JPH11302874A - Stripping liquid for stripping tin or tin alloy on copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stripping liquid capable of surely stripping not only a tin layer or a tin alloy layer on a copper alloy but a copper-tin alloy layer on the under part thereof by preparing the stripping liquid containing at least ferric nitrate, an alkanesulfonic acid and chlorine respectively in a specific concentration. SOLUTION: The stripping liquid containing at least 30-300 g/l, preferably 30-120 g/l ferric nitrate (ferric nitrate.9-hydrate or the like), 120-200 g/l, preferably <140-235 g/l alkanesulfonic acid (methane; sulfonic acid, ethane, sulfonic acid or the like, >=20 mg/l, preferably 20-60 mg/l chlorine (hydrochloric acid, sodium chloride) is prepared. And if necessary, 1.0-200 g/l acetic acid and 0.05-2 wt.% additives such as a surfactant can be contained and the use temp. of the stripping liquid is controlled to 15-40 deg.C. As a result, the solubility of the copper alloy is held remarkably low and the surface of the copper alloy after stripping is made flat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stripping solution for stripping tin or tin alloy on a copper alloy, and more particularly to a tin layer or tin alloy layer provided on a copper alloy by plating, and a copper layer existing thereunder. A stripper for stripping the tin alloy layer;

[0002]

2. Description of the Related Art For example, a lead frame formed of a copper alloy has been used for mounting electronic components such as transistors and ICs. A pattern made of a tin layer or a tin alloy layer such as a tin-lead alloy (solder) is formed on the lead frame for various purposes by electroplating or the like. In a process or the like, the tin layer or the tin alloy layer on the lead frame is removed. Also, when recovering the copper alloy from the discarded lead frame, it is necessary to remove the tin layer or the tin alloy layer.

When the tin layer or the tin alloy layer on the lead frame is peeled off, not only the tin layer or the tin alloy layer but also the copper-tin alloy layer existing thereunder can be surely peeled off. It is required that the material (copper alloy) is less dissolved (usually 1 μm / min or less) and that the surface of the material (copper alloy) after peeling is flat.

As a stripping solution used for removing a tin layer or a tin alloy layer, for example, a stripping solution containing an aqueous solution of alkanesulfonic acid and ferric nitrate as disclosed in Japanese Patent Publication No. 4-80117 is known. Have been.

[0005]

However, the stripper disclosed in Japanese Patent Publication No. 4-80117 is for stripping a tin layer or a tin alloy layer formed on a copper surface, and is used for stripping a lead frame or the like. It is difficult to peel off a tin layer or a tin alloy layer formed on a copper alloy as described above. That is, when the stripping solution disclosed in Japanese Patent Publication No. 4-80117 is stripped under a composition condition that suppresses the dissolution of the material (copper alloy) at the time of stripping, a copper-tin alloy layer remains. On the other hand, composition conditions under which the copper-tin alloy layer can be peeled off (increase the concentration of alkanesulfonic acid)
When peeling is performed, smut is generated on the material (copper alloy) and the material (copper alloy) is extremely dissolved at the time of peeling, and the surface of the material (copper alloy) after peeling is rough,
Even if tin or a tin alloy is plated again after peeling, abnormal deposition such as poor adhesion to the material (copper alloy) or formation of a bump-like plating layer occurs.

[0006] Therefore, there is a demand for the development of a stripping solution capable of stripping tin or a tin alloy from a copper alloy while satisfying all of the above-mentioned conditions (1) to (4).

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and is intended to dissolve a tin layer or a tin alloy layer provided on a copper alloy or a copper-tin alloy layer existing thereunder by melting the copper alloy. It is an object of the present invention to provide a stripper for stripping so as to keep the copper alloy surface extremely low and to strip the copper alloy surface after stripping so as to be flat.

[0008]

In order to achieve such an object, the present invention provides at least ferric nitrate of 30 to 3 times.
Alkanesulfonic acid in an amount of from 120 to 3
The constitution was such that chlorine was contained within a range of 75 g / l and a solubility of 20 mg / l or more within the solubility range.

In the present invention, acetic acid is further added to 10-20.
The composition was such that it was contained in the range of 0 g / l.

[0010]

Next, an embodiment of the present invention will be described.

The stripping solution for stripping tin or tin alloy on a copper alloy according to the present invention is an aqueous solution containing at least ferric nitrate, alkanesulfonic acid and chlorine. In the range of 30 to 300 g / l, the content of alkanesulfonic acid in the range of 120 to 375 g / l,
The content of chlorine is set to 20 mg / l or more and within the solubility range.

Here, a tin layer or a tin alloy layer (for example, tin-lead alloy (solder)) is formed on the copper alloy by electroplating or the like.
When the layer is formed, tin and copper react with time to form a copper-tin alloy layer at the interface. The stripping solution of the present invention surely strips not only a tin layer or a tin alloy layer but also a copper-tin alloy layer existing thereunder.

The stripping solution of the present invention contains ferric nitrate in an amount of 30 to 300 g / l, preferably 30 to 120 g / l, as described above.
It is contained within the range of 1. 30g / l content
If it is less than 300 g / l, the copper-tin alloy layer will not dissolve and hinder peeling. ,
When a lead frame is used as a copper alloy, an allowable melting range (usually 1 μm / min or less) cannot be maintained. In the present invention, ferric nitrate nonahydrate can be used as ferric nitrate, and when ferric nitrate nonahydrate is used, the content is in the range of 50 to 500 g / l. Become.

As described above, the stripping solution of the present invention contains alkanesulfonic acid in an amount of 120 to 375 g / l, preferably 140 g / l.
235 g / l. When the content is less than 120 g / l, the copper-tin alloy layer does not dissolve and peeling becomes difficult. When the content exceeds 375 g / l, the copper alloy dissolves at the time of peeling (coupling of copper from the copper alloy). Become
For example, when a lead frame is used as a copper alloy, an allowable melting range (usually 1 μm / min or less) cannot be maintained. In the present invention, methanesulfonic acid, ethanesulfonic acid, or the like can be used as the alkanesulfonic acid. When 70% methanesulfonic acid is used, the content is in the range of 130 to 400 ml / l.

[0015] The stripping solution of the present invention contains chlorine as described above.
0 mg / l or more within the solubility range, preferably 20 mg / l
1 to 60 g / l, more preferably 20 mg / l to 6 g / l
It is contained within the range of 1. Chlorine concentration is 20mg
If it is less than / l, the copper-tin alloy layer does not dissolve and peeling is impossible. Hydrochloric acid, sodium chloride,
Potassium chloride, ferric chloride hexahydrate and the like can be used. The chlorine concentration in the stripping solution of the present invention can be appropriately set within the above range according to the target copper alloy.

The stripping solution of the present invention contains, in addition to the above-mentioned ferric nitrate, alkanesulfonic acid and chlorine as components,
One or more of acetic acid, propionic acid, lactic acid, etc.
You may contain in the range of 0-200 g / l. By appropriately adjusting the content of these components, it is possible to control the peeling rate of the tin layer or the tin alloy layer and the copper-tin alloy layer existing thereunder.

Further, the stripping solution of the present invention may contain an additive such as a surfactant in a range of 0.05 to 2% by weight, if necessary.

When the tin layer or the tin alloy layer on the copper alloy and the copper-tin alloy layer existing thereunder are stripped using the stripping solution of the present invention as described above, a stripping solution (treatment bath) Is not particularly limited, for example, 15 to 40.
It can be set in the range of ° C.

[0019]

Next, the present invention will be described in more detail with reference to examples. (Example 1) First, MF-202 manufactured by Mitsubishi Metex Co., Ltd. (Cu = 97.75%, Sn =
2.0%, Ni = 0.2%, P = 0.05%), a tin-lead alloy layer (solder layer) having a thickness of 10 μm was formed on this copper alloy to prepare a sample to be peeled. . In this sample, it was confirmed that a copper-tin alloy layer was present under the solder layer.

On the other hand, ferric nitrate 9-hydrate was used as ferric nitrate, 70% methanesulfonic acid was used as alkanesulfonic acid, and hydrochloric acid was used as a chlorine source. 24 types of aqueous solutions containing the solutions having the concentrations shown in 1 were prepared to obtain stripping solutions (samples 1 to 24). The chlorine concentration of these stripping solutions was 60 mg / l.

Using the above stripper (samples 1 to 24),
Create a treatment bath with a bath temperature of 25 ± 2 ° C and a liquid volume of 200 ml.
The above-mentioned sample to be peeled was immersed in a bath to form a solder layer and a copper layer.
The tin alloy layer was peeled off. The time required for this stripping treatment and the dissolution rate of the copper alloy at the time of stripping were measured and are shown in Table 1 below.

[0022]

[Table 1] As shown in Table 1, ferric nitrate contained 30 to 300 g /
1 (50-500 as ferric nitrate 9-hydrate)
g / l), and methanesulfonic acid is 120 to 375
g / l (130% as 70% methanesulfonic acid).
All of the stripping solutions of the present invention (samples 2 to 6, 9 to 17, and 19 to 24) in the range of 400 to 400 ml / l are capable of stripping the solder layer and the copper-tin alloy layer, and ,
It was confirmed that the dissolution rate of the copper alloy was 1 μm / min or less. The surface condition of the copper alloy subjected to the stripping treatment using the stripping solution of the present invention was good, and a tin-lead alloy layer (solder layer) having a thickness of 10 μm was formed again on this surface, resulting in abnormal deposition. No bumps or the like were generated by the heat treatment, and after that, even when the heat treatment was performed at 170 ° C. for 15 hours, no blistering or floating occurred in the solder layer.

On the other hand, in the stripping solutions (samples 1 and 8) in which the content of ferric nitrate or the content of methanesulfonic acid is less than the range of the present invention, the copper-tin alloy layer hardly dissolves. , Peeling was impossible. On the other hand, in the stripping solutions (samples 7 and 18) in which the content of ferric nitrate or the content of methanesulfonic acid exceeds the range of the present invention, although the solder layer and the copper-tin alloy layer can be stripped, The dissolution rate of the alloy exceeded 1 μm / min, which was not practical for peeling a tin-lead alloy on a lead frame. (Example 2) 200 g / l of ferric nitrate nonahydrate was contained as ferric nitrate, and 70% as alkanesulfonic acid
By containing methanesulfonic acid at 150 ml / l and using sodium chloride as a chlorine source and setting the chlorine concentration to the value shown in Table 2 below, 15 kinds of aqueous solutions were prepared and stripping solutions (samples 1 to 15) I got

For comparison, ferric nitrate 9-hydrate was contained at 230 g / l as ferric nitrate and 70% methanesulfonic acid was used at 500 ml / l as alkanesulfonic acid.
A stripping solution (sample 16) containing chlorine and not containing chlorine was prepared.

Using the above stripping solution (samples 1 to 16),
Create a treatment bath with a bath temperature of 25 ± 2 ° C and a liquid volume of 200 ml.
The same sample to be peeled as in Example 1 was immersed in a bath to peel the solder layer and the copper-tin alloy layer. The time required for the stripping treatment and the dissolution rate of the copper alloy at the time of stripping were measured and are shown in Table 2 below. Further, a plating appearance when a tin-lead alloy layer (solder layer) having a thickness of 10 μm was formed again on the surface of each copper alloy after the release treatment, and at 170 ° C.
The plating appearance after the heat treatment for 15 hours was observed and evaluated according to the following criteria. The results are shown in Table 2 below.

(Evaluation Criteria for Re-Solder Plating Appearance) ：: Flat and good, without occurrence of bumps due to surface roughness or abnormal precipitation Δ: Slight occurrence of bumps due to surface roughness or abnormal precipitation x: Surface roughness And bumps due to abnormal precipitation are observed. (Evaluation criteria for plating appearance after heat treatment) ○: Good without blistering or floating of solder layer △: Slight blistering or floating of solder layer ×: Solder layer Blistering or floating

[0027]

[Table 2] As shown in Table 2, the stripping solutions of the present invention (samples 4 to 15) having a chlorine concentration of 20 mg / l or more are capable of stripping the solder layer and the copper-tin alloy layer, and It was confirmed that the dissolution rate of the copper alloy was 1 μm / min or less. The surface condition of the copper alloy subjected to the release treatment using the release liquid of the present invention is good, and the appearance of the tin-lead alloy layer (solder layer) having a thickness of 10 μm formed again on this surface is good. In addition, the appearance of the solder layer after the heat treatment was good without blistering or lifting.

On the other hand, when the chlorine concentration is 0 mg / l,
With the stripper (samples 1 and 2) of mg / l, the solder layer can be stripped, but the copper-tin alloy layer did not dissolve, and a 10 μm thick tin-lead alloy layer ( In the solder layer), bumps due to surface roughness and abnormal precipitation were observed, and further, blisters and floating were observed in the solder layer after the heat treatment.

In the case of a stripping solution having a chlorine concentration of 10 mg / l (sample 3), the solder layer and the copper-tin alloy layer can be stripped, but the thickness of the stripping layer formed on this surface is reduced to 10 mg / l.
Abnormal precipitation was slightly observed in the tin-lead alloy layer (solder layer) of μm, and blistering and lifting were observed in the solder layer after the heat treatment.

Further, in the stripping solution having a high 70% methanesulfonic acid concentration and containing no chlorine (sample 16), although the solder layer and the copper-tin alloy layer can be stripped, the dissolution rate of the copper alloy is 1 μm / Min, and a smut is formed on the copper alloy, and a thickness of 10 μm is formed again on this surface.
In the tin-lead alloy layer (solder layer), bumps due to surface roughness and abnormal precipitation were observed, and further, blistering and lifting were observed in the solder layer after the heat treatment. (Example 3) 200 g / l of ferric nitrate nonahydrate was contained as ferric nitrate, and 70% as alkanesulfonic acid
90% acetic acid was added to a stripping solution consisting of an aqueous solution containing methanesulfonic acid at 150 ml / l and a chlorine concentration of 60 mg / l using sodium chloride as a chlorine source.
The peeling liquids (Samples 1 to 8) containing the following concentrations were prepared.

Using the above stripping solutions (samples 1 to 8), a treatment bath having a bath temperature of 25 ± 2 ° C. and a liquid volume of 200 ml was prepared, and the same sample to be stripped as in Example 1 was immersed in the bath. The solder layer and the copper-tin alloy layer were peeled off. The time required for this stripping treatment and the dissolution rate of the copper alloy at the time of stripping were measured and are shown in Table 3 below.

[0032]

[Table 3] As shown in Table 3, by increasing the acetic acid concentration, it was possible to shorten the solder peeling time (increase the peeling rate), and the dissolution rate of the copper alloy at this peeling was almost constant. (Example 4) First, the following five copper alloys were prepared as copper alloys.

EFTEC-3 Cu manufactured by Furukawa Electric Co., Ltd. Cu = 99.84% Sn = 0.15% P = 0.01% EFTEC-64T Cu manufactured by Furukawa Electric Co., Ltd .: 99.35% Sn = 0.25% Cr = 0.3% Zn = 0.1% ・ MF-202 manufactured by Mitsubishi Metex Co., Ltd. Cu = 97.75% Sn = 2.0% Ni = 0.2% P = 0.05 % OLIN-7025 Cu = 96.2% Ni = 3.0% Si = 0.65% Mn = 0.15% manufactured by Yamaha Ohlin Co., Ltd. C Cu = 99.85% manufactured by Mitsui High-Tech Co., Ltd. Sn = 0.15% A tin-lead alloy layer (solder layer) having a thickness of 10 μm was formed on each of the above-mentioned copper alloys to obtain a sample to be peeled. In each of these samples to be peeled, it was confirmed that a copper-tin alloy layer was present under the solder layer.

On the other hand, ferric nitrate 9-hydrate was used as ferric nitrate, 70% methanesulfonic acid was used as alkanesulfonic acid, hydrochloric acid was used as a chlorine source, and the following seven aqueous solutions were used. Was prepared to obtain stripping solutions (Samples 1 to 7).

Component concentration of stripping solution (sample 1) Ferric nitrate 9-hydrate 250 g / l 70% methanesulfonic acid 200 ml / l Chlorine concentration 120 mg / l of stripping solution (sample 2) Ingredient concentration / ferric nitrate 9-hydrate 100 g / l 70% methanesulfonic acid 300 ml / l Chlorine concentration 30 mg / l Component concentration of stripper (sample 3) Ferric nitrate 9 water 300 g / l 70% methanesulfonic acid 250 ml / l Chloride concentration 60 mg / l Concentration of stripping solution (sample 4) Ferric nitrate 9-hydrate 50 g / l 70% methane Sulfonic acid: 400 ml / l-Chlorine concentration: 120 mg / l Component concentration of stripper (sample 5) -Ferric nitrate 9-hydrate ... 200 g / l-70% methanesulfonic acid-150 ml / l-Chlorine concentration ... 60mg 90% acetic acid ... 60 ml / l Concentration of stripping solution (sample 6) Ferric nitrate 9-hydrate 200 g / l 70% methanesulfonic acid 150 ml / l Chlorine concentration 1200 mg / l -90% acetic acid: component concentration of 60 ml / l stripping solution (sample 7) -ferric nitrate 9-hydrate ... 230 g / l-70% methanesulfonic acid-500 ml / l stripping solution (samples 1 to 7) ), Bath temperature 25 ± 2
A processing bath having a liquid volume of 200 ml was prepared in the bath.
The solder layer and the copper-tin alloy layer were peeled by dipping the samples to be peeled. A plating appearance when a tin-lead alloy layer (solder layer) having a thickness of 10 μm is formed again on the surface of each copper alloy after performing the peeling treatment, and at 170 ° C.
The appearance of the plating after heat treatment for 15 hours was observed and evaluated according to the following criteria. The results are shown in Table 4 below.

(Evaluation Criteria for Re-Solder Plating Appearance) ：: Flat and good without occurrence of bumps due to surface roughness or abnormal precipitation △: Slight bumps due to surface roughness or abnormal precipitation are observed x: Surface roughness And bumps due to abnormal precipitation are observed. (Evaluation criteria for plating appearance after heat treatment) ○: Good without blistering or floating of solder layer △: Slight blistering or floating of solder layer ×: Solder layer Blistering or floating

[0037]

[Table 4] As shown in Table 4, the six types of stripping solutions of the present invention (Sample 1
All of the above 6) can exfoliate the solder layer and the copper-tin alloy layer on the copper alloy satisfactorily with respect to the four copper alloys except for OLIN-7025. The surface condition of each of the copper alloys was good, and a tin-lead alloy layer (solder layer) having a thickness of 10 μm was formed again on this surface.
Was good in appearance, and the appearance of the solder layer after the heat treatment was good without swelling or lifting.

Further, the solder layer and the copper-tin alloy layer formed on OLIN-7025 can be satisfactorily stripped with the stripping solution of the present invention (sample 6) in which the chlorine concentration is set high, and the stripping treatment was performed. The surface condition of each copper alloy is good, the appearance of the tin-lead alloy layer (solder layer) having a thickness of 10 μm formed again on this surface is good, and the appearance of the solder layer after heat treatment is blistering and floating. It was good without. From this, it was confirmed that the stripping solution of the present invention can appropriately set the chlorine concentration within a range of 20 mg / l or more according to the composition of the target copper alloy.

In contrast, a conventional chlorine-free stripping solution (sample 7) for stripping a tin layer or a tin alloy layer formed on a copper surface is composed of a solder layer on five types of copper alloys and a copper layer. -Although it is possible to peel off the tin alloy layer, smut is generated on the copper alloy, and the tin-lead alloy layer (solder layer) having a thickness of 10 μm formed again on this surface due to surface roughness or abnormal precipitation Ridges were observed, and after the heat treatment, blisters and floating were observed in the solder layer.

[0040]

As described above in detail, according to the present invention, the stripping solution comprises an aqueous solution containing at least ferric nitrate, alkanesulfonic acid and chlorine, and contains ferric nitrate. 30-300 g / l, alkanesulfonic acid content of 120-375 g / l, chlorine content of 2
By setting the solubility within the range of 0 mg / l or more, the tin layer or the tin alloy layer provided on the copper alloy and the copper-tin alloy layer existing thereunder can be surely peeled off, and this peeling can be performed. In this case, the dissolution of the copper alloy can be suppressed extremely low (for example, 1 μm / min or less), and the copper alloy surface after peeling becomes flat, and even if tin or a tin alloy is plated again, The adhesiveness is good, and the effect of maintaining a good adhesiveness even after heat treatment is achieved.

Further, by appropriately adding acetic acid in the range of 10 to 200 g / l, the peeling speed can be controlled.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mutsuko Miyakawa 2-3-1, Yoshino-cho, Omiya-shi, Saitama

Claims (2)

[Claims] (1) at least 30 to 300 g of ferric nitrate
/ Alkanesulfonic acid in the range of 120 to 375 g
A stripping solution for stripping tin or a tin alloy on a copper alloy, wherein the stripping solution contains chlorine in a range of 20 mg / l or more and a solubility range of 20 mg / l or more. 2. The stripping solution for stripping tin or tin alloy on a copper alloy according to claim 1, further comprising acetic acid in a range of 10 to 200 g / l.