JPH11229178A - Metal coated member - Google Patents

Abstract

(57) [Problem] To provide a metal coating material in which oxidative discoloration is suppressed even when subjected to a heat treatment for a long period of time and solderability is not easily deteriorated. SOLUTION: An intermediate layer 2 made of at least one layer of Ag or an Ag alloy is formed on a partial surface or an entire surface of a conductive substrate 1.
Is formed and at least one surface layer 3 made of Sn or Sn alloy is formed on the surface of the intermediate layer 2 in the metal-coated member A1. It is formed of a Sn alloy containing In.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a metal coating material,
More specifically, the present invention relates to a metal coating material which is less likely to undergo oxidative discoloration even when heated for a long time or has excellent solderability, and is useful as a material for various electric / electronic parts and devices.

[0002]

2. Description of the Related Art A material having a substrate made of Cu, Fe or an alloy thereof and having a coating layer made of Sn or a Sn alloy typified by solder on the surface thereof has excellent conductivity and mechanical properties. Since it has both strength and excellent solderability and corrosion resistance provided by the coating layer, it can be used for contact materials such as connectors and terminals, component lead parts such as lead frames and lead wires, board circuits and wiring cable conductors, etc. Electronic
It is widely used as a material for electrical components.

[0003] These materials are deposited directly on the surface of a substrate.
It is usually manufactured by performing electroplating or hot-dip plating of n or Sn alloy, or cladding Sn or Sn alloy foil. At this time, Cu or Ni may be interposed as a base layer between the surface coating layer and the surface of the substrate. By the way, when these materials are used for electronic and electric parts, the temperature of the materials is generally 10 ° C due to external heating or self-heating during use.
It rises to about 0 ° C. In recent years, the self-heating has increased due to the high integration of components, and due to factors such as the proximity to other heat sources and the difficulty of good heat dissipation, the material has become In many cases, heating to a temperature of 120 ° C. or higher is performed.

However, when the operating temperature exceeds 120 ° C., the C existing under the Sn or Sn alloy coating layer is reduced.
u and the like are thermally diffused and reach the surface of the coating layer and are oxidized, so that the solderability is deteriorated. Also, Sn or Sn alloy constituting the uppermost layer, and further, the solder or the like laid thereon is In addition to causing poor appearance due to thermal diffusion and alloying as a whole, deterioration of material properties such as an increase in contact resistance is caused.

In the case of a material using Ni as a base layer, when the operating temperature exceeds 120 ° C., a Sn—Ni diffusion layer is formed between the coating layer and the Ni layer to cause an increase in contact resistance. . In order to solve such a problem, Sn or S
A material has been developed in which an intermediate layer made of Ag or an Ag alloy is interposed under a coating layer of an n alloy (Japanese Patent Laid-Open Publication No. 2-3).
01546, JP-A-2-301573).

[0006] However, even in the case of these materials, when the surface layer is made of Sn or ordinary solder, when exposed to the above-mentioned heating state for a long time at the above-mentioned temperature, oxidative discoloration also occurs. Problems such as a decrease in solderability may occur.

[0007]

According to the present invention, the surface layer is made of S
In order to solve the above-mentioned problem in the conventional material composed of n or Sn alloy, even if the material is heated for a long time at a temperature of 120 ° C. or more, the occurrence of oxidation discoloration is suppressed,
It is another object of the present invention to provide a metal coating material that does not easily cause a decrease in solderability.

[0008]

In order to achieve the above object, according to the present invention, at least one intermediate layer made of Ag or an Ag alloy is formed on a partial surface or the entire surface of a conductive substrate. At least one surface on the intermediate layer
In the metal-coated member on which a surface layer made of Sn or a Sn alloy is formed, at least the outermost layer of the surface layer is formed of a Sn alloy containing Bi or / and In. A metal coating is provided.

In particular, a metal coating material having an underlayer made of Ni, Co, or an alloy thereof interposed between the conductive substrate and the intermediate layer, or one of the intermediate layer and the surface layer. A metal coating material in which part or all is melted and re-solidified is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a metal coating material of the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a cross-sectional view showing a basic configuration of the metal coating material of the present invention. This material A1
Has a layer structure in which an intermediate layer 2 described below is formed by covering the surface of the conductive substrate 1, and a surface layer 3 described below is further formed by covering the intermediate layer 2.

The conductive substrate 1 may be made of any material having a heat-resistant temperature higher than the melting temperature of the solder and having at least a surface having conductivity. For example, Cu, Fe, Ni, Examples of such materials include Al and alloys thereof, conductive resins, and printed circuit boards. Also, the core is formed of steel or the like, and its surface is made of Cu,
A material coated with Ni, Cr, or the like may be used. Also,
The shape may be any shape such as a line or a stripe.

The intermediate layer 2 is made of Ag or an Ag alloy, and the metal constituting the surface of the substrate 1 and the metal constituting the underlayer, which will be described later, are thermally diffused into the surface layer 3 to cause oxidative discoloration and reduced solderability. Function as a barrier to prevent a situation from being caused. The intermediate layer 2 may be a single layer. However, when the intermediate layer 2 has a layer structure in which a plurality of layers obtained by appropriately combining a layer made of Ag alone and a layer made of an Ag alloy are stacked, the above-described barrier effect is improved. It is valid.

If the thickness of the intermediate layer 2 is too small, the above-mentioned barrier effect is reduced. Conversely, if the thickness is too large, expensive Ag is used.
Not only is the material wasted, but cracks occur, the substrate 1 is peeled off, and the workability of the entire material is reduced.
It is preferable to set the thickness to about 05 to 10 μm. This intermediate layer 2 is formed by electroplating, electroless plating, vacuum deposition, PV
It can be formed by a known film forming method such as a D method or a CVD method, may be formed by a cladding method, or may be formed on the entire surface of the substrate 1 or on a part of the surface.

As an Ag alloy constituting the intermediate layer 2, for example, Ag, Ag-Sn, Ag-In, Ag-C
u, Ag-Zn, Ag-Pd, Ag-Se, Ag-Sb
Among them, Ag, A
Since g-Sn and Ag-In are components originally contained even when diffused into Sn on the surface, g-Sn and Ag-In are suitable in that the change in characteristics is reduced.

Next, the surface layer 3 formed by covering the intermediate layer 2 is made of Sn or a Sn alloy. Since this layer functions as a working surface when soldering other components, for example, it is desired not only to have excellent solderability, but also to not undergo oxidative discoloration even during long-time heating. . This surface layer 3 may be a single layer,
Further, a layer structure in which a plurality of layers obtained by appropriately combining a layer made of Sn alone or a layer made of Sn alloy may be used. In this case, the outermost layer 3A of the surface layer 3 is formed of Sn-Bi.
It must be made of any one of an alloy, a Sn—In alloy, and a Sn—Bi—In alloy.

Each of these alloys is a material which is less likely to undergo oxidative discoloration during heating than Sn alone or ordinary solder, and has a lower melting temperature than Ag or the Ag alloy constituting the intermediate layer 2. Needless to say, even when the layer located immediately below the outermost layer portion 3A is made of Sn alone, since the melting point is lower than that of Sn alone, the solderability is good and the soldering time is long. This is because, even after the heating, the composition exhibits good solderability without causing oxidative discoloration.

When the outermost layer 3A is made of an Sn-Bi alloy, if the Bi content is too large, the strength characteristics of the joint are deteriorated with time after joining by soldering. Since blowholes are easily generated sometimes, the content is preferably regulated to 10% by weight or less after reflow. In the case of Sn-In alloy, I
Considering that n is expensive and, for example, in order to suppress the occurrence of blowholes at the time of welding with an Al wire, its content is preferably regulated to 8% by weight or less after reflow.

The thickness of the surface layer 3 is preferably set to 0.05 to 20 μm in relation to the formation of the surface layer by a reflow treatment described later. When the thickness of the surface layer 3 is smaller than 0.05 μm, the constituent metal of the surface layer 3 is thermally diffused toward the lower layer during the reflow treatment, and the surface layer 3 disappears. This is because the function and effect will not be exhibited. If the thickness is more than 20 μm, the molten metal of the surface layer 3 flows out during the reflow treatment, and the surface after the reflow treatment may not be smooth.

The surface layer 3 can be easily formed by various film forming methods as in the case of the intermediate layer 2. FIG. 2 is a sectional view showing another metal coating material A2 of the present invention. This material A2 has a layer structure in which a base layer 4 is interposed between the conductive substrate 1 and the intermediate layer 2. This underlayer 4
Functions as a barrier for preventing metal such as Cu diffused from the substrate 1 from reaching the intermediate layer 2 and further reaching the surface layer 3, and causes oxidative discoloration of the surface layer 3 more than the material A1. It is a material that is difficult or has improved solderability.

The underlayer 4 is preferably made of Ni, Co, or an alloy thereof, and has a thickness of 0.1 from the viewpoint of a barrier effect, manufacturing cost and workability.
The thickness is preferably about 1 to 2 μm. In the case of the metal coating material of the present invention, it may be a material as manufactured by applying the above-mentioned various film forming methods, but it is further subjected to a reflow treatment to once melt the surface layer portion 3 and then re-use it. It is preferably solidified.

The reason is that the surface layer formed after the re-solidification becomes smooth, so that the soldering operation can be easily performed.
This is because whiskers that can be generated when the concentrations of i and In are low are prevented, and when the surface layer is thin, the Ag of the intermediate layer diffused by the reflow treatment acts to further enhance the solderability. When performing such reflow treatment, as described above, the thickness of the surface layer 3 is 0.05 to 2 mm.
It is set to 0 μm.

[0022]

Examples 1 and 2 A conductive substrate 1 was manufactured by performing a pretreatment on the surface of a steel strip made of Al-killed steel and then performing Cu plating under the following conditions. Composition of plating bath: Copper sulfate pentahydrate 250g / L, sulfuric acid 60g
/ L.

Plating conditions: bath temperature 50 ° C., current density 9 A / dm
² , Plating time 30 seconds. The conductive substrate 1 in which the surface of the steel strip was covered with a Cu plating layer having a thickness of 1 μm was obtained. Next, Ag plating was performed on the surface of the conductive substrate 1 under the following conditions to form the intermediate layer 2.

Composition of plating bath: 6 g of potassium silver cyanide /
L, potassium cyanide 80 g / L. Plating conditions: bath temperature 25 ° C., current density 2 A / dm ² , plating time 30 seconds. The surface of the conductive substrate was covered with a 0.6 μm thick Ag plating layer (intermediate layer 2). Next, Sn-Bi alloy plating was performed on the surface of the Ag plating layer under the following conditions.

Composition of plating bath: PF-TIN 450 g /
L, PF-BI 50g / L, PF-ACID 150g / L, P
F-0.5M30mL / L. (All are plating baths manufactured by Ishihara Chemical Co., Ltd.) Plating conditions: bath temperature 40 ° C., current density 10 A / dm ² , plating time 25 seconds. An Sn—Bi alloy plating layer having a thickness of 2 μm was formed on the Ag plating layer, and the material A1 having the layer structure shown in FIG. 1 was obtained.

This material is referred to as Example 1. This material A1 was subjected to a reflow treatment at an atmosphere temperature of 650 ° C. for a treatment time of 3 seconds. The obtained material is referred to as Example 2. Examples 3 and 4 Ag plating layer (intermediate layer 2) in the same manner as in Example 1.
Until formed. Next, Sn plating was performed on this Ag plating layer under the following conditions.

Composition of plating bath: PF-TIN 450 g /
L, PF-ACID 150 g / L, PF-0.5M 30 mL / L. Plating conditions: bath temperature 40 ° C., current density 10 A / dm ² , plating time 20 seconds. A 1.6 μm thick Sn plating layer was formed by covering the Ag plating layer. Next, a 0.4 μm thick Sn—Bi alloy plating layer was formed on the Sn plating layer in the same manner as in Example 1 except that the plating time was 5 seconds.

In the obtained material, the outermost layer 3A of the material A1 shown in FIG.
It consists of a Bi alloy plating layer, and a 1.6 μm thick S
The material has a two-layer structure in which an n-plated layer exists. This material is referred to as Example 3. This material was subjected to a reflow treatment under the same conditions as in Example 2, and the obtained material was referred to as Example 4.

Examples 5 and 6 Example 3 was repeated except that the Sn—Bi alloy plating layer in Example 3 was a Sn—In alloy plating layer formed by electroless plating under the following conditions. Similarly,
A material having a two-layer surface layer was manufactured. Composition of plating bath: 80 g / L tin methanesulfonate,
Indium chloride 10 g / L, methanesulfonic acid 40 g / L, thiourea 120 g / L, sodium hypophosphite 65 g / L, nonionic surfactant 10 g / L, amphoteric surfactant 2 g / L.

Plating conditions: bath temperature 55 ° C., immersion for 180 seconds. A 0.4 μm thick Sn—In alloy electroless plating layer was formed on the Sn plating layer. This material is referred to as Example 5. This material was subjected to the same reflow treatment as in Example 1, and the obtained material was used as Example 6.

Examples 7 and 8 In Example 1, a material having the same layer structure as in Example 1 was produced except that the surface of the steel strip was plated with Ni under the following conditions. This material corresponds to the material A2 having the underlayer 4 shown in FIG. Plating bath composition: nickel sulfamate 400g / L,
Boric acid 40 g / L.

Plating conditions: bath temperature 50 ° C., current density 10 A /
dm ² , plating time 30 seconds. The thickness of the Ni plating layer formed on the surface of the steel strip is 1 μm
Met. This material is referred to as Example 7. This material was subjected to a reflow treatment in the same manner as in Example 1. The obtained material is referred to as Example 8. Comparative Examples 1 and 2 A material having the same layer structure as that of Example 1 was manufactured except that the Sn—Bi alloy plating layer of Example 1 was a solder plating layer formed under the following conditions.

Composition of plating bath: IS-TIN 570 g /
L, IS-LEAD15g / L, IS-ACID54g / L,
519M 50 mL / L (all are plating baths manufactured by Ishihara Chemical Co., Ltd.). Plating conditions: bath temperature 40 ° C., current density 10 A / dm ² , plating time 25 seconds. A material in which a solder plating layer having a thickness of 2 μm was formed on the Ag plating layer was obtained.

This is referred to as Comparative Example 1. This material was subjected to a reflow treatment under the same conditions as in Example 1. The obtained material is referred to as Comparative Example 2. Comparative Examples 3 and 4 Example 1 was the same as Example 1 except that the Sn—Bi alloy plating layer of Example 1 was a plating layer of Sn alone (thickness 1.6 μm).
A material having the same layer structure as described above was manufactured. Note that the formation of the Sn plating layer was performed under the same conditions as in Example 3.

This material is referred to as Comparative Example 3. This material was subjected to a reflow treatment under the same conditions as in Example 1. The obtained material is referred to as Comparative Example 4. As described above, the heat discoloration test and the solderability were evaluated for the 12 types of materials according to the following specifications. Heat discoloration test: Each material was heated in the air at a temperature of 120 ° C., and the relationship between the heating time and discoloration was visually observed. In the case of no discoloration: ，, in the case of slightly yellow discoloration: △, in the case of strong yellowing or blackening: ×.

Solderability: molten solder at a temperature of 240 ° C. (Sn-Ag-Bi-Cu-based P manufactured by Senju Metal Industry Co., Ltd.)
b free solder, using trade name Eco Solder 121) in each of the materials subjected to the heat treatment for the time shown in Table 1.
After immersion for 2 seconds, take out and visually observe the appearance. At this time, rosin flux was used.

When the wetness was uniform and good, the evaluation was ○, when the wetness was slightly uneven: Δ, and when there was repelling: X.
Table 1 shows the above results.

[0038]

[Table 1]

The following is clear from Table 1. (1) The material of the present invention is hardly discolored or has excellent solderability even when heated for a long time, as compared with the material of the comparative example. This proves the effectiveness of the material according to the present invention that the outermost layer is made of a Sn—Bi alloy or a Sn—In alloy.

(2) Also, as is apparent from comparison between Examples 1 and 2, Example 3 and Example 4, and Examples 7 and 8, a reflow process is performed after forming a plating layer. It can be seen that the application improves the solderability. Thus, the reflow process is effective. (3) Further, as is apparent from comparison between Examples 7 and 8 and the other examples, when a Ni plating layer is interposed between the conductive substrate and the intermediate layer, the occurrence of discoloration can be effectively suppressed. it can.

[0041]

As is apparent from the above description, the metal coating material of the present invention hardly causes oxidative discoloration even if it is heated at a temperature of about 120 ° C. for a long time, or hardly causes a decrease in solderability. This is because the surface layer is made of Sn or a Sn alloy, and the outermost layer is made of a low melting point Sn—Bi alloy, S
This is an effect obtained by forming with an n-In alloy or a Sn-Bi-In alloy.

Further, since this surface layer has a good bondability with a solder containing no Pb, it is possible to use a Pb-free solder and contribute to the preservation of the global environment.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sectional structure of a material A1 of the present invention.

FIG. 2 is a sectional view showing a sectional structure of another material A2 of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 intermediate layer (Ag or Ag alloy layer) 3 surface layer (Sn or Sn alloy layer) 3A outermost layer portion of surface layer 3

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C25D 5/50 C25D 5/50 H01L 23/50 H01L 23/50 DV

Claims (3)

[Claims] At least one intermediate layer made of Ag or Ag alloy is formed on a partial surface or the whole surface of a conductive substrate, and at least one surface layer made of Sn or Sn alloy is formed on the surface of the intermediate layer. Is formed, at least the outermost layer portion of the surface layer is Bi
And / or a metal coating material formed of a Sn alloy containing In. 2. Between the conductive substrate and the intermediate layer,
2. The metal coating material according to claim 1, wherein an underlayer made of Ni, Co, or an alloy thereof is interposed. 3. The metal coating material according to claim 1, wherein a part or all of said intermediate layer and said surface layer are melted and re-solidified.