EP0698677A2 - Méthode pour le dorage de produits semi-finis en bandes, en particulier pour cadres de connexion - Google Patents

Méthode pour le dorage de produits semi-finis en bandes, en particulier pour cadres de connexion Download PDF

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Publication number
EP0698677A2
EP0698677A2 EP95111826A EP95111826A EP0698677A2 EP 0698677 A2 EP0698677 A2 EP 0698677A2 EP 95111826 A EP95111826 A EP 95111826A EP 95111826 A EP95111826 A EP 95111826A EP 0698677 A2 EP0698677 A2 EP 0698677A2
Authority
EP
European Patent Office
Prior art keywords
current density
gold
layer
partial layer
thickness
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95111826A
Other languages
German (de)
English (en)
Other versions
EP0698677A3 (fr
EP0698677B1 (fr
Inventor
Franz Dr. Kaspar
Norbert Dr. Normann
Gerd Schaudt
Thilo Uhrig
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Doduco Contacts and Refining GmbH
Original Assignee
Doduco GmbH and Co
Doduco GmbH and Co KG Dr Eugen Duerrwaechter
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE4436071A external-priority patent/DE4436071C2/de
Application filed by Doduco GmbH and Co, Doduco GmbH and Co KG Dr Eugen Duerrwaechter filed Critical Doduco GmbH and Co
Publication of EP0698677A2 publication Critical patent/EP0698677A2/fr
Publication of EP0698677A3 publication Critical patent/EP0698677A3/fr
Application granted granted Critical
Publication of EP0698677B1 publication Critical patent/EP0698677B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/623—Porosity of the layers
    • 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
    • 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
    • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers

Definitions

  • the invention relates to a method for the continuous, selective, galvanic gilding of band-shaped semi-finished products, in particular for lead frames for semiconductor technology.
  • bond flags the surface of which is designed to be bondable, for example by galvanic gold plating is.
  • Bonding is a friction welding process, with which thin wires are connected to the bonding lugs.
  • the requirements for galvanic gold plating are, for example, in the MIL Specif. G-45204B.
  • the gold layer that is bonded to is usually deposited from high-purity fine gold baths on a nickel underlayer.
  • the present invention is based on the object of demonstrating a way in which reliable high-quality bondable surfaces can be obtained under series production conditions, namely with strip electroplating running at high speed, which enable more reliable bond connections.
  • the semi-finished product is in a first step with a gold bath at a higher current density and then in a further step with a gold bath treated at a lower current density. It has been shown that gold surfaces are obtained in this way which are outstandingly suitable for wire bonding and which lead to failures in the bond connections much less frequently. It is a further great advantage of the method according to the invention that the surface properties of the gold layer can be set independently of their volume properties. However, this in no way means that the only thing that matters for the bondability is the surface properties. The surface properties and the volume properties of the gold layer rather both influence the bondability in combination.
  • the layer growth is slow. This is undesirable for efficient series production.
  • the prior art therefore works with the highest possible separation speed and therefore with the highest possible current density (high speed conditions).
  • the use of a deposition step at a low current density does not result in the process becoming uneconomical, because the majority of the layer structure still takes place at a high current density and therefore at a correspondingly high deposition speed.
  • Preferably about 75 to 90% of the thickness of the gold layer is produced at a higher current density, only the rest at a lower current density; in terms of numbers a layer structure is preferred in which 0.6 to 1.2 ⁇ m gold are deposited at a high current density and 0.15 to 0.4 ⁇ m gold at a low current density.
  • a layer structure in which 0.8 ⁇ m is deposited at a high current density and 0.2 ⁇ m at a low current density has proven particularly useful.
  • the thicker partial layer deposited first influences the bondability primarily through its hardness, thickness and purity, while the surface layer deposited next determines the bondability primarily through its surface structure, roughness, the coefficient of friction with the bonding wire and also through it Purity. Volume properties and surface properties can be set independently of one another, thereby optimizing the bondability.
  • a gold layer deposited with a high current density is not only economical to deposit, but also has a low hardness which is favorable for bonding. It is disadvantageous, however, that more undesirable foreign substances are also deposited and embedded in the gold layer at high speed and that the layer is more porous than a gold layer deposited slowly with a low current density.
  • the surface layer deposited at low speed is denser, has fewer defects and is characterized by fewer foreign inclusions, which is favorable for bonding, and shows a different friction behavior which is more favorable for bonding.
  • the current density with which the lower sub-layer is deposited is preferably a factor of 10 to 30 above the current density with which the thinner surface layer is deposited.
  • the deposition can be carried out in such a way that the strip-shaped semifinished product passes through the same bath twice, the bath being operated with a high current density the first time and with a low current density the second time.
  • Suitable devices for coating are, for example, the device disclosed in DE-A-40 19 643 for depositing gold strips on strips of metal, the position and width of the gold strips being determined by mask strips, or a device for spot gilding in which one to be coated Band lies with this mask band running along, which has individual windows which determine the position and size of the spots to be separated.
  • the coating apparatus shown in EP 370 239 which has an elongated nozzle head, over which a felt is stretched, which is impregnated with the gold bath liquid, and over which the band-shaped semi-finished product is pulled away for selective gilding.
  • the accompanying drawing shows schematically the typical structure of a bond flag, consisting of a carrier 1 made of a copper-based alloy, which is first nickel-plated in a conventional manner with a layer thickness of 2 to 3 ⁇ m; the nickel layer is designated by the reference number 2 and serves as a diffusion barrier between the copper alloy and the gold layer, which is applied in two steps according to the invention: in a first step, at a current density of 3 to 100 A / dm 2, preferably at a current density of 5 to 7 A / dm2, a 0.8 .mu.m thick gold layer 3, onto which a 0 in a second step at a lower current density, for example at 0.3 to 1 A / dm2, preferably at a current density of 0.6 A / dm2 , 2 ⁇ m thick surface layer 4 of gold is deposited.
  • the separation takes place from a Fine gold bath of conventional composition, for example from a bath based on potassium gold cyanide or from a cyanide-free bath based

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)
  • Battery Electrode And Active Subsutance (AREA)
EP95111826A 1994-07-28 1995-07-28 Méthode pour le dorage de produits semi-finis en bandes, en particulier pour cadres de connexion Expired - Lifetime EP0698677B1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE4426862 1994-07-28
DE4426862 1994-07-28
DE4436071A DE4436071C2 (de) 1994-07-28 1994-10-10 Verfahren zum Vergolden von bandförmigem Halbzeug, insbesondere für Leadframes und nach dem Verfahren vergoldete Leadframes
DE4436071 1994-10-10

Publications (3)

Publication Number Publication Date
EP0698677A2 true EP0698677A2 (fr) 1996-02-28
EP0698677A3 EP0698677A3 (fr) 1998-08-26
EP0698677B1 EP0698677B1 (fr) 2002-10-09

Family

ID=25938782

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95111826A Expired - Lifetime EP0698677B1 (fr) 1994-07-28 1995-07-28 Méthode pour le dorage de produits semi-finis en bandes, en particulier pour cadres de connexion

Country Status (2)

Country Link
EP (1) EP0698677B1 (fr)
ES (1) ES2184776T3 (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2147311B (en) * 1983-09-29 1987-10-21 Hara J B O Electrodepositing precious metal alloys
DE3683595D1 (de) * 1985-11-11 1992-03-05 Electroplating Eng Vorrichtung zum selektiven metallbeschichten von steckverbinderkontaktstiften.
DE3839223C2 (de) * 1988-11-19 1994-10-20 Degussa Vorrichtung zur selektiven galvanischen Beschichtung

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None

Also Published As

Publication number Publication date
EP0698677A3 (fr) 1998-08-26
EP0698677B1 (fr) 2002-10-09
ES2184776T3 (es) 2003-04-16

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