Alloys that give good results in terms of aspect, duration of heating,
wetting properties, solder retention and resistance to humid heat are
Sn99Cu1 and Sn95Ag3.8Cu0.7. These alloys are commonly available on the
market. This list is not exclusive and other alloys may give good results.
In general tin/silver/copper base alloys are those which are most
recommended for ³reflow² flow-soldering. Recommended soldering iron is 80W
power and working temperature of the solder iron tip will be 380°C instead
of the previous 350°C in order to compensate for the higher melting point
(~30 °C) of lead-free alloys.
On a general basis, soldering is recommended for small connector assembly
volumes, it requires little amount of tooling such as a soldering iron, on
the other hand the assembly requires more time. Crimping assembly is
recommended for large volumes of cable assembly, no heat is required to make
the connection so the equipment may be used in a high temperature
environment. The electrical contact and wire are crimped together and then
inserted into the insulator, this makes it a convenient assembly process for
high contact density. On the other hand crimping requires extra tooling such
as crimping tools and positionner.
The picture here shows the assembly of the LEMO F series before placing the
heatshrink boot. When heated gently the heatshrink boot retracts and works
as a strain relief. This connector allows a high contact density (up to 64
crimp contacts in this example). The connectors were installed in 2007 in
the beampipe of the ATLAS detector at the large hadron collider at CERN
(European Organization for Nuclear Research).
The biggest advantage of fibre optics versus copper is that fibre covers
longer distances than copper. This is essential when needing to cover long
distances for industrial environment, for communication or broadcast. Fibre
also offers larger bandwidth; this means that rather than using ten coax
cables to send information, a unique fibre cable will be able to transmit
the same information, and even more. Finally, optical fibre is immune to
electromagnetic interference, meaning that the signal will not be
deteriorated by other power cables or radio frequency interference. It is
recognised that maintenance and repair of the cable / connector
infrastructure is of primary concern to users. Yes, fibre optic contacts do
need to be inspected and kept clean. The first rule is ³inspect the endface
and if it isn¹t dirty don¹t touch it². If the fibre is dirty then it needs
to be cleaned. This can be done with minimal tooling required.
In 2008, LEMO China is equipping the Beijing Olympic Games for their
intra-venue communication. ³LEMO is supplying a complete solution including
connectors, cable, cable spool and termination. The chosen solution offers
up to 10 fibres per connector and allows saving time during the setup and
decreases the complexity of the cabling on site², said David Ge from LEMO
Trading (Shanghai).
Cable assembly
The cable assembly depends essentially on the application. Will the
connector and its associated cable be manipulated over and over again by an
operator? Does the assembly need to be watertight, does it need to answer a
specific military standard, must the cable be flexible and will it encounter
constant motion such as on a pick and place machine? Some of the following
cable assembly solutions may answer these questions.
Assembly techniques may involve hot melt technology, overmolding and cable
labelling and depend on the type of cable: high voltage cable, coaxial cable
(RG 58 C/U, RG 174 A/U, RG 316 B/U, etcŠ), fibre optic cables for
audio/video (standard SMPTE 311M), or multiconductor cables.
Customer focus
LEMO's skilled technicians build and test assemblies to the customer¹s
specifications. Customers can receive the same high quality cable
assemblies that they expect from LEMO connectors. LEMO cable assembly
feature: electronic, fibre optic, and hybrid connections, 100% testing of
all assemblies, small to large volume capacity and overmold capabilities.
Some of the larger subsidiaries are equipped with highly modern and special
constructed equipment such as stripping equipment with rotating knives,
clipping robot, hydraulic crimp facility, test equipment etc.
In LEMO Germany, a 100% inspection test ensures a zero defect cable
assembly. The test allows to control the quality output and to pro-actively
improve the termination of the harnesses. A final control is done by
computer to achieve a 100% quality before packaging and shipment.
Serge Buechli is Product manager , LEMO S.A , Switzerland
www.lemo.com
Enter 29 at www.engineerlive.com/ape