Piezoelectric vibrator with hermetically closed casing and filler comprising non-spherical conductive particles
There is provided a piezoelectric vibrator 1 that includes a base substrate 2 , a lid substrate 3 , a piezoelectric vibrating reed 4 , a pair of external electrodes 38 and 39 , a pair of through electrodes 32 and 33 , and routing electrodes 36 and 37 . Both surfaces of the base substrate 2 are polished. The lid substrate 3 includes a recess 3 a for a cavity C and is bonded to the base substrate. The piezoelectric vibrating reed 4 is bonded to the upper surface of the base substrate so as to be received in a cavity that is formed between the base substrate and the lid substrate. The pair of external electrodes 38 and 39 is formed on the lower surface of the base substrate. The pair of through electrodes 32 and 33 is formed so as to pass through the base substrate, maintains airtightness in the cavity, and is electrically connected to the pair of external electrodes, respectively. The routing electrodes 36 and 37 are formed on the upper surface of the base substrate and electrically connect the pair of through electrodes to the bonded piezoelectric vibrating reed. The through electrodes are formed by the hardening of paste that contains a plurality of nonspherical metal fine particles.
1. A piezoelectric vibrator comprising:
a hermetically closed casing comprising first and second substrates with a cavity inside, the first substrate being formed with at least one through-hole which is hermetically closed with a filler hardened by firing, wherein the fillers comprise non-spherical conductive particles; and
a piezoelectric vibrating strip secured inside the cavity and electrically connected via a conductive pattern to the fillers in the through-holes.
2. The piezoelectric vibrator according to claim 1 , wherein the piezoelectric vibrating strip is secured, using conducting bumps.
3. The piezoelectric vibrator according to claim 1 , further comprising external electrodes electrically connected to the fillers hardened in the through-holes.
4. An oscillator comprising the piezoelectric vibrator defined in claim 1 .
5. An electronic device comprising the piezoelectric vibrator defined in claim 1 .
6. The electronic device according to claim 5 , wherein the electronic device is an atomic clock.
7. A method for producing piezoelectric vibrators, comprising:
(a) defining a plurality of first substrates on a first wafer and a plurality of second substrates on a second wafer;
(b) forming at least one through-hole in respective at least some of the first substrates on the first wafer;
(c) filling at least some of the through-holes with a paste filler containing non-spherical conductive particles;
(d) firing the first wafer to harden the paste fillers in the at least some of the through-holes to hermetically close the through-holes;
(e) grinding at least one surface of the first wafer to level off any recesses formed by the hardened paste fillers in the through-holes;
(f) layering the first and second wafers such that at least some of the first substrates substantially coincide respectively with at least some of the corresponding second substrates, wherein a piezoelectric vibrating strip is secured in respective pairs of at least some of coinciding first and second substrates;
(g) hermetically bonding the first and second substrates of at least some of the respective pairs recited in step (f);
(h) cutting off respective at least some of the hermetically bonded pairs from the first and second wafers.
8. The method according to claim 7 , further comprising before step (f) forming a recess in at least one of the first substrates and the second substrates to create a cavity between the bonded first and second substrates for storage of the piezoelectric vibrating strip therein.
9. The method according to claim 7 , wherein hermetically bonding the first and second substrates comprises anodically bonding the first and second substrates.
10. The method according to claim 7 , further comprising before step (f) securing the piezoelectric vibrating strip, using conductive bumps.
11. The method according to claim 7 , further comprising before step (c) defoaming the paste filler.