CMEMS Fabricated in LTCC

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C-MEMS Fabricated in LTCC

• Presented By Don Plumlee

February 14, 2003
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Overview

• MEMS
• Overview of LTCC
• Materials
• Typical Uses
• LTCC Fabrication Process
• Route Layer Patterns
• Fill Vias/Screen Print
• Laminate the Stack
• Co-Fire
• Inspect
• Ion Mobility Spectrometer Design/Development
• IMS Schematic
• IMS Model and Segments
• Future Goals

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MicroElectroMechanical Systems (MEMS)
LabCD-DOS developed by Gamera Bioscience in
Boston http//www.biomems.net/ResearchDevelopment/
microfluidics.htm
Micro-machine fabricated by Sandia
Labs http//mems.sandia.gov/scripts/index.asp
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Low Temperature Co-Fired Ceramics (LTCC)

• LTCC is a Glass/Alumina mixture that sinters 900C Low Temperature
• The Ceramic substrate and embedded elements are
  fired simultaneously Co-Fired
• Material in the Green state is composed of
  Glass, Ceramic and Organic binder
• Raw materials delivered as a flexible sheet
  called Green Tape

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LTCC Advantages

• Process
• Parallel processing (High Yield/Quality)
• Single sintering step for all materials (Co-fire)
• Inexpensive
• Quick Time to Market
• Electrical
• Integrated Passive Components (R, L, C)
• High circuit density (3D Structure)
• Dielectric Stability at wide range of
  frequencies.

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More LTCC Advantages

• Thermal
• High ambient temperature resistance
• Better thermal conductivity than PCBs
• Close match to semiconductor Thermal Coefficient
  of Expansion.
• Mechanical
• Machineable (Drill, Cut, Punch) in Green State.
• High Mechanical Strength w/ Multi-layer
  Structure.
• Hermetically-sealed Package

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LTCC Fabrication Process
From Thales Microsonics LTCC Design Guide
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Typical LTCC Applications

• Chip Packaging
• Integrated Circuits
• Antenna Arrays
• Waveguides
• Bluetooth Microwave Devices
• C-MEMS

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C-MEMS Fabrication Process

• Rough Cut Blank Sheets
• Route/Drill Layer Patterns
• Fill Vias
• Screen Print Conductors and Resistors
• Laminate the Stack of Layers
• Co-Fire the device
• Inspect

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1. Rough Cut Blanks

• Each layer is rough cut from a roll of Green
  Tape.
• Layers are cut into 100mm x 100mm squares.
• Process performed using an EXACTO knife.

Cutting Layers
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2. Route/Drill Layer Patterns

• Registration Holes, Vias and Cavities are drilled
  in each layer using CNC Milling Machine
• 3D Solid Models are created in Solid Works.
• The routing pattern for each layer is extracted
  as a 2D file and converted to a milling pattern
  using GerbTool and ISOCAM software.

Bungard CNC Milling Machine
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3. Fill Vias

• Vias are filled with DuPont 6141 Conductor Paste.
• Currently done manually using a plastic stencil
  and brush.

Via Filling
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4. Print Conductors/Resistors

• Circuits are printed on each layer with DuPont
  6145 Conductor Paste.
• An AUTOROLL M25 screen printer is used to print
  the pattern.
• Screens are developed by transferring the
  conductor pattern from the 3D model section using
  photo-imaging.
• Screens are aligned to substrate visually using
  registration holes.

Screen Printing
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5. Laminate the Stack

• The sheets are collated and stacked in a
  Lamination Jig.
• The stack is pressed for 10 minutes at 70C and
  3000psi.
• A PHI SPWR220 press is used for lamination (40
  ton capacity).

Lamination Press
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6. Co-Fire the Device

• The laminated stack is Co-fired in a laboratory
  oven with a Eurotherm controller.
• _at_ 350 C, binders burned off.
• _at_ 850 C, sintering occurs

Furnace Profile
Laboratory Furnace
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7. Inspect and Test

• Samples are examined under an Olympus SZ40
  microscope for defects.
• Functional Testing will be performed on each
  device as required.

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C-MEMS Projects

• Current
• Capacitive Pressure Sensor
• Ion Mobility Spectrometer (IMS)
• Electro-Chemical Cell
• Future
• Micro-Combustor
• Micro-Turbine
• Micro-Fluidic Systems (Lab on a Credit Card)
• P3 device in LTCC (Washington State Univ.)

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EPA Sensor Project

• Sponsored by the EPA
• Collaboration between Civil, Electrical,
  Mechanical Engineering and Chemistry (BSU and
  WSU)
• A sensor is inserted into the soil using a
  Direct-Push style ground penetrometer.
• The sensor analyzes groundwater chemical
  concentrations periodically.
• Data is broadcast and collected from an array of
  sensors in real-time.
• Result Accurate Time/Space knowledge of chemical
  migration in groundwater

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Sensor Requirements

• Detect chemical concentrations in groundwater
• Sensitivity
• Accuracy
• Operate in a down-hole environment for multiple
  years
• Reliability
• Chemical Resistivity
• Small Diameter

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IMS Schematic X-section
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IMS Assembly Components

• Aperture/Collector
• Drift Tube
• Tyndall Gate
• Ionization Tube

Drift Gas Flow
Ion Flow
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IMS Model Assembly
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Aperture/Collector Segment
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Drift Tube Segment
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Tyndall Gate Segment
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Ionization Tube Segment
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Future Goals

• IMS
• Complete Fabrication of a device
• Test IMS at WSU Analytical Laboratory
• Optimize design
• Finish Thesis
• Optimize fabrication process with new techniques
• Continue to pursue additional C-MEMS devices and
  applications using the LTCC process.