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TRANSCRIPT
Integrated Circuits Towards Reducing E-Waste:
Future Design Directions
Torsten Lehmann and Tara J. Hamilton School of Electrical Engineering and Telecommunication
The University of New South Wales
Sydney, Australia
Email: [email protected]
Abstract-Electronic devices and systems are not usually environmentally friendly. Large amounts of energy and hazardous substances are required for their production, and discarded products end up in landfills; trends that are exacerbated by fast moving advances in consumer electronics. In this paper, we argue that the most promising way to reduce the environmental load of consumer electronics is to move towards reusable electronic components; components that are reliable, self-testing, and, most importantly, flexible in a manner that allow electronic systems to be build for a wide range of applications using only a few highly reconfigurable integrated circuits.
Index Terms-Electronics Waste Reduction, Green Circuits and Systems, Reusable Electronics, Reconfigurable Integrated Circuits
I. INTRODUCTION
It is estimated that between 20 to 50 million tonnes of
electronics waste (e-waste) is being produced world-wide
every year [1]. Last year approximately 234 million electronic
items were dumped in Australia representing an increase of
21 % from 2008 [2]. The dramatic increase in e-waste can be
attributed to fast-paced technological advancements and the
desire (and sometimes need) to upgrade computers, mobile
phones, TV s and so on.
W hile some changes in e-waste handling and regulations
are emerging, a substantial amount still ends up in landfills:
in the United States, for instance, about 80% of e-waste was
dumped in the early-to-mid 2000s [3]. This is concerning
particularly because e-waste contains many toxic substances
(such as lead, cadmium, mercury, and arsenic) and can lead to
serious pollution. Recycling the larger parts of e-waste (such
as cables, enclosures, and evacuated tubes) is relatively simple.
Printed circuit boards (PCBs) with their mounted components
are harder to recycle. Usually they must be ground up, burned
or acid washed in order to salvage raw materials (such as gold,
copper and aluminium) [4], [5]. There have been few attempts to salvage electronic com
ponents (or PCBs) such as sophisticated integrated circuits
(ICs or chips) for reuse; components may be obsolete or
worn out, but also they are simply difficult to remove from
modern PCBs once mounted, without being damaged (e.g.
[6], [7], [8]). This is unsatisfactory from an environmental
point of view: firstly, waste products from PCB recycling
contains the toxic substances not salvaged by the process.
Secondly, the embodied energy in integrated circuits is very
high - for instance, a 2002 study estimated the embodied
energy of a typical small integrated circuit (a 1.2 cm2, 32MB
memory chip) to be 26 MJ, requiring 2.3 kg of fossil fuel for
its production [9].
Thus, in this age of global climate change and increasing
demand for electronics goods, we see an emerging need for
moving towards electronic systems that can, at least in part,
be reused in order to lower their environmental burden. To
enable efficient electronics reuse, the technical issues above
need to be addressed.
Power converters for windmills or photovoltaic panels make
extensive use of power electronics. Such electronics, by its
very nature, has a low environmental burden because of their
aid in generating renewable energy. However most electronic
systems, e.g. consumer electronics, does not fall in this cate
gory; most electronic systems are users rather than providers of
energy. For the purpose of this work, by "electronic systems"
we understand "energy using" electronics.
In this paper, we discuss the challenges that lie ahead for
electronics circuits and systems designers if the electronics
industry is to move away from having an ever increasing
environmental load. In section II, we argue the case for the
future design of reusable electronics; in section ill, we discuss
the challenges of reusable electronics; in section IV, we argue
that further research into reconfigurable electronics is required;
in section V we summarise the future design directions for
reusable electronics; finally, in section VI, conclusions are
drawn.
II. REUSABLE ELECTRONICS
Lowering circuit power dissipation is often brought forward
as a primary approach to reducing the environmental burden
of electronic systems. For systems that use large amounts
of energy this is a valid avenue. However, lowing power
dissipation can arguably lead to an increase in environmental
burden: lowering power dissipation in a system may enable
it to be operated from a small battery and be portable, hence
increasing the system's market penetration and environmental
burden (e.g. the mobile phone); lowering the power dissipation
further enables increased functionality of the system, hence
creating consumer desire to upgrade their system at an envi-
978-1-4244-6878-2/10/$26.00 ©2010 IEEE 469
ronmental cost (e.g. the mobile phone ).1 Further, with the typical short life of todays complex
electronic devices, their embodied energy is typical much
higher than the energy they use - e.g. Williams et al. [9] found that only 27 % of the energy used over the life of a
32 MB RAM chip was during its operational life; the rest
was associated with manufacturing. In addition to the pure
energy considerations, the manufacturing of integrated circuits
require a large number of hazardous chemicals; their use being
a potential risk to workers and the environment.
Thus, we see is a very strong incentive to reuse electronics
components whenever possible. We see this as the approach
towards reducing the environmental burden of electronics with
the most potential; an approach which is radically different
than reducing power dissipation of devices. Today, there have
been only very few attempts at reversing the trend of "throw
away" electronics (e.g. [12]). While there is seemingly an inexhaustible appetite amongst
consumers for the latest electronic gadget, there is much scope
for reusing electronic components. This can be understood
by noticing that there is a substantial difference between
the computational (and other) requirements and the electron
ics in different applications. Personal computers have more
computational power than DVD players; DVD players have
more computational power than washing machines, and so
on. Also, as electronics become smaller and cheaper, even
more types of appliances are fitted with electronic control
systems ("intelligent" appliances), normally starting towards
the lower end of computational requirements. Oliver et al.
[13] use the term "technology food chain," and explain how
microprocessors could be reused, moving down the food chain
between technology generations. If designed so that they can
be reconfigured for different applications, this can apply to
most components such that components fitted in a DVD player
in one generation (say), move down the food chain and will
be fitted in a washing machine (say) in a following generation.
Thus, there is much scope for reconfigurable, reusable
electronic systems that can be reconfigured to perform dif
ferent or varied functions for a particular application or
for different applications (e.g. the "technology food chain").
Such reconfigurable, reusable systems could significantly alter
future electronic design paradigms and significantly improve
the burden of the electronics industry on the environment.
III. CHALLENGES
There are many challenges that have to be overcome before
electronic devices can be reused in a sustainable and efficient
manner:
A. Obsoleteness
If an application requires the full capabilities of the very
latest electronic technology to operate, earlier generation com
ponents can not be recycled for that application. Most appli
cations do not require this, however, and their obsoleteness
1 Note that both the authors have extensive industrial and academic experience in low-power circuit design, primarily in bio-inspired systems and implantable electronic systems (e.g. [ lOj, [11])
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Fig. I. Typical signal flow in electronic system.
lie in their function rather than in the underlying technology;
for such applications, if components and sub-systems can be
reconfigured to perform a different function, the sub-systems
can be reused.
The generalised purpose of electronics systems is to sense
signals in a physical domain, manipulate these signals and
apply them to an (often different) physical domain as indi
cated in Figure 1. Over the last two decades, reconfigurable
digital components, notably Field-Programmable Gate Arrays
(FPGAs), e.g. [14], [15], have matured to a stage where
they are used extensively for prototyping and increasingly
in products. Reconfigurable analogue components are more
sparsely reported; most of these address signal processing only,
e.g. [16], [17], [18], [19], though a few also include sensor
interfacing [20], [21]. Reconfigurable support functions, such
as power transfer and communications are the last functions in
typical electronic systems that must be made configurable in
order to enable the reuse of electronic sub-systems. From an
electronic circuit design point of view, the design of suitable
reconfigurable circuit components is the first challenge for
reusable electronics.
B. Wear-out
Electronic components wear out with use or stress; typical
consumer electronics have an expected life of about a decade.
Reusable electronics need to have an expected life that equals
the sum life of a number of products. Thus for successful
employment of reusable electronics, it is critical that such
components are designed for a long life, rather than for
optimising performance or power dissipation (such as reducing
voltage and temperature stress and having redundant circuit
functions, e.g. [22]). Note that such reliable systems are
commonly used in demanding applications such as military,
space or medical applications; the design practices just need
to be incorporated in consumer electronics.
When building a new product with a reused part, it may
become the responsibility of the product manufacturer (rather
than the part supplier) to ensure good parts are used. Hence,
we foresee reusable electronic components needing to include
automatic, thorough component testing (such as boundary scan
systems and built-in self-test, e.g. [23]). From an electronic
circuit design point of view, built-in self-test is the second
challenge for reusable electronics.
C. Unmounting
While sockets can be used to facilitate removal of compo
nents from PCBs, they make equipment bulkier and, in some
applications, severely reduce performance or prevent opera
tion. Processes to remove large surface mount components
Fig. 2. Conceptual block diagram of typical FPGA based electronic system.
Fig. 3. Conceptual block diagram of reusable electronic system.
from PCBs (e.g. [6]) should be in place for the adoption of
reusable electronics. Alternatively PCBs could be engineered
as modules with well defined interfaces and functions such
that entire PCBs could be reused.
D. Non-technical challenges
There are many non-technical issues that have to be ad
dressed before widespread reuse of electronic components
can be realised; for instance standardisation issues, economic
issues, logistical issues and manufacturing issues, e.g. [24], [25]. However the technology first has to be in place with
circuit components designed specifically for reuse.
Thus, from a circuits and systems design point of view, we
see the primary challenge to achieve electronic components
that are well suited to reuse to be the design of flexible,
reprogrammable components for typical circuit functions that
are not currently so designed.
IV. RECONFIGURABLE CHIP S
While the purpose of electronic systems is to manipulate
and transfer signals between physical domains, a number of
support functions are required for system operation - for in
stance energy sources, power supplies and power distribution,
voltage references, oscillators, bias control for sensors, drivers
for actuators, and communications hardware, see Figure 2 and
e.g. [26]. Complex generic components (such as field-programmable
gate arrays, field-programmable analogue arrays, micro
controllers, and digital signal processors) are relatively easy
to reuse for different applications because the functions
they perform are determined by digital configuration data
(or firmware) that can be uploaded to the component. This
updating of configuration data, however, requires a suitable
interface though, despite this (see [13]), such components are
considered reconfigurable.
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Application specific hardware for the physical interfaces -
typically power supplies, sensor biasing, drivers and commu
nication systems - are harder to reuse because the functions
they perform are determined by their component types and
interconnecting wires. The reason that current reconfigurable
electronic circuits address the signal processing rather than the
required physical interfaces is that the physical requirements
to the latter are highly application specific (operating at vastly
different voltages, currents, and frequencies, for instance) and
require electronic components suited to each application - or
reconfigurable circuits of extraordinary flexibility.
Thus to facilitate practical reuse of electronic systems, the
physical interfaces must be designed in a less application
specific manner; reconfigurable circuits need to be devised for
these functions.
Assuming complete PCBs are designed for reuse, it would,
in principle, be possible to implement reconfigurable, reusable
electronics using largely existing electronic components. There
are, however, a number of compelling reasons why such
electronics should be implemented primarily on integrated
circuits (ICs or chips): Firstly, due to their micro-scale, com
ponents on ICs are much smaller than their PCB equiva
lents; this is critical as general-purpose, reconfigurable sub
systems are more resource intensive than custom hardware
(Le. some hardware is dedicated to reconfiguration rather than
function, and some hardware will be unused; compare FPGAs
vs. Application-Specific Integrated Circuits). Secondly correct
function of components need to be verified before they can
be reused: specific hardware for self-test should be included,
further increasing the hardware overhead on the reconfigurable
system. Thirdly, on-chip integration of functions increases
system reliability, which is critical when the expected useful
lifetime of the system increases with reuse. Finally, when
PCBs are not reused as whole, the need to unmount fewer
components would increase the likelihood of function reuse
- note that some work on environmentally friendly PCBs
haven been reported, e.g. [27], thus PCB reuse may be less
critical than component reuse.
Therefore, we envisage reusable electronic systems to look
somewhat like Figure 3: having fewer, more configurable,
more highly integrated components than current systems.
Components such as energy storing elements and application
specific sensors and actuators will still need to be off-chip; the
challenge from a circuits and systems design point of view is
to integrate everything else on chip - and to determine which
functions to best to integrate on the same chip. These concepts
are embodied in our idea for a Field-Programmable Electronics
Support System (FPESS).
V. DESIGN DIRECT IONS
In summary, in order best to address the environmental
burden of electronic systems, design focus should be on
reusable components; such components need to:
• be very reliable - component failure rates should be long
enough such that they can be used over the lifetime of
several systems;
• be self-testing - components should be able to thor
oughly test themselves without the aid of the component
manufacturer in order to qualify for reuse;
• be highly integrated - in order to avoid having to
unmount a large number of discrete components and to
include reconfigurability and self-test in a way that is
transparent to the system designer;
• be highly reconfigurable - in order to be useful in a
large variety of applications.
All of these requirements are feasible when design strategies
are targeted towards reuse and reconfigurability. For instance,
both reliability and self-testing are integral parts of chips
manufactured for implantable medical devices. Such devices
must maintain functionality for the lifetime of the recipient.
Thus, by employing design techniques used in the medical
device industry, for instance, reliability over an extended
lifetime is possible.
Chips with a large number of integrated components (e.g.
inductors, diodes, etc.) are possible especially when silicon
technologies such as silicon-on-sapphire (SOS) are utilised;
although this is not imperative. While reconfigurability will
come at the cost of greater area and digital programming com
plexity (and possibly reduced performance), reusable chips
will have the potential for having a much reduced environ
mental burden over their lifetime.
VI. CONCLUSION
In this paper, we discussed future design directions for
electronic systems with a reduced environmental burden than
what is currently practiced. We argued that it is not the power
dissipation of employed systems that should be the primary
technology driver for environmentally friendly electronic sys
tems; rather it should be the total environmental load of the
systems ("from cradle to grave") - as integrated circuits have
large embodied energy and as they require large amounts
of resources to manufacture, prolonging the useful life of
the integrated circuits is a most promising avenue towards
reducing their total environmental load. We thence argue
a need towards the use of reusable electronic components.
From a circuits and systems design point of view, this means
designing reconfigurable integrated circuits, for functions not
currently designed thus, and designing system partitioning in
such a manner that systems can be implemented using few,
smart components each having a long life and extensive built
in self-test. Only energy storing components and application
specific sensors and actuators should be left off chip.
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