# US 9,518,327 B2 · Metal stripping additive, composition containing the same, and method for stripping metal by using the composition

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- Number: US 9,518,327 B2
- Document ID: US9518327B2
- Status: Granted
- Kind: B2
- Application number: 14/972,790
- Filed: 2015-12-17
- Published: 2016-04-14
- Granted: 2016-12-13
- Earliest claimed: 2013-02-22
- Assignees: Uwin Nanotech Co., Ltd.
- Applicants: UWin Nanotech. Co., Ltd.
- Inventors: Ching-Hsiang Hsu
- Web page: https://patentgrep.com/patent/US9518327B2

## CPC

- C23F 1/18: for etching copper or alloys thereof
- C22B 11/046: {from manufactured products, e.g. from printed circuit boards, from photographic films, paper or baths}
- C22B 15/0063: {Hydrometallurgy}
- C22B 23/04: {by wet processes (recovery or separation of nickel or cobalt using organic agents C22B3/00)}
- C22B 25/04: {by wet processes}
- C22B 25/06: from scrap, especially tin scrap (by electrolytic procedure C25C1/14)
- C23F 1/16: Acidic compositions (C23F1/42 takes precedence)
- C23F 1/30: for etching other metallic material
- H05K 3/22: Secondary treatment of printed circuits {(H05K3/1283 takes precedence; embedding circuits in grooves by pressure H05K3/107)}
- B08B 3/04: Cleaning involving contact with liquid
- B08B 3/044: {using agitated containers in which the liquid and articles or material are placed (by means of ultrasonic vibrations B08B3/12; cleaning casks or barrels by agitating B08B9/0817; mixers with shaking, oscillating or vibrating mechanisms B01F31/00)}
- C23F 1/28: for etching iron group metals
- H05K 2203/0789: Aqueous acid solution, e.g. for cleaning or etching
- H05K 2203/178: Demolishing, e.g. recycling, reverse engineering, destroying for security purposes; Using biodegradable materials
- C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- B08B: CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL

## Abstract

The present invention provides a metal stripping additive, composition containing the same, and method for stripping metal by using the composition. The metal stripping additive comprises a phosphate, a carbonate, and a component selected from at least one of citric acid or a derivative thereof, oxalate or a derivative thereof, malate or a derivative thereof. The metal stripping additive is used with nitric acid as the metal stripping composition of the present invention. The present method has advantages of being capable of stripping various metals, low corrosion, low toxicity, and being applicable under ambient temperature.

## Claims

### Claim 1

A method for stripping metal, comprising the following steps:
contacting an electronic element to be processed with a metal stripping composition;
wherein said metal stripping composition, comprising:
40 to 60% (v/v) of nitric acid; and
40 to 60% (v/v) of a metal stripping additive;
wherein said metal stripping additive, comprising:
10 to 40 wt % of phosphate, wherein said phosphate is monobasic potassium phosphate, dipotassium hydrogen phosphate, or a combination thereof;
3 to 15 wt % of carbonate, wherein said carbonate is sodium bicarbonate, potassium bicarbonate, sodium carbonate, or a combination thereof;
5 to 15 wt % of a component selected from at least one of citric acid or a derivative thereof, oxalate or a derivative thereof, or malate or a derivative thereof, wherein said citric acid or a derivative thereof is citric acid monohydrate, trisodium citrate monohydrate, or a combination thereof; and
5 to 30 wt % of a component selected from at least one of sodium hypochlorite or a derivative thereof, or pyridinesulfonic acid or a derivative thereof;
wherein said metal is gold, copper, nickel, tin, palladium, or a combination thereof;
wherein said composition has no harm to an object made of silver, stainless steel, titanium, plastic, or a combination thereof; and
wherein said electronic element is a central processing unit, a printed circuit board, a memory, a flip chip, a mobile phone, or a combination thereof.

### Claim 2 (depends on 1)

The method according to claim 1, wherein said contacting is accomplished by immersing said electronic element to be processed into said metal stripping composition.

### Claim 3 (depends on 1)

The method according to claim 1, wherein said contacting is accomplished at a temperature of 10° C. to 70° C.

### Claim 4 (depends on 1)

The method according to claim 1, wherein said contacting is accomplished in a time period of 10 sec to 900 sec.

### Claim 5 (depends on 1)

The method according to claim 1, having a stripping rate of 0.01 μm/min to 0.2 μm/min.

### Claim 6 (depends on 1)

The method according to claim 1, wherein said metal stripping additive comprises 10 comprises 10 to 40 wt % of monobasic potassium phosphate; 5 to 30 wt % of sodium hypochlorite; 3 to 15 wt % of sodium bicarbonate; and 5 to 15 wt % of citric acid monohydrate.