Resin plating method

Abstract

The present invention provides a resin plating method using an etching bath containing manganese as an active ingredient, the method being capable of maintaining stable etching performance even during continuous use. The resin plating method includes: an etching step, which uses a resin material-containing article as an object to be treated and etches the article using an acidic etching bath containing manganese; a catalyst application step, which uses palladium as a catalyst metal; and an electroless plating step; and the method further includes a step of maintaining the palladium concentration in the acidic etching bath at 100 mg/L or less.

Claims

1. A resin plating method comprising: an etching step, a catalyst application step, an electroless plating step, and a maintaining palladium concentration step; wherein an object to be treated by the resin plating method is an article comprising a resin, wherein in the etching step, the object to be treated is subjected to etching using an acidic etching bath containing manganese and one or more acid components; wherein the acid components comprise at least one selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, and organic sulfonic acid; wherein in the catalyst application step, a catalyst metal is palladium; and wherein the maintaining palladium concentration step maintains a concentration of palladium of up to 100 mg/L in the acidic etching bath; wherein the maintaining palladium concentration step is performed by one or more methods selected from the group consisting of: a method for reducing the palladium concentration in the acidic etching bath by cathodic electrolysis; wherein the cathodic electrolysis comprises electrolytic treatment by depositing palladium on a cathode in the etching bath; wherein the electrolytic treatment has a cathode current density of 0.1A/dm.sup.2 to 50A/dm.sup.2, and wherein, during the electrolytic treatment, the acidic etching bath comprises an etching solution having a solution temperature of 30° C. to 80° C.; and a method for reducing the palladium concentration by iodide addition to the acidic etching bath; wherein the iodide addition comprises adding to the etching bath at least one iodide selected from the group consisting of sodium iodide, iodic acid, iodates, periodic acid, and periodates, and then separating formed precipitate; and wherein a jig is a holder for the object to be treated.

2. The resin plating method according to claim 1, wherein the etching step, the catalyst application step and the electroless plating step are repeated at least two times or more upon the jig, wherein each repeat set of steps is upon a subsequent object to be treated, and wherein the maintaining palladium concentration step maintains the concentration of palladium throughout the entire resin plating method.

3. The resin plating method according to claim 1, wherein the concentration of palladium is up to 50 mg/L.

4. The resin plating method according to claim 1, wherein the concentration of palladium is up to 20 mg/L.

5. The resin plating method according to claim 1, wherein manganese in the etching bath is at a concentration of 0.01 to 100 g/L.

6. The resin plating method according to claim 1, further comprising a post-etching treatment, wherein the post-etching treatment is performed after the etching step but prior to the catalyst application step; and wherein, during the post-etching treatment, manganese is removed by using an inorganic acid or a reducing agent.

7. A method for controlling a resin plating etching bath, comprising maintaining palladium concentration in a manganese-containing acidic etching bath at up to 100 mg/L; wherein the manganese-containing acidic etching bath comprises at least one acid component selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, and organic sulfonic acid; and wherein the maintaining palladium concentration is performed by one or more methods selected from the group consisting of: a method for reducing the palladium concentration in the acidic etching bath by cathodic electrolysis; wherein the cathodic electrolysis comprises electrolytic treatment by depositing palladium on a cathode in the etching bath; wherein the electrolytic treatment has a cathode current density of 0.1A/dm.sup.2 to 50A/dm.sup.2, and wherein, during the electrolytic treatment, the acidic etching bath comprises an etching solution having a solution temperature of 30° C. to 80° C.; and a method for reducing the palladium concentration by iodide addition to the acidic etching bath; wherein the iodide addition comprises adding to the etching bath at least one iodide selected from the group consisting of sodium iodide, iodic acid, iodates, periodic acid, and periodates, and then separating formed precipitate; and wherein a jig is a holder for an object to be treated.

Description

DESCRIPTION OF EMBODIMENTS

(1) The present invention is described below in more detail with reference to Examples.

Examples 1 to 7 and Comparative Examples 1 to 7

(2) Flat plates (10 cm×5 cm×0.3 cm, surface area: about 1 dm.sup.2) of ABS resin (produced by UMG ABS, Ltd., trade name: UMG ABS3001M) were used as test pieces and attached to a jig coated with vinyl chloride. The test pieces were plated by the steps shown in Table 1 below. The volumes of treatment solutions used in the treatments were all set to 1 L, and the test pieces were washed with water between each treatment.

(3) TABLE-US-00001 TABLE 1 Treatment step Type of treatment solution Treatment conditions Degreasing Alkaline degreasing solution 40° C., immersion time: 5 min. treatment (produced by Okuno Chemical Industries Co., Ltd., ACE CLEAN A-220 bath) Etching treatment Etching bath shown in Table 2 below 68° C., immersion time: 20 min. Acid pickling 300 ml/L sulfuric acid 25° C., immersion time: 1 min. Catalyst application Palladium-tin colloidal catalyst solution 40° C., immersion time: 5 min. (produced by Okuno Chemical Industries Co., Ltd., catalyst C bath) Activation Aqueous solution containing 100 ml/L of 35% 35° C., immersion time: 5 min. hydrochloric acid Electroless nickel Electroless nickel plating solution 40° C., immersion time: 5 min. Plating (produced by Okuno Chemical Industries Co., Ltd., Chemical Nickel SEP-LF bath) Copper sulfate Copper sulfate plating solution Cathode current density: 3 A, plating (produced by Okuno Chemical Industries Co., Ltd., 25° C., plating time: 30 min. Top Lucina 2000 bath) Semi-bright nickel Semi-bright nickel plating solution Cathode current density: 3 A plating (produced by Okuno Chemical Industries Co., Ltd., 55° C., plating time: 20 min. ACNA NEO bath) Bright nickel plating Bright nickel plating solution Cathode current density: 3 A, (produced by Okuno Chemical Industries Co., Ltd., 55° C., plating time: 15 min. (KAI) ACNA B bath) Trivalent chrome Trivalent chromium plating solution Cathode current density: 10 A, Plating (produced by Okuno Chemical Industries Co., Ltd., 35° C., plating time: 4 min. Top Fine chromium WR bath)

(4) Table 2 to 5 below show the compositions of the etching baths used in the plating steps above.

(5) In the resin plating method comprising the treatment steps described above, the treatment for removing Pd from a jig, the treatment for removing Pd by cathodic electrolysis and/or the treatment for removing Pd by iodide addition were performed under the conditions shown in Tables 2 to 5 below.

(6) Among these treatments, the treatment for removing Pd from a jig was performed every time after each test piece plated with trivalent chrome was removed from the jig. The treatment for removing Pd by cathodic electrolysis and the treatment for removing Pd by iodine addition were performed in the etching bath used every 100 times of the resin plating treatment comprising the above treatment steps.

(7) Using the test pieces obtained in the Examples, the palladium concentration in the etching bath after treating 1000 test pieces (treatment area: 1000 dm.sup.2/L) and the peel strength of the obtained plating film were measured. The palladium concentration in the bath was measured by the ICP method. The peel strength was determined in the following manner. The test pieces plated by the above steps were dried at 80° C. for 120 minutes, and allowed to stand to cool to room temperature. Thereafter, parallel cuts with a width of 10 mm were made in the plating film, and the plating film was pulled in a direction vertical to the resin surface using a tensile tester (Autograph AGS-J 1 kN; produced by Shimadzu Corporation) to determine the peel strength. Tables 2 to 5 below show the results.

(8) Resin plating was performed in the same manner as in the Examples except that none of the treatment for removing Pd from a jig, the treatment for removing Pd by cathodic electrolysis, and the treatment for removing Pd by iodide addition was performed. These results are shown as Comparative Examples in Tables 2 to 5.

(9) TABLE-US-00002 TABLE 2 Comp. Ex. 1 Example 1 Comp. Ex. 2 Example 2 Composition of the etching bath 10 g/L manganese(III) phosphate + 4 g/L manganese(IV) oxide + 1200 g/L sulfuric acid 900 g/L phosphoric acid Treatment for Composition — 300 g/L — — removing Pd nitric acid from the jig Temperature 25 (° C.) Time (min.) 30 Treatment for Anode — — — Pt/Ti removing Pd in Cathode Zr the etching Cathode current 20 bath by density (A/dm.sup.2) cathodic Temperature 70 electrolysis (° C.) Time (min.) 60 Treatment for Iodide salt — — — — removing Pd in Amount added the etching (mg/L) bath by iodide Temperature addition (° C.) Time (min.) Pd concentration (mg/L) in the 120 30 114 55 bath after treating 1000 test pieces Peel strength Immediately 0.61 0.61 0.57 0.57 after preparing the bath 1000 dm.sup.2/L 0.11 0.58 0.09 0.51

(10) TABLE-US-00003 TABLE 3 Comp. Ex. 3 Example 3 Comp. Ex. 4 Example 4 Composition of the etching bath 3 g/L potassium 2 g/L manganese(III) fluoride + permanganate(VII) + 5 g/L sodium permanganate(VII) + 700 g/L sulfuric acid + 700 g/L sulfuric acid + 700 g/L phosphoric acid 600 g/L phosphoric acid Treatment for Composition — — — 300 g/L nitric acid + removing Pd 20 g/L ethylene from the jig diamine Temperature (° C.) 25 Time (min.) 60 Treatment for Anode — — — Pb removing Pd in Cathode Zr the etching bath Cathode current 30 by cathodic density (A/dm.sup.2) electrolysis Temperature (° C.) 70 Time (min.) 30 Treatment for Iodide salt — KI — — removing Pd in Amount added (mg/L) 200 the etching bath Temperature (° C.) 70 by iodide Time (min.) 30 addition Pd concentration (mg/L) in the bath after 150 20 190 15 treating 1000 test pieces Peel strength Immediately after 0.96 0.96 0.89 0.89 preparing the bath 1000 dm.sup.2/L 0.19 0.94 0.21 0.85

(11) TABLE-US-00004 TABLE 4 Comp. Ex. 5 Example 5 Comp. Ex. 6 Example 6 Composition of the etching bath 5 g/L manganese(IV) oxide + 5 g/L manganese(IV) oxide + 10 g/L sodium 10 g/L sodium permanganate(VII) + permanganate(VII) + 1000 g/L methanesulfonic acid 700 g/L sulfuric acid + 700 g/L methanesulfonic acid Treatment for Composition — — — 200 g/L hydrogen removing Pd peroxide + from the jig 10 g/L thiourea Temperature (° C.) 40 Time (min.) 90 Treatment for Anode — Pb — — removing Pd in Cathode Pt/Ti the etching bath Cathode current 15 by cathodic density (A/dm.sup.2) electrolysis Temperature (° C.) 70 Time (min.) 90 Treatment for Iodide salt — NaI — Sodium iodate removing Pd in Amount added (mg/L) 200 100 the etching bath Temperature (° C.) 70 70 by iodide Time (min.) 20 10 addition Pd concentration (mg/L) in the bath after 185 5 210 8 treating 1000 test pieces Peel strength Immediately after 0.91 0.91 0.99 0.99 preparing the bath 1000 dm.sup.2/L 0.18 0.88 0.12 0.94

(12) TABLE-US-00005 TABLE 5 Comp. Ex. 7 Example 7 Composition of the etching bath 10 g/L manganese(III) acetate + 4 g/L manganese(IV) oxide + 15 g/L potassium permanganate(VII) + 700 g/L sulfuric acid + 700 g/L methanesulfonic acid Treatment for Composition — 300 g/L nitric acid + removing Pd 20 g/L dimethylglyoxime from the jig Temperature 30 (° C.) Time (min.) 60 Treatment for Anode — Carbon removing Pd in Cathode Pt/Ti the etching bath Cathode current 10 by cathodic density (A/dm.sup.2) electrolysis Temperature 70 (° C.) Time (min.) 60 Treatment for Iodide salt — Potassium periodate removing Pd in Amount added 150 the etching bath (mg/L) by iodide Temperature 70 addition (° C.) Time (min.) 15 Pd concentration (mg/L) in the bath 205 0.2 after treating 1000 test pieces Peel strength Immediately after 1.02 1.02 preparing the bath 1000 dm.sup.2/L 0.13 1.02

(13) The above results clearly confirm that when the palladium concentration in the etching bath was maintained at 100 mg/L or less (Examples 1 to 7) by any one of the treatment for removing Pd from a jig, the treatment for removing Pd in an etching bath by cathodic electrolysis, and the treatment for removing Pd from an etching bath by iodide addition, substantially no reduction in peel strength occurred, and good etching power could be maintained even after treating 1000 test pieces (treatment area: 1000 dm.sup.2/L). In particular, when two or more of the above treatments were performed in combination (Examples 5 to 7), the palladium concentration in the etching bath could be maintained at a lower level, and good etching performance was exhibited.

(14) In contrast, when no treatment for reducing the Pd concentration was performed (Comparative Examples 1 to 7), the palladium concentration in the bath was increased to 114 to 210 mg/L after treating 1000 test pieces; etching power was reduced, compared with that immediately after preparing the bath; and significant reduction in peel strength of the obtained plating film was observed.

(15) These results clearly show that controlling the metal palladium concentration in an acidic etching bath containing manganese as an active ingredient at 100 mg/L or less can maintain good etching power over a long period of time.