WO2000075404A1

WO2000075404A1 - Electrolytic removing agent for silver and method for electrolytic removing

Info

Publication number: WO2000075404A1
Application number: PCT/JP2000/002364
Authority: WO
Inventors: Akihiro Aiba
Original assignee: Japan Energy Corporation
Priority date: 1999-06-03
Filing date: 2000-04-12
Publication date: 2000-12-14
Also published as: JP2000345400A

Abstract

An electrolytic removing agent for silver comprising, as a main component, an oxo acid having one carboxyl group (-COOH) and one or more hydroxyl groups (-OH) or a salt thereof, in particular, one or more acid selected from the group consisting of salicylic acid, gallic acid, mandelic acid, tropic acid, glycolic acid, lactic acid, hydroacrylic acid, oxybutyric acid, glyceric acid and gluconic acid or a salt thereof; and a method for electrolytic removing using the same. The electrolytic removing agent for silver is advantageous in that a removing liquid prepared therefrom is stable and thus a bath using it has a long life, silver can be removed at a high current density (at a high speed), it does not adversely affect bonding properties, and it is free from the change of color and the occurrence of corrosion of a substrate material treated such as copper or a copper alloy, especially free from the occurrence of resin attack and free from the damage of appearance of a raw material and a residual silver plating.

Description

Description Electrolytic stripping agent for silver and electrolytic stripping method

The present invention relates to a silver electrolytic stripping agent and a silver electrolytic stripping method suitable for electrolytically stripping all or unnecessary portions of a plating film from silver-coated parts such as lead frames and connectors, and particularly to copper or copper. The present invention relates to a silver electrolytic stripping agent and a silver stripping method which have a good appearance of a silver-coated film and a residual silver-plated film when the metal is processed (material) such as a copper alloy and has no resist attack. Background art

Silver is often applied to electronic components such as semiconductor lead frames and connector pins. In such a case, plating is usually performed after masking is applied to the unnecessary portion, but not all masking is performed completely, and the silver plating film may protrude to the unnecessary portion. In such a case, it is necessary to remove the protruding silver coating.

As a method for removing the silver-coated film at an unnecessary portion, an electrolytic peeling method is known. In this electrolytic stripping method, a silver-coated material to be treated is immersed in a bath of a stripping agent (stripping solution), and the silver-coated film is stripped by electrolysis using the material as an anode. It is a method.

Conventionally, silver electrolytic strippers have been used in which concentrated nitric acid is added to sodium nitrate, those that contain cyanide, and those that contain sodium thiosulfate as the main component. (Metals such as alloys) to corrode (etch) to cause poor appearance, to erode the required silver-coated portion, and to use highly toxic cyanide compounds, wastewater treatment and poison control However, there were problems such as the need to pay attention to the handling of processing agents such as. Therefore, as a stripping agent that does not use dangerous concentrated sulfuric acid or highly toxic cyanide, succinimide or phthalimide and alkali metal hydroxide are the main components.

(Japanese Unexamined Patent Publication (Kokai) No. Hei 6-410900), those containing 2-pyrrolidone-15-carboxylic acid and those further containing saccharides in addition thereto. A release agent containing a cyclic acid imide containing one nitrogen atom in the molecule as a main component has been proposed. Further, a 5- or 6-membered ring compound having one NH— such as peracyl barbiturate and dartarimide (Japanese Patent Application Laid-Open No. 2-175825) and a hydantoin compound (Japanese Patent Application Laid-Open No. — 2 4 3 1 0 0) has been proposed.

The release agent consisting of a compound mainly composed of a cyclic acid imide containing one nitrogen atom in the molecule is easily hydrolyzed by alkali, and when the decomposed product accumulates in the bath, the surface becomes silvery. In addition, the passivation, discoloration, unevenness, etc., of the required part had an adverse effect on the silver-coated surface, the main component was consumed in a large amount, and the bath life was short.

In addition, when peeling was performed under conditions of high current density, there was another problem that the silver-plated surface was liable to be passivated or uneven.

In semiconductor devices, the bonding process is performed through die bonding or wire bonding. Die bonding is a process in which the semiconductor chip and the lead frame are bonded with epoxy resin.If epoxy pre-adhesion occurs, the die pad is contaminated with organic substances, resulting in poor ground bonding and loss of electrical connection to the outside. .

Wire bonding is a process in which the semiconductor chip and the inner lead of the lead frame are wired with Au, A1, etc. If the inner lead portion Ag surface is contaminated or the surface condition is very rough, Continuity cannot be obtained. Therefore, it is important that as it does not affect the volume bindings Japanese I ¹ production after silver peeling. The above described silver release agents did not satisfy these requirements.

From the above, the main component of the stripping solution is less likely to be hydrated, has a long bath life, enables silver to be stripped at a high current density, and has no adverse effect on the bonding characteristics. When a release agent is used, the material to be treated, such as copper or copper alloy, slightly dissolves and activates the surface of the material. Although there was a problem that discoloration or corrosion occurred during the process, the present inventors first developed a silver electrolytic stripping agent such as hydantoin and a silver electrolytic stripping agent such as hydantoin. An electrolytic peeling method (Japanese Patent Application Laid-Open No. 9-149010) was proposed. The silver electrolytic stripping agent and the electrolytic stripping method solve the above problems and have excellent characteristics as compared with the conventional method. However, since they are alkaline, they unfortunately erode the resist (resist attack). Therefore, when the object to be processed has a resist attached when the silver is peeled off, it cannot be used. Disclosure of the invention

From the above, it can be seen that the present invention provides a stable stripping solution and a long bath life, enables silver to be stripped at a high current density (high speed), and does not adversely affect the bonding characteristics. In addition, a silver electrolytic stripping agent that does not discolor or corrode the material to be processed, such as copper or copper alloy, does not particularly cause a resist attack, and does not impair the material and the remaining silver-plated appearance. The subject is an electrolytic stripping method.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and found that an alkaline silver release agent is liable to self-decompose and has a problem of eroding a resist. I got the knowledge that there is.

Based on these findings, the present invention

Silver electrolytic stripping agent characterized by containing a carboxylic acid or its salt as a main component having at least one carboxyl group (-C〇OH) and one hydroxyl group (-OH) in one molecule.

(2) One or more acids selected from the group consisting of salicylic acid, gallic acid, mandelic acid, tolovic acid, glycolic acid, lactic acid, hydroacrylic acid, oxybutyric acid, glyceric acid, and dalconic acid, or a salt thereof, as a main component. Characteristic silver stripper

3. The silver electrolytic stripping agent according to the above item 1 or 2, wherein the concentration of the acid or salt in the bath is 5 to 300 g / 1.

(4) The silver electrolytic stripping agent according to (1) or (2), wherein the concentration of the acid or salt in the bath is 20 to 120 g Z1. (5) The silver electrolytic stripping agent according to any one of (1) to (4) above, which contains 5 to 100 gZl of a boric acid or phosphate pH buffer.

(6) The silver electrolytic stripping agent according to (1) to (4) above, which contains a boric acid-based or phosphate-based pH buffer at 10 to 50 g / 1.

7 characterized in that it contains 10 gZl to 10 g / 1 of at least one surfactant selected from anionic, cationic and nonionic. Silver electrolytic stripping agent as described in each of ~ 6

(8) The silver electrolytic stripping agent according to any one of (1) to (6) above, which contains one or more surfactants selected from an anion-based, a cationic-based, and a non-ionic-based surfactant in an amount of 10 gZl to 1 g / 1.

9 lmg / L ~ 10 g / l of at least one discoloration inhibitor selected from triazonole, imidazonore, pyrronore, pyrazonore, thiazonole, thiol, carboxylic acid, and amine The electrolytic stripping agent for silver according to any one of the above items 1 to 8, characterized by containing L

10 Contains at least one discoloration inhibitor selected from triazonole, imidazonole, pyronoleno, pyrazonoleno, thiazonole, thiol, carboxylic acid, and amines in an amount of 1 OmgZL to 1 gZL. Silver electrolytic stripping agent according to any one of 1 to 8 above, characterized in that:

11 The material to be treated, whose surface is coated with silver, is used as the anode, and this is immersed in the bath for silver electrolytic peeling described in each of 1 to 10 above, with a current density of 0.1 to 50 AZdm

⁽²⁾ Electrolytic stripping method of silver characterized by electrolysis at a bath temperature of 5 to 80 ° C

(12) The method for electrolytic stripping silver according to the above (11), wherein the electrolysis is performed at a current density of 0.5 to 20 AZdm ² and a bath temperature of 10 to 50 ° C.

, I will provide a. Embodiment of the Invention

The silver electrolytic stripping agent and the electrolytic stripping agent method of the present invention are characterized in that silver to be treated is formed on various metal base materials such as copper, copper alloy, iron-nickel alloy such as 42 alloy, stainless steel, and nickel alloy. It can be applied to the case where silver or silver-based film is formed by plating or silver brazing, etc., when all or part of the film is peeled off.

The main component of the silver electrolytic stripping agent of the present invention is an oxyacid or a salt thereof having one or more carboxyl groups (one CO OH) and one or more hydroxyl groups (—OH) in the molecule, and specifically, salicylic acid and gallic acid. The main component is one or more acids selected from the group consisting of acids, mandelic acid, torovic acid, glycolic acid, lactic acid, hydroacrylic acid, oxybutyric acid, glyceric acid, and dalconic acid, or salts thereof. The chemical formula of these main components is shown in the following chemical formula 1.

An oxyacid or a salt thereof which does not have two or more carboxyl groups (-CO OH) or a hydroxyl group (-OH) in a molecule has a slow silver peeling rate, and has poor silver and material appearance after silver peeling. . It is desirable that the concentration of the acid or salt as a main component of the silver electrolytic stripping agent in the bath is 5 to 300 g Z1. If the concentration is too low, the electrolytic stripping rate of silver is low, and if the concentration is high, the electrolytic stripping effect saturates and is not effective.

Therefore, the above bath concentration is set to 5 to 300 g / 1. More preferably, the acid or salt concentration in the bath is preferably from 20 to 120 g Z1.

It is preferable that the silver electrolytic stripping agent of the present invention further contains a boric acid-based or phosphate-based pH buffer of 5 to 100 g Zl. Examples of the pH buffer include borate compounds such as potassium tetraborate, (ortho) borate, potassium diborate, sodium borate, and sodium pentaborate, such as borate and di, tetra, and pentaborate; Phosphoric acid or its salts, such as acids, orthophosphoric acid, pyrophosphoric acid can be used.

When the pH buffer is less than 5 g / 1, the pH buffer capacity is low, and there is no point in adding. If the concentration is more than 100 g / 1, the effect is saturated and there is no merit, so in order to have an effective pH buffering ability, it is added in the range of 5 to 100 g Zl. A more preferred range is from 10 to 50 g / 1. Chemical formula 1 Salicylic acid Hydroacrylic acid

OH HOCH ₂ CH ₂ COOH oc Oxybutyric acid

COOH CH ₃ CH ₂ CH (OH) COOH Gallic acid Glyceric acid

OH HOCH ₂ CH (OH) COOH

HO COOH

HC-OH

Mandelic acid

HC-OH

0-OH HC-OH

Tolovic acid

COOH glycolic acid

HOCH ₂ COOH lactic acid

CHaCH (OH) COOH Further, it is desirable to add 10 μgZ 1 to 10 gZ1 of one or more surfactants selected from anion type, cationic type and nonionic type to the silver electrolytic stripping agent of the present invention. Surfactants enhance the electrolytic stripping ability of silver. If the concentration is less than 10 μg, there is no effect of addition, and if the concentration exceeds 10 gZ1, the effect is saturated and there is no merit. In order to enhance the effect of the addition, it is more preferable to add 100 / z gZl to lg / l.

When copper or a copper alloy is used as the material to be treated, it is selected from triazole, imidazo mono, pyrro mono, pyrazole, thiazono, thiol, carboxylic acid, and amine. By containing lmgZL to 10gZL of a discoloration preventing agent of at least one kind, it is possible to simultaneously perform the peeling treatment of the material at the same time as the silver peeling.

If the amount is less than 1 mg / L, the effect of preventing discoloration is low, and if it exceeds 10 gZL, the effect is saturated and useless. A more effective range is between 1 Omg / L and 1 gZL.

The object having a silver film formed on its surface is immersed in a bath of the electrolytic stripping agent adjusted as described above, and the object is electrolyzed using the object as an anode. The material of the cathode is not particularly limited, but stainless steel is generally used.

The current density is from 0.1 to 50 A / dm ² , preferably from 0.5 to 1 OAZdm ² , based on the area of the peeled silver. If the current density is too low, the peeling rate is low, while if the current density is too high, passivation of silver tends to occur, which is not preferable.

The electrolysis is performed at a bath temperature of 5 to 80 ° C, preferably 10 to 50 ° C. If the temperature of the bath is too low, the stripping rate is low, while if it is too high, the bath becomes unstable, which is not preferable. It is desirable to stir the bath during the electrolysis, and particularly when the current density is high, the stirring speed should be high to suppress the passivation.

If a silver or silver coating is formed on a copper or copper alloy base material and a silver coating is formed on the copper or copper alloy base material by peeling, immerse in a bath containing the copper discoloration inhibitor (copper inhibitor). Then, electrolysis can be performed using the object to be processed as an anode under the above-described conditions.

It is also effective to immerse the object in a copper inhibitor solution after the electrolytic stripping of silver. If it is immersed in the solution for 5 seconds or more, the effect of preventing discoloration of copper is sufficient. When a part of the silver coating on the workpiece is to be peeled off with a release agent bath, the necessary silver coating that should not be peeled off should be masked or only the part to be peeled should be immersed locally. Such a method can be adopted.

If the silver coating on the required part is sufficiently thick and it can be peeled to the same extent as the unnecessary part to be peeled, the whole may be immersed.

When the lead frame is to be processed, the silver plating film in the necessary parts such as the pad part usually becomes a low current density part during electrolytic stripping, and the unnecessary part of the silver plating film around it becomes a high current part. Therefore, even if electrolytic peeling is performed without masking the required silver-coated portion, only the silver-coated film at the unnecessary portion can be removed. Examples and comparative examples

Next, examples of the present invention will be described in comparison with comparative examples. Note that this embodiment is merely an example, and the present invention is not limited to this example. That is, within the scope of the technical concept of the present invention, all aspects or modifications other than the present embodiment are included.

(Example)

Release agent baths having the compositions shown in Sample Nos. 1 to 10 in Table 1 were prepared. In the table, * 1 indicates polyoxyethylene nonylphenyl ether, and * 2 indicates peryl betaine.

Sample No. 1 contains salicylic acid 25 gZl as the main component, and further contains polyoxyethylenenoylphenyl ether 1 Omg / 1 as a surfactant and benzotriazoyl 5 OmgZ1 as a copper discoloration inhibitor. No. 2 contained gallic acid 10 g / 1, sample No. 3 contained mandelic acid 25 g / 1 as the main component, and further contained benzotriazole 5 Omg / 1 as a copper discoloration inhibitor. Sample No. 4 contained 50 g / 1 of toroic acid as the main component, and further contained 15 g / 1 of boric acid as a pH buffer. Sample No. 5 contained 25 g / 1 of glycolic acid as the main component and further contained an interface. Sample No. 6 containing 10 Omg / 1 stearic acid as the activator Sample No. 7 containing 25 g / l of lactic acid, Sample No. 7 containing 10 gZl of hydroacrinoleic acid, Sample No. 8 containing 50 gZ1 of oxybutyric acid as the main component, and boric acid 15 g / pH as a pH buffer l, 1 O OmgZ of butyric acid as a surfactant and 5 OmgZ 1 of hexadecyl mercuff as a copper discoloration inhibitor. Sample No. 9 contains 50 g Zl of glyceric acid as the main component, Laurinobetaine containing 1 OmgZ1 and Sample No. 10 containing 50 g / 1 of gnoreconic acid.

The main component of the release agent is an oxyacid or a salt thereof having one or more carboxyl groups (-COOH) and one or more hydroxyl groups (-OH) in the molecule.

The above is a sample of a lead frame made of copper with a 5 / in-thick partial silver coating on the pad portion (an unnecessary portion around the pad portion is also coated with silver). Immersed in each of the stripper baths, and the stripping conditions shown in Table 1, namely, pH: 4.0 to 6.0, current density: 1.0 to 5.0 A / dm ² , bath temperature: 25 ° C, Electrolysis was performed at a stirring speed of 0.5 m / sec and a time of 30 to 60 seconds, and unnecessary portions of the silver were electrolytically peeled off. Regarding the sampling after peeling, the silver surface appearance and the material appearance were evaluated by microscopic observation (X100). At the same time, the silver peeling rate and the resist attack were investigated. As a result, all of Sample Nos. 1 to L0 had good silver surface appearance and material appearance. As shown in Table 1, the silver peeling rate was 0.5 to 1.4 / m, which was slightly slower than the comparative example described later. Performance was shown.

With regard to the resist attack, which is a particularly important evaluation item, for Sample Nos .:! To 10, all of them were not observed at all and good results were obtained.

Although not shown in the table, the bonding characteristics were good, and the same results were obtained in a test 92 days after use. This confirmed that the bath life was good. o

(Comparative example)

Next, for Comparative Examples 1 and 2, release agent baths having compositions shown in Table 1 were similarly prepared. The electrolytic stripping bath of Comparative Example 1 contains 50 gZ1 of imidized succinate, and the electrolytic stripping bath of Comparative Example 2 contains 50 gZ1 of hydantoin. The pH is alkaline at 9.0 and 10.0, respectively. In the same manner as in the example, the stripping conditions shown in Table 1, ie, current density: 5.0 A / dm \ bath temperature: 25 ° C, stirring speed: 0.5 m / sec, and time: 30 seconds, electrolysis was performed. Unnecessary portions of silver were electrolytically peeled off.

As a result, both the silver surface appearance and the material appearance were good, and the silver peeling rate was 1.5 to 1.6 ^ um, which was satisfactory, but a resist attack was seen, and the production of electronic components using resist was observed. Was unsuitable. Industrial applicability

As described above, the silver stripping agent and the stripping method of the present invention are capable of stripping silver at a high current density (high speed) while maintaining a stable stripping solution and a long bath life. It does not adversely affect the characteristics.When the electrolytic stripping agent is used, the discoloration or corrosion of the material to be processed, such as copper or copper alloy, does not occur, and in particular, the resist attack does not occur. It has an excellent effect that the remaining silvery appearance is not impaired.

Claims

The scope of the claims

1. A silver electrolytic stripping agent characterized by containing, as a main component, an oxyacid or a salt thereof having one carboxyl group (—COOH) and one or more hydroxyl group (—OH) in the molecule.

2. One or more acids selected from the group consisting of salicylic acid, gallic acid, mandelic acid, tolovic acid, glycolic acid, lactic acid, hydroxyacrylic acid, oxybutyric acid, glyceric acid, and dalconic acid, or a salt thereof. An electrolytic stripping agent for silver, comprising:

3. The silver electrolytic stripping agent according to claim 1, wherein the concentration of the acid or salt in the bath is 5 to 300 gZl.

4. The electrolytic stripping agent for silver according to claim 1, wherein the concentration of the acid or salt in the bath is 20 to 120 g / 1.

5. The silver electrolytic stripping agent according to claim 1, further comprising 5 to 100 g Z1 of a boric acid-based or phosphate-based pH buffer.

6. The silver electrolytic stripping agent according to any one of claims 1 to 4, further comprising 10 to 50 g Z1 of a boric acid-based or phosphate-based pH buffer.

7. Electrolysis of silver according to claims 1 to 6, characterized in that it contains 10 / x gZl to 10 gZ1 of at least one surfactant selected from anion, cationic and nonionic. paint remover.

8. Electrolytic peeling of silver according to each of claims 1 to 6, characterized in that it contains 1 OO / gZl to 1 gZl of one or more surfactants selected from anion type, cationic type and nonionic type. Agent.

9, one or more discoloration inhibitors selected from triazols, imidazoles, piazoles, pyrazoles, thiazols, thiols, carboxylic acids, and amines lmgZL to l0 gZL The silver electrolytic stripping agent according to any one of claims 1 to 8, which is contained.

10. Contains 1 OmgZL to lg / L of at least one discoloration inhibitor selected from triazonole, imidazonole, pyrrolenole, pyrazonole, thiazole, thiol, carboxylic acid, and amine. The silver electrolytic stripping agent according to any one of claims 1 to 8, wherein:

11. The material to be treated, whose surface is coated with silver, is used as an anode, which is immersed in a silver electrolytic stripping bath according to claim 1 to obtain a pH of 7 or less and a current density of 0.1. ~ 50 AZ dm ² bath temperature 5 ~ 80. A method for electrolytically stripping silver, comprising electrolyzing with C.

12.112 to 7, the current density 0. 5~20 AZdm ^2, electrolytic stripping method of the silver according to claim 11, characterized in that the electrolysis at a bath temperature 10 to 50 ° C.