Electronic part with a comb electrode and protective film and electronic equipment including same
View Patent ↗An electronic part, object of which is to improve temperature characteristics and electrical properties, includes a substrate ( 1 ), a comb-type electrode ( 2 ) that is disposed on the upper surface of the substrate ( 1 ), and a protective film ( 4 ) that covers the comb-type electrode ( 2 ) and has an uneven shape at its top surface. If the pitch width of one pitch in the uneven shape of the protective film ( 4 ) is L, the width of one pitch of a convex portion ( 4 a ) of the unevenness in the uneven shape of the protective film ( 4 ) is L 1 , the width of one pitch of a concave portion ( 4 b ) thereof is L 2, the pitch width of one pitch of the comb-type electrode ( 2 ) is p, the width of one of electrode fingers which form the comb-type electrode ( 2 ) is p 1 and the width between the electrode fingers is p 2, then each parameter is set so that the following expressions are satisfied, L 1 ≦p 1 and L 2 ≧p 2 (herein, the correlations of L≈p, p 1+ p 2= p and L 1+ L 2= L are satisfied).
1. An electronic part which includes a substrate, a comb-type electrode that is disposed on an upper surface of the substrate, and a protective film that covers the comb-type electrode and has an uneven shape at a top surface thereof,
wherein a height from the surface of the substrate which is in contact with the protective film to a top part of a convex portion of the protective film is t, a height from the surface of the substrate which is in contact with the protective film to a bottom part of a concave portion of the protective film is t 1 , a height (t-t 1 ) from the top part of the convex portion of the protective film to the bottom part of the concave portion of the protective film is t 2 , a pitch width of one pitch in the uneven shape of the protective film is L, a width of one pitch of the convex portion of an unevenness in the uneven shape of the protective film is L 1 , a width of one pitch of the concave portion is L 2 , a pitch width of one pitch of the comb-type electrode is p, a width of one of electrode fingers which form the comb-type electrode is p 1 , a width between the electrode fingers is p 2 , and a film thickness of the comb-type electrode is h so as to satisfy t 2 ≦h,
and wherein correlations of L≈p, p 1 +p 2 =p, L 1 +L 2 =L, L 1 <p 1 and L 2 >p 2 are satisfied).
2. The electronic part according to claim 1 , wherein a correlation between the film thickness h of the comb-type electrode and the pitch width p of one pitch of the comb-type electrode is,
0.05≦ h /(2× p ).
3. The electronic part according to claim 1 , wherein a ratio L 1 /L of the width L 1 of one pitch of the convex portion of the unevenness in the uneven shape of the protective film to the pitch width L of one pitch of the protective film is η′ and a ratio p 1 /p of the width p 1 of one of the electrode fingers which form the comb-type electrode to the pitch width p of one pitch of the comb-type electrode isη, and a correlation betweemηandη′ is,
η′/η≦0.86
wherein correlations of L≈p, p 1 +p 2 =p and L 1 +L 2 =L are satisfied.
4. The electronic part according to claim 1 , wherein a center of the width L 1 of one pitch of the convex portion of the unevenness of the protective film is Lc and a center of the width p 1 of the electrode finger of the comb-type electrode which is located under the pitch of the convex portion of the protective film is pc, and Lc and pc are, in plan view, substantially on a same straight line.
5. The electronic part according to claim 1 , wherein the substrate is a lithium-tantalate substrate and a cutout angle of the lithium-tantalate substrate is D° as a rotational angle thereof around an X-axis against a Z-axis direction and the substrate is cut out of a Y-sheet at an angle which satisfies,
38°≦D°.
6. The electronic part according to claim 1 , wherein with respect to the comb-type electrode which is disposed on the upper surface of the substrate and the protective film which covers the comb-type electrode and has the uneven shape at the top surface thereof, a correlation between the height t 1 from the surface of a substrate which is in contact with the protective film to the bottom part of the concave portion of the protective film and the pitch width p of one pitch of the comb-type electrode is,
13%≦ t 1/(2× p )≦35%.
7. The electronic part according to claim 1 , wherein the protective film is silicon dioxide.
8. Electronic equipment which includes at least one antenna and an electric circuit that is electrically connected to the antenna,
wherein the electric circuit is provided with a plurality of electronic parts, and at least one of the electronic parts is the electronic part according to claim 1 .