JP2001345639A - Voltage controlled oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface mount voltage controlled oscillator suitable for size reduction. SOLUTION: Circuit elements, including capacitors C1-C10, resistors R1-R4, and inductance elements L1-L4, and a conductive pattern P connected with these circuit elements are formed in thin film on an alumia substrate 1. Semiconductor bare chips, i.e., a diode D1 and transistors Tr1, Tr2, are then wire bonded to the connection lands of the conductive pattern P and an end face electrode 3 being connected with the ground electrode, the input electrode and the output electrode of the conductive pattern P is provided on the side face of the alumia substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount type voltage controlled oscillator (VCO) which is used in a wireless communication device such as a portable telephone.

[0002]

2. Description of the Related Art A conventionally known voltage controlled oscillator solders each circuit component of a resonance circuit, an oscillation circuit and a buffer circuit to a solder land of a conductive pattern provided on a substrate, and shields these circuit components. It is schematically configured to be covered with a cover. The board is composed of a multilayer board,
A microstrip line is provided in the inner layer portion between the ground conductors. The resonance circuit is composed of circuit components such as the microstrip line, the diode, the chip capacitor, and the inductor, and these components are connected to a through hole provided on the substrate through a conductive pattern. The oscillation circuit is composed of transistor, chip resistor, chip capacitor and inductor circuit components.
Similarly, the buffer circuit is composed of circuit components such as transistors, chip resistors, chip capacitors, and inductors.
These components are connected via a conductive pattern.
An end surface electrode is provided on a side surface of the substrate. When the voltage controlled oscillator is surface-mounted on the motherboard, the end surface electrode is soldered to a solder land of the motherboard.

[0003]

In recent years, techniques for miniaturizing circuit components such as chip components and transistors have been remarkably advanced. For example, an ultra-small chip resistor whose external dimensions have been reduced to about 0.6 × 0.3 mm has been developed. And chip capacitors have been put into practical use, and the external dimensions of semiconductor components such as transistors and diodes have also been reduced in size. Therefore, even in the prior art described above, if such a small chip component or semiconductor component is used and these circuit components are mounted on a substrate with a reduced pitch between the components, the voltage controlled oscillator can be increased to some extent. Can be reduced in size. However, there is a limit to the miniaturization of circuit components such as chip components and semiconductor components, and furthermore, when mounting a large number of circuit components on a substrate, it is necessary to prevent short-circuiting of the soldered portion of each circuit component. Therefore, there is a limit in narrowing the pitch between components, and these are major factors that hinder further miniaturization of the voltage controlled oscillator.

[0004] The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to provide a surface mount type voltage controlled oscillator suitable for miniaturization.

[0005]

In order to achieve the above object, in a voltage controlled oscillator according to the present invention, a semiconductor bare chip of a transistor and a diode is mounted on an alumina substrate on which a conductive pattern is formed. Is wire-bonded to the conductive pattern, and an end face electrode connected to the conductive pattern is provided on a side surface of the alumina substrate.

According to such a configuration, at least the semiconductor elements of the transistor and the diode among the circuit components required for the VCO circuit are wire-bonded to the conductive pattern in which the semiconductor bare chip is formed on the alumina substrate. Therefore, these semiconductor elements can be mounted at a high density on an alumina substrate, and a surface mount type voltage controlled oscillator suitable for miniaturization can be realized.

In the above structure, it is preferable that a film of a circuit element including a capacitor, a resistor, and an inductance element is formed on an alumina substrate, and the circuit element is connected to a conductive pattern. And circuit element film forming technology,
Necessary circuit components can be mounted on the alumina substrate at high density.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a voltage controlled oscillator, FIG. 2 is a plan view of an alumina substrate showing a circuit configuration layout, and FIG. Is a back view of the alumina substrate, and FIG. 4 is a VCO
FIG. 5 is a perspective view showing an end face electrode, FIG. 6 is a sectional view of the end face electrode, FIG. 7 is an explanatory view showing a relationship between a semiconductor bare chip and connection lands, and FIG. 8 shows a manufacturing process of a voltage controlled oscillator. FIG.

As shown in FIG. 1, a voltage controlled oscillator (VCO) according to an embodiment of the present invention includes an alumina substrate 1 on which circuit components of a VCO circuit described later are mounted, and a shield cover attached to the alumina substrate 1. 2 and is a surface-mounted component to be soldered to a motherboard (not shown) of a mobile phone or the like. The alumina substrate 1 is formed in a rectangular flat plate shape. The alumina substrate 1 is obtained by cutting a large-sized substrate into strip-shaped divided pieces, and further subdividing the divided pieces. The shield cover 2 is formed by bending a metal plate into a box shape, and circuit components on the alumina substrate 1 are covered with the shield cover 2.

As shown in FIG. 2, circuit components of the VCO circuit and a conductive pattern for connecting them are provided on the surface of the alumina substrate 1. As shown in FIG.
On the back surface of the alumina substrate 1, a conductive pattern as a back electrode is provided. The VCO circuit according to the present embodiment has a circuit configuration as shown in FIG. 4, and each circuit component shown in FIG. 2 is denoted by a reference numeral corresponding to the circuit diagram in FIG. However, FIG. 4 shows an example of the VCO circuit, and the present invention can be applied to other VCO circuits.

As shown in FIG. 4, the VCO circuit includes a resonance circuit, an oscillation circuit, and a buffer circuit.
4, inductance elements L1 to L4, diode D1,
The conductive patterns connecting the transistors Tr1 and Tr2, the conductive paths S1 and S2, and each circuit component are provided on the surface of the alumina substrate 1. This conductive pattern is formed, for example, of Cr, Cu, or the like by using a thin film technique such as sputtering, and is denoted by a symbol P in FIG.

As shown in FIG. 2, a ground electrode (GND), input electrodes (Vcc, Vctl), and an output electrode (FRout) of a VCO circuit are formed at the end of the alumina substrate 1. Is constituted by a part of the conductive pattern P. Grounding electrode and input electrode (Vcc, Vctl)
The output electrode (FRout) is formed only on two long sides facing each other of the rectangular alumina substrate 1, and is not formed on the other two short sides facing each other. In other words, GND electrodes are formed at three places at both corners (corners) on one long side of the alumina substrate 1 and at the center, and a Vcc electrode and a Vctl electrode are formed between these GND electrodes. In addition, GND electrodes are formed at both corners on the other long side of the alumina substrate 1 and three places near the corners.
Two FRout electrodes are formed between the electrodes. As will be described later, the two long sides of the alumina substrate 1 correspond to the dividing lines when the large-sized substrate is cut into strip-shaped divided pieces, and the two short sides of the alumina substrate 1 further connect the divided pieces. It corresponds to the division line when subdividing.

On the other hand, as shown in FIG.
The conductive pattern P1 (rear electrode) provided on the back surface of each of the ground electrodes (GND) and the input electrodes (Vcc, V
ctl) and the output electrode (FRout), and both are electrically connected via the end face electrode 3 as shown in FIGS. The end face electrode 3 is obtained by sequentially laminating a Ni base plating layer and an Au plating layer on an Ag thick film layer. The lowermost Ag thick film layer is formed by forming a thick Ag paste containing no glass component. It is made of a low-temperature fired material fired at about 200 ° C. Further, the Ni underlayer plating layer of the intermediate layer facilitates adhesion of the Au plating layer, and the uppermost Au layer is used.
The plating layer is for preventing the lowermost layer of Ag from depositing on the solder when the end face electrode 3 is soldered to a solder land on a mother substrate (not shown). Then, in the completed product of the voltage-controlled oscillator in which the shield cover 2 is attached to the alumina substrate 1, the leg 2 a bent and formed on the side surface of the shield cover 2 is soldered to the end face electrode 3 which is electrically connected to the ground electrode (GND). The shield cover 2 is grounded at the four corners of the alumina substrate 1.

Among the circuit components of the VCO circuit, the capacitors C1 to C10 are formed by laminating an upper electrode on a lower electrode via a dielectric film such as SiO ₂ , and these are formed as thin films by sputtering or the like. Have been. A Cu layer is provided on the surface of the upper electrode, and the Q of the resonance circuit is enhanced by the Cu layer. The lower and upper electrodes of the capacitors C1 to C10 are connected to a conductive pattern P. As shown in FIG. 2, the conductive pattern P between the capacitor C8 and the Vcc electrode, the conductive pattern P between the capacitor C8 and the RFout electrode, An adjacent portion (air gap) G for discharge is formed in the conductive pattern P between C10 and the Vctl electrode. The adjacent portion G is constituted by a protruding portion provided on each of the conductive pattern P and the GND electrode facing each other or a pair of conductive patterns P arranged side by side on each other. They face each other with a predetermined gap. In this case, since the dimensional accuracy of both the conductive pattern P and the GND electrode is improved by the thin film technology, the gap dimension of the adjacent portion G can be narrowed, and discharge at a low voltage is possible. Also,
Among the capacitors C1 to C10, the capacitors C1 to C10
4, C6 and C7 are formed in a simple square shape, but the capacitors C5 and C8 to C10 are formed in different shapes combining two squares. That is,
The capacitors C5, C8, and C10 have a shape in which another rectangle is shifted from one side of one rectangle and protrude, and the capacitor C9 has a shape in which two rectangles are connected in an L-shape. Part (or all) of capacitors C1 to C10
With such an irregular shape, a limited space on the alumina substrate 1 is effectively used, and a capacitor having a desired capacitance value can be mounted at a high density.

Further, of the capacitors C1 to C10, the capacitor C9 is constituted by two grounding capacitors, which are connected in parallel via a pair of conductive patterns P separated from each other. That is, as shown in FIG. 2, the grounding capacitors C9 and L
In the grounding capacitor C9 formed in the shape of a letter, each one electrode portion is connected to the conductive pattern P connected to the GND electrode, while each other electrode portion is connected via a separate conductive pattern P separated from each other. Oscillation transistor Tr1
Are connected to the collector electrode. As is clear from FIG. 4, the capacitor C9 is provided between the collector of the oscillation transistor Tr1 and the ground.
Is set by two grounding capacitors connected in parallel via a pair of conductive patterns P separated from each other. Therefore, the transistor Tr1
Of the entire conductive pattern P from the collector electrode to the ground through the capacitor C9, the grounding effect of the grounding capacitor C9 is improved, and each grounding capacitor C9 and each conductive pattern P
Therefore, the parasitic oscillation frequency can be increased by setting this frequency to be equal to or higher than the operating point frequency of the transistor Tr1.

[0016] Among the circuit components of the VCO circuit, the resistor R1~R4 for example a resistive film such as TaSiO ₂ which was formed by using a thin film technology such as sputtering, SiO ₂ or the like, if necessary on the surface Is provided. As shown in FIG. 2, among the four resistors R1 to R4,
R3 is formed as a thin film at a position close to each other on the alumina substrate 1, and the remaining resistor R4 is formed as a thin film juxtaposed at a position distant from the resistors R1 to R3. Thus, the resistance R1
Since R3 to R3 are formed close to each other, even if the resistance values of the resistors R1 to R3 vary from a desired value, the ratio of the variation among the resistors R1 to R3 can be made the same. it can. As is clear from FIG.
Reference numerals 1 to R3 denote base bias voltage dividing resistors of the oscillation transistor Tr1 and the amplification transistor Tr2.
+ R2) / (R1 + R2 + R3) × Vcc is applied to the base of the transistor Tr1, and R1 / (R1 + R2 +
R3) × Vcc is applied to the base of the transistor Tr2. Here, a resistor R which is a voltage dividing resistor for base bias is used.
As described above, since the ratio of the variation among all the resistors 1 to R3 is always the same, the trimming of the resistance values of the resistors R1 to R3 becomes unnecessary. On the other hand, the resistor R4 is an emitter resistor of the oscillation transistor Tr1, and a current flows from the Vcc electrode through the collector and the emitter of the transistor Tr2 to the collector and the emitter of the transistor Tr2, and further grounded through the resistor R4 and the inductance element L4. You. Here, among the resistors R1 to R4, since the resistor R4, which is the emitter resistor, has the largest contribution to the amplification of the transistors Tr1 and Tr2, only the resistor R4 is trimmed so that the current value is constant, and the output is adjusted. I have to do it.

Further, among the circuit components of the VCO circuit, the inductance elements L1 to L4 and the conductive paths S1, S2
Is formed of Cr, Cu, or the like by using a thin film technique such as sputtering, and is connected to the conductive pattern P.
A Cu layer is provided on the surface of each of the inductance elements L1 to L4, and the Cu layer enhances the Q of the resonance circuit. Inductance elements L1, L2 and L4
Are formed in a rectangular spiral shape, and one end of each is wire-bonded to a Vctl electrode or a conductive pattern P for grounding. Inductance element L2
Is for setting a resonance frequency for setting an approximate resonance frequency, and the inductance element L3 is an inductance element L2.
Is connected to the other end. The inductance element L3 is an adjustment conductive pattern for adjusting the resonance frequency. As shown by a broken line in FIG. 2, by trimming and cutting the inductance element L3, the number of turns of the inductance element L2 increases and the resonance frequency is reduced. Adjustments are made. In this case, the trimmed inductance element L3
Is made the same as the conductor width of the inductance element L2, the characteristic impedance of the inductance element L2 and the inductance element L3 does not change,
Oscillation with a good C / N ratio can be obtained.

The conductive paths S1 and S2 are unbalanced / balanced conversion elements for converting an unbalanced signal into a balanced signal and outputting the signal, and are formed as a thin film on the alumina substrate 1 as described above. These conductive paths S1 and S2 are formed in a crank shape so as to face each other with a predetermined gap on the alumina substrate 1, and both ends of one conductive path S1 are connected to the collector electrode of the transistor Tr2 and the capacitor C8. The other end of the other conductive path S2 is connected to a pair of RFs.
connected to out electrode. In this case, since the dimensional accuracy of the conductive paths S1 and S2 formed as a thin film is high, both conductive paths S1 and S2 are formed.
A desired degree of coupling can be ensured by narrowing the gap between S1 and S2, and a small unbalanced / balanced conversion element can be provided in a limited space on the alumina substrate 1.

The diode D1 and the transistors Tr1 and Tr2 among the circuit components of the VCO circuit are
A semiconductor bare chip is mounted on a connection land of a conductive pattern P formed as a thin film on an alumina substrate 1 and the semiconductor bare chip is wire-bonded to the conductive pattern P. That is, as shown in FIG.
The semiconductor bare chip has a square shape, and one electrode provided on the lower surface thereof is fixed to a connection land using a conductive adhesive such as cream solder or conductive paste, and the other electrode provided on the upper surface of the semiconductor bare chip Is the conductive pattern P
Are wire-bonded to predetermined portions. Also,
The semiconductor bare chips of the transistors Tr1 and Tr2 also have a square shape, and the collector electrodes provided on the lower surfaces thereof are fixed to the connection lands using a conductive adhesive, and the base electrodes and the emitter electrodes are connected to predetermined portions of the conductive pattern P by wires. Bonded. Similarly to the end face electrode 3 described above, a Ni base plating layer and an Au plating layer are sequentially laminated on these connection lands. Here, as shown in FIG. 7A or 7B, the area of the connection land 5 is formed to be smaller than the lower area of the semiconductor bare chip 4, and by adopting such a configuration, the semiconductor bare chip Since the pool of the conductive adhesive is secured under the semiconductor chip 4, an accident that the conductive adhesive protrudes from the outer shape of the semiconductor bare chip 4 and short-circuits with the surrounding conductive pattern P can be prevented beforehand. Further, an opening 5a is provided in the connection land 5, and since an excess of the conductive adhesive is accumulated in the opening 5a, it is possible to more reliably prevent the conductive adhesive from protruding. .

Next, the manufacturing process of the voltage controlled oscillator configured as described above will be described mainly with reference to FIG.

First, as shown in FIG. 8A, after sputtering the whole surface of the alumina substrate 1 with TaSiO ₂ or the like,
This is etched into a desired shape to form the resistance film 6, thereby forming a portion corresponding to the resistors R1 to R4. Next, as shown in FIG. 8B, Cr or Cu or the like is sputtered from above the resistive film 6, and is etched into a desired shape to form the lower electrode 7, and then as shown in FIG. As described above, SiO ₂ or the like is sputtered from above the lower electrode 7 and is etched into a desired shape to form the dielectric film 8. Next, as shown in FIG. 8D, after sputtering Cr, Cu, or the like from above the dielectric film 8, this is etched into a desired shape to form the upper electrode 9. As a result, the conductive pattern P and the inductance elements L1 to L4 and the conductive paths S1,
A portion corresponding to S2 is formed, and a laminate of the lower electrode 7, the dielectric film 8, and the upper electrode 9 forms the capacitors C1 to C1.
A portion corresponding to C10 is configured. Next, after a Cu layer is formed on the surfaces of the portions corresponding to the inductance elements L1 to L4 and the capacitors C1 to C10 by plating or thin film technology, as shown in FIG. The film 10 is formed. Next, as shown in FIG. 8 (f), after sputtering Cr, Cu, or the like on the entire back surface of the alumina substrate 1, this is etched into a desired shape to form the back electrode 11, whereby the conductive material on the back surface side is formed. A portion corresponding to the pattern P1 is configured.

The steps shown in FIGS. 8A to 8F described above are performed on a large-sized substrate made of an alumina material in which division grooves extending in a lattice pattern are cut in the vertical and horizontal directions. The steps shown in FIGS. 8G to 8J are performed on the strip-shaped divided pieces obtained by cutting the large-sized substrate along the dividing grooves in one direction.

That is, after cutting the large-sized substrate into strip-shaped divided pieces, as shown in FIG. 8 (g), a thick Ag layer 12 is formed on both end faces of the alumina substrate 1 which is the cut surface of the divided pieces. The grounding electrode (GND) and the input electrode (V) of the conductive patterns P, P1 provided on the front and back surfaces of the alumina substrate 1 are formed.
(cc, Vctl) and the output electrode (FRout) are conducted by the Ag layer 12. The Ag layer 12 is formed on the end face electrode 3 described above.
Is a low-temperature fired material made of an Ag paste containing no glass component. In addition, such Ag layer 1
It is also possible to perform the thick film forming step 2 on one strip-shaped divided piece. However, if a plurality of divided pieces are overlapped with a slight gap, the Ag layer 12 can be divided into a plurality of pieces. A thick film can be formed simultaneously on the divided pieces, which is suitable for mass production. Next, after a Ni underlayer and an Au layer are sequentially plated on each surface of the connection land on which the Ag layer 12 and the semiconductor bare chip are mounted, as shown in FIG. 8H, a diode D1 and a transistor are provided on each connection land. The semiconductor bare chips of Tr1 and Tr2 are fixed using a conductive adhesive such as cream solder or conductive paste. In this case, as described above, since the area of the connection land is formed smaller than the lower area of the semiconductor bare chip, the conductive adhesive is prevented from protruding from the semiconductor bare chip, and the conductive adhesive is applied to the semiconductor bare chip. Undesired short circuit with the surrounding conductive pattern P is prevented. Next, as shown in FIG. 8 (i), each semiconductor bare chip is wire-bonded to a predetermined portion of the conductive pattern P, and then, as shown in FIG. 8 (j), a resistor R4 which is an emitter resistor is trimmed and output. At the same time, the resonance frequency is adjusted by trimming the inductance element L3, which is an adjustment conductive pattern.
In this case, the adjustment of the resonance frequency is performed in the state of the strip-shaped divided pieces before being divided into the individual alumina substrates 1, and the grounding electrodes (GND) are provided at the corners of each alumina substrate 1. The ground electrode (GND) is always located between the input electrode (Vcc, Vctl) and the output electrode (FRout) provided on the alumina substrate 1 to be adjusted. The circuit is not adversely affected.

Next, a shield cover 2 is attached to each of the alumina substrates 1 of the strip-shaped divided pieces.
By soldering the leg piece 2a to the end face electrode 3 conducting to the ground electrode (GND), the divided piece is subdivided into the individual alumina substrates 1 along the other divided groove, as shown in FIG. A voltage-controlled oscillator can be obtained.

According to the voltage controlled oscillator according to the above-described embodiment, the capacitors C1 to C10, the resistors R1 to R4, the inductance elements L1 to L4, and the conductive paths S1 and S2 are formed on the alumina substrate 1. A circuit element and a conductive pattern P connected to these circuit elements are formed as a thin film, a diode D1 and a semiconductor bare chip of transistors Tr1 and Tr2 are wire-bonded on the alumina substrate 1, and a conductive layer is formed on the side surface of the alumina substrate 1. Since the end electrodes 3 connected to the ground electrode and the input / output electrode of the pattern are provided, the components for the VCO circuit can be mounted on the alumina substrate 1 at high density using thin film technology and wire bonding of semiconductor elements. In addition, a surface-mount type voltage controlled oscillator suitable for miniaturization can be realized. Further, since the Cu layers are provided on the surfaces of the capacitors C1 to C10 and the inductance elements L1 to L4 formed as thin films, the Q of the resonance circuit can be increased. Although the case where the semiconductor element and the semiconductor element are mounted on the same alumina substrate has been described, only the semiconductor bare chip is wire-bonded to the alumina substrate, and this alumina substrate is formed on another substrate on which a circuit element such as a capacitor is formed as a thin film or a thick film. It is also possible to configure so as to be soldered on top.

[0026]

The present invention is embodied in the form described above and has the following effects.

Semiconductor bare chips of transistors and diodes are mounted on an alumina substrate on which a conductive pattern is formed, and these semiconductor bare chips are wire-bonded to the conductive pattern, and end electrodes connected to the conductive pattern are formed on the side surfaces of the alumina substrate. With this arrangement, among the circuit components required for the VCO circuit, semiconductor elements such as transistors and diodes can be densely mounted on an alumina substrate using wire bonding of a semiconductor bare chip, and surface mounting suitable for miniaturization. A type of voltage controlled oscillator can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a voltage controlled oscillator according to an embodiment of the present invention.

FIG. 2 is a plan view of an alumina substrate showing a circuit configuration layout.

FIG. 3 is a rear view of the alumina substrate.

FIG. 4 is an explanatory diagram of a VCO circuit.

FIG. 5 is a perspective view showing an end face electrode.

FIG. 6 is a sectional view of an end face electrode.

FIG. 7 is an explanatory diagram showing a relationship between a semiconductor bare chip and connection lands.

FIG. 8 is an explanatory diagram illustrating a manufacturing process of the voltage controlled oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alumina substrate 2 Shield cover 3 End face electrode 4 Semiconductor bare chip 5 Connection land 5a Opening 6 Resistive film 7 Lower electrode 8 Dielectric film 9 Upper electrode 10 Protective film 11 Back electrode 12 Ag layer C1-C10 Capacitors R1-R4 Resistance L1-L4 Inductance element Tr1 to Tr2 Transistor S1, S2 Conductive path P, P1 Conductive pattern

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiko Ueda 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Hiroshi Sakuma 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alp F-term (reference) within SUMITOMO ELECTRIC CO., LTD.

Claims (2)

[Claims] A semiconductor bare chip of a transistor and a diode is mounted on an alumina substrate on which a conductive pattern is formed, and these semiconductor bare chips are wire-bonded to the conductive pattern, and the conductive pattern is formed on a side surface of the alumina substrate. A voltage controlled oscillator comprising an end face electrode to be connected. 2. The circuit according to claim 1, wherein a film of a circuit element including a capacitor, a resistor and an inductance element is formed on the alumina substrate, and the circuit element is connected to the conductive pattern. And a voltage controlled oscillator.