US3617988A

US3617988A - Insulative electrical terminal

Info

Publication number: US3617988A
Application number: US848985A
Authority: US
Inventors: Curtis Eugene Ward
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-08-11
Filing date: 1969-08-11
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02

Abstract

An insulative electrical terminal is disclosed. The terminal includes a ceramic body metallized on one end which is brazed to a terminal post structure to which an electrical circuit component is to be soldered. The other end of the ceramic insulator body is affixed to a metallic chassis via a thermally conductive adhesive which preferably forms a fillet between the insulator body and a pocket formed in the metallic chassis member.

Description

United States Patent Curtis Eugene Ward 11486 Miller Ave., Los Altos, Calif. 94022 [21] Appl. No. 848,985

[22] Filed Aug. 11, 1969 [45] Patented Nov. 2,1971

[72 Inventor [S4] INSULATlVE ELECTRICAL TERMINAL 4 Claims, 2 Drawing Figs.

[52] U.S. Cl 339/112, 174/166, 339/1 19, 339/275 [51] 1nt.Cl H01r 9/06 [50] Field of Search 339/119, 112, 93 C, 275,278,198.3,218;174/153,166.l

[5 6] References Cited UNITED STATES PATENTS 2,726,280 12/1955 Demurjian 174/166 2,823,251 2/1958 Clark 174/153 2,918,521 12/1959 Abrams. 174/166 X 3,261,396 7/1966 Trunk. 165/80 2,836,807 5/1958 Goodfellow et al 339/l98.3

Primary Examiner- Richard E. Moore Attorneys-Stanley 2. Cole and Gerald L. Moore ABSTRACT: An insulative electrical terminal is disclosed. The terminal includes a ceramic body metallized on one end which is brazed to a terminal post structure to which an electrical circuit component is to be soldered. The other end of the ceramic insulator body is afflxed to a metallic chassis via a thermally conductive adhesive which preferably forms a fillet between the insulator body and a pocket formed in the metallic chassis member.

INVENTOR.

CURHS E] WARD BY ATTORNEY I l INSULATIVE ELECTRICAL TERMINAL DESCRIPTION OF THE PRIOR ART Heretofore, electrically insulative terminals have been employed wherein a metallic terminal post structure, to which the electrical component is to be soldered, is affixed to one end of a hollow ceramic body by crimping. A metallic stud is crimped to the other end of the ceramic body. The stud screws into a threaded bore in a metallic chassis from which the component is to be supported. Some of the problems with this terminal are that the crimped joints made to the ceramic insulator body tend to loosen as the terminal is putthrough atypical thermal cycle, such as that encountered during soldering of the electrical component to the terminal, moreover, such crimped joints have a relatively poor thermal conductivity due to the very small thermal cross section of their line and point contacts. In addition, the hollow central portion of the ceramic insulator body provides an uninspectable electrical flashover or leakage path inside the insulator. The central bore is required in order to make the crimped joint between the solder terminal and the insulator body.

In another prior art electrically insulative terminal, the metallic terminal post structure, to which the electrical component is to be soldered, is molded into one end of a solid plastic body such as Alkyd, phenolics and the like. The problem with the molded plastic body is that the plastic material has a relatively poor thermal conductivity, as of 0.00l cal. per gram per centimeter per degree Centigrade per second. In a typical example, such an insulated terminal, in normal operation, can result in a temperature drop across the insulator of approximately 60 C. This is a relatively high thermal gradient to exist across the terminal and it is desired to produce an electrically insulative terminal which has substantially improved thermal conductivity to the chassis.

SUMMARY OF THE PRESENT INVENTION The principal object of the present invention is the provision of an improved electrically insulative terminal for electrical circuit components.

One feature of the present invention is the provision of an electrically insulative terminal having a ceramic insulator body with a metallic terminal post structure to which the electrical component is to be soldered being brazed to the insulator body by means of a relatively thermal-conductive metalto-ceramic fused metallic joint, whereby the thermal conduc tivity of the insulative terminal is substantially improved.

Another feature of the present invention is the same as the preceding feature wherein the ceramic insulator body is joined to a metallic chassis member by means of a thermally conductive adhesive.

Another feature of the present invention is the same as the preceding feature wherein the end of the insulator body which is joined to the metallic chassis member is disposed within a pocket in the chassis member with a thermally conductive adhesive forming a fillet and filling the space within the pocket between the inside wall of the pocket and the end of the insulator body.

Another feature of the present invention is the same as any one or more of the preceding features wherein the ceramic insulator body is made of a material selected from the group consisting of alumina and beryllia.

Other features and advantages of the present invention become apparent upon perusal of the following specification taken in connection with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly broken away and partly in section of a prior art insulative electrical terminal as mounted to a chassis member, and

FIG. 2 is a view similar to that of FIG. 1 depicting the insulative electrical terminal of the present invention.

2 DESCRIPTION OF THE PREFERRED EMBODIMENTS per. degree Centigrade per second. A turret-type terminal post structure 4, as of brass, is affixed to one end of the insulator 3 by being molded into the end of the insulator body 3. A metallic stud 5 is afiixed to the other end of the insulator body 3 by being molded into the other end of the insulator body 3. The stud 5 includes a threaded extension 6 threadably mating with the internal threads of a bore 7 in the chassis plate 2.

In a typical example of the prior art insulated terminal I,-the insulator body 3 has a length of 0.10 inch, and a diameter of 0.14 inch. The typical temperature drop across the insulator body, for the aforecited dimensions and assuming 0.l watt input at the turret terminal 4 is approximately 60 C. Thus, a temperature rise of 60 C. is obtained only due to the poor thermal conductivity of the insulator body and this does not take into account the relatively poor thermal conductivity obtained through the joints to the insulator body 3.

Referring now to FIG. 2, there is shown an insulative electrical terminal 11 incorporating features of the present invention. Insulated terminal 11 includes a solid ceramic body member 12 to which metallic members maybe brazed. A suitable ceramic material for insulator 12 includes ceramics, such as fosterite, steatite, alumina and beryllia. Fosterite and steatite have thermal conductivities of 0.008 and 0.006 cal.

per gram per centimeter per degree Centigrade per second,

the end thereof to receive the terminal structure 13. A suitable metallizing layer is formed by the conventional molybdenum manganese metallizing technique. The terminal post structure 13 is then brazed by means of a conventional silver/copper eutectic brazing alloy material to the metallized layer, thereby forming a metal-to-ceramic joint 14 of fused metal having relatively high thermal conductivity and large thermal cross section. A circuit component 15 such as a diode, resistor, inductor, etc., has a lead thereof 16 soldered to terminal post structure 13.

The other end of the insulator body 12 is disposed in a cylindrical recess or pocket 17 in the chassis plate 2. A fillet of thermally conductive adhesive such as Delta Bond 152" adhesive obtained from Wakefield Engineering of Wakefield, Mass, fills the space between the end of the insulator body 12 and the inside wall of the pocket 17 to provide a relatively highly thermally conductive joint between the insulator body 12 and the chassis plate 2. The aforementioned conductive adhesive has a relatively high coefficient of thermal conductivity, as of 0.002.

Although the preferred embodiment has the insulator body disposed within a recess or pocket 17 in the chassis plate 2, this is not a requirement and as an alternative the adhesive may be disposed between the surface of the chassis plate 2 and the end of the insulator body 12. However, the recess 17 has the additional advantage of providing a locating hole for location of the various terminal insulator members 11.

The advantage of the insulated terminal II as compared to the prior art is that the thermal conductivity through the terminal is substantially improved compared to the prior art,

thereby facilitating thermal conduction cooling of the devices connected to the insulated terminal. More particularly, for an insulator body 12 of the same dimensions as that previously cited for insulator 3, a temperature drop across insulator body 12 for 0.1 watt applied to the terminal 13 is 7.6 C. for fosterite, 10.1 C. for steatite, 1.2 C. for alumina, and 03 C. for beryllia, whereas 60 C. was obtained for Alkyd of the prior art.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

lclaim:

l. in an electrical insulative terminal for connecting circuit components to a metallic chassis, means forming a ceramic insulator body, means forming a metallic terminal post structure afflxed to a first end of said insulator body for connection to a circuit component to be insulatively supported from the metallic chassis which is to be disposed at the second end of said insulator body, THE IMPROVEMENT COMPRISING, a metal-to-ceramic fused metallic joint disposed in between the first end of said ceramic body and said terminal post for bonding said metallic terminal post to said ceramic insulator body, whereby a relatively high thermal conductivity path is provided from said terminal post structure to the metallic chassis through said metal-to-ceramic metallic joint and said insulator body and further including a metallic chassis from which the electrical component is to be supported via the intermediary of said insulator body and terminal post, said chassis including a recessed pocket, said second end of said insulator body being disposed in said pocket, and means for supporting said insulator body within said pocket in thermally conductive relationship with the walls of said pocket.

2. The apparatus of claim 1 wherein said ceramic insulator body is made of a material selected from the group consisting of fosterite, steatite, alumina, and beryllia.

3. The apparatus of claim 1 wherein said ceramic insulator body is made of a material selected from the group consisting of alumina and beryllia.

4. The apparatus of claim 1 wherein said means for supporting said insulator body comprises a thermally conductive adhesive filling the space between the walls of said pocket and the second end of said insulator body.

Claims

1. In an electrical insulative terminal for connecting circuit components to a metallic chassis, means forming a ceramic insulator body, means forming a metallic terminal post structure affixed to a first end of said insulator body for connection to a circuit component to be insulatively supported from the metallic chassis which is to be disposed at the second end of said insulator body, THE IMPROVEMENT COMPRISING, a metal-to-ceramic fused metallic joint disposed in between the first end of said ceramic body and said terminal post for bonding said metallic terminal post to said ceramic insulator body, whereby a relatively high thermal conductivity path is provided from said terminal post structure to the metallic chassis through said metal-to-ceramic metallic joint and said insulator body and further including a metallic chassis from which the electrical component is to be supported via the intermediary of said insulator body and terminal post, said chassis including a recessed pocket, said second end of said insulator body being disposed in said pocket, and means for supporting said insulator body within said pocket in thermally conductive relationship with the walls of said pocket.