0199l(2).pdf

(70 KB) Pobierz
INGENIOUS REVERSE ENGINEERING TECHNIQUES COULD ALLOW BETTER
RECLAMATION OF OBSOLETE ELECTRONIC ASSEMBLIES. IAN POOLE REPORTS.
Green issues are becoming
increasingly important. There
are naturally the issues of
reducing the amount of
greenhouse and other toxic
gasses into the atmosphere.
One area that has been of
particular importance to the
electronics industry is that of
cleaning fluids to remove the
flux from printed circuit boards
after soldering. Now many new
methods of cleaning have been
developed, thereby reducing the
pollution to the atmosphere.
However, there are many
other areas that need to be
addressed to ensure that the
overall level of the pollution of
our planet is kept to a minimum.
The amount of electronic
equipment that is manufactured
today is vast. Yet very little of it
is recycled. One of the main
reasons for this is the huge cost
of disassembly and this has
meant that many products
containing valuable components
have had to be used as landfill
or crushed so that some of the
more valuable raw materials
can be reused.
In many countries now there
are requirements to increase
the amount of electronics
equipment being recycled. In
several countries legislation is
about to hit the statute books
that will require companies
producing the equipment to take
it back for recycling. In other
countries other schemes are
either in operation or are about
to be launched.
Whatever approach is
adopted in each country,
though, the overall effect is
that the amount of electronics
equipment reaching landfill sites
will be reduced, and the amount
being recycled will have to
increase. This will require new
technologies to be developed
that will enable the recycling
process to be achieved far more
easily and cost effectively.
The idea revolves around
the fact that certain metal alloys
can be made into a particular
shape by heating them, typically
to a temperature around 400°C,
and then rapidly cooling them.
The part can then only resume
its original shape if it is re-
heated. The temperature at
which this occurs is somewhat
less than the temperature
required in the original
manufacture of the part, and
may range between about
60°C and 120°C.
Two main SMAs were used
in these investigations. The first
was Nickel Titanium (NiTi), and
the second was Copper-Zinc-
Aluminum (CuZnAl). These
operated in slightly different
ways, but the end results were
the same.
Whilst the metal alloys are
the most widely used materials,
a group of polymers also
exhibits the same properties,
and these may provide a
cheaper and more convenient
solution for the longer term.
Different materials
To help solve the problem,
the Cleaner Electronics Group
at Brunel University in the UK
has exploited the properties of a
group of metal alloys known as
shape memory alloys (SMA). In
a system called Active
Disassembly using Smart
Materials (ADSM), electronic
equipment could be made of
materials that would actively
disassemble themselves once
they were subjected to
temperatures at a given level.
In this way the cost of disass-
embly could be significantly
cut, making recycling far
more cost effective.
Temperature sensitive fasteners allow rapid equipment disas-
sembly for reclamation of reusable parts.
EPE Online, January 1999 - www.epemag.com - 192
Copyright © 1998 Wimborne Publishing Ltd and
Maxfield & Montrose Interactive Inc
New technology Updates
If these materials are used
in the manufacture of fasteners
and clips, it is possible to pass
the equipment though a heat
treatment process, often using
steam. Once this happens, the
fasteners will let go and spring
actuators can be used to push
apart the components of the
product. In this way the major
part of disassembly is for the
components to be picked out of
the equipment and sorted and
sent for re-use.
As different materials have
different temperatures at which
they return to their original
shape, it is being proposed that
fasteners could be made with
different temperatures so that a
unit could be successively
disassembled.
this. These assemblies could be
freed and reclaimed at an early
stage in the process.
reclaim a very large number of
the components.
Naturally there would be a
cost associated with the use of
the system, but with some
countries introducing penalties if
products are not recyclable, this
would almost certainly provide a
cheaper option, apart from the
advantages in being able to
reduce pollution. In addition to
this, much of the increased cost
of using the new system could
be recouped by the re-use of
the components.
More information can be
found via E-mail):
joseph.chiodo@brunel.ac.uk
or (Web)
http://
www.brunel.ac.uk:8080/~dtsrj
dc/ ADSM.html,
where Joseph
Chiodo and Prof. E.H. Billett are
carrying out the research.
Trials
A number of trials have
been undertaken, both on the
components made out of the
smart materials, and on
equipment made using the
smart fasteners and actuators.
These trials proved to be
enormously helpful. They
highlighted the ways in which
the fasteners and actuators
should be used, along with
suitable locations for them.
Further tests proved that the
sequential disassembly of
products in this manner is
feasible.
It was also shown that this
approach is possible on a
commercial basis. Until
recently, the cost of
disassembly was exceedingly
high. The majority of this was
taken up by the manual nature
of disassembly. Owing to the
fact that products were not
designed to be disassembled, it
was difficult and time
consuming to salvage any
components. In addition to this,
many components were
destroyed in the process. As a
result, it was only viable to
salvage a few high cost items or
metals and leave any others,
consigning them to landfill sites.
Using the new system, the
labor content of disassembly is
vastly reduced. In turn, this
reduces the cost of disassembly
to a level where it is viable to
Design
If a system of this nature
were employed, then
disassembly would become an
integral part of the design
process. During a typical
disassembly process the case
would separate from the main
electronics assemblies early in
the cycle. Then board-level
assemblies would be freed.
Connectors freeing themselves
as well as individual
components would follow this.
At the end of the process the
individual components would be
left and they could be easily
sorted for reclamation or re-use.
One problem might occur
with components that can be
damaged by heat. Liquid
crystals are one example of
Copyright © 1998 Wimborne Publishing Ltd and
Maxfield & Montrose Interactive Inc
EPE Online, January 1999 - www.epemag.com - 193

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin