an external terminal of the semiconductor device is separated from the frame, and then Sn or Sn- is plated or coated. By providing a Pb alloy film, bonding reliability is improved, and the outer lead is manufactured by bending the outer lead into a desired shape. Such a semiconductor device is mounted by soldering a terminal portion to a joint terminal portion of a mounting board.

In recent years, methods that do not use Pb in consideration of the influence on the environment and the human body have been proposed. Among them, a method in which a Pd film is formed on a lead frame in advance and then a semiconductor device is assembled to form Sn or Sn on the surface of a terminal portion. Sn-Pb
Methods that do not require the formation of an alloy film have been spotlighted.

When a Cu material is used in this method, as shown in FIG. 7, a Ni film 70 having a film thickness of about 1 μm is formed on the surface of the Cu material 60 as a barrier metal for suppressing generation of a local battery by plating. Then, a method of forming two metal films on which a Pd film 64 having a thickness of about 0.1 μm is formed, or as shown in FIG. Film 62 and thickness 0.1 μm
Au film 66 having a thickness of several nm after forming the Pd film 64
Have been proposed to further improve the bonding reliability between the lead portion and the substrate.

[0006]

However, Pd and Au are expensive, and there is a problem that the cost is increased if the film is formed too thick.

[0007] Further, there is a defect that the bonding reliability (or mounting reliability) with a mounting substrate such as a printed wiring board is inferior to the case of using Sn or Sn-Pb alloy. Further, in a bending process of a terminal portion in a semiconductor device manufacturing process, a metal film having good corrosion resistance such as an Au film on the surface of the terminal portion is peeled off, and the terminal portion is partially corroded, thereby impairing bonding reliability. There is.

Further, when the Pd film is provided on the base material made of Fe material, the adhesion and the corrosion resistance are poor and the deterioration is faster than when the Pd film is provided on the base material made of Cu material. There is also a disadvantage that a Pd film cannot be provided on a base material made of an Fe material such as a material.

In view of the above, the present invention provides a lead frame having improved bonding reliability (or mounting reliability) between a lead portion of a semiconductor device and a mounting substrate such as a printed wiring board without using Pb. This is the first object. A second object is to provide a lead frame that can reduce the manufacturing cost. Further, the present invention provides a lead frame provided with a film made of Pd or a Pd alloy on its surface and having good film adhesion and corrosion resistance even when using a Cu material as well as an Fe material as a base material. This is also a third object.

[0010]

In order to achieve the first object, a lead frame according to the first aspect of the present invention comprises a substrate made of a Cu material, and Sn and N formed on the surface of the substrate.
i) and a Pd film formed on the surface of the Sn—Ni alloy film or a Pd film formed with an Au film on the surface.

Since the Sn—Ni alloy film has no leveling effect, minute irregularities are easily formed on the surface, and the adhesion effect is increased by the anchor effect due to the minute irregularities. Therefore, a film made of an Sn—Ni alloy is coated with a Cu material and a Pd film, which are base materials of a lead frame, or A
By providing the Pd film between the Pd film and the u film, the Sn—Ni alloy film adheres well to both the surface of the base material and the Pd film, and functions to prevent the Pd film from peeling. Therefore, it is possible to provide a lead frame with improved bonding reliability of the mounting substrate.

Further, since the film made of the Sn—Ni alloy is used, it is not necessary to increase the thickness of the Pd film in consideration of the thickness of the Pd film peeling off. Even in this case, the same joining reliability as that of the related art can be obtained.
Therefore, there is an advantage that the material cost can be reduced. Also, since the Pd film is favorably maintained on the surface,
Sufficiently good corrosion resistance and wear resistance can be secured. Further, when an Au film is provided on the surface of the Pd film, the thickness of the Au film can be reduced, so that the cost can be reduced accordingly.

[0013] It is to be noted that P on the surface of the Sn-Ni alloy film
Even if the d film is peeled off or cracked for some reason, the Sn-Ni alloy film has better corrosion resistance and wear resistance than the Ni film, so that it is compared with the case where the conventional Ni film is applied. As a result, the life of the terminal can be extended.

Further, since the standard electrode potential of the Sn—Ni alloy is an intermediate value between the standard electrode potential of the Cu material constituting the base material and the standard electrode potential of Pd, the film made of the Sn—Ni alloy is , Cu material which is the base material of lead frame and P
By providing between the Cu film and the Cu material and the Pd film having the Au film formed on the surface, the base material and the Sn—Ni
The occurrence of local batteries between the alloy film and between the Sn—Ni alloy film and the Pd film or the Pd film having the Au film formed on the surface is suppressed, and the corrosion caused by this is suppressed. it can. Therefore, the life of the lead frame can be made longer than before, and the bonding reliability of the terminal portion of the semiconductor device can be secured for a long period.

According to a second aspect of the present invention, there is provided a lead frame, comprising: a base material made of a Cu material; and a base film made of a Ni film or a Sn—Ni alloy film made of Sn and Ni formed on the surface of the base material. A Pd-Au alloy film formed of Pd and Au and formed on the surface of the base film.

That is, according to the invention of claim 2, Pd and A
is contained in the same film as the Pd-Au alloy film, so that even if the Pd-Au alloy film is slightly peeled off in the terminal bending step or the like, the remaining Pd-Au alloy film has corrosion resistance and wear resistance. Is good.
Therefore, when the Pd film and the Au film are formed to overlap with each other, the bonding reliability can be sufficiently ensured as compared with the case where the Au film serving as the outermost surface is peeled off. Further, when the film forming process is performed using Pd
There is also an advantage that the cost can be reduced because it is smaller than in the case where the film and the Au film are formed in an overlapping manner.

In the case where the Sn—Ni alloy film is provided as a base film of the Pd—Au alloy film, the bonding reliability can be improved as described in claim 1 and the bonding reliability can be improved. Pd-A for similar
Since the thickness of the u alloy film can be made smaller than the total thickness of the conventional Pd film and Au film, there is also an advantage that the material cost can be reduced.

Further, the lead frame of the invention according to claim 3 is a lead frame made of Fe material or Cu material, a Cu—Sn alloy film made of Cu and Sn formed on the surface of the base material, Sn and N formed on the surface of the Sn alloy film
The substrate includes a base film made of a Sn—Ni alloy film or a Ni film made of i, and one of a Pd—Au alloy film, a Pd film, and a Pd film having an Au film on its surface.

That is, according to the third aspect of the present invention, the Fe material and the Cu material constituting the base material of the lead frame, and the film (ie, the Pd—Au alloy film or the Pd film or the surface) to be the outermost surface of the lead frame. Pd with Au film
In addition to providing a base film made of a Sn—Ni alloy film or a Ni film between the base film and the base film, the standard electrode potential is made of a Cu—Sn alloy having a value between the base material and the base film. Since the film is provided, between the substrate and the Cu-Sn alloy film,
When the Sn—Ni alloy film is used as the base film,
The standard electrode potential difference between the Ni alloy film and C and the u-Sn alloy film, and between the Ni film and the Cu-Sn alloy film when the Ni film is used as the base film, is Cu-Sn alloy film. The potential difference becomes smaller than the standard electrode potential difference when a base film is provided on the surface of the base material. As a result, generation of a local current between the base material and the base film is suppressed, corrosion due to this is prevented, and corrosion resistance can be improved.

In particular, when an Fe material having a larger standard electrode potential difference from a base film than a Cu material is used as a base material, a dissimilar metal contact portion between the Fe material and the Sn—Ni alloy film, or F
Since the standard electrode potential difference at the dissimilar metal contact portion between the e-material and the Ni film is within a range that suppresses the generation of a local battery, 42 alloy materials and the like which could not be provided due to severe electric corrosion in the past. A Pd-containing metal such as a Pd film or a Pd-Au alloy film can be provided on the Fe base material. Therefore, the usable range of the base material of the Fe material can be expanded as compared with the related art.

If the Sn—Ni alloy film is selected as the underlayer, the bonding reliability can be improved as in the first aspect, and the film provided on the outermost surface when the bonding reliability is improved. There is an advantage that the film thickness can be made thinner than before. Further, if a Pd-Au alloy film is selected as the film provided on the outermost surface, corrosion resistance and abrasion resistance are maintained as compared with the case where the Pd film and the Au film are formed in an overlapping manner as in claim 2, and sufficient Thus, the bonding reliability can be ensured.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

(First Embodiment) The lead frame base material 10 shown in FIG. 1 is made of a Cu material (a metal comprising Cu and a trace amount of another metal component of about 10 wt%). In the first embodiment, the Sn—Ni alloy film 12 containing 50 wt% of Sn is formed on the surface of the lead frame base material 10.
Of about 1 to 2 μm by plating, and a Pd film 14 is applied to the surface by about 0.1 μm by plating.

In the first embodiment, since the Sn—Ni alloy film 12 is provided between the lead frame base material 10 and the Pd film 14, good adhesion is ensured. And the reliability of bonding with the mounting board can be improved.

When the Sn—Ni alloy film 12 is applied as the base film, better film adhesion is obtained than when the Ni film is used as the base film to have the same thickness as the Sn—Ni alloy film 12. Therefore, when the thickness of the Sn—Ni alloy film 12 is about 1 to 2 μm, even if the thickness of the Pd film 14 is made thinner than before, it is possible to obtain the same bonding reliability as before. That is, even if the thickness of the Pd film is not taken into consideration in consideration of the thickness of the Pd film to be peeled off, the same bonding reliability as that of the related art can be obtained. Can be lowered.

(Second Embodiment) FIG. 2 shows a lead frame having a structure in which an Au film 16 having a thickness of several nm is formed on the surface of a Pd film which is a surface film of the lead frame shown in the first embodiment. Is shown. In the case of this configuration, the joint reliability can be further improved by the good corrosion resistance and wear resistance of the Sn—Ni alloy film 12 and the corrosion resistance of the Au film.

The thickness of the Sn—Ni alloy film 12 is 1 to
When the thickness is about 2 μm, even if the thickness of the Pd film 14 is reduced, the same bonding reliability as that of the related art can be obtained. That is, even if the thickness of the Pd film and the Au film is not taken into consideration in consideration of the thickness of the Pd film and the Au film to be separated, the same bonding reliability as that of the related art can be obtained. Can be made thinner, and costs can be reduced.

(Third Embodiment) The lead frame substrate 10 shown in FIG. 3 is made of a Cu material. In the third embodiment, a Ni film 20 is applied to the surface of the lead frame base material 10 by plating to a thickness of about 1 to 2 μm, and Au having a thickness of 0.1 μm is coated on the surface by at least 10 wt.
% Pd-Au alloy film 18 is applied by plating.

According to this configuration, Pd and Au are converted to Pd-
Since the Pd-Au alloy film 18 is formed at the same time as the Au alloy film 18, even if the surface film portion of the Pd-Au alloy film 18 is slightly peeled off in the terminal bending step or the like, neither Pd nor Au is attached to the film remaining in close contact with the lead frame base material. included. Therefore, when the Pd film 14 and the Au film 16 are formed so as to overlap with each other, Au which is the outermost surface is formed.
Corrosion resistance and abrasion resistance can be maintained better than when the film 16 is peeled off, and the bonding reliability thereof can be sufficiently ensured.

Needless to say, when the Pd film 14 and the Au film 16 are formed to overlap each other, two film forming steps are necessary. However, as in the third embodiment, Pd and Au are converted to a Pd-Au alloy film. In the case where they are formed simultaneously as 18, there is also an advantage that the cost can be reduced because only one process is required.

(Fourth Embodiment) FIG. 4 shows the lead frame shown in the third embodiment in which Sn having a thickness of about 1 to 2 μm and containing 50 wt% of Sn is used instead of the Ni film 20.
-The Ni alloy film 12 is formed by plating. In the case of this configuration, in addition to the effects obtained in the third embodiment, the Pd-A of the surface of the Sn—Ni alloy film 12 is improved due to the good corrosion resistance and wear resistance of the Sn—Ni alloy film 12.
Even if the thickness of the u-alloy film 18 is reduced, it is possible to obtain the same level of bonding reliability as the conventional one.

That is, even if the thickness of the Pd film is not increased in consideration of the thickness of the Pd film to be peeled off, the same bonding reliability as that of the related art can be obtained, so that the thickness of the Pd film can be reduced accordingly. The material cost can be reduced.

(Fifth Embodiment) The lead frame base material 30 shown in FIG. 5 is made of an Fe--Ni alloy containing 42 wt% of Ni as an Fe material, that is, a 42 alloy material. In the fifth embodiment, a Cu—Sn alloy film 32 having a thickness of about 1 to 3 μm is formed on the surface of the lead frame base material 30 and Sn having a thickness of about 1 to 2 μm is formed on the surface.
A Sn—Ni alloy film 12 containing 0 wt% is applied by plating, and Au is further coated on the surface with at least 10 wt%.
The Pd-Au alloy film 18 is applied by plating so as to have a thickness of about 0.1 μm.

The Cu—Sn alloy film 32 provided between the lead frame substrate 30 and the Sn—Ni alloy film 12 allows the lead frame substrate 30 and the Cu—Sn alloy film 32 and the Sn—Ni alloy film Since the standard electrode potential difference between the second electrode 12 and the Cu—Sn alloy film 32 becomes smaller, generation of local current is suppressed, corrosion caused by this is prevented, and corrosion resistance is increased.

The Sn—Ni alloy film 12 is used as a base film.
Is used, the joining reliability can be improved, and even if the thickness of the Pd-Au alloy film 18 on the surface of the Sn-Ni alloy film 12 is reduced, the same joining reliability as that of the related art can be obtained. Can be reduced.

Further, since the Pd-Au alloy film 18 is provided on the outermost surface, even if the surface film portion of the Pd-Au alloy film 18 is slightly peeled off in a terminal bending step or the like, the corrosion resistance and wear resistance can be maintained well. , The joint reliability can be sufficiently ensured. Of course, Pd as a Pd-Au alloy film
Since Au and Au are formed in the same film, there is also an advantage that the film formation process can be performed in one step, and the cost can be reduced accordingly.

In this embodiment, the ratio of Sn—Ni alloy to Cu—Sn alloy at a specific ratio and P
The combination of the ratios of the d-Au alloy is not limited, and the ratio and the combination can be appropriately selected as necessary in consideration of the coefficient of thermal expansion and the like.

Further, in the fifth embodiment, F
Although a 42 alloy material as the e material was used, another Fe material may be used. Further, as another base material, a Cu material can be used as in the above-described first to fourth embodiments.

In the fifth embodiment, when a Pd-Au alloy film is formed on a base made of a 42 alloy material, a Cu-Sn alloy film is formed on the surface of the base material, and an Sd alloy is formed on the surface of the Cu-Sn alloy film.
The Pd-Au alloy film is applied after the n-Ni alloy film is applied. However, as another configuration, a Cu-Sn alloy film of about 1 μm and a Ni film of about 1 μm are formed on a surface of a base material made of a 42 alloy material. , A Pd-Au alloy film of about 0.1 μm may be provided by plating.

A Cu—Sn alloy film of about 1 μm, a Ni film of about 1 μm,
Even if a Pd film of about 0.1 μm is provided by plating, a Cu-Sn alloy film of about 1 μm
Ni film of about 1 μm, Pd film of about 0.1 μm, several nm
May be provided by plating.

Further, about 42 μm of Cu
-Sn alloy film, Sn-Ni alloy film of about 1 μm, 0.1
Even if a Pd film of about μm is provided by plating,
42 alloy material, Cu-Sn alloy film of about 1 m, 1 m
An Sn—Ni alloy film of about 0.1 μm, a Pd film of about 0.1 μm, and an Au film of several nm may be provided by plating.

In the first to fifth embodiments described above, the Cu material may be an alloy composed of copper and a trace amount of a metal component.
and a Cu-Zr alloy composed of Cu and Zn, and the like.

In the first, second, fourth and fifth embodiments, the Sn—Ni alloy film 12
Although an Sn—Ni alloy containing 50 wt% of Sn is used as the alloy, the present invention is not limited to the Sn—Ni alloy having this composition, and an Sn—Ni alloy containing about 30 to 70 wt% of Sn can be used.

In the third, fourth, and fifth embodiments, the Pd—Au alloy constituting the Pd—Ni alloy film 18 is a Pd—Au alloy containing at least 10 wt% of Au.
Although an alloy is used, the present invention is not limited to a Pd-Au alloy having this composition, but a Pd-Au alloy containing Pd in an amount of about 30 to 70 wt%.
Alloys can be used.

[0045]

As described above, according to the first aspect of the present invention, Sn-N is applied to both the surface of the substrate and the Pd film.
This prevents the Pd film from peeling off due to good adhesion of the i-alloy film, thereby improving the bonding reliability.

According to the second aspect of the present invention, Pd and Au are contained in the remaining film even if the surface film portion of the Pd-Au alloy film is slightly peeled off in the terminal bending step or the like.
When the d film and the Au film are formed on top of each other,
Corrosion resistance and abrasion resistance are maintained as compared with the case where the u film is peeled off, and there is an effect that the joint reliability can be sufficiently ensured.

Further, according to the third aspect of the present invention, generation of a local current between the base material and the base film is suppressed, thereby preventing corrosion caused by the local current and further improving the corrosion resistance. . As a result, there is an effect that a Pd film or a Pd alloy film, which is not provided on a base material made of an Fe material such as a 42 alloy material, as well as a Cu material, can be provided.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a lead frame according to a first embodiment of the present invention.

FIG. 2 is a partial sectional view of a lead frame according to a second embodiment of the present invention.

FIG. 3 is a partial sectional view of a lead frame according to a third embodiment of the present invention.

FIG. 4 is a partial sectional view of a lead frame according to a fourth embodiment of the present invention.

FIG. 5 is a partial sectional view of a lead frame according to a fifth embodiment of the present invention.

FIG. 6 is a top view showing a lead frame.

FIG. 7 is a partial sectional view of a conventional lead frame.

FIG. 8 is another partial sectional view of a conventional lead frame.

[Explanation of symbols]

 10, 30 Lead frame base material 12 Sn-Ni alloy film 12 14 Pd film 16 Au film 18 Pd-Au alloy film 20 Ni film 32 Cu-Sn alloy film

Claims (3)

[Claims] 1. A substrate made of a Cu material, and an Sn— layer formed on the surface of the substrate and made of Sn and Ni.
A lead frame comprising: a Ni alloy film; and a Pd film formed on the surface of the Sn—Ni alloy film or a Pd film formed on the surface with an Au film. 2. A substrate formed of a Cu material, a base film formed on a surface of the base material and formed of a Ni film or a Sn—Ni alloy film formed of Sn and Ni, and a base film formed on a surface of the base film. P consisting of Pd and Au
A lead frame comprising: a d-Au alloy film. 3. A base material made of an Fe material or a Cu material, and a Cu-based material formed on the surface of the base material and made of Cu and Sn.
A Sn alloy film; a Sn—Ni alloy film composed of Sn and Ni formed on the surface of the Cu—Sn alloy film or a base film composed of a Ni film; a Pd—Au alloy film, a Pd film, and an Au film on the surface A lead frame comprising: any one of the Pd films comprising: