Title of Invention

A TEST STRUCTURE FOR TESTING ELECTRONIC SUB-ASSEMBLIES OF SPACE APPLICATIONS UNDER THERMO VACUUM CONDITIONS

Abstract

ABSTRACT "A test structure for testing electronic sub-assemblies of space applications under thermo-vacuum conditions " The present invention discloses a test structure for testing electronic sub¬assemblies of space applications under thermo-vacuum conditions comprising: a single flange; said single flange provided with D-type shell connectors with plug and socket pins crimped with shortest link on both sides of said flange without adopted harness; multi strand insulated wires of a suitable length are crimped on both sides of plug and socket pins, inspection holes of said pins being sealed with an epoxy adhesive for vacuum sealing and said pins are inserted in the outer side and inner side of said connector shell being mounted flush onto the said flange; and said flange also provided with D-type coaxial contacts crimped on both sides of said flange without adopter harnesses. Fig 2b

Full Text

The present invention relates to a test-fixture for testing electronic sub¬assemblies under thermo-vacuum conditions to ensure high reliable operation when used in space. Background of the Invention The hardware developed for space is tested and evaluated under various environmental conditions. Thermo-vacuum test is one of the critical tests in which the space environment of temperature and vacuum are simulated. Thermo-vacuum testing requires vacuum of the order of better than 10"^ Torr and temperature around -15 to +55°C. During the test, the subsystem is kept in the vacuum chamber, the electrical stimuli are provided from an external test setup and the outputs are taken to the test system. The interconnections are established through hermetically sealed (vacuum proof) round-shell imported feed-thru cormectors mounted on stainless steel flanges. The feed-thru consists of three parts, namely, flange mount round-shell plug on both sides (vacuum tight); adopter harness inside thermo-vac chamber with round-shell connector socket on one side and D-type plug/socket at the other end (compatible to unit under test); and adopter harness outside thermo-vac chamber with round-shell connector socket on one side and D-type plug/socket at the other end (compatible to test system). Round shell connectors are usually imported leading to an increased cost. The harnesses are standard wires as the harness and fee-thrus were common to all sub-systems. Such cormectors require more space for mounting and handling. Also, only two or three connectors could be accommodated on one flange. When the numbers of interconnections are more it requires multiple cormectors and flanges which causes increase in length of harness. This additional harness causes signal distortions due to increases length, change in wire type, discontinuities in impedance, unshielded nature of harness etc. This affects the performance of low noise and high precision video signal processors. For digital high speed clocks and signals, the number of discontinuity causes reflection problems. The longer harness affects the performance of the sub-assemblies under test This has been critical for testing of electronic system having better than 12 bit digitization. Storage and handling of such flanges also needs special care. Typical time of 8-10 hours for starting any test (mounting, continuity check, functional check and lastly test run for the chamber due to the type of handling of flanges and harness). Objects of the Invention The present invention envisages all connectors to be assembled onto one standard SS flange. Also, the connector types shall be the same as those used in the onboard package and not the hermetically sealed type thereby eliminating adopter harness. Preferably, standard connectors, which are used generally for ground test hardware with low out gassing, are used to reduce cost factors also. Another object of the invention is to reduce the overall length of the cables used, thereby reducing the number of impedance discontinuities (joints). Another object of the invention is to use fabricate harness with specific wire types for each subsystem instead of using common type of harness. Another object of the invention is to make the sub-assemblies verification easier, by ensuring that no harness continuity check is required causing minimum handling and in turn reducing loading time. Another object of the invention is to fabricate the components with standard materials available in the electronic laboratory. Summary of the Invention The present invention discloses a test structure for testing electronic sub¬assemblies of space applications under thermo-vacuum conditions comprising: a single flange; said single flange provided with D-type shell cormectors with plug and socket pins crimped with shortest link on both sides of said flange without adopted harness; multi strand insulated wires of a suitable length are crimped on both sides of plug and socket pins, inspection holes of said pins being sealed with an epoxy adhesive for vacuum sealing and said pins are inserted in the outer side and inner side of said connector shell being mounted flush onto the said flange; and said flange also provided with D-type coaxial contacts crimped on both sides of said flange without adopter harnesses. Brief Description of the drawings Fig 1 shows the conventional flanges required to test one specific payload configuration. All the three flanges are required to be mounted and stored after the test. Fig 2 shows the flange according to the present invention, which can be used for many payload configurations as many connectors are accommodated to meet versatile needs. Fig 3 shows the inner side of the flange according to the present invention Fig 4 shows the outer side of the flange according to the present invention. Fig 5 shows the perspective view of the flange according to the present invention. Fig 6 shows the partial cross sectional view of the flange according to the present invention; Fig 7 shows the construction of the flange according to the present invention Detailed Description of the Invention Figure 1 shows the conventional interconnections established through hermetically sealed feed-thru connectors mounted on stainless steel flanges. The performance of the sub-system is verified with simulated harness. OCM-2 Payload electronics (PLE) package has about 9 D-type connectors which include D-type with coaxial contacts. The feed-thru connectors are of hermetically sealed 37 pin round shell type and BNC type connectors. The interconnection harness for thermo-vac requires large number of adopter harnesses to make connections from D-type connectors on the onboard package to D-type connectors on test system through round shell/BNC vacuum tight feed-thrus. The length of the harness depends on chamber configuration like location of payload package inside the chamber, number of round shell connectors that can be mounted on one steel flange, number of flanges available on main door and on the body of the chamber. This additional harness causes signal distortions and affects the performance of low noise video processor and high-speed clocks etc. Hence, minimization of test harness length and the number of discontinuities has been critical for testing 12 bit electronic system of OCM-2. Also, the installation of test harness, test set-up and verification of payload package takes considerable time due to distribution of flanges on the chamber and increased length of harness. The present invention will now be described with reference to figures 2 to 7. All the required connectors are assembled onto one standard SS flange (1). The connector types are the same as those used in the onboard package thereby eliminating adopter harness. Profile cutouts compatible to the required 'D' type connectors (2), are made on the flange. On both sides of the flange, D-type connector pins are crimped with the shortest link and the vacuum sealing is achieved in this technique. The front side of the flange is provided with mounting holes (H) compatible to the chamber's flange (1). Connectors (2) are mounted on both the sides of flange (1) with stud (4). Connectors are D-type shells with plug/socket pins (22, 24, 26 AWG wire) or RP contacts. Wire harness (5) to take out interconnections to the unit and from the unit under test in vacuum chamber is provided as shown especially in Figure 2b. Standard 24 AWG multi-stranded insulated wires (3), preferably multi-strand Kepton/Teflon wires, are taken and cut into pieces of ~ 1 length. The length is selected based on flange thickness, projections of the pins on rear side, space required for inserting the pins and sealing etc. The wires (3) are crimped on both sides of the flange to plug and socket pins respectively. The inspection holes of the pins are also sealed with epoxy. The pins are inserted in the outer side connector shell. The outer connector is mounted in-flush onto the SS flange (1) with standard screw available with connectors. The pins are inserted into the inner side connector shell and it is mounted onto the flange. Standard screw is used to derive the support for the flange of inner connector. Similarly, all other connectors are also assembled. For D-type coaxial contacts, link wire is used for connecting live pins. The pins are sealed. Preferably, the pins are filled with an epoxy-based adhesive to effect sealing. The shield contacts are touching each other and hence they are soldered. The projection of the mounting screw is used to extend the length by using an additional standard screw. This will provide guide to the mating harness and it will not stress the contacts. Adhesive sealing is done from the rear side of the outer connector such that it provides vacuum sealing of gaps between the connector body and the SS flange, gap between connector metal shell, gap between each pin and the insulator and the insulator holding the pins. The SS flange (1) is heated momentarily with hot air gun so that the viscosity of the adhesive is reduced and spreads into the minute gaps. The flange (1) is left undisturbed for about 24 hours for curing of the sealing adhesive. Care is taken during adhesive application such that it does not spread and fall onto active contact area pins. Subsequently, the flange (1) is operationally used for test and evaluation of ongoing payloads for remote sensing satellites. The flange is tested for electrical continuity for all pins. Also, it is tested by multiple mating/de-mating of test harness. After this, the flange is mounted onto the thermo-vac chamber and tested for vacuum. Subsequently, the flange is operationally used for test and evaluation of all the 3 PLE packages of OCM-2. Loading time of package and test preparation time was reduced from 10 hours to 1 hour. This flange can be used for any other package where D-type connectors and D-type connectors with coaxial contacts are required. A comparison of newly developed flange with conventional flange is given below. WE CLAIM 1. A test structure for testing electronic sub-assemblies of space applications under thermo-vacuum conditions comprising: a single flange; said single flange provided with D-type shell connectors with plug and socket pins crimped with shortest link on both sides of said flange without adopted harness; multi strand insulated wires of a suitable length crimped on both sides of said plug and socket pins, inspection holes of said pins being sealed with an epoxy adhesive for vacuum sealing and said pins are inserted in the outer side and irmer side of said connector shell being mounted flush onto the said flange; and said flange also provided with D-type coaxial contacts crimped on both sides of said flange without adopter harnesses. 2. The test structure as claimed in claim 1, wherein atmost seven D-type shell connectors and atmost four D-type coaxial contacts are provided on said flange. 3. The test structure as claimed in claim 1, wherein profile cuts compatible to the required D-type connectors are made on said flange. 4. The test structure as claimed in claim 1, wherein link wires are used for connecting live pins of said D-type coaxial contacts, said pins being vacuum- sealed by means of an epoxy adhesive. 5. The test structure as claimed in claim 1, wherein mounting studs are provided for mounting said connectors. 6. The test structure as claimed in claim 1, wherein wire harness is provided to take out interconnections from and to said electronic sub-assembly under test in vacuum chamber. 7. A test structure for testing electronic sub-assemblies of space applications under thermo-vacuum conditions substantially as hereinabove described with reference to figure 2.

Documents:

3172-CHE-2008 AMENDED CLAIMS 27-08-2014.pdf

3172-CHE-2008 EXAMINATION REPORT REPLY RECEIVED 27-08-2014.pdf

3172-che-2008 abstract.jpg

3172-che-2008 abstract.pdf

3172-che-2008 claims.pdf

3172-che-2008 correspondence-others.pdf

3172-che-2008 description (complete).pdf

3172-che-2008 drawings.pdf

3172-che-2008 form-1.pdf

3172-che-2008 form-26.pdf

3172-che-2008 form-3.pdf

3172-che-2008 form-8.pdf

3172-CHENP-2008 AMENDED PAGES OF SPECIFICATION 27-08-2014.pdf

3172-CHENP-2008 POWER OF ATTORNEY 27-08-2014.pdf