Glass composition for micro-D connector sealing

Abstract

The present invention relates to a tellurium-oxide-based glass composition for forming a glass-to-metal seal to alloys or metals having a coefficient of thermal expansion higher than 16 ppm/ C., said composition comprising TeO.sub.2, ZnO, TiO.sub.2 and optionally K.sub.2O and being essentially free of lead oxide, sodium oxide and vanadium oxide. In addition it relates to the use of the glass composition according to the invention to form a glass-to-metal seal between copper or a copper alloy and an alloy or a metal having a coefficient of thermal expansion higher than 16 ppm/ C., in particular aluminum alloys. It furthermore relates to a connector comprising a contact made of copper or of copper alloy, an insert and/or shell made of a metal or alloy having a coefficient of thermal expansion higher than 16 ppm/ C. and, by way of glass-to-metal sealant between the contact and the insert and/or shell, a tellurium-oxide-based glass having the composition according to the invention. Lastly, it relates to a process for forming a glass-to-metal seal between a contact made of copper or of copper alloy and an insert and/or shell made of metal or alloy having a coefficient of thermal expansion higher than 16 ppm/ C.

Claims

1. A tellurium-oxide-based glass composition for forming a glass-to-metal seal to alloys or metals, wherein the alloy or metal has a coefficient of thermal expansion higher than 16 ppm/ C., said composition consisting of, in molar percent: 60-80% of TeO.sub.2; 5-35% of ZnO; TiO.sub.2 in an amount of at most 15%; 0-30% of K.sub.2O; and unavoidable impurities, said composition being essentially free of lead oxide, sodium oxide and vanadium oxide.

2. The glass composition as claimed in claim 1, which comprises TiO.sub.2 in an amount in molar percent of 1-13%.

3. The glass composition as claimed in claim 1, which comprises K.sub.2O in an amount in molar percent of at most 30%.

4. The glass composition as claimed in claim 3, which comprises K.sub.2O in an amount in molar percent of 1-20%.

5. The glass composition as claimed in claim 1, which consists of, in molar percent: 64-79% of TeO.sub.2; 14-31% of ZnO; TiO.sub.2 in an amount of at most 15%; 0-20% of K.sub.2O; and unavoidable impurities.

6. The glass composition as claimed in claim 1, wherein the coefficient of thermal expansion of the glass is in a range of 11-22 ppm/ C.

7. The glass composition as claimed in claim 1, wherein the alloy or metal having a coefficient of thermal expansion higher than 16 ppm/ C. is chosen from the group consisting of aluminum and its alloys, stainless steel, copper and copper alloys.

8. The glass composition as claimed in claim 7, wherein the alloy or metal having a coefficient of thermal expansion higher than 16 ppm/ C. is chosen from the group consisting of aluminum-silicon, aluminum-magnesium or aluminum-magnesium-silicon alloy.

9. The glass composition as claimed in claim 7, wherein the alloy or metal having a coefficient of thermal expansion higher than 16 ppm/ C. is a copper-beryllium alloy.

10. The glass composition as claimed in claim 9, wherein the copper-beryllium alloy is plated with nickel or plated with nickel and gold.

11. A glass-to-metal sealant between copper or a copper alloy, and an alloy or a metal having a coefficient of thermal expansion higher than 16 ppm/ C. made from the glass composition as claimed in claim 1.

12. The glass-to-metal sealant as claimed in claim 11, wherein the alloy or metal having a coefficient of thermal expansion higher than 16 ppm/ C. is other than copper or than a copper alloy and is chosen from the group consisting of aluminum and its alloys and stainless steel.

13. The glass-to-metal sealant as claimed in claim 11, which is formed in a connector, between a contact made of copper or of copper alloy and an insert and/or shell made of an alloy or metal having a coefficient of thermal expansion higher than 16 ppm/ C.

14. A connector comprising a contact made of copper or of copper alloy, an insert and/or shell made of a metal or alloy having a coefficient of thermal expansion higher than 16 ppm/ C. and a glass-to-metal sealant between the contact and the insert and/or shell, wherein the sealant is a tellurium-oxide-based glass having the composition such as defined in claim 1.

15. The connector as claimed in claim 14, characterized in that the alloy or metal having a coefficient of thermal expansion higher than 16 ppm/ C. is chosen from the group consisting of aluminum and its alloys and stainless steel.

16. The connector as claimed in claim 14, wherein the copper alloy or copper of the contact is not plated with nickel, wherein the alloy or metal having a coefficient of thermal expansion higher than 16 ppm/ C. is chosen from the group consisting of aluminum and its alloys and wherein the connector is non-magnetic with a residual magnetism <20 nT.

17. The connector as claimed in claim 14, which is a micro-D connector.

18. The connector as claimed in claim 14, which is hermetic with a helium leak rate lower than 310.sup.1 mbar.Math.l/s, has an insulation resistance between the contacts and between each contact and the insert and/or shell >5 Gohm and an operating temperature able to reach as high as 200 C.

19. A process for forming a glass-to-metal seal between a contact made of copper or of copper alloy, and an insert and/or shell made of a metal or alloy having a coefficient of thermal expansion higher than 16 ppm/ C., comprising the following successive steps: a) providing a contact made of copper or of copper alloy, and an insert and/or shell made of a metal or alloy having a coefficient of thermal expansion higher than 16 ppm/ C.; b) providing a preform of tellurium-oxide-based glass having the composition as defined in claim 1; c) bringing the preform into contact with the contact and with the insert and/or the shell; d) using a suitable tool, maintaining contact between the assembly made up of the contact, preform and insert and/or shell; e) heating the assembly made up of the contact, preform and insert and/or shell to a temperature and for a time sufficient to obtain the glass-to-metal seal; f) collecting the assembly thus sealed.

20. The process as claimed in claim 19, characterized in that the temperature of step e) is in a range of 350-500 C.

Description

(1) FIG. 1 shows an example of a 15-pin female micro-D connector according to the standard Mil-DTL-83513.

(2) FIG. 2 shows, in cross section (FIG. 2A) and as seen from above (FIG. 2B), schematic views of a compression seal of a contact (1) in a shell (3) using glass (2) according to the invention.

EXAMPLE 1: GLASS-TO-METAL SEAL BETWEEN CONTACTS MADE OF COPPER ALLOY AND A SHELL MADE OF ALUMINUM ALLOY WITH GLASS COMPOSITIONS ACCORDING TO THE INVENTION

(3) The Glasses the Composition of which is Indicated in Table 2 Below were Manufactured

(4) TABLE-US-00002 TABLE 2 General data on 3 glass compositions according to the invention CTE Durability Tg (ppm/ (g/ Glass Composition ( C.) C.) (min .Math. cm.sup.2)) 2 (TeO.sub.2).sub.65(TiO.sub.2).sub.5(ZnO).sub.30 346 13.6 1.97 10.sup.7 4 (TeO.sub.2).sub.65(TiO.sub.2).sub.5(ZnO).sub.22(K.sub.2O).sub.6.3 320 15.5 3.15 10.sup.7 5 (TeO.sub.2).sub.65(TiO.sub.2).sub.5(ZnO).sub.22(K.sub.2O).sub.8 310 16 2.5 10.sup.7 6 (TeO.sub.2).sub.65(TiO.sub.2).sub.5(ZnO).sub.20(K.sub.2O).sub.10 296 18.4

(5) The chemical-durability values were determined in a soxhlet at 95 C. in continually renewed demineralized water according to standard ISO16797.

(6) This is an extremely critical test because the rate of dissolution remains at its maximum throughout the time (no saturation of water).

(7) The glass-to-metal seals with these glass compositions were formed to shells made of aluminum alloy of the 4000, 5000 or 6000 family: 4047, 4032, 5083, 5754 or 6061.

(8) The contact used was made of copper alloy: 33 type copper-beryllium alloy, also called C17300 (1.8% Be, 0.2% Co and at least 0.2% Pb for machinability). The glass was placed in the form of a cylindrical preform around each contact.

(9) To form the glass-to-metal seals, the assembly made up of the metals and glass preforms was held in place using a suitable tool.

(10) The heating was carried out in an oven, without a protective atmosphere, at the temperature and for the times indicated in table 3.

(11) The glass-to-metal seal was formed by compression level with the shell as schematically shown in FIG. 2. The glass was thus compressed everywhere, except level with the contact where a radial extension occurs.

(12) Insulation resistance was measured using a megohmeter under 500 Vdc. The insulation resistances obtained reached the detection limit of the apparatus (20 Gohms).

(13) Hermeticity to helium was measured using a helium leak detector (Adixen ASM 142) according to the standard MIL-STD-883, under test condition A4. The measured leak rates were at the detection limit of the apparatus after a rapid measurement, i.e. after a measurement shorter than 1 minute (310.sup.1 mbar.Math.l/s).

(14) To determine the wetting angle , the glass was deposited on an aluminum sheet and exposed in an oven to the temperature indicated for the time indicated in table 3 (same temperature and same time as for the glass-to-metal sealing process). The assembly made up of the glass and sheet was then removed from the oven, the glass setting immediately. The angle was then determined optically with a Nikkon camera (D5100, lens: AF-S Micro NIKKOR 40 mm f:2.8G) and the freeware software package imageJ.

(15) Table 3 below shows the results obtained with these glasses.

(16) TABLE-US-00003 TABLE 3 Experimental data obtained with the glasses according to the invention in the process according to example 1 Time/temperature Hermeticity Insulation Residual (min/ C.) of the to helium resistance magnetism Glass sealing operation () (mbar .Math. l/s) (Gohm) (nT) 2 60/440 70-74 <3 10.sup.10 >20 <20 60/460 42-39 4 30/480 98- <3 10.sup.10 >20 <20 103 30/500 49-50 5 60/440 96-87 <3 10.sup.10 >20 <20 30/500 18-29 6 60/440 41-39 <3 10.sup.10 >20 <20 30/500 21-28 30/500 18-29

(17) The various glass-to-metal seals formed were then exposed to 5 thermal-shock cycles of 55 C.+125 C., with plateaus of 30 minutes in vertical shock climatic chambers, for example as sold under the trademark Climats.

(18) Hermeticity was once again measured: all the parts retained their hermeticity and the measured value was at the detection limit of the apparatus.

(19) Five thermal shock cycles going from 55 C. to +200 C. were then carried out on the same parts. The measured hermeticity revealed that, once again, the parts had a leak rate lower than the detection limit of the apparatus.

(20) These glasses are therefore suitable for the glass-to-metal sealing of connectors. It is thus possible to obtain, by virtue of these glasses, connectors, with contacts made of copper alloy, that are hermetic, non-magnetic, that meet the requirements of the RoHS directive and that have an operating temperature able to reach as high as 200 C.

EXAMPLE 2: GLASS-TO-METAL SEAL BETWEEN CONTACTS MADE OF A COPPER ALLOY PLATED WITH NICKEL OR PLATED WITH NICKEL AND GOLD AND A SHELL MADE OF ALUMINUM ALLOY WITH GLASS COMPOSITIONS ACCORDING TO THE INVENTION

(21) Two glass compositions described in example 1 (glasses number 2 and 5) were used to form a glass-to-metal seal between a contact made of a copper-beryllium alloy plated with nickel or plated with nickel and gold and a shell made of aluminum alloy according to example 1. The process for forming a glass-to-metal seal and the measuring methods were identical to those of example 1.

(22) Only the contact was different since various surface treatments were carried out on the contacts made of copper-beryllium alloy of example 1: contacts plated with nickel and plated with nickel and gold. In each and every case, chemical nickel (Ni) was used with various amounts of phosphorus (P). In the case of contacts plated with nickel and gold, gold (Au) alloyed with nickel was deposited by electrolysis after the deposition of nickel.

(23) Table 4 below presents the results obtained with these glasses.

(24) TABLE-US-00004 TABLE 4 experimental data obtained with the glasses according to the invention in the process according to example 2 Surface Hermeticity to Insulation Residual treatment of the helium resistance magnetism Glass contact (mbar .Math. l/s) (Gohm) (nT) 5 6 m Ni 11% P + <3 10.sup.10 >20 >20 6 m Au 2 6 m Ni 11% P + <3 10.sup.10 >20 >20 6 m Au 2 3 m Ni 6% P <3 10.sup.10 >20 >20 2 5 m Ni 6% P <3 10.sup.10 >20 >20 2 10 m Ni 11% P <3 10.sup.10 >20 >20

(25) By virtue of these glasses, it is possible to obtain hermetic connectors that meet the requirements of the RoHS directive and that have contacts made of a copper alloy plated with nickel or plated with nickel and gold. However, these connectors are not non-magnetic, even if the contacts are to start with (if the percentage of phosphorus in the surface-treatment layer is higher than or equal to 10.5%).

EXAMPLE 3: GLASS-TO-METAL SEAL BETWEEN CONTACTS MADE OF A COPPER ALLOY AND A SHELL MADE OF STAINLESS STEEL WITH GLASS COMPOSITIONS ACCORDING TO THE INVENTION

(26) One of the glass compositions described in example 1 (glass number 2) was used to form a glass-to-metal seal between a contact made of copper-beryllium alloy according to example 1 and a shell made of 304L and 316L stainless steel. The glass-to-metal sealing process and the measuring methods were identical to those of example 1. Only the shell was different since it was a shell made of stainless steel.

(27) Table 5 below presents the results obtained with this glass.

(28) TABLE-US-00005 TABLE 5 experimental data obtained with glasses according to the invention in the process according to example 3 Glass Hermeticity to helium (mbar .Math. l/s) Insulation resistance (Gohm) 2 <3 10.sup.10 >20

(29) A glass-to-metal seal to stainless steel does not allow non-magnetic connectors to be obtained. However, the connectors obtained with the glass composition according to the invention were hermetic.

(30) It is therefore possible to produce hermetic micro-D connectors having a stainless steel shell and contacts made of copper alloy with a glass containing no lead oxide.

COMPARATIVE EXAMPLE 1: PHOSPHATE GLASSES

(31) 5 phosphate-glass compositions were tested for sealing contacts made of copper-beryllium alloy to a shell made of aluminum alloy. Phosphate glasses are generally known for their high degree of water absorption. The compositions were therefore optimized to improve their durability via the presence of acid oxides such as Al.sub.2O.sub.3, which create AlPO.sub.4 groups that reinforce the glass network, or the addition of amphoteric compounds such as Nb.sub.2O.sub.5.

(32) The glasses the composition of which is indicated in table 6 below were therefore manufactured.

(33) TABLE-US-00006 TABLE 6 General data on 5 phosphate-glass compositions Tg CTE Durability Glasses Composition ( C.) (ppm/ C.) (g/cm.sup.2 .Math. min) 11 (NaPO.sub.3).sub.36(KPO.sub.3).sub.36(Ba(PO.sub.3).sub.2).sub.12)(Al.sub.2O.sub.3).sub.8(Al(PO.sub.3).sub.3).sub.8 380 15 1.23 10.sup.6 12 (NaPO.sub.3).sub.35(KPO.sub.3).sub.35(Ca.sub.2(P.sub.2O.sub.7).sub.2).sub.10(Al.sub.2O.sub.3).sub.3.65(Al(PO.sub.3).sub.3).sub.1.65(ZnO).sub.15 380 14.2 1.68 10.sup.6 14 (NaPO.sub.3).sub.37.5(KPO.sub.3).sub.37.5(Ba(PO.sub.3).sub.2).sub.12.5)(Nb.sub.2O.sub.5).sub.12.5 381 16.8 1.28 10.sup.5 32 (NaPO.sub.3).sub.35(KPO.sub.3).sub.35(Ca.sub.2(P.sub.2O.sub.7).sub.2).sub.10(Al.sub.2O.sub.3).sub.3.65(Al(PO.sub.3).sub.3).sub.1.65(ZnF.sub.2).sub.15 360 13 34 (NaPO.sub.3).sub.35(KPO.sub.3).sub.35(Ca.sub.2(P.sub.2O.sub.7).sub.2).sub.10(Al.sub.2O.sub.3).sub.3.65(Al(PO.sub.3).sub.3).sub.1.65(ZnF.sub.2).sub.10(CuF.sub.2).sub.5 362 12.9

(34) For the glass-to-metal seals, the metals and the process used were the same as in example 1. The heating was carried out in an oven under atmosphere, but other methods of heating could have been envisioned for forming the glass-to-metal seal.

(35) The measuring methods were identical to those of example 1.

(36) Table 7 below presents the results obtained with these glasses.

(37) TABLE-US-00007 TABLE 7 Experimental data obtained with phosphate glasses Time (min)/ Temperature Hermeticity ( C.) to Insulation Residual of the sealing helium resistance magnetism Glasses operation () (mbar .Math. l/s) (Gohm) (nT) 11 9.5 10.sup.6- 0.3-14 <20 5.2 10.sup.8 12 60/500 104- 4 10.sup.4- 0.2-0.5 <20 108 4 10.sup.9 14 >10.sup.5 1.2-2.2 <20 32 60/480 115 1.3 10.sup.5 2 <20 34 60/500 113- 4 10.sup.5 0.1 <20 117

(38) These glasses are therefore unsuitable for meeting the requirements in terms of wettability and above all in terms of insulation resistance.

(39) Specifically, the measured wetting angles and the glass-to-metal seals formed demonstrated an evident lack of wettability to the aluminum. It has been observed that even if the temperature and time in the oven were increased, the wettabilities of these glasses did not improve.

(40) These glasses therefore did not allow parts with a leak rate lower than 110.sup.9 mbar.Math.l/s to be obtained.

(41) In addition, insulation resistance varied from trial to trial, certainly because of the varying amount of air between the glass and the aluminum. These glasses also exhibited a capacitive effect, very certainly due to ionic conduction, due to sodium ions for example.

COMPARATIVE EXAMPLE 2: CHALCOGENIDE GLASSES

(42) Three chalcogenide glasses were synthesized because, according to the literature, they had Tgs and CTEs that meant they could have met the requirements.

(43) Their properties are presented in table 8 below.

(44) TABLE-US-00008 TABLE 8 General data on 3 chalcogenide-glass compositions Glass Composition Tg ( C.) CTE (ppm/ C.) 20 Ge.sub.25Sb.sub.10S.sub.65 + 10% CsCl 260 about 20 22 Ge.sub.26Sb.sub.10S.sub.24 340 about 16 26 15Ga.sub.2S.sub.375GeS.sub.210CsCl 370 about 20

(45) These glasses were abandoned after wettability trials because they required the glass-to-metal seal to be formed under a controlled atmosphere to prevent their oxidation.

COMPARATIVE EXAMPLE 3: ALKALI GLASSES

(46) An alkali glass containing no lead oxide, which was sold commercially under the name Msoft 5 by Mansol Preforms, was tested in the context of formation of a glass-to-metal seal between copper alloys and a shell made of aluminum alloy.

(47) Its properties are presented in table 9 below.

(48) TABLE-US-00009 TABLE 9 General data on the composition of the alkali glass CTE Sealing temperature Trade name Type of glass (ppm/ C.) ( C.) Msoft 5 Alkali glass 16.0 560-600

(49) To form the glass-to-metal seals, the same process as that in example 1 was used for 1 hour and with a temperature of 570 C.only the tested glass was changed. However, it was not possible to produce parts the leak rate of which was measurable with the alloys 4000 and 5083. The latter have a quite low melting point and their surface deformed and oxidized enormously during the formation of the glass-to-metal seal. Their surface was therefore no longer smooth enough to ensure a uniform compression of the gasket and a hermetic fixture. The measuring methods were identical to those of example 1.

(50) Table 10 below presents the results obtained with this glass.

(51) TABLE-US-00010 TABLEAU 10 Experimental data obtained with an alkali glass Insulation Residual Helium leak rate resistance magnetism Contact (mbar .Math. l/s) (Gohm) (nT) Unplated contact <3 10.sup.10 0.2-0.5 <20 Contact plated with nickel <3 10.sup.10 0.3-1 >20 (10 m Ni 11% P)

(52) The helium leak rate obtained with the various connectors was below the detection limit of the measuring apparatus after a rapid measurement, i.e. after a measurement shorter than 1 minute. In contrast, the measured insulation resistance was much lower than that desired. A capacitive effect was observed, i.e. the resistance was observed to increase with the application time of the voltage, as during the charging of a capacitor. This is typical of ionic conduction. The glass being alkali-based, it is highly probable that small alkali-metal ions, such as sodium ions, are responsible for this conduction.

(53) Specifically, these ions being small, they may easily move through the glass if the iono-covalent bonds binding them to the rest of the glass network have too low an energy with respect to the attraction of the applied negative voltage.

(54) Thus, during the application of the voltage, Na.sup.+ ions move toward the negative electrode. The resistance was therefore very low to start with. However, it then gradually increased as ions reached this pole. On a polarity inversion, this effect recommenced.

(55) To increase insulation resistance, trials were carried out in which the surface of the contact was pre-oxidized (see table 11 below). Specifically, forming an oxide layer adds an insulating layer between the contact and the glass, this being liable to increase insulation resistance.

(56) TABLE-US-00011 TABLE 11 Experimental data obtained with an alkali glass and a pre- oxidized contact Helium leak Insulation Residual Contact (time and temperature rate resistance magnetism of the pre-oxidation) (mbar .Math. l/s) (Gohm) (nT) Unplated pre-oxidized contact <3 10.sup.10 1-2 <20 (200 C./5 min) Contact plated with nickel then <3 10.sup.10 1-22 >20 pre-oxidized (530 C./10 min)

(57) Unfortunately, insulation resistance varied greatly from trial to trial. Two explanations may be given for this observation. Firstly, the thicknesses of oxide created are perhaps not always the same, and, during the formation of the glass-to-metal seal, the oxide may dissolve in the glass. Thus, if the oxide is not thick enough in places, it is possible to end up with oxide-free zones after the formation of the glass-to-metal seal. Secondly, when the contact is being handled in order to be placed in the tool, oxide may be removed. Specifically, all that is required for this insulating layer to be removed locally is for a scratch to scratch off the oxide.

(58) Obtaining a sufficient insulation resistance is therefore not something that is easy and it is risky to rely solely on oxide to guarantee it. This alkali glass can therefore not be used in the targeted application.