US3182845A

US3182845A - Housing for an electronic device

Info

Publication number: US3182845A
Authority: US
Publication date: 1965-05-11
Anticipated expiration: 1982-05-11

Description

May 11, 1965 HOUSING FOR AN ELECTRONIC DEV Filed Aug. 1'7, 1959 R. D. CULBERTSON ETAL ICE fig. 1

INVENTORS. ROBERT 0. CULBERTSQN RUSSELL C. McRAE BYHARVE Y C. WARNER my. ATTORNEYS tube;

United States Patent On ice 3,182,84 Patented May 1 1,196

3,182,845 HOUSHVG FOR AN ELECTRONIC DEVICE Robert D. Culbertson, San Jose, Russell C. MclRae, Santa Clara, and Harvey C. Warner, Colma, Calif, assignors to Eitel-McCullough, Inc, San Bruno, Califl, a corpuration of California Filed Aug. 17, 1959, Ser. No. 834,219 8 Claims. (Cl. 2202.3)

This invention relates to anelectron tube and more particularly to an electron tube having'a pressure seal and to a method of and a means for making such a seal. The term pressure seal is defined for use hereinjas a permanent. vacuum-tight seal obtained by the application 'of pressure at temperatures below the melting point of any of the materials in the seal.

With the introduction of high alumina ceramic electron tubes, various types of pressure seals were developed to seal ceramic to ceramic or ceramic to metal. None of these types of seals are effective in sealing two parts of a miniature electron tube, especially when the tube dimensions are in the order of one-half inch long and one-quarter inch in diameter. In pressuresealing a miniature diode that requires at least three electrical leads and is limited to two ceramic ring insulators, the electrical lead, which is in the form of a ring and positioned between the two ceramics, is required to be 'made. of hard metal such as Kovar so that it will not deform under sealing pressure destroying the metal to ceramic bond, as well as making it difiicultto obtain accurate electrical spacing. The art of pressure welding two pieces of metal teaches that hard metals require larger pressures for pressure welding'than softer metals. The pressure required to weld Kovar is too high and not practical in the fabrication of a miniature In this application Kovar refers to metal alloys comprising primarily i-ron, nickel and cobalt with some manganese and having a coeffic-ient of thermal expansion ap proximately 5x10 per degree ceritigrade.

It is an object of the present invention to provide an electron tube with a pressure seal between two pieces of hard metals. I I

It is another object of the present invention toprovide a pressure sealing method between hard metal surfaces which do not require optical fiat joining surfaces."

It is yet another object of the present invention to provide a pressure seal, a method of and a means for making such seal between hard metal rings in an electron tube.

In one embodimentthe invention involves making hard metal pressure seals for electron tubesbyplating the hard metal sealing rings with a soft ductile metal. A soft ductile metal sealing gasket is placed between the two soft metal clad surfaces on each of the hard metal rings.

Force is applied to-the hard metal rings until the gasket yields and deforms- In so doing the basket adheres to the plated surfaces.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the invention. It is to be understood that the invention is not limited to the disclosed species, as variant embodiments thereof are contemplated and may be adopted within the scope of the claims.

Referring to the drawings: t

FIGURE 1 is a sectional elevation of a typical die press fixture, through which pressure is applied to the sealing rim of an electron tube.

FIGURE 2 is an enlarged view of the sealing rim of an electron tube before pressure is applied.

FIGURE 3 is a sectional elevation of the sealed electron tube.

" Referring now to the drawings and to FIGURE 1 particular, there is shown an electron tube in two sectio which are to be sealed together. The two sections a cathode section 12 and an anode section 14. The cathot section 12 is suspended within an axial well 16 form in a ram 18. The ram 18 and a die 20 form a die pre fixture. The cathode section is held by a wire 22 Whit is suspended through an aperture 24in the ram 18. T end of the wire 22 within the well 16 is fixed to a sealii means 26 which is a metallic plate joined to a ceran'. cylinder 28 ofthe cathode section 12 by means of a co ventional ceramic-to-metal bond. Wire 22 may be fix to sealing means 26 with soft solder. The wire is th passed through aperture 24 and the cathode section drawn up tight against the ram 18. The wires free e1 protruding from the ram is bent to hold the catho section in place. Onthe other end of the ceramic c1 inder 28 is bonded a terminal sealing ring 30 preferab made of Kovar. The terminal sealing ring 30 is plat with a soft, highly ductile metal 32 such as oxygen-frc high conductivity copper, which in this embodiment plated on both sides of the Kovar, as shown, althou; it is actually necessary to plate only the side of the Kov to be pressure sealed. The plating is preferably betwet .001 and .002 inch thick and the ring 30 is about .0 inch thick. A cathode 33 with an emitting surface 1 coplanar with the terminal ring 30- is mounted theret The anode section 14 is similar to the cathode SCCtll in that sealing means 26' formed into a cup-shaped met section is scaled to a similar ceramic cylinder 28 a1 a terminal ring 35) is joined to the other end of the c ramic cylinder 28' by means of a conventional cer-arni to-metal bond. Ring 30 is also made of a hard met such as Kovar. The sealing means 26' is the anode wi a face 35 coplanar with terminal sealing ring 30'. Sin

larly to ring 30, the ring 30' is also copper plated as re resented by plated layers 32'. The anode section 14 f into the die 20 with the ceramic section 28' disposed wit in a bore 34 of the die'Ztl and the terminal sealing ri1 30' hearing on a shoulder formed by a larger bore 1 into which is disposed the ram 18. i

The pressure seal is formed between the two rings 2 and 30' byfirst cleaning the sealing surfaces which a the copper plated

surfaces

32 and 32. which face eat other and cleaning a soft, highly ductile metallic sealii gasket 38 made of the same material as the plated st faces 32 and 32, and in this embodiment being oxyg free, high conductivity copper, all being cleaned with standard acid process. The two

sections

12 and 14 a1 the copper gasket 38 are afterward wet-hydrogen fired approximately 800 C. to. anneal, degas and rem-o carbon residue. The two

sections

12 and 14 are assemblt to the ram 18 and die 20, as shown in FIGURE 1, wi hard metal washers 40 and.40 disposed between :1 terminal sealing ring 30 and the ram 18 and between t terminal sealing ring 30' and the die 20, clearly shown FIGURE 2. The hard metal washers 40 and 40' a preferably made of Kovar and are used to prevent tf copper plating on the rings 30 and30 adjacent the ra and the die from adhering thereto. The sealing gask 38 is placed on the plated layer 32'. Also on the plat layer 32' is placed a hard metal spacer washer 42, al preferably made of Kovar. The washer 42 is thinn than the sealing gaskets 38, and it is used to. limit tI space between the anode face 35 and the emitting surfa 34. The ram 18 and die 20, along with the tube a enclosed in a vacuum envelope (not shown) and vacuu fired between 600 and 700 C. The vacuum pressure reduced to 1X10 mm. of mercury at this temperatui An electrical resistance coil 50 may be used for t vacuum firing process. The coil 56 is powered by a su power supply 52 and controlled by a variable resistor The tube is processed in a standard manner during vacuum firing. .fter vacuum firing and still maintaining a high vac- 1, the ram 18 is then forcedagainst the die 20 by a s 56. A pressure of about 25,000 p.s.i. on the sealing :et38 is applied for 2 to minutes at a temperature s-bout 500600 C. The pressure, temperature, time tbination can be varied somewhat as long as the temtture is below the melting temperature of copper and ve the annealing temperature; the lower the temperathe greater the pressure and time requirement and versa. The sealing gasket 38 is extruded under this :sure causing it-to adhere to the layers 32 and 32' a like metalto like metal (copper to copper) seal is le. The spacer washer 42 limits the spacing between

rings

30 and 30 and also prevents the sealing gasket nextruding into the tube and making an electrical ."t.. tlthough the seal isa copper-tc-copper seal, rings 30 30' made entirely of copper are not practical since per will extrude and deform during the pressing opera- I This deformation of the copper would destroy the sum tight bond with the ceramic. A ring 30. and 30 1e of hard metal such as Kovar does not deform in ring the seal and therefore retains the vacuum tight d with the ceramic. Further, if copper were used, spacer washer- 4 2 Would imbed itself in the terminal ing rings and no longer serves the purpose of fixing cathode, anode spacing. v =IGURE 3 shows the sealed electron tube. The tube hown in cross-section in order to illustrate What haps to the copper gasket 38 after pressure is applied. a copper flows under pressure and is prevented from ling into thevacuum envelope by the spacer Washer The copper in thus flowing adheres to the adjacent per plating strips 32 and 32. Vhat is claimed is:

. An electron tube comprising a first vacuum envelope :ion'and asecond vacuum envelope section sealed to- 1er bya pressure weldseal, said pressure weld seal iprising a first hard metal sealing ring forming part said first section and a second hard met-a1 sealing ring ning partof said second section, soft ductile metal ing on said first and second rings, and a soft ductile ling gasket between said sealing rings bonded to said :ings and forming a vacuum tight seal between said ling rings, and said sealing gasket and said metal plat-- being the same metal.

1. An electron tube as claimed in claim 1 wherein said d metal'is Kovar, and said soft ductile metal is copper. An electron tube comprising a first vacuum. envelope tion and a second vacuum envelope section sealed ether by a pressure seal, said pressure seal'comprising rst hard metal sealing ring bonded to said-first section 1 a second hard metal sealing ring bonded to said second tion, said sealing rings protruding outwardly from 1 envelope sections forming rims, soft ductile metal ting on said sealing rings, a hard metal spacer ring gosed between said first and second plated hard metal ling rings, and a soit ductile meatl sealing gasket dis- .ed exterior of said hard metal spacer ring and exied to adhere to said plated'sealing rings forming a vacuum tight seal, said metal spacer ring being of a metal substantially as hard as said metal in said sealing rings, said sealing gasket and said metal plating being of the same soft metal.

4. An electron tube as claimed in claim 3 wherein said hard metal is Kovar, -=and said soft metal is copper.

5. An electron tube having two envelope sections each comprising a ceramic ring and a metal sealing ring bonded thereto, said metal sealing rings being bonded together by a pressure weld seal, said pressure weld seal comprising annular rims on said metal rings projecting outwardly beyond said ceramic rings, said rims being made of hard metal coated on their adj-acent sides with a relatively soft metal, a sealing gasket between said rims, a non-melt pressure Weld bonding said gasket to said coatings and forming a vacuum tight seal between said rims, and said sealing gas metal.

6. An electron tube as claimed in claim 5 in which a spacer ring is positioned between said sealing rings, said spacer ring being made of material which is harder than said. sealing gasket.

7. An electron tube comprising a first vacuum envelope section and a second vacuum envelope section sealed together by a pressure Weld seal, an electrode supported by each of said sections, said pressure Weld seal comprising a first metal sealing ring forming part of said first section and a second metal sealing ring forming part of said second section, a metal sealing gasket between said sealing rings, a non-melt pressure weld bonding said gasket to said rings to form a vacuum tight seal between said sealing rings, and a spacer ring between said sealing rings, said spacer ring being made of a relatively hard material compared to said sealing gasket.

8. A housing for an electronicdevice comprising a first envelope section and a second envelope secti-onsealed together by a pressure weld seal, said pressure Weld seal comprising a first hard metal sealingfiange forming part of said first section and a second hard metal sealing flange forming part of said second section, a soft ductile metal plating on said first .and second flanges, and a soft ductile sealing gasket between said sealingflanges bonded to said platings and forming an hermetic seal between said sealing flanges, and said sealing gasket and said metal plating being the same metal.

Reierences Cited by the Examiner I UNITED STATES PATENTS THERON E. CONDON, Primary Examiner.

FRANKLIN T. GARRETT, EARLE I. DRUMMOND,

Examiners.

Claims

8. A HOUSING FOR AN ELECTRONIC DEVICE COMPRISING A FIRST ENVELOPE SECTION AND A SECOND ENVELOPE SECTION SEALED TOGETHER BY A PRESSURE WELD SEAL, SAID PRESSURE WELD SEAL COMPRISING A FIRST HARD METAL SEALING FLANGE FORMING PART OF SAID FIRST SECTION AND A SECOND HARD METAL SEALING FLANGE FORMING PART OF SAID SECOND HARD METAL SEALING FLANGE FORMING PART OF SAID SECOND SECTION, A SOFT DUCTILE METAL PLATINGS AND FORMING AND HERMETIC SEAL BETWEEN SAID SEALING FLANGES, AND SAID SEALING GASKET AND SAID METAL PLATING BEING THE SAME METAL.