SIST EN 50389:2007
(Main)Space product assurance - Wire-wrapping of high-reliability electrical connections
Space product assurance - Wire-wrapping of high-reliability electrical connections
This standard specifies the methods for preparing and assembling the parts to be joined by wire wrapping, and the selection, calibration, use and certification of the wire wrapping tools. The required wire-wrapped connections are illustrated in Figure 1. This type of connection is similar to "Class A preferred" or "modified" connection detailed in MIL-STD-1130, and NASA NHB 5300.4(3H). Only tested and qualified wire-wrapped connections are covered by this standard, which lists four wire sizes from 24 AWG to 30 AWG, and three terminal post sizes up to 1,78 mm maximum diagonal. The use of thicker wire and larger terminals are not advised. Thicker wire than 24 AWG is generally multistranded and terminated by soldering (see ECSS-Q-70-08) or by crimping (see ECSS-Q-70-26). Training and certification requirements for operators and inspectors are defined in 9.7 and in EN 13291-1.
Raumfahrt-Produktsicherung - Lötfreie elektrische Drahtverbindungen hoher Zuverlässigkeit
Diese Norm legt Verfahren zur Herstellung und Montage der mit lötfreien Drahtwickelverbindungen (im Folgenden kurz 'Wickelverbindungen') zu verbindenden Teile und enthält Angaben zur Auswahl, Kalibrierung, zum Gebrauch und zur Zertifizierung von Wickelwerkzeugen. Bild 1 zeigt eine den Anforderungen entsprechende Wickelverbindung. Wickelverbindungen entsprechen Verbindungen der "Klasse A (empfohlen)" oder "modifizierten" Verbindungen, wie sie in MIL-STD-1130 und NASA NHB 5300.4(3H) festgelegt sind. Diese Norm gilt nur für geprüfte und qualifizierte Wickelverbindungen und bezieht sich auf vier Drahtstärken (AWG 24 bis AWG 30) und drei Stiftgrößen (mit einem Diagonalmaß von maximal 1,78 mm). Die Verwendung von dickerem Draht und größeren Wickelstiften wird nicht empfohlen. Bei Draht-durchmessern von mehr als AWG 24 wird im Allgemeinen Litze mit Lötverbindungen (siehe ECSS Q 70-08) oder Crimpverbindungen (siehe ECSS-Q-70-26) verwendet. Anforderungen an die Schulung und Zertifizierung von Wickel- und Prüfpersonal sind in 9.7 und in EN 13291 1 festgelegt.
Conformité des produits spaciaux - Connexion par enroulement des connexions électriques de haute fiabilité
Zagotavljanje vesoljskih izdelkov - Visoko zanesljivi električni spoji z žičnim ovijanjem
General Information
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EUROPEAN STANDARD EN 50389
NORME EUROPÉENNE
EUROPÄISCHE NORM September 2005
ICS 49.060
English version
Space product assurance –
Wire-wrapping of high-reliability electrical connections
Conformité des produits spaciaux - Raumfahrt-Produktsicherung –
Connexion par enroulement Lötfreie elektrische Drahtverbindungen
des connexions électriques hoher Zuverlässigkeit
de haute fiabilité
This European Standard was approved by CENELEC on 2005-08-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in two official versions (English, German). A version in any other language
made by translation under the responsibility of a CENELEC member into its own language and notified to the
Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50389:2005 E
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EN 50389:2005 - 2 -
Foreword
This European Standard was prepared by the Technical Committee CENELEC TC 107X, Process
management for avionics (former CENELEC BTTF 91-3).
The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50389 on
2005-08-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn
(dow) 2008-08-01
1)
It is based on a previous version originally prepared by the ECSS product assurance working group,
reviewed by the ECSS Technical Panel and approved by the ECSS Steering Board. The European
Cooperation for Space Standardization (ECSS) is a cooperative effort of the European Space Agency,
National Space Agencies and European industry associations for the purpose of developing and
maintaining common standards.
This European Standard is one of a series of space standards intended to be applied together for the
management, engineering and product assurance in space projects and applications.
Requirements in this European Standard are defined in terms of what shall be accomplished, rather than
in terms of how to organize and perform the necessary work. This allows existing organizational
structures and methods to be applied where they are effective, and for the structures and methods to
evolve as necessary without rewriting the standards.
The formulation of this European Standard takes into account the existing EN ISO 9000 family of
documents.
———————
1)
ECSS-Q-70-30A.
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Contents
Introduction.5
1 Scope.5
2 Normative references .6
3 Terms, definitions and abbreviated terms .7
3.1 Terms and definitions .7
3.2 Abbreviated terms .8
4 Preparatory conditions.8
4.1 Hazards, health and safety precautions .8
4.2 Facility cleanliness .8
4.3 Environmental conditions .8
4.4 Lighting requirements.9
4.5 Configuration of process/workpiece .9
4.6 Cleaning.9
4.7 Tools and equipment .9
4.7.1 General.9
4.7.2 Cutting tool .9
4.7.3 Insulation strippers.9
4.7.4 Wire-wrapping tools .10
4.7.5 Unwrapping tools .11
4.8 Tool calibration.12
4.9 Wire-wrap process certification.12
4.10 Test monitoring equipment .13
5 Materials selection .13
5.1 Wire .13
5.1.1 General.13
5.1.2 Conductor .13
5.1.3 Wire insulation .13
5.2 Terminal post .14
5.3 Wire to terminal post combinations.16
6 Wire-wrap operation .16
6.1 Preparation for wire-wrapping.16
6.2 Process .16
6.3 Wire-wrap criteria .18
6.3.1 Usage of wrap levels.18
6.3.2 Number of turns on terminal post .19
6.3.3 Positioning and regularity of wrap connection.19
6.3.4 Wire routing .19
6.3.5 Rework.19
6.3.6 Wire-wrap and solder connections onto the same terminal post.20
7 Test methods .20
7.1 General .20
7.2 Workmanship .20
7.3 Stripping force.20
7.4 Unwrapping test .22
7.5 Connection resistance .22
7.6 Gas-tightness test .23
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EN 50389:2005 - 4 -
7.7 Metallography.24
7.8 Records of tests .24
8 Acceptance criteria.25
8.1 Visual inspection .25
8.2 Performance tests .26
8.2.1 General.26
8.2.2 Stripping force test.26
8.2.3 Unwrapping test .27
8.2.4 Connection resistance test .27
8.2.5 Gas-tightness test .27
8.2.6 Metallography .27
9 Quality assurance.27
9.1 General .27
9.2 Data .27
9.3 Nonconformance .27
9.4 Calibration.27
9.5 Traceability .27
9.6 Workmanship standards .29
9.7 Operator and inspector training and certification.29
9.8 Inspections.29
9.8.1 Visual inspection .29
9.8.2 Process control .29
10 Verification .30
10.1 General .30
10.2 Temperature cycling.30
10.3 Vibration.30
Annex A (informative) Daily process control sheet for test samples.31
Bibliography.32
Figure 1 — Single wire-wrapped connection to square terminal and reference corner .6
Figure 2 — Examples of approved wire-wrapping tools .11
Figure 3 — Hand unwrapping tools .11
Figure 4 — Minimum wrapping length on terminal post for each wire gauge.15
Figure 5 — Terminal post dimensions over minimum wrapping length
for each terminal size .15
Figure 6 — Wire-wrap connection process .17
Figure 7 — Position and regularity of wrap connection.18
Figure 8 — Stripping force test fixture.21
Figure 9 — Connection resistance test.22
Figure 10 — Gas-tightness test result .23
Figure 11 — Typical cross-section of wire-wrap (×64) .24
Figure 12 — Wire-wrap rejection criteria which require reworking of the connection.26
Figure 13 — Guide to quality assurance during wire-wrapping .28
Table 1 — Wire size to terminal post combinations .16
Table 2 — Minimum number of wire turns on terminal post .19
Table 3 — Minimum stripping force.21
Table 4 — Test current for connection resistance .23
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Introduction
This standard defines the requirements and quality assurance provisions for the manufacture of
high-reliability wire-wrapped connections made with round single-strand silver-plated wire onto
appropriately designed gold-plated terminals. Equipment design requirements, such as terminal spacing
and terminal mounting are not included in this standard.
This standard deals with the mechanical and electrical stability of wire-wrapped connections operating
under high vacuum, thermal cycling and vibration conditions imposed by space flight.
1 Scope
This standard specifies the methods for preparing and assembling the parts to be joined by wire
wrapping, and the selection, calibration, use and certification of the wire wrapping tools.
The required wire-wrapped connections are illustrated in Figure 1.
This type of connection is similar to “Class A preferred” or “modified” connection detailed in
MIL-STD-1130, and NASA NHB 5300.4(3H).
Only tested and qualified wire-wrapped connections are covered by this standard, which lists four wire
sizes from 24 AWG to 30 AWG, and three terminal post sizes up to 1,78 mm maximum diagonal.
The use of thicker wire and larger terminals are not advised. Thicker wire than 24 AWG is generally
multistranded and terminated by soldering (see ECSS-Q-70-08) or by crimping (see ECSS-Q-70-26).
Training and certification requirements for operators and inspectors are defined in 9.7 and in EN 13291-1.
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EN 50389:2005 - 6 -
Terminal post
End tail
Uninsulated wire turns
Insulated wire
Reference corner
(and at 1 below)
1
1
3
2
4
2
3
Shows either 3 or 4 corners of contact of insulation minimum ¾ turn of insulated wire
Figure 1 — Single wire-wrapped connection to square terminal and reference corner
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 13291-1 Space product assurance - General requirements - Part 1: Policy and principles
EN 13291-2 Space product assurance –General requirements - Part 2: Quality assurance
EN 13701 Space systems - Glossary of terms
EN 14097 Space product assurance - Non conformance control system
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ECSS-Q-70-02 Space product assurance - Thermal vacuum outgassing test for the screening
of space materials
ESA/SCC No. 3903 Solid wires, electrical 350 V, for wire wrapping
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this European Standard, the terms and definitions given in EN 13701 and the
following apply.
3.1.1
wire-wrapped connection
this connection consists of a helix of continuous, solid, uninsulated wire tightly wrapped around the
terminal post to produce a mechanically and electrically stable connection
NOTE The number of turns required depends on the gauge of wire used. All completed wraps have an additional minimum of 3/4
turn of the insulated wire that is in contact with at least three corners of the terminal post (see Figure 1).
3.1.2
terminal post
post of square or rectangular section onto which the interconnection wire is wrapped
3.1.3
a turn of wire
this consists of one complete single helical ring of wire wrapped 360º around the terminal post, touching
all four corners of the post
NOTE For the purpose of counting turns, the number of times the wrapped wire passes and intercepts the reference edge of the
terminal post after the first intercept of uninsulated wire and terminal post, constitutes the number of turns of uninsulated wire in the
connection.
3.1.4
reference corner
corner of the terminal post at which the first turn of uninsulated wire contacts, and from which the number
of turns of the wrapped wire are counted
3.1.5
end tail
end of the last turn of wire on the terminal post which may extend in a tangential direction instead of
resting against the post
3.1.6
gas-tight area
contact area between the terminal post and wire which excludes gas fumes
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EN 50389:2005 - 8 -
3.2 Abbreviated terms
The following abbreviated terms are defined and used within this European Standard:
AWG American wire gauge;
ECSS European Cooperation for Space Standardization;
ETFE ethylene-tetrafluorethylene;
PTFE polytetrafluorethylene;
PVDF polyvinylidene fluoride;
PFA perfluoroalkoxy;
RH relative humidity.
4 Preparatory conditions
4.1 Hazards, health and safety precautions
Particular attention shall be paid to health and safety precautions. A safety checklist is produced below:
a) hazards to personnel, equipment and materials shall be controlled and reduced to a minimum;
b) components, tools and controls shall be so located that personnel are not exposed to hazards such
as electric shock, cutting edges, sharp points or toxic atmospheres;
c) pneumatic air-powered wire-wrapping tools shall be connected to a regulated, lubricated and filtered
air supply, and disconnected when not in use.
4.2 Facility cleanliness
a) Unless classified as a cleanroom, the areas in which wire-wrapping is carried out shall be maintained
in a neat orderly fashion, with no loose material (such as dirt, dust, oils or clipped wires) that can
cause contamination of the wire-wrapped connection. Furniture shall be kept to a minimum in the
work areas and be arranged to allow easy and thorough cleaning of the floor.
b) Working surfaces shall be covered with an easily cleaned hard top, or have a replaceable surface of
clean, noncorrosive silicone-free paper.
c) Tools used in the wire-wrapping operation shall be clean. Excess lubricants shall be removed before
wire-wrapping starts.
d) Before assembly, wire and terminal posts shall be visually examined for cleanliness, absence of oil
films and freedom from tarnish or corrosion.
4.3 Environmental conditions
The wire-wrapping area shall have a controlled environment which limits entry of contamination. The area
shall be continuously controlled as follows:
— room temperature: (22 ± 3) °C;
— relative humidity: (55 ± 10) %.
The work stations shall not be exposed to draught. Fresh air shall be supplied to the room through a
filtering system so that there is a positive pressure difference with regard to adjacent rooms; the exhaust
air shall be suitably restricted.
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4.4 Lighting requirements
The light intensity shall be a minimum of 1 080 lx on the work surface. At least 90 % of the work area shall
be shadowless and without severe reflections.
4.5 Configuration of process/workpiece
In order to ensure compatibility with the customer requirements and as a means of identifying potential
problems, the supplier shall perform a review of the tools, materials and techniques which he plans to use
for the work. The review shall cover each separate manufacturing step and consider the dimensions and
metallurgical properties of the terminal post and wire such that they are guaranteed to be suitable for the
manufacture of wire-wrapped connections. Special attention shall be paid to the appropriate choice of
functional tools, particularly the type of power-driven wire-wrapping tool and associated rotary wrapping
bit and stationary sleeve. The quality of a wrapped connection depends largely on the maintenance and
adjusting of the cutting, stripping and wrapping tools.
Work shall be managed and organized such that tool bits and sleeves cannot be interchanged.
During handling and transportation, wrapped joints and their wires shall not suffer from any constraints
likely to cause deterioration.
4.6 Cleaning
The cleaning of materials where necessary, prior to wire-wrapping, shall be performed using one of the
following solvents:
— ethyl alcohol, 95,5 % or 95 % pure by volume;
— isopropyl alcohol, best commercial grade, 99 % pure;
— any mixture of the above.
Procedures for cleaning shall be generated before solvent cleaning is begun. Further cleaning or other
treatments of the joint after wire-wrapping shall not be done.
Materials and workpieces shall be handled only with clean lint-free gloves or finger cots.
4.7 Tools and equipment
4.7.1 General
Before the first production of wire-wrapped connections, the tools shall conform to the control
requirements of this subclause.
4.7.2 Cutting tool
The cutting tool selected for use shall cut the conductor wire without causing flattening of the wire. Any
tool not achieving this requirement shall be removed from the work area.
4.7.3 Insulation strippers
a) Thermal strippers
Thermal-type insulation strippers may be used on types of wire insulation for which they are suited.
Heat of the stripper shall be controlled to prevent blistering and excessive melting of insulation. Local
extraction units shall be used if thermal stripping is employed, in order to avoid part contamination or
health hazards due to resultant fumes.
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EN 50389:2005 - 10 -
b) Precision cutting-type strippers
Automatic power-driven strippers with precision, factory-set, non-adjustable cutting and stripping dies
and wire guards may be used. Precision-type hand strippers with accurately machined and
factory-preset cutting heads may be used with a caution about making certain that the die openings
for wire sizes other than that being used are masked off. The conductor shall not be twisted, ringed,
nicked, cut or scored by this operation.
4.7.4 Wire-wrapping tools
a) The wire-wrapping tools (see Figure 2) shall be power driven. The tool shall be either an electrical
tool (mains supply), or a pneumatic tool (supplied with regulated, lubricated and filtered air). It should
be fitted with a “backforce” device to prevent overwrapping defect. Hand-powered or battery-powered
wrapping tools shall not be used.
b) A wrapping tool together with appropriate rotary bit and stationary sleeve shall be assigned to each
wire gauge and terminal combination in use, and suitably marked to show the size for which it is
calibrated.
c) Refer to the tool manufacturer for appropriate selection of bit and sleeve for each wire/terminal post
diagonal combination.
d) The tool and associated accessories shall be checked for cleanliness and general satisfactory
condition at up to ×10 magnification. The extremity of the bit shall be perfectly clean and smooth
without blockages or faults. The sleeve should not have any sharp blockage in its neck, and shall be
checked manually to ensure that the bit runs perfectly in the sleeve, without any hard or rough points
of contact. Any tool not meeting the above requirements shall be removed from the work station for
repair or replacement.
e) The wire-wrapping tool shall not nick, ring, gouge, or scrape conductors, or damage the terminal post
in any way during its operation.
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A
B
C
Key
A electrical mains supply
B pneumatic
C typical design of bit and sleeve
Figure 2 — Examples of approved wire-wrapping tools
4.7.5 Unwrapping tools
When required, wrapping connections shall be detached from their terminal posts by means of special
unwrapping tools (see Figure 3).
a) Manual unwrapping tools are preferred. They are short tubular tools having an external spiral groove
and handle. A “left-hand” unwrapping tool is required to unwrap a “right-hand” wrap connection
(clockwise wire rotation from base to top of terminal), or vice versa for a “left-hand” wrap connection.
b) The unwrapping tool chosen shall be compatible with the terminal post diagonal, and shall not nick,
ring, gouge, scrape or damage the terminal post in any way.
c) It shall be checked that it is clean and that it does not have any blockages on the outside. Damaged
tools shall be removed from the work station for repair or replacement.
Figure 3 — Hand unwrapping tools
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EN 50389:2005 - 12 -
4.8 Tool calibration
a) Initial tool calibration shall be carried out to confirm that a new or repaired tool (with appropriate bit
and sleeve) is working correctly, and shall only then authorize the use of the tool.
b) First confirm that the tool meets the requirements of 4.7.4. The operator shall make 30 sample wrap
connections between the selected wire and terminal post referred to in 5.3, appropriate to the tool.
The calibration test sequence shall be as follows:
- sample 1 to 30 workmanship (see 7.2);
- sample 1 to 15 stripping force (see 7.3);
- sample 16 to 30 unwrapping test (see 7.4).
c) Recalibration shall be carried out at 12 monthly intervals thereafter or whenever the tool is repaired.
A tool-calibration record shall be kept with the tool.
d) Tool/wire/terminal certification shall then be carried out using the calibrated tool (see 4.9).
4.9 Wire-wrap process certification
a) Initial certification of each wire-wrap combination
The capability of the wire-wrap tool to produce acceptable wire-wrap connections shall be
established for each combination of tool with correct bit and sleeve, wire gauge and terminal post.
30 sample wrap connections shall be prepared with a calibrated tool. The certification test sequence
shall be as follows:
- samples 1 to 30 workmanship (see 7.2);
- samples 1 to 30 connection resistance (see 7.5);
- samples 1 to 10 stripping force (see 7.3);
- samples 11 to 20 unwrapping test (see 7.4);
- samples 21 to 26 gas-tightness test (see 7.6);
- samples 27 to 30 metallography (see 7.7).
The successful completion of all above tests authorizes spacecraft wire wrapping to commence for
the wrap combination.
b) Re-certification of each wire-wrap combination shall be carried out after the following
occurrences:
1. when production wraps fail to meet the requirements of the daily process-control tests specified
in 9.8.2;
2. at every 10 000 wire-wrap connections in a continuous programme;
3. if production is interrupted for a period in excess of 12 months. This shall ensure reliability of the
joint, as the wire and terminals may degrade during storage.
The re-certification test sequence shall be a repeat of 4.9 a), 30 sample wrap connections being
prepared with a calibrated tool.
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