DE2036201A1 - Hermetically sealed connection - Google Patents

Description

fnwäno ng. A. Qr _{0n 9ckor}

P 3341 21. Wed 1970

The Bunker-Ramo Corporation

Oakbrook North.

Oak Brook, Illinois . United States

Hermetically sealed connection

The invention relates to hermetically sealed electrical connections light weight, insbespndere for use in environments with very low and very high temperatures in the aerospace industry, where certain use military standards se must be sufficient for those *. "

Hermetically sealed electrical connections generally employ two types of sealed connections between metal and Glass, namely the integral connection and the press-fit seal. In the integral connection, the metal and glass parts have the same coefficients of thermal expansion, so that the occurrence of excessive and undesirable tension in the contraction and expansion of metal and glass Temperature changes avoided 1st. Such an arrangement requires the formation of a chemical bond between the glass and the metal in order to create the seal,

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In the case of a press fit seal, the seal between the glass and the metal is brought about by compressive forces. Appropriate there is an additional chemical bond, which however with » this type of seal is not absolutely necessary. The pressure forces are created by an outer metal frame a relatively high coefficient of thermal expansion exerted on an • inner glass part. After heating the glass and the setting to a fusing temperature, the setting contracts during the subsequent cooling and practices dab'si Pressure forces on the glass part.

At this point it should be noted that glass is very pressure-resistant and only very slightly tensile-resistant, so that a press-fit seal is only possible with a metal part arranged around the outside of a glass part ₆ whereas a material-jointed seal with both an externally and internally arranged metal part, for example also with a metal contact enclosed by a glass body, can be produced. Electrical connections mostly use both types of sealing arrangements, since all connections inevitably have an outer part, that is to say a socket or a housing and at least one inner part made of metal, namely in one

^ Contacts or bushings arranged in insulating glass

^ stanchions included.

Currently in use hermetically sealed electrical connections use as the material for the socket 1m generally a low carbon steel, stainless steel or other alloys which have low coefficients of thermal expansion compared to other metals. The interior glass insulator usually has an even lower coefficient of thermal expansion with values in the range of 9, 10 "* / deg. Because the glass used \ species low coefficient of expansion have" are the works

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Materials for the connection contacts are also limited to special alloys with low expansion coefficients ^, which ensure a material connection between the contacts and the glass. The most common of these Alloys are iron-hickel alloys, albeit also . Tungsten and molybdenum can be used as material for the contacts. .

For the above materials prepared terminals have -genügende mechanical strength to accommodate the _like under thermal shock conditions occurring voltages. They are, however, considerably heavier than the connections disclosed herein, since the density of iron and steel alloys averages 8 g / cm ³ compared to 2.7 g / cm ³ for aluminum Alloys with low expansion, such as were previously used for contacts, were known hermetically sealed connections also characterized by high contact resistance and thus by relatively low conductivity of contacts is generally used, an electrical conductivity value of 4S IACS (International Annealed Copper * | Standard), generally compared to pure copper, which has a conductivity value of 101S IACS.

Attempts have been made in the production of Hermetically sealed. Connections Use aluminum sockets. Applicant 1st. U.S. Pat. No. 3,371,413 an aluminum frame in connection with one with the frame of a glass body materially connected steel ring reveals · The steel ring enclosing the glass is thereby together

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with the glass pressed into the aluminum surround, so that a mechanical seal is created between the steel and the aluminum formed 1st. Such an arrangement brings the advantage of the light weight of aluminum, the mechanical one However, sealing between the metals of the ring and the socket is not as reliable as one by fusion manufactured. In addition, this type of press-fit seal is rather difficult to manufacture in large quantities because extremely tight tolerances are maintained have to.

Further attempts to use aluminum as the material for the socket connection have been simply to use an aluminum socket along with the well-known low thermal expansion glasses and alloys for the contacts. Although this results in the advantage of the low weight of aluminum, because of the essential differences in the internal expansion of glass and aluminum, the glass bodies mounted in such aluminum mounts with a small expansion subject the sealing interfaces and the aluminum mount itself to very high stresses. The coefficient of thermal expansion for aluminum coatings is generally in the range of 25.10 / degree. In addition HSGT the melting point of aluminum, which is in most aluminum alloys less than 650 ⁰ C for most types of glass melting or pour point over. Finally, the contacts made from low expansion alloys have poor electrical conductivity as noted above.

In retrospect, the greatest difficulty in designing a hermetically sealed connection with an aluminum enclosure was the adverse effects of aluminum's high coefficient of thermal expansion

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high compressive force can be achieved through the aluminum on the inner glass body when cooling the connection after firing and sealing, but at the same time a correspondingly high tensile force is exerted on the socket. The tensile force creates tensions in the frame that sometimes exceed the tensile strength of aluminum. If this occurs, this results in a plastic deformation and expansion of the diameter of the inner wall of the frame, and consequently a reduction in the compressive forces exerted on the glass body to a value proportional to the tensile strength of the aluminum. In the event of renewed heating, as can occur during use, | the seal expands elastically, relieving the tension. At sufficiently high temperatures, the compressive force exerted by the frame on the glass body is then zero and with further heating the glass comes under tensile stress, i.e. in a state in which - as stated above - it is very weak. The thermal shock limit of the connection is reached when it is destroyed by breaking or detaching the glass body from the socket. For this reason, connections provided with aluminum mounts could not be used ^{at operating temperatures of more than approximately 100 ° C. up to now.}

It should also be noted that aluminum alloys initially. , In machining and heat treatment processes are hardened "and that most aluminum alloys reduce their original hardness as well as their tensile strength suffer if they are used to create the hermetic seal of the socket be subjected to necessary heating. The heat treatment to produce the hermetic seal acts as an annealing process and as such leads to a softening of the aluminum Version. The aluminum frames that are stress-relieved in this'.! are therefore able to absorb even less tensile forces which are exerted by the glass bodies inserted in them.

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In contrast, the invention provides a hermetically sealed electrical connection, v / hich its hermeticity over einon temperature range of about -55 ⁰ C to little * - least + 225 ⁰ C maintains and a hollow metal casing having a through passing aperture, some with their Seitonwandungen glass insulator melted therein tightly and under compressive stress, and has at least one electrical contact or metal part that is melted into the insulator and penetrates it, wherein the contact or the metal part consists of a metal 1 having a coefficient of thermal expansion matched to that of the insulator manufactured and held only by this insulator, the glass of which has a melting point below that of the metal frame, the metal of which has a greater üä'rnieausdGhnung coefficient than the glass and, in the stress-relieved state, has such a degree of strength that the glass insulator melts into the frame with connect 1st by cooling to -55 ⁰ C possible without the metal frame to give tensile stresses which exceed the tensile strength in entspannungsgeglUhten state.

The hermetically sealed connection according to the invention is lightweight, has has a high electrical conductivity and withstands low and high operating temperatures, as required by individual USA military standards, without loss of tightness. These Properties can be achieved in that the outer frame is made of a light aluminum alloy, the is characterized by high tensile strength in the stress-relieved condition and has a coefficient of thermal expansion that is greater than that of the glass, so that when it cools down Pressure forces are exerted on this, but not by so much greater than that of the glass that the metal of the frame would be permanently stretched or deformed and thus the connection when it occurs such high temperatures in operation would make susceptible to damage or destruction.

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BATH ORIGINAL

Further objects, features and advantages of the invention emerge from the following description of the embodiment. play based on the drawing «In this 1st:

Flg. 1 a sectional view of a temperature insensitivity

Small, hermetically sealed connection of the structure according to the invention and ■

F1g. FIG. 2 shows a sectional view of the prefabricated glass insulator used in the production of the connection according to FIG. 1, i

The In Flg. 1 shown embodiment of a connection 10 according to the invention has a generally designated 12 outer housing or a socket, which in general with a Mounting flange 14 and an actual socket or Socket 16 is formed for receiving a matching plug or mating plug-in part. In practice, that can Socket setting IC have different types of guide grooves IR, annular grooves 20 and notches 22. However, these are not part of it the invention.

The socket 12, however, has a fastening flange 14 through setting Mittelborhung 24, which expires in the version 16 and the inclusion of a glass insulator 26 is used. This in turn carries at least one metal bushing or a metal one Contact 28, each of which has a terminal part 30 protruding from the outside of the connection and an inside of the socket part 16 arranged pin 32 has. The glass insulator 26 is of course held immovably within the bore 24 and is hermetically sealed by being connected to the inner wall of the bore 24 and is fused to the contact or contacts 28

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The mount 12 is made of a light aluminum alloy with a relatively high tensile strength, for example 1,000 kg / cm ² , but preferably about ^{1,400 kg / cm 2} or above in a relaxed state. The thermal coefficient of the alloy is considerably higher than that of the glass insulator 26, but only within certain limits, generally not exceeding that of the glass by a factor of 1.5.

Excellent results are obtained using a Glass with a thermal expansion coefficient of 17.10 "7 degrees and an aluminum alloy with a coefficient of thermal expansion of about 23.10 / deg. One that has this property Metal is made by the Aluminum Association, New York, and the US Standards Institute under the name Aluminum 5083 classified material. The exact description of this Alloy can be found in USAS Dokoment H 35.1-1967, aluminum 5083 is an aluminum alloy with a coefficient of thermal expansion of 23.4.10 / deg.

tem condition with a tensile strength of 1,400 kp / cn at room temperature. The significance of this value results from a comparison with the tensile strength of about 530 kp / cn ^{2 of} the aluminum alloy 6061, which is commonly used for industrial purposes.

Aluminum 5083 is listed here as a suitable material for the socket 12 of the connection according to the invention because of its desirable properties. These properties are the favorable tensile strength, the satisfactory coefficient of thermal expansion and low weight. However, there are also others, the same or metals having similar properties are suitable for use in accordance with the invention, and even aluminum alloys with less than optimal properties, for example aluminum

6056, which has a tensile strength of 1,470 kgf / cm and a coefficient of thermal expansion of 26.10 "/ degree or aluminum 5086, which has a tensile strength of 1 070 kp / cm and a thermal expansion ·

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BATH

Coefficients of 23.9.10 / degree aufv / e1st, v / er are considered suitable for certain purposes.

By using very conductive metal, for example Copper, made contacts 28 has the connection according to the invention, compared with known hermetically tight connections a considerably increased current carrying capacity, since, as stated above, copper is a conductivity 101% IACS, but the iron-nickel alloy only has a conductivity of 4 &. Also has copper a coefficient of thermal expansion of 17.10 "/ grd, 'which is I is considerably higher than that of the iron-nickel alloys.

To create a material seal between the contacts 28 and the glass insulator 26 and a press fit seal between the insulator and the socket 12 at a temperature below the melting point of the metal of the socket, the insulator is made of a type of glass that is 1m high compared to other glass , the coefficient of linear expansion closely matched to the copper contacts and a relatively low flow temperature. One glass with these properties is that manufactured by Ferro Corporation, Cleveland, under the designation AL-19, albeit different Glass types with the same or similar properties can be used. The glass AL-19 has a coefficient of thermal expansion of 17.10 ygrd, i.e. the same as copper, and about two thirds of that of aluminum 5083, which is 23.4.10 ygrd. Further, the 1st processing or flow temperature of the glass type AL-19 about 540 ⁰ C which is below the lying at 555 ⁰ C melting point of aluminum 5083rd

The glass insulator 26 is preferably a one-piece prefabricated part that is attached to a for insertion into the bore 24 of the socket and for receiving the

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Contacts 28 is molded to match size and shape. This is done, for example, by grinding the glass material into jamJ) and introducing the dust into a mold (not shown) for pressing and melting into a one-piece blank corresponding to the representation 1n F1g. 2. The blank has broken or beveled outer edges 34 and countersunk Bores 36 for receiving the contacts 28. The beveled Edges 34 and countersunk bores 36 favor the formation of smooth upper transitions under uniform tension between the contacts 28 and the glass and between the socket 12 and the glass during heating or baking to produce the seal. This effect can be seen in the uniform cross section and the rounded corners of the insulating body 26 in FIG countersunk holes, the glass tends to form irregular tension bulges and depressions when it is burned in »

The prefabricated glass insulator 26 is in the bore 24 of Socket 12 inserted and aligned, then in a burn-in or melt-down process in which the glass is up is heated to its flow temperature, the hermetic seals between the metal of the contact and the Glass and between the metal of the frame and the glass. »At the temperature that occurs, the glass softened to such an extent that it is sufficiently fluid to enter into a bond with the contacts (within the socket.

On cooling, the connector, the version Dar difference dsr expansion coefficient of the glass and pulls together on the glass insulator, since the metal of the frame with 23,4.10 "/ deg a larger expansion coefficient than the glass with 17.10 / deg, as stated above. However, according to the invention, the metal of the socket is not as large as in the case of known connections, which types of glass with low thermal expansion of

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Use 9.10 "/ grd in aluminum surround. Thus, the tensile stresses caused by the insulating glass body 26 in the socket 12 during the connection according to the invention much less than with known connections with aluminum sockets. The lower tensile stress brings about the connection according to the invention together with the high tensile strength the material of the socket reliable hermetic. Seals because of the tendency of the socket to plastic deformation significantly reduced 1st. As a result, the thermal break limit of the insulating glass body is considerable because the high tensile strength of the frame subjects the glass to compressive forces even at operating temperatures are higher than in the past for connections with aluminum sockets was possible.

Sample copies of the terminal according to the invention were subjected llärmeschocKversuchen in which the temperature of the environment 1m operation was very rapidly changed from a low temperature of about -55 ⁰ C to a high temperature of about +225 ⁰ C, and other assays in which the terminals continuously at least 200 ⁰ C 1n operation were. The tightness was fully retained. Thus endured the seals and the glass WE λ sent! I greater temperature extremes than known connections with aluminum frames, which, as noted above, have your highest operating at about 100 ⁰ C.

In addition to the advantage that the connection 1n according to the invention can be used reliably over a wide temperature range it also saves a lot of weight compared to conventional connections made of steel and iron alloys. This 1st especially important when used in the civil and aerospace industries, where weight is a critical factor.

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As already mentioned above, copper is used for the contacts also compared to the known designs a considerable increase in the conductivity of the connection according to the invention. To protect the copper of the contacts from excessive oxidation when melting the seals these can be coated or plated with nickel, rhodium or other oxidation-resistant metals.

From the foregoing description it can be seen that the invention provides an extremely reliable hermetically sealed electrical Connection creates which has low weight and high electrical conductivity and via a known connection never reached temperature range resistant to heat shock 1st.

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Claims (1)

Claims 1. Hermetically sealed electrical connection, thereby ge -ke η η ζ eich η et that it maintains its hermetic tightness over a temperature range of about -55 ⁰ C to at least + 225 ⁰ C and a hollow metal socket (.12) with a them penetrating opening (24), the side walls of which have a glass insulator (26) fused therein tightly fitting and under compressive stress, and little- | at least one in the insulator (26) fused, penetrating this electrical contact or a metal part (23), the contact or the metal part (20) made of a metal having a coefficient of thermal expansion matched to that of the insulator (26) and held only by this insulator (26), the glass of which has a melting point below that of the metal frame, the metal of which has a greater coefficient of thermal expansion than the glass and in the stress-relieved state has such a tensile strength that the. 1st possible to grant melting the glass insulator 1n of the socket, followed by cooling to -55 ⁰ C without the metal frame tensile stresses that exceed its tensile strength in the annealed state corresponds · voltage. 2, connection according to claim 1, characterized in that the glass has a coefficient of thermal expansion of about 17.10 "S / grd has ι government exists. 17.10 "\ ./ grd and the metal frame is made of aluminum 3, connection according to claim 1 or 2, characterized in that the socket (12) is made of an aluminum alloy with a tensile strength of at least 1,000 kp / cm in annealed condition exists, 009886/1598 4. Connection according to claim 1, characterized g e Ic e η η ζ e 1 c h -net that the! / Thermal expansion coefficient of the socket is not more than one and a half times that of the glass. 5. - Connection according to claim I _1, characterized in that the glass insulator (26) is a one-piece, prefabricated part with beveled outer edges (34) and at least one countersunk hole (35) for receiving a contact (28) and that the beveled outer edges and the countersunk hole form bonds or transitions between the glass and the frame (12) and between the glass and the contact (23), which are under uniform tension, 6 »terminal according to claim 1" characterized gekennzei ch "η et, that the contact (28) 1st made of copper, that the glass has a flow temperature of about 540 ⁰ C and in that the Hetallfassung (12) comprises a substantially 23,4 Härmeausdehnungskoeffizienten of 1m -10 * ⁶ / grd. 7 »Connection according to claim 1, characterized in that the tensile strength of the metal of the socket in the stress relieved condition is at least 1,400 kp / cm. 8 »Connection according to claim 5, characterized in that the bonds or transitions between the glass and the socket (12) and between the contact (28) and the glass by treating the connection at a burn-in temperature are formed. 0 0 98 86/1598