Design of MEMS Packaging
A micro-electromechanical device comprises a micro-electromechanical die, a package, and three pillars attaching the micro-electromechanical die to the package, at least one of the shape, position and orientation of the pillars is configured such that any strain transferred from the package to the die by deformation of the package is minimized.
1 . A micro-electromechanical device comprising:
a micro-electromechanical die;
a package; and
three pillars attaching the micro-electromechanical die to the package;
wherein at least one of the shape, position and orientation of the pillars is configured such that any strain transferred from the package to the die by deformation of the package is minimized.
2 . The micro-electromechanical device of claim 1 , wherein the pillars are bonded to the package and the shape of the pillars is determined based on the minimum contact area needed, given the package, the micro-electromechanical die and bond materials and the bonding process in accordance with die shear test criteria, as given in a predetermined standard.
3 . The micro-electromechanical device of claim 2 , wherein the shape of the pillars is further determined based on the minimum applicable feature size, given the bonding process, the bond material and the bondline thickness.
4 . The micro-electromechanical device of claim 1 , wherein the pillars are formed on the die via chemical etching or mechanical abrasion.
5 . The micro-electromechanical device of claim 1 , wherein the pillars are formed on the substrate via patterned electroplating, molded pillars or mechanical stamping.
6 . The micro-electromechanical device of claim 1 , wherein the pillars are prefabricated and bonded onto the die.
7 . The micro-electromechanical device according to claim 1 , wherein:
the three pillars are arranged around a point on a surface of the micro-electromechanical die; and
the positions of the three pillars satisfy the following equations:
k
x
1
r
x
1
=
-
k
x
2
r
x
2
sin
(
φ
2
)
sin
(
φ
1
)
;
k
x
3
r
x
3
=
k
x
2
r
x
2
(
sin
(
φ
2
)
cos
(
φ
1
)
sin
(
φ
1
)
-
cos
(
φ
2
)
)
;
and
0
=
∑
i
=
1
3
k
yx
1
(
r
x
1
)
2
,
where
:
r x1 , r x2 and r x3 are the lengths of first, second and third axes extending from the first, second and third pillars respectively to the point;
k x1 , k x2 and k x3 are the spring constants in the radial direction of the point of the first, second and third pillars respectively;
k yx1 , k yx2 and k yx3 are the relationships between a deformation of the first, second and third pillars respectively in a direction which is both normal to the radial direction of the central point and parallel to a plane formed by the surface of the micro-electromechanical die and a force applied to the first, second and third pillars respectively in radial direction of the point; and
φ 1 and φ 2 are the angles separating the first and second axes respectively from the third axis.