US3015761A - Semi-conductive electrode system - Google Patents

Semi-conductive electrode system Download PDF

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US3015761A
US3015761A US745032A US74503258A US3015761A US 3015761 A US3015761 A US 3015761A US 745032 A US745032 A US 745032A US 74503258 A US74503258 A US 74503258A US 3015761 A US3015761 A US 3015761A
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wire
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aluminum
aluminium
oxide layer
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Esselin Ludovicus Au Lambertus
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    • H01L24/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
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Definitions

  • transistors or crystal diodes having a semi-con-v ductive body to which oneend of at least one electrode wire is secured by fusion.
  • Electrodes of aluminum are therefore manufactured by applying by fusion either pellets the electrodematerial, in the present case in the wire,
  • An object of the invention is inter alia to provide a construction in which these disadvantages do not occur,v
  • Such a wire may be manufactured by filling an aluminum tube with the other material and subsequently reducing the cross-section of the whole by swaging or expanding.
  • FIG. 1 shows diagrammatically a side-view of a diode
  • FIG. 2 shows a device for applying wires to semioonductive bodies by fusion. 7
  • FIG. 3 is a cross-sectional view of a semi-conductor device according to the invention.
  • the diode shown in FIG. 1 comprises a thin silicon disc 1 of conductivity, to which an aluminum wire 2 is secured by fusion in an oven at a temperature preferably higher than the melting point of aluminum, for instance 8009 C.
  • the oven temperature may however in principle be lower than the melting point of aluminum, but higher than the eutectic temperature of the silicon-aluminum mixture.
  • the heating takes place in reducing surroundings, for example in a mixture of nitrogen and hydrogen.
  • a small addition of hydrochloricacid gas as a flux enhances adhesion of the wire to the body.
  • the wire is provided with a genetic oxide layer 3 which ensures that the form of the wire substantially does not change during heating and that flowing-out of the aluminum is restricted within certain limits.
  • the strengthened oxide layer is naturally not present at the area wherethe aluminum must fuse togetherwith the silicon. [The reoxide sheath.
  • the thickness of the wire' is not essential According to the invention, the wireof which at least t the envelope consists of aluminum, has so thick a genetic oxide layer on its cylindrical outer surface that fusion of the aluminum is possible without breakage of the oxide layer.
  • Said oxide layer preferably has a thickness comprised between 5 and 40 microns. Consequently, this layer is much thicker than the natural oxide layer already present on aluminm and which has a thickness'of only 0.1 to 0.2 gt. 1
  • An oxide layer of sufficient thickness maybe obtained in a simple manner by chemical means or by anodic'.
  • the method according to the invention is characterized in that a wire, of which at least the envelope consists of aluminum, is provided with a genetic oxide, layer of a thickness such that fusion of the aluminum is possible without breakage of the oxide. layer, whereupon one end of this wire is secured by fusion to a semi-conductive body. It will be evident that it is also possible for short pieces to be cut from a long oxidized wire.
  • a genetic oxidelayer is to be understood to mean a layer, the aluminum content of which substantially originates from the initial wire.
  • oxide layer is to be understood to mean also layers consisting of oxide hydrates, such as the compound Al O -H O, and furthermore oxide layers strengthened by impregnation or in another way, as will be discussed more fully hereinafter.
  • the'wire homogeneously consists of aluminum.
  • a wire having an envelope of aluminum and a core of a different material may fuse together.
  • the core may consist, for example, of semi-conductive material, such as germanium or silicon. Its presence in to the invention and is usually from lOOmicrons to several millimetres in practice. a Y
  • The, semi-conductive body is means of tin solder 4.
  • the aluminum wire with its strengthened. oxide layer may be manufactured in various ways. known per se, that is to say by purely chemical means or an anodic oxidation.
  • the last-mentioned method usually gives thicker oxide layers than the first-mentioned and is therefore preferable for comparatively thick wires.
  • the wire is dipped for 4 minutes in an oxidizing bath of the conventional type containing for example,
  • the wire is then carefully rinsed and dried.
  • the thickness of the oxide layer is from 3 to 5 microns.
  • Example I Aluminum wire degreased as described in Example I is subjected at 20 C. to an anodic treatment at 60 volts (direct voltage) for one hour.
  • the bath was a conventional one, containing 50 guts. of oxalic acid C H H 2H O per litre. Also other oxidizing baths are suitable.
  • the thickness of the resultant oxide layer was about 40 microns.
  • the oxidized wire obtained in accordance with Example i or II there are cut oif pieces each having a length of mms, which in a jig of graphite are placed on the bodies of silicon (see KG. 2).
  • the jig is constituted by two parts 11 and 12, which fit into each other.
  • the part 12 has recesses 13, by which the semi-conductive bodies are kept in position, and perforations 14, by which the pieces of Wire 10 are centred with respect to the bodies.
  • the pieces of wire are found to have retained their initial form.
  • the semi-conductive bodies are after-etched in the usual manner, for example with the use of hydrofluoric .acid, the strengthened oxide-layer then again having the advantage of protecting the aluminum itself against chemical attack.
  • the pieces of Wire 10, before being applied by fusion are preferably provided with a fiat end by polishing or filing.
  • the pieces of wire 10 may be connected by" spot- Welding to a piece of cop-per Wire or copper cable which may be connected by soldering to a connecting member.
  • the strengthened oxide layer is naturally broken through, but this is not dangerous, the operation being effected at some distance from the semiconductive body.
  • FIG. 3 shows an example of such a'structure applied to a diode in an evacuated envelope.
  • the envelope comprises a base with a threaded stud 31 for attachment, and a cap 32.
  • the cap 32 contains a glass leadthrough insulator 33 containing a small metallic tube 34.
  • the aluminum wire 10 is secured by spot-Welding to a copper Wire '36 at 35.
  • the base 30 and the cap 32 are secured together by means of flanges 37 and 38, for example by Welding. Subsequently, the envelope is fully closed due to the copper wire 36 being soldered in the tube 34.
  • The-latter may contain or consist of an active impurity such as a donor and/or an acceptor, but also semi-conductive material and more
  • the silicon body 1 is soldered to the base 30,
  • An electrode comprising a wire-like ele ent adapted for fusion at one end to a semiconductive body, the outer Wire portions consisting essentially of aluminum and containing a genetic oxide layer'having a thickness between 3 and 40 microns enabling fusion of the alu minum without destruction of the layer.
  • a semiconductor device comprising a semiconductive body, and a Wire-like element fused at one end to the semiconductive body, the outer wire portions consisting essentially of aluminum and containing a genetic aluminum oxide layer having a thickness between about 3 and 40 microns.
  • a 3. A device as set forth in claim 2 wherein the wirelike element comprises a core of a semiconductive material, an envelope of aluminum, and a surrounding aluminum oxide coating.
  • wirelike element comprises a core of an impurity material, an envelope of aluminum, and a surrounding aluminum oxide coating.
  • a semiconductor device comprising a semiconductive silicon body, and an aluminum wire-like element fused at one end to the semiconductive body, the outer wire portions containing a genetic aluminum oxide layer having a thickness between about 5 and 40 microns.
  • a method of making a semiconductor device comprising, providing a wire whose outer portions consist essentially of aluminum, subjecting said Wire to an oxidizing treatment'to provide on the aluminum portions a genetic'oxide' layer having a thickness enabling the aluminum to be fused without desruction of the oxide layer, and using an end of the said Wire to a semiconductive body.
  • a method of making a semiconductor device comprising providing a wire whose outer portions consist essentially of aluminum, subjecting said Wire to an oxidizing treatment to provide a'genetic oxide layer having a thickness of at least about 5 microns, placing a cut end of the said wire in contact with a semiconductive body, and heating the assembly at a temperature at which I the wireend fuses to the semiconductive body.
  • a method of making a semiconductor device comprising providing an aluminum wire, subjecting said Wire to an oxidiring'treatment to provide thereon a genetic aluminum oxide layer having a thickness between 3 and 40 microns, placing a cut end of the wire in contact with a silicon semiconductive body, and heating the assembly in an oven at a temperature above the eutectic temperature of the silicon-aluminum alloy and at which the 2,840,770 Jackson June 24, 1958 2,844,770 Vessem July 22, 1958 2,906,932 Fedotowsky et a1. Sept.

Abstract

894,672. Semi-conductor devices. PHILIPS ELECTRICAL INDUSTRIES Ltd. June 27, 1958, No. 20704/58. Drawings to Specification. Class 37. A wire, at least the envelope of which is aluminium, and which is coated with a layer of oxide of sufficient thickness to enable fusion of the aluminium to take place without breakage of the oxide layer, is fused to a semi-conductor material. The oxide layer should have a thickness of from 3 to 40 microns and the semiconductor material and the material inside the aluminium envelope of the wire may be germanium or silicon, and tin may be used to connect the semi-conductor device to a base-plate. The device may be a diode or a transistor and in one embodiment (Fig. 3, not shown) it may be sealed inside an evacuated casing. A device according to the invention may be constructed by degreasing an aluminium wire by washing in caustic soda solution, nitric acid and then water and then oxidizing the surface either by dipping in a solution of H3PO3, CrO3, NH4HF2, and (NH4)2HPO3 in water or by subjecting the wire to anodic treatment at 60 volts D.C. in a solution of oxalic acid in water. The end of the wire may then be cut and polished and held in contact with a silicon body by means of a graphite jig (Fig. 2, not shown), while the whole device is heated in an oven to cause fusion to occur. Copper wire or cable may then be spotwelded to the aluminium wire at a point some distance away from the semi-conductive body.

Description

Jan. ,2, 1962 Filed June 27, 1958 Fig.1
INVENTOR LUDOVICUS AUGUSTINUS LAMBERTUS ESSELING BY A,
AGEN
United States Patent are Filed June 27, 1958, Ser. No; 745,032 Claims priority, application Netherlands July 1,1957 9 Claims. (Cl. 317-234) This invention relates to semi-conductor devices, for
example transistors or crystal diodes, having a semi-con-v ductive body to which oneend of at least one electrode wire is secured by fusion.
It has previously been suggested for the body, tc gether with a wire applied thereto at one end, to be heated at a temperature such that both elements fuse together at the contact area. i 7
When it is endeavoured in this way to secure by fusion a wire of aluminum, it appears, more particularly if the semi-conductive body consists of silicon, that heating above the melting point of aluminum is necessary, so that the wire, although it is covered with a natural oxide layer, flows together into a drop or at least loses its filamentary form. Electrodes of aluminum are therefore manufactured by applying by fusion either pellets the electrodematerial, in the present case in the wire,
or thin discs of aluminum. However, it is ditficult for the resultant electrodes to be provided with supply wires,
since, as is well-known, soldering to aluminum is in practice impossible as a result of the aforementioned natural oxide layer, which spontaneously forms on aluminum clue to action of the oxygen in the air.
An object of the invention is inter alia to provide a construction in which these disadvantages do not occur,v
and also amethod by which this construction may be realized in a simple manner.
may restrict penetration of the electrode material into the Semi-conductive body in a manner known per se.-
Such a wire may be manufactured by filling an aluminum tube with the other material and subsequently reducing the cross-section of the whole by swaging or expanding. In order that the invention may be' readily'carried into effect, several embodiments will now be explained in detail, by way of example, with reference to the accompanying drawing, in which:
FIG. 1 shows diagrammatically a side-view of a diode; FIG. 2 shows a device for applying wires to semioonductive bodies by fusion. 7
FIG. 3 is a cross-sectional view of a semi-conductor device according to the invention. The diode shown in FIG. 1 comprises a thin silicon disc 1 of conductivity, to which an aluminum wire 2 is secured by fusion in an oven at a temperature preferably higher than the melting point of aluminum, for instance 8009 C. The oven temperature may however in principle be lower than the melting point of aluminum, but higher than the eutectic temperature of the silicon-aluminum mixture. The heating takes place in reducing surroundings, for example in a mixture of nitrogen and hydrogen. A small addition of hydrochloricacid gas as a flux enhances adhesion of the wire to the body. The wire is provided with a genetic oxide layer 3 which ensures that the form of the wire substantially does not change during heating and that flowing-out of the aluminum is restricted within certain limits. The strengthened oxide layer is naturally not present at the area wherethe aluminum must fuse togetherwith the silicon. [The reoxide sheath. The thickness of the wire'is not essential According to the invention, the wireof which at least t the envelope consists of aluminum, has so thick a genetic oxide layer on its cylindrical outer surface that fusion of the aluminum is possible without breakage of the oxide layer.
Said oxide layer preferably has a thickness comprised between 5 and 40 microns. Consequently, this layer is much thicker than the natural oxide layer already present on aluminm and which has a thickness'of only 0.1 to 0.2 gt. 1
An oxide layer of sufficient thickness maybe obtained in a simple manner by chemical means or by anodic'.
oxidation. a
The method according to the invention is characterized in that a wire, of which at least the envelope consists of aluminum, is provided with a genetic oxide, layer of a thickness such that fusion of the aluminum is possible without breakage of the oxide. layer, whereupon one end of this wire is secured by fusion to a semi-conductive body. It will be evident that it is also possible for short pieces to be cut from a long oxidized wire.
It is to be noted that a genetic oxidelayer is to be understood to mean a layer, the aluminum content of which substantially originates from the initial wire. The term oxide layer is to be understood to mean also layers consisting of oxide hydrates, such as the compound Al O -H O, and furthermore oxide layers strengthened by impregnation or in another way, as will be discussed more fully hereinafter.
As a rule, the'wire homogeneously consists of aluminum. However, it is possible to utilize a wire having an envelope of aluminum and a core of a different material. During fusion, the envelope and the core may fuse together. I
The core may consist, for example, of semi-conductive material, such as germanium or silicon. Its presence in to the invention and is usually from lOOmicrons to several millimetres in practice. a Y
I The, semi-conductive body is means of tin solder 4. v
The use of a'flux, such as hydrochloric-acid gas, is greatly simplified due to the presence of the oxide layer, since such fluxes usually also chemically attack the aluminum to aconsiderable extent, which phenomenon is greatly suppressed by the presence of the strengthened oxide layer. p
The aluminum wire with its strengthened. oxide layer may be manufactured in various ways. known per se, that is to say by purely chemical means or an anodic oxidation. The last-mentioned method usually gives thicker oxide layers than the first-mentioned and is therefore preferable for comparatively thick wires.
One example of each method will now be given hereinafter.
secured to a base 5 by I v I Pure aluminum wire is de'greased for half a minute in a bath-containing 15 gms. of sodium hydroxide to gms.-of water at a temperature of 20 C. After rinsing in water, any residues of this bath are neutralized in a solution of nitric acid having a specific gravity of 1.25 at room temperature for 1 minute, whereafter the wire is rinsed in water. Such removal of grease is not necessary for wire which is very clean.
Subsequently, the wire is dipped for 4 minutes in an oxidizing bath of the conventional type containing for example,
55 cos. of phosphoric acid H PO density 1.7
22 gms. of chromic acid CrO 3.3 gms. of acid ammonium fluoride NH HF 2.2 gms. of acid diammonium phosphate (NH4)2HPO3 1000 gms. of water at a temperature of 50 C. Of course also other oxidizing baths can be used.
3 The wire is then carefully rinsed and dried. The thickness of the oxide layer is from 3 to 5 microns.
Aluminum wire degreased as described in Example I is subjected at 20 C. to an anodic treatment at 60 volts (direct voltage) for one hour. The bath was a conventional one, containing 50 guts. of oxalic acid C H H 2H O per litre. Also other oxidizing baths are suitable. The thickness of the resultant oxide layer was about 40 microns.
Several such purely chemical or electro-chemical methods are known and it is not essential to the invention which method is used, provided the resultant layer has suflicient thickness and, of course, does not contain constituents detrimentally'atiecting the performance of the semi-conductor device.
From the oxidized wire obtained in accordance with Example i or II, there are cut oif pieces each having a length of mms, which in a jig of graphite are placed on the bodies of silicon (see KG. 2). The jig is constituted by two parts 11 and 12, which fit into each other. The part 12 has recesses 13, by which the semi-conductive bodies are kept in position, and perforations 14, by which the pieces of Wire 10 are centred with respect to the bodies.
After the above-described heating in an oven, the pieces of wire are found to have retained their initial form. Subsequently, the semi-conductive bodies are after-etched in the usual manner, for example with the use of hydrofluoric .acid, the strengthened oxide-layer then again having the advantage of protecting the aluminum itself against chemical attack.
It is to be noted that the pieces of Wire 10, before being applied by fusion, are preferably provided with a fiat end by polishing or filing.
The pieces of wire 10 may be connected by" spot- Welding to a piece of cop-per Wire or copper cable which may be connected by soldering to a connecting member.
During spot-welding, the strengthened oxide layer is naturally broken through, but this is not dangerous, the operation being effected at some distance from the semiconductive body.
FIG. 3 shows an example of such a'structure applied to a diode in an evacuated envelope. The envelope comprises a base with a threaded stud 31 for attachment, and a cap 32. The cap 32 contains a glass leadthrough insulator 33 containing a small metallic tube 34. Whereas the aluminum wire 10 is secured by spot-Welding to a copper Wire '36 at 35. After this wire has been passed through the tube 34, the base 30 and the cap 32 are secured together by means of flanges 37 and 38, for example by Welding. Subsequently, the envelope is fully closed due to the copper wire 36 being soldered in the tube 34.
As previously mentioned, it is alternatively possible to utilize a wire having an envelope of aluminum and a core of different material. The-latter may contain or consist of an active impurity such as a donor and/or an acceptor, but also semi-conductive material and more The silicon body 1 is soldered to the base 30,
particularly the same material as that of the body to which the wire is secured.
What is claimed is:
1. An electrode comprising a wire-like ele ent adapted for fusion at one end to a semiconductive body, the outer Wire portions consisting essentially of aluminum and containing a genetic oxide layer'having a thickness between 3 and 40 microns enabling fusion of the alu minum without destruction of the layer.
2. A semiconductor device comprising a semiconductive body, and a Wire-like element fused at one end to the semiconductive body, the outer wire portions consisting essentially of aluminum and containing a genetic aluminum oxide layer having a thickness between about 3 and 40 microns. A 3. A device as set forth in claim 2 wherein the wirelike element comprises a core of a semiconductive material, an envelope of aluminum, and a surrounding aluminum oxide coating.
4. A device as set forth in claim 2 wherein the wirelike element comprises a core of an impurity material, an envelope of aluminum, and a surrounding aluminum oxide coating.
5. A semiconductor device comprising a semiconductive silicon body, and an aluminum wire-like element fused at one end to the semiconductive body, the outer wire portions containing a genetic aluminum oxide layer having a thickness between about 5 and 40 microns.
6. A method of making a semiconductor device comprising, providing a wire whose outer portions consist essentially of aluminum, subjecting said Wire to an oxidizing treatment'to provide on the aluminum portions a genetic'oxide' layer having a thickness enabling the aluminum to be fused without desruction of the oxide layer, and using an end of the said Wire to a semiconductive body. 7. A method of making a semiconductor device comprising providing a wire whose outer portions consist essentially of aluminum, subjecting said Wire to an oxidizing treatment to provide a'genetic oxide layer having a thickness of at least about 5 microns, placing a cut end of the said wire in contact with a semiconductive body, and heating the assembly at a temperature at which I the wireend fuses to the semiconductive body.
8. A method of making a semiconductor device comprising providing an aluminum wire, subjecting said Wire to an oxidiring'treatment to provide thereon a genetic aluminum oxide layer having a thickness between 3 and 40 microns, placing a cut end of the wire in contact with a silicon semiconductive body, and heating the assembly in an oven at a temperature above the eutectic temperature of the silicon-aluminum alloy and at which the 2,840,770 Jackson June 24, 1958 2,844,770 Vessem July 22, 1958 2,906,932 Fedotowsky et a1. Sept. 29, 1959 UNITED STATES PATENT OFFICE e CERTIFICATE OF CORRECTION January 2 1962 Patent Nm-O OESJl Ludcvicus Augustinus Lambertus Eseeling s in the above numbered pat- It is hereby certified that error appear tters Patent should read as ent requiring correction and that the said Le corrected below.
Column 2,, line 17 after of insert n-type line 65,, for H PQ read B 190 line 68 for NH )2HP0 read QNH D HPO column 3,, line 9 for "*C H H .2H 0".
reed C204H2.2H20
Signed and sealed this 1st day of May 1962c (SEAL) Attest:
DAVID L. LADD Commissioner of Patents ERNEST W0 SWIDER Attesting Officer

Claims (1)

  1. 2. A SEMICONDUCTOR DEVICE COMPRISING A SEMICONDUCTIVE BODY, AND A WIRE-LIKE ELEMENT FUSED AT ONE END TO THE SEMICONDUCTIVE BODY, THE OUTER WIRE PORTIONS CONSISTING ESSENTIALLY OF ALUMINUM AND CONTAINING A GENETIC ALUMINUM OXIDE LAYER HAVING A THICKNESS BETWEEN ABOUT 3 TO 40 MICRONS.
US745032A 1957-07-01 1958-06-27 Semi-conductive electrode system Expired - Lifetime US3015761A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036485A (en) * 1969-08-11 1977-07-19 Licentia Patent-Verwaltungs-G.M.B.H. Jig

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1178520B (en) * 1961-08-24 1964-09-24 Philips Patentverwaltung Alloy process for the manufacture of semiconductor devices

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US2840770A (en) * 1955-03-14 1958-06-24 Texas Instruments Inc Semiconductor device and method of manufacture
US2844770A (en) * 1954-05-18 1958-07-22 Philips Corp Semi-conductive device and method of producing same
US2906932A (en) * 1955-06-13 1959-09-29 Sprague Electric Co Silicon junction diode

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NL175652B (en) * 1952-02-07 Krings Josef SLIDING SHOE FOR TENSIONING DEVICE OF A HANDLE CONSTRUCTION DEVICE.

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US2844770A (en) * 1954-05-18 1958-07-22 Philips Corp Semi-conductive device and method of producing same
US2840770A (en) * 1955-03-14 1958-06-24 Texas Instruments Inc Semiconductor device and method of manufacture
US2906932A (en) * 1955-06-13 1959-09-29 Sprague Electric Co Silicon junction diode

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036485A (en) * 1969-08-11 1977-07-19 Licentia Patent-Verwaltungs-G.M.B.H. Jig

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