JP2011066117A - Circuit module and method of mounting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit module suppressing a reduction in solder bondability at the mounting step to achieve highly reliable mounting. <P>SOLUTION: The circuit module includes at least: a circuit board 10 having a first surface 10A, a main surface of which an element chip 20 is mounted and having a second surface 10B opposing to the first surface 10A. The circuit board 10 is brought into contact with a mounting board 100 via a heat-conductive spacer member 40 and a wiring conductor layer formed on the second surface is fixed to the mounting board via a solder layer 30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a circuit module and a circuit module mounting method, and more particularly to mounting a circuit module on a mounting board (motherboard).

For example, when mounting the electronic component 120 on the mounting substrate 100 as shown in FIGS. 13 and 14, the solder 130 is often used, but the thermal expansion coefficient between the electronic component (package) 120 and the mounting substrate 100 is used. Therefore, a problem has been raised that cracks are likely to occur in the solder portion.
In order to avoid this problem, various mounting methods have been proposed.

  For example, an insulating layer thicker than the land thickness is provided between the substrate (mounting substrate) and the body of the leadless component, so that a sufficiently thick solder can be formed between the land and the electrode of the leadless component. Based on the difference in thermal expansion coefficient, the shear stress applied to the solder is dispersed and reduced to improve the reliability of the solder joint (connection part) (Patent Document 1).

  In addition, the chip component is fixed on the printed wiring board with double-sided tape, and the thickness of the double-sided tape is increased and the Young's modulus is soldered when the electrode of the chip part and the electrode on the printed wiring board are bonded and fixed with solder. A structure has also been proposed in which the Young's modulus of the double-sided tape is set so as not to interfere with the solder (Patent Document 2).

  Furthermore, a configuration has also been proposed in which an electronic component is provided with an insulator portion that protrudes toward the printed board side so as to ensure a bonding region by solder (Patent Document 3).

  In addition, when mounting a chip component on the mounting substrate, the mounting substrate corresponding to the lower part of the chip component in order to alleviate the generation of thermal stress due to the difference in thermal expansion coefficient and prevent cracks in the solder joints A structure in which a slit is formed in the upper region has also been proposed (Patent Document 4).

Japanese Patent Laid-Open No. 04-171790 Japanese Patent Laid-Open No. 05-0678758 Japanese Patent Laid-Open No. 11-026910 JP 2000-1511060 A

In the mounting structures of Patent Documents 1, 2, and 3, the insulating member is sandwiched between the electronic component and the mounting substrate, thereby increasing the gap, increasing the amount of solder, and soldering due to the difference in thermal expansion coefficient. Generation of cracks and the like can be suppressed.
According to this configuration, when soldering, an insulating member is interposed between the electronic component and the mounting substrate, so that a sufficient gap can be taken and the amount of solder that can be held can be increased. , The bondability can be improved.
However, due to the presence of these insulating members, the thermal conductivity is reduced, and when the electronic component is a power element such as a power transistor, the heat dissipation is reduced, and the heat originally radiated to the mounting substrate side is reduced. It will remain on the electronic component, which is likely to cause deterioration of the electronic component. In particular, in the case of a mounting structure that requires a repetitive solder reflow process in order to mount a large number of components, there is also a problem of generation of thermal stress due to a decrease in heat dissipation particularly during the mounting process that undergoes a repeated heating process.

  On the other hand, in Patent Document 4, the mounting substrate can be deformed by the slit and the stress relaxation is performed to suppress the occurrence of solder cracks. However, the displacement of the wiring pattern due to the deformation of the mounting substrate is also suppressed. It was a problem.

  As described above, when the electronic component is solder-mounted on the motherboard, the thermal expansion coefficient between the electronic component package and the motherboard is different, so that a crack may occur in the solder joint due to a thermal load, and various proposals have been made. However, there is a need for a mounting method that can reduce the occurrence of cracks, improve solder jointability, and suppress local temperature rise caused by thermal stress during the mounting process or in use. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a circuit module that can suppress a decrease in solderability in a mounting process and can realize highly reliable mounting.

Therefore, in the present invention, at least the first surface which is the main surface is mounted with an element, and a circuit board having a second surface opposite to the first surface is provided. Provided is a circuit module in which a wiring conductor layer formed on the second surface and a mounting substrate is fixed to each other via a solder layer through a spacer member having a property. .
According to this configuration, when the circuit module is mounted on the mounting board, the wiring conductor layer and the mounting board are connected to each other because the circuit module is in contact with the mounting board via the thermally conductive spacer member. The volume of the solder layer to be increased can be increased, and the generation of cracks due to the thermal load during mounting can be suppressed. Further, since this spacer member has thermal conductivity, it is possible to efficiently suppress a temperature rise due to heat generation of elements on the circuit module, and thermal efficiency at the time of melting the solder at the time of mounting is also good.

According to the present invention, in the circuit module, the spacer member is fixed to the second surface of the circuit board with an adhesive.
According to this configuration, since the spacer member is formed separately from the circuit board and is fixed by the adhesive, the versatility is high, and the size and material of the spacer member can be adjusted as necessary.

According to the present invention, in the circuit module, the spacer member is a member formed integrally with the circuit board.
According to this configuration, since the spacer member is integrally formed with the circuit board, the mounting workability is good.

According to the present invention, in the above circuit module, the circuit board is a three-dimensional wiring board having an element chip mounted on a first surface.
According to this configuration, it is possible to mount an element chip such as a gyro sensor or LED while maintaining the posture angle.

According to the present invention, in the circuit module, the spacer member is an elastic body.
According to this configuration, a difference in thermal expansion coefficient between the circuit board and the mounting board can be absorbed, and a highly reliable mounting structure can be realized.

In the circuit module according to the present invention, the spacer member is urethane foam having electrodes formed on both surfaces thereof, one surface being in contact with the circuit board and the other surface being in contact with the mounting substrate.
According to this configuration, since heat and electrical conductivity can be maintained, heat conduction can be efficiently realized, stress absorption can be performed while exhibiting heat dissipation characteristics.

According to the present invention, in the circuit module, the spacer member is a fin-like body having a plurality of fins.
According to this configuration, it is possible to increase heat dissipation.

According to the present invention, in the above circuit module, the fins are arranged so as to open in a direction perpendicular to a line connecting regions where the solder layers are formed.
According to this configuration, a laminar flow is efficiently generated along the fin in the opening direction, and heat dissipation is further improved.

According to the present invention, in the circuit module, the second surface of the circuit board includes a notch in a part of a region where the solder layer is formed.
According to this configuration, the volume of the solder layer can be increased by the amount of the notch, and highly reliable mounting is possible.

The present invention also includes a step of preparing a circuit module including a circuit board having at least a first surface that is a main surface and having a second surface facing the first surface, the device being mounted on the first surface; A circuit module including a step of contacting a mounting substrate via a spacer member having thermal conductivity, and fixing a wiring conductor layer formed on the second surface and a solder layer between the mounting substrate Provide the implementation method.
According to this configuration, when the circuit module is mounted on the mounting board, the wiring conductor layer and the mounting board are connected to each other because the circuit module is brought into contact with the mounting board via the thermally conductive spacer member. The volume of the solder layer can be increased, and the generation of cracks due to the thermal load during mounting can be suppressed. Moreover, since this spacer member has thermal conductivity, heat generation of elements on the circuit module can be efficiently suppressed, and thermal efficiency at the time of melting the solder at the time of mounting is also good.

According to the present invention, in the method for manufacturing a circuit module, the spacer includes a step of forming the spacer separately from the circuit board and fixing the spacer to a part of the circuit board mounting region on the mounting board.
According to this configuration, since the spacer is formed separately from the circuit board and is fixed by the adhesive, the versatility is high, and the size and material of the spacer can be adjusted as necessary.

According to the present invention, in the method for manufacturing a circuit module, the step of preparing the circuit module includes a step of integrally forming the circuit board and the spacer.
According to this configuration, since the spacer member is integrally formed with the circuit board, the mounting workability is good.

  According to the present invention, when the circuit module is mounted on the mounting board, the wiring conductor layer and the mounting board are connected to each other because the circuit module is brought into contact with the mounting board via the thermally conductive spacer member. The volume of the solder layer can be increased, the generation of cracks due to the thermal load during mounting can be suppressed, and the spacer member has thermal conductivity, so that heat generated from the elements on the circuit module can be efficiently dissipated. By doing so, temperature rise can be suppressed. Also, the thermal efficiency at the time of melting the solder during mounting is good, and unnecessary heating is eliminated.

The perspective view which shows the state which mounted the circuit module of Embodiment 1 of this invention on the mounting board | substrate. The principal part expanded sectional view which shows the state which mounted the circuit module of Embodiment 1 of this invention on the mounting board | substrate. The perspective view which shows the state which mounted the circuit module of Embodiment 2 of this invention on the mounting board | substrate. The principal part expanded sectional view which shows the state which mounted the circuit module of Embodiment 2 of this invention on the mounting board | substrate. The perspective view which shows the state which mounted the circuit module of Embodiment 3 of this invention on the mounting board | substrate. The principal part expanded sectional view which shows the state which mounted the circuit module of Embodiment 3 of this invention on the mounting board | substrate. The perspective view which shows the state which mounted the circuit module of Embodiment 4 of this invention on the mounting board | substrate. The principal part expanded sectional view which shows the state which mounted the circuit module of Embodiment 4 of this invention on the mounting board | substrate. The principal part expanded sectional view of the modification which shows the state which mounted the circuit module of Embodiment 4 of this invention on the mounting board | substrate. The principal part expanded sectional view of the modification which shows the state which mounted the circuit module of Embodiment 4 of this invention on the mounting board | substrate. The principal part expanded sectional view which shows the state which mounted the circuit module of Embodiment 5 of this invention on the mounting board | substrate. The principal part expanded sectional view which shows the state which mounted the circuit module of Embodiment 6 of this invention on the mounting board | substrate. The perspective view which shows the state which mounted the circuit module of the prior art example on the mounting board. An enlarged cross-sectional view of a main part showing a state in which a circuit module of a conventional example is mounted on a mounting board.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view showing a state in which the circuit module according to the first embodiment of the present invention is mounted on a mounting substrate, and FIG. 2 is a cross-sectional view of a main part showing a state in which the circuit module is mounted on the mounting substrate.
As shown in FIGS. 1 and 2, the circuit module 1 according to the present embodiment has an element chip 20 constituting a gyro sensor mounted on a first surface 10A that is a main surface, and the first surface 10A. The circuit board 10 has a second surface 10B facing each other. The circuit board 10 is brought into contact with the printed wiring board as the mounting board 100 through the copper block as the spacer member 40 having thermal conductivity, and the wiring conductor layer 21 formed on the second surface 10B and The mounting substrate 100 is fixed via a solder layer 30. Here, the circuit board 10 is a three-dimensional board in which a concave portion constituting an element mounting region is formed on the first surface 10A. Then, it is mounted on the pad 101 formed on the mounting substrate (motherboard) 100 via the solder layer 30. Here, the wiring conductor layer 20 connected to the pad on the mounting surface on the circuit board 10, the die pad (element mounting region) formed on the element chip mounting surface, and the wiring conductor layer 21 including the bonding pad are sputtered on the resin substrate. A base layer is formed by the method, and a plating layer is formed on the base layer. The connection between the element chip 20 and the circuit board may be flip-chip bonding or wire bonding.

  Here, the space between the circuit board 10 and the mounting board 100 is increased by the amount of the spacer member 40, the volume of the solder layer 30 can be increased, and the generation of cracks due to the thermal load during mounting can be suppressed. In addition, since the copper block constituting the spacer member 40 has thermal conductivity, the element chip 20 on the circuit module 1 (circuit board 10) can dissipate heat efficiently and the temperature rise can be suppressed. Also, the thermal efficiency at the time of melting the solder during mounting is good, and unnecessary heating is eliminated.

  In manufacturing, since the gyro sensor is mounted on the first surface 10A, the circuit board 10 is designed and manufactured so that the directionality of the first surface is maintained.

  Here, when forming the wiring conductor layer on the three-dimensional substrate constituting the circuit board, first, an underlying layer made of a conductive thin film is formed on the entire surface of the substrate 10 by performing electroless plating, CVD, sputtering, or the like. Form. Here, a copper thin film is formed by electroless copper plating or sputtering. Then, by irradiating the surface of the substrate 10 with a laser beam, the underlying layer of the irradiated portion is patterned and selectively removed. Here, the laser beam is irradiated while moving on the surface of the substrate 10 along the outline of the wiring conductor layer to be formed by scanning with a galvanometer mirror or the like, and the portion of the underlying layer that matches the pattern of the wiring conductor layer ( Hereinafter, the underlayer in the boundary region between the “underlayer” and the portion not matching the pattern of the wiring conductor layer is removed. Therefore, the surface of the substrate 10 was irradiated with the laser beam only on the inner layer of the contour irradiated with the laser beam (underlying layer matching the pattern of the wiring conductor layer) and the portion along the contour of the underlying layer. An underlayer (not shown) remains. However, when the interval between the adjacent wiring conductor layers is narrow, it is possible to remove not only the contour portion but also the entire underlying layer between the wiring conductor layers by laser beam irradiation as described above.

  Subsequently, a surface conductor layer is formed by thickening a plating layer such as copper on the underlying layer that matches the pattern of the wiring conductor layer by electroplating, and unnecessary underlying plating layers other than the underlying layer are removed by etching. Then, a circuit board on which a desired circuit pattern is formed can be obtained.

  Thus, the circuit board 10 having the wiring conductor layer 21 on the surface is designed, and the element chip 20 is arranged on the circuit board.

  Then, after a copper block as a spacer member is fixed on the mounting substrate 100 and the solder layer 30 is formed, the circuit module on which the element chip 20 is mounted on the circuit substrate 10 is aligned and heated to a desired temperature. Then, solder reflow is performed to connect the circuit board 10, the pad 101 on the mounting substrate 100, and the wiring conductor layer 21. At this time, due to the presence of the spacer member 40, a sufficient area of the solder layer 30 can be taken, and a stronger connection can be achieved.

  Thus, the volume of the solder layer 30 that connects the wiring conductor layer 21 and the pad 101 on the mounting substrate 100 can be increased, and the occurrence of cracks due to the thermal load during mounting can be suppressed. . Furthermore, since the spacer member 40 has thermal conductivity, the temperature rise can be suppressed by efficiently radiating the heat generated by the elements on the circuit module. Also, the thermal efficiency at the time of melting the solder during mounting is good, and unnecessary heating is eliminated.

  In addition, according to the above configuration, it is possible to maintain a highly accurate angle even when mounting a sensor device such as a gyro sensor whose directionality is extremely important.

  Further, since the circuit board may be mounted on the mounting board 100 via the spacer member after the circuit board is manufactured, the versatility of the circuit board is improved.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. FIG. 3 is a perspective view showing a state in which the circuit module according to the second embodiment of the present invention is mounted on a mounting board, and FIG. 4 is an enlarged cross-sectional view of a main part showing a state in which the circuit module is mounted on the mounting board.
In the circuit module 1 of the first embodiment, a copper block is used as the spacer member 40. However, the present embodiment is characterized in that copper fins 41 are configured instead of the copper block. The fins 41 are arranged so as to open in a direction perpendicular to a line connecting regions where the solder layers 30 are formed.
Since other parts are formed in the same manner as in the first embodiment, the description is omitted here.
According to this configuration, a laminar flow is efficiently generated along the fin in the opening direction, and heat dissipation is further improved.
In this case as well, the versatility of the circuit board is improved because the circuit board may be mounted on the mounting board 100 via the spacer member after the circuit board is manufactured.
Note that the fin is not necessarily made of metal, and a ceramic piece or the like may be fixed with an adhesive.
Furthermore, the number of fins is not necessarily one, and a plurality of fins may be combined and can be adjusted as appropriate.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. FIG. 5 is a perspective view showing a state in which the circuit module according to Embodiment 3 of the present invention is mounted on a mounting board, and FIG. 6 is an enlarged cross-sectional view of a main part showing a state in which the circuit module is mounted on the mounting board.
In the circuit module 1 according to the first embodiment, a copper block is used as the spacer member 40. However, in this embodiment, when the circuit board 10 is formed by injection molding, the protruding portion 10S is formed instead of the copper block. In this way, a conductor layer 21S (see FIG. 6) is formed on the surface to give thermal conductivity. The conductor layer 21S is assumed to be in a floating state without being electrically connected to other wiring. The conductor layer 21 </ b> S is formed in the same process as the wiring conductor layer 21.
Since other parts are formed in the same manner as in the first embodiment, the description is omitted here.
According to this configuration, since the protruding portion 10S serving as a spacer is integrally formed, in addition to the effects of the first and second embodiments, the manufacturing is easy and the mounting is easy without any positional deviation. To be successful.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. FIG. 7 is a perspective view showing a state in which the circuit module according to the second embodiment of the present invention is mounted on a mounting board, and FIG. 8 is an enlarged cross-sectional view of a main part showing a state in which the circuit module is mounted on the mounting board.
In the circuit module 1 of the present embodiment, the notch 11 is formed in the circuit board mounting diagram, and the volume of the solder layer is increased. That is, the notch 11 is provided in a part of the region where the solder layer is formed on the second surface 10B of the circuit board 10.
Others are formed in the same manner as in the first embodiment.
According to this configuration, the volume of the solder layer can be increased by the amount of the notch, and in addition to the effect of the first embodiment, the bondability is further increased, and the difference in thermal expansion coefficient between the circuit board and the mounting board is increased. Occurrence of cracks in the solder layer due to this is suppressed, and highly reliable mounting becomes possible. In particular, in the case of a gyro sensor, since it is necessary to maintain the attitude angle with an extremely high accuracy of ± 1 degree, it is necessary to reduce the thickness of the solder layer. The amount is secured and a strong connection is possible.

  Moreover, as a shape of a notch, as shown in FIG.9 and FIG.10, you may form circular 11C or the step-like notch 11S.

(Embodiment 5)
Next, a fifth embodiment of the present invention will be described. FIG. 11 is an essential part enlarged cross-sectional view showing a state where the circuit module 1 according to the fifth embodiment of the present invention is mounted on the mounting substrate 100.
In the first embodiment, a copper block is used as the spacer member. However, in this embodiment, instead of the copper block, urethane foam, which is an elastic body, is impregnated with a metal such as copper as a spacer member. Metal-impregnated urethane 42 is used.
Since other configurations are the same as those in the first embodiment, description thereof is omitted here.

  According to this configuration, the metal-impregnated urethane 42 having thermal conductivity and elastic body absorbs the difference in thermal expansion coefficient between the circuit board and the mounting board and has thermal conductivity. A highly reliable mounting structure with good conductivity and good heat dissipation can be realized.

(Embodiment 6)
Next, a sixth embodiment of the present invention will be described. FIG. 12 is an enlarged cross-sectional view of a main part showing a state where the circuit module 1 according to the sixth embodiment of the present invention is mounted on the mounting substrate 100.
In the fifth embodiment, as the spacer member, the metal-impregnated urethane 42 in which a foamed urethane, which is an elastic body, is impregnated with a metal such as copper, is used as the spacer member. Is used. That is, the metal-impregnated urethane 43 in which electrodes 44 and 45 made of a heat conductive material such as gold-plated nickel are formed on both the circuit board 10 side and the mounting board 100 side is used.
Since other configurations are the same as those in the first embodiment, description thereof is omitted here.

According to this configuration, in addition to the fifth embodiment, the thermal conductivity is further improved, the mounting can be surely performed, and the reliability can be further improved.
In the above circuit module, metal-impregnated urethane is used, but it goes without saying that other materials may be used as long as they are electrically insulating and have good thermal conductivity. Absent.

  In the above embodiment, the circuit module (sensor module) on which a sensor chip such as a gyro sensor is mounted has been described. However, the present invention is not limited to the sensor module, and is mounted on a module mounted on a portable terminal or the like or on a wall surface. The present invention can be applied to various circuit modules such as LED modules for LED lighting.

In the above embodiment, a resin solid substrate formed by injection molding is used as the circuit substrate. However, a ceramic substrate or a laminated substrate using a green sheet may be used. Here, for example, it is made of ceramic dielectric material LTCC (Low Temperature Co-fired Ceramics) that can be sintered at a low temperature of 1000 ° C. or lower, and is made of a low resistivity Ag on a green sheet having a thickness of 10 μm to 200 μm. A conductive paste such as Cu or Cu is printed to form a predetermined pattern, and a plurality of green sheets are used as an insulating layer, and are laminated together as appropriate, and sintered to provide an insulating layer (dielectric) Body layer). As these dielectric materials, for example, Al, Si, Sr as main components, Ti, Bi, Cu, Mn, Na, K as subcomponents, Al, Si, Sr as main components, Ca, Pb A material containing Na, K as a multicomponent, a material containing Al, Mg, Si, Gd, or a material containing Al, Si, Zr, Mg is applicable. Here, a material having a dielectric constant of about 5 to 15 is used. In addition to the ceramic dielectric material, it is also possible to use a resin multilayer substrate or a multilayer substrate made of a composite material obtained by mixing a resin and ceramic dielectric powder. Further, the ceramic substrate is made of HTCC (High Temperature Co-fired Ceramics) technology, the dielectric material is mainly Al ₂ O ₃ , and the transmission line is made of tungsten or the like as the internal conductor layer. You may comprise as a metal conductor which can be sintered at high temperature, such as molybdenum.

  Moreover, it is applicable to other ceramics without being limited to the green sheet, and when a resin substrate such as glass epoxy resin, polyimide resin, polyester resin, polyethylene terephthalate resin is used, a laminated substrate using a prepreg It is also applicable to.

  Although the case where the element chip is mounted on the circuit board has been described in the above embodiment, an electronic component package may be used instead of the element chip.

DESCRIPTION OF SYMBOLS 1 Circuit module 10 Circuit board 10A 1st surface 10B 2nd surface 10S Protrusion part 20 Element chip 21 Wiring conductor layer 30 Solder layer 40 Spacer member 41 Fin 42 Metal impregnation urethane 43 Metal impregnation urethane 44, 45 Electrode 100 Mounting board ( Printed wiring board)
101 pad

Claims (8)

  An element is mounted on at least a first surface which is a main surface, and a circuit board having a second surface facing the first surface is provided, and the circuit board includes a spacer member having thermal conductivity. A circuit module that is brought into contact with the mounting substrate and the wiring conductor layer formed on the second surface and the mounting substrate are fixed to each other via a solder layer. The circuit module according to claim 1,
The said spacer member is a circuit module fixed to the 2nd surface of the said circuit board via an adhesive agent. The circuit module according to claim 1,
The said spacer member is a circuit module which is a member integrally formed with the said circuit board. The circuit module according to claim 3, wherein
The circuit board is a circuit module which is a three-dimensional wiring board having an element chip mounted on a first surface. The circuit module according to any one of claims 1 to 4,
The circuit module, wherein the second surface of the circuit board has a notch in a part of a region where the solder layer is formed. Providing a circuit module including a circuit board having at least a second surface opposite to the first surface while mounting an element on a first surface that is a main surface;
A circuit module including a step of contacting a mounting substrate via a spacer member having thermal conductivity, and fixing a wiring conductor layer formed on the second surface and a solder layer between the mounting substrate How to implement A circuit module mounting method according to claim 6, comprising:
The spacer is formed separately from the circuit board,
A circuit module mounting method including a step of fixing the spacer to a part of the circuit board mounting region on the mounting board. A circuit module mounting method according to claim 6, comprising:
The step of preparing the circuit module includes:
A circuit module mounting method including a step of integrally molding the circuit board and the spacer.

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