Abstract
An external electromagnet plus moving PM (permanent magnet) FPCB (flexible printed circuit board) micromirror is proposed in this paper that can overcome two limitations associated with the previous FPCB micromirror with a configuration of an external PM plus moving coil, i.e., (1) it reduces the overall width beyond the mirror plate, and (2) increases the maximum rotation angle. The micromirror has two external electromagnets underneath an FPCB structure (two torsion beams and a middle seat) with two moving PM discs attached to the back and a metal-coated mirror plate bonded to the front of the FPCB middle seat. Modeling and simulation were introduced, and the prototype was fabricated and tested to verify the design. The achieved performance was better than that of the previous design: a maximum resonant rotation angle of 62° (optical) at a driving voltage of ±3 V with a frequency of 191 Hz, the required extra width beyond the mirror plate was 6 mm, and an aperture of 8 mm × 5.5 mm with a roughness of <10 nm and a flatness of >10 m (ROC, radius of curvature). The previous FPCB micromirror’s performance was: strain limited maximum rotation angle was 40° (optical), the extra width beyond the mirror plate was 14.7 mm, and had an aperture of 4 mm × 4 mm with a similar roughness and flatness.
Highlights
MEMS micromirrors have been widely and successfully used in displays [1,2,3,4,5,6,7], optical switches [8], and medical devices [9] because of their small size, high integration, high reliability, and low cost
A larger rotation can be achieved due to the higher strain limit. Those flexible printed circuit board (FPCB) micromirrors share the same advantages as the second type of MEMS micromirrors, i.e., a large aperture and high flatness
This paper proposes an FPCB micromirror to overcome these two limitations in the following two ways: (1) It utilizes the configuration of two moving permanent magnet (PM) discs plus two external electromagnets, which are underneath the FPCB structure
Summary
MEMS (microelectromechanical systems) micromirrors have been widely and successfully used in displays [1,2,3,4,5,6,7], optical switches [8], and medical devices [9] because of their small size, high integration, high reliability, and low cost. The second type can achieve a large aperture (several millimeters) with a high flatness (ROC >10 m), in which the mirror plate and actuator are fabricated separately and bonded together afterwards [21,22]. The second type needs to bond the mirror plate onto a released and fragile micro actuator, which is very difficult and leads to a low bonding yield due to the low strain limit of the silicon flexible structure. The flexible parts of FPCB structure are the polyimide layer or polyimide plus copper film laminate layer, which has a higher strain limit than silicon. A larger rotation can be achieved due to the higher strain limit Those FPCB micromirrors share the same advantages as the second type of MEMS micromirrors, i.e., a large aperture and high flatness. Two driving methods are used for those FPCB micromirrors, i.e., electrostatic [23,24,25] and magnetic with the configuration of “moving coil plus external permanent magnet (PM)” [26]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
