JP2002198740A - Crystal oscillator for surface mounting - Google Patents

Abstract

(57) [Summary] [Object] To provide a high-precision and high-reliability surface mount oscillator which maintains the connection strength of a capacitor, improves the frequency change and aging characteristics, and provides a high precision and high reliability. The present invention relates to a crystal oscillator for surface mounting in which a crystal chip, an IC chip, and a chip capacitor are housed in a concave container.
Both the crystal blank and the chip capacitor are fixed with a silicone-based conductive adhesive. The IC chip and the capacitor are fixed to the bottom surface of the concave container, and the quartz piece is fixed to at least one end of the concave container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator for surface mounting (referred to as a surface mounting oscillator) as an industrial technical field, and particularly to a surface mounting oscillator which promotes miniaturization.

[0002]

2. Description of the Related Art Surface mount oscillators are widely used as various frequency and time reference sources in various electronic devices including communication devices, particularly in portable devices. In recent years, with the further miniaturization of portable devices, surface mount oscillators are increasingly required to be smaller and lighter.

(Example of Prior Art) FIG. 2 is a cross-sectional view of a surface mount oscillator for explaining a conventional example. The surface mount oscillator is formed by fixing a main surface of the IC chip 2 and the capacitor 3 to the bottom surface of a surface mount container made of a laminated ceramic, for example, a concave container 1, and fixing one end of a crystal blank 4 to a step portion, and covering the cover 5. Become. The IC chip 2 integrates each element such as an amplifier constituting an oscillation circuit together with the crystal blank 4 and is fixed by so-called face-down bonding by ultrasonic thermocompression bonding using bumps 6 or the like. The crystal blank 4 has excitation electrodes 7 on both main surfaces.
(Ab), and the extraction electrodes 8 (ab) extend on both sides of one end. The capacitor 3 is formed of a chip element and has a large capacitance value for, for example, bypass and high-frequency coupling, which is difficult to integrate.

The crystal piece 4 is fixed by a silicone-based material, and the capacitor 3 is fixed by, for example, an epoxy-based conductive adhesive. That is, a flexible silicone material is selected for the crystal blank 4 in order to prevent distortion due to curing shrinkage of the conductive adhesive at the time of fixing, and to prevent a decrease in vibration characteristics such as temperature characteristics due to this. In addition, since the capacitor is not affected by curing shrinkage, an epoxy resin is selected because it has high adhesive strength and is easy to handle. Reference numeral 10 in the figure denotes a metal ring for seam welding.

[0005]

[Problems to be Solved by the Invention]
However, in the surface mount oscillator having the above configuration, the conductive adhesive for fixing the crystal blank 4 and the capacitor 3 is different as described above. After fixing the capacitor 3 and the IC chip 2 to the bottom surface, the crystal blank 4 is fixed to the step.

Usually, the curing temperature of a silicone-based adhesive is about 160 ° C., the heat-resistant temperature is about 300 ° C., and the heat-resistant temperature of an epoxy-based adhesive is lower than that of a silicon-based adhesive. For this reason, when the crystal blank 4 is fixed or during annealing (heat treatment) for the purpose of degassing after the fixing, the epoxy conductive adhesive for fixing the capacitor is thermally decomposed, and the bonding function is reduced.

Further, when the cover 5 is sealed and mounted on a circuit board after shipment, that is, when it is transported in a high-temperature furnace and fixed with cream solder, the organic gas from the epoxy-based conductive adhesive is used to remove the crystal blank. To change the oscillation frequency or deteriorate the aging characteristics. For these reasons, there is a problem that it is not suitable for, for example, a temperature-compensated oscillator that requires particularly high precision and high reliability.

(Object of the Invention) It is an object of the present invention to provide a surface mount oscillator having high accuracy and high reliability by maintaining the connection strength of a capacitor and improving the frequency change and aging characteristics.

[0009]

The basic solution of the present invention is to fix both a crystal piece and a capacitor housed in a concave container with a silicone-based conductive adhesive.

[0010]

According to the present invention, since both the crystal blank and the capacitor are fixed by a silicone-based conductive adhesive, the influence of heat is prevented. Hereinafter, an embodiment of the present invention will be described.

[0011]

FIG. 1 is a sectional view of a surface mount oscillator for explaining an embodiment of the present invention. The same parts as those in the prior art are denoted by the same reference numerals, and description thereof will be simplified or omitted. As described above, the surface mount oscillator is provided with the I
One main surface of the C chip 2 and the capacitor 3 is fixed to the stepped portion on both sides of one end of the crystal blank 4 and covered with a cover 5.

In this embodiment, first, the bump 6
The IC chip 2 is fixed to the bottom surface by so-called face-down bonding using ultrasonic thermocompression bonding or the like. Next, a conductive adhesive 9 is applied to the bottom surface and the stepped portion, and the capacitor 3 and the crystal piece 4 are mounted thereon. Each of the conductive adhesives 9 is made of silicone. Then, the capacitor 3 and the crystal piece 4 are fixed by heating and hardening in a high-temperature furnace. Thereafter, degassing is performed by annealing, and the cover 5 is joined and sealed.

With this configuration, since the capacitor 3 and the crystal blank 4 are fixed to each other with the same silicone-based conductive adhesive 9, the conductive adhesive may be thermally decomposed during annealing as described above. And the connection strength of the capacitor 3 is maintained. In addition, the frequency change and aging characteristics are improved without generating organic gas when the solder paste is mounted on the circuit board by cream solder. Therefore, it maintains high accuracy and high quality and is particularly suitable for a temperature compensated oscillator.

Further, since the conductive adhesive is the same and the fixing conditions such as the heating temperature are the same, the capacitor 3 and the crystal blank 4 can be simultaneously fixed as in this embodiment. Therefore, in this case, productivity can be improved.

[0015]

[Others] In the above embodiment, the IC chip 2 and the capacitor 3 are fixed to the bottom of the concave container 1 and the crystal blank 4 is fixed to the step. However, for example, when the step is removed and each element is fixed to the bottom. This may be applied to a case where each element is accommodated in the same space. Although the quartz piece 4 is fixed at one end on both sides, the extraction electrode 8 (ab) may be extended to both ends to fix the both ends. Further, although the cover 5 is seam-welded, it goes without saying that the cover 5 may be beam-welded, resin-sealed, or glass-sealed.

[0016]

According to the present invention, since both the crystal piece and the capacitor housed in the concave container are fixed with a silicone-based conductive adhesive, the connection strength of the capacitor is maintained to change the frequency and the aging. It is possible to provide a surface-mounted oscillator with improved characteristics and high accuracy and high reliability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a surface mount oscillator illustrating one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a surface mount oscillator illustrating a conventional example.

FIG. 3 is a plan view of a crystal blank for explaining a conventional example.

[Explanation of symbols]

1 concave container, 2 IC chip, 3 capacitor, 4
Crystal blank, 5 cover, 6 bump, 7 excitation electrode, 8
Lead electrode, 9 conductive adhesive, 10 metal ring.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J079 AA04 BA43 HA03 HA07 HA11 HA25 HA28 HA29 KA05 5J108 BB02 CC04 EE03 EE07 EE18 FF07 GG03 KK04

Claims (3)

[Claims] 1. A surface mounting crystal oscillator comprising a crystal container, an IC chip, and a chip capacitor housed in a concave container, wherein both the crystal chip and the chip capacitor are fixed with the same resin-based conductive adhesive. A crystal oscillator characterized by the following. 2. The crystal oscillator according to claim 1, wherein said conductive resin-based adhesive is a silicone-based conductive adhesive. 3. The crystal oscillator according to claim 1, wherein the IC chip and the capacitor are fixed to a bottom surface of the concave container, and the crystal piece is fixed to at least one end of the concave container.