JP3261094B2 - Mounting structure of high frequency wiring board - Google Patents

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 wiring board, and more particularly, to a high-frequency wiring board containing or mounting a high-frequency semiconductor element in a microwave band to a millimeter band. And a mounting structure for connecting to an external circuit board by reducing transmission loss.

[0002]

2. Description of the Related Art Conventionally, a wiring board for handling microwave or millimeter wave signals includes a high-frequency semiconductor package and the like. For example, a cavity formed by a dielectric substrate made of a dielectric, a frame and a lid is used. A structure in which a semiconductor element is housed in a cavity and hermetically sealed is proposed.

[0003] Input and output of high-frequency signals to and from a semiconductor element in a high-frequency semiconductor package having such a structure,
The package is mounted on an external circuit board by forming a signal transmission line, such as a strip line, formed on the surface of the dielectric substrate and electrically connected to the high-frequency semiconductor element, from the inside of the cavity to the outside through the frame, This is further routed to the back surface via the side surface of the dielectric substrate and connected to the connection high-frequency terminal, and the connection terminal and the wiring layer of the external circuit board are connected via an adhesive such as solder.

In addition, a high-frequency terminal for connection is formed on the back surface of the dielectric substrate of the high-frequency semiconductor package, and the high-frequency terminal and the semiconductor element are connected through a through-hole conductor formed through the dielectric substrate. There has been proposed a high-frequency semiconductor package which is connected by a connection. In this semiconductor package for high frequency, similarly to the above, the high frequency terminal and the wiring layer of the external circuit board are connected via an adhesive such as solder.

[0005]

However, when the former high-frequency semiconductor package is used in the millimeter-wave band, when a signal transmission line such as a strip line is pulled out from the inside of the space through the frame to the outside, the frame is closed. Since the signal line is converted from the microstrip line to the strip line in the passing portion, it is necessary to match impedance between the lines and to reduce the width of the signal line. As a result, there is a problem that reflection loss and radiation loss are apt to occur in the passing portion, and the transmission characteristic of the high-frequency signal is likely to deteriorate. In addition, since the signal transmission line is bent at the side surface of the dielectric substrate, reflection at the bent portion is increased, resulting in deterioration of transmission characteristics.

In the latter package, when the through-hole conductor is led out to the back surface of the dielectric substrate and used as a signal line, the contact portion between the signal transmission line and the through-hole is bent, and the reflection at this bent portion is caused. The loss increases,
At 40 GHz or more, rapid deterioration of characteristics occurs, so that it has been difficult to use in a high frequency range.

Therefore, the present inventors have proposed, as a high-frequency semiconductor package, a package that incorporates an electromagnetic coupling mechanism and can transmit a signal line with low loss.
(JP-A-09-186268). However, when this high-frequency wiring board is mounted on the wiring layer of an external circuit board, if the dielectric constant of the external circuit board becomes 7 or more, the transmission characteristics deteriorate, making it difficult to use in a high-frequency region. The grade was limited.

Accordingly, the present invention is capable of mounting a high-frequency wiring board on an external circuit board by surface mounting on the external circuit board, reducing the deterioration of the transmission characteristics of high-frequency signals, and applying the present invention to any external circuit board. It is intended to provide a structure that can be mounted.

[0009]

Means for Solving the Problems The present inventors have made it possible to mount a high-frequency wiring board on an external circuit board without deteriorating the characteristics of a high-frequency signal. As a result of repeated studies on a configuration that can ensure sufficient mounting strength, signal transmission lines were formed on the semiconductor element mounting surface side and the back surface of the dielectric substrate, respectively, and a high-frequency wiring board formed by coupling them was connected to an external circuit. When mounted on the wiring layer of the board, by providing a material with a low dielectric constant on the surface of the external circuit board immediately below the joint of the high-frequency wiring board, the signal transmission on the wiring board can be performed for any external circuit board. It has been found that good coupling between lines can be maintained.

That is, the mounting structure of the high-frequency wiring board according to the present invention includes a dielectric substrate, a high-frequency semiconductor element mounted on the surface of the dielectric substrate, and the dielectric substrate formed on the surface of the dielectric substrate. A first signal transmission line electrically connected to the semiconductor element on the front surface of the body substrate, a second signal transmission line formed on the back surface of the dielectric substrate, the first signal transmission line and the second signal transmission line; A high-frequency wiring board formed by coupling the second signal transmission line to a wiring layer formed on the surface of the insulating substrate in the external circuit board via a connection portion formed at the end of the second signal transmission line. A recess in the surface of the external circuit board immediately below a joint between the first signal transmission line and the second signal transmission line, and the high frequency The dielectric substrate and the outside of the wiring substrate Than the insulating substrate in the circuit board is characterized in that embedded in the low dielectric constant material.

The first signal transmission line and the second signal transmission line
Is coupled electromagnetically via a slot hole of a ground layer provided inside the dielectric substrate, or a through-hole conductor formed so as to penetrate the dielectric substrate. May be any of those connected by

According to the mounting structure of the present invention, the first signal transmission line formed on the surface of the dielectric substrate of the high-frequency wiring board and electrically connected to the semiconductor element; The second signal transmission line formed on the back surface is made of a dielectric substrate or a material having a dielectric constant lower than that of the external circuit board on the surface of the external circuit board immediately below the coupling portion electromagnetically or by a through-hole conductor. By providing the region, the effective dielectric constant, characteristic impedance of the electromagnetic coupling portion and the microstrip line portion, and the parasitic inductance around the through-hole conductor for connection do not suddenly change, so that there is little deterioration in transmission characteristics and high frequency Signals can be transmitted.

In particular, according to the present invention, a structure in which the first signal transmission line and the second signal transmission line are formed at opposing positions via the dielectric substrate and electromagnetically coupled to each other. According to the method, the transmission line can be coupled without passing through the side wall of the lid in a high-frequency semiconductor package structure or the like. And a signal of a required frequency can be transmitted.

[0014]

FIG. 1 is a cross-sectional view of a mounting structure based on a first embodiment of a high-frequency semiconductor package as a typical application of a high-frequency wiring board according to the present invention. According to FIG. 1, a high-frequency semiconductor package 1 has a cavity 4 formed by a dielectric substrate 2 made of a dielectric material and a lid 3, and a high-frequency semiconductor element 5 such as an IC is formed in the cavity 4. Is installed.

A ground layer 6 made of a conductor layer is formed almost entirely inside the dielectric substrate 2, and a portion of the ground layer 6 is connected to the semiconductor element 5 on the surface of the dielectric substrate 2 in the cavity 4. A first signal transmission line 7 is formed. A second signal transmission line 8 is also formed on the back surface of the high frequency semiconductor package 1.

A slot 9 in which no conductor layer is formed is formed in the ground layer 6, and the first signal transmission line 7 and the second signal transmission line 8 are formed through the slot 9. By forming the lines at positions where the ends of the lines face each other, the lines are electromagnetically coupled, and a signal with little loss is transmitted.

The cover 3 is made of a material that can prevent the electromagnetic wave from the cavity 4 from leaking outside.
It is formed of metal, ceramics, ceramic-metal composite material, glass ceramics, glass organic resin-based composite material, and the like.

On the other hand, a wiring layer 12 made of a coplanar line or a grounded coplanar line is formed on the surface of the external circuit board 10. Further, in order not to adversely affect the signal transmission characteristics between the first signal transmission line and the second signal transmission line in the package 1, the external circuit board should be made of a material having a dielectric constant as low as possible. Although desirable, the external circuit board may be made of a material having a high dielectric constant.

In such a case, according to the present invention, the surface area of the external circuit board 10 located at least immediately below the slot hole 9 formed in the high-frequency semiconductor package 1 is covered by the dielectric substrate 2 and the external circuit of the package 1. It is formed of a material having a lower dielectric constant than the substrate 10.

Specifically, a concave portion is formed in a region immediately below the slot hole 9 in the external circuit board 10, and a dielectric material 2 having a lower dielectric constant than the dielectric substrate 2 and the external circuit substrate 10 is formed in the concave portion. Embedded. This low dielectric constant material 11 is desirably a material having a low dielectric loss of 3 or less, particularly 2.7 or less. As such a low dielectric constant material, a fluorine-based resin such as PTFE (polytetrafluoroethylene) or a resin-based material such as PPE (polyphenylene ether) resin, particularly a fluorine-based resin is suitably used. In addition, a low dielectric constant material powder such as quartz may be filled, and the opening of the concave portion filled with the low dielectric constant material may be covered with a lid material made of a low dielectric constant material.

Further, the high-frequency semiconductor package 1 is mounted on an external circuit board 10, and a second signal transmission line 8 formed on the back surface of the high-frequency semiconductor package 1 and a wiring layer formed on the external circuit board 10. Reference numerals 12 are connected to each other via bumps 13 made of solder, gold, or the like.

FIG. 2 is a view for explaining wiring in the cavity 4 of the high-frequency semiconductor package 1 of FIG.
In the cavity 4, a power supply layer 14a for supplying power to the semiconductor element 5 is formed in addition to the semiconductor element 5 and the microstrip line forming the first signal transmission line 7, and one end of the power supply layer 14a. Is electrically connected to the semiconductor element 5 by a ribbon, a wire, a TAB, or the like, and the other end is electrically connected to the wiring layer 14c on the back surface of the dielectric substrate 2 via the through-hole conductor 14b. ing.

The first signal transmission line 7 composed of a microstrip line and the semiconductor element 5 are the same as those of the first element.
Can be connected with a small transmission loss by directly mounting on the signal transmission line 7, the method of connecting the first signal transmission line 7 and the semiconductor element 5 is not limited to this. Alternatively, the connection can be made by using a gold ribbon or a plurality of wire bonding, or by using a conductor plate in which a conductor such as Cu is formed on a substrate such as polyimide.

The other end of the first high-frequency transmission line communicates with the second signal transmission line 8 via a slot 9 formed in a ground layer 6 formed inside the dielectric substrate 2 of the high-frequency semiconductor package 1. Are combined. Specifically, the end of each of the first signal transmission line 7 and the second signal transmission line 8 is separated from the center of the slot hole 9 through the slot hole 9 formed in the ground layer 6. It is desirable to be formed at a position protruding on average with a length L corresponding to １ ／ of the wavelength λ of the transmission signal.

The shape of the slot hole 9 is a rectangular or elliptical elongated hole having a long side and a short side, and the shape can specify a used frequency and a frequency bandwidth. Therefore, the long side of the slot hole 9 is the wavelength λ of the transmission signal.
Of the slot hole 9
Is shorter than 1/5 of the wavelength λ of the transmission signal.
It is desirable to set it to a length equivalent to 50.

FIG. 3 is a diagram for explaining wiring formed on the back surface of the high-frequency semiconductor package 1 of FIG. The second signal transmission line 8 is, like the first signal transmission line 7,
The microstrip line is formed into a coplanar line with a ground having a ground layer 15 on both sides of a center conductor of the microstrip line at a terminal portion (connection portion with an external circuit board).
The ground layer 15 is connected to the ground layer 6 formed inside the dielectric substrate 2 by via hole conductors 16 or castellations (not shown) formed on the side surfaces of the dielectric substrate 2.

FIG. 4 shows the wiring layer 1 on the surface of the external circuit board 10.
FIG. 2 is a plan view for explaining No. 2;
Central conductor 17 and ground layers 18 provided on both sides thereof
And, in some cases, a coplanar line with a ground by forming a ground layer in the external circuit board 10.

Then, the coplanar line with ground formed at the end of the second signal transmission line on the back surface of the package shown in FIG. 3 and the coplanar line or the coplanar line with ground shown in FIG. The package 1 can be mounted on the external circuit board 10 by connecting the center conductors 8 and 17 and the ground layers 15 and 18 in the wiring layer 12. Note that the package 1 is mounted in a region within a dotted line of the external circuit board in FIG. The power supply wiring layer 14c is electrically connected to the power supply wiring layer 12 'formed on the surface of the external circuit board 10 by soldering or the like.

FIG. 5 is a cross-sectional view of a mounting structure according to a second embodiment of a high-frequency semiconductor package as a typical application example of the high-frequency wiring board of the present invention. In the high-frequency semiconductor package 19 shown in FIG. 5, a cavity 4 is formed by a dielectric substrate 2 and a lid 3 made of a dielectric material, as in FIG. 5 is mounted. In the dielectric substrate 2, a ground layer 6 is formed over substantially the entire surface, and a cavity 4 is formed.
The first signal transmission line 7 is formed on the surface of the dielectric substrate 2 inside, and the second signal transmission line 8 is formed on the back surface of the dielectric substrate 2. The first signal transmission line 7 and the second
Each of the signal transmission lines 8 forms a microstrip line together with the ground layer 6 provided inside the dielectric substrate 2.

Then, the first signal transmission line 7 and the second signal transmission line 8 are connected to each other by a through-hole conductor 20 provided so as to penetrate through the dielectric substrate 2 at their terminal portions. . When the ground layer 6 is formed in the dielectric substrate 2, the through-hole conductor 20 is provided at a position penetrating the hole 21 provided in the ground layer 6 so as not to contact the ground layer 6. I have.

FIG. 6 is a diagram for explaining wiring on the surface of the dielectric substrate 2 in the cavity 4 of the high-frequency semiconductor package 19 of FIG. The first signal transmission line 7 is connected to a second signal transmission line 8 formed on the back surface of the dielectric substrate 2 via a through-hole conductor 20 formed on the dielectric substrate 2. Around the through-hole conductor 20, an impedance matching through-hole conductor 22 is formed. It is preferable that one or more through-hole conductors 22 are formed around the through-hole conductor 20 for coupling.

FIG. 7 is a diagram for explaining wiring on the dielectric back surface of the high-frequency semiconductor package 19 of FIG. According to FIG. 7, the second signal transmission line 8 has a ground layer 15 on both sides of the center conductor of the microstrip line at its terminal end (connection part to the external circuit board), as in FIG.
It has been converted to a coplanar line with ground. The ground layer 15 is connected to the ground layer 6 formed inside the dielectric substrate 2 by a via-hole conductor 16. The connection between the ground layer 15 and the ground layer 6 can be made by castellation formed on the side surface of the dielectric substrate 2 in addition to the via hole conductor 16.

On the other hand, the external circuit board 10 has the through-hole conductors 20 formed in the package 19 as in FIG.
A concave portion is formed in a region located immediately below
A low-permittivity material 11 having a lower permittivity than the dielectric substrate 2 and the external circuit board 10 is embedded in the recess. The low dielectric constant material 11 is desirably a low dielectric loss material, and is desirably formed of a resin-based material.

In the high-frequency semiconductor package shown in FIGS. 1 to 7 as a typical application example of the high-frequency wiring board of the present invention, the semiconductor element 5 is formed by the dielectric substrate 2 and the lid 3. Although it is hermetically sealed in the cavity 4 to be formed, the package structure in the present invention is not limited to this. For example, as shown in FIG. The semiconductor element 5 may be resin-sealed on the surface of the body substrate 2 with a resin 22 such as an epoxy resin.

In the above embodiment, the dielectric substrate 2 and the external circuit board 10 of the semiconductor package 1 for high frequency are used.
Are ceramics such as alumina (Al ₂ O ₃ ), glass ceramics, aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), organic resin, or organic insulating material composed of a composite material of an organic resin and an inorganic filler. Alternatively, it is formed of quartz or the like, but in order to reduce the transmission loss of the high-frequency signal, A
It is desirable to use a low-resistance conductor such as g, Cu, Au or the like.
Glass ceramics of about ~ 1000 ° C is most suitable,
With this combination, simultaneous firing of the dielectric substrate and the first and second signal transmission lines 7 and 8 and the ground layers 6 and 15 is also possible.

The dielectric constant is 8.9 and the dielectric loss is 1.5 × 1.
FIG. 1 shows a dielectric substrate made of alumina ceramic of 0 ^-3 (measurement frequency 8.6 GHz) made of tungsten and gold.
A high-frequency semiconductor package having the mounting structure described above was manufactured. According to the present invention, this high-frequency semiconductor package is 4 cm long, 4 cm wide and 4 cm wide in a region including immediately below the slot hole 9 of a dielectric substrate made of alumina ceramics having a dielectric constant of 9.8 (measuring frequency 8.6 GHz). After forming a 0.8 mm concave portion and mounting it on an external circuit board in which polytetrafluoroethylene (PTFE) resin having a dielectric constant of 2.3 is sealed in the concave portion, transmission characteristics between the external circuit board and the inside of the high-frequency package Was measured by a network analyzer. At a measurement frequency of 20 GHz, S11 is -13.5d.
B and S21 were -1.3 dB.

On the other hand, when all of the external circuit board 10 is formed of a dielectric substrate made of alumina ceramics having a dielectric constant of 9.8 (measuring frequency 8.6 GHz), the package is similarly mounted, and then the high-frequency package is mounted. When the transmission characteristics between the external circuit boards were similarly measured from inside using a network analyzer, the measurement frequency was 20 GHz.
In S11, S11 is -3.5 dB, and S21 is -4.8 dB, which indicates that the transmission characteristics are degraded.

[0038]

As described above in detail, according to the present invention, a signal transmission line is formed on a semiconductor element mounting surface side and a back surface of a dielectric substrate.
In a structure in which the high-frequency wiring board obtained by connecting them is mounted on the wiring layer of the external circuit board, the dielectric constant of the high-frequency wiring board is lower than the dielectric board and the external circuit board on the surface of the external circuit board adjacent to the coupling region. By providing the region formed of the above material, it is possible to reduce transmission loss during mounting on any external circuit board.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining wiring in a cavity of the high-frequency semiconductor package in FIG. 1;

FIG. 3 is a diagram for explaining wiring formed on the back surface of the high-frequency semiconductor package in FIG. 1;

FIG. 4 is a diagram for explaining wiring on the surface of the external circuit board in FIG. 1;

FIG. 5 is a schematic sectional view for explaining a second embodiment of the mounting structure of the present invention in which a high-frequency semiconductor package is surface-mounted on an external circuit board.

6 is a diagram for explaining wiring in a cavity of the high-frequency semiconductor package in FIG. 5;

FIG. 7 is a diagram for explaining wiring formed on the back surface of the high-frequency semiconductor package in FIG. 5;

FIG. 8 is a schematic cross-sectional view for explaining a third embodiment of the mounting structure of the present invention in which a high-frequency semiconductor package is surface-mounted on an external circuit board.

[Explanation of symbols]

 1, 19, 21 High-frequency semiconductor package 2 Dielectric substrate 3 Lid 4 Cavity 5 Semiconductor element 6 Ground layer 7 First signal transmission line 8 Second signal transmission line 9 Slot hole 10 External circuit board 11 Low dielectric constant material Reference Signs List 12 wiring layer 12 'power supply wiring layer 13 bump 14a power supply layer 14b, through-hole conductor 14c power supply wiring layer 15 ground layer 16 via-hole conductor 17 center conductor 18 ground layer 20 through-hole conductor 21 void 22 through-hole impedance matching impedance 23 resin

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 1/18 H01L 21/60 311 H01L 23/12

Claims (3)

(57) [Claims] 1. A dielectric substrate, a high-frequency semiconductor device mounted on a surface of the dielectric substrate, and a semiconductor device attached to the surface of the dielectric substrate and electrically connected to the semiconductor device on the surface of the dielectric substrate. A first signal transmission line, a second signal transmission line formed on the back surface of the dielectric substrate, and a high-frequency signal formed by coupling the first signal transmission line and the second signal transmission line. A mounting structure in which a wiring board is mounted on a wiring layer formed on a surface of an insulating substrate of an external circuit board via a connection portion formed at a terminating end of the second signal transmission line; A concave portion is formed in a region immediately below a coupling portion between the first signal transmission line and the second signal transmission line on a substrate surface, and the dielectric substrate and the external circuit substrate of the high-frequency wiring board are formed in the concave portion. Lower dielectric constant than the insulating substrate in A mounting structure for a high-frequency wiring board, wherein the material is embedded. 2. The semiconductor device according to claim 1, wherein said first signal transmission line and said second signal transmission line are electromagnetically coupled via a slot in a ground layer provided inside said dielectric substrate. The mounting structure of the high-frequency wiring board described. 3. The signal transmission line according to claim 1, wherein the first signal transmission line and the second signal transmission line are coupled by a through-hole conductor formed to penetrate the dielectric substrate.
The mounting structure of the high-frequency wiring board described.