Method of packaging electronic parts

1. A method of fabricating electronic parts comprising the steps of:

(a) mounting electronic elements in regular cavities that are two-dimensional array arranged on a baseboard on which dummy cavities are provided so as to be located further out than the array of the regular cavities and surround the array of the regular cavities wherein there are no dummy cavities located between any adjacent pair of regular cavities in the array, and wherein no electronic elements are mounted in the dummy cavities; and

(b) covering a top of the baseboard with a resin sheet.

2. The method as claimed in claim 1 , wherein the step (b) includes a step of supplying resin of the resin sheet to given dummy cavities having bottoms that are not metallized.

3. The method as claimed in claim 1 , wherein the step (b) includes a step of placing the resin sheet on the top of the baseboard so as to cover the regular and dummy cavities and pressurizing the resin sheet while heating, so that the regular and dummy cavities can be hermetically sealed.

4. The method as claimed in claim 1 , further comprising a step (c) of dividing the baseboard into separate electronic parts each of which includes one of the electronic elements in a corresponding one of the regular cavities.

5. The method as claimed in claim 1 , wherein the dummy cavities are at least 150 μm away from regular cavities located at outermost positions.

6. The method as claimed in claim 1 , wherein the dummy cavities are away from regular cavities located at outermost positions at a distance equal to that at which the regular cavities are two-dimensionally arranged.

7. The method as claimed in claim 1 , wherein the dummy cavities are away from regular cavities located at outermost positions at a distance equal to or longer than a gap between sidewalls of the regular cavities and the electronic elements in the regular cavities.

8. The method as claimed in claim 1 , wherein the dummy cavities are arranged in rows and columns of a two-dimensional arrangement of the regular cavities.

9. The method as claimed in claim 1 , wherein each of the dummy cavities, is arranged common to at least two rows and columns of a two-dimensional arrangement of the regular cavities.

10. The method as claimed in claim 1 , wherein the dummy cavities make a single groove that totally surrounds a two-dimensional arrangement of the regular cavities.

11. The method as claimed in claim 1 , wherein the dummy cavities are at least 50 μm deep.

12. The method as claimed in claim 1 , further comprising a step of attaching a wiring board to a backside of the baseboard so that terminals on the wiring boards are electrically connected to terminals in the regular cavities by via interconnections provided in the baseboard.

13. The method as claimed in claim 1 , wherein the electronic elements are surface acoustic wave filter chips, and the electronic parts are surface acoustic wave devices.