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Rolltronics Corporation
Flexible Thin Film
Micro-Switch Backplane Arrays
Dr. Nicholas F. Pasch
Dr. John Fenn - Presenter
Rolltronics Corporation
Flexible Thin Film
Micro-Switch Backplane Arrays
Dr. Nicholas F. Pasch
Dr. John Fenn - Presenter
Rolltronics Corporation Overview
IntroductionIntroduction
q FPDs dominate the display market
q Active-matrix LCD displays are a mature industry
q High TFT manufacturing costs
q Limited scalability of TFT display backplanes
q New display technologies such as OLED, EL, and e-paper need low-cost backplanes
Transistor array
The Search for the Perfect BackplaneThe Search for the Perfect Backplane
q Display technologies are constrained by TFTs
q Most researchers try to transfer TFTs to plastic§ Sony: mechanical transfer
§ Philips, Rolltronics: direct deposit onto plastic
q Or conventional silicon MEMS § Dr. Esashi, and others
q However, still tied to silicon equipment, processes, and costs
FASwtch™ An Active Matrix SolutionFASwtch™ An Active Matrix Solution
Unconventional materials (thin film plastics)
+Unconventional manufacturing methods
(roll-to-roll production like flex circuits)
= Flexible Active Matrix Mechanical Switch Arrays
+ =
Active Matrix - DefinedActive Matrix - Defined
q Individually addressable pixel elements
q Illuminated for most of the display scan cycle
q Non-linear response to scan voltages
q No cross-talk between the pixels
FASwitch TechnologyFASwitch Technology
How does FASwitch work?q Start with two layers of plastic:
§ Blue layer: thin and flexible
§ Gray layer: relatively thick
FASwitch TechnologyFASwitch Technology
How does FASwitch work?q Start with two layers of plastic:
§ Blue layer: thin and flexible
§ Gray layer: relatively thick
q Deposit copper (or aluminum) on each layer
FASwitch TechnologyFASwitch Technology
How does FASwitch work?q Start with two layers of plastic:
§ Blue layer: thin and flexible
§ Gray layer: relatively thick
q Deposit copper (or aluminum) on each layer
q Print an insulating spacer and laminate the layers
FASwitch TechnologyFASwitch Technology
How does FASwitch work?q Start with two layers of plastic:
§ Blue layer: thin and flexible
§ Gray layer: relatively thick
q Deposit copper (or aluminum) on each layer
q Print an epoxy spacer and laminate the layers
q Create electrostatic attraction between the layers
q The blue layer flexes until it touches the gray layer
FASwitch TechnologyFASwitch Technology
How does FASwitch work?q Start with two layers of plastic:
§ Blue layer: thin and flexible
§ Gray layer: relatively thick
q Deposit copper (or aluminum) on each layer
q Print an epoxy spacer and laminate the layers
q Create electrostatic attraction between the layers
q The blue layer flexes until it touches the gray layer
q This forms an ON switch at that point in the array
q The contacts stay closed until the voltage is removed
Technology: The Universal SwitchTechnology: The Universal Switch
As a Universal Switch, FASwitch can:
q Switch either AC or DC
q Switch high or low voltage
q Be a momentary or a latchedswitch (bi-stable)
q Scale from 70um to 70mm
q Drive voltage- or current-driven devices
q Work with just about any display technology
FASwitch: Layer AFASwitch: Layer A
Layer A:
Rigid layer next to the display media
q Columns of electrostatic plates, plus contacts and vias
FASwitch: Layer BFASwitch: Layer B
q Layer B: Insulating spacer layer
q Deposited onto Layer A
q Defines the perimeter of the cell/pixel
FASwitch: Layer CFASwitch: Layer C
q Layer C: flexible membrane layer
q Rows of electrostatic plates, plus contacts
q Flexes to touch the contact on Layer A
Latching SwitchLatching Switch
q Novel electrostatic plate structure
q Power is transferred directly to display layer
q Cell can latch ON when selected
q Latches to keep the pixel ON indefinitely
q Does not require refreshing!
Technology: BackplanesTechnology: Backplanes
For display backplane applications:
q FASwitch turns on 1 pixel in the display
q It latches ON, until it is told to turn off
q This creates a black dot on the display
q The black bar in the animation represents one black pixel, as seen from the side
FASwitch: Powering the DisplayFASwitch: Powering the Display
q 3 Voltages are supplied to the array:
§ Row Select Voltage ð Layer C (flexible layer)
§ Column Select Voltage ð Layer A
§ Latch/Display Voltage
q Column Select protocol for scanning the array
q Electrical connection between the Latch/Display Voltage and the Display media
Switch “Pull-in”Switch “Pull-in”
q Electrostatic attraction displaces the flexible membrane 1/3 of the distance to the fixed plate
q Flexible plate snaps to the fixed plate
q Electrostatic force is 1/r2
q Mechanical spring force is linear
q Two benefits:
§ Pull-in behavior is non-linear with voltage.
§ Switch response has a significant hysteresis.
ManufacturingManufacturing
q Established flexible printed circuit processes
q Roll-to-roll deposition, patterning, vias, etc.
q R2R is less expensive and more productive than silicon TFT-on-glass tools
q FASwitch production in widths up to 1 meter to start
q Size of FASwitch array can be
LARGE!
Manufacturing Advantages Manufacturing Advantages
q FASwitch cells can be same size as the pixel
q Improved registration tolerance
q Large electrical contacts: easier registration, looser tolerances, broader “guard bands”
q Less costly, automated manufacturing steps
q High production yields
Design VariationsDesign Variations
FASwitch designs to fit various product applications:
Design Pixel Size (um) Manufacturability
1 600 to 10,000+ 1 (baseline)
2 200 to 10,000+ 1.5
3 75 to 500 4
5 Sensor arrays 2
6 200 to 10,000+ 1.5
7 75 to 10,000 Flexible
Technology: ConsiderationsTechnology: Considerations
Contact Lifetime
Use contact materials that have demonstrated up to 300M hot-switch cycles
Stiction (cells stick in ON position)
Materials selection and design
Other Considerations
q Full-motion, full-color video is possible
q Long lifetime for static displays
Technology: FunctionalityTechnology: Functionality
q Latching cells enable partial refresh of displayreduces amount of display data needed
q Backplane can be B&W, grayscale, or full color
q Works with virtually all FPD technologies
q Change mask to produce different backplanes
q Latch drive circuitry is easy to add
Technology: Development StatusTechnology: Development Status
Prototype 1 (Mockup)
q Built by Kazuo Senda in Dr. Esashi’s lab at Tohoku University in Sendai, Japan
q 9 by 9 array of 7mm pixels
q Tested several device designs, materials, and processes
q We planned a non-working mockup, but many of the switches actually worked!
q Chose the best switch design.
Technology: Development StatusTechnology: Development Status
Prototype 2 (working backplane)
q New mask based on the best Mockup design
q 9 by 9 array of 6 mm pixels
q Majority of pixels worked
q Tested at 10Hz
q See the video on our website:http://www.rolltronics.com/tech/prototype01.html
Technology: Development StatusTechnology: Development Status
Prototype 3 (working display)
q FASwitch backplane + E Ink display layer
q Response speed is fast
q Backplane uses a glass substrate
q Future versions will use plastic substrate
Kazuo Senda
63mm wide
Pixels are 7mm
Product ApplicationsProduct Applications
First application:
Future applications:
q Flexible signs and displays
q Outdoor signs, and other displays
q Gray-scale and full-color displays
q Higher resolution displays & TVs
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