JPH09291377A - Article with coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance adhesion between layers and to prevent a coating layer from being stripped off at the time of coating the copper alloy substrate of a lead frame with an Ni layer and a Pd layer to improve the corrosion resistance, solderability and bondability when wires are bonded by arranging an Au layer between both layers and forming a diffused layer contg. Ni and Pd. SOLUTION: An Ni plating is applied on the surface of the substrate 11 of a frame to improve the solder wettability, and then gold strike plating including diffusion treatment, Pd plating and further gold strike plating are successively conducted to form a laminated coating. Consequently, the upper face of an Ni layer 14 on the substrate 11 surface is bonded to the Au layer 16 through an Ni-Au diffused layer 15, and further a Pd layer 18 on the Au layer 15 is joined to the Au layer 16 through a Pd-Au diffused layer 17. Accordingly, a multilayer coating film consisting essentially of the Ni layer 14 and Pd layer 18 is firmly joined to the substrate 11, and the stripping and especially that of the Pd layer 18 are prevented when the frame is bent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an article provided with a plating film on a substrate, and more particularly to a lead frame provided with the film on the substrate.

[0002]

2. Description of the Related Art In a lead frame for a semiconductor element, there has been a conventional technique for applying various coatings to a base material in order to improve the bondability at the time of soldering or wire bonding and the corrosion resistance of the lead frame itself. Being developed. For example, Japanese Patent Publication No. 63-49382 discloses N
By stacking the i base plating layer and the Pd layer, while maintaining the bondability during soldering or wire bonding,
A configuration that improves corrosion resistance is disclosed. Further, Japanese Patent Application Laid-Open No. 4-115558 discloses a configuration in which the Ag or Au plating film is thinly formed on the Pd layer to prevent oxidation of the Pd layer and improve solder wettability. Further, Japanese Patent Laid-Open No. 7-169901 discloses that Ni
A construction is disclosed in which a protective composite layer is formed on the layer.
As the protective composite layer, a multilayer film such as a Pd layer, a Pd / Ni layer, an Au layer, etc. is shown.

[0003]

However, the structure in which the Pd layer is provided on the above-mentioned conventional Ni plating layer is P
When the thickness of the d layer is increased, there is a problem that film peeling easily occurs due to stress inside the layer. In such a state where the coating film is likely to be peeled off, the wire is peeled off from the lead frame when the wire bonding is performed.
Further, when the lead frame is bent during the assembly of the IC chip, the coating film peels off, and mounting such as soldering becomes impossible.

It is an object of the present invention to provide an article having a Nid layer and a Pd layer stacked on the Ni layer, while preventing film peeling.

[0005]

In order to achieve the above object, according to the present invention, the following articles are provided.

That is, an article having a base material and a coating film formed on at least a part of the base material, wherein the coating film is disposed on a Ni-containing layer and an upper side of the Ni-containing layer. In addition, it is composed of a plurality of layers having a layer containing Pd, and the Ni layer is provided between the layer containing Ni and the layer containing Pd.
In the article, a layer containing Ni and Au is arranged in a position in contact with the layer containing Pd, and a layer containing Pd and Au is arranged in a position in contact with the layer containing Pd.

The inventors have found that conventional Pd on Ni plating film
It was considered that the reason why the layers were easily peeled off was that Ni and Pd were less likely to diffuse into each other. For this reason, it is difficult to form a diffusion layer between the Ni layer and the Pd layer, and the bonding between the Ni and Pd metals is weakened. In the present invention, Au is arranged to easily form a diffusion layer for both Pd and Ni, and a diffusion layer of Pd and Au and a diffusion layer of Ni and Au are formed to increase the adhesion strength. Although such elements that form a diffusion layer with Pd and Ni are present other than Au, metals other than Au may move to the surface of the coating film and cause corrosion. Therefore, in the present invention, Au that does not cause corrosion is used.

[0008]

An embodiment of the present invention will be described with reference to the drawings.

First, a lead frame of one embodiment will be described with reference to FIG.

As shown in FIG. 1, in the present embodiment, the base material 1
A copper alloy is used as 1, and a Ni layer 1 that is melted with the solder during soldering and forms a good joint is arranged on the surface of the base material 11.

A Pd layer 18 is disposed on the Ni layer 14 to prevent the Ni layer 14 from being oxidized. Ni layer 14 and Pd
In order to improve the adhesiveness between the layer 18 and the layer 18,
Layers 15 to 17 are formed. That is, the Ni-Au diffusion layer 15 is formed on the upper side of the Ni layer 14 so as to be in contact with the Ni layer 14, and the Pd-Au diffusion layer 15 is formed on the lower side of the Pd layer 18 so as to be in contact with the Pd layer 18. 17 is formed. An Au layer 16 for forming these two layers is disposed between the Ni-Au diffusion layer 15 and the Pd-Au diffusion layer 17. The Pd layer 18 has excellent corrosion resistance and
Since the solder hardly melts and is excellent in bonding with a bonding wire, it is possible to prevent the Ni layer 14 from being oxidized and to provide good bondability during soldering or bonding.

On the surface of the Pd layer 18, Pd-Au is formed.
The diffusion layer 19 is arranged. The Pd-Au diffusion layer 19 is made of Pd.
An oxide film is formed on the surface of the layer 18 to prevent the solder wettability from decreasing.

The outer shape of the lead frame of this embodiment can be shaped as shown in FIG. That is, it has a shape including an island portion 81, an inner lead portion 82, an outer lead portion 83, and a tie bar portion 84. The outer lead portion 83 is a portion exposed to the outside of the mold when formed into an IC chip. The inner lead portion 82 is located inside the mold and is a portion to be bonded to the semiconductor element mounted on the island portion 81.

In the present embodiment, the outer lead portion 83
1 to form all of the coatings of layers 14 to 19 of FIG. Further, all of the coatings of the layers 14 to 19 are formed also in the region II of the inner lead portion 82 where bonding is performed. However, it is desirable to form only one layer 14 in the region III of the inner lead portion 82 where bonding is not performed. In addition, the island portion 81 (see FIG.
It is desirable to form only one of the layers 14 in the area IV). Thus, in regions III and IV of FIG.
The reason for exposing the Ni layer 14 is to improve the adhesion between the resin used for bonding the semiconductor element and the island portion 81 and the resin used for molding.

Now, the structure of the coating film of the lead frame of another embodiment of the present invention will be described. For example, as shown in FIG. 2A, a structure without the Au layer 16 in the structure shown in FIG. 1 or instead of the layers 15 to 17 as shown in FIG.
The Ni-Pd-Au diffusion layer 22 in which i, Pd, and Au are mutually diffused may be provided. Further, as shown in FIG. 2C, instead of the Au layer 16 of FIG.
A configuration including the Pd-Au diffusion layer 22 can also be adopted. Even in the case of the configurations of FIGS. 2A, 2B, and 2C, N
The adhesion between the i layer 14 and the Pd layer 18 can be improved.

Further, in FIG. 1, on the outermost surface of the Pd layer 19,
Although the Pd-Au diffusion layer 19 in which Au is diffused in Pd is arranged, it does not necessarily have to be a diffusion layer, and a structure in which an Au layer is simply arranged may be adopted.

A process of manufacturing the coating of FIG. 1 of the lead frame of this embodiment will be described. In this embodiment, each layer of the coating film is formed by electroplating.

First, as shown in FIG. 5A, a plurality of strip-shaped base materials 50 in which a plurality of lead frame base materials 11 are connected are set on a plurality of plating jigs 51. This is arrange | positioned between the two anodes 53 in the plating bath 52 like FIG.5 (b). The strip-shaped base material 50 is connected to the negative electrode of the power source through the plating jig 51, and electrolytic cleaning and plating are performed. At this time, the jet forming device 54 forms a jet in the plating bath 52. In addition, in a process requiring heating of the plating bath 52, heating is performed by a heater (not shown). As the plating bath 52, a plating bath having a composition of each step shown in Tables 1 and 2 is prepared, and these plating baths are sequentially subjected to the conditions shown in Tables 1 and 2 in order of 1, alkaline electrolysis. By performing a cleaning step, 2, a hydrochloric acid dipping step, 3, a nickel plating step 4, a gold strike step 5, a palladium plating step 6, and a gold strike step, the substrate 1 having the layer structure shown in FIG.
Can be formed on one. Steps 1 and 2 are for the base material 11
This is a surface cleaning process. Step 3 includes Ni layer 14 and Step 4
Is a step of forming the Au layer 16, and step 5 is a step of forming the Pd layer 18. Step 6 is a step of forming an Au layer for forming the Pd-Au diffusion layer 19 on the Pd layer 18.

After completion of these plating steps, hot air drying is carried out as a step of drying the film. At this time, in the present embodiment, by setting the hot air temperature to 110 ° C. to 150 ° C., heat treatment is applied to the plating film at the same time as drying, and the Au layer
6 of Au is diffused into the Ni layer 14 and the Pd layer 18,
The Ni-Au diffusion layer 15 and the Pd-Au diffusion layer 17 are formed. At the same time, the Au layer formed in step 6 is used as the Pd layer 18
To form a Pd-Au diffusion layer 19.

After drying with hot air, 100 ° C. to 3 ° C.
By applying a heat treatment at about 00 ° C. for a predetermined time, Au
Are diffused sufficiently to diffuse the diffused Ni-Au diffusion layer 15, Pd-
It is also possible to form the Au diffusion layer 17 and the Pd-Au diffusion layer 19. The heat treatment time can be about 3 minutes at 100 ° C. and about 1 minute at 300 ° C., for example. When the heat treatment temperature is 150 ° C. or higher, it is desirable to perform the heat treatment in a reducing atmosphere in order to prevent oxidation of the coating film and the substrate. When the heat treatment is performed, the hot air drying temperature can be lowered to a normal temperature. It is also possible to perform both the above-mentioned high temperature hot air drying and heat treatment. The temperature and time of hot-air drying and heat treatment are determined experimentally as the temperature and time at which the thickness of the diffusion layer is obtained to a desired thickness.
Use it.

[0021]

[Table 1]

[0022]

[Table 2]

However, in the above steps, as shown in FIG. 8, the layers 15 to 19 are the outer lead portions 83, and
Before the step 4, since the inner lead portion 82 is formed only in the region II to be bonded, the regions III and IV in FIG.
Forming a mask on.

When forming the lead frame coating of the embodiment of FIG. 2A, the plating time in step 4 is shortened to reduce the amount of Au to be plated, or the plating bath is used. It can be formed by diffusing all the plated Au by raising the temperature to promote the diffusion. It is also possible to form by a method of diffusing Au by applying heat treatment after forming the film.

Further, when a Ni-Pd-Au diffusion layer is formed between the Pd layer 18 and the Ni layer 14 as shown in FIGS. 2B and 2C, a heat treatment step after step 8 is performed. In addition, it can be formed by mutually diffusing Pd, Ni, and Au.

Actually, a lead frame sample provided with the coating of the form of FIG. 1 was prepared by the above-mentioned manufacturing process, and its film peeling resistance and solder wettability were examined. The result will be described with reference to FIGS.

In the sample, the base material 11 was formed of a copper material containing Fe and P in the proportions of 0.1% and 0.03%, respectively, and each layer of the coating film was formed by the above-mentioned plating process. Ni layer 1
The thickness of No. 4 was 2.0 μm, and the thickness of the Pd—Au diffusion layer 19 was 0.008 μm. The Au layer 16 has a thickness of 0.
The thickness of the Pd layer 18 is 0.05 μm, 0.15 μm, and 0.50 μm.
A plurality of samples having respective thicknesses of m and 1.0 μm were prepared.
At this time, the Pd-Au diffusion layer 17 and the Ni-Au diffusion layer 1
The thickness of 5 is 0.005 μm. In addition, as a comparative sample, only the gold plating in the step 4 in the manufacturing process described above was not performed, and the Pd-Au diffusion layer 17, the Au layer 16, the Ni-A were used.
A sample having no u diffusion layer 15 was prepared.

In order to examine the film peeling resistance of each sample, the following bending test was conducted.

First, the sample is sandwiched between two plate-shaped jigs.
At this time, a part of the sample is projected from between the jigs. Then, a force is applied to the portion of the sample protruding from the jig to bend the sample by 90 degrees with respect to the main plane. Return the bent part to its original position, bend it 90 degrees to the opposite side, and then return it to its original position. After this bending test,
It was examined whether film peeling occurred in the bent portion.

The results are shown in FIG. However, in FIG. 3, the Au layer 16 having a film thickness of 0 is a comparative sample.

As shown in FIG. 3, film peeling did not occur in the comparative sample only in the comparative sample in which the thickness of the Pd layer 18 was 0.05 μm, and when the thickness of the Pd layer 18 was 0.15 μm or more.
Film peeling occurred in all of the two comparative samples. On the other hand, in the sample of the present embodiment, no sample was peeled off regardless of the film thickness of the Pd layer 18. From this, as in the present embodiment, the Pd-Au diffusion layer 17, the Au layer 16, the Ni-A are provided between the Pd layer 18 and the Ni layer 14.
It is clearly understood that the film peeling can be prevented by providing the u diffusion layer 15. Further, in order to evaluate the solder wettability of the lead frame of the present embodiment, after heating the above-mentioned sample, it is immersed in solder. The test was done. As a result, all the samples had good solder wettability. As a result, as in this embodiment, Pd
It was confirmed that the three layers of Pd-Au diffusion layer 17, Au layer 16, and Ni-Au diffusion layer 15 arranged between the layer 18 and the Ni layer 14 did not affect the solder wettability.

As described above, it is understood that the lead frame having the structure of FIG. 1 according to the present embodiment has good adhesion, excellent corrosion resistance, and high solder wettability. For this reason, in the lead frame provided with the coating of the present embodiment, film peeling is less likely to occur during wire bonding, and a defect in which the wire is disengaged from the lead is less likely to occur. Further, even when the outer lead portion 83 of the lead frame formed into an IC chip is bent, the plating film is not easily peeled off, and the solder joining at the time of mounting can be favorably performed.

Here, the film thickness of each layer of the lead frame of the present embodiment is not limited to the film thickness of the above-mentioned sample, and can be freely designed. For example, the Ni layer 14 is 0.5 to 2.0 μm, and the Pd layer 18 is 0.05 to 2.0 μm.
1.0 .mu.m, Pd-Au diffusion layer 19 with 0.005 to 0.
It can have a thickness of 015 μm. In addition, in FIG. 1, FIG. 2A, and FIG. 2C, the Pd—Au diffusion layer 17 and the Ni—Au diffusion layer 15 may have these layers regardless of the thickness. In addition, in the configuration of FIG. 2B, Ni-Pd- in which Ni, Pd, and Au are mutually diffused.
The Au layer may be present regardless of its thickness.

Here, a process of manufacturing a semiconductor chip by attaching a semiconductor element to the lead frame of this embodiment shown in FIGS. 1 and 4 will be briefly described. First, a semiconductor element is fixed to the island portion 81 shown in FIG. 4 with an adhesive. The electrode pad of the semiconductor element and the inner lead portion of the lead frame are bonded and bonded with a bonding wire. The semiconductor element and the inner lead portion 82 are filled with resin to form a mold. Then, the tie bar portion 84 is cut off, and the outer lead portion 83 is bent and formed according to the application. This completes the semiconductor chip. When mounting a semiconductor chip on a printed circuit board or the like, the tip of the outer lead portion is inserted into a hole of the printed circuit board, immersed in a solder bath, and soldered.

In the manufacturing process of such a semiconductor chip, the lead frame of the present embodiment is provided with the coating as shown in FIG. 1 on the region II of the inner lead portion 82 and the outer lead portion 83. The film is less likely to peel off, and the bonding characteristics during soldering and bonding are good. Therefore, it is possible to provide a lead frame that has high workability during assembly and is unlikely to cause defective products.

In addition, in the plating process for forming the coating film of the lead frame in the present invention, in addition to the apparatus shown in FIG. 5B, a hoop material 63 in which the lead frame base material 11 is continuous is used. A plating device such as No. 6 can be used. When the hoop material 63 as shown in FIG. 6 is used, the hoop material 63 is sent out by the roller 61 and passed through the plating bath 62. Power is supplied to the hoop material 63 by the roller 61. At this time, the plating bath 62 can be divided into a processing bath 71 and a management bath 72 as shown in FIG. With the configuration shown in FIG. 7, the plating bath pumped up by the pump 73 from the management bath 72 can be supplied to the processing bath 71 as a jet stream, and the plating bath overflowing from the processing bath 71 can be circulated to the management bath 72. .

In the lead frame of the above embodiment,
Although the coating film on the base material is formed by plating, it is of course possible to form each layer by a method other than plating, for example, a vapor phase growth method such as sputtering or vapor deposition.

Further, in the above-described embodiment, Ni-Au is used.
The diffusion layer 15, the Pd-Au diffusion layer 17, the Pd-Au diffusion layer 19 and the like are subjected to Au treatment by heat treatment during or after plating.
However, instead of these diffusion layers, a Ni—Au alloy layer, a Pd—Au alloy layer, or a Pd—Au alloy layer can be formed from the beginning by plating or heat treatment. Even when these alloy layers are formed,
The adhesion of the coating can be improved as compared with the conventional one.

Further, in the above-mentioned embodiment, the Ni layer 14 is formed directly on the base material 11, but it is also possible to dispose the underlayer of the Ni layer 14 between them. For example, a Cu layer can be used as the base layer 14.

Although the lead frame has been described in the above embodiment, the present invention is not limited to the lead frame, and can be applied to other articles having a coating on an iron base material. .

[0041]

As described above, in the present invention, on the substrate,
An article having a Ni film and a Pd film and having high film adhesion can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a lead frame according to an embodiment of the present invention.

2A, 2B, and 2C are cross-sectional views showing the structure of a lead frame according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram for explaining a result of performing a film peeling test on the sample in the form of FIG. 1.

FIG. 4 is an explanatory view showing the shape of the lead frame of the present embodiment.

FIG. 5 is an explanatory diagram for explaining an overall configuration of (a) a plating jig and (b) a plating apparatus for manufacturing the lead frame according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a configuration of a plating apparatus for manufacturing the lead frame according to the embodiment of the present invention.

7 is an explanatory view for further explaining the plating apparatus of FIG.

[Explanation of symbols]

11 ... Base material, 14 ... Ni layer, 15 ... Ni-
Au diffusion layer, 16 ... Au layer, 17 ... Pd-Au
Diffusion layer, 18 ... Pd layer, 19 ... Pd-Au diffusion layer, 20 ... Zn layer, 22 ... Ni-Pd-Au diffusion layer, 51 ... Plating jig, 52 ... ..Plating baths
53 ... Anode.

Claims (10)

[Claims] 1. An article having a base material and a coating formed on at least a part of the base material, the coating being disposed on a Ni-containing layer and above the Ni-containing layer. And a layer containing Ni and Au is disposed between the layer containing Ni and the layer containing Pd at a position in contact with the layer containing Ni. An article characterized in that a layer containing Pd and Au is arranged at a position in contact with the layer containing Pd. 2. The method according to claim 1, wherein A is provided between the layer containing Ni and Au and the layer containing Pd and Au.
An article, in which a layer containing u is arranged. 3. The article according to claim 2, wherein the layer containing Ni and Au is a layer formed by diffusing Au into the layer containing Ni. 4. The article according to claim 2, wherein the layer containing Pd and Au is a layer formed by diffusing Au into the layer containing Pd. 5. An article having a substrate and a coating formed on at least a part of the substrate, the coating being disposed on a layer containing Ni and above the layer containing Ni. In addition, a plurality of layers including a Pd-containing layer are provided, and N is provided between the Ni-containing layer and the Pd-containing layer.
An article, wherein a layer containing i, Au, and Pd is arranged. 6. The article according to claim 1, wherein a layer containing Pd and Au is arranged on the layer containing Pd. 7. The article according to claim 6, wherein the layer containing Pd and Au is a layer formed by diffusing Au into the layer containing Pd. 8. A lead frame comprising a base material and a coating film formed on at least a part of the base material, wherein the coating film is disposed on a Ni-containing layer and above the Ni-containing layer. And a layer containing Ni and Au is arranged between the layer containing Ni and the layer containing Pd at a position in contact with the layer containing Ni. The lead frame, wherein a layer containing Pd and Au is arranged at a position in contact with the layer containing Pd. 9. A lead frame comprising a base material and a coating film formed on at least a part of the base material, wherein the coating film is disposed on a Ni-containing layer and above the Ni-containing layer. A plurality of layers including a Pd-containing layer, and N between the Ni-containing layer and the Pd-containing layer.
A lead frame, in which a layer containing i, Au, and Pd is arranged. 10. A method of manufacturing an article comprising a coating film composed of a plurality of layers on a base material, the method comprising: forming a Ni-containing layer on the base material by plating; Forming a layer containing Au by plating, diffusing Ni and Au into each other, and forming a layer containing Ni and Au between the layer containing Ni and the layer containing Au. A layer containing Pd is formed on the layer containing Au by plating to diffuse the Au and Pd into each other,
A step of forming a layer containing Au and Pd between the layer containing Pd and the layer containing Pd.