JP2517209B2 - High-frequency circuit module mounting structure - 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 for a high frequency circuit module which generates heat. In recent years, wireless communication in mobile communication is highly required to have multi-carrier (multiplexing) and high output, and high-frequency power amplifiers use high-output and low-power semiconductor circuit elements that can obtain low distortion over the entire band. Distorted ones are required.

In a high frequency power amplifier using a semiconductor circuit element, conduction and removal of heat generated by the semiconductor circuit element due to higher output of the semiconductor circuit element is a factor affecting performance assurance and reliability and life of the element. Become.

In view of the above, when the present invention constructs a high-power high-frequency circuit with a planar circuit, the thermal resistance of contact between the high-frequency circuit module containing the semiconductor circuit element and the metal substrate on which it is mounted is high. It satisfies the demand for high-frequency power amplifiers with high performance, high reliability and long life.

In the present invention, the term "metal substrate" includes a simple substrate and a metal housing, which are generically referred to as a metal substrate or a metal substrate.

[0005]

2. Description of the Related Art In a high frequency circuit module as described above, the precision of the surface roughness of the grounding surface and the heat transfer surface which are in contact with the metal substrate to be mounted is extremely high so that a reliable contact state between wide surfaces can be obtained. I have to.

A mounting structure of such a high-frequency circuit module and a metal substrate will be described with reference to a perspective view of an essential part in a separated state of FIG. 5 and a sectional view of an essential part of FIG. 6 along a circuit conductor pattern of the circuit board.

FIG. 6A shows the state before attachment, and FIG. 6B shows the state of attachment. Note that the term “metal substrate, etc.” means that the term “metal substrate or the like” is included in any case of being attached to a metal substrate or a metal housing, but hereinafter, it is simply referred to as a metal substrate.

In the figure, a circuit board 5 consisting of a dielectric substrate 4 having a ground conductor layer 2 formed on the lower surface and a circuit conductor pattern 3 formed on the upper surface of a metal substrate 1 is a surface of the ground conductor layer 2. Are electrically and mechanically joined together.

In the portion 7 to which the high-frequency circuit module 6 is attached, the circuit board 5 is separated and a groove-shaped recess 8 is formed in the metal substrate 1, the bottom surface is made flat and smooth, and a screw hole 9 for attachment is formed. It is provided.

The metal substrate 1 is made of copper or a copper alloy having good thermal conductivity. In the case of aluminum, a film of gold or the like is formed on the surface by plating. On the lower side of the high-frequency circuit module 6, flange-shaped mounting seats 11 are projected on both sides, and cutout holes 12 for mounting screws are formed in the mounting seats 11, respectively. A semiconductor circuit element that generates heat is mounted inside the high frequency circuit module 6, and is hermetically sealed by a lid 13. In addition,
The package, which is the housing for the high-frequency circuit module 6, is made of copper or the like having good thermal conductivity.

On both sides different from the mounting seat 11, thin plate-like terminals 14 joined to a high-frequency transmission line which constitutes an airtight terminal with a dielectric are provided so as to project and are connected to an internal circuit. .

With the above structure, the high frequency circuit module 6 is placed in the recess 8 of the metal substrate 1, and the four screws 15 from the top are placed.
Is screwed into the screw hole 9 through the notch hole 12, the high frequency circuit module 6 is positioned so that the positions of the circuit conductor pattern 3 and the terminal 14 are at predetermined predetermined positions, and then tightened and fixed.

As described above, the high frequency circuit module 6
Is attached to the metal substrate 1, the terminals 14 are soldered to the circuit pattern 3 as shown in FIG.
And connect.

In contrast to the above construction, as shown in FIG. 7, the lower end surface of the high frequency circuit module 6 and the metal substrate 1 are
Deforms relatively easily between the concave part 8 and the concave part 8,
A method is also known in which a soft metal, such as an indium sheet 18, which is easily adapted to both surfaces and has a good thermal conductivity is interposed. In this case, the depth of the recess 8 is appropriately deepened.

[0015]

In the mounting structure as shown in FIGS. 5 and 6, when the tightening balance of the screws 15 on the metal substrate 1 is not uniform, or when the contact surface is slightly distorted,
There is a problem that a certain surface contact state cannot be obtained due to the presence of foreign matter between contact surfaces or a minute swelling due to a scratch, etc., and thermal resistance of contact is generated.

Although the mounting structure as shown in FIG. 7 solves the problem of the unstable surface contact state as described above, the soft metal 18 is largely deformed by the pressing force due to the tightening of the high frequency circuit module 6. When it occurs, for example, the high frequency circuit module 6 is in a state of being sunk below a predetermined set position due to creep, thermal deformation, or the like accompanying the change over time of the soft metal 18.

In such a case, the terminal 14 is not flat as shown in FIG. 7B, and steps A, A are generated. Alternatively, as shown in FIG. 6C, the high frequency circuit module 6 is tilted so that the terminals 14 are not in a horizontal state and are tilted like A, A. Also soft metal 18
Due to the deformation of B, it oozes into the gap formed between the concave portion 8 and the high-frequency circuit module 6 and rises in the gap as indicated by B and B.

In the worst case, if such swelling increases, the terminal 14 may be contacted and damaged, or the terminal 14 may be damaged.
The high-frequency transmission characteristics may change due to a change in the distance between the ground and the ground. As described above, there is a problem that the terminal 14 is deformed or stressed in the soldering 16 portion including the terminal 14.

The present invention solves the above-mentioned problems of the prior art, reduces thermal resistance, and is excellent in long-term stability.
It is intended to provide a mounting structure for a high-frequency circuit module which is electrically high-performance and highly reliable.

[0020]

Means for Solving the Problems The object of the present invention for solving the above-mentioned problems is to provide a mounting surface of a high-frequency circuit module in which a semiconductor circuit element is incorporated and which is screwed and mounted on a metal substrate or the like. A mounting structure in which a soft metal for heat conduction is interposed between the metal substrate and the surface of the metal substrate, the soft metal accommodating recess is formed, and the metal substrate and the high frequency circuit module are mounted in a mounted state of the high frequency circuit module. The high frequency circuit module mounting structure is configured such that a part of the surfaces are in contact with each other to define a mounting position.

Further, the above-mentioned high frequency circuit configured such that the metal substrate and the surfaces of the high frequency circuit module are brought into contact with each other directly below the portion where the input / output section of the high frequency circuit module is connected to the high frequency plane transmission line. It is a mounting structure of a circuit module.

[0022]

In the constituent means of the present invention, a part of the contact surface between the metal substrate and the high frequency circuit module is in contact, and the other part is in contact with the soft metal via the soft metal. Therefore, the excessive tightening force due to the mounting of the high-frequency circuit module is not restricted and prevented from reaching the soft metal, so that stable heat conduction characteristics and electrical characteristics can be maintained for a long period of time.

According to the further means, since the direct contact portion between the high frequency circuit module and the metal substrate or the like is directly under the connection portion between the terminal of the module and the high frequency plane transmission line, a reliable ground connection relation can be obtained. As a result, the high frequency transmission characteristics are in a very good state.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The connection structure of a high frequency circuit module of the present invention will be described in detail below with reference to the drawings in an embodiment based on the structure.

FIG. 1 is a perspective view of an essential part of a first embodiment of the present invention in a separated state, and FIG. 2 is a sectional view of the essential part at a position along the circuit conductor pattern. FIG. 2A shows a state before attachment, and FIG. 2B shows an attached state.

It should be noted that the term “metal substrate, etc.” can be included in any case of being attached to a metal substrate or a metal housing, but hereinafter, it will be simply referred to as “metal substrate”. And

In the figure, a circuit board 5 composed of a dielectric substrate 4 having a ground conductor layer 2 formed on a lower surface and a circuit conductor pattern 3 formed on an upper surface on a metal substrate 21 is electrically connected on the surface of the ground conductor layer 2. Mechanically and mechanically.

In the portion 22 to which the high-frequency circuit module 6 is attached, the circuit board 5 is separated, and the groove-like recess 23 is formed in the metal substrate 21 so that the bottom surface is flat and smooth, and the step portions on both sides are formed. 24 and a second recess 25 that is one step lower than the recess 24 are formed, and a screw hole 26 for attachment is provided in the bottom thereof.

The second recess 25 is provided on the second recess 25 of the portion 22 to which the high frequency circuit module 6 is attached.
A soft metal 28, such as an indium sheet, having a thickness that is appropriately thicker than the depth thereof is arranged.

The metal substrate 21 is made of copper or a copper alloy having a good thermal conductivity. In the case of aluminum, a film of gold or the like is applied to the surface by a plating method or the like. On the lower side of the high-frequency circuit module 6, flange-shaped mounting seats 11 are projected on both sides, and notch holes 12 for mounting screws are formed therein. Inside the high-frequency circuit module 6, a semiconductor circuit element with heat generation (not shown) is mounted and is hermetically sealed with a lid 13. The package, which is the housing for the high frequency circuit module 6, is made of copper or the like having good thermal conductivity.

Further, on both sides different from the mounting seat 11, thin plate-like terminals 14 joined to a high-frequency transmission line which constitutes an airtight terminal with a dielectric are provided so as to project, and are connected to an internal circuit. .

With the above structure, the high frequency circuit module 6 is mounted on the metal substrate 21 at the mounting portion 22 of the high frequency circuit module.
Place it on the top and screw the four screws 15 from the top to the cutout hole 12
The high frequency circuit module 6 is positioned and positioned so that the circuit conductor pattern 3 and the terminal 14 are positioned at predetermined proper positions.

As described above, the high frequency circuit module 6
Is attached to the metal substrate 21, the terminals 14 are soldered to the circuit conductor pattern 3 as shown in FIG.
And connect.

The state of attachment in this way is shown in FIG.
(B) of FIG. The bottom surface 29 of the high-frequency circuit module 6 is in contact with the surfaces of the stepped portions 24, 24 of the metal substrate 21 on both sides, and the other portions are pressed by the soft metal 28 arranged in the second recess 25 to soften the metal. It is in electrical and thermal contact with the metal substrate 21 via 28.

The circuit conductor pattern 3 on the circuit board 5 is a so-called microstrip line, and this and the terminal 14 of the high frequency circuit module 6 mean that the dielectric constant of the dielectric substrate 4 in which the microstrip line constitutes a high frequency plane circuit. While the characteristic impedance is determined by the above, the characteristic on the terminal 14 side is determined by the space shape based on the dielectric constant of air in the space portion of the metal substrate 21.

Therefore, according to this embodiment, the metal substrate 2
There is no soft metal 28 on the step 24 of No. 1,
Smooth finished surface and bottom surface of high frequency circuit module 2
Due to the close contact with 9, stable transmission characteristics can be obtained without a discontinuous state of the electrical transmission path.

Since the soft metal 28 is densely filled in the second recess 25 and is in a pressed state, the heat generated in the high frequency circuit module 6 is effectively transferred to the metal substrate 21 through the soft metal 28. Thus, the temperature rise of the high frequency circuit module 6 is controlled so as not to exceed a certain temperature.

With respect to the soft metal 28, since the high-frequency circuit module 6 is defined at a fixed position by the step portion 24, an excessive pressing force does not act regardless of the tightening state of the mounting screw, and the soft metal 28 can be used for a long period of time. A stable and constant pressure contact state can be obtained over the entire range.

In this embodiment, the second recess 2 is formed on the metal substrate 21 side.
5 is formed, on the contrary, a similar recess 25 is formed on the bottom surface 29 side of the high frequency circuit module 6 to form the metal substrate 2
Even if only the concave portion 23 is provided on the first side and the portions corresponding to the step portions 24 on both sides of the bottom portion of the high frequency circuit module 6 are brought into contact with each other, the same action and effect can be obtained. Of course, it goes without saying that the soft metal 28 is provided in the recess corresponding to the second recess 25.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. Since FIG. 3 comprises a circuit board 5 and a high-frequency circuit module 6 having the same configuration as in the first embodiment, the same reference numerals are given to these and description of the configuration is omitted.

Here, the structure of the metal substrate 31 having a different structure will be described. A groove-shaped recess 33 is formed in a portion 32 to which the high-frequency circuit module 6 is attached, and the bottom surface 3 is formed.
4 is a screw hole 35 (not shown) for mounting similar to that of FIG.
(26 in FIG. 1), and projections 37 having a height corresponding to the thickness of the soft metal 36 disposed here from the bottom surface 34 are provided at a plurality of locations.

As the shape of the projection 37, an appropriate shape in plan view is applied. For example, it is circular or rectangular, but its position is as close to the screw hole 35 as possible or the screw hole 3
It is preferably a portion containing 5.

The thickness of the soft metal 36 is slightly higher than the height of the protrusion 37, and the width thereof is set to be a width slightly smaller than the width of the recess 33, for example, an indium sheet. is there.

The metal substrate 31 is made of copper or a copper alloy having good thermal conductivity. In the case of aluminum, a film of gold or the like is applied to the surface by plating or the like. With the above configuration, the high-frequency circuit module 6 is placed on the mounting portion 32 of the high-frequency circuit module of the metal substrate 31, and the four screws 15 are screwed into the screw holes 35 through the cutout holes 12 as in FIG. The screw 15 is tightened and fixed so that the position of the high-frequency circuit module 6 is positioned so that the conductor pattern 3 and the terminal 14 are located at predetermined proper positions.

After the high frequency circuit module 6 is attached to the metal substrate 31, as shown in FIG. 3B,
The terminal 14 and the circuit conductor pattern 3 are connected by soldering 16.

The bottom surface 29 of the high-frequency circuit module 6 thus mounted is in contact with the projection 37 surface of the recess 33 bottom surface 34 of the metal substrate 31, and the other bottom surface 29 is in contact with the soft metal 35 and is pressed. Has become.

The soft metal 36 is pressed against both surfaces 29,
It spreads to 34 and is in contact with the wall portion of the recess 33, and is in electrical and thermal contact. In this way, the soft metal 36 is set so as not to ooze and fill the gap between the wall surface between the recess 33 and the high-frequency circuit module 6 more than necessary. Therefore, stable transmission characteristics can be obtained without electrical discontinuity.

Since the high-frequency circuit module 6 contacts the surface of the protrusion 37 and is defined at a fixed position, the soft metal 36 is
An excessive pressing force does not act regardless of the tightened state of the mounting screw 15, and a stable and constant pressure contact state can be obtained for a long period of time.

Since the soft metal 36 is filled in the concave portion 33 and is in a pressure contact state, the heat generated in the high frequency circuit module 6 is effectively transferred to the metal substrate 31 via the soft metal 36, and the high frequency circuit module. The temperature rise of 6 is controlled so as not to exceed a certain temperature.

In this embodiment, the protrusion 37 is formed on the metal substrate 31, but the same protrusion 37 is formed on the bottom surface 29 of the high-frequency circuit module 6 so that only the recess 33 is formed on the metal substrate 31 side. Bottom part 2 of high-frequency circuit module 6
Even if the portions corresponding to the protrusions 37 of 9 are brought into contact with each other, the same action and effect can be obtained. Of course, it goes without saying that the soft metal 36 is arranged in the recess 33.

A further configuration and features of the present invention will be described with reference to FIG. FIG. 4 is data obtained by experiments by the inventor of the present invention regarding the relationship between the surface roughness and the thermal resistance of heat transfer according to the present invention. The abscissa indicates the surface roughness, the height of the unevenness, and the ordinate indicates the thermal resistance.

It has been generally recognized that it is desirable for heat transfer by surface contact to be such that the adhesion between the surfaces is good and there is no gap. Therefore, the present inventor also conducts an experiment by making the surfaces of both the high-frequency circuit module and the metal substrate as extremely smooth surfaces with few irregularities, even in the case of interposing a soft metal based on the above idea. I did.

First, in the case where no soft metal is interposed, the contact surface finishing accuracy on the metal substrate side is calculated by the 10-point averaging method.
It was found that about 2 μm was necessary. However, in the case of interposing a soft metal, rather than such a surface state,
It was found that the larger the surface roughness was 12.5 μm, the more the thermal resistance of the contact decreased.

It is considered that the soft metal conforms to the rough surface to increase the heat transfer area and increase the heat transfer efficiency, and the thermal resistance of contact can be reduced.

[0055]

As described in detail above, according to the mounting structure of the high-frequency circuit module of the present invention, the structure is simple and the electric high-frequency characteristics are excellent, and the heat generation of the high-frequency circuit module is effectively transmitted. The practical effect of heat cooling is extremely remarkable. In addition, regarding the state of the surface on which the soft metal is interposed, not the smooth surface state but an appropriately rough surface state reduces the heat resistance of heat transfer and transfers a larger amount of heat even with the same facing area. You can get what you get.

[Brief description of drawings]

FIG. 1 is a mounting structure of a high-frequency circuit module of the present invention (No. 1)

2 is a cross-sectional view of the main part of FIG.

FIG. 3 is a mounting structure for a high-frequency circuit module of the present invention (No. 2)

FIG. 4 is an experimental data of surface roughness and thermal resistance of heat transfer according to the present invention.

FIG. 5: Conventional high-frequency circuit module mounting structure (No. 1)

6 is a cross-sectional view of the main part of FIG.

FIG. 7: Conventional high-frequency circuit module mounting structure (Part 2)

[Explanation of symbols]

 2 ground conductor layer 3 circuit conductor pattern 4 dielectric substrate 5 circuit board 6 high frequency circuit module 11 mounting seat 12 notch hole 14 terminal 15 screw 16 soldering 21 metal substrate 22 mounting part of high frequency circuit module 23 recess 24 step 25 2 recessed portion 26 screw hole 28 soft metal 29 bottom surface 31 metal substrate 32 mounting portion of high frequency circuit module 33 recessed portion 34 bottom surface 35 screw hole 36 soft metal 37 protrusion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kyoichi Ishii 2-12-5 Iwamotocho, Chiyoda-ku, Tokyo Inside Space Communication Basic Technology Research Institute, Inc.

Claims (2)

(57) [Claims] 1. A metal substrate (2) incorporating a semiconductor circuit element.
A mounting structure in which a soft metal (28) for heat conduction is interposed between a mounting surface of a high-frequency circuit module (6) mounted by screwing on 1) or the like and a surface of the metal substrate or the like. In the mounting state of the high frequency circuit module (6) in which the metal (28) accommodating recess (25) is formed, a part of the surfaces of the metal substrate (21) and the high frequency circuit module (6) are brought into contact with each other and the mounting position is A structure for mounting a high-frequency circuit module, characterized in that 2. The surface (24) () of the high-frequency circuit module (6) and the metal substrate (21) directly below the portion where the input / output section of the high-frequency circuit module (6) is connected to the high-frequency flat transmission line (3). 29) The mounting structure for a high-frequency circuit module according to claim 1, characterized in that they are abutted against each other.