World-to-chip Socket
Last update: 2003/04/15
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World-to-chip Socket Last update: 2003/04/15 |
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@ A WORLD-TO-CHIP SOCKET FOR MICROFLUIDIC PROTOTYPE DEVELOPMENT Summary This paper reports a prototype for a standard connector between a microfluidic chip and the macro world. This prototype is the first to demonstrate a fully functioning socket for a microchip to access the outside world by means of fluids, data and energy supply, as well as providing process visibility. It has 20 channels for the input and output of liquids or gases, as well as compressed air or vacuum lines for pneumatic power lines. It also contains 42 pins for electrical signals and power. All these connections were designed in a planar configuration with linear orthogonal arrays. The vertical space was opened for optical measurement and evaluation. The die (29.1 mm x 27.5 mm x 0.9 mm) can be easily mounted and dismounted from the socket. No adhesives or solders are used at any contact points. The pressure limit for the connection of working fluids was 0.2 MPa and the current limit for the electrical connections was 1 A. This socket supports both serial and parallel processing applications. It exhibits great potential for developing microfluidic system efficiently. 1.
Introduction With the development of micro-electro-mechanical systems (MEMS), microfluidic applications have increased in importance since the 1990s. The reason for the continual interest in this field is its obvious applications. These include the need from biological, pharmaceutical and medical applications, to detect very dilute solutions of analytes in ultrasmall volumes. The need for sample manipulations in small volumes, for chemical analysis and chemical synthesis, is also of great importance. The applications in space technologies and semiconductor fabrication are also very interesting. There
are gaps between existing technologies and particular applications. For example,
capillary electrophoresis may require the samples with volume of only several
nanolitres. However, with the restriction of transportation, the sample
preparation should be in the order of microlitre or more. Most parts of the
sample are discarded as waste. Not surprisingly, a great deal of effort has been
devoted to integrate the functions of sample pretreatment, separation and
detection onto one chip. Until now, research
activities focused on the
developments
of functional devices.
Methods
for creating networks of microchannels are well established in
silicon, glass and polymeric substrates, using etching or molding processes. PZT-actuated
micropumps and micromixers have achieved excellent performance
and various microsensors have also
been reported. These have been well reviewed by Manz et al. [1, 2].
As commercialization of MEMS and microsystems gains
momentum, product packaging has
also gained increasing attention from within
the industrial
and research communities. Compared
with the numerous publications on functional microfluidic devices, few
approaches on packaging of fluidic MEMS devices have been reported [3, 4]. These
approaches mainly concern the input and output (I/O) of working fluids. The I/O
of electrical power and signals are not supported. Packaging
has been a major
stumbling block in capitalizing the full market potential of microengineering
products. Packaging technology breakthroughs are a critical
element for continuous growth of microfluidic research and
applications over the
next decade. Ink jet printing technologies is a good example. The ink supply and electrical supply are well arranged in
printing head. Ink jet printers have already obtained considerable
success in commercial as
well as industrial applications.
Commercial micropumps [5]
and microvalves [6]
have already appeared in packaging with both fluidic and electrical
interconnections. However, their packagings are permanently sealed and
invisible. The
success of microfluidic research and its
extension
into
commercial products depend on delivering
the innovations in the following key technologies: Design,
Fabrication,
Packaging, and
Testing.
In this paper, the focus has been on packaging technologies.
1.1.
Importance of packaging technology As with integrated circuits, high performance MEMS devices cannot work independently. They needs adequate fluidic transportation, power supplies and data communications with peripheral devices. (1)
Systems
considerations Monolithic integrated microfluidic systems, similar to current LSI, were expected at the beginning of microfluidic research. But at its infancy, hybrid systems are still the most viable approach. Hybrid systems give a practical means to circumvent compatibility problems during fabrication processes. Packaging technology is one of the key elements in the development of hybrid systems. (2)
Reliability considerations Reliability is important for commercial products, as well as for proof-of-concept prototype development. Without a proper consideration of packaging, even prototypes might be hindered by trouble from factors such as electrical contact resistance; noise; optical deformation; clogging and leaks; and thermal or physical stress. (3)
Miniaturization
considerations In most cases, the physical size of an IC or MEMS device is dwarfed by the size of its final package. A die size of a few microns can end up in undesirably bulky packages, with overall dimensions in centimeters. Consequently, some of the benefits of miniaturization are diminished due to inadequate packaging [7] . (4)
Cost considerations The cost of packaging cannot be neglected. For example, the cost of packaging micro pressure sensors can vary from 20% to as high as 95% of the productfs total cost [7] . A packaging design compatible with automatic processes will tremendously decrease the assembling cost. 1.2. Challenges in packaging
fluidic MEMS Comparing with IC packaging, fluidic MEMS packaging increases the complexity. It has to consider:
It
is very important for the development of MEMS packaging to learn from
microelectronic technologies and methodologies.
And the I/O of micro scale working fluids are the most
attractive challenge to researchers and engineers working on fluidic
MEMS packaging. A
socket for
connecting fluidic
MEMS device to the
macro world is presented.
It is the first to report the supply general-purpose interconnections for
fluidic MEMS development at the proof-of-concept stage. This socket supplies
full I/O interfaces
for the transportation of fluids, data and energy. This
research will increase the development speed greatly,
by saving time for packaging design, assembling and testing. The socket mounted
with a micromixer array
is shown in Fig. 1. 2. Materials and methods 2.1. Design of working fluidic connections
4. Concluding remarks Figure 1. Socket
mounted with a 5-micromixer array chip. The volume of each mixing chamber is 0.7
ml and the
silicone tube pitch for I/O of working fluids is 2.5 mm. Both working fluidic
and electrical connections were adhesive/solder-free. Figure 2. The side view
schematic of the lead guide for the working fluidic connection (upper). At the
bottom is the photograph of the part of the lead guide (from right side view of
upper schematic). The extended silicone tubes serve as O-rings, to seal the flow
channel ports on fluidic chips. Figure 3. Front (left) and
back (right) view of the socket. At the top of the socket, 1.27 mm pitch springs
were arranged for electrical connection with the die. At the back of the socket,
2.54 mm pitch pins were arranged for electrical connections to the outside
world.
Figure 4. Backside view of
a (8+1) micromixer array chip. The chip is
a Si/glass structure
with dimensions of 29.1 mm x 27.5 mm x 0.9 mm.
Electrical lead pads were formed directly on the silicon substrate, to connect
with piezo-ceramic actuators.
Figure 5. A fluidic
circuit was set up on an electrical breadboard using the sockets. The micromixer
array in Fig. 1 was serially connected with a flow rate regulator module. The
silicone tubes help to smooth out the flow pulse before it entres the mixing
chamber. This fluidic circuit was highly flexible and reconfigurable in terms of
electrical and working fluidic connections. Any functional module could be
easily added/removed. For a carbon copy of the paper, email your airmail address to : Zhen.YANG@aist.go.jp |
