Case Study
Wire Harness Conversion to Flexible Circuit
Executive Summary
This Case Study describes the conversion of a discreet
wire harness to a flex circuit harness for the purpose of
providing the user with a lighter, smaller, more reliable and
economical interconnect system that is ultimately more
aesthetically pleasing.
Before
Challenge
A Midwest defense contractor was experiencing
quality and delivery issues with a discreet wire harness
used to interconnect several modules of a battlefield
communications system. The quality issues were relative
to wiring errors and bundle pinching during installation.
The harness was bulky and difficult to install. The lead time
was typically 16 to 20 weeks for the wire harness. The user
was looking for a solution which would provide ease of
installation while eliminating wiring errors, all in a shorter
lead time.
Solution
Vulcan Flex Circuit Applications Engineers proposed a flex
circuit harness approach, complete with etched signals and
corresponding shield layers – both solid and cross-hatched
copper. The item was costed at a Unit Price roughly $250
less than the wire harness version and with an overall lead
time of only 8 weeks.
Vulcan Flex Circuit Corporation
6 George Avenue
Londonderry, NH 03053
Tel: (603) 883.1500 Ext. 2123
Fax: (603) 883.7919
www.vulcanelectric.com
After
Instruction/Clarification for Designer
Wire Harnesses are used in almost every piece of defense
hardware to interconnect circuit boards within a system and
to connect systems to each other. They are used to carry
digital signals, analog signals, power and ground. In some
cases the signal integrity is very critical – very “clean” highspeed signal. Wire harnesses are made with individual wires
which are hand prepared (cut and stripped) and soldered
to the connector as required. This requires a great deal of
hand labor and is very susceptible to wiring errors if one
or more of the wires (often all the same color) is soldered
onto the wrong pin. Additionally, the wire harness tends to
be very bulky and relatively heavy for the space it utilizes.
The bulkiness often reduces critical air flow (needed for
electronics cooling) within a system (box). The weight can be
an issue in certain applications where this is critical: space,
missiles, un-manned vehicles, man-packs. Wire harness
technology has not changed significantly in 50 years and the
items are generally considered a low-tech adjunct to hightech electronic systems.
A Flex Circuit Harness is a replication of this same
interconnect concept, but utilizing circuit board print and
etch technology to create the wiring patterns on flexible
substrates. This results in a much lighter and smaller (thinner)
harness. Since flex circuit/harness fabrication is highly
automated the items are often much less expensive than a
similar wire harness.
Cost reduction is a paramount concern for the DOD at this
point in history. The Defense Budget will no doubt experience
cuts in coming years due to general economic pressures.
Additionally, the DOD needs to continue to fund new, hightech – and very expensive - solutions for use in the new
“urban-warfare theater”. Wire harnesses represent a very
good opportunity to enjoy such cost reductions by employing
modern technology solution to a traditionally low-tech item.
Summary
The Contractor is now enjoying a readily available item
which is much lighter and smaller and consequently
installs very easily without “pinching.” The wiring errors
are completely eliminated with the use of repeatable tested
flex circuits. The item is now a more robust and reliable
interconnect solution and the cost savings are a very
welcome bonus to the Program Office.
Vulcan Flex Circuit Corporation
6 George Avenue
Londonderry, NH 03053
Tel: (603) 883.1500 Ext. 2123
Fax: (603) 883.7919
www.vulcanelectric.com
Project
The Vulcan Flex Circuit Technology Team began work on
converting the discreet wire harness into a printed and etched
flex circuit construction.
Modeling – the item had to be modeled to determine
approximate size.
Mock Up – a mechanical representation of the item was
fabricated, made from the anticipated materials and of the
anticipated shape and size for a system “fit check.”
Conductor Conversion – all wires – signal, power, ground and
shield – were calculated for conversion to flat etched conductors.
Gerber File Creation – CAD Gerber files were created to represent
the wiring pattern of the signals and their corresponding shields,
including power and ground requirements. The Gerber files were
photoplotted into working films.
Connector Conversion – all connectors were converted from
“crimp-style” to “PC tails.”
Flex Fabrication & Test- the flex circuit was fabricated and tested
as a typical IPC-6013, Class 3 item.
Harness Assembly & Test – the connectors were hand assembled
and soldered per J-STD-001, followed by encapsulation (potting).
Mating connectors were used to create a test harness with which
the item was tested for continuity and isolation.
Installation – the completed Flex Harness was easily installed
into the communications system.