JP2007158419A - Crystal oscillator for surface mount - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive surface mount crystal oscillator for expediting miniaturization. <P>SOLUTION: The crystal oscillator for surface mount has a closed container 1 comprising a rectangular ceramic substrate 4 that has a metal film 9 on the outer periphery circulating around one main surface, and a packaged electrode 7 on the other surface; and a recessed metal cover 5, where an opening end face is brazed to the metal film 9. The closed container 1 stores an IC chip 2 and a crystal piece 3 in the closed container 1. The ceramic substrate 4 is formed in a plate shape where both the main surfaces are horizontal. In the IC chip 2, a circuit functional surface is fixed onto one main surface of the ceramic substrate 4 by using a bump 12. One extended longitudinal edge of an extraction electrode 14 in the crystal piece 3 is stuck onto one edge of a surface opposite to the circuit functional surface of the IC chip 2 directly, or by interposing an auxiliary substrate 21. The extraction electrode 14 extended to both the sides of one edge in the crystal piece 3 is electrically connected to a relay terminal 16 provided on the ceramic substrate 4 via a conductor 20 at least by wire bonding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface mount crystal oscillator (hereinafter referred to as a surface mount oscillator), and more particularly to a small and inexpensive surface mount oscillator.

(Background of the Invention)
Since surface-mounted oscillators are small and lightweight, they are built in as a reference source for frequency and time in compact mobile electronic devices such as mobile phones. One of such devices is a surface mount oscillator by the present applicant (see Patent Document 1).

(Example of conventional technology)
FIG. 3 is a diagram of a surface-mount oscillator for explaining a conventional example. FIG. 3 (a) is a sectional view, FIG. 3 (b) is a diagram of a circuit function surface (one main surface) of the IC chip, and FIG. ) Is a plan view of the crystal piece.

  The surface mount oscillator includes an IC chip 2 and a crystal piece 3 housed in a sealed container 1. The sealed container 1 includes a ceramic substrate (mounting substrate) 4 and a metal cover 5. The ceramic substrate 4 is formed by laminating a flat plate-like first ceramic 4a having a rectangular shape and a second ceramic 4b having an opening and forming a recess. The first ceramic 4a has circuit terminals 6 that are electrically connected to the IC chip 2 on the surface on the laminated surface side (the bottom surface of the recess), and has mounting electrodes 7 on the four corners of the back surface.

  The mounting electrode 7 is electrically connected to the circuit terminal 6 to which the IC terminal 8 of the IC chip 2 is fixed via the side surface electrode by the through hole and the laminated surface of the first and second ceramics 4 (ab). The side electrodes form solder fillets when mounted on a set substrate (not shown). The second ceramic 4b has a metal film 9 for sealing on the outer periphery, and has crystal holding terminals 10 on both sides of one end. The metal cover 5 has a concave shape, and the opening end face is bonded onto the metal film 9 of the second ceramic 4b. For example, bonding is performed by thermocompression bonding using a metal braze 11 such as a eutectic alloy AuSn.

  The IC chip 2 has at least an oscillation circuit, and has an IC terminal 8 on one main surface which is a circuit function surface. And it adheres to the circuit terminal 6 on the 1st ceramic 4a by ultrasonic thermocompression using the bump 12. FIG. Thereby, each IC terminal 8 of the IC chip 2 is electrically connected to the mounting electrode 7 and the crystal holding terminal 10.

  The IC terminal 8 has at least a pair of crystal terminals and a power source, an output, a ground, and an automatic control (AFC) terminal that are electrically connected to the mounting electrode 7. The crystal piece 3 has excitation electrodes 13 on both main surfaces, and extends extraction electrodes 14 on both sides of one end in the length direction. Then, both ends of the extended end portion of the extraction electrode 14 are fixed to the crystal holding terminal 10 by the conductive adhesive 15 or the like. The crystal holding terminal 10 is electrically connected to the crystal terminal of the IC chip 2.

In such a case, compared to a case where a flat metal cover 5 is joined to a container body made of a laminated ceramic (not shown), the metal cover 5 is particularly concave and joined to the outer periphery of the ceramic substrate 4. Therefore, the inner product can be increased because the thickness of the metal cover 5 is, for example, 0.08 mm, which is smaller than the frame width of the container body, for example, 0.35 mm. In other words, downsizing can be promoted.
JP 2003-318690 A Japanese Utility Model Publication No. 6-48215

(Problems of conventional technology)
However, in the surface mount oscillator having the above-described configuration, the ceramic substrate 4 has the first and second ceramics 4 (ab) laminated, so that there is a problem that the unit price does not decrease. In particular, since the second ceramic 4b has an opening and has a punching process, there is a problem that it is expensive.

  Further, since the ceramic substrate 4 requires stepped portions that hold both sides of one end of the crystal piece 3, the area for accommodating the IC chip 2 is limited. In particular, when a temperature compensation mechanism or the like that increases the added value is integrated, the IC chip 2 is increased in size, so that there is a problem that the step portion prevents the ceramic substrate 4 from being reduced in size (smaller in area).

(Object of invention)
It is an object of the present invention to provide a surface mount oscillator that is inexpensive and promotes miniaturization.

  According to the present invention, as shown in the claims (Claim 1), a rectangular ceramic substrate having a metal film on the outer periphery of one main surface and mounting electrodes on the other main surface, and the metal A crystal oscillator for surface mounting, comprising: a sealed container comprising a concave metal cover whose opening end face is brazed to a film, wherein an IC chip and a crystal piece are housed in the sealed container; The substrate is a flat plate with both main surfaces being horizontal surfaces, and the IC chip is fixed to one main surface of the ceramic substrate with a circuit function surface using bumps, and the length direction in which the lead electrode of the crystal piece extends is extended. One end is fixed directly on one end opposite to the circuit function surface of the IC chip or via an auxiliary substrate, and lead electrodes extending on both sides of the one end of the crystal piece are provided on the ceramic substrate. Relay terminal and at least A structure that is electrically connected through a conductive wire by Ya bonding.

  With such a configuration, since the ceramic substrate is not provided with a frame portion having an opening as both horizontal surfaces, the unit price of the ceramic substrate can be reduced. Further, since the crystal piece is provided on the IC chip, the ceramic substrate does not require a step portion for fixing both ends of the crystal piece. Since the lead electrodes on both sides of one end of the crystal piece are connected to the relay terminal by wire bonding, the distance between the one end of the crystal piece and the relay terminal can be shortened. Therefore, the inner product of the ceramic substrate can be increased to reduce the size.

(Embodiment section)
According to a second aspect of the present invention, the ceramic substrate and the crystal piece have the same length direction, and the relay terminal is on both sides of one end portion of the ceramic substrate in the length direction. Thereby, the length of the ceramic substrate can be shortened and miniaturized.

  In the third aspect, one end of the crystal piece of the first aspect is fixed to the surface opposite to the circuit function surface of the IC chip by an insulating adhesive, and the lead electrode and the relay terminal are directly connected by wire bonding. Connect to. According to this, since the opposing surface of the crystal piece is directly fixed to the IC chip, the number of parts can be reduced.

  According to the fourth aspect of the present invention, the crystal piece of the first aspect is fixed to the crystal holding terminal of the auxiliary substrate by a conductive adhesive on both sides of the extended end portion of the extraction electrode, and the auxiliary substrate is a circuit functional surface of the IC chip. The crystal holding terminal is electrically connected to the relay terminal by wire bonding. According to this, since the auxiliary substrate is used, workability is facilitated.

  In claim 5, the ceramic substrate according to claim 1 is a single layer, and the mounting electrode is electrically connected to the IC chip through a via hole provided in the ceramic substrate. According to this, since the ceramic substrate is a single layer, the unit price is further reduced.

  According to the sixth aspect of the present invention, the ceramic substrate according to the first aspect is a multilayer, and the mounting electrode is electrically connected to the IC chip through a multilayer surface of the ceramic substrate. According to this, since the IC chip is electrically connected to the mounting electrode through the laminated surface, airtightness is ensured.

  In claim 7, the ceramic substrate of claim 1 is a laminate, and a temperature compensation data write terminal is provided on a side surface of the ceramic substrate. Thereby, an inexpensive and small temperature compensated oscillator can be configured.

(First embodiment)
FIG. 1 is a diagram for explaining a first embodiment of the present invention. FIG. 1 (a) is a cross-sectional view of a surface mount oscillator, and FIG. 1 (b) is a plan view of a ceramic substrate. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.

  As described above, the surface-mount oscillator includes the sealed container 1 in which the opening end surface of the concave metal cover 5 is bonded to the rectangular ceramic substrate 4 having the metal film 9 on the outer periphery of one main surface by the metal brazing 11. Prepare. The IC chip 2 and the crystal piece 3 are accommodated in the sealed container 1.

  In the first embodiment, the ceramic substrate 4 is a minimum of one layer, and has a flat plate shape in which both main surfaces are horizontal surfaces. The circulating metal film 9 is separated from, for example, the outer peripheral ends of the four corners, and side electrodes 7b are formed by through holes on the end surfaces (side surfaces) of the four corners. Circuit terminals 6 and relay terminals 16 are formed on one main surface of the ceramic substrate 4. Further, the crystal piece 3 is made shorter than the length of the IC chip 2.

  A total of eight circuit terminals 6 corresponding to the IC terminals 8 of the IC chip 2 are formed, four on each side in the length direction. As described above, at least a pair of crystal terminals 6 (X1, X2), a power source 6 (Vcc), an output 6 (Vout), a ground 6 (E), and an automatic frequency control 6 (AFC) terminal are provided. The IC chip 2 here includes a temperature compensation mechanism together with an oscillation circuit, and has two write terminals for writing temperature compensation data. Correspondingly, the circuit terminal 6 has two write terminals 6 (W1, W2).

  The relay terminals 16 are provided on both sides of one end of the ceramic substrate 4 in the length direction, and are electrically connected to the crystal terminals 6 (X1, X2) in the circuit terminals 6 by conductive paths 17. The other main surface (outer surface, bottom surface) of the ceramic substrate 4 has mounting electrodes 7 connected to the side electrodes 7b. The power supply 6 (Vcc), output 6 (Vout), ground 6 (E), and automatic frequency control terminal 6 (AFC) in the IC terminal 8 (circuit terminal 6) are electrically connected.

  The other main surface is provided with writing surface terminals 7 (W1, W2) which are connected to the writing terminals 6 (W1, W2) and contact the temperature compensation data writing probe. The writing surface terminal 7 (W1, W2) is provided at the center between the mounting electrodes 6 on both long sides. The mounting electrode 7 and the writing surface terminal 7 (ab) are connected to the corresponding circuit terminals 6 by via holes 18 and conductive paths 17 on one main surface. The metal film 9 is electrically connected to the ground terminal 7 (E) in the mounting electrode 7 through a via hole 18 to form a case ground.

  The via hole 18 fills the through hole with a printing material when the circuit base pattern (the circuit terminal 6, the relay terminal 16, the conductive path 17, and the mounting electrode 7) is formed by printing. The printing material is made of molybdenum (Mo) or tungsten (W), for example. Then, after integrally firing together with the ceramic fabric, for example, nickel (Ni) and gold (Au) by plating are laminated on the circuit pattern. Thereby, a through-hole is obstruct | occluded and a sealing is maintained.

  In the IC chip 2, each IC terminal 8 is connected to the circuit terminal 6 by ultrasonic thermocompression using the bumps 12 as in the prior art. The crystal piece 3 is aligned with the ceramic substrate 1 in the length direction, and the opposing surface of one end portion of the lead electrode 14 is extended to one end portion of the surface opposite to the circuit function surface of the IC chip 2 by the insulating adhesive 19. It is fixed. In this case, one end portion of the crystal piece does not protrude from the outer periphery within the surface of the IC chip 2. And it connects with the relay terminal 16 of the ceramic substrate 4 by the wire bonding by the gold wire 20 as a conducting wire.

  With such a configuration, the ceramic substrate 4 is a flat single layer. Therefore, since the ceramic substrate 4 is a flat plate with the minimum number, the cost can be reduced. Since the crystal piece 3 is directly fixed on the IC chip 2, no stepped portion for holding both ends of the one end portion is required. Therefore, if the length of the crystal piece 3 is the same, the length of the ceramic substrate 4 can be shortened. Conversely, if the length of the ceramic substrate 4 is the same, the inner product can be increased.

  Incidentally, the distance from one end of the IC chip 2 to the inner peripheral surface of the metal cover 5 can be about 0.3 mm. On the other hand, the step portion in the conventional example requires about 0.4 mm because it requires a coating area of the adhesive, and further requires a gap of about 0.15 mm for mounting the IC chip 2 in the recess. Therefore, the conventional example requires approximately 0.55 mm, and can be shortened by 0.25 mm. Thereby, in addition to the reduction | decrease by having set it as the metal cover 5, further size reduction or an inner product can be enlarged.

  Further, one end of the crystal piece 3 is directly fixed on the IC chip 2 by an insulating adhesive 19. Therefore, since the IC chip 2 is also used as a holding base for the crystal piece 3, the number of parts can be reduced. Further, since the crystal piece 3 is made shorter than the length of the IC chip 2, the size of the ceramic substrate 4 can be reduced depending on the size of the IC chip 3.

  Although the crystal piece 3 is arranged horizontally, it may be inclined with the other end side facing upward to prevent contact with the IC chip 2. In this case, if the wire bonding (gold wire 20) has a loop height, the height can be kept low. Further, the writing surface terminals 6 (W1, W2) provided on the bottom surface can be applied as mounting electrodes as necessary in order to increase the connection strength to the set substrate.

(Second Embodiment)
2A and 2B are views for explaining a second embodiment of the present invention. FIG. 2A is a cross-sectional view of a surface mount oscillator, and FIG. 2B is a plan view of an auxiliary substrate 21. FIG. In addition, description of the same part as 1st Embodiment is abbreviate | omitted or simplified.

  In the second embodiment, the crystal piece 3 is not directly fixed to the IC chip 2, but the crystal piece 3 is mounted on the IC chip 2 with the auxiliary substrate 21 interposed, and other configurations are the first embodiment. Same as The auxiliary substrate 21 here is made of, for example, a crystal plate having the same cutting angle (AT cut) as the crystal piece 3 and has a pair of crystal holding terminals 10.

  Here, first, the IC chip 2 is fixed onto the ceramic substrate 4 by ultrasonic thermocompression bonding similar to the above. Next, the auxiliary substrate 21 is fixed on the IC chip 2 by the insulating adhesive 19. Next, both ends of one end of the crystal piece 3 from which the extraction electrode 14 extends are fixed to the crystal holding terminal 10 of the auxiliary substrate 21 by the conductive adhesive 15. Finally, the crystal holding terminal 10 and the relay terminal 16 on the ceramic substrate 4 are connected by a gold wire 20 for wire bonding. Then, the opening end face of the metal cover 5 is bonded and sealed to the metal film 9 provided on the outer periphery of the ceramic substrate 4 by thermocompression using the metal solder 11.

  With such a configuration, the crystal piece 3 is mounted on the IC chip 2 with the auxiliary substrate 21 interposed. Therefore, since the auxiliary substrate 21 is fixed on the entire surface of the IC chip 2, it is mechanically stable. This facilitates the wire bonding operation for connecting the crystal holding terminal 10 and the relay terminal 16. Further, since the crystal piece 3 has a gap from the IC chip 2 depending on the thickness of the auxiliary substrate 21, the fixing work or the like is facilitated. Then, the contact with the IC chip 2 is prevented and the vibration characteristics are kept good.

  Here, since the auxiliary substrate 21 has the same cutting angle (AT cut) as that of the crystal piece 3, for example, the expansion coefficient is made the same. Therefore, the occurrence of distortion due to the difference in expansion coefficient is suppressed, and the thermal shock characteristics of the crystal resonator (crystal piece 3) are improved. In the second embodiment, as in the first embodiment, since the ceramic substrate 4 is a flat plate as the minimum number of single layers, the cost can be reduced. And since the step part holding one end part both sides is not required, the length of the ceramic substrate 4 can be shortened and an inner product can be enlarged.

(Other matters)
In the first and second embodiments, since the other end side of the crystal piece 3 is a free end, when there is an impact, it collides with the IC chip 2 and adversely affects the vibration characteristics. Therefore, a flexible adhesive may be applied to, for example, the other end of the crystal chip 3 and / or the other end of the metal cover 5 corresponding to the other end of the crystal piece 3 to reduce the swing width at the time of impact.

  Moreover, although all the ceramic substrates 4 were made into the single layer, if each layer is flat form, a lamination | stacking may be sufficient. Even in this case, since a frame-shaped ceramic is not used, it can be made cheaper than the prior art without requiring punching. The same effects as described in the first embodiment are obtained.

  For example, in the case of lamination, the IC chip 2 and the mounting electrode 7 are electrically connected through the lamination surface to ensure confidentiality. In the case of the temperature compensation type, a temperature compensation data writing terminal, a crystal resonator characteristic inspection terminal, and the like can be formed on the side surface of the ceramic substrate 4. In this case, an electrical short circuit can be prevented by using the uppermost layer and the lowermost layer of the multilayer ceramic as electrodeless electrode layers.

  Further, the mounting electrodes 7 are provided with side electrodes at the four corners. However, in order to increase the inner product, the side electrodes may be removed and only the bottom surfaces of the four corners may be provided. Furthermore, although the metal film 9 is provided up to the peripheral edge, it may be separated from the peripheral edge in order to facilitate the division of the ceramic sheet. The temperature compensation oscillator having the temperature compensation data writing terminal has been described, but it is needless to say that the present invention can be applied even if there is no temperature compensation mechanism.

1A and 1B are views for explaining a first embodiment of the present invention, in which FIG. 1A is a cross-sectional view of a surface mount oscillator, and FIG. 1B is a plan view of a ceramic substrate 4. 4A and 4B are diagrams illustrating a second embodiment of the present invention, in which FIG. 1A is a cross-sectional view of a surface mount oscillator, and FIG. 2B is a plan view of an auxiliary substrate 21. FIG. 2A is a cross-sectional view of a surface-mount oscillator for explaining a conventional example, FIG. 2B is a plan view of a crystal piece 3, and FIG. 1C is a circuit function surface (mainly) of an IC chip 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Airtight container, 2 IC chip, 3 Crystal piece, 4 Mounting board, 5 Metal cover, 6 Circuit terminal, 7 Mounting electrode, 8 IC terminal, 9 Metal film, 10 Crystal holding terminal, 11 Metal solder, 12 Bump, 13 Excitation Electrode, 14 Lead electrode, 15 Conductive adhesive, 16 Relay terminal, 17 Conductive path, 18 Via hole, 19 Insulating adhesive, 20 Gold wire, 21 Auxiliary substrate.

Claims (7)

  A sealed container comprising a rectangular ceramic substrate having a metal film on an outer periphery of one main surface and a mounting electrode on the other main surface; and a concave metal cover having an open end surface brazed to the metal film; A crystal oscillator for surface mounting in which an IC chip and a crystal piece are accommodated in the hermetically sealed container, wherein the ceramic substrate is a flat plate whose both main surfaces are horizontal surfaces, and the IC chip is the ceramic chip A circuit function surface is fixed to one main surface of the substrate using a bump, and one end portion in the length direction in which the lead electrode of the crystal piece extends is on one end portion of the surface opposite to the circuit function surface of the IC chip. The extraction electrode fixed directly or through an auxiliary substrate and extending on both sides of one end of the crystal piece is electrically connected to a relay terminal provided on the ceramic substrate through at least a wire by wire bonding. A surface-mount crystal oscillator according to claim.   2. The surface-mount crystal oscillator according to claim 1, wherein the ceramic substrate and the crystal piece have the same length direction, and the relay terminal is on both sides of one end portion of the ceramic substrate in the length direction.   2. The surface mounting device according to claim 1, wherein one end of the crystal piece is fixed to an opposite surface of the IC chip to the circuit function surface by an insulating adhesive, and the extraction electrode and the relay terminal are directly connected by wire bonding. Crystal oscillator.   The crystal piece is fixed to the crystal holding terminal of the auxiliary substrate by a conductive adhesive on both sides of the extended end portion of the extraction electrode, and the auxiliary substrate is an insulating adhesive on the surface opposite to the circuit function surface of the IC chip. A crystal oscillator for surface mounting, wherein the crystal holding terminal is electrically connected to the relay terminal by wire bonding.   2. The surface-mount crystal oscillator according to claim 1, wherein the ceramic substrate is a single layer, and the mounting electrode is electrically connected to the IC chip through a via hole provided in the ceramic substrate.   2. The surface-mount crystal oscillator according to claim 1, wherein the ceramic substrate is a laminate, and the mounting electrode is electrically connected to the IC chip through a laminate surface of the ceramic substrate.   2. The surface-mount crystal oscillator according to claim 1, wherein the ceramic substrate is laminated, and a temperature compensation data writing terminal is provided on a side surface of the ceramic substrate.

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