JP3181036B2 - Mounting structure of high frequency package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency package mounting structure, and more particularly to a high-frequency package suitable for housing or mounting a high-frequency semiconductor device in a microwave band to a millimeter wave band. The present invention relates to a mounting structure for reducing transmission loss of a high-frequency signal and connecting to an external circuit board.

[0002]

2. Description of the Related Art Hitherto, a high-frequency wiring board for handling microwave and millimeter-wave signals, for example, a semiconductor device package as a typical application example thereof is formed by an insulating substrate made of a dielectric and a frame. It has a structure in which a semiconductor element is housed in a cavity and this is hermetically sealed with a lid.

When the semiconductor element housed in the cavity is a high-frequency element, the wiring connected to the high-frequency element and the mounting of the high-frequency package on an external circuit board also have a special structure.

For example, a high-frequency signal transmission line such as a strip line electrically connected to a high-frequency element is drawn out from the inside of the cavity to the outside through a frame, and is further passed through a side surface of a dielectric substrate. The wiring is routed to the bottom surface of the board, and the bottom line and the wiring layer of the external circuit board are connected and mounted via an adhesive such as solder.

As another example, a high-frequency line is formed on the bottom surface of a dielectric substrate of a high-frequency package, and the high-frequency line and the high-frequency element are connected by a through-hole conductor provided to penetrate the insulating substrate. The bottom line and the wiring layer of the external circuit board are connected via an adhesive such as solder.

[0006]

However, when the above-mentioned high frequency package is used in the millimeter wave band, when a signal transmission line such as a strip line is pulled out of the cavity after passing through the frame, the frame passing portion is required. As the signal line is converted from a microstrip line to a strip line, it is necessary to reduce the width of the signal line in order to achieve impedance matching. As a result, there is a problem that reflection loss and radiation loss occur in the passing portion, and transmission characteristics of a high-frequency signal deteriorate. Further, since the signal transmission line is bent at the corner of the dielectric substrate, reflection at the bent portion is increased, and signal transmission loss occurs.

When a through-hole conductor formed in a dielectric substrate is used as a signal transmission line, a contact portion between the signal transmission line formed on the bottom surface of the substrate and the through-hole conductor is bent, and the reflection at the bent portion is caused. Becomes larger and 40G
Abrupt transmission loss occurs at Hz or higher, making it difficult to use in a high frequency range.

In order to solve such a problem of the conventional high-frequency package, the present inventors have first formed a high-frequency transmission line to which a high-frequency element is connected in a cavity and a bottom surface of a dielectric substrate. It has been proposed that a low-loss signal can be transmitted by electromagnetically coupling a high-frequency transmission line with a slot hole formed in a ground layer (Japanese Patent Laid-Open No. Hei 9-186268).

However, when this high-frequency package is mounted on a wiring layer formed on the surface of an external circuit board on which various electric circuits are formed, electromagnetic coupling in the package is caused by the electric circuit formed on the external circuit board. It has been found that the transmission performance is deteriorated and may affect the signal transmission characteristics.

[0010]

The present inventors have repeatedly studied a configuration for surface-mounting the high-frequency package on an external circuit board without transmission loss of a high-frequency signal. Since the parallel plane mode and the propagation mode of the strip line are generated by the provided ground layer, the electromagnetic coupling by the slot hole between the high frequency transmission line formed on the bottom surface of the package and the high frequency transmission line formed in the cavity is reduced. In addition, in the mounting portion of the package, it is found that by not forming a ground layer at least immediately below the slot hole forming portion, it is possible to suppress the influence on the electromagnetic coupling portion in the external circuit board. Reached.

That is, the mounting structure of the high-frequency package according to the present invention comprises a dielectric substrate, a high-frequency device mounted on the surface of the dielectric substrate, and a surface bonded to the dielectric substrate to seal the high-frequency device. A first signal transmission line formed on the surface of the dielectric substrate, one end of which is electrically connected to the high-frequency element; and a second signal transmission line formed on the bottom surface of the dielectric substrate. A first ground provided in the dielectric substrate and provided with a slot hole at a portion where the other end of the first signal transmission line and one end of the second signal transmission line face each other; A high-frequency package comprising a first layer and a second layer, wherein the first signal transmission line and the second signal transmission line are electromagnetically coupled through the slot hole.
A third signal transmission line is formed on at least a surface of the package, and the third signal transmission line is mounted on a surface of an external circuit board having a second ground layer provided therein. In a mounting structure of a high-frequency package in which a third signal transmission line of a circuit board is electrically connected, at least a position of the second ground layer of the external circuit board immediately below the slot hole forming portion in the package. Where a ground layer non-formation area is provided at a location where the ground layer is not formed.

It is preferable that a plurality of through-hole conductors are formed in the second ground layer around the area where the ground layer is not formed.

[0013]

According to the present invention, a first signal transmission line electrically connected to a high-frequency element inside a cavity formed by a dielectric substrate and a lid, and a first signal transmission line formed on a bottom surface of the dielectric substrate. 2 and the signal transmission line are formed at positions opposing each other via a slot hole of the ground layer formed in the dielectric substrate and are electromagnetically coupled, so that the transmission line passes through the side wall of the lid, Since the line is not bent, there is no reflection loss or radiation loss, and there is no transmission loss due to through holes or via holes, so that high-frequency signals can be transmitted while reducing transmission loss.

Further, by providing a ground layer non-forming area in a ground layer provided on the external circuit board immediately below the slot hole forming portion of the high-frequency package, the magnetic field may be distorted by the ground layer. As a result, as a result, the effect on the electromagnetic coupling portion in the package is suppressed, and deterioration of the transmission characteristics can be suppressed. Therefore, the electromagnetic field distribution of the electromagnetic coupling portion does not change drastically as compared with a state where the electromagnetic field is not mounted on the external circuit board, and a high-sensitivity high-frequency signal with small transmission loss can be transmitted.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The mounting structure of a high-frequency package according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a mounting structure in which a high-frequency package according to an embodiment of the present invention is surface-mounted on an external circuit board. According to FIG. 1, a high-frequency package 1 has a cavity 4 formed by a dielectric substrate 2 made of a dielectric material and a lid 3, and the surface of the dielectric substrate 2 in the cavity 4 is made of MMIC, MIC, or the like. The high frequency element 5 is mounted.

The cover 3 is preferably made of a material having an electromagnetic wave shielding property capable of preventing electromagnetic waves from the cavity 4 from leaking to the outside, or a material in which an electromagnetic wave shielding material is applied to a lid base, and is preferably made of metal, ceramics, or the like. , Ceramic-metal composite materials, glass ceramics, glass organic resin-based composite materials, and the like.

According to the present invention, the first signal transmission line 7 for inputting / outputting signals to / from the high-frequency element 5 is provided on the surface of the dielectric substrate 2 in the cavity 4 of the high-frequency package 1.
Is formed, and the end of the line 7 is connected to the high-frequency element 5.
Are electrically connected by wire bonding, ribbon, tape, flip chip mounting, or the like.

In the dielectric substrate 2, a first ground layer 6 is formed over substantially the entire surface.
The signal transmission line 7 forms a microstrip line together with the ground layer 6.

Further, a second signal transmission line 8 is provided on the bottom surface of the dielectric substrate 2, and forms a microstrip line together with the ground layer 6.

The ground layer 6 has a slot 9 in which no conductor is formed. The first signal transmission line 7 and the second signal transmission line 8 are connected through the slot 9. By causing the ends of the lines to face each other, they are electromagnetically coupled to each other, so that lossless signal transmission is performed between the first signal transmission line 7 and the second signal transmission line 8.

In this electromagnetic coupling structure, specifically, as shown in FIG. 2, the slot hole 9 may be an elliptical elongated hole in addition to a rectangle having long sides and short sides. ,
The slot shape is specified by the operating frequency, and the length a of the long side of the slot hole 9 is desirably set to a length corresponding to の of the wavelength λ of the transmission signal in order to increase the signal transmission efficiency. It is desirable to set the length b of the short side of 9 to a length corresponding to 1/5 to 1/50 of the wavelength λ of the transmission signal.

Then, the first signal transmission line 7 and the second
The signal transmission line 8 is disposed so as to pass through the center x of the slot hole 9 and protrude from each other by the length y when viewed in a plan view with respect to the slot hole 9 having the above shape. The protrusion length y is desirably a length corresponding to about ４ of the wavelength λ of the transmission signal.

On the other hand, according to the external circuit board 10 for mounting the high-frequency package 1, the third signal transmission line 12 capable of transmitting a high-frequency signal is provided on the surface of the insulating substrate 11.
Are formed. Further, a second ground layer 13 is formed inside the external circuit board 10, and the third signal transmission line 12 is formed together with the second ground layer 13.
A microstrip line is formed.

According to the present invention, the high-frequency package 1 having the above configuration is mounted on the external circuit board 10, and the second signal transmission line 8 formed on the bottom surface of the high-frequency package 1 and the external circuit board 10 The high-frequency package 1 can be mounted on the external circuit board 10 by connecting the third signal transmission line 12 formed thereon via the solder bumps 14 and the like.

More specifically, when the microstrip lines are connected to each other by the second signal transmission line 8 made of a microstrip line and the third signal transmission line 12 made of a microstrip line, an electromagnetic field Since the distribution is reversed before and after the connection, signal transmission loss increases, and it is difficult to obtain good characteristics. Therefore, as shown in the wiring pattern diagram on the bottom surface of the package 1 in FIG. 3, the end of the second signal transmission line 8 is formed by a grounded coplanar line having a pair of ground layers 8 ′ formed on both sides of the line 8. Also, as shown in the wiring pattern diagram on the surface of the external circuit board 10 in FIG. 4, the terminal end of the third signal transmission line 12 in the external circuit board 10 is also on both sides of the line 12 similarly to the second signal transmission line. And a grounded coplanar line formed with a pair of ground layers 12 ′,
By connecting the lines 8 and 12, the ground layer 8 'and the ground layer 12' to each other by soldering or the like, it is possible to transmit a signal with reduced transmission loss. The ground layer 8 ′ is connected to the ground layer 6 in the dielectric substrate 2 of the package 1 by a via-hole conductor or a castellation (not shown) formed on the side surface of the dielectric substrate 2 to maintain the same potential. It is desirable to be done.

According to the present invention, the second ground layer 13 formed in the external circuit board 10 is located at least immediately below the slot hole 9 formed in the first ground layer of the high-frequency package 1. The non-ground layer forming region 15 is formed in the region where the ground layer is formed. As shown in the pattern diagram of the second ground layer 13 in FIG. 5, the non-ground layer forming region 15 may be elliptical, polygonal, or the like in addition to the circular shape.

The non-ground layer forming area 15 is
As shown in FIG. 5, desirably, not only the slot hole 9 in the electromagnetic coupling structure shown in FIG. 2 but also the first signal transmission line 7 and the second signal transmission line 8 in plan view.
Is formed so as to include a portion directly below the protruding portion from the center x of the slot hole 9 of FIG. For example, if the signal frequency is 60 GHz
In the case of, the ground layer non-forming region 15 is approximately
m and 3.0 mm or more in width.

In the external circuit board 10, the third
Other wiring layers 16 such as a power supply layer for supplying power to the high-frequency element 5 may be formed in addition to the signal transmission line 12 and the second ground layer 13 according to the present invention. Immediately below one slot hole 9,
From the front surface to the back surface of the external circuit board 10, it is desirable that not only the second ground layer 13 but also those wiring layers do not exist at all. This is because wiring layers other than the ground layer may affect the electromagnetic coupling in the package 1.

In particular, according to the present invention, in order to minimize the influence on the electromagnetic coupling, as shown in the sectional view of FIG. 6A and the pattern diagram of the second ground layer 13 of FIG. In addition, it is desirable to form a plurality of through-hole conductors 17 in the second ground layer 13 around the non-ground layer forming region 15 and to electromagnetically isolate the power supply layer 16 and the like. The plurality of through-hole conductors 17 are set at an interval z at which a signal can be cut off. By forming the through-hole conductor 17, mutual interference between the electromagnetic coupling portion of the package 1 and various wiring layers of the external circuit board 10 can be prevented.

The through-hole conductor 17 is formed, for example, on the surface, bottom, or inside of the external circuit board 10 by a conductor layer 18.
It is desirable that the conductive layer 18 and the second ground layer 13 be electrically connected.

The dielectric substrate 2 of the package 1
The insulating substrate 11 of the external circuit board 10 is made of alumina (Al ₂ O ₃ ), mullite, glass, glass ceramics, aluminum nitride (AlN), silicon nitride (Si ₃ N).
₄ ), etc., and a composite material such as an organic resin, an organic resin-glass fiber, an organic resin-inorganic filler, quartz, or the like.

The signal transmission line in the package 1, the conductor layer such as the ground layer, the signal transmission line in the external circuit board 10, the ground layer, etc. are made of Ag, Cu, Au or the like in order to reduce the transmission loss of the high frequency signal. It is desirable to use a low resistance conductor. Further, when the insulating substrate is made of ceramics, it is possible to co-fire with the low-resistance metal by selecting a low-temperature sinterable ceramic such as a glass ceramic having a firing temperature of about 800 to 1000 ° C.

[0033]

EXAMPLE 1 In the high-frequency package of FIG. 1, tungsten was applied to a 400 μm-thick dielectric substrate made of alumina having a dielectric constant of 8.9 and a dielectric loss of 29.0 × 10 ^-4 (measuring frequency 60 GHz). The first and second signal transmission lines described above, the first ground layer at a depth of 200 μm from the surface of the dielectric substrate, and the power supply layer to the high-frequency element were also formed by simultaneous firing. And the first and second surfaces
The surface of the signal transmission line was further plated with gold to produce a high-frequency package.

The long side a of the slot hole in the electromagnetic coupling portion was 0.85 mm, the short side b was 0.2 mm, and the protrusion length y was 0.3 mm.

On the other hand, the dielectric constant is 2.3 and the dielectric loss is 9.0 × 1.
A third signal transmission line made of copper, a second ground layer, and a power supply layer were formed on an external circuit board using a glass cloth-Teflon resin composite material of 0 ^-4 (measuring frequency 10 GHz) as an insulating substrate. The second ground layer is 1
It was formed at a depth of 30 μm. Further, the second ground layer was provided with a square ground layer non-formation area having a length of 3.0 mm and a width of 3.0 mm centered immediately below the slot hole forming portion of the high frequency package. The power supply layer was formed outside the region where the ground layer was not formed when the external circuit board was viewed in plan.

Then, paste-like eutectic solder was applied by screen printing to the ground layer of the coplanar line with ground formed at the end of the second signal transmission line of the high-frequency package. Thereafter, the high-frequency package is placed on the external circuit board such that the grounded coplanar line at the end of the third signal transmission line of the external circuit board contacts the grounded coplanar line on the high-frequency package side, A heat treatment was performed at a temperature of about 190 ° C. to melt the solder, and the high-frequency package was surface-mounted on an external circuit board.

The transmission characteristics between the high-frequency package and the external circuit board were measured with a network analyzer for the obtained package, and the S21 characteristics are shown in FIG. In addition,
The measurement was performed between the high-frequency element mounting portion of the high-frequency package and the third signal transmission line on the external circuit board. For measurement, the first signal transmission line was converted from a microstrip line to a grounded coplanar line at the high-frequency element mounting portion. As a result of the measurement, the frequency was 58 GHz to 62 GHz.
In z, S11 is -10 dB or less, S21 is -1.2 dB
The above good transmission characteristics were shown.

Embodiment 2 In the high-frequency package of FIG. 1, tungsten was used as a conductor on a 400 μm-thick dielectric substrate made of alumina having a dielectric constant of 8.9 and a dielectric loss of 29.0 × 10 ⁻⁴ (measuring frequency 60 GHz). The first and second signal transmission lines to be formed, a first ground layer at a depth of 200 μm from the surface of the dielectric substrate, and a power supply layer to the high-frequency element were also formed by simultaneous firing. And the first and second surfaces
The surface of the signal transmission line was further plated with gold to produce a high-frequency package.

The long side b of the slot hole in the electromagnetic coupling portion was 0.85 mm, the short side a was 0.2 mm, and the protrusion length y was 0.3 mm.

On the other hand, as an external circuit board, a dielectric constant of 5.
0, dielectric loss 8.0 × 10 ^-4 (measuring frequency 60 GHz)
A third signal transmission line, a second ground layer, and a power supply layer were formed using copper as a conductive material on an insulating substrate made of the above glass ceramic. The second ground layer has a vertical length of 3.0 centered directly below the slot hole forming portion of the high frequency package.
A square ground non-formation area of 3.0 mm in width and 3.0 mm in width was provided. Further, via holes having a diameter of 0.2 mm were arranged in the second ground layer at 0.5 mm intervals so as to surround this region. The power supply layer was formed outside the region where the ground layer was not formed when the external circuit board was viewed in plan.

Thereafter, the high-frequency package was mounted on the surface of an external circuit board in the same manner as in Example 1.

For the obtained structure, the transmission characteristics from the high-frequency element mounting portion of the high-frequency package to the third signal transmission line on the external circuit board were measured with a network analyzer, as in the first embodiment. , S21 characteristics are shown in FIG. As a result of the measurement, S11 exhibited good transmission characteristics of -10 dB or less and S21 exhibited -1.5 dB or more at a frequency of 45 GHz to 65 GHz.

Comparative Example A high-frequency package was mounted on an external circuit board in the same manner as in Example 1 except that no ground layer-free area was provided in the second ground layer on the external circuit board.

For the obtained structure, the transmission characteristics from the high-frequency element mounting portion of the high-frequency package to the wiring layer on the external circuit board were measured by a network analyzer, as in Example 1, and the S21 characteristics were shown in FIG. Indicated. As a result of the measurement, when the area where the ground layer is not formed is not provided on the external circuit board, the frequency S1 is not less than 45 GHz to 65 GHz.
It was found that the sensitivity was deteriorated from 1:10 dB or more to S21: -2 dB or less, and the transmission characteristics deteriorated.

[0045]

As described above in detail, according to the present invention, a signal transmission line is formed on the high-frequency element mounting surface side and the bottom surface of the dielectric substrate.
In a structure in which a high-frequency package for electromagnetically coupling them is mounted on a wiring layer of an external circuit board, a non-conductive layer region where no conductive layer exists in a region near the electromagnetic coupling region of the high-frequency package is formed in the external circuit board. Thereby, transmission loss at the time of mounting can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mounting structure in which a high-frequency package according to an embodiment of the present invention is surface-mounted on an external circuit board.

FIG. 2 is a schematic diagram illustrating an electromagnetic coupling structure between a first signal transmission line and a second signal transmission line of the high-frequency package according to the present invention.

FIG. 3 is a wiring pattern diagram on the bottom surface of the high-frequency package according to the present invention.

FIG. 4 is a wiring pattern diagram of a surface of an external circuit board according to the present invention.

FIG. 5 is a wiring pattern diagram of a second ground layer in the external circuit board.

FIG. 6A is a schematic sectional view of an external circuit board according to another embodiment, and FIG. 6B is a wiring pattern diagram of a second ground layer.

FIG. 7 is a diagram showing a transmission characteristic (S21) result in a mounting structure of the high-frequency package according to the present invention on an external circuit board.

FIG. 8 is a diagram showing a result of transmission characteristics (S21) when a high-frequency package is surface-mounted on another external circuit board of the present invention.

FIG. 9 is a diagram illustrating a transmission characteristic (S21) result when the high-frequency package is surface-mounted on an external circuit board (comparative example) in which a ground layer is arranged on the entire surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High frequency package 2 Dielectric substrate 3 Lid 4 Cavity 5 High frequency element 6 First ground layer 7 First signal transmission line 8 Second signal transmission line 9 Slot hole 10 External circuit board 11 Insulating substrate 12 Third Signal transmission line 13 Second ground layer 14 Solder bump 15 Non-ground layer forming area 16 Power supply layer (other wiring layer) 17 Through-hole conductor 18 Conductor layer

Claims (2)

(57) [Claims] 1. A dielectric substrate, a high-frequency element mounted on the surface of the dielectric substrate, a lid joined to a surface of the dielectric substrate to seal the high-frequency element, and a surface of the dielectric substrate A first signal transmission line, one end of which is electrically connected to the high-frequency element, a second signal transmission line formed on a bottom surface of the dielectric substrate, and a first signal transmission line provided inside the dielectric substrate. A first ground layer having a slot hole formed at a portion where the other end of the first signal transmission line and one end of the second signal transmission line face each other. A third signal transmission line is formed on at least a surface of a high-frequency package formed by electromagnetically coupling the transmission line and the second signal transmission line through the slot hole;
And mounted on a surface of an external circuit board having a second ground layer provided therein, and connecting the second signal transmission line of the package and the third signal transmission line of the external circuit board. A mounting structure for a high-frequency package, comprising: a non-ground layer forming region provided at least in a position of the second ground layer immediately below the slot hole forming portion. . 2. A method according to claim 1, wherein said second layer is formed around said non-ground layer forming area.
2. The mounting structure for a high-frequency package according to claim 1, wherein a plurality of through-hole conductors are provided on the ground layer.