CA1117853A - Copper alloy cleaning process - Google Patents
Copper alloy cleaning processInfo
- Publication number
- CA1117853A CA1117853A CA000334174A CA334174A CA1117853A CA 1117853 A CA1117853 A CA 1117853A CA 000334174 A CA000334174 A CA 000334174A CA 334174 A CA334174 A CA 334174A CA 1117853 A CA1117853 A CA 1117853A
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- Prior art keywords
- solution
- process according
- ferric sulfate
- seconds
- immersed
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
- Chemical Treatment Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A rapid and effective surface cleaning process for copper alloys, particularly copper alloys containing aluminum and other metals tending to form surface coatings of refractory oxides during annealing treatments. The process consists of treating such alloys or articles fabricated thereof for a short time in a hot aqueous solution of an alkali hydroxide and rinsing with water. The alloy is then immersed for a short time in a hot aqueous solution of ferric sulfate, or other ferric salt of a mineral acid, followed by rinsing with water.
A rapid and effective surface cleaning process for copper alloys, particularly copper alloys containing aluminum and other metals tending to form surface coatings of refractory oxides during annealing treatments. The process consists of treating such alloys or articles fabricated thereof for a short time in a hot aqueous solution of an alkali hydroxide and rinsing with water. The alloy is then immersed for a short time in a hot aqueous solution of ferric sulfate, or other ferric salt of a mineral acid, followed by rinsing with water.
Description
This invention relates to the surface cleaning of copper base alloys and provides a rapid and effective two-stage process for removing surface oxide deposits formed on the metal, as during annealing treatments. In the case of copper alloys contalning aluminum and other readily oxidizable metals such as iron, cobalt, nickel, zinc or silicon, a resistant metal oxide surface film is formed during annealing treatments at elevated temperatures, applied for a period of time sufficient to relieve strains imposed during mechanical operations, as in the rolling to metal ingots to elongated strip of reduced thickness or for the fabrication of metal parts and articles. Such surface coatings of oxlde are produced even when the anneallng is carried out in the presen-ce of a protective atmosphere, such as may be prepared by the partial combustion of a hydrocarbon, because the active metals present in the alloy will react with oxygen that is present in the free state or as moisture or as an oxide of carbon to form refractory oxides. When various metal oxides are thus formed, they often tend to combine with each other to form complex metal oxides, such as spinels, of refractory nature, which at times are extremely resistant to removal by conventional cleaning methods. Unless such surface oxide films are thoroughly removed, however, subsequent surface finishing treatments, such as soldering, electroplating, or pressure bonding with other metals, will generally yield unsatisfactory results because of the resulting poor adhesion.
While numerous proposals have been made in the past for single and multi-stage cleaning treatments, they have generally proved ineffective for the successful cleaning of copper alloys containing aluminum and other metals tending to form refractory oxides in thick surface layers. Although some of these procedures mayj if prolonged, finally result in the removal of such layers, an undesirable extent of pitting and etching of the metal surface is found to occur simultaneously during such extended treatments, which may render them unsuitable for the intended purpose. Such unsatisfactory results characterize attempts to remove thick refractory oxide layers from various copper alloys containing aluminum and other active metals by single treatments with aqueous pickling solutions, such as aqueous solutions of sulfuric acid, sulfu-ric acid and alkali dichromate, sulfuric acid and ferric sulfate, as described on Pages 308-309 of "The Chemical ; Formulary", Vol. IX, 1951, Chemical Publishing Co.~ Inc.
Brooklyn, ~.Y.
Accordingly, it is the principal object of this invention to provide a rapid and effective treatment for the removal of refractory complex metal oxide films, even of unusually high thickness, from the surface of copper base alloys.
- A further object of the invention is to provide a process that is readily applied and is effective for such removal without causing harmful surface etching or pitting of the metal.
In accordance with the present invention 9 there is provided a process for cleaning the surface of a copper base alloy having a surface layer of thermally formed complex metal oxide of a refractory nature, comprising immersing the surface in an aqueous alkaline solution having a pH of 11 to 14 and heated to a temperature of about 40C to its boiling point for
While numerous proposals have been made in the past for single and multi-stage cleaning treatments, they have generally proved ineffective for the successful cleaning of copper alloys containing aluminum and other metals tending to form refractory oxides in thick surface layers. Although some of these procedures mayj if prolonged, finally result in the removal of such layers, an undesirable extent of pitting and etching of the metal surface is found to occur simultaneously during such extended treatments, which may render them unsuitable for the intended purpose. Such unsatisfactory results characterize attempts to remove thick refractory oxide layers from various copper alloys containing aluminum and other active metals by single treatments with aqueous pickling solutions, such as aqueous solutions of sulfuric acid, sulfu-ric acid and alkali dichromate, sulfuric acid and ferric sulfate, as described on Pages 308-309 of "The Chemical ; Formulary", Vol. IX, 1951, Chemical Publishing Co.~ Inc.
Brooklyn, ~.Y.
Accordingly, it is the principal object of this invention to provide a rapid and effective treatment for the removal of refractory complex metal oxide films, even of unusually high thickness, from the surface of copper base alloys.
- A further object of the invention is to provide a process that is readily applied and is effective for such removal without causing harmful surface etching or pitting of the metal.
In accordance with the present invention 9 there is provided a process for cleaning the surface of a copper base alloy having a surface layer of thermally formed complex metal oxide of a refractory nature, comprising immersing the surface in an aqueous alkaline solution having a pH of 11 to 14 and heated to a temperature of about 40C to its boiling point for
2-a period of two seconds to not more than ten minutes, and then immersing the surface in 0.5 to 3 N. aqueous solution of ferric sulfate containing no added mineral acid at a temperature of 25 to 95C for a period of two seconds to not more than ten minutes.
The process of the invention involves the combina-tion of the following two-step treatrnent, neither step alone being effective to produce a clean metal surface satisfactory for soldering or other surface treating process. The oxide-coated copper-base article or strip is first immersed in a stirred aqueous alkaline solution, as of sodium, potassium or lithium hydroxide, having a pH above 10, for at least two seconds at a temperature of about 40C to the boiling point, and, after draining and rinsing with water, is then submerged in a stirred aqueous solution of ferric sulfate, or similar ferric salt of a mineral acid containing no added mineral acid, at a ferric salt concentration of 0.5 to 3.0 ~, for at least two seconds, preferably for five to sixty seconds, at a temperature of 25 to 95C, prefera~ly at 60 to 90C.
~ Each step should be followed by draining the solution from the article or subjecting it to blowing with air streams, and removing the residual solution by rinsing with waterO
The need for such improved cleaning process arose during the use of the duplex process of U.S. Patent 3,646,946 issued March 7, 1972, consisting of first immersing annealed metal in a hot alkaline solution and then treating with a hot solution of mineral acid, preferably a 12% by volume aqueous sulfuric acid solution. Effective results were attained thereby in removing complex oxide films and producing a surface displaying excellent solderability in a variety of f~
annealed copper base alloys, such as Cu, Fe and Al; Cu, Al, Si, Co and P, and C.D.A. Alloy 688 containing 22.7% Zn, 3.4%
Al, 0.4% Co, and balance e~sentially Cu. The above duplex treatment accomplished the substantially complete removal of complex ~i,,, -3a-333 ~ 5~
oxide film ln annealed metal shown ~y capacitance measure-ments to have sur~ace oxide films up to about 105 A in thickne s. However~ when the latter alloy was annealed under more severe conditions and having surface oxide films up to 140 to 160 A in thickness, such as resulted from bell annealing treatments whlch were prolonged or carried out in a less ~rotective atmosphere, ~he above duplex cleaning process displayed subs~antiall~ decreased effectiveness. Thereb~, the need for an improved cleaning procedure ~rose as an urgent pro~lem, which has now been solved through the provision o~ the novel second step of the duplex treatment described below.
- DE~AILED DESCRIPTION
It was theorized that a solution having proper oxida-tive power and solvent action on complex oxide films might be found through measurements o~ the rate of weight loss of the basis metal therein. This mode of attack has been successful ln establishing an effective second treatment, although the generality o~ such parallel behavior is quite uncert in and unproved. A study o~ weight loss measurements was carried out in the above Alloy 688 at 50C and 6~C immersed for periods o~ lO, 20, and 30 seconds in a l N. aqueous solution of ~erric sul~ate containing no added acid, and comparison solutions con-taining 1 N. ~erric sulfate and added sul~uric acid at con-centrations o~ l N., 3 N., and 5 N. At each temperature, the loss in weight per unit area, expressed as micrograms per square centimeter, wa3 linear with time, in seconds, and ~ielded the values for dissolving rate listed in Table I.
34~ 901 TA~LE I
Solution ~i'ss~l~i'n~_R'at'eCu' grams ~e'r 'cm2'~er sec.
'50'C ''65C
1 N.Fe2(S04)3 45- 62.8 1 N.~e2Cso4)3 ~
1 N.H2S04 44.4 58.0 1 N.Fe2(S04)3 ~
The process of the invention involves the combina-tion of the following two-step treatrnent, neither step alone being effective to produce a clean metal surface satisfactory for soldering or other surface treating process. The oxide-coated copper-base article or strip is first immersed in a stirred aqueous alkaline solution, as of sodium, potassium or lithium hydroxide, having a pH above 10, for at least two seconds at a temperature of about 40C to the boiling point, and, after draining and rinsing with water, is then submerged in a stirred aqueous solution of ferric sulfate, or similar ferric salt of a mineral acid containing no added mineral acid, at a ferric salt concentration of 0.5 to 3.0 ~, for at least two seconds, preferably for five to sixty seconds, at a temperature of 25 to 95C, prefera~ly at 60 to 90C.
~ Each step should be followed by draining the solution from the article or subjecting it to blowing with air streams, and removing the residual solution by rinsing with waterO
The need for such improved cleaning process arose during the use of the duplex process of U.S. Patent 3,646,946 issued March 7, 1972, consisting of first immersing annealed metal in a hot alkaline solution and then treating with a hot solution of mineral acid, preferably a 12% by volume aqueous sulfuric acid solution. Effective results were attained thereby in removing complex oxide films and producing a surface displaying excellent solderability in a variety of f~
annealed copper base alloys, such as Cu, Fe and Al; Cu, Al, Si, Co and P, and C.D.A. Alloy 688 containing 22.7% Zn, 3.4%
Al, 0.4% Co, and balance e~sentially Cu. The above duplex treatment accomplished the substantially complete removal of complex ~i,,, -3a-333 ~ 5~
oxide film ln annealed metal shown ~y capacitance measure-ments to have sur~ace oxide films up to about 105 A in thickne s. However~ when the latter alloy was annealed under more severe conditions and having surface oxide films up to 140 to 160 A in thickness, such as resulted from bell annealing treatments whlch were prolonged or carried out in a less ~rotective atmosphere, ~he above duplex cleaning process displayed subs~antiall~ decreased effectiveness. Thereb~, the need for an improved cleaning procedure ~rose as an urgent pro~lem, which has now been solved through the provision o~ the novel second step of the duplex treatment described below.
- DE~AILED DESCRIPTION
It was theorized that a solution having proper oxida-tive power and solvent action on complex oxide films might be found through measurements o~ the rate of weight loss of the basis metal therein. This mode of attack has been successful ln establishing an effective second treatment, although the generality o~ such parallel behavior is quite uncert in and unproved. A study o~ weight loss measurements was carried out in the above Alloy 688 at 50C and 6~C immersed for periods o~ lO, 20, and 30 seconds in a l N. aqueous solution of ~erric sul~ate containing no added acid, and comparison solutions con-taining 1 N. ~erric sulfate and added sul~uric acid at con-centrations o~ l N., 3 N., and 5 N. At each temperature, the loss in weight per unit area, expressed as micrograms per square centimeter, wa3 linear with time, in seconds, and ~ielded the values for dissolving rate listed in Table I.
34~ 901 TA~LE I
Solution ~i'ss~l~i'n~_R'at'eCu' grams ~e'r 'cm2'~er sec.
'50'C ''65C
1 N.Fe2(S04)3 45- 62.8 1 N.~e2Cso4)3 ~
1 N.H2S04 44.4 58.0 1 N.Fe2(S04)3 ~
3 N H2S4 41.3 53.8 1 N.Fe2~S04)3 ~
5 N~2S4 36.4 48.3 These results sho~ed quite unexpectedly that the aqueous ~erric sulfate solution with no added acid, at both temperatures, dissolves the metal at a higher rate than any of the solutions containing added acid, and further~ that the dissolving rate at both temperatures decreases as the concentration of added acid is increased.
It was subsequently shown in duplex cleaning treat-ments of annealed metal having a surface oxide film up to 160 A thick, wherein the treatment consisted o~ a Lirst immersion in a hot alkaline solution7 followed by a second lmmersion in a hot ferric sulfate solution containing no added acid, that the removal o~ oxide film was accomplished effectively, as substantiated by the applicable tests, including the solderability test. The cleaning action is as thorough and complete, or better, than when added sul-furic acid is present in the ferric sul~ate solution, thereby accomplishing at least equivalent resul~s more ~ convenlentl~y and at decreased expense.
: The initial treatment with hot alkaline solution is carried out at a temperature o~ about 40C to the boiling ~ 9015 point and preferablyg at a temperature of about 70C to the ~oiling point, the solution having a pH abo~Je 10, preferably 11 to 14. The solutlon is preferably of caustic soda, but other alkali hydroxldes as of potassium or lithium, or mixtures may be used within the above-stated pH range. Immersion of the copper alloy should be for at least two seconds and prefera~ly, for five to six~y seconds. The treatment time may be prolonged, particularly at temperatures near the lower lim~t of the abo~e range, but generally should ~e for ten minutes or less, as longer times usually provide no added advantages. Optimum treating times and conditions may be determined in ac-cordance with the particular alloy and the results desired.
The second step of the duplex treatment is best ef-fected by immersion of the copper alloy strip or article, after the alkaline solution has been drained therefrom and rinsed with water9 in a hot 0.5 to 3 N., best 1.25 to 2 N., solution of ferric sulfate, without added acld at a tem-perature of about 25 to 95C,~est 65 to 90C, for at least two seconds, and preferably for five to sixty seconds, and generally for not over ten minutes.
Ferric sulfate for such treatment may be replaced in whole or in part by other soluble ferric salts, as for example b~y ferric ammonium sulfate or ferric nitrate, generally with the obtainment of equivalent results in t~e obtainment of clean and solderable copper alloy sur-faces. It may oe noted that aqueous solutions of ferric sulfate, typical of soluble ferric salts of strong acids, display a pH of about 1 at 0.5 N. solution, decreasing~
close to linearly, to about 0.5 at 2 N. and to about 0.35 at 3 N.
The efficacy of a duplex treatment in accordance with t~is invention, as above outlined, i5 illustrated in the following spec fic example, contrasting its successful results wit~ the ineffective cleaning provided by the process taught in U.S. Patent 3,646,946, the closest prior art duplex treatment.
EXAMPLE I
Sheets of C.D. Alloy 688 Ccontaining 22.7% Zn, 3.4%
Al, 0.4% Co, and balance essentially Cu) were bell an-nealed at about 600C in a closed furnace containing an ~; atmosphere produced by the partial combustion of hydro-carbons to produce two lots of annealed sheet, the first having a surface oxide layer ranging 95 to 105 A in thickness and the second having a sur~ace oxide la~er ranging 140 to 160 A ~n thickness.
Samples of the two lots were given a first i.~mersion ~reatment in boiling caustlc soda solution having a pE OL
14 for twenty seconds, drained, and washed with water.
Samples of the two lots, treated as above, were then sub~ected to immersion for twenty seconds in one o~ the following three solutions:
(l) 1.5 N. aqueous ferric sulfate solution, con-taining no added acid, at 65~C.
(2) 12% b~ vol. aqueous sulfuric acid solution at 65C.
(3) 12% b~y vol. aqueous sulfuric acid solution con-taining 4 oz. per gallon o~ sodium dichromate.
~ollowing the twentJ second immersion, the samples were drained, washed with water, and dried.
7~3~ ~ 9015-~3 Solderability tests applied to the treated samples of the first lot (95 to 105 ~ oxide layer~ revealed that those treated ~ith solution Cl~ and (3) were solderable, while those treated ~ith solution (2) could not be soldered ef~ectively .
Solderability tests applied to the treated samples o~ the second lot C140 to 160 A oxide layer) revealed that those ~reated with solution Cl ) ~ere solderaole, while those treated with solutions (2) and (3) could not be ef~ectively soldered.
Furthermore, capacitance tests on the above-treated samples revealed that the oxide layer had been substan-tially completely removed from the samples whlch dis-played acceptable solderability ~Lot 1, treated with (1) or (3)] and ~Lot 2, treated with (1)]. The samples which were not solderaole ~Lot 1, tre~ted wi~h (2)] and ~Lot 2, treated with (2~ and ~3)] were determined to have retained about 20 to 30% of the initial oxide layer.
Thus, the only duplex treatment which was completely success~ul in the above example was the one utllizing for the second treatment the immersion in aqueous ferric sul~ate solution with no added acid.
The above test for solderability correspcnds to that described in Report W 72 - 51.2, American Societ~ for Metals, Metals Par~, Ohio. The sample is immersed in a rosin ~lux solution, then Yertically dipped into a oO Sn:
40 Pb molten solder at 230C, held in the bath ~or five seconds, ~,~ith~rawn, and examined a~ter cooling. The coating is rated according to appearance, rang~ng ~rom "ldeal't ~or a ~orlgh~, smooth deposit of uni~orm thickness to that in which there has been no solder adherence to the metal surf~ce.
The capacitance test referred to above has been described by J. J. McMullen and M. J. Pryor in "First International Congress in Metallic Corrosion", pages 53-54, 1961 (Butter~orth's, London), as amplified by Beck, Heine, Keir, van Rooyen, and Pryor in 'iInternational Journal of Corrosion Science", Vol. 2, pages 136 and 144-145~ 1962.
The mechanism of the duplex cleaning treatment of this invention is believed to differ in a significant way from the mechanism of the duplex cleaning treatment of U.S. Patent 3,646,946. The first treatment in the a~ueous alkaline solution is believed to hydrolyze the refractory oxides to convert them to a gelatinous condition. In ~he patented process the immersion in the mineral acid solution serves to dissolve the copper oxides and to help break up the refractory oxides without significant metal removal. ~n the process of the present invention the immersion in the ferric sulfate solution provides a cleaning action through removal of underlying metal beneath the oxide which undermines the oxide layer. The gelatinous condition of the oxide layer from the alkaline treatment allows the ferric sulfate solution to penetrate to the metal surface to provide the metal removal.
It has been observed for certain silicon containing copper alloys that an oxide penetration of from about 6 to 10 microns occurs at the grain boundaries. The prior art duplex treatment is not effective to remove the oxides at the grain boundaries because of insufficient removal of the ad~acent metal. The process of this invention is highly ~015 f'B.j ~
,~ , effective ~or removing such grain boundary oxides because it attacks the metal surface. The process of this invention is designed to remove oxides which are insoluble or resistant to normal pickling agents including ferric sulfate.
The effect of added mineral acid on the potency of the ferric sulfate cleaning bath as demonstrated in Table I has also been verified as applied to samples with an oxide coating. Therefore~ it is an important aspect of this invention that the ferric sulfate bath have no added mineral acid to thereby provide improved cleaning efficiency.
This invention may be embodied in other forms or carried out in varied ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as illustrative, the scope ` of the invention being indicated by the appended claims, and all changes and variations which come within the meaning and range of equivalency are intended to be embraced therein.
3o
5 N~2S4 36.4 48.3 These results sho~ed quite unexpectedly that the aqueous ~erric sulfate solution with no added acid, at both temperatures, dissolves the metal at a higher rate than any of the solutions containing added acid, and further~ that the dissolving rate at both temperatures decreases as the concentration of added acid is increased.
It was subsequently shown in duplex cleaning treat-ments of annealed metal having a surface oxide film up to 160 A thick, wherein the treatment consisted o~ a Lirst immersion in a hot alkaline solution7 followed by a second lmmersion in a hot ferric sulfate solution containing no added acid, that the removal o~ oxide film was accomplished effectively, as substantiated by the applicable tests, including the solderability test. The cleaning action is as thorough and complete, or better, than when added sul-furic acid is present in the ferric sul~ate solution, thereby accomplishing at least equivalent resul~s more ~ convenlentl~y and at decreased expense.
: The initial treatment with hot alkaline solution is carried out at a temperature o~ about 40C to the boiling ~ 9015 point and preferablyg at a temperature of about 70C to the ~oiling point, the solution having a pH abo~Je 10, preferably 11 to 14. The solutlon is preferably of caustic soda, but other alkali hydroxldes as of potassium or lithium, or mixtures may be used within the above-stated pH range. Immersion of the copper alloy should be for at least two seconds and prefera~ly, for five to six~y seconds. The treatment time may be prolonged, particularly at temperatures near the lower lim~t of the abo~e range, but generally should ~e for ten minutes or less, as longer times usually provide no added advantages. Optimum treating times and conditions may be determined in ac-cordance with the particular alloy and the results desired.
The second step of the duplex treatment is best ef-fected by immersion of the copper alloy strip or article, after the alkaline solution has been drained therefrom and rinsed with water9 in a hot 0.5 to 3 N., best 1.25 to 2 N., solution of ferric sulfate, without added acld at a tem-perature of about 25 to 95C,~est 65 to 90C, for at least two seconds, and preferably for five to sixty seconds, and generally for not over ten minutes.
Ferric sulfate for such treatment may be replaced in whole or in part by other soluble ferric salts, as for example b~y ferric ammonium sulfate or ferric nitrate, generally with the obtainment of equivalent results in t~e obtainment of clean and solderable copper alloy sur-faces. It may oe noted that aqueous solutions of ferric sulfate, typical of soluble ferric salts of strong acids, display a pH of about 1 at 0.5 N. solution, decreasing~
close to linearly, to about 0.5 at 2 N. and to about 0.35 at 3 N.
The efficacy of a duplex treatment in accordance with t~is invention, as above outlined, i5 illustrated in the following spec fic example, contrasting its successful results wit~ the ineffective cleaning provided by the process taught in U.S. Patent 3,646,946, the closest prior art duplex treatment.
EXAMPLE I
Sheets of C.D. Alloy 688 Ccontaining 22.7% Zn, 3.4%
Al, 0.4% Co, and balance essentially Cu) were bell an-nealed at about 600C in a closed furnace containing an ~; atmosphere produced by the partial combustion of hydro-carbons to produce two lots of annealed sheet, the first having a surface oxide layer ranging 95 to 105 A in thickness and the second having a sur~ace oxide la~er ranging 140 to 160 A ~n thickness.
Samples of the two lots were given a first i.~mersion ~reatment in boiling caustlc soda solution having a pE OL
14 for twenty seconds, drained, and washed with water.
Samples of the two lots, treated as above, were then sub~ected to immersion for twenty seconds in one o~ the following three solutions:
(l) 1.5 N. aqueous ferric sulfate solution, con-taining no added acid, at 65~C.
(2) 12% b~ vol. aqueous sulfuric acid solution at 65C.
(3) 12% b~y vol. aqueous sulfuric acid solution con-taining 4 oz. per gallon o~ sodium dichromate.
~ollowing the twentJ second immersion, the samples were drained, washed with water, and dried.
7~3~ ~ 9015-~3 Solderability tests applied to the treated samples of the first lot (95 to 105 ~ oxide layer~ revealed that those treated ~ith solution Cl~ and (3) were solderable, while those treated ~ith solution (2) could not be soldered ef~ectively .
Solderability tests applied to the treated samples o~ the second lot C140 to 160 A oxide layer) revealed that those ~reated with solution Cl ) ~ere solderaole, while those treated with solutions (2) and (3) could not be ef~ectively soldered.
Furthermore, capacitance tests on the above-treated samples revealed that the oxide layer had been substan-tially completely removed from the samples whlch dis-played acceptable solderability ~Lot 1, treated with (1) or (3)] and ~Lot 2, treated with (1)]. The samples which were not solderaole ~Lot 1, tre~ted wi~h (2)] and ~Lot 2, treated with (2~ and ~3)] were determined to have retained about 20 to 30% of the initial oxide layer.
Thus, the only duplex treatment which was completely success~ul in the above example was the one utllizing for the second treatment the immersion in aqueous ferric sul~ate solution with no added acid.
The above test for solderability correspcnds to that described in Report W 72 - 51.2, American Societ~ for Metals, Metals Par~, Ohio. The sample is immersed in a rosin ~lux solution, then Yertically dipped into a oO Sn:
40 Pb molten solder at 230C, held in the bath ~or five seconds, ~,~ith~rawn, and examined a~ter cooling. The coating is rated according to appearance, rang~ng ~rom "ldeal't ~or a ~orlgh~, smooth deposit of uni~orm thickness to that in which there has been no solder adherence to the metal surf~ce.
The capacitance test referred to above has been described by J. J. McMullen and M. J. Pryor in "First International Congress in Metallic Corrosion", pages 53-54, 1961 (Butter~orth's, London), as amplified by Beck, Heine, Keir, van Rooyen, and Pryor in 'iInternational Journal of Corrosion Science", Vol. 2, pages 136 and 144-145~ 1962.
The mechanism of the duplex cleaning treatment of this invention is believed to differ in a significant way from the mechanism of the duplex cleaning treatment of U.S. Patent 3,646,946. The first treatment in the a~ueous alkaline solution is believed to hydrolyze the refractory oxides to convert them to a gelatinous condition. In ~he patented process the immersion in the mineral acid solution serves to dissolve the copper oxides and to help break up the refractory oxides without significant metal removal. ~n the process of the present invention the immersion in the ferric sulfate solution provides a cleaning action through removal of underlying metal beneath the oxide which undermines the oxide layer. The gelatinous condition of the oxide layer from the alkaline treatment allows the ferric sulfate solution to penetrate to the metal surface to provide the metal removal.
It has been observed for certain silicon containing copper alloys that an oxide penetration of from about 6 to 10 microns occurs at the grain boundaries. The prior art duplex treatment is not effective to remove the oxides at the grain boundaries because of insufficient removal of the ad~acent metal. The process of this invention is highly ~015 f'B.j ~
,~ , effective ~or removing such grain boundary oxides because it attacks the metal surface. The process of this invention is designed to remove oxides which are insoluble or resistant to normal pickling agents including ferric sulfate.
The effect of added mineral acid on the potency of the ferric sulfate cleaning bath as demonstrated in Table I has also been verified as applied to samples with an oxide coating. Therefore~ it is an important aspect of this invention that the ferric sulfate bath have no added mineral acid to thereby provide improved cleaning efficiency.
This invention may be embodied in other forms or carried out in varied ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as illustrative, the scope ` of the invention being indicated by the appended claims, and all changes and variations which come within the meaning and range of equivalency are intended to be embraced therein.
3o
Claims (9)
1. A process for cleaning the surface of a copper base alloy having a surface layer of thermally formed complex metal oxide of a refractory nature, comprising immersing the said surface in an aqueous alkaline solution having a pH of 11 to 14 and heated to a temperature of about 40°C to its boiling point for a period of two seconds to not more than ten minutes, and then immersing the said surface in 0.5 to 3 N. aqueous solution of ferric sulfate containing no added mineral acid at a temperature of 25° to 95°C for a period of two seconds to not more than ten minutes,
2. A process according to claim 1 wherein the said alloy contains Al and at least one metal selected from the group consisting of Zn, Fe, Co and Si.
3. A process according to claim 1 wherein the said thermal oxide layer has a thickness of 140 to 160 .ANG..
4. A process according to claim 1 wherein the said alkaline solution is at 70°C to its boiling point.
5. A process according to claim 1 wherein the said ferric sulfate solution is at 60° to 90°C.
6. A process according to claim 1 wherein the said surface is immersed in said alkaline solution for a period of five to sixty seconds.
7. A process according to claim 1 wherein the said surface is immersed in the said ferric sulfate solution for a period of five to sixty seconds.
8. A process according to claim 1 wherein the said surface is immersed in a 1.25 to 2 N. ferric sulfate solution.
9. A process according to claim 1 wherein the said ferric sulfate solution has a pH of 0.35 to 1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94189078A | 1978-09-13 | 1978-09-13 | |
| US941,890 | 1978-09-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117853A true CA1117853A (en) | 1982-02-09 |
Family
ID=25477230
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000334174A Expired CA1117853A (en) | 1978-09-13 | 1979-08-21 | Copper alloy cleaning process |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5538994A (en) |
| AU (1) | AU524836B2 (en) |
| CA (1) | CA1117853A (en) |
| DE (1) | DE2935138A1 (en) |
| FR (1) | FR2436193A1 (en) |
| GB (1) | GB2031468B (en) |
| HK (1) | HK53383A (en) |
| IT (1) | IT1162479B (en) |
| MY (1) | MY8400310A (en) |
| SE (1) | SE7907027L (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4588634A (en) * | 1983-08-05 | 1986-05-13 | The Flintkote Company | Coating formulation for inorganic fiber mat based bituminous roofing shingles |
| US4600443A (en) * | 1984-10-01 | 1986-07-15 | Kennecott Corporation | Process for removing surface oxides from a copper-base alloy |
| GB2220005A (en) * | 1988-06-28 | 1989-12-28 | Borsodi Vegyi Komb | Process for removing oxide layer and scale from metals and metal alloys |
| JPH05279573A (en) * | 1992-04-02 | 1993-10-26 | Itsuo Ichikawa | Production of road paving material |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2318559A (en) * | 1941-04-30 | 1943-05-04 | Monsanto Chemicals | Material for and process of pickling copper or its alloys |
| US3646946A (en) * | 1969-01-06 | 1972-03-07 | Olin Mathieson | Copper alloy cleaning process |
| IL33877A0 (en) * | 1969-03-28 | 1970-04-20 | Miles Lab | Metal cleaning compositions and process for their use |
-
1979
- 1979-08-21 CA CA000334174A patent/CA1117853A/en not_active Expired
- 1979-08-22 AU AU50176/79A patent/AU524836B2/en not_active Ceased
- 1979-08-22 SE SE7907027A patent/SE7907027L/en not_active Application Discontinuation
- 1979-08-23 GB GB7929337A patent/GB2031468B/en not_active Expired
- 1979-08-30 DE DE19792935138 patent/DE2935138A1/en not_active Withdrawn
- 1979-08-31 FR FR7921946A patent/FR2436193A1/en active Granted
- 1979-09-04 JP JP11247279A patent/JPS5538994A/en active Pending
- 1979-09-05 IT IT50176/79A patent/IT1162479B/en active
-
1983
- 1983-11-10 HK HK533/83A patent/HK53383A/en unknown
-
1984
- 1984-12-30 MY MY310/84A patent/MY8400310A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5538994A (en) | 1980-03-18 |
| FR2436193A1 (en) | 1980-04-11 |
| DE2935138A1 (en) | 1980-03-27 |
| MY8400310A (en) | 1984-12-31 |
| FR2436193B1 (en) | 1983-11-04 |
| HK53383A (en) | 1983-11-18 |
| SE7907027L (en) | 1980-03-14 |
| GB2031468B (en) | 1982-09-08 |
| AU5017679A (en) | 1980-03-20 |
| AU524836B2 (en) | 1982-10-07 |
| IT1162479B (en) | 1987-04-01 |
| IT7950176A0 (en) | 1979-09-05 |
| GB2031468A (en) | 1980-04-23 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |