Surface acoustic wave device and method of fabricating the same

1. A surface acoustic wave device comprising:

a surface acoustic wave filter element having a piezoelectric substrate on which comb-like electrodes are formed; and

a package having a first cavity in which the surface acoustic wave filter is housed,

the package including a flexible chip mounting base that has a first surface on which the surface acoustic wave filter is mounted and has a thickness equal to or less than 100 μm.

2. The surface acoustic wave device as claimed in claim 1 , wherein the package has a second cavity via which a second surface of the flexible chip mounting base opposite to the first surface is exposed.

3. The surface acoustic wave device as claimed in claim 1 , wherein the package includes a lower frame member that is attached to the flexible chip mounting base and defines a second cavity having a size larger than that of the surface acoustic wave filter chip.

4. The surface acoustic wave device as claimed in claim 1 , wherein the package includes:

a second cavity to which a second surface of the flexible chip mounting base opposite to the first surface is exposed; and

a lid board that seals the second cavity.

5. The surface acoustic wave device as claimed in claim 1 , wherein the package includes a lower board having a plate shape, the lower board being attached to the flexible chip mounting base at positions that are further out than the surface acoustic wave filter chip.

6. The surface acoustic wave device as claimed in claim 5 , further comprising an adhesive layer that joins the flexible chip mounting base and the lower board and are provided at the positions that are further out than the surface acoustic wave filter chip.

7. The surface acoustic wave device as claimed in claim 1 , wherein the package includes a lid that hermetically seals the first cavity and is attached to a backside of the surface acoustic wave filter chip.

8. The surface acoustic wave device as claimed in claim 1 , wherein the package includes a lid that hermetically seals the first cavity, and an electrical shield member that is attached to the lid and faces the surface acoustic wave filter chip.

9. The surface acoustic wave device as claimed in claim 8 , wherein the electrical shield member is a planar pattern.

10. The surface acoustic wave device as claimed in claim 1 , the package includes an electrical shield member attached to the flexible chip mountingbase.

11. The surface acoustic wave device as claimed in claim 10 , wherein the electrical shield member is a planar pattern.

12. The surface acoustic wave device as claimed in claim 1 , wherein the surface acoustic wave filter chip has metal bumps, which are electrically and mechanically connected to on-base interconnection lines on the flexible chip mounting base via an electrically conductive resin.

13. The surface acoustic wave device as claimed in claim 1 , wherein the surface acoustic wave filter chip has metal bumps, which are electrically and mechanically connected to on-base interconnection lines on the flexible chip mounting base via an electrically anisotropic conductive sheet.

14. The surface acoustic wave device as claimed in claim 1 , wherein the surface acoustic wave filter chip is flip-chip bonded to the flexible chip mounting base in the first cavity.

15. The surface acoustic wave device as claimed in claim 1 , wherein the flexible chip mounting base has a bending elastic stiffness of 2~8 GPa.

16. The surface acoustic wave device as claimed in claim 1 , wherein the flexible chip mounting base includes at least one of bismaleimide-triazine resin, polyphenylether and polyimide resin.

17. The surface acoustic wave device as claimed in claim 1 , wherein the package comprises a lower board provided so that another cavity is defined between the flexible chip mounting base and the lower board.

18. The surface acoustic wave device as claimed in claim 1 , wherein terminals for making external connections are provided on a backside of the flexible chip mountingbase.