CA1057421A - Process for making a brazed lead electrode, and product thereof - Google Patents

Process for making a brazed lead electrode, and product thereof

Info

Publication number
CA1057421A
CA1057421A CA264,663A CA264663A CA1057421A CA 1057421 A CA1057421 A CA 1057421A CA 264663 A CA264663 A CA 264663A CA 1057421 A CA1057421 A CA 1057421A
Authority
CA
Canada
Prior art keywords
joining
joining surface
brazing alloy
copper
lead
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
Application number
CA264,663A
Other languages
French (fr)
Inventor
Monroe B. Goldberg
William B. Voorhis
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.)
Arris Technology Inc
Original Assignee
General Instrument Corp
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 US05/642,588 external-priority patent/US4017266A/en
Application filed by General Instrument Corp filed Critical General Instrument Corp
Application granted granted Critical
Publication of CA1057421A publication Critical patent/CA1057421A/en
Expired legal-status Critical Current

Links

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
    • H01L24/01—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
    • H01L24/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L24/31—Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L24/33—Structure, shape, material or disposition of the layer connectors after the connecting process of a plurality of layer connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/02—Containers; Seals
    • H01L23/04—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls
    • H01L23/043—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls the container being a hollow construction and having a conductive base as a mounting as well as a lead for the semiconductor body
    • H01L23/051—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls the container being a hollow construction and having a conductive base as a mounting as well as a lead for the semiconductor body another lead being formed by a cover plate parallel to the base plate, e.g. sandwich type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H01L23/31—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape
    • H01L23/3157—Partial encapsulation or coating
    • 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
    • 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
    • H01L24/83—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 layer 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
    • H01L2224/83—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 layer connector
    • H01L2224/8319—Arrangement of the layer connectors prior to mounting
    • 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
    • H01L2224/83—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 layer connector
    • H01L2224/838—Bonding techniques
    • H01L2224/83801—Soldering or alloying
    • 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
    • H01L2924/01014—Silicon [Si]
    • 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
    • H01L2924/01015—Phosphorus [P]
    • 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
    • H01L2924/01018—Argon [Ar]
    • 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
    • H01L2924/0102—Calcium [Ca]
    • 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
    • H01L2924/0103—Zinc [Zn]
    • 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
    • H01L2924/01033—Arsenic [As]
    • 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
    • H01L2924/0104—Zirconium [Zr]
    • 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
    • H01L2924/01042—Molybdenum [Mo]
    • 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
    • H01L2924/01047—Silver [Ag]
    • 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
    • H01L2924/0105—Tin [Sn]
    • 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
    • H01L2924/01057—Lanthanum [La]
    • 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
    • H01L2924/01058—Cerium [Ce]
    • 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
    • H01L2924/01073—Tantalum [Ta]
    • 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
    • H01L2924/01082—Lead [Pb]
    • 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
    • H01L2924/01322—Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
    • 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
    • H01L2924/014—Solder alloys
    • 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
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/102—Material of the semiconductor or solid state bodies
    • H01L2924/1025—Semiconducting materials
    • H01L2924/10251—Elemental semiconductors, i.e. Group IV
    • H01L2924/10253—Silicon [Si]
    • 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
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/11—Device type
    • H01L2924/13—Discrete devices, e.g. 3 terminal devices
    • H01L2924/1304—Transistor
    • H01L2924/1306—Field-effect transistor [FET]
    • H01L2924/13062—Junction field-effect transistor [JFET]

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Connections Effected By Soldering, Adhesion, Or Permanent Deformation (AREA)
  • Fuses (AREA)
  • Ceramic Products (AREA)
  • Electric Connection Of Electric Components To Printed Circuits (AREA)
  • Manufacture Of Switches (AREA)

Abstract

Abstract of the Disclosure This relates to a process for making a brazed lead electrode work-piece, and such workpiece. The process for attaching a lead member to a con-tact member comprises initially providing a lead member formed substantially of a thermally and electrically conductive metal and terminating at one end in a joining surface, and an axially extending contact member formed substan-tially of a refractory metal and terminating in a joining surface of such refractory metal. The joining surfaces of the members are placed in contact with a silver/copper-based brazing alloy having a wetting point of at least 450 C. The brazing alloy is then heated (preferably in an inert atmosphere at atmospheric pressure) at least to its wetting point for a period of time sufficient to melt the brazing alloy. Thereafter the molten brazing alloy is allowed to cool and solidify in contact with the joining surfaces of the mem-bers, thereby to join the contact member and the lead member into a unitary structure. The workpiece comprises an axially extending contact member formed substantially of a refractory metal and terminating at one end in a joining surface, a lead member formed substantially of a thermally and electrically conductive metal and terminating at one end in a joining surface, and a brazing alloy disposed between and securing together the joining surfaces of the members, thereby to join the members into a unitary structure.

Description

:1~5~2~ ~

The present invention relates to a workpiece and a process for making a workpiece suitable for use in a semiconductor device, and more part-icularly a workpiece comprising a thermally and electrically conductive lead and a refractory metal contact joined by a high temperature brazing process.
Passivated semiconductor devices generally inclucle a semiconductor body composed substantially of silicon, a layer of passivating material such as glass or plastic disposed about the semiconductor body, and at least one metallic contact extending outwardly from the semiconductor body through the passivating layer as an external contact for connection with the associated ~ 10 circuitry. More specifically, such devices require that the metallic contacts be refractory in nature in order that the coefficients of thermal expansion Oe the semiconductor body, the passivating layer and the metallic contaots be reasonably matched to avoid breakage during thermal cycling. Molybdenum, tungsten, tantalum and various special;alloys are typical of the refractory metals used as such refractory metal contacts; however, since such materials 1 are both expensive and relatively poor conductors of both heat and electric ` current, the refractory metal contacts are generally joined to goQd convention-- al con~uctors ( such as copper, silver or various special alloys) just beyond :
th-e passivating layer, the connection between the refractory contact and the other circuitry elements being made by the conventional conductor. In the case ~ ;
of axial-lead-construction semiconductor rectifiers, the connection of the con-ventional axial lead to the refractory metal contact is accomplished by one of ;. the following two procedures.
In the first procedure, the refractory material is initially plated with a solderable metal such as silver before application of the passivating layer. After the passivating operation, the axial leads are attached to the refractory metal contacts using ~Isoft solder~' preforms with melting points ~`s typically less than 350 C. Devices containing such connections have the dis-.,~ .
advantages commonly associated with soft solder contacts. If extreme tempera-. ~, .

1~574~1 .~ . ' ture control is not exercised in soldering the axial lead to other circuit components~ the axial lead may detach from the refractory metal contact as the . .~ .
soft solder heats up. In any case, it has been found that such soft solder ~ ~ ~
, joints are subject to thermal fatigue and a resultant short operating life.
In the other procedure, the refractory metal contact is joined to the ' axial lead by a special welding process known as butt or percussion welding~
-~ The joint and the axial lead must thereafter be exposed to all the chemical and heat-treating processes subsequently required to (1) join the semiconductor body to the refractory metal contact, (2) etch the subassembly, and (3~ apply and fuse the passivating glass layer. The devices fashioned according to this pro-.... .
`~ cedure are not reliable in the first place because a true weld is not possible '`! between the refractory metal of the contact and the conventional conductive :, :
~ metal of the axial lead. Furthermore, the processing operations required to .'`~'.~ - -complete the semiconductor device subsequent to formation of the refractory con-tact/axial lead joint frequently result in a weak and porous joint which will develop high electrical and thermal resistance in time or eventually even fail ~: mechanically and fall off. Experience has shown that butt welded joints have ;;
extremely high failure rates when exposed to conductions of high temperature and - -high humidity, the failure rate rising as high as 50% at conditions of 85 C and 85% relative humidity. -` Yet another disadvantage of the process of joining a refractory metal contact to an axial lead by the butt or percussion welding technique is that ... ..
~; certain details of the technique are proprietary information, not readily avail-able on the open market. But even if the full details of this technique were ..... .
i generally known, its very nature imposes undesirable constraints on the design of the refractory metal contacts and the axial lea~suseful therein. In the technique, the axial lead is actually in motion as the weld between the axial .. ::
~; lead and the refractory metal contact is made, the parts being brought together : to make the electrical contact by rapid advance of the axial lead once the "::
'''' : ' ~ -2-:.., -.

:. . . ' . : :
: .
:: ~ .

`
~L0~74Zl refractory metal contact is in position. The technique requires that each refractory metal contact be inserted into an individual clamp-designed welding electrode in order to control the we]ding current. Thus, for the automatic rapid positioning essential to mass production, it is necessary that the dim-ensions of the refractory metal contact adhere to certain rigid specifications, `
and in particular that it be of a length sufficient to be grasped by the weld-ing electrode clamp. To insure reasonable centering of the axial lead relative ~
to the end of the refractory metal contact, the end of the~axial lead must ~ -generally be at least 0.5 mm. smaller in diameter than the end of the refract-ory metal contact. Thus the technique requires a minimum cross-sectional area ., for the refractory met-al contact and additionally imposes~a maxi~um cross-sectional area for the axial lead for a given refractory metal contact. These ; length and cross-sectional limitations restrict the degree of miniaturization `~ which can be obtained in any semiconductor device ultimately embodying the " axial lead/refractory metal contact subassembly.
Accordingly, it is an object of the present invention to provide a ~` process for attaching a thermally and electrically conductive lead to a refract- ~
ory metal contact using a high temperature brazing process. ~ ;
It is another object to provide such a process which avoids the afore-; 20 mentioned disadvantages of 'Isoft solder" and "butt welded~ joints.
It is also an object to provide such a process wherein the resultant joint is of higher physical strength and lower porosity than a butt-welded joint, ~;
withstands a higher temperature than a soft solder joint, and withstands condi~
tions of high temperature and high humidity better than a butt-welded joint.

". , . ~
It is a further object to provide such a process which does not i ffl ~ ~ -pose limitations on the minimum length or cross-section of the refractory metal contact or on the maximum cross-section of the axial lead for a given refractory metal contact and thus lends itself to unimpeded miniaturization of the semi-conductor device embodying the axial lead/refractory metal contact subassembly.

. " .

:- . .: . . , : - . - , , .

~ '74Z~L
Yet another o'bject is to provide such a process which is adapted to ~' mass production techniques.
Still another object is to provide such a process which utilizes a ' special preform, is simple and economical to perform, is less expensive than butt welding, and provides a joint superior to those produced by soft solder or 'butt welding processes.
A final object is to provide a brazed lead electrode workpiece adapted ~ for use in a semiconductor device and comprising a lead member joined to a l~ refractory metal contact by the aforesaid brazing process.
It has now 'been found that the above and related objects of the present ~ 5 ; invention are obtained in a process for attaching a lead member to a cortact ., .
'~ member by initially providing a lead member formed substantially of a thermally and electrically conductive metal and terminating at one end in a joining sur~
; faceg and an axially extending contact member formed substantially of a '~
'x refractory metal and terminating in a joining surface of such refractory metal~
The joining surfaces of the members are placed in contact with a silver/copper-~'~ based brazing alloy having a wetting point of at least 450 C. The brazing .,~ , alloy is then heated (preferably in an inert atmosphere at atmospheric pressure) ~ '"
- at least to its wetting point for a period of time sufficient to melt the ' 20 brazing alloy. Thereafter the molten brazing alloy is allowed to cool and sol-'- idify in contact with the joining surfaces cf the members, thereby to join the `~l contact member and the lead member into a unitary structure. '':~',,., :.
The refractory metal is selected from the group consisting of tungsten, '` molybdenum, tantalum, and alloys thereof, and is preferably molybdenum. The ~'~ conductive metal is selected from the group consisting of sllver and copper and ''~3 alloys thereof, and is preferably copper. A preferred brazing alloy is, on a weight basis, about 80-89% copper~ about 5-15% silver and about 4-6% phosphorus~preferably an 80/15/5 alloy. Preferably, the brazing alloy is provided as a ` preform with joining surfaces of substantially $imilar configuration and size ~, ' '' ' ' ''' ' ~ : '` ' '"'' ' : ' lOS7~

a~utting the joining surfaces of the members.
The present invention provides a brazed lead electrode workpiece adapted for use as a component of a semiconductor device. The workpiece com-prises an axially extending contact member formed substantially of a refractory metal and terminating at one end in a joining surface, a lead member formed substantîally of a thermally and electrically conductive metal and terminating at one end in a joining surface, and a brazing alloy melting point of at least 450 C disposed between and securing together the joining surfaces of the mem-bers, thereby to join the members into a unitary structure.
Figure 1 is a fragmentary exploded plan view of a workpiece according to the present invention.
Figure 2 is a fragmentary plan view of workpiece of Figure l; and Figure 3 is a fragmentary plan view of a semiconductor device incorp-orating the workpiece as a component thereof.
Referring now to the drawing, and in particular to Figure 2 thereof, therein illustrated is a brazed lead electrode workpiece embodying the principles of the present invention and generally designated by the numeral lO~the in-dividual components thereof being illustrated in exploded view in Figure 1.
~ Generally speaking, the workpiece 10 comprises an axially extending contact - 20 member generally designated by the numeral 20, a brazing alloy generally designated by the numeral 30~ and a lead member generally designated by the ~;-; numeral 40. The workpiece 10 is adopted for use as a component of a semi-conductor device or subassembly S0 including a semiconductor body 52, as illustrated in Figure 3.
More specifically7 the axially extending contact member 20, generally referred to as a ~'slug~', includes joining surfaces 22 and 24 at opposite ends thereof. The contact member 20 is formed substantially of a refractory metal material and is preferably composed substantially of molybdenum, tungsten, tantalum and alloys thereof. Whether the alloys be composed of two or more of .. ..

: '' '' ' ~ : . : ' :' ~

; 1~5~74z~
the aforementioned refractory metals or of one or more of the refractory metals with other materials, the alloys must~ of course, be selected according to their Isnown coefficients of expansion to insure that the coefficients of expansion of the se~iconductor body 52, the contact member 20 and any materials used to passivate the semiconductor body 52 are compatible.
The brazing alloy preform 30 is of relatively planar configuration and has opposed joining surfaces 32 and 34 at opposite ends thereof. The ~- brazing alloy is a coppellsilver-based alloy having a wetting point of at least 450 C. The alloy may include, on a weight basis3 up to 25% of metals other than copper and silver--for example, nickel, tin, phospho~s, etc.--so ..
long as it is devoid of any high vapor pressure metals~(such as zinc or cadmium)which might adversely affect the semiconductor body 52 to which the workpiece 10 will ultimately be secured. Any available copper/silver-based brazing alloy having a wetting point of at least 450 C may be used provided that the alloy is capable of effectively wetting and bonding with both the refractory metal of -contact member 20 and the conductive metal of lead member 40.
A preferred brazing alloy comprlses on a weight bases about 83-89%
copper, about 5-15% silver, and about 4-6% phosphorus, and may be a commerc-ially available 80/15/5 high temperature brazing alloy marketed by Englehard " Industries Division of Englehard Minerals and Chemicals Corp. (Murray Hill, ~ ~ New Jersey) under the trademark ~Silvaloy 15~~ and by Handy and Harmon, Inc.
i under the trademark "Silfos". This brazing alloy is characterized by a freez-ing point of about 640 C and a wetting point of about 705 C. Because the ;~ -i phosphorus acts as a flux, it requires neither an oxidizing nor a reducing environment externally maintained during the brazing process. In this brazing alloy composition~ the copper (melting point 1083 C) constitutes the main brazing component, with the silver (melt m g point 960 C) and the phosphorus (melting point 44 C) lowering the wetting point of the composition to a desir-able temperatvre, and the phosphorus also providing the necessary flu7sing _~ ' ~5742~

action to enable brazing in an inert atmosphere.
Other preferred brazing alloys include the 56-72/28-42 copper/silver_ based alloys such as a 72/2~ Ag/Cu eutectic commercially known as "BT braze"
(avai]able from Handy and Harmon, Inc. under the tradename "720 ALIOY"), a 71.5/28/0.5 Ag/Cu/Ni alloy ~qlS AIIOY"), a 60/30/10 Ag/Cu/Sn alloy ("603 AIIOYIl), a 56/42/2 Ag/Cu,~Ni alloy ("559 AILOY"), etc. These bra~ing alloys are characterized by a freezing point of about 620-765C and a wetting point of about 620- 850 C. As they contain no flux, these ~brazing alloys require a slightly reducing environment externally maintained during the brazing process (such as is conventionally provided by the presence of hydrogen gas)O Accord-ingly, these brazing alloys are preferably used only when the lead members 40 are composed of materials which are not particularly subject to hydrogen em-brittlement - e.g., oxygen-free copper. ;
The nail-headed axial lead member 40 has a joining surface 42 on the exposed surface of the head 44 thereof, the tail or other end being available ~i; for connection to other circuitry membersO The lead member 40 is formed of a .; ... .
thermally and electrically conductive metal such as copper, silver, or alloys thereof, the alloys of such metals by themselves or individually with other .. . . . .
` materials being selected for their ability to braze well with the brazing alloy of the preform 30. While it is preferred that the conductive metal of joining surface 42 be formed substantially of the aforementioned copper, silver or alloys thereof, a core or sheath is frequently used in connection with the Gon- :
tact member 40 to facilitate its function~ig as a heat sink for the semiconduct-.
or body 52, to reduce the cost of the materials used in the lead member 40, and/or to provide magnetic susceptibility for lead member 40. Suitable materials for the lead member thus include oxygen-free copper (especially suited for use in a reducing atmosphere), zirconium copper (for a stiffer lead~ and copper clad iron (for economy).
The lead member 40 may be joined to the contact member 20 by placing .,., ' ~

:lOS74Z~

the joining surface 42 of the lead member 40 and the joining surface 24 of the contact member 2Q in contact with the joining surfaces 34 and 3~ respectively, - ' of the preform 30. To facllitate this operation the various joining surfaces 24, 32, 34, 42 are preferably of the same size and configuration. If desired~
the lead member joining surface 42 m~y be greater in cross-section than the contact member joining surface 24. The preform 30 is then rapidly heated (for .
about 15 minutes) at least to its wetting point, held at that temperature for a period of time sufficient to melt the alloy (generally about 5 minutes) and ; thereafter the molten alloy of the preform 30 is allowed to cool and solidify : 10 n contact with the joining surfaces 24, 42 of the contact member 20 and lead member 40, thereby joining the members 20, 40 into a unitary structure. Where j the brazing alloy 30 contains a flux, this brazing operation may be performed .~
under atmospheric conditions--i.e., in a reducing, inert~ or oxidizing envir-onment; otherwise a slightly reducing atmosphere is required.
In a preferred embodiment of the process, the components of the workpiece are assembled in a subassembly, as indicated in Figure 2, with the ~; joining surface 24 of the contact member 20 contacting the joining surface 32 of the preform 30, and the other joining surface 34 of the preform 30 contact-,~
ing the joining surface 42 of the lead member 40. A brazing fixture or jig of ,! graphite~ stainless steel or other conventional material is suitably employed to hold the components of the subassembly in proper orientation during passage through the furnace. The entire subassembly is then placed on a conveyor belt ~ -~ which carries it through a tunnel furnace which, if desired, may be provided - with an inert atmosphere (such as dry nitrogen) at one atmosphere pressure.
m e maximum temperature within the tunnel furnace must be sufficient to wet or ~' melt the brazing preform 30, and is preferably about 10-15 C higher. Generally ' a dwell time of about 15-2~ minutes within the tunnel furna;ce is sufficient to l cause brazing of the lead member 40 to the contact member 20. Preferably the . .
~ entire subassembly 10 is heated over a 15 minute entry period to at least the ... .. . .
~ 8-,:.

~05~4Z~

wetting point of the brazing alloy, held there for about 5 minutes, and then slowly cooled over a 15 minute period to below the wetting point of the brazing alloy . The workpiece may then be further cooled and is then ready for sale or incorporation into a se~iconductor device.
The process results in the workpiece components being integrated into a unitary structure having bra3ed joints which withstand higher tempera-tures than soft solder joints, are stronger and less porous than butt welded ` joints, and withstand thermal cycling to high temperatures and high humidity conditions (such as 85C and 85% relative humidity) without failure or the development of high electrical and thermal resistances. The solidity and strength of the brazed joints thus formed permit the workpiece 10 to be further ~ ;
processed without resultant damage thereto.
Referring now to Figure 3g therein illustrated is a semiconductor ;~
device subassembly generally designated by the numeral 50 and incorporating therein a pair of workpieces 10. The semiconductor generally designated by the numeral 52 comprises a diffused silicon chip 54 and, at each end thereof, a layer of evaporated aluminum 56 forming a joining surface for the semiconduc-tor 52. The semiconductor body 54 is formed substantially of silicon, although one or more portions thereof may have minute quantities of various conventional ."
dopants such as phosphorus, boron and the like~ as will be well recognized by those skilled in the semiconductor art. For clarity of illustration the semi-conductor 52 has been illustrated as a rectifier adapted for connection to only two lead members~ although the workpieces 10 of the present invention may be attached to any other semiconductors, such as the N-type, P-type, or combination ` type and those useful as junction, field effect, or other types of semiconductors.
The workpiece 10 of the present invention may be used regardless of whether the semiconductor device comprises a single thin wafer-like diode (as shown) or a relatively long stack of several chips joined in series and brazed together with conventional materials (such as aluminum), with each of the various chips having . - _ g_ ' :

.: ~ : -. : .- .
. . : ; : . :. .

~OS7~Z~

a plurality of workpieces and/or other leads extending therefrom. The alumi-num joining surfaces 56 may be applied to the silicon body 54 by conventional techniques well knol1n in the semiconductor art, the preferred technique being an evaporation deposition technique.
Each workpiece 10 is easily incorporated in the semiconductor device 50 as follows: The refractory contact member 20 is joined to the semiconductor chip 52 by placing refractory joining surface 22 against aluminum joining sur-face 56 and conventionally brazing the aluminum joining surface 56 to both of the surfaces 52 and 22, to form a refractory metal/aluminum/silicon brazed joint.
The aluminum and silicon form a ~hard contactJJ eutectic having a melting point of about 575C which joins extremely well with both the silicon body 54 and the refractory metal joining surface 22. Due to the nature of the alumin~lm and .`J silicon materials involved, it is essential that this joint be formed by brazing ~ in an inert atmosphere (i.e., one that is neither an oxidizing nor a reducing ; atmosphere), and is typically performed in a controlled environment of one atmosphere, or slightly higher, of dry nitrogen, argon, or a similar inert gas.
~ - Thereafter, the exposed surface ofthe semiconductor body 54 is pre-- ferably etched to remove contaminants (e.g., with a solution of nitric and hydro M uoric acids), and a layer of passivating material 60 applied thereto to prevent recontamination. The passivating material 60 is applied over the-ex-posed surface of semiconductor body 54 and a portion of the contact member 20 between the joining surfaces 22~ 24 thereof to completely encapsulate the semi-conductor device 52 and protect it from exposure to contamination. The passiv-~` ating material 60 is typically plastic or glass which has been finely ground ~t into a slurry, applied by a conventional technique onto the exposed surface of ^ the semiconductor body 54, and finally heated in situ to a temperature suffi-, .
cient to f`use the passivating material 60. For example, a tunnel furnace may be maintained at a temperature of about 685 C to about 700 C to fuse a glass passivating material 60 applied to the semiconductor device 52. Both the : :; .

-::. . : . . . : .
. .:: , . ,, . :, . . : , , , : .

~L05'742~l preform 30 and the eutectic at the joints may become fluid again at the tempera-tures in the tunnel furnace; however, the surface tensions of the brazed joints formed in the brazing processes are sufficient to maintain the molten joints until cooling reoccurs as the subassembly leaves the tunnel furnace.
Because the passivating material 60, the semiconductor body 54 and the refractory member all exhibit compatible coefficients of expansion, the passivated semiconductor devices incorporating workpieces 10 of the present invention exhibit a desirably long life under repeated thermal cycling.
^ It will be noted that brazed lead electrode or workpiece of the 10 present invention may be produced on standard industrial equipment and does not require the use of the proprietary information or proprietary equipment in-volved in butt or percussion welding. Furthermore, the process lends itself well to the production of workpieces in mass production quantities as the re- ~
fractory metal contacts require neither insertion into nor retention by indiv- ~ ;
idual welding electrode clamps. As the joint between the axial lead and the refractory metal contact is not formed while one of the parts is in motion, there are`no minimum or maximum length or cross-sectional area requirements for either the axial lead or the refractory metal contact. Indeed, according to the present process~ the joining end of the axial lead may be larger in ~ ~
cross-section than the joining end of the refractory metal contact, so that ~ ;
- the entire joining end of the refractory metal contact member contacts the . .~
joining end of the wire lead, thus providing both greater strength for the joint and better conduction between the members thereof. The absence of a maximum cross-sectional area specification for the wire lead, relative to a glven refractory metal contact, permits the use of axial leads of a given diameter despite progressive miniaturi7ation of the refractory metal contact.
Finally the brazed lead electrode of the present invention is more reliable than a comparable butt or percussion welded joint electrode because its lack of porosity and its generally larger joint cross-section provide a joint of : -11- ~
, ~:

.. , ,~

.. . . . . . . . . . . . .

105~21 . .
greater strength and thus a joint which is better able to resist the physical processes encountered during incorporation of the brazed lead electrode into the ultimate semiconductor device. Most importantly, semiconductor devices incorporating the brazed lead electrodes of the present invention are able to withstand high hw~idity and high temperature conditions with negligible fail-; ures as opposed to similar devices incorporating butt or percussion welded lead electrodes, the latter exhibiting significant failure rates under similar conditions.
Now that the preferred embodiments of the present invention have been shown and described, various modifications and improvements thereon will become ` readily apparent to those skilled in the art. For example, special high temp~r-ature metallic compositions such as dumet (a nickel/iron core sheathed in copper) or copper-clad iron may be considered as equivalent to a refractory metal for the purposes of the present in~ention. As another example, the semi~
conductor body may bea diff`used silicon chip without any aluminim joining surfaces thereon, and the refractory contact may be joined to an exposed sur-~`~ face of the diffused silicon chip using an aluminum preform therebetween.
Accordingly, the spirit and scope of the present invention is to be understood as being limited not by the foregoing disclosure, but only by the appended claims.

;, :
, ' ~. i "i ,:

~', ~" '' ".
:~ : . , !

.
' .`; , ' . ,: . ' ' ' ' ' " . , ' . : :
' ;' , . , ~ ' '~ "~ ~ " , . , ' ' ' ' ' ,' . ' '

Claims (21)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for attaching a lead member to a contact member com-prising the steps of A) providing a lead member formed substantially of a thermally and electrically conductive metal and terminating at one end in a joining surface and an axially extending contact member formed substantially of molybdenum and terminating in a joining surface of said molybdenum; B) placing said joining surfaces of said members in contact with a silver/copper-based brazing alloy having a wetting point of at least 450°C; C) heating the brazing alloy at least to its wetting point for a period of time sufficient to melt the brazing alloy; and D) allow-ing the molten brazing alloy to cool and solidify in contact with said joining surfaces of said members, thereby to join said contact member and said lead member into a unitary structure.
2. The process of Claim 1 wherein the conductive metal is selected from the group consisting of silver and copper and alloys thereof.
3. The process of Claim 2 wherein said conductive metal is copper.
4. The process of Claim 1 wherein the heating of step (C) is per-formed in an inert or slightly reducing atmosphere at substantially atmospheric pressure.
5. The process of Claim 1 wherein said joining surface of said members are of substantially the same configuration and size, and wherein the brazing alloy is provided as a preform with joining surfaces of substantially similar configuration and size abutting said joining sur-faces of said members.
6. The process of Claim 1 wherein said lead member joining sur-face is greater in cross-section than said contact member joining surface.
7. The process of Claim 1 wherein said brazing alloy comprises on a weight basis about 80-89% copper, about 5-15% silver and about 4-6% phosphorus.
8. A process for attaching a lead member to a contact member com-prising the steps of A) providing (i) an axially extending contact mem-ber formed substantially of a refractory metal and haying at one end a joining surface of said refractory metal; (ii) a lead member formed sub-stantially of a thermally and electrically conductive metal and having at one end a joining surface; and (iii) a brazing preform formed sub-stantially of a silver/copper-based brazing alloy having a wetting point of at least 450°C., and having a joining surface at each end thereof; B) forming an assembly by simultaneously contacting (i) said refractory metal joining surface of said contact member to one of said brazing alloy joining surfaces of said preform; and (ii) the other of said brazing alloy joining surfaces of said preform to said conductive metal joining surface of said lead member; C) heating said assembly at least to the alloy wetting point to cause brazing of contacting joining sur-faces; and D) allowing said assembly to cool, thereby to join said con-tact member, said preform, and said lead member into a unitary structure.
9. The process of Claim 8 wherein said refractory metal is se-lected from the group consisting of molybdenum, tungsten, tantalum, and alloys thereof.
10. The process of Claim 9 wherein said refractory metal is molybdenum.
11. The process of Claim 8 wherein said conductive metal is selected from the group consisting of copper and silver and alloys thereof.
12. The process of Claim 8 wherein said conductive metal is copper.
13. The process of Claim 8 wherein the heating of step (C) is per-formed in an inert or slightly reducing atmosphere at substantially at-mospheric pressure.
14. The process of Claim 8 wherein said lead member joining surface is greater in cross-section than said contact member joining surface.
15. The process of Claim 8 wherein said brazing alloy comprises on a weight basis about 80-89% copper, 5-15% silver, and about 4-6% phos-phorus.
16. A brazed lead electrode workpiece for use in a semiconductor device comprising: A) an axially extending contact member formed sub-stantially of molybdenum and terminating at one end in a joining surface;
B) a lead member formed substantially of a thermally and electrically conductive metal and terminating at one end in a joining surface; and C) a silver/copper-based brazing alloy having a wetting point of at least 450°C brazed with and securing together said joining surface of said mem-bers, thereby to join said members into a unitary structure.
17. The workpiece of Claim 16 wherein the conductive metal is se-lected from the group consisting of silver and copper and alloys thereof.
18. The workpiece of Claim 17 wherein said conductive metal is copper.
19. The workpiece of Claim 16 wherein said joining surfaces of said members are of substantially the same configuration and size.
20. The workpiece of Claim 16 wherein said lead member joining surface is greater in cross-section than said contact member joining sur-face.
21. The workpiece of Claim 16 wherein said brazing alloy comprises on a weight basis about 80-89% copper, about 5-15% silver, and about 4-6% phosphorus.
CA264,663A 1975-12-19 1976-11-02 Process for making a brazed lead electrode, and product thereof Expired CA1057421A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US05/642,588 US4017266A (en) 1974-04-24 1975-12-19 Process for making a brazed lead electrode, and product thereof

Publications (1)

Publication Number Publication Date
CA1057421A true CA1057421A (en) 1979-06-26

Family

ID=24577211

Family Applications (1)

Application Number Title Priority Date Filing Date
CA264,663A Expired CA1057421A (en) 1975-12-19 1976-11-02 Process for making a brazed lead electrode, and product thereof

Country Status (6)

Country Link
AU (1) AU505174B2 (en)
CA (1) CA1057421A (en)
DE (1) DE2619869A1 (en)
FR (1) FR2335954A2 (en)
IT (1) IT1069952B (en)
MX (1) MX3349E (en)

Also Published As

Publication number Publication date
AU505174B2 (en) 1979-11-08
AU1377576A (en) 1977-11-17
FR2335954A2 (en) 1977-07-15
IT1069952B (en) 1985-03-25
DE2619869A1 (en) 1977-06-30
MX3349E (en) 1980-10-06

Similar Documents

Publication Publication Date Title
KR970010891B1 (en) High temperature lead-free tin based solder composition
KR0124518B1 (en) Lead-free high temperature tin based multi-component solder
EP0847828A1 (en) Solder material and electronic part using the same
US3996602A (en) Passivated and encapsulated semiconductors and method of making same
JPS6187396A (en) Manufacture of electronic circuit device
JPH0788679A (en) Lead-free tin antimony bismuth copper solder
US3930306A (en) Process for attaching a lead member to a semiconductor device
EP1402988B1 (en) The use of a solder on surfaces coated with nickel by electroless plating
US5008735A (en) Packaged diode for high temperature operation
KR102242388B1 (en) Solder alloy, solder bonding material and electronic circuit board
CN102017107A (en) Joint structure and electronic component
US4017266A (en) Process for making a brazed lead electrode, and product thereof
JP3721073B2 (en) Solder material, device or apparatus using the same, and manufacturing method thereof
US4504849A (en) Semiconductor devices and a solder for use in such devices
US5341981A (en) Use of a cadmium-free silver alloy as brazing solder (III)
CA1057421A (en) Process for making a brazed lead electrode, and product thereof
KR100595037B1 (en) Soldering Filler Metal, Assembly Method for Semiconductor Device Using Same, and Semiconductor Device
US3065534A (en) Method of joining a semiconductor to a conductor
US3665589A (en) Lead attachment to high temperature devices
JP2001244622A (en) Electronic circuit device
JP3670432B2 (en) Solder for thermoelectric cooling device
JP2005177842A (en) Brazing material, manufacturing method of semiconductor device using the same and semiconductor device
CN115283774B (en) Treatment process of Cu-Cr-Zr alloy lead wire for packaging shell
JP2668569B2 (en) Brazing material
GB2031223A (en) Method for bonding a refractory metal contact member to a semiconductor body