JP4396005B2 - Circuit module and component placement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit module in which a plurality of circuit components are mounted on the front and back of a substrate, and more particularly to a component placement method in the circuit module.
[0002]
[Prior art]
Various circuit modules have been developed, such as RF modules used in radio frequency circuits of communication devices. Some of them are equipped with circuit components such as a power amplifier that generate a large amount of heat during operation. In order to prevent the heat generated in the circuit component from adversely affecting other circuit components, devise the arrangement of the circuit component on the substrate surface, or a member to dissipate heat from the circuit component that generates heat Either one of the above is required.
[0003]
As a contrivance in circuit component arrangement, first, there is a method in which a heat generating circuit component is arranged as close to the edge of the substrate as possible instead of the central portion of the substrate. Secondly, a circuit component having high temperature dependency, for example, an active element integrated circuit, is arranged as far as possible from a circuit component that generates heat. As a heat radiating member, there exists a fin for heat radiation, for example.
[0004]
[Problems to be solved by the invention]
However, coping with the circuit component arrangement on the board surface results in restrictions on the design of the circuit component arrangement on the board surface, that is, the floor plan and layout design. That is, problems arise in that the circuit component arrangement on the substrate surface is not optimal and wastes space, cannot cope with various board outlines, and the design effort is increased. Further, if heat is dealt with by providing a member dedicated to heat dissipation, an increase in size and cost due to the provision of the member will occur.
[0005]
An object of the present invention is to solve such problems, and heat generated in circuit components on the substrate surface can be generated on the other surface of the substrate without providing a dedicated member for heat dissipation. The purpose is to increase the degree of freedom in floorplanning and layout design while minimizing adverse effects on circuit components.
[0006]
[Means for Solving the Problems]
To achieve the above object, the present invention is first mounted and a substrate having first and second surfaces, a first circuit component mounted on the first surface, the second surface and a second circuit component, the circuit module to provide an electrical circuit including a first and a second circuit component, the first and second circuit components, the substrate is sandwiched by the first and second circuit component And the surfaces of the first and second circuit components are arranged and mounted so as to be close to or in contact with the substrate, and the heat generated in the first circuit component is absorbed by the second circuit component through the substrate. Or a circuit module to be dissipated , wherein the second circuit component has a larger heat capacity or surface area compared to other circuit components mounted on the substrate, or a single circuit component or a collection of a plurality of circuit components It is a body . In addition, the present invention determines the arrangement of circuit components on the substrate so as to obtain a target electric circuit prior to mounting a plurality of circuit components on the substrate having the first and second surfaces. In the component placement method to be executed , a single circuit component or a plurality of circuit components having a large heat capacity or surface area compared with other circuit components mounted on the substrate from the first circuit component through the substrate The overlapping relationship of the arrangement of the second circuit component on the second surface with respect to the arrangement of the first circuit component on the first surface is determined so that a heat propagation path to the second circuit component that is an aggregate of the first circuit component is generated. It is characterized by doing.
[0007]
Thus, in the present invention, the heat generated in the first circuit component mounted on the first surface propagates to the second circuit component mounted on the second surface via the substrate, Absorbed or dissipated by the second circuit component. Therefore, in terms of suppressing the adverse effect of the heat generated in the first circuit component on other circuit components, an effect equivalent to or higher than that obtained when a member dedicated to heat dissipation is attached to the first circuit component is obtained. It is done. In the present invention, the member that absorbs or dissipates heat generated in the first circuit component is not a member dedicated to heat dissipation, but is a second circuit component that constitutes an electric circuit together with the first circuit component. FIG. 2 is a component on a circuit diagram of a target electric circuit. That is, since parts necessary for the circuit configuration are used together for heat absorption or heat dissipation, the circuit module does not increase in size and cost in the present invention. Furthermore, the restriction imposed by the present invention on the circuit component arrangement is mainly that the first and second circuit parts are arranged so as to sandwich the board, and more than the conventional restriction on the circuit component arrangement. Since it is loose, according to the present invention, the degree of freedom regarding the design of the floor plan and the layout is increased as compared with the conventional case.
[0008]
Further , according to the present invention , the second circuit component is a single circuit component or an assembly of a plurality of circuit components having a large heat capacity or surface area compared to other circuit components mounted on the substrate. some reason, the effect of the heat absorbing or dissipating of the second circuit component becomes more pronounced.
[0009]
Secondly, the second circuit component is arranged so as to cover the entire region of the second surface that is in a relation of front and back with the covering portion of the first circuit component on the first surface. As a result, the heat transmitted to the substrate out of the heat generated in the first circuit component is efficiently transmitted to the second circuit component, and heat is propagated from the first circuit component to the second circuit component. Efficiency becomes good.
[0010]
Thirdly, the second circuit component is designed in advance so as to exhibit relatively good or stable characteristics in a state where it is heated by the first circuit component. Here, the present invention aims to prevent the circuit component mounted on the substrate surface from being affected by the heat generated by the first circuit component as much as possible, but only the second circuit component is provided. The principle of the present invention is always affected by the heat from the first circuit component. Therefore, the second circuit component is designed as described above so that better or more stable characteristics can be obtained when the first circuit component is generating heat than when it is not. Thereby, the performance of the circuit module becomes better. Note that this type of characteristic may be realized by using a circuit such as temperature deviation adjustment and temperature compensation.
[0011]
Fourth, a thermal conductor having better thermal conductivity than the substrate body is embedded in a portion of the substrate sandwiched between the first and second circuit components. This increases the efficiency of heat propagation from the first circuit component to the second circuit component. In addition, this type of thermal conductor can be realized relatively easily and inexpensively, for example, by providing a via hole on the substrate and placing and filling a conductor such as metal in the via hole.
[0012]
When the first and second circuit components are circuit components to be connected (for example, a power amplifier and a subsequent output filter), the first and second circuit components in the present invention sandwich the substrate. By utilizing the fact that they are in a positional relationship facing each other, it is possible to obtain incidental effects such as shortening the signal propagation path between the two as much as possible. Specifically, as the conductor for the connection, a conductor that penetrates the board from the periphery or directly below the first circuit component and extends to the periphery or directly below the second circuit component is provided. Thereby, the signal propagation path between the first circuit component and the second circuit component can be shortened, and attenuation, delay and other phenomena can be suppressed. Also, this type of conductor can be realized relatively easily and inexpensively in the form of a via hole or the like that connects the land or conductor pattern on the first surface and the land or conductor pattern on the second surface. Furthermore, by forming the conductor from a material that is also a heat conductor such as a metal, the heat propagation from the first circuit component to the second circuit component is made more efficient.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 shows a configuration of a circuit module according to an embodiment of the present invention. The circuit module shown in this figure is, for example, an RF module mounted on a communication device. As a component mounting surface for mounting circuit components, at least the first surface 10A of the substrate 10 and the second surface that is the back surface thereof. It has a surface 10B. The circuit components are arranged and mounted on these surfaces 10A and 10B, and are connected to each other by a conductor pattern formed on the surfaces 10A and 10B, via-hole conductors penetrating the substrate 10, or the like.
[0015]
The first surface 10A is a first circuit component 12-1 that is a heating element, and the second surface 10B is a second circuit component 12-2 that is a heat absorption / dissipation body. Has been. Each of the first and second circuit components 12-1 and 12-2 is a component constituting an electric circuit according to the illustrated circuit module. That is, it is not a part that does not appear on the circuit diagram such as a heat sink, but various active elements, passive elements, or a collection thereof. A power amplifier can be listed as an example of the first circuit component 12-1, and a filter such as a surface acoustic wave filter can be listed as an example of the second circuit component 12-2.
[0016]
In the present embodiment, the second circuit component 12-2 is used not only for its original purpose, that is, as a circuit component, but also for the purpose of dealing with heat generation in the first circuit component 12-1. is doing. That is, the heat generated in the first circuit component 12-1 is released to the second circuit component 12-2 through the substrate 10, and this heat is absorbed or dissipated by the second circuit component 12-2. I have to. In the present embodiment, this increases the degree of freedom of component placement on the component mounting surfaces 10A and 10B of the substrate 10 without providing a member dedicated to heat dissipation such as a heat sink, and at the same time, the first circuit component 12-1. Heat generation is prevented from adversely affecting other circuit components as much as possible. Furthermore, since it is not necessary to use a limiter as a countermeasure to the temperature rise, the circuit configuration is simplified.
[0017]
In this embodiment, in order to realize or increase the efficiency of heat propagation from the first circuit component 12-1 to the second circuit component 12-2, the first circuit component 12-1 and the second circuit component 12-2 are arranged so as to sandwich the substrate 10 therebetween. That is, when the substrate 10 is seen through from a direction orthogonal to the component mounting surface 10A or 10B, the projected area S1 of the first circuit component 12-1 and the projected area S2 of the second circuit component 12-2 are at least one. The first and second circuit components 12-1 and 12-2 are arranged so as to overlap each other. More preferably, as shown in FIG. 2, a component whose projected area, that is, the substrate covering area S2, is larger than the projected area of the first circuit component 12-1, that is, the substrate covering area S1, is used as the second circuit component 12-2. The first and second circuit components 12-1 and 12-2 are used so that all the portions covered by the first circuit component 12-1 are included in the covered portions by the second circuit component 12-2. Decide on placement. As a result, the rate at which the heat radiated from the first circuit component 12-1 to the substrate 10 and transmitted to the substrate 10 is transmitted to the second circuit component 12-2 increases.
[0018]
The first and second circuit components 12-1 and 12-2 are components that are in a mounted state as close as possible to the component mounting surfaces 1 A and 10 B of the substrate 10, preferably the component mounting surface 10 A of the substrate 10 in the mounted state. And it is desirable to make it a surface mount type component that contacts 10B. By preparing and using such a component, it is possible to increase the heat propagation efficiency from the first circuit component 12-1 to the substrate 10 and the heat propagation efficiency from the substrate 10 to the second circuit component 12-2. . Furthermore, it is better not to cover the mold as much as possible.
[0019]
The second circuit component 12-2 is a component that does not generate heat as much as the first circuit component 12-1. For example, if the first circuit component 12-1 is a power amplifier that generates heat during its operation, the second circuit component 12-2 is a component that does not generate heat as much as the power amplifier, such as a surface acoustic wave filter. Furthermore, the second circuit component 12-2 is a component having a heat capacity as large as possible. That is, a component that can sufficiently absorb the heat generated in the first circuit component 12-1. Thereby, it can suppress as much as possible that the 1st circuit component 12-1 has a bad influence by heat on components other than the 2nd circuit component 12-2. The second circuit component 12-2 is a component having a surface area as large as possible. Thereby, the heat radiation from the second circuit component 12-2 is efficiently performed.
[0020]
Further, as the second circuit component 12-2, one having a characteristic with as little temperature dependency as possible is used. For example, if the second circuit component 12-2 has an adjustable impedance matching circuit for connection with the circuits before and after the second circuit component 12-2, the circuit constant of the matching circuit is set to the first circuit component 12-. It is adjusted in advance according to the temperature of the second circuit component 12-2 when 1 is operating. By doing so, the second circuit component 12-2 can be operated normally or with the expected characteristics despite receiving heat from the first circuit component 12-1. Further, as shown in FIG. 3, the second circuit component 12-2 is designed so as to operate with good and stable characteristics / operation state when the first circuit component 12-1 generates heat. Thus, the characteristics as a circuit module can be improved as compared with the conventional one. The characteristics shown in FIG. 3 can be achieved only by designing / setting the design of the second circuit component 12-2, and by combining with adjustment / setting operations such as adjustment of matching circuit constants. You may make it achieve.
[0021]
When the first and second circuit components 12-1 and 12-2 are in a cascade connection relationship on the circuit diagram, the first and second circuit components 12-1 and 12-2 are arranged so as to sandwich the substrate 10. By doing so, not only the above-mentioned effect of heat countermeasures but also the performance on circuit connection can be improved. For example, as shown in FIG. 6, an input signal is supplied to a power amplifier (PA) 22 via various circuits 20, and a signal amplified by the PA 22 is band-limited and noise-removed by an output filter 24 and supplied to an antenna. Consider an RF module. As a solution to this type of circuit configuration, that is, as a solution to the heat generated in the PA 22, when the component arrangement as shown in FIG. 1 in the present embodiment is applied, the second circuit component 12-1 is connected to the back side of the PA 22. A configuration in which the output filter 24 is arranged as the circuit component 12-2 is obtained. In this configuration, the PA 22 and the output filter 24 that are in a cascade connection relationship on the circuit diagram are in a front-and-back relationship in the actual arrangement on the substrate 10, so that a conductor is filled in as shown in FIG. 4 or FIG. If the via hole 18 is used, the wiring length between them can be minimized. Moreover, since the conductor in the via hole 18 is also generally a heat conductor, it contributes to the efficiency of heat propagation.
[0022]
The example shown in FIG. 4 is an example of mounting a device having a face-down bonding such as a bare chip or a ball grid array type package, and the example shown in FIG. 5 is an example of mounting a device having various in-line packages. It is. In the figure, 12-1a and 12-2a are chip or device side conductor pads, 12-1b and 12-2b are conductor bumps, 12-1c and 12-2c are conductor terminals, and 16-1 and 16-2 are substrates. This is a land or conductor pattern provided on the 10 side. A via hole may be provided in the land itself, or the land and the via hole formation site may be separated.
[0023]
As a method of improving the heat propagation efficiency from the first circuit component 12-1 to the second circuit component 12-2, as shown in FIG. 7, the first and second circuit components 12-1 of the substrate 10 are used. And the method of providing the conductor 14 in the site | part pinched by 12-2 may be used. The conductor 14 can be realized by means such as providing many via holes. The second circuit component 12-2 is not limited to one. For example, as shown in FIG. 8, the second circuit component 12-2 may be realized by an assembly of a plurality of components. Conversely, one second circuit component 12-2 may be provided corresponding to the plurality of first circuit components 12-1. If there are a plurality of circuit components that can be used as the second circuit component 12-2, one or more of the plurality of candidates are selected so that the characteristics of the circuit module are improved. And used as the second circuit component 12-2.
[0024]
Further, in FIG. 1, the substrate 10 is a rectangular substrate, but it is not necessary to specifically limit the outer shape / contour of the substrate when the present invention is implemented. On the other hand, the degree of freedom of component placement is higher than that of the prior art, and in particular, the first circuit component 12-1 is arranged on the peripheral edge of the board, and is freed from restrictions such as being arranged separately from the active circuit components. Therefore, in a preferred embodiment of the present invention, it is possible to provide a small, inexpensive and high-performance circuit module corresponding to the substrate 10 having an irregular outer shape / contour which is not square.
[Brief description of the drawings]
1A and 1B are diagrams showing a configuration of a circuit module according to an embodiment of the present invention, in particular, FIG. 1A is a top view, FIG. 1B is a II cross-sectional view, and FIG.
FIG. 2 is a diagram showing a planar positional relationship between a first circuit component and a second circuit component.
FIG. 3 is a diagram conceptually illustrating a characteristic example of a second circuit component.
FIG. 4 is a partially enlarged cross-sectional view showing an example of an electrical connection form between a first circuit component and a second circuit component.
FIG. 5 is a partially enlarged cross-sectional view showing an example of an electrical connection form between a first circuit component and a second circuit component.
FIG. 6 is a block diagram illustrating an example in which a first circuit component and a second circuit component are in a cascade connection relationship.
FIG. 7 is a schematic cross-sectional view showing a modified example of a substrate.
FIG. 8 is a view showing a modification of the second circuit component.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Board | substrate, 10A 1st surface (component mounting surface), 10B 2nd surface (component mounting surface), 12-1 1st circuit component, 12-2 2nd circuit component, 14 conductor, 18 Via hole, 22 Power amplifier (PA), 24 output filter.

Claims (6)

A substrate having a first surface and a second surface; a first circuit component mounted on the first surface; and a second circuit component mounted on the second surface; In a circuit module that provides an electric circuit including a circuit component, the first and second circuit components are sandwiched between the first and second circuit components, and the surfaces of the first and second circuit components there are arranged and implemented to close or in contact with the substrate, heat generated in the first circuit component is a circuitry module that will be by or dissipated absorbed by the second circuit component through the substrate,
A circuit module characterized in that the second circuit component is a single circuit component or an assembly of a plurality of circuit components having a larger heat capacity or surface area than other circuit components mounted on a substrate. . The circuit module according to claim 1,
When viewed through from the direction orthogonal to the surface of the substrate, the portion covered by the second circuit component of the second surface includes all of the portion covered by the first circuit component of the first surface. A circuit module in which the first and second circuit components are mounted. 3. The circuit module according to claim 1 , wherein the second circuit component is better and more stable in a state where the second circuit component is heated by the first circuit component than in a state where the second circuit component is not heated by the first circuit component. A circuit module characterized by being a part designed to exhibit special characteristics. The circuit module according to any one of claims 1 to 3 ,
A circuit module, wherein a thermal conductor having better thermal conductivity than that of a substrate body is embedded in a portion of the substrate sandwiched between first and second circuit components. The circuit module according to any one of claims 1 to 4 ,
A circuit module characterized in that the first and second circuit components are connected by a conductor that penetrates the substrate from the periphery or directly below the first circuit component and extends to the periphery or directly below the second circuit component. Prior to mounting a plurality of circuit components on a substrate having first and second surfaces, a component placement method executed to determine the placement of circuit components on the substrate so as to obtain a target electrical circuit In
A second circuit which is a single circuit component or a collection of a plurality of circuit components having a large heat capacity or surface area compared with other circuit components mounted on the substrate through the substrate from the first circuit component ; A component arrangement characterized by determining an overlapping relationship of the arrangement of the second circuit component on the second surface with respect to the arrangement of the first circuit component on the first surface so that a heat propagation path to the circuit component occurs. Method.

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