1. UV-LIGA Microfabrication of a Power Relay Based on Electrostatic Actuation
Ren Yang, Seok Jae Jeong, and Wanjun Wang
Department of Mechanical Engineering
Louisiana State University
Baton Rouge, LA 70810
USA
Louisiana State University

2. Introduction.
Design
Fabrication
Summary & Future work

3. 1. Introduction Different Types of Power Relays Traditional Relay
- Advantage: low on resistance, off-leakage, and big output capacitance
- Disadvantage: large, noisy, slow, and difficult to integrate
Solid-state Relay
- Advantage: much longer life time, fast response, low noisy, smaller size
- Disadvantage: high on-resistance, low off-resistance, high power consumption, and poor electrical isolation
MEMS (Micro Electro Mechanical System) Relay
- Takes advantages from traditional and solid-state relay

4. General Principle Commonly Used MEMS Design
Electrostatic force
Magnetomotive force
Piezoelectrical force

5. 2. Design
Schematic diagram of the micro power relay

6. Differences Compared to Other MEMS Relays
Not silicon based
Metal/Alloy as basic materials such as Ni or Cu for conductivity
Thick metal/Alloy pads can be used instead of thin metal films as silicon based relay

7. Fundamental calculation for electrostatic force
E:electrical energy stored by the capacitor
C: capacitance P:power
q:current x:gap
ε:electric permittivity of free space
E:voltage A:surface area

8. 3. Fabrication of micro-relay by UV-LIGA
What is UV-LIGA?
; Approach where a UV aligner is used with a thick resist in place of the synchrotron x-ray exposure step. After the lithography, electrodeposition and planarization are used to produce metal micropart.
Advantages
- High aspect-ratio microfabrication
- Broad selection of materials
- Slightly lower quality and much lower fabrication cost compared to X-ray LIGA

9. Fabrication Method
Bottom part
Top part
Assemble

10. Bottom part substrate photo resist(SU 8) Au/Cr seed layer UV light
mask
developing
electroplating
metal structure

11. Top part Insulation layer substrate photo resist Au/Cr seed layer
UV light
mask
developing
Insulation layer
electroplating
metal structure
Separated structure

12. Top view picture of Bottom and top part
Side view schematic diagram of relay
Bottom part
Top part
Initial open position
Closing operation
Assembled top and bottom part

13. Adding an insulation layer on the bottom part
Top part
Bottom part
Insulation layer

14. Top view picture of Bottom and top part
Side view schematic diagram of relay
Initial open position
Bottom part
Top part
Closing operation
Assembled top and bottom part

15. 4. Preliminary test of assembled relay
Mechanical properties
Measurement of deflection by applied weight

16. Electrical properties
R=872kΩ
Experiment
Calculation
Working voltage
~10V
8.5V
Spring constant
1.7510-3N/
2.1310-3N/m
R=Infinite

17. I
4. Summary
Design of a novel micro-relay for power applications based on electrostatic actuation
Fabrication by UV-LIGA
Preliminary test
Control voltage: 10V
Spring constant: 1.7510-3N/m

18. 5. Future Work Improve fabrication process Measure physical properties
Low stress plating condition
Easy way separate top structure from the substrate.
Measure physical properties
Spring constant
Strength of polymer connector
Test working properties of the assembled power relay
On/off resistance
Life time
reliability