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
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/10—Electrodes, e.g. composition, counter electrode
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/64—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of silver
• • 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
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
• • 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
  • C25D5/48—After-treatment of electroplated surfaces
  • C25D5/50—After-treatment of electroplated surfaces by heat-treatment
  • C25D5/505—After-treatment of electroplated surfaces by heat-treatment of electroplated tin coatings, e.g. by melting
• • 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
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/615—Microstructure of the layers, e.g. mixed structure
  • C25D5/617—Crystalline layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D7/00—Electroplating characterised by the article coated
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
  • H01R12/00—Structural associations of a plurality of mutually-insulated electrical connecting elements, specially adapted for printed circuits, e.g. printed circuit boards [PCB], flat or ribbon cables, or like generally planar structures, e.g. terminal strips, terminal blocks; Coupling devices specially adapted for printed circuits, flat or ribbon cables, or like generally planar structures; Terminals specially adapted for contact with, or insertion into, printed circuits, flat or ribbon cables, or like generally planar structures
  • H01R12/50—Fixed connections
  • H01R12/51—Fixed connections for rigid printed circuits or like structures
  • H01R12/55—Fixed connections for rigid printed circuits or like structures characterised by the terminals
  • H01R12/58—Fixed connections for rigid printed circuits or like structures characterised by the terminals terminals for insertion into holes
  • H01R12/585—Terminals having a press fit or a compliant portion and a shank passing through a hole in the printed circuit board

Definitions

• the invention relates to a method for coating a press-fit pin and a press-in pin.
• the EP 2 596 157 B1 discloses a method of making a press-fit pin.
• a layer is deposited on a base body galvanically from methanesulfonsaurer solution, which is formed from a tin alloy.
• the US 2009/0239398 A1 discloses a press-in pin which is coated with a layer made of a tin alloy.
• the tin alloy contains 0.5 to 15 wt.% Silver.
• the US Pat. No. 6,361,823 B1 discloses an electroless method for coating a base made of copper or a copper alloy.
• the base body is first coated with a layer made of tin and then coated with an outer layer made of an alloy.
• the DE 10 2005 055 742 A1 discloses a method of making a contactable layer on a metal element.
• the contact-adapted layer is formed essentially of tin. It may have intermetallic silver / tin phases with a silver content in the range of 25 to 40 wt.%.
• whiskers growing out of the layer sometimes occurs. Such whiskers can lead to the formation of short circuits.
• the object of the invention is to eliminate the disadvantages of the prior art.
• a method for producing a press-fit pin and a press-in pin are to be specified in which the tendency to form whiskers is reduced.
• a method for coating a Einpresspins wherein a base made of copper or a copper alloy is galvanically coated from an alkaline-cyanide electrolyte at least partially with a layer of a silver alloy, the more than 50 wt.% Ag, a Contains residual Sn and unavoidable impurities.
• the layer is not deposited galvanically from an acidic electrolyte, but from an alkaline-cyanide electrolyte on the base body.
• the silver alloy forming the layer contains more than 50% by weight of Ag, preferably at least 55% by weight of Ag. It has surprisingly been found that with the method according to the invention, a largely pore-free connection of the layer to the base body can be achieved. In particular, it is possible with the proposed method to produce homogeneous single-phase layers.
• a press-in pin produced by the method according to the invention is characterized by a particularly low tendency to form whiskers.
• silver cyanide silver cyanide
• potassium silver cyanide silver sulfide
• silver sulfate silver sulfate
• tin compounds the following compounds can be used to prepare the electrolyte: potassium stannate, sodium stannate, tin oxide, tin sulfate.
• At least one of the following compounds is advantageously added to the electrolyte: sodium cyanide, potassium cyanide, sodium gluconate, potassium gluconate, ethylenediamine, ammonia, triethanolamine, glycine, thiourea, urea, nitrilotriacetic acid.
• the abovementioned compounds serve as complexing agents or as conducting salts.
• At least one of the following further compounds may be added to the electrolyte: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium sulphide.
• the abovementioned further compounds act as complexing agents with respect to tin. Apart from that, the conductivity of the electrolyte can be adjusted with the other compounds.
• the galvanic coating is advantageously carried out at a current density in the range of 5 to 20 A / dm 2 .
• the pH of the electrolyte is suitably adjusted to 7 to 14, preferably to more than 8.
• a temperature of the electrolyte may be adjusted to a value in the range of 40 to 90 ° C, preferably 50 to 70 ° C in the coating. More preferably, the temperature is 55 to 60 ° C.
• an anode made of any one of the following materials can be used: graphite, platinum-plated titanium or niobium, silver, tin, silver or tin alloy.
• An anode made of titanium or niobium may also be coated with a layer of a mixed oxide based on Ir, Ta, Nb instead of the platinum. It is also possible to use an anode made of silver and a further anode made of tin, which are operated in two separate circuits. Further, anodes can be used in an anolyte with a diaphragm.
• the layer in a thickness of 0.1 to 0.8 microns, preferably 0.2 to 0.6 microns applied.
• an intermediate layer of Ni or Cu can be galvanically applied to the base body.
• the adhesion of the layer can be improved.
• the applied to the body layer for a period of 1 to 10 seconds to a temperature in the range of 200 to 500 ° C, preferably 300 to 400 ° C, heated.
• the heating causes a crystal growth in the layer.
• it can be reduced in the alloy, the concentration of Sn.
• intermetallic phases can form Ag 3 Sn or Ag 4 Sn. Such intermetallic phases are particularly effective against the formation of whiskers.
• the heat treatment may cause the formation of further intermetallic phases between the base body and the layer.
• Such further intermetallic phases consist for example of Cu 6 Sn 5 or of Cu 3 Sn.
• the heat treatment may cause the formation of a further intermetallic phase between the Ni intermediate layer and the layer made of the silver alloy.
• Such a further intermetallic phase is formed, for example, from Ni 3 Sn 4 .
• a press-in is proposed, with a base body made of copper or a copper alloy and the base body at least partially covering layer, wherein the layer is formed of a silver alloy containing at least 50 wt.% Ag, a balance of Sn and contains unavoidable impurities.
• the proposed press-in pin can be produced by the process according to the invention. It advantageously contains no lead. With the proposed layer, formation of whiskers can be effectively counteracted.
• the silver alloy contains more than 63 wt.% And less than 90 wt.% Ag.
• the silver alloy contains 73% by weight to 89% by weight of Ag.
• the silver alloy contains 75 wt.% To 85 wt.% Ag.
• the silver alloy is in particular formed from Ag 3 Sn and / or from Ag 4 Sn. It is in particular formed from an intermetallic phase of Ag 3 Sn or Ag 4 Sn. Such an intermetallic phase causes the formation of whiskers safely and reliably.
• the silver alloy is greater than 95%, preferably greater than 99%, of a single such intermetallic phase.
• the silver alloy may also be formed from an Ag or Sn matrix containing at least one intermetallic phase of Ag 3 Sn and / or Ag 4 Sn.
• a thickness of the layer is suitably 0.1 to 0.8 ⁇ m, preferably 0.2 to 0.6 ⁇ m.
• the thickness of the layer is particularly preferably 0.3 to 0.4 ⁇ m.
• an intermediate layer formed of Ni or Cu is provided between the base body and the layer.
• the intermediate layer may have a further thickness of 1.0 to 3.0 ⁇ m, preferably 1.1 to 2.5 ⁇ m.
• An average crystal size of the crystals forming the layer is advantageously 50 to 800 nm, preferably 100 to 600 nm, particularly preferably 150 to 400 nm.
• an electrolyte is used, the composition of which is shown in the table below.
• the pH of the electrolyte is adjusted to a value in the range of 8 to 13 by the addition of sodium hydroxide, potassium hydroxide or the like.
• the electrolytic deposition of the layer takes place at a temperature in the range of 50 to 70 ° C. and a current density of 5 to 20 A / dm 2 .
• the concentrations of the silver and tin-providing compounds are adjusted so that a single-phase intermetallic compound of Ag 3 Sn or Ag 4 Sn is formed.
• the layer deposited on the base made of copper or a copper alloy may subsequently be heated to a temperature in the range of 300 to 400 ° C for a period of 1 to 10 seconds.
• the press-in pin produced according to the invention is free of lead.
• the layer of silver alloy deposited thereon is hard, tough, and has a particularly low tendency to form whiskers.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Electroplating Methods And Accessories (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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Publications (2)

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Citations (4)

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• 2015
  • 2015-03-14 DE DE102015003285.2A patent/DE102015003285A1/de not_active Withdrawn
• 2016
  • 2016-03-03 EP EP16000515.3A patent/EP3070188A3/fr not_active Withdrawn
  • 2016-03-14 US US15/068,875 patent/US20160268709A1/en not_active Abandoned
  • 2016-03-14 CN CN201610227976.1A patent/CN105970263A/zh active Pending

Patent Citations (4)

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