JP2000315918A - Crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reflow solder from flowing to a bonding part of other kind. SOLUTION: In the case that an IC chip connection land 11a and a capacitor connection land 11b are placed at both ends of one print pattern among print patterns formed on a bottom face of a ceramic-substrate made package main body 7 (of an oscillation circuit section) being a component of the crystal oscillator, the pattern is broken in the middle and as shown in a cross sectional view (c), the broken ends of the pattern are connected via an inner print pattern 12, and through-holes or a through-wire 12s so that reflow solder is prevented from flowing to the unnecessary land of the other end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator in which a crystal oscillator and its oscillation circuit are integrated, and more particularly, to a crystal oscillator in which the oscillator and the oscillation circuit are housed in a container.

[0002]

2. Description of the Related Art In order to be incorporated in recent electronic devices such as mobile phones, the crystal oscillator has changed from a single crystal oscillator alone to a crystal oscillator including an electric circuit such as an oscillation circuit, and has a very small size. Have been. In such a crystal oscillator, a container in which a crystal oscillator is accommodated and a container in which an oscillation circuit portion is incorporated are combined into a single container, and a single-part crystal oscillator having a flat package type external electrode is provided. Supplied to the market.

FIG. 5 shows an example of such a case, and FIG.
FIG. 5B schematically shows the internal structure of the crystal oscillator, and FIG. 5B schematically shows the shape of external electrodes connected to a pattern on a printed circuit board in which the crystal oscillator is incorporated. As an approximate size of such a crystal oscillator, L = 5 and B = 3.2 m
A rectangle having a size of about 1.5 mm and a thickness D of about 1.5 mm is known. Then, two ceramic substrate bodies 64 and 67 formed in a shallow box shape are joined in two upper and lower stages. A lid 6 made of a thin metal (such as Kovar) is joined to the upper container body 64 (hereinafter, referred to as an upper container 64) by seam welding, brazing, bonding, or the like. By joining to the bottom of the main body 64, the inside can be kept airtight, for example.

A thin rectangular crystal resonator 5 is accommodated in an upper container 64, and electronic components such as an IC chip 8 and a capacitor 9 constituting an oscillation circuit are accommodated in a lower ceramic substrate body 67. Will be accommodated. A portion in which the upper crystal resonator 6 is sealed is referred to as a crystal vibrating portion 62, and a portion in which the lower electronic circuit is sealed is referred to as an oscillation circuit portion 63. A plurality of external electrodes 13 for surface-mounting the completed crystal oscillator 61 on a printed circuit board are provided on the outside of the bottom surface of the lower container body 67, and necessary terminals of an oscillation circuit formed by internal electronic components and ceramics are provided. The connection is made via a pattern on a substrate, through holes or through wires, etc., and a detailed description thereof will be described later. The external electrode 1
In addition to 3, the oscillation frequency adjusting electrode 14 used in manufacturing the crystal oscillator may be formed.

As described above, the circuit components constituting the oscillation circuit section 63 in the crystal oscillator 61 are usually integrated on one IC chip and usually have one to three large capacitors connected to the outside and other components. Is merely connected to the outside of the IC chip 8. Note that the IC chip 8 has a built-in frequency adjustment circuit, temperature compensation circuit, and the like.

The detailed structure of the oscillation circuit section 63 will be described with reference to FIG. FIG. 6A shows a state in which electronic components forming the oscillation circuit 63 are mounted on a printed pattern formed on the container 67 by surface mounting, and FIG. 6B shows a printed pattern before mounting the electronic components. In each case, in order to show the internal configuration of the oscillation circuit section, the crystal oscillation section 62 is removed. FIG. 6C shows a crystal oscillator 61.
2 shows a cross section taken along line AA.

In these figures, reference numeral 8 denotes an IC chip on which bumps (protrusion electrodes) made of, for example, gold are formed as connection terminals, and reference numeral 9 denotes a rectangular capacitor for surface mounting having external electrodes at both ends. These are connected to a predetermined position of the print pattern by a predetermined method. That is,
The print patterns 51, 51a, 51b in FIG.
In the 51X, square lands 51b, 51b, 51
External electrodes formed at both ends of the capacitor 9 are connected to b and 51b. The dashed-dotted rectangle in FIG.
The lands 51a, 51a, and 51a represent the outer shape of the chip 8 and are formed at the ends of the print pattern inside the square.
Are connected to the bumps formed on the lead electrodes of the IC chip to be mounted. Incidentally, the print pattern 51X indicates a connection pattern between the land 51a and the land 51b.

[0008] As shown in FIG.
4 and 67 are printed patterns 51, 51,... For attaching quartz oscillators and other electronic components.
Are formed, and inner layer patterns 52, 52 are also formed inside the substrate. In addition, the conductive pattern 10 is also formed on the convex portion (flange portion) on the outer periphery where the containers 64 and 67 abut. A plurality of external electrodes 13 for surface mounting on a printed circuit board are provided on the outer surface of the bottom surface of the lower container 67, and connection with required terminals of each built-in electronic component is performed by a pattern 51, an inner layer pattern 52, This is performed via a through hole or a through wire 52s.

In order to join the external electrodes of the electronic component for surface mounting to the lands formed on the printed pattern of the printed circuit board, generally, reflow soldering is used. ) And a flip chip method using a conductive adhesive may be used.

However, when any one of the joining methods is employed, the following problems have been confirmed by a vibration test, a temperature test, or various acceleration tests. For example, when all the electronic components are mounted by reflow soldering, the characteristic change due to the aging of the IC chip becomes large. This requires paste application, cream solder supply, heating, etc. to perform the reflow soldering process, but if the subsequent cleaning is incomplete, the remaining impurities will change the oscillation circuit constant. It is thought to be. Therefore, it is conceivable to mount all the electronic components using a conductive adhesive. However, the conductive adhesive increases the electrical resistance at the joint of the components with respect to soldering.

[0011] The resistance value generated at this connection portion hardly causes a problem in an element having a high input impedance such as an IC chip, but a resistor is connected in series to the capacitance of a capacitor. In other words, the dielectric loss tangent (tan δ) increases, and the characteristics of the capacitor deteriorate. Further, when the capacitor is related to the oscillation frequency, it is conceivable that the Q of the crystal resonator is directly reduced and the characteristics are changed.

Therefore, the connection between the IC chip and the land of the substrate pattern is a conductive thermosetting connection using a conductive adhesive.
It is conceivable to connect the capacitor by reflow soldering.

[0013]

However, in the order of the manufacturing process, when the capacitor is first joined by reflow soldering and then the IC chip is joined by a conductive adhesive, the capacitor is joined by the land 51b in the reflow soldering process. There is a possibility that the attached solder may travel on the surface of the pattern and flow to the land 51a to which the IC chip is connected.

The reason why the IC chip is bonded to the land 51a on which the solder has flown with a conductive adhesive is that the IC chip is inclined by the thickness of the solder flowing under the IC chip, and the reliability of the conductive adhesive and the later The mechanical strength when sealing with an epoxy-based adhesive in the process is reduced. That is, if the reflow solder flows excessively, there is a problem that a serious defect may occur after the step of bonding the IC chip with the conductive adhesive.

[0015]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises a crystal vibrating portion in which a crystal oscillator is sealed and an oscillation circuit portion in which an oscillation circuit is sealed. In a crystal oscillator, at least a capacitor and an IC circuit are mounted on a first wiring substrate forming the oscillation circuit, and the capacitor connection land and the IC circuit connection land are connected to each other through a second hole through a second hole. A crystal oscillator characterized by being connected by a wiring board is provided.
In the crystal oscillator according to the present invention, the capacitor is mounted by reflow soldering, and the IC circuit is mounted by conductive thermosetting connection.

[0016]

1 to 3 show an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1A is a perspective view of the external appearance of an example of a crystal oscillator according to the present invention, and FIG. 1B is a diagram illustrating a lid 6 and a container body 4 (of a crystal vibrating section) (hereinafter, referred to as a first container 4). FIG. 3 is a perspective view showing an internal component arrangement in which a container body 7 (of an oscillation circuit unit) (hereinafter, referred to as a second container 7) is separated.

The crystal oscillator shown in FIG. 1A has substantially the same outer shape and dimensions as those of the crystal oscillator described with reference to FIG. That is, its size is about 5 × 3.2 × 1.
The size is 5 mm, and although not shown, it is the same that an external electrode 13 for surface mounting and an electrode 14 for adjustment are provided on the bottom surface, and the same parts will be denoted by the same reference numerals as in FIGS. To avoid complications.

The crystal vibrating part 2 accommodates a crystal vibrator 5 inside a first container 4 made of a shallow box-shaped ceramic substrate, and has a metal lid 6 made of, for example, Kovar to cover the inside thereof. Hermetic sealing can be performed in a vacuum state or a state filled with an inert gas such as nitrogen. Crystal oscillator 5
Is a rectangular thin plate shape, on both surfaces of which metal electrodes 5a are formed by vapor deposition or the like, and an electrode lead portion 5b formed inside the container body 4 is connected to the metal electrode 5a of the crystal unit 5 with a conductive adhesive. Is done. From the electrode lead-out portion 5b, through the through-hole and the printed pattern formed in the inner layer of the container body 4, etc., to the oscillation circuit portion 3 via the connection electrode 10 formed on the upper edge of the second container 7. Connected.

The second container 7 of the oscillating circuit section 3 is also the first container described above.
In the same manner as the container 4 described above, it is formed of a ceramic substrate and houses electronic components constituting an oscillation circuit. These ceramic substrates are often made by a green sheet laminating method, in which alumina is used as a substrate material, molybdenum, tungsten, or the like is used as a conductor material, and a printed pattern is formed by firing.

FIG. 2 shows details of the oscillation circuit section.
FIG. 2A shows the arrangement of the electronic components constituting the oscillation circuit portion viewed from above with the crystal oscillation portion 2 removed, and FIG.
(B) shows a printed pattern on the first wiring board formed on the bottom surface of the second container 7 by removing the electronic component. FIG. 2C shows a cross section along the line AA,
This shows a situation where the chip 8 and the capacitor 9 are electrically connected to the through hole 12c via the pattern 12 on the second wiring board formed in the inner layer. As shown in FIG. 2A, an IC chip 8 and a capacitor 9 are surface-mounted and housed on a first printed pattern formed inside a bottom surface of a second container 7 of the oscillation circuit unit 3. .

From FIG. 2 (c) which shows a front view of the first print pattern of FIG. 2 (b) and a cross section taken along the line AA, the land 11bX for the capacitor is formed through a through hole or a through wire 12c. It is connected to the pattern 12 on the second wiring board formed in the inner layer of the second container 7.
Then, the pattern 12 is connected to the land 11c via the through wire 12c, and further reaches the land 11a for the IC chip formed at the other end of the pattern 11. As described above, the land 11b for the capacitor and the land 11a for the IC chip are connected through the pattern 12 on the second wiring board formed in the inner layer of the second container 7, Land 1 for the capacitor on the wiring board 1
1bX and the land 11a for the IC chip are separated.

Similarly, for the capacitor land 11bY shown in FIG. 2B, similarly to the above-described 11bX, the IC is connected via the pattern on the second wiring board.
Since it is connected to the chip land 11a, extra reflow solder attached to the capacitor land 11b
It is possible to completely prevent the flow into the inside of the C chip, the inclination of the chip, and the contamination of the IC chip land 11a with solder. The second wiring board formed in the inner layer of the second container 7 can be originally used for connecting the crystal oscillator 5, the external electrode 13, and the adjustment electrode 14, and is newly provided with an IC chip. Even if a pattern for connecting the lands of the capacitor is added, the cost hardly increases.

FIG. 3 schematically shows an electronic circuit constituting the crystal oscillator 1 comprising the crystal vibrating section 2 and the oscillation circuit section 3. As described above, the oscillation circuit section is composed of the IC chip and the oscillation circuit section 2.
It is composed of up to three components such as capacitors.

Various methods are known for joining external electrodes of surface-mounted electronic components to lands formed on a printed pattern of a printed circuit board. One example of such a method is shown in FIG. 4, which is used in a crystal oscillator. A specific example of surface mounting of an electric component will be described. FIG. 4A shows a structure in which a gold bump (protrusion) 16 is bonded to an external electrode 15 of an IC chip 8 by, for example, ultrasonic waves. It is formed by melting.
Generally, 30 to 12 if gold wire for wire bonding is used
It is easy to obtain a bump having a diameter of 0 μm. The IC chip 8 is connected to a land 18 which is a part of a wiring pattern formed on the surface of the printed wiring board 17 via a conductive adhesive 19 disposed so as to surround the gold bump 16. The conductive adhesive 19 is fixed to the wiring pattern by so-called conductive thermosetting connection after a predetermined heating, and then a sealing agent is provided between the bottom surface of the IC chip 8 and the surface of the substrate 17 facing the same. Epoxy resin or the like is injected as 20 to prevent mechanical strength and environmental deterioration such as moisture. When the sealant 20 is solidified, its volume is slightly reduced, and pressure is applied to the conductive adhesive 19, which also has the effect of ensuring electrical connection.

FIG. 4B shows the external electrodes 1 of the IC chip 8.
5, the bump 21 with the cut gold wire having a diameter of about 30 μm is bonded by ultrasonic bonding or the like, and the gold-plated land 22 on the surface of the printed wiring board 17 and the bump 21 are also bonded by ultrasonic bonding. Also in this case, the adhesive 2 also serves as a seal.
3 is preferably injected between the bottom surface of the IC chip 8 and the surface of the substrate 17 facing the IC chip 8.

FIG. 4C shows a capacitor 9 for surface mounting.
Is a case where reflow soldering is performed.
After supplying a required amount of solder (solder) having various forms to the joint between the land 11b formed on the surface of the substrate 17 and the electrodes at both ends of the capacitor 9, it is heated by various heat sources to perform soldering. Both are brought into a metallic bonding state.

[0027]

As described above, in the crystal oscillator of the present invention, the printed pattern of the oscillation circuit portion is separated into two portions by the through holes, so that the IC chip is joined to the land of the substrate by the conductive adhesive. Even when the capacitor is bonded to the land by reflow soldering, the reflow solder flows into the land side of the IC chip and
The problem of insufficient mounting of the chip can be solved, and therefore, a long life and high reliability of the whole crystal oscillator can be obtained.

The second layer formed on the inner layer of the container 7
Is originally used for connecting the crystal unit 5, the external electrode 13, and the adjustment electrode 14.
Even if the pattern of land separation of the chip and the capacitor is added, the economics that the cost increase is small cannot be ignored.

[Brief description of the drawings]

FIG. 1 is a perspective view of a crystal oscillator employing a container structure of the present invention.

FIG. 2 is an explanatory diagram showing a print pattern of an oscillation circuit section of the present invention.

FIG. 3 is a schematic diagram showing a circuit configuration of a crystal oscillator.

FIG. 4 is a schematic diagram showing a printed circuit board mounting method of an IC chip and a capacitor.

FIG. 5 is a schematic diagram showing an external shape of a crystal oscillator.

FIG. 6 is an explanatory diagram showing a print pattern of an oscillation circuit section of a conventional example.

[Explanation of symbols]

1 crystal oscillator, 2 crystal oscillation section, 3 oscillation circuit section, 4
Container body (of crystal vibrating part), 5 crystal vibrator, 6
Lid, 7 container body (of oscillation circuit section), 8 IC chip,
9 capacitors, 10 connection electrodes, 11 (print)
Pattern, 11a Land a, 11 (for IC chip)
b Land (for capacitor) b, 11c Land (for through hole) c, 12 Print pattern (for inner layer), 12c Land (for through hole) c, 12s Through hole, 13 External electrode, 16 bump, 19 Conductive bonding Agent, 20 sealant, 21 (wire-made) bump,

Continued on the front page F term (reference) 5J079 AA04 BA43 HA07 HA09 HA16 HA28 HA29 5J108 BB02 CC04 EE03 EE18 GG03 KK04

Claims (3)

[Claims] 1. A crystal oscillator comprising: a crystal vibrating section in which a crystal resonator is sealed; and an oscillation circuit section in which an oscillation circuit is sealed, wherein at least a capacitor and an IC are provided on a first wiring board forming the oscillation circuit. A crystal oscillator having a circuit mounted thereon, wherein the land for capacitor connection and the land for IC circuit connection are connected by a second wiring board via through holes. 2. The oscillation circuit according to claim 1, wherein the second wiring board is formed on a bottom surface of the container of the oscillation circuit.
4. The crystal oscillator according to 1. 3. The crystal oscillator according to claim 1, wherein said capacitor is mounted by reflow soldering, and said IC circuit is mounted by conductive thermosetting connection.