JP2001284490A - Grounding structure for high-frequency wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency grounding structure which exhibits excellent high frequency characteristic that prevent the amplification factor of an amplifier from deteriorating and that prevents abnormal oscillation, by surely performing high frequency grounding. SOLUTION: The structure grounded for the high-frequency wave has a through hole 38, the size of which is slightly smaller than that of an MMIC (monolithic microwave integrated circuit) 30 being mounted and located directly under the MMIC 30. A good conductive metal member 32 that enhances the high-frequency grounding is installed between the MMIC 30 and a metal board 35 located under a circuit board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of a high-frequency circuit component, and more particularly to an active element such as a transistor and a microwave band such as an MIC (microwave integrated circuit) integrating an active element and a passive element. And a high-frequency grounding structure in a high-frequency circuit component used in a high-frequency region such as a millimeter wave band.

[0002]

2. Description of the Related Art In recent years, due to the depletion of frequency resources, system applications in microwave and millimeter wave bands which have not been used so far are expected. Microwaves and millimeter waves have the advantage of higher spatial attenuation compared to other low frequencies, and have the advantage that the wireless transmission distance is short so that the frequency can be folded back. Practical application of a high-speed wireless LAN system, a cordless camera system, an image monitor system, a high-speed wireless network, and the like, which are suitable for high-speed transmission of information, is proceeding at a rapid pace.

[0003] In order to realize such a system, MI
High frequency circuit components such as C are used. The MIC has
A hybrid MIC (HMI) in which a transmission path is formed on a dielectric substrate such as alumina and chip components are mounted thereon
C), and a monolithic MIC (MM) in which passive elements and active elements are collectively manufactured on a semiconductor substrate such as GaAs or Si.
IC) and the like.

A conventional mounting structure of a high-frequency circuit component will be described below with reference to FIGS. FIG. 8 is a diagram showing an example of a high-frequency unit, and FIG. 9 is an external perspective view when a conventional MMIC chip is mounted on a substrate.
Is a mounting cross-sectional view when a conventional MMIC chip is mounted on a substrate, and FIG. 11 is a diagram illustrating an example of a feedback amount in a conventional mounting method.

[0005] The microwave / millimeter wave integrated circuit unit
For example, as shown in FIG. 8, a plurality of dielectric substrates 12 to 15 are provided side by side in a cavity of a metal housing 11, and one or a plurality of high-frequency circuit components package MMIC 12a are provided on each dielectric substrate. Or MMIC
The chip 13a is mounted, and although not shown, signal lines between the dielectric substrates are electrically connected by wire bonding using thin metal wires. A connector 16 connected to the signal line of the dielectric substrate and the ground is provided on the side wall of the metal housing 11 and is connected to an external circuit.

Although not shown, as a mounting method of the high frequency circuit component, when the MMIC chip 13a is mounted, there are wire bonding using a thin metal wire, ribbon bonding, and flip chip bonding for directly connecting using a metal bump. Also, package MMI
When C12a is mounted, there is a connection method using a conductive adhesive or soldering other than the connection method described above. In wire bonding, it is general to reduce the loss by bonding a plurality of wires in parallel.

FIG. 9 shows a conventional example in which one package MMIC is mounted on one dielectric substrate. As shown in FIG. 9, a dielectric substrate 21 is joined to a conductive metal substrate 22 such as Kovar (Fe—Ni—Co alloy) by brazing or soldering with gold tin (AnSn) or the like. A package MMIC 24 such as a low-noise amplifier or a high-output amplifier is mounted on 21.

The package MMIC 24 has an input / output terminal 2
4a, 24b and ground terminals 24c, 24d. The input / output terminals 24a, 24b are electrically connected to microstrip lines 25, 26 formed on the dielectric substrate 21 by a conductive adhesive or the like. Terminal 24
c and 24d are connected to ground patterns 27 and 28, respectively. The ground patterns 27, 28 on the front surface and the solid ground 29 on the rear surface are connected by through holes 27a, 28a.

However, in the above configuration, the ground on the upper surface of the dielectric substrate 21 is connected to the back surface through the through holes 27a and 28a.
In this case, the high frequency grounding of the package MMIC 24 cannot be taken due to the presence of the inductance components a and 28a, and the amplification factor of the amplifier may be reduced.

As a countermeasure for this problem, although not shown, capacitors are mounted between the ground terminals 24c and 24d of the package MMIC 24 and the through holes 27a and 28a, respectively, and a series resonance is caused by the inductance components of the capacitors and the through holes 27a and 28a. There is a method of short-circuiting the ground on both sides at high frequency.

However, the short circuit occurs only in a limited frequency band in the vicinity of the resonance frequency. Further, even at the resonance frequency, the short circuit cannot be completely made due to the series resistance of the through hole, the loss resistance of the capacitor, and the like. There is.

As shown in the package MMIC mounting cross-sectional view of FIG.
In some cases, the ground terminals 24c and 24d may jump from the output terminal 24b of the IC 24 to the input terminal 24a, causing spatial coupling and returning. FIG. 11 shows an example of the characteristics. In the case of an amplifier having a large amplification factor, oscillation may occur at a frequency with a large feedback amount (33 GHz in this example).

[0013]

As described above, the high-frequency characteristics are extremely deteriorated due to the above-mentioned conventional mounting method of high-frequency circuit components or the physical structure of the high-frequency components. In the worst case, oscillation at an unnecessary frequency occurs. For example, there is a problem that characteristics as originally designed cannot be obtained.

The present invention has been made in view of the above-mentioned conventional circumstances. Even in an ultra-high frequency band such as a microwave band or a millimeter wave band, the high-frequency grounding is reliably performed to reduce the amplification factor of the amplifier. It is an object of the present invention to provide a high-frequency grounding structure that can obtain favorable high-frequency characteristics such as preventing abnormal oscillation and preventing abnormal oscillation.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention provides a package MMI on a circuit board.
A through hole slightly smaller than the MMIC component to be mounted is formed directly below the C component, and a good conductive metal for enhancing high-frequency grounding is disposed in a gap between the MMIC component and the metal substrate below the circuit board.
Also, the connection between the metal substrate and the good conductive metal for ground reinforcement
It is performed by brazing, soldering, or using a conductive adhesive.

[0016]

Embodiments of the present invention will be described with reference to the drawings. The high-frequency grounding structure according to the embodiment of the present invention includes a dielectric substrate having a microstrip line and a ground pad formed on a front surface and a solid ground formed on a back surface, and a metal ground integrated with the dielectric substrate. Are bonded to each other, and a high-frequency grounding member is disposed in a through hole provided in the dielectric substrate, and the high-frequency grounding member is bonded to the ground pad and the metal substrate. Is grounded at high frequency. Thereby, by reliably performing high-frequency grounding, it is possible to obtain a good high-frequency characteristic such as preventing a decrease in the amplification factor of the amplifier and preventing abnormal oscillation.

Further, the mounting structure of the high-frequency circuit component according to the embodiment of the present invention includes a dielectric substrate having a microstrip line formed on the front surface and a solid earth formed on the back surface, and a metal substrate joined to the solid earth. A high-frequency circuit component is mounted on the surface of the dielectric substrate, a through-hole is provided immediately below the high-frequency circuit component, and a high-frequency grounding member is disposed on the metal substrate.

The mounting structure of the high-frequency circuit component according to the embodiment of the present invention includes a dielectric substrate having a microstrip line formed on the front surface and a solid ground formed on the back surface, and a metal substrate bonded to the solid ground. A high frequency circuit component is mounted on the surface of the dielectric substrate, a through hole is provided directly below the high frequency circuit component, and a threshold is provided on the metal substrate to prevent high frequency coupling of the input / output terminals. A grounding member is provided.

The mounting structure of the high-frequency circuit component according to the embodiment of the present invention includes a dielectric substrate having a coplanar line formed on the front surface and a solid ground formed on the back surface, and a metal substrate bonded to the solid ground. , A high-frequency circuit component is mounted on the surface of the dielectric substrate, a through-hole is provided immediately below the high-frequency circuit component, and a high-frequency grounding member is disposed on the metal substrate.

In the mounting operation of the high-frequency circuit component, a projection having the function of a high-frequency grounding member may be formed on the metal substrate.

A high-frequency grounding structure according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an exploded perspective view illustrating a high-frequency grounding structure according to an embodiment of the present invention, as viewed from a substrate pattern surface. In the schematic structure according to the embodiment of the present invention, a metal substrate 35 and a dielectric substrate 39 are integrated, and a good conductive metal member 32 for enhancing high-frequency grounding is installed in a through hole 38 provided in the dielectric substrate 39. The package MMIC chip 30 is mounted thereon and fixed on the metal housing 36.

Hereinafter, a specific example of the embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a package MMI which is a low-noise amplifier as an example showing the configuration of the present invention.
FIG. 4 is an exploded perspective view when the C chip 30 is mounted on a ceramic substrate 39 having a relative dielectric constant of 10.0 and a thickness of 0.25 mm. FIG. 2 is a sectional view of the center of the package MMIC chip 30.

Package MMI on ceramic substrate 39
A through-hole 38 is opened immediately below the mounting portion of the C chip 30, and a highly conductive metal member 32 for enhancing high-frequency grounding is inserted. The ceramic substrate 39
There is no through hole on the top, but only a ground pad pattern 42 for mounting components of the package MMIC chip 30.

Next, a brief description will be given of a mounting procedure for mounting the high-frequency integrated circuit module of the present invention on a microwave / millimeter-wave integrated circuit unit housing. Ceramic substrate 3
9 is a Kovar plate 35 (Fe-N
After being integrated by brazing or soldering using gold tin (AuSn) to an i-Co alloy), a metal member that is a highly conductive metal is formed on the Kovar plate 35 exposed from the through hole direction of the ceramic substrate 39. 32 is fixed by brazing, soldering, or a conductive adhesive. The metal member 32 and the ground pad 42 are connected, and the ground pad 42 and the MMIC are connected.
The chip 30 is connected to the ground terminal.

As shown in FIG. 3, the good conductive metal member 52 to be grounded at a high frequency is connected to the package MMIC chip 3.
With a terminal shape of 0, a structure is provided in which a gap is provided between the input and output terminals, so that coupling between the input and output terminals can be suppressed and abnormal oscillation can be suppressed. 1 and 3, the input / output terminals of the MMIC chip 30 have a structure in which the input / output terminals are escaped so as not to short-circuit with the metal members 32 and 52. FIG. 3 is an exploded perspective view of a metal member according to another embodiment of the present invention, viewed from a substrate pattern surface.

FIG. 4 shows the coupling characteristics between the input and output terminals in this embodiment in comparison with the conventional example. FIG. 4 is a diagram illustrating an example of a feedback amount in the mounting method according to the embodiment of the present invention. It can be seen that the provision of the threshold reduces the feedback amount in a wide frequency band and does not sharply increase the feedback amount that causes abnormal oscillation at a specific frequency.

In the other embodiment, as shown in FIG. 5, the same effect can be obtained by directly etching the base metal plate 35 to have a structure in which the base metal plate 35 has a metal member 62. In addition, the number of steps for mounting the metal member 62 can be reduced.

As in the case of the above embodiment, the metal member 6
2 has a structure in which the input / output terminal of the MMIC chip 30 escapes so that the input / output terminal of the MMIC chip 30 is not short-circuited to the metal member 62, and is provided with a threshold for preventing direct high-frequency coupling in the input / output line. Such a structure is also conceivable.

In another embodiment, the MM
MMI having coplanar line such as IC bare chip
The same applies to the ground structure for the C chip component, as shown in FIG. FIG. 6 shows an MM having a coplanar line in a high frequency grounding structure according to another embodiment of the present invention.
FIG. 3 is an exploded perspective view showing a grounding structure for an IC chip component.

In the example shown in FIG. 6, on a dielectric substrate 39 provided with a microstrip coplanar converter in the signal line 33 and the ground pattern 72, the chip is slightly smaller than the chip component just below the component of the MMIC chip 70 to be mounted. A through hole 38 is opened, and a high-conductive metal member 71 for high-frequency grounding is arranged in a gap with the metal substrate 35 below the circuit board.

However, the upper surface of the metal member 71 in this case is desirably flat. The mounting state is as shown in the perspective view of FIG. 7, and the MMIC bare chip 70 is made of gold tin (AuSn).
After the connection, the signal line and the ground line are connected by wire bonding. FIG. 7 is an external perspective view showing an embodiment in which an MMIC chip component of a coplanar line is mounted in a high-frequency grounding structure according to another embodiment of the present invention.

Also in this case, the same effect can be obtained by directly etching the Kovar plate, which is the metal substrate 35 serving as the base, and having the metal member 62 of FIG.

In each of the embodiments described above, the simplest case in which only one high-frequency integrated circuit (MIC, MMIC) is mounted is described. Obviously it is possible to do. Also, grounding of active elements such as microcapacitors and thin-film resistors can be positively used as a method for suppressing parasitic inductance.

According to the high-frequency grounding structure of the embodiment of the present invention, the grounding structure around the MIC and MMIC, which are high-frequency integrated circuits, even in an ultra-high frequency band such as a microwave / millimeter wave band, By forming a through hole 38 directly below the chip component and disposing a highly conductive metal member for high-frequency ground reinforcement in a gap between the base metal substrate below the circuit board, the parasitic inductance with respect to the ground of the MIC and MMIC is reduced. A remarkable effect can be obtained in that the characteristics can be greatly reduced, good high-frequency characteristics can be obtained, and characteristics as designed can be obtained without problems such as oscillation at unnecessary frequencies.

[0035]

According to the present invention, the solid earth is bonded to the dielectric substrate having the microstrip line and the ground pad formed on the front surface and the solid ground formed on the back surface, and the metal substrate integrated with the dielectric substrate. A high-frequency grounding member is arranged in a through hole provided in the dielectric substrate, and the high-frequency grounding member is joined to the ground pad and the metal substrate, so that the ground pad is connected to the metal substrate via the high-frequency grounding member. Since it has a high-frequency grounding structure that is grounded,
High-frequency grounding can be reliably performed, and there is an effect that favorable high-frequency characteristics such as prevention of a decrease in the amplification factor of the amplifier and prevention of abnormal oscillation can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a high-frequency grounding structure according to an embodiment of the present invention as viewed from a substrate pattern surface.

FIG. 2 is a cross-sectional view illustrating a mounting method according to an embodiment of the present invention.

FIG. 3 is an exploded perspective view of a metal member according to another embodiment of the present invention, viewed from a substrate pattern surface.

FIG. 4 is a diagram illustrating an example of a feedback amount in the mounting method according to the embodiment of the present invention.

FIG. 5 is an exploded perspective view showing that a metal member is provided on a metal substrate in the high-frequency grounding structure according to another embodiment of the present invention.

FIG. 6 is an exploded perspective view showing a grounding structure for an MMIC chip component having a coplanar line in a high-frequency grounding structure according to another embodiment of the present invention.

FIG. 7 is an external perspective view showing an embodiment in which an MMIC chip component of a coplanar line is mounted in a high-frequency grounding structure according to another embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of a high-frequency unit.

FIG. 9 is an external perspective view when a conventional MMIC chip is mounted on a substrate.

FIG. 10 is a mounting cross-sectional view when a conventional MMIC chip is mounted on a substrate.

FIG. 11 is a diagram illustrating an example of a feedback amount in a conventional mounting method.

[Explanation of symbols]

11, 25, 36 ... metal housing, 12 to 15, 21, 3
9: Dielectric substrate, 12a, 24, 30 ... Package M
MIC, 13a, 70: MMIC chip, 16: Connector, 22, 35: Metal substrate, 23, 31: Screw,
24a, 24b: input / output terminal, 24c, 24d: ground terminal, 25, 26: microstrip line, 27, 28: ground pattern, 27a, 28a
… Through hole, 29… solid earth, 32,52,
71: metal member, 33: board pattern, 34: screw through hole, 37: screw tap, 38: through hole, 42
... Earth pad pattern, 62 ... Projection on metal substrate,
72… Earth pattern

Claims (1)

[Claims] 1. A solid ground is formed on a back surface of a dielectric substrate having a microstrip line and an earth pad formed on a front surface thereof, the solid earth is bonded to a metal substrate, and a high-frequency wave is formed in a through hole provided in the dielectric substrate. A grounding member is arranged, and the high-frequency grounding member is joined to the ground pad and the metal substrate, whereby the ground pad is grounded to the metal substrate via the high-frequency grounding member. Grounding structure.