Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/9335—Product by special process
  • Y10S428/934—Electrical process
  • Y10S428/935—Electroplating
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12896—Ag-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12903—Cu-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12986—Adjacent functionally defined components

Definitions

• This invention relates generally to electroplating a solderable surface on an article. More specifically, the invention involves a multiple step process for providing a tenaciously adhering electroplating base on an alloy article.
• the invention may be considered as two processes. A first general process which will produce solderable coatings on alloy articles but with less than 100% yield of articles and a second more limited process that enables one to have substantially 100% yield of articles even under extreme environmental conditions.
• the process may not require a substantially 100% yield and in those cases the general process without refinements need not be followed.
• the plated articles will not be required to withstand extreme operating and test conditions. For example, two of the conditions are that lead coating frames must withstand a baking cycle of about 900 F. and still be solderable.
• lead coating frames must withstand a baking cycle of about 900 F. and still be solderable.
• One of the problems is that subjecting an article to a high temperature baking cycle causes the coating to blister or peel off which renders the article useless.
• nickel-iron, ferrous and copper alloys and Kovar (trademark for nickel cobalt iron alloys) alloys are preferred in lead frames for electrical circuits.
• Kovar trademark for nickel cobalt iron alloys
• the present invention is a process of coating an article with a number of different layers of material after thoroughly cleaning the surface of the article.
• the present invention is the discovery that a process of applying a tenaciously adhering solderable coating to a nickel-iron alloy requires a thorough cleaning of the article followed by forming base layers to receive a final layer of solderable material. More specifically, the process involves cleaning the article to remove organic and inorganic material, applying a copper strike, applying a silver strike which is followed by electroplating a solderable coating such as copper silver on top of the silver strike.
• the article was anodically cleaned with about 6 volts in an alkaline solution having a concentration of about 2.2 lbs. of an alkaline cleaner per gallon of water for at about 3 minutes at a temperature of about 150 LII F.
• the alkaline material can be any suitable alkaline cleaner such as potassium hydroxide or sodium hydroxide.
• the purpose of the first step is to remove any organic material on the article.
• the article is spray rinsed or washed to remove any alkaline solution on the article.
• the article is pickled in a solution of about 20% hydrochloric acid for about 30 seconds at about F.
• the purpose of this step is to remove any oxides and neutralize any alkaline solution on the article.
• the article is spray rinsed to remove any residue materials on the article.
• the article now in a cleaned condition is placed in a solution containing about 2.2 pounds of potassium cyanide per gallon of water for about 3 minutes and subjected to anodic cleaning at 6 volts.
• This step leaves the article with an active metal surface.
• any suitable cleaning solution is acceptable, for example, chelating agents or sodium gluconate could also be used in this cleaning process.
• the process of anodic cleaning is well known in the art and no further discussion is necessary but those wishing to obtain greater detail on anodic cleaning may refer to the l97l Metal Finishing Guidebook and Directory.
• the article is removed and spray rinsed to remove any residue material from the previous step.
• a typical suitable copper strike solution contains about 2.5 ounces of copper cyanide per gallon of water and about 6 ounces of potassium cyanide per gallon of water.
• the alloy article is immersed for about 1 minute at about 120 F. and given a copper strike at about 1.5 volts.
• the copper strike solution is monitored to determine the ratio of the free potassium cyanide to the copper. Results have indicated that the yield is higher if the ratio is about 1 to 1, however, the process still produces acceptable plated articles if the ratio is not maintained at the l to 1 ratio.
• a dummy article is also plated at about 1.5 volts.
• the dummy article is an article which is similar to the article being plated but is only used as a copper plating sink. It is not understood why the dummy article is required but it has been observed that the use of the dummy article insures that the yield of properly plated articles is close to 100% whereas without the dummy article the yield of usable articles will greatly fluctuate from run to run.
• Another feature which has been found useful is to place a woven bag around the anode during the plating cycle. The bag acts as a filter to keep crud and other material from forming and collecting at the anode.
• the article with the copper strike is then removed and spray rinsed to remove any residue material on the article.
• a typical suitable silver plating solution contains about 0.3 ounces of silver cyanide per gallon of water, about 0.3 to about 0.37 ounces of copper per gallon of water and about 12 ounces of potassium cyanide per gallon of water.
• the alloy article is plated for about 1 minute at about 75 F. and at about 1.5 volts. It is important to the process to prevent the silver from immersion coating the article. The immersion coated silver is undesirable because it does not adhere well to the copper strike. In order to avoid this problem, it was discovered that the silver ion concentration in the solution should be kept low and the electroplating voltage should be applied to the article before immersing the article in the electroplating solution. While there is no absolute limit as to ion concentration.
• the article is removed and a solderable coating in this case, silver, was electroplated on the article in a solution containing about 6 ounces of silver cyanide per gallon of water, about 0.1 ounces to about 0.4 ounces of copper cyanide per gallon of water and about ounces of potassium cyanide per gallon. of water.
• the heart of the present invention is the process of applying a silver strike by limitation of the concentration of the silver ions in the silver strike solutions, as well as applying the electroplating voltage to the article before inserting the article into the silver strike solution.
• concentration of the ions is that if the concentration of ions is too high and if no voltage is applied to the article before insertion of the article into the silver strike solution, the article will immersion plate with silver.
• the immersion plated silver has been found to be undesirable because it does not adhere well and tends to flake off of the article thereby rendering the article inoperative.
• the process of the present invention may be more aptly described as a process of applying a solderable coating to alloy by first cleaning the article to remove organic and inorganic materials and then applying a copper strike to the article followed by removing the article with the copper strike thereon and maintaining the article in a wetted condition followed by electroplating a silver strike to the article insuring that the electroplating voltage is applied to the article before inserting the article in the silver strike solution.
• the article can then receive a solderable coating electroplating base material on the silver strike.
• the concentration of the silver strike solution is not in excess of about one ounce of silver cyanide per gallon of water if the temperature is about F. and the voltage is about 1.5 volts with a time of about one minute.
• the voltage, temperature and time of plating are all related and that changes in these parameters can still produce acceptable plated articles.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating Methods And Accessories (AREA)
• Lead Frames For Integrated Circuits (AREA)

Priority Applications (9)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23738572

Family Applications (1)

Country Status (9)

Cited By (2)

Families Citing this family (2)

Citations (8)

• 1974
  • 1974-01-30 US US437944A patent/US3878065A/en not_active Expired - Lifetime
  • 1974-08-21 CA CA207,516A patent/CA1034899A/en not_active Expired
  • 1974-08-23 GB GB3711174A patent/GB1456769A/en not_active Expired
  • 1974-08-30 NL NL7411586A patent/NL7411586A/xx not_active Application Discontinuation
  • 1974-09-09 BE BE148312A patent/BE819667A/nl unknown
  • 1974-10-07 FR FR7433721A patent/FR2259165B3/fr not_active Expired
  • 1974-10-08 JP JP49116021A patent/JPS585275B2/ja not_active Expired
  • 1974-11-19 IT IT29605/74A patent/IT1025833B/it active
  • 1974-12-04 DE DE19742457201 patent/DE2457201A1/de not_active Withdrawn

Patent Citations (8)

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