|Publication number||US3646946 A|
|Publication date||Mar 7, 1972|
|Filing date||Jan 6, 1969|
|Priority date||Jan 6, 1969|
|Also published as||DE2000209A1, DE2000209B2|
|Publication number||US 3646946 A, US 3646946A, US-A-3646946, US3646946 A, US3646946A|
|Inventors||Caule Elmer J, Ford James A, Mclain Charles D, Saunders Stuart R|
|Original Assignee||Olin Mathieson|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (11), Referenced by (7), Classifications (15)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent Ford et a].
[ Mar. 7, 1972  COPPER ALLOY CLEANING PROCESS  Assignee: Olin Mathieson Chemical Corporation  Filed: Jan. 6, 1969  Appl. No.: 789,417
 US. Cl ..l34/3, 134/27, 134/28,
 Int. Cl. ..C23g l/04, (124g l/ 10, C23g H20  Field ofSearch ..l34/2, 3, 26, 27, 28, 29, 30
 References Cited UNITED STATES PATENTS 947,067 III 910 Thompson ..l34/28 2,125,458 8/1938 Ostermann ..1 34/3 2,284,743 6/1942 Kawecke et a1. 1 34/29 UX 2,318,559 5/1943 Percival ..l34/3 UX 2,395,694 2/ 1946 Spence et al. ..,l34/2 UX 2,726,970 12/1955 Toth ..134/3 3,003,896 10/1961 Kendall 134/3 3,121,026 2/1964 Beigay et al .134/2 1,049,054 12/1912 Coombs ..27 X/ 1,859,734 5/1932 George ..134/2 X 2,671,717 3/1954 Ferguson 1 34/2 Primary ExaminerMorris O. Wolk Assistant ExaminerBarry S. Richman Attorney-Richard S. Strickler, Robert H. Bachman, Donald R. Motsko and Thomas P. ODay  ABSTRACT A process for removing surface oxides from copper alloys. For example, these alloys which form, on annealing, A 1 0;, and related oxides are uniquely cleaned by a process which consists of a duplex treatment requiring a first immersion in a hot alkaline solution followed by a second immersion in a hot mineral acid solution.
12 Claims, No Drawings COPPER ALLOY CLEANING PROCESS Many copper base alloys, especially those containing aluminum, form complex thermal oxides which are difficult to remove by conventional copper cleaning techniques.
For example, a copper alloy containing about 66 percent copper, 1.55 percent aluminum, 1.0 percent iron, balance essentially zinc, forms a refractory thermal oxide during annealing that cannot be reliably removed using ordinary cleaning procedure. The metal cannot be reproducibly soldered or electroplated because of the residual annealing oxide.
in addition to causing soldering and plating problems, excessive residual A1 can cause excessive die wear and failure during fabrication operations.
It is the object of the present invention to achieve easy and reproducible removal of these films.
lt is another object of the present invention to remove those films within the confines of existing copper-base alloy cleaning equipment.
Other objects and advantages will become apparent from the following description.
In accordance with the present invention the foregoing objects are readily obtained. The process of the present invention comprises: immersing the surface to be cleaned in an aqueous alkaline solution having apH above 10 for at least two (2) seconds, with the solution being at a temperature of from 100 F. to the boiling point; and then immersing the surface to be cleaned in an aqueous mineral acid solution at a temperature of from 75 to 200 F. for from two (2) seconds to minutes, said solution having an acid equivalent to an H 50, solution of 3 to 50 percent by volume. Preferably, a conventional water rinse or air wipe is performed between steps and after the final step.
The exact time and the exact bath temperature in each of these two steps is determined by the type of annealing operation and the character of the resulting oxide including its thickness and constitution.
The process is suitable to both continuous cleaning of strip and to batch cleaning of fabricated parts.
Following the described cleaning process, copper base alloys coated with complex oxides can be successfully soldered and electroplated because the residual oxide resulting from annealing has been removed.
The process of the present invention is effective for any copper basc alloy. The present process is especially effective with copper alloys containing as alloying additions: aluminum, from 0.5 to 12 percent; and silicon, from 0.5 to 5 percent. The process of the present invention is particularly useful with respect to copper alloys bearing: complex oxides; alumina:
spinel type oxides, such as copper aluminate and zinc aluminate; nickel oxides; etc.
As indicated hereinabove, the process of the present invention utilizes a duplex treatment requiring a first immersion in a hot alkaline solution followed by a second immersion in a hot mineral acid solution.
Concerning the first alkaline solution, any alkaline solution may be used which has a pH above and preferably a pH from 1 1 to 14. Preferred solutions which may be used depend, of course, upon the particular alloy and the results desired. ln general, caustic soda is the preferred alkaline solution, but others may be readily employed such a lithium or potassium hydroxide, for example. The alkaline solution should be maintained at a temperature of from 100 F. to the boiling point, and preferably at a temperature of from 160 F. to the boiling point. The copper alloy to be cleaned should be immersed in the solution for at least 2 seconds and preferably for from 5 seconds to 1 minute. Naturally, longer treatment times may be employed, but in general no advantage is obtained thereby. Generally, the treatment time should be under 10 minutes. Naturally, temperature and time are related and the exact treatment conditions are dependent upon the alloy used and the results desired.
The second immersion in acid may employ any mineral acid solution having an acid equivalent to an H 80 solution of3 to 50 percent by volume. In general, any mineral acid may be used with sulfuric acid being preferred. Others which may be used include nitric and hydrochloric, for example. The preferred solution has an acid equivalent to an H SO, solution of from 5 to 20 percent by volume. The mineral acid solution should be maintained at a temperature of from 75 to 200 F. and preferably at a temperature of from to 175 F. A treatment time of at least 2 seconds should be employed and preferably from 5 seconds to 1 minute. The mineral acid treatment should generallynot exceed 5 minutes as in-some cases there is obtained an undesirable blush color for treatment times in excess of about 5 minutes. The alloy is, of course, effectively cleaned; however, the color is undesirable commercially.
Naturally, both the first and second solutions should be aqueous solutions.
Preferably, a conventional water rinse or air wipe is preferred between the steps and after the final step.
The present invention will be more readily apparent from a consideration of the following illustrative examples.
EXAMPLE I In this example, the following alloys were processed.
Copper, essentially balance The alloys were processed as shown in Table 11, below, which shows bath concentration and residence times and temperatures for air, bell, and strip annealing oxides for each alloy.
Air annealing was carried out as follows: The alloy sheet was brought to a temperature of about l,l00 F. in several minutes and held at that temperature for 2 hours. The alloy was then cooled to room temperature by removal from the furnace. Air had access to the interior of the furnace.
Bell annealing refers to annealing in whichsheet material was placed in a closed furnace. Air was displaced with an atmosphere resulting from hydrocarbon combustion. The furnace was brought to a temperature of about l,l00 F. over a period of several hours. The furnace was held at temperature for a period of several hours, after which it was slowly cooled over several hours to a temperature at which the furnace could be opened without promoting excessive oxidation.
1n strip annealing, a strip is continuously fed through a furnace heated, for example, by gas burners or resistance heat and continuously exits therefrom with a gas atmosphere in the furnace produced by burning propane to eliminate oxygen. The rate of travel is adjusted so that residence time in the furnace is sufficiently low that the strip reaches the desired temperature, l,100 F,, in this case.
Temp.Boiling pt. H,SO,a-l2% vol Temp. F.
Time in each30 sec.
Temp-Boiling pt. H,SO, 12% vol Temp. 150 F.
Time in each30 sec.
Temp-Boiling pt. H,SO,-12% vol Temp. I50 F.
Time in each-30 sec.
Treatment Following Bell Anneal NaOH-pH 14 Temp-Boiling pt.
Temp. 150 F.
NaOH-pH 13 Temp-Boiling pt. H,SO a-12% vol Temp. 150 F.
Time in cach-l5 see. Time in eachsec.
NaOH-pH 14 Temp-Boiling pl. H,SO l- 12% vol Temp. l50 F.
Time in each-5 sec.
NaOHpH l4 Temp-Boiling pt. H,SO,12% vol Temp. 150 F.
Time in each-5 sec.
It should be noted that the alkaline immersion for air annealed alloy C for short treatment times should use lithium hydroxide. In addition, an acid bath composition modification was used for the bell annealed alloy C treatment. In this latter case, sodium dichromate should be added to the acid bath in the range of from 1 to 8 ounces per gallon in order that the last 25 Angstroms of A1 0 might be removed.
This acid dichromate bath modification can be used with the other alloys; however, it produces an etched surface which appears hazy or frosty; an undesirable surface condition for the final product. This is not important in most instances since further cold rolling and strip annealing will produce a bright surface.
It was found that after the cleaning process described above, all alloys were successfully soldered after cleaning. By comparison, prior to cleaning, none of these alloys could be soldered.
EXAMPLE ll The efficacy of the foregoing cleaning procedure has been accurately demonstrated by utilizing surface capacitive measurements before and after cleaning. It has been found that the cleaning technique described effectively increases the surface capacitance, a parameter linked to the thermal oxide thickness and solution double layer thickness, to a value indicative of only the surface double layer capacitance produced by immersion of the test specimen in the electrolytic solution used in capacity measurement. For example, a specimen of alloy C before cleaning was covered by a film of oxide which capacitance measurements allowed to be calculated 88 Angstroms thick. After cleaning, the thickness of oxide and double layer equivalent was 4.8 Angstroms. Correction for the double layer reduces any total value less than 8 Angstroms to zero thickness of oxide. Effectively, the capacitance bridge showed that the surface was cleaned. This was confirmed by the solder test.
This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalence are intended to be embraced therein.
What is claimed is:
l. A process for cleaning a copper base alloy surface having a thermally formed oxide thereon, comprising: immersing the surface to be cleaned in an aqueous alkaline solution having a pH of from 1 1 to 14 at a temperature from 160 F. to the boiling point of said aqueous alkaline solution for a period of time of at least 2 seconds; and then immersing the surface to be cleaned in an aqueous mineral acid solution at a temperature of from 75 to 200 F. for from 2 seconds to 5 minutes, said acid solution having an acid equivalent to an H 50, of 3 to 50 percent by volume.
2. A process according to-claim 1 in which the copper base alloy surface has a complex oxide thereon.
3. A process according to claim 1 in which the temperature of the acid bath is from to 175 F.
4. A process according to claim 1 in which said alkaline solution contains lithium hydroxide.
5. A process according to claim 1 in which said alkaline solution contains sodium hydroxide.
6. A process according to claim 1 in which the acid solution consists of an aqueous solution of H 80 7. A process according to claim 1 in which sodium dichromate is present in the acid solution in an amount of from 1 to 8 ounces per gallon.
8. A process according to claim 1 in which the thickness of the oxide after cleaning is less than 10 Angstrom units.
9. A process according to claim 1 in which the oxide is at least in part a spinel.
10. A process according to claim 1 wherein the temperature ofsaid alkaline solution is at the boiling point.
11. A process for cleaning a copper base alloy surface having a thermally formed oxide thereon, comprising: immersing the surface to be cleaned in an aqueous alkaline solution having a pH of from 1 1 to 14 at a temperature from F. to the boiling point of said aqueous alkaline solution for from 5 seconds to 1 minute; and then immersing the surface to be cleaned in an aqueous mineral acid solution at a temperature from 125 to F. for a period of from 5 seconds to 1 minute, said acid solution having an acid equivalent to an H 80 solution of5 to 20 percent by volume.
12. A process according to claim 11 wherein the temperature of said alkaline solution is at the boiling point. 7
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US947067 *||Sep 30, 1908||Jan 18, 1910||Int Nickel Co||Method of treating nickel-copper alloys.|
|US1049054 *||Jul 8, 1911||Dec 31, 1912||Frank E Coombs||Process of removing scale.|
|US1859734 *||Dec 21, 1928||May 24, 1932||Electro Metallurg Co||Method of removing oxide coatings from metals|
|US2125458 *||Sep 28, 1937||Aug 2, 1938||Georg Von Giesche S Erben||Method of bright-pickling articles of copper-zinc alloys|
|US2284743 *||Mar 28, 1941||Jun 2, 1942||Beryllium Corp||Pickling agent for copper-beryllium alloys|
|US2318559 *||Apr 30, 1941||May 4, 1943||Monsanto Chemicals||Material for and process of pickling copper or its alloys|
|US2395694 *||Jun 2, 1944||Feb 26, 1946||Hooker Electrochemical Co||Processes for removing oxide from the surface of metals|
|US2671717 *||Aug 29, 1950||Mar 9, 1954||Gen Electric||Chemical brightening of aluminum|
|US2726970 *||Jun 1, 1954||Dec 13, 1955||Ford Motor Co||Deoxidizing copper base metal parts|
|US3003896 *||Jan 17, 1958||Oct 10, 1961||Rohr Aircraft Corp||Process and composition for treating aluminum alloys|
|US3121026 *||Jul 15, 1960||Feb 11, 1964||Titanium Metals Corp||Descaling metals and alloys with aqueous potassium hydroxide at relatively low temperature|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3905808 *||Mar 21, 1973||Sep 16, 1975||Madison Ind Inc||Process for the recovery of metallics from brass skimmings|
|US4361445 *||Jun 26, 1981||Nov 30, 1982||Olin Corporation||Copper alloy cleaning process|
|US4581102 *||Aug 20, 1984||Apr 8, 1986||Olin Corporation||Copper-base alloy cleaning solution|
|US4600443 *||Oct 1, 1984||Jul 15, 1986||Kennecott Corporation||Process for removing surface oxides from a copper-base alloy|
|US4769345 *||Mar 12, 1987||Sep 6, 1988||Olin Corporation||Process for producing a hermetically sealed package for an electrical component containing a low amount of oxygen and water vapor|
|US5052421 *||Jul 27, 1990||Oct 1, 1991||Henkel Corporation||Treatment of aluminum with non-chrome cleaner/deoxidizer system followed by conversion coating|
|US7699936||Jun 24, 2005||Apr 20, 2010||Gm Global Technology Operations, Inc.||Composition and method for surface treatment of oxidized metal|
|U.S. Classification||134/3, 134/27, 134/28, 134/29, 134/41, 134/30|
|International Classification||C25D5/24, C23G1/02, C23G1/10, C23G1/14, B23K1/20, C23G1/20, C23G1/00|