JP2898297B2 - Stripper for tin and tin-lead alloy layers - Google Patents

Description

The present invention relates to a tin or tin-lead alloy stripper in the manufacture of printed wiring boards, and more particularly to a tin or tin-lead alloy by dipping, melting or spray melting. Tin and tin capable of selectively separating a layer from a copper substrate in a short time and preventing discoloration of the substrate-
The present invention relates to a stripping solution for a lead alloy layer.

[Prior art and its problems] Conventionally, in the production of a printed wiring board, a tin or tin-lead alloy layer plated on a copper-clad laminate uses a solution containing borofluoric acid and hydrogen peroxide or It is separated from the copper substrate using a mixed aqueous solution of hydrogen peroxide and an acid. However, in these solutions, the dissolution of copper increases at an accelerated rate, the metallic luster disappears, and the electrical properties of the substrate are greatly affected. In order to prevent these inconveniences, there have been proposed those in which a polyhydric alcohol is added to a stripping solution (Japanese Patent Application Laid-Open No. 60-149790) and those in which a copper inhibitor is added (Japanese Patent Application Laid-Open No. 57-166494). There is also a mixture of hydrofluoric acid and phosphoric acid (JP-A-63-76888). These stripping solutions basically use a fluorine-based acid solution, and are therefore highly corrosive and toxic, which not only imposes a heavy burden on equipment and work, but also makes it extremely difficult to treat wastewater. These problems can be solved by using advanced processing techniques, but the processing requires a large amount of expense and economic loss is reduced, and JP-A-58-77577 discloses alkyl sulfonic acid and aromatic nitro acid. Although a stripper containing a substitution compound and thiourea is disclosed, elution of copper from the copper base into the stripper is observed, resulting in discoloration of the copper base. Further, when the treatment is performed for a long time, there is the greatest defect that the dissolved tin or lead is substituted and precipitated on the copper base.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems, does not use fluoride or hydrogen peroxide, hardly elutes a copper base material, and furthermore, has dissolved tin or lead. It is an object of the present invention to provide a solution capable of exfoliating a tin or tin-lead alloy layer for a short period of time without causing substitutional precipitation.

[Means for Solving the Problems] According to the present invention, an aliphatic or aromatic organic sulfonic acid,
A solution for selectively stripping a tin and tin-lead alloy layer, which is an aqueous solution containing an aromatic nitro-substituted compound, thiourea or a derivative thereof, benzotriazole or a derivative thereof, and catechol is provided.

 Hereinafter, the present invention will be described in detail.

The organic sulfonic acid used in the stripping solution according to the present invention includes:
Preferably, it is selected from the group consisting of the following general formulas (a) and (b).

(A) General formula (R ₁ ) _n R—SO ₃ H wherein R represents a C _1-5 alkylene group, and R ₁ represents a hydroxyl group, an aryl group, an alkylaryl group, a carboxyl group or a sulfonic acid group. And n may be any position of the alkylene group, and n represents an integer of 0 to 3].

(B) General formula [Wherein R ₂ represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, a carboxyl group or a sulfonic acid group, and m represents an integer of 0 to 3].

Of the organic sulfonic acids (a) and (b) used in the stripping solution of the present invention, particularly important ones are 2-hydroxyethanesulfonic acid, 2-hydroxypropanesulfonic acid, 2-carboxyethanesulfonic acid, and methane. Sulfonic acid, ethanesulfonic acid, sulfosuccinic acid, benzenesulfonic acid, p-phenolsulfonic acid, and m-xylenesulfonic acid. The concentration may be from 1 g / l to saturation, but is preferably between 20 g / l and 200 g / l.

Organic sulfonic acids have the effect of solubilizing tin and tin-lead alloys.

The aromatic nitro compound used in the present invention preferably has the following formula: Wherein R ₃ and R ₄ represent hydrogen, a lower alkyl group, a hydroxyl group, a nitro group, a carboxyl group or an alkali salt thereof, or a sulfonic acid group or an alkali salt thereof; Must be something. Particularly preferably, R ₃ and / or R ₄ have a carboxyl group or a sulfonic acid group or a soluble group such as an alkali salt thereof. For example, m-nitrobenzenesulfonic acid, sodium, potassium or ammonium m-nitrobenzenesulfonate, 2,4-dinitrobenzenesulfonic acid, sodium, potassium or ammonium 2,4-dinitrobenzenesulfonate, sodium or potassium m-nitrobenzoate Or ammonium. Aromatic nitro compounds act as oxidants.

The concentration of the aromatic nitro compound may be from 0.5 g / l to saturation, but is preferably between 20 g / l and 100 g / l.

Further, thiourea or a derivative thereof is preferably represented by the following formula: Wherein R ′ and R ″ are hydrogen, lower alkyl group, lower alkenyl group, lower acyl group or phenyl group and may be the same or different. For example, thiourea, methylthiourea , Ethyl thiourea, dimethyl thiourea, diethyl thiourea, phenyl urea, methyl phenyl urea, allyl thiourea, acetyl thiourea and the like.

Thiourea or a derivative thereof is used as a peeling accelerator to some extent, but basically prevents the copper base from being dissolved. However, when the treatment is repeated as described above, tin and lead ions accumulate in the liquid, and these are reprecipitated on the copper base. The main object of the present invention is to improve this point. Therefore, the addition concentration of thiourea or a derivative thereof is 0.5 g / l to 10 g / l, preferably 1 to 5 g / l.

The benzotriazole derivative used in the present invention preferably has the following formula: [Where X is represented by hydrogen, lower alkyl group, acetyl group, amino group, hydroxyl group or carboxyl group] and must be soluble. For example, benzotriazole, 4-methylbenzotriazole, 4-hydroxybenzotriazole,
4-carboxybenzotriazole and the like.
The amount of benzotriazole or its derivative added is generally
It is 0.1-5 g / l, preferably 0.2-2 g / l. Benzotriazole or a derivative thereof has an effect of preventing dissolution of a copper base material by being used in combination with thiourea, and not causing any substitution precipitation even if the treatment is performed for a long period of time.

Further catechol 0.1 ~ 10g / l, preferably 0.5 ~ 3g / l
By the addition, the stripping time was shortened, and a synergistic effect was particularly observed during long-term treatment.

The aqueous stripper having the above composition according to the present invention can be used by any method of dipping or spraying,
The rate of peeling increases with processing temperature, but is typically 30
~ 45 ° C is preferred. Further, the stripping solution of the present invention can be similarly stripped of tin or a tin-lead alloy and those in which these two metals are present in any ratio.

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to these examples.

 Hereinafter, examples of the composition of the stripping solution according to the present invention will be described.

Example 1 2-hydroxypropanesulfonic acid 150 g / l sodium m-nitrobenzenesulfonate 20 g / l thiourea 3 g / l benzotriazole 2 g / l catechol 1 g / l Example 2 2-carboxyethanesulfonic acid 100 g / l m-nitrobenzene Sodium sulfonate 30 g / l 1-allylthiourea 2 g / l benzotriazole 1 g / l catechol 2 g / l Example 3 sulfosuccinic acid 120 g / l 2,4-dinitrobenzenesulfonate 50 g / l thiourea 3 g / l 4-methyl Benzotriazole 0.5 g / l catechol 1 g / l Example 4 p-phenolsulfonic acid 80 g / l sodium m-nitrobenzenesulfonate 15 g / l acetylthiourea 2.5 g / l 4-hydroxybenzotriazole 2.5 g / l catechol 0.5 g / l Example 5 2-Hydroxypropanesulfonic acid 70 g / l Sodium 2,4-dinitrobenzenesulfonate 50 g / l 1,3- Methyl-2-thiourea 2 g / l benzotriazole 1.5 g / l catechol 3 g / l Example 6 2-hydroxyethanesulfonic acid 100 g / l sodium m-nitrobenzenesulfonate 35 g / l thiourea 3 g / l 4-carboxybenzotriazole 0.5 g / l catechol 1 g / l Example 7 120 g / l benzenesulfonic acid 20 g / l sodium m-nitrobenzoate 20 g / l thiourea 2 g / l benzotriazole 2 g / l catechol 2 g / l Example 8 160 g 2-hydroxypropanesulfonic acid / l Sodium m-nitrobenzenesulfonate 45g / l 1,3-dimethyl-2-thiourea 1.5g / l 4-methylbenzotriazole 1g / l Catechol 2g / l Example 9 Methanesulfonic acid 100g / l m-nitrobenzenesulfone Sodium acid 20g / l Thiourea 3g / l Benzotriazole 1g / l Catechol 2g / l Example 10 m-xylene sulfonic acid 120g / l m-nitrobenzenesulfo The peel test of the tin-lead alloy layer was performed using an aqueous solution having the composition described in each of the above examples, 30 g of sodium phosphate / l thiourea 2 g / l benzotriazole 1.5 g / l catechol 1 g / l.

In this test, as a sample having a tin-lead alloy layer, 30
An epoxy copper-clad laminate (copper film thickness 35 μm) of × 50 mm, which is obtained by applying a solder plating of about 10 μm to copper is used. This sample was immersed in 100 ml of the aqueous solution of each Example at 25 ° C. with stirring,
The time required for peeling the tin-lead alloy layer of each sample and the amount of base copper eluted were measured.

For comparison, an aqueous solution having the following composition was prepared and tested in the same manner as described above.

Comparative Example 1 Methanesulfonic acid 100 g / l sodium m-nitrobenzenesulfonate 20 g / l thiourea 20 g / l The results obtained are shown in the following table.

As described above, in the solution of the present invention, the stripping time was shorter and the amount of copper eluted was smaller than in Comparative Example 1.

Example 11 Using the solutions of Example 1 and Comparative Example 1, the degree of re-deposition after 50 sheets of the above-mentioned solder plating samples were processed was compared. In Comparative Example 1, re-deposition was confirmed. In Example 1, there was no re-deposition, and a good glossy copper surface was exhibited.

[Effects of the Invention] As described above, according to the present invention, since the stripping time is shorter than that of the conventional stripping solution, an improvement in productivity can be expected, and a great effect that there is no adverse effect on the copper substrate was obtained.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-51-42028 (JP, A) JP-A-63-161178 (JP, A) JP-A-59-123773 (JP, A) JP-A 48-48 32483 (JP, A) JP-A-57-24295 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23F 1 / 10,1 / 14,1 / 30 H05K 3/26

Claims (1)

(57) [Claims] 1. A tin and tin-lead alloy layer which is an aqueous solution containing an aliphatic or aromatic organic sulfonic acid, an aromatic nitro-substituted compound, thiourea or a derivative thereof, benzotriazole or a derivative thereof and catechol, is selectively peeled off. Solution for you.