US3561084A - Method of terminating a lamp filament - Google Patents

Method of terminating a lamp filament Download PDF

Info

Publication number
US3561084A
US3561084A US765149A US3561084DA US3561084A US 3561084 A US3561084 A US 3561084A US 765149 A US765149 A US 765149A US 3561084D A US3561084D A US 3561084DA US 3561084 A US3561084 A US 3561084A
Authority
US
United States
Prior art keywords
filament
lead wire
metal
wire
gold
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.)
Expired - Lifetime
Application number
US765149A
Inventor
Richard E Sims
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.)
VCH INTERNATIONAL Ltd
Original Assignee
Chicago Miniature Lamp Inc
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
Application filed by Chicago Miniature Lamp Inc filed Critical Chicago Miniature Lamp Inc
Application granted granted Critical
Publication of US3561084A publication Critical patent/US3561084A/en
Assigned to GENERAL INSTRUMENT CORPORATION reassignment GENERAL INSTRUMENT CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: CHICAGO MINIATURE LAMP WORKS
Assigned to VCH International Limited reassignment VCH International Limited ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: GENERAL INSTRUMENT CORPORATION, 225 ALLWOOD RD., CLIFTON, NJ 07012, A CORP. OF DE
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L24/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/002—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating specially adapted for particular articles or work
    • B23K20/004—Wire welding
    • B23K20/005—Capillary welding
    • B23K20/007—Ball bonding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/001—Interlayers, transition pieces for metallurgical bonding of workpieces
    • B23K35/005—Interlayers, transition pieces for metallurgical bonding of workpieces at least one of the workpieces being of a refractory metal
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01K—ELECTRIC INCANDESCENT LAMPS
    • H01K1/00—Details
    • H01K1/02—Incandescent bodies
    • H01K1/16—Electric connection thereto
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01K—ELECTRIC INCANDESCENT LAMPS
    • H01K3/00—Apparatus or processes adapted to the manufacture, installing, removal, or maintenance of incandescent lamps or parts thereof
    • H01K3/06—Attaching of incandescent bodies to mount
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/42—Wire connectors; Manufacturing methods related thereto
    • H01L24/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L24/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/4501—Shape
    • H01L2224/45012—Cross-sectional shape
    • H01L2224/45015—Cross-sectional shape being circular
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/45099—Material
    • H01L2224/451—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45144—Gold (Au) as principal constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/484—Connecting portions
    • H01L2224/48463—Connecting portions the connecting portion on the bonding area of the semiconductor or solid-state body being a ball bond
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/485—Material
    • H01L2224/48505—Material at the bonding interface
    • H01L2224/48599—Principal constituent of the connecting portion of the wire connector being Gold (Au)
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/74—Apparatus for manufacturing arrangements for connecting or disconnecting semiconductor or solid-state bodies and for methods related thereto
    • H01L2224/78—Apparatus for connecting with wire connectors
    • H01L2224/7825—Means for applying energy, e.g. heating means
    • H01L2224/783—Means for applying energy, e.g. heating means by means of pressure
    • H01L2224/78301—Capillary
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L2224/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L2224/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
    • H01L2224/852—Applying energy for connecting
    • H01L2224/85201—Compression bonding
    • H01L2224/85203—Thermocompression bonding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/42—Wire connectors; Manufacturing methods related thereto
    • H01L24/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L24/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/00014—Technical content checked by a classifier the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01005—Boron [B]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01006—Carbon [C]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01013—Aluminum [Al]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01019—Potassium [K]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01028—Nickel [Ni]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01029—Copper [Cu]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01074—Tungsten [W]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01075—Rhenium [Re]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01077—Iridium [Ir]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01078—Platinum [Pt]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/01—Chemical elements
    • H01L2924/01079—Gold [Au]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/013—Alloys
    • H01L2924/0132—Binary Alloys
    • H01L2924/01327—Intermediate phases, i.e. intermetallics compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/20—Parameters
    • H01L2924/207—Diameter ranges
    • H01L2924/20755—Diameter ranges larger or equal to 50 microns less than 60 microns

Definitions

  • a lamp filament is reliably and firmly connected both electrically and mechanically to a lead wire or mounting
  • the present invention relates to the manufacture of incandescent lamps, and more particularly to a new and improved method for terminating a lamp filament.
  • a filament such as a fine tungsten wire is mounted between a pair of lead wires or posts which serve both to support the filament and to complete a path for energization of the filament. Consequently it is of paramount importance that the interconnection between the filament and the lead wires or posts be firm, reliable, and characterized by extremely low electrical resistance.
  • An important object of the present invention is to provide an improved method of connecting a lamp filament to a lead wire.
  • Another object is to provide a method capable of producing a firm, strong and reliable mechanical connection between the filament and the lead wire.
  • a further object is to provide a method for producing a connection between a filament and a lead wire characterized by low resistance.
  • Another object of the invention is to provide a method for terminating a lamp filament wherein the production of oxide is avoided.
  • Another object is to provide an improved method for terminating a lamp filament wherein the connection between the filament and the lead wire is small in size and low in profile, and to provide a method particularly suited to the manufacture of miniature lamps such as numeric readout lamps and the like.
  • a lamp filament is mounted to a lead wire by sandwiching the filament between the lead wire and a body of metal.
  • the metal is simultaneously heated to a semi-plastic state and pressed against the lead wire.
  • a metallurgical or intermetallic bond is created between the body of metal and the lead wire, and at the same time the filament is entrapped within the body of metal.
  • FIGS. 1-4 are somewhat diagrammatic and fragmentary illustrations of successive operations carried out in a process of terminating a lamp filament in accordance with the present invention.
  • FIG. 1 the filament 10 is placed on the lead wire 12 and the body 14 of metal is positioned to overlie the filament 10- and lead wire 12.
  • the metal body 14 is then moved toward the lead wire 12 to sandwich the filament 10 between the lead wire 12 and the body 14, as indicated in FIG. 2.
  • the body 14 is heated to a plastic or semi-plastic state, but not to a liquid state, while being pressed against the filament 10 and the lead wire 12.
  • the filament is intimately surrounded or entrapped in the metal of the body 14 while an intermetallic or metallurgical bond is formed by diffusion at the interface of the body 14 and the lead wire 12. Due to the extensive and firm mechanical contact between the filament 10 and the body 14, and the thermocompression diffusion bond between the body 14 and lead wire 12, a highly reliable and conductive connection is produced.
  • the method of the present invention is particularly suited to the manufacture of miniature lamps such as numeric readout lamps wherein several filaments such as the filament 10 illustrated in the drawing may be connected between several lead wires or posts 12 and sealed in a vacuum beneath a transparent face plate.
  • the filament 10 is a tungsten wire having a diameter in the neighborhood of 0.3 mil and wound in a spiral having a diameter in the neighborhood of 1 to 2 mils in accordance with known practice.
  • the lead wire or post 12, only the end of which is illustrated may be of any desired size and configuration, and preferably comprises a conductor adapted to extend from the interior of the finished lamp for completing an electrical connection to the filament 10.
  • the lead wire .12 has a surface formed of a metal capable of producing a diffusion bond with the metal of the body 14. l 1
  • the lead wire 12 is formed of a suitable conductive metal such as copper, dumet, or the like, while the body 14 is formed of gold.
  • the portion of the post .12 to which the body 14 is bonded is provided with a coating of highly pure gold.
  • an intermediate layer of nickel orother suitable material may be provided.
  • the body 14 of metal may be provided in any desired manner.
  • a metal wire 16 preferably fabricated of highly pure gold and having a diameter in the neighborhood of 1.5 mils is advanced from a supply such as a spool (not shown) through a tip member 18 having a central passageway 20 (FIG. 1) approximately 2 mils in diameter.
  • the body 14 is initially in the form of a ball or bead having a diameter of about 6 to 8 mils formed at the end of the wire 15.
  • the filament 10 is positioned upon the lead wire 12 between the lead wire and the body 14 of metal.
  • the filament 10 is located on the substantially flat end of the lead wire 12, although it should be appreciated that the filament 10 may be attached to other portions of the lead wire 12 if desired.
  • the arrangement shown in the drawing has the advantage that the connection created between the filament and the lead wire is small in size and low in profile and is 3 therefore particularly suited for use in extremely small lamps.
  • the body 14 is moved toward the filament and lead wire 12 as illustrated in FIG. 2.
  • the body 14 is pressed toward the lead wire 12 before heat is applied to the body 14.
  • This operation serves to compress or crush the spiral wound filament 10 into close engagement with the surface of the lead wire 12 due to the relative rigidity of the metal of the body 14.
  • This pressing operation may conveniently be carried out by forcing the tip member 18 against the ball or bead-like body 14 thereby to force the body 14 toward the lead wire.
  • the body 14 of metal is heated to a temperature sufiicient to place the metal in a plastic or semi-plastic state, but insufficient to melt the metal.
  • the temperature to which the body is heated in accordance with the invention is high enough so that the metal exhibits a substantial increase in intrinsic malleability and so that diffusion takes place at the interface of the body 14 and the surface of the lead wire 12. However, the temperature is maintained below the melting point of the metal of the body 14 and also well below the temperature at which the material of the lamp filament 10 becomes brittle.
  • the body 14 is formed of gold and is heated to a temperature in excess of about 450 C., this being the approximate temperature at which gold is capable of diffusion. Furthermore the temperature of the body 14 is maintained below the melting point of gold which is about 1065 C. It has been found that satisfactory results are obtained by heating the gold body 14 to a temperature of approximately 600-650 C. for a period of about three seconds while pressure is applied to the body 14. This can conveniently be carried out by applying heat to the body 14 through the tip element 18, which may in turn be heated in any suitable manner.
  • the metal of the body is in a highly malleable or semi-plastic state.
  • the metal closely envelops or entraps the lamp filament 10 and an intimate, large area contact is created between the body 14 and the filament 10.
  • a thermocompression bond is created between the body 14 and the surface of the lead wire 12. More specifically, under conditions of heat and pressure diffusion of the materials at the joint interface of the body 14 and the lead wire 12 takes place to produce a strong and highly conductive intermetallic or metallurgical bond.
  • the mechanical connection between the filament 10 and the lead wire 12 is firm and reliable.
  • the electrical resistance at the interconnection is low.
  • One important advantage of the method of the present invention is that little or no oxide is produced during the operation of terminating the lamp filament.
  • metallic oxides may be produced due to the use of certain mate rials and/or as a result of the degree of heat required to complete the termination. When heated to elevated temperatures during subsequent use, such oxides may result in contamination of the vacuum within the lamp and/ or darkening of the transparent face plate of the lamp. Since the temperatures required in carrying out the process of the present invention are relatively low, and since the process makes use of gold in a pure form, the problems resulting from the production of oxides are substantially eliminated.
  • the tip member 18 is moved away from the body 14 in order to expose a segment of the metal wire 16.
  • the wire is then severed above the body 14 in any suitable manner.
  • the wire 16 is melted so that the severing of the wire and the formation of a new body of metal for a subsequent termination operation can be accomplished simultaneously.
  • a source of heat such as a flame torch 22 is applied to the wire 16 so that the wire melts and is severed.
  • the melted metal at the end of the wire 16 is formed by the application of heat into a bead or ball serving as a metallic body such as the body 14 illustrated in FIG. 1.
  • the trail When the wire .16 is severed from the body 14, a short length or trail of metal remains. As shown in FIG. 4, the trail may have a thin portion designated as 24 produced as a result of pulling the wire 16 while the metal on the body 14 remains in a plastic state. In order to reduce the profile of the connection between the filament 10 and the lead wire 12, the trail may be removed from the body 14 by breaking it off.
  • thermocompression bonding equipment available from Wells Electronics, Inc. of South Bend, Ind. This equipment is ordinarily used for providing so-called nail head or ball bonds of a metal wire to a metal receiving surface such as a terminal of a microcircuit or the like, as described in an article entitled Microjoining Processes For Electronic Packaging, Part 3 by Ray B. Larson (Assembly Engineering, November 1966).
  • a method of providing a mechanical and electrical connection between a tungsten lamp filament and a metal lead having at least a surface portion of gold comprising the steps of:
  • step of heating comprising heating said body of gold to a temperature in the approximate range of 600 to 650 C.
  • a method of terminating a spiral wound tungsten lamp filament to a lead wire having a gold surface comprising: advancing a gold Wire through a tip member; beading the end of said wire to form a body of gold; sandwiching the filament between said body and said surface; applying pressure to said body thereby to compress said spiral against said surface; heating said body simultaneously to entrap said filament in said body and to produce a diffusion bond between said surface and said body, and severing said Wire from said body.
  • step of applying pressure being carried out by applying force to said tip memher while said tip member is in engagement with said body
  • said heating step being carried out by applying heat to said tip member while said tip member is in engagement with said body
  • said heating step comprising heating said body to a temperature between about 450 C. and about 1065 C.

Abstract

A LAMP FILAMENT IS RELIABLY AND FIRMLY CONNECTED BOTH ELECTRICALLY AND MECHANICALLY TO A LEAD WIRE OR MOUNTING POST BY A BODY OF METALLIC MATERIAL INTIMATELY ENTRAPPING THE FILAMENT AND METALLURGICALLY BONDED TO THE LEAD WIRE. IN ORDER TO TERMINATE THE FILAMENT, THE FILAMENT IS PLACED ON THE LEAD WIRE AND OVERLAID WITH A BODY OF METAL. THE METAL IS HEATED TO A PLASTIC OR SEMI-PLASTIC AND NON-LIQUID STATE AND IS PRESSED AGAINST THE FILAMENT AND LEAD WIRE SO THAT THE FILAMENT IS ENVELOPED BY THE METAL AND THE METAL IS DIFFUSION BONDED TO THE LEAD WIRE.

Description

Feb. 9,1971 I r I R. E. suvls 3,561,034
METHOD OF TERMI NATING A LAMP FILAMENT Filed Oct. 4, 1968 PRESSURE E FIG. 3
HEAT and PRESSURE I6 IN VENTOR: RICHARD E. SIMS,
By a 0), KOIQhF I Qn I gcwbhbotp, Udvs Affal'fleysf v United States Patent 3,561,084 METHOD OF TERMINATING A LAMP FILAMENT Richard E. Sims, Des Plaines, Ill., assignor to Chicago, Miniature Lamp Works, Chicago, 11]., a corporation of Illinois Filed Oct. 4, 1968, Ser. No. 765,149 Int. Cl. H01j 9/18, 9/36 US. Cl. 29-25.15 8 Claims ABSTRACT OF THE DISCLOSURE A lamp filament is reliably and firmly connected both electrically and mechanically to a lead wire or mounting The present invention relates to the manufacture of incandescent lamps, and more particularly to a new and improved method for terminating a lamp filament.
In the manufacture of incandescent lamps a filament such as a fine tungsten wire is mounted between a pair of lead wires or posts which serve both to support the filament and to complete a path for energization of the filament. Consequently it is of paramount importance that the interconnection between the filament and the lead wires or posts be firm, reliable, and characterized by extremely low electrical resistance.
An important object of the present invention is to provide an improved method of connecting a lamp filament to a lead wire.
Another object is to provide a method capable of producing a firm, strong and reliable mechanical connection between the filament and the lead wire.
A further object is to provide a method for producing a connection between a filament and a lead wire characterized by low resistance.
Another object of the invention is to provide a method for terminating a lamp filament wherein the production of oxide is avoided.
Another object is to provide an improved method for terminating a lamp filament wherein the connection between the filament and the lead wire is small in size and low in profile, and to provide a method particularly suited to the manufacture of miniature lamps such as numeric readout lamps and the like.
In brief, in accordance with the present invention a lamp filament is mounted to a lead wire by sandwiching the filament between the lead wire and a body of metal. The metal is simultaneously heated to a semi-plastic state and pressed against the lead wire. A metallurgical or intermetallic bond is created between the body of metal and the lead wire, and at the same time the filament is entrapped within the body of metal.
The invention together with the above and other objects and advantages may be better understood from the following detailed description of one process embodying the invention, in the course of which reference is made to the drawing wherein:
FIGS. 1-4 are somewhat diagrammatic and fragmentary illustrations of successive operations carried out in a process of terminating a lamp filament in accordance with the present invention.
Having reference now to the drawing, there are illustrated certain of the steps of a process performed in accordance with the present invention for mounting a lamp filament 10 to a lead wire 12 with a body 14 of metal. In general, and referring first to FIG. 1, the filament 10 is placed on the lead wire 12 and the body 14 of metal is positioned to overlie the filament 10- and lead wire 12. The metal body 14 is then moved toward the lead wire 12 to sandwich the filament 10 between the lead wire 12 and the body 14, as indicated in FIG. 2.
In accordance with an important feature of the invention the body 14 is heated to a plastic or semi-plastic state, but not to a liquid state, while being pressed against the filament 10 and the lead wire 12. As a result the filament is intimately surrounded or entrapped in the metal of the body 14 while an intermetallic or metallurgical bond is formed by diffusion at the interface of the body 14 and the lead wire 12. Due to the extensive and firm mechanical contact between the filament 10 and the body 14, and the thermocompression diffusion bond between the body 14 and lead wire 12, a highly reliable and conductive connection is produced.
The method of the present invention is particularly suited to the manufacture of miniature lamps such as numeric readout lamps wherein several filaments such as the filament 10 illustrated in the drawing may be connected between several lead wires or posts 12 and sealed in a vacuum beneath a transparent face plate. In the illustrated embodiment of the invention, the filament 10 is a tungsten wire having a diameter in the neighborhood of 0.3 mil and wound in a spiral having a diameter in the neighborhood of 1 to 2 mils in accordance with known practice. The lead wire or post 12, only the end of which is illustrated, may be of any desired size and configuration, and preferably comprises a conductor adapted to extend from the interior of the finished lamp for completing an electrical connection to the filament 10. In order to permit an intermetallic or metallurgical bond between the lead wire 12 and the body 14 of metal, the lead wire .12 has a surface formed of a metal capable of producing a diffusion bond with the metal of the body 14. l 1
In the preferred embodiment of the invention, the lead wire 12 is formed of a suitable conductive metal such as copper, dumet, or the like, while the body 14 is formed of gold. In order to permit the formation of a diffusion bond between the body 14 and the post 12, the portion of the post .12 to which the body 14 is bonded is provided with a coating of highly pure gold. In addition, in order to prevent diffusion between the body of the conductor 12 and the gold coating, an intermediate layer of nickel orother suitable material may be provided.
The body 14 of metal may be provided in any desired manner. In the illustrated arrangement, a metal wire 16 preferably fabricated of highly pure gold and having a diameter in the neighborhood of 1.5 mils is advanced from a supply such as a spool (not shown) through a tip member 18 having a central passageway 20 (FIG. 1) approximately 2 mils in diameter. The body 14 is initially in the form of a ball or bead having a diameter of about 6 to 8 mils formed at the end of the wire 15.
As illustrated in FIG. 1, in carrying out the method of the present invention the filament 10 is positioned upon the lead wire 12 between the lead wire and the body 14 of metal. In the preferred arrangement the filament 10 is located on the substantially flat end of the lead wire 12, although it should be appreciated that the filament 10 may be attached to other portions of the lead wire 12 if desired. The arrangement shown in the drawing has the advantage that the connection created between the filament and the lead wire is small in size and low in profile and is 3 therefore particularly suited for use in extremely small lamps.
After the body 14, filament 10, and lead wire 12 have been aligned with one another, the body 14 is moved toward the filament and lead wire 12 as illustrated in FIG. 2. In the preferred method, the body 14 is pressed toward the lead wire 12 before heat is applied to the body 14. This operation serves to compress or crush the spiral wound filament 10 into close engagement with the surface of the lead wire 12 due to the relative rigidity of the metal of the body 14. As a result the filament wire takes up a minimum of space in the region of the connection to the lead wire. This pressing operation may conveniently be carried out by forcing the tip member 18 against the ball or bead-like body 14 thereby to force the body 14 toward the lead wire.
In accordance with an important aspect of the present invention, there is created a firm and reliable connection between the body 14 and the filament 10 and also between the body 14 and the lead wire 12. As indicated in FIG. 3, this is accomplished by subjecting the body 14 to heat and to pressure to the end that the body 14 entraps or intimately envelops the filament 10 and at the same time forms an intermetallic or metallurgical bond with the lead wire 12.
More specifically, and in accordance with an important aspect of the invention, the body 14 of metal is heated to a temperature sufiicient to place the metal in a plastic or semi-plastic state, but insufficient to melt the metal. The temperature to which the body is heated in accordance with the invention is high enough so that the metal exhibits a substantial increase in intrinsic malleability and so that diffusion takes place at the interface of the body 14 and the surface of the lead wire 12. However, the temperature is maintained below the melting point of the metal of the body 14 and also well below the temperature at which the material of the lamp filament 10 becomes brittle.
In the preferred embodiment of the present invention, the body 14 is formed of gold and is heated to a temperature in excess of about 450 C., this being the approximate temperature at which gold is capable of diffusion. Furthermore the temperature of the body 14 is maintained below the melting point of gold which is about 1065 C. It has been found that satisfactory results are obtained by heating the gold body 14 to a temperature of approximately 600-650 C. for a period of about three seconds while pressure is applied to the body 14. This can conveniently be carried out by applying heat to the body 14 through the tip element 18, which may in turn be heated in any suitable manner.
During the operation of applying heat and pressure to the body 14, the metal of the body is in a highly malleable or semi-plastic state. As a result, under pressure the metal closely envelops or entraps the lamp filament 10 and an intimate, large area contact is created between the body 14 and the filament 10. Simultaneously, a thermocompression bond is created between the body 14 and the surface of the lead wire 12. More specifically, under conditions of heat and pressure diffusion of the materials at the joint interface of the body 14 and the lead wire 12 takes place to produce a strong and highly conductive intermetallic or metallurgical bond. As a result, the mechanical connection between the filament 10 and the lead wire 12 is firm and reliable. In addition, the electrical resistance at the interconnection is low.
One important advantage of the method of the present invention is that little or no oxide is produced during the operation of terminating the lamp filament. In some known methods of terminating a lamp filament metallic oxides may be produced due to the use of certain mate rials and/or as a result of the degree of heat required to complete the termination. When heated to elevated temperatures during subsequent use, such oxides may result in contamination of the vacuum within the lamp and/ or darkening of the transparent face plate of the lamp. Since the temperatures required in carrying out the process of the present invention are relatively low, and since the process makes use of gold in a pure form, the problems resulting from the production of oxides are substantially eliminated.
Having reference now to FIG. 4, after the bonding of the body 14 to the surface of the lead wire 12 together with the entrapping of the filament 10 has been completed, the tip member 18 is moved away from the body 14 in order to expose a segment of the metal wire 16. The wire is then severed above the body 14 in any suitable manner. In the preferred arrangement, the wire 16 is melted so that the severing of the wire and the formation of a new body of metal for a subsequent termination operation can be accomplished simultaneously. As illustrated in FIG. 4, a source of heat such as a flame torch 22 is applied to the wire 16 so that the wire melts and is severed. In addition, the melted metal at the end of the wire 16 is formed by the application of heat into a bead or ball serving as a metallic body such as the body 14 illustrated in FIG. 1.
When the wire .16 is severed from the body 14, a short length or trail of metal remains. As shown in FIG. 4, the trail may have a thin portion designated as 24 produced as a result of pulling the wire 16 while the metal on the body 14 remains in a plastic state. In order to reduce the profile of the connection between the filament 10 and the lead wire 12, the trail may be removed from the body 14 by breaking it off.
A significant advantage of the method of the present invention is that it may conveniently and economically be carried out with commercially available apparatus normally used for an unrelated purpose. For example, the invention may be carried out with thermocompression bonding equipment available from Wells Electronics, Inc. of South Bend, Ind. This equipment is ordinarily used for providing so-called nail head or ball bonds of a metal wire to a metal receiving surface such as a terminal of a microcircuit or the like, as described in an article entitled Microjoining Processes For Electronic Packaging, Part 3 by Ray B. Larson (Assembly Engineering, November 1966).
Although the present invention has been described with reference to details of one particular process embodying the invention, it should be understood that many alterations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Details of the process described here should not be taken to limit the invention except as set forth in the following claims.
What is claimed and desired to be secured by Letters Patent of the United States is:
1. A method of providing a mechanical and electrical connection between a tungsten lamp filament and a metal lead having at least a surface portion of gold comprising the steps of:
placing the filament on said surface portion of the lead;
placing a body of gold on the filament and over the surface portion of the lead;
heating the body of gold to a temperature below the melting point of gold and above the temperature at which the diffusion of gold takes place; and subjecting the body of gold to pressure of a magnitude great enough to cause the body of gold to surround the filament and to create a diffusion bond between the body of gold and the surface portion of the lead.
2. The method of claim 1, said step of heating, comprising heating said body of gold to a temperature in the approximate range of 600 to 650 C.
3. The method of claim 1 further comprising beading the end of a gold wire to form said body, and severing said wire from said body.
4. The method of claim 3, said severing step following said steps of heating and subjecting to pressure.
5. A method of terminating a spiral wound tungsten lamp filament to a lead wire having a gold surface comprising: advancing a gold Wire through a tip member; beading the end of said wire to form a body of gold; sandwiching the filament between said body and said surface; applying pressure to said body thereby to compress said spiral against said surface; heating said body simultaneously to entrap said filament in said body and to produce a diffusion bond between said surface and said body, and severing said Wire from said body.
6. The method of claim 5, further comprising continuing to apply pressure during said heating.
7. The method of claim 5, said step of applying pressure being carried out by applying force to said tip memher while said tip member is in engagement with said body, and said heating step being carried out by applying heat to said tip member while said tip member is in engagement with said body.
8. The method of claim 5, said heating step comprising heating said body to a temperature between about 450 C. and about 1065 C.
References Cited UNITED STATES PATENTS 1,238,575 8/1917 Schloter 29--25.13 2,082,079 6/1937 Palucki 29-25.1X 2,387,074 10/1945 Hroch 2925.1 3,221,386 12/1965 Demarest 2925.11 3,320,401 5/1967 Zachay et al. 228-44 JOHN F. CAMPBELL, Primary Examiner R. B. LAZARUS, Assistant Examiner US. Cl. X.R.
US765149A 1968-10-04 1968-10-04 Method of terminating a lamp filament Expired - Lifetime US3561084A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US76514968A 1968-10-04 1968-10-04

Publications (1)

Publication Number Publication Date
US3561084A true US3561084A (en) 1971-02-09

Family

ID=25072777

Family Applications (1)

Application Number Title Priority Date Filing Date
US765149A Expired - Lifetime US3561084A (en) 1968-10-04 1968-10-04 Method of terminating a lamp filament

Country Status (4)

Country Link
US (1) US3561084A (en)
DE (1) DE1949869A1 (en)
FR (1) FR2019895A1 (en)
GB (1) GB1222905A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3762029A (en) * 1971-08-04 1973-10-02 Ferranti Ltd Manufacture of supports for semiconductor devices
US3826000A (en) * 1972-05-18 1974-07-30 Essex International Inc Terminating of electrical conductors
US3889364A (en) * 1972-06-02 1975-06-17 Siemens Ag Method of making soldered electrical connections
US4038743A (en) * 1972-05-18 1977-08-02 Essex International, Inc. Terminating and splicing electrical conductors
WO1998032168A1 (en) * 1997-01-16 1998-07-23 Ford Motor Company Method for doping metallic connecting wire
WO2022033892A1 (en) * 2020-08-11 2022-02-17 Infrasolid Gmbh Arrangement and method for mechanically and electrically contacting a glow wire of a thermal radiation source made of refractory metal for semiconductor and microsystem technology

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
HU192884B (en) * 1984-05-14 1987-07-28 Pal Gal Method for cohesive bonding metal pieces by deformation indirect material particularly for members of small material thickness

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3762029A (en) * 1971-08-04 1973-10-02 Ferranti Ltd Manufacture of supports for semiconductor devices
US3771212A (en) * 1971-08-04 1973-11-13 Ferranti Ltd Manufacture of supports for use with semiconductor devices
US3826000A (en) * 1972-05-18 1974-07-30 Essex International Inc Terminating of electrical conductors
US4038743A (en) * 1972-05-18 1977-08-02 Essex International, Inc. Terminating and splicing electrical conductors
US3889364A (en) * 1972-06-02 1975-06-17 Siemens Ag Method of making soldered electrical connections
WO1998032168A1 (en) * 1997-01-16 1998-07-23 Ford Motor Company Method for doping metallic connecting wire
WO2022033892A1 (en) * 2020-08-11 2022-02-17 Infrasolid Gmbh Arrangement and method for mechanically and electrically contacting a glow wire of a thermal radiation source made of refractory metal for semiconductor and microsystem technology

Also Published As

Publication number Publication date
GB1222905A (en) 1971-02-17
FR2019895A1 (en) 1970-07-10
DE1949869B2 (en) 1970-12-23
DE1949869A1 (en) 1970-04-16

Similar Documents

Publication Publication Date Title
US3672047A (en) Method for bonding a conductive wire to a metal electrode
US7021521B2 (en) Bump connection and method and apparatus for forming said connection
US3781981A (en) Method for making armature-commutator assembly having armature winding of very small diameter
GB881832A (en) Improvements in or relating to the bonding of metals to bodies comprising semiconductive or brittle materials
US3561084A (en) Method of terminating a lamp filament
US6001724A (en) Method for forming bumps on a semiconductor die using applied voltage pulses to an aluminum wire
US3217401A (en) Method of attaching metallic heads to silicon layers of semiconductor devices
US3197608A (en) Method of manufacture of semiconductor devices
US3612940A (en) Lamp filament structure
JP2814985B2 (en) Method for manufacturing solid electrolytic capacitor
US3279038A (en) Method of making glass capsules for electrical components
US3172188A (en) Method of manufacture of semiconductor devices
US3329922A (en) Welded terminal resistor
JPH0212919A (en) Formation of bump electrode
US3637972A (en) Method and apparatus for forming an ohmic contact to high-resistivity silicon
US3147361A (en) Vacuum tight joint and method of making such joint
JPS6215810A (en) Method of connecting insulated covered electric wire to terminal
JPS61194735A (en) Semiconductor device
JPS62190734A (en) Manufacture of semiconductor device
JPS603134A (en) Wire bonding method
JPH01143176A (en) Manufacture of terminal or the like
JPS583239A (en) Bonding wire
JPH01245535A (en) Wire bonding of semiconductor element
JP2680232B2 (en) Wire bonding method with solder wire
JPS6379331A (en) Wire bonding equipment

Legal Events

Date Code Title Description
AS Assignment

Owner name: VCH INTERNATIONAL LIMITED, ENGLAND

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GENERAL INSTRUMENT CORPORATION, 225 ALLWOOD RD., CLIFTON, NJ 07012, A CORP. OF DE;REEL/FRAME:004746/0459

Effective date: 19870727

Owner name: VCH INTERNATIONAL LIMITED,BEETONS WAY, BURY ST. ED

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:GENERAL INSTRUMENT CORPORATION, 225 ALLWOOD RD., CLIFTON, NJ 07012, A CORP. OF DE;REEL/FRAME:004746/0459

Effective date: 19870727