JP2011071422A - Circuit module, and method of mounting circuit module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve mounting of high reliability by preventing solder cracking when a circuit module is mounted on a mounting substrate. <P>SOLUTION: The circuit module includes a circuit board having at least a first surface and a second surface, an element chip mounted on the first surface, and a mounting terminal part formed on the second surface of the circuit board, the mounting terminal part being connected to a wiring pattern on the mounting substrate through solder. <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, as shown in FIG. 8, when an electronic component having the element chip 120 mounted on the circuit board 110 is mounted on the mounting substrate 100, the solder layer 130 is often used, but the circuit board of the electronic component (package) is used. Due to the difference in thermal expansion coefficient between 110 and the mounting substrate 100, a problem has been raised that the solder layer 130 is likely to crack.
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).

Japanese Patent Laid-Open No. 04-171790

At this time, mounting terminal portions are provided at both end portions of the package including the circuit board, and the mounting terminal portions are mounted so as to run from the side surface to the lower surface of the package. At this time, if the package size is large and a thermal cycle is applied, the package, the mounting board, and the solder are greatly expanded and contracted, and stress is generated due to the difference in linear expansion coefficient between them, and solder cracks are likely to occur.
For this reason, even in the structure of Patent Document 1, the occurrence of solder cracks or the like due to the difference in thermal expansion coefficient cannot be sufficiently suppressed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent solder cracks from occurring when a circuit module is mounted on a mounting board, and to realize highly reliable mounting.

Therefore, the present invention provides a circuit board having at least a first surface and a second surface, an element chip mounted on the first surface, and a mounting board formed on the second surface of the circuit board. And a circuit module configured to be connected to the wiring pattern on the mounting substrate via solder.
With this configuration, the mounting terminal portion is provided inside the circuit board, that is, the outer surface of the package, and is mounted on the mounting board at that position. For this reason, when compared with the circuit board of the same size, the distance between solders becomes shorter than before. For this reason, the stress load by a thermal cycle is reduced and it becomes difficult to generate a solder crack conventionally. Here, the first and second surfaces may be in any positional relationship as long as they are other than the same surface.

The present invention includes the circuit module, wherein the mounting terminal portion is a concave terminal formed on the second surface and capable of being filled with the solder.
With this configuration, in addition to the above effects, the solder is filled in the concave portion of the concave terminal, so that the stress load applied to the solder itself is reduced, and as a result, solder cracks are less likely to occur.

According to the present invention, in the above circuit module, the concave terminal includes a via hole provided on the second surface so as to reach a wiring layer inside the circuit board, and a conductor portion provided on the inner wall of the via hole. Including those composed of.
With this configuration, in addition to the above effects, the solder is filled in the concave portion of the concave terminal, so that the stress load applied to the solder itself is reduced, and as a result, solder cracks are less likely to occur.

According to the present invention, in the above circuit module, the conductor portion is formed of the same layer as a wiring conductor layer formed on the surface of the circuit board.
With this configuration, the film formation process is common and only the patterning mask needs to be changed. For example, when the wiring conductor layer is formed by a plating method or the like, it can be formed very easily because it only needs to be immersed in a plating bath. Then, the stress load applied to the solder itself is reduced, and as a result, solder cracks are less likely to occur.

In the circuit module according to the present invention, the via hole is a hole formed so as to penetrate from the second surface to the first surface, and a conductor layer is formed on an inner wall of the hole. Including those in which a part of the via hole is filled with solder.
According to this configuration, since a space is created at the time of mounting, it plays a role of air escape, generation of voids is suppressed, and stronger bonding is realized.

The present invention also provides a circuit board having at least a first surface and a second surface, an element chip mounted on the first surface, and a mounting formed on the second surface of the circuit board. A step of preparing a circuit module including a terminal portion, and a step of positioning the circuit module on the mounting substrate on a mounting substrate having a wiring pattern and fixing the circuit module via solder. This is a circuit module mounting method.
According to this configuration, the mounting terminal portion is provided inside the circuit board, that is, the outer surface of the package, and is mounted on the mounting board at that position. For this reason, when compared with the circuit board of the same size, the distance between solders becomes shorter than before. For this reason, the stress load due to the thermal cycle in the mounting process is reduced, and as a result, solder cracks are less likely to occur than before.

According to the present invention, in the method for manufacturing a circuit module, a via hole provided so that a mounting terminal portion penetrates from the second surface to the first surface, and a conductor portion provided on the inner wall of the via hole. The fixing step includes a step of melting and fixing solder while sucking from the first surface side.
According to this configuration, it has a via hole provided so as to penetrate from the second surface to the first surface, and the molten solder rises on the surface of the conductor portion provided on the inner wall of the via hole, Since it is fixed while extruding air, there is no generation of voids, and highly reliable mounting is possible.

  According to the present invention, when the circuit module is mounted on the mounting substrate, the stress distance due to the thermal cycle is reduced because the distance between the solders is shortened. As a result, the occurrence of cracks can be suppressed, and the reliability can be improved. High implementation can be realized.

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 mounted on the mounting board | substrate of the circuit module of Embodiment 1 of this invention. The principal part expanded sectional view which shows the mounting process on the mounting board | substrate of the circuit module of Embodiment 1 of this invention The principal part expanded sectional view which shows the state mounted on the mounting board | substrate of the circuit module of Embodiment 2 of this invention. The principal part expanded sectional view which shows the mounting process on the mounting substrate of the circuit module of Embodiment 2 of this invention The principal part expanded sectional view which shows the state mounted on the mounting board | substrate of the circuit module of Embodiment 3 of this invention. The principal part expanded sectional view which shows the mounting process on the mounting board of the circuit module of Embodiment 3 of this invention The perspective view which shows the state which mounted the circuit module of the prior art example on the 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 includes a circuit board 10 on which an element chip 20 constituting a gyro sensor is mounted on a first surface 10 </ b> A that is a main surface. The terminal electrode 30 is formed on the second surface 10B facing the first surface 10A. The terminal electrode 30 constitutes a part of the wiring conductor layer 21 formed on the surface of the circuit board 10. The circuit board 10 is brought into contact with a printed wiring board as the mounting board 100, and the terminal electrode 30 formed on the second surface 10B and the mounting board 100 are fixed to each other through the solder layer 40. Has been. Here, the circuit board 10 is a three-dimensional board in which the concave portion 13 constituting the element mounting region is formed on the first surface 10A. Then, it is directly bonded onto the pad 101 made of a wiring pattern formed on the mounting substrate (motherboard) 100. Here, a wiring conductor layer (not shown) connected to a pad (not shown) on the mounting surface on the circuit board 10, a die pad (element mounting region) formed on the element chip mounting surface, and a wiring conductor including a bonding pad The layer 21 is formed by forming a base layer by a sputtering method on a resin substrate on which a protruding portion having a predetermined height is formed by three-dimensional molding, and forming a plating layer on the base layer. The connection between the element chip 20 and the circuit board 10 may be flip chip bonding or wire bonding.

  Here, as in the conventional example shown in FIG. 8, the terminal electrode 30 is a second surface facing the mounting substrate 100 in place of the terminal made of the wiring conductor layer formed from the side surface to the lower surface of the circuit substrate 10. Is formed. With this configuration, the distance between the solder layers 40 formed between the terminal electrode 30 and the mounting substrate 100, that is, the inter-solder distance L1, is shorter than in the conventional example, thereby reducing the stress load due to the thermal cycle, As a result, solder cracks are less likely to occur than before.

  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 21 on the three-dimensional board constituting the circuit board 10, first, the entire surface of the circuit board 10 is made of a conductive thin film by performing electroless plating, CVD, sputtering, or the like. An underlayer is formed. Here, a copper thin film is formed by electroless copper plating or sputtering. Then, by irradiating the surface of the circuit board 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 circuit board 10 along the outline of the wiring conductor layer to be formed by scanning with a galvanometer mirror or the like, and a portion of the underlying layer that matches the pattern of the wiring conductor layer And the base layer in the boundary region between the portion not matching the pattern of the wiring conductor layer is removed. Therefore, the surface of the circuit board 10 is irradiated with the laser beam only on the inner layer of the contour (underlying layer matching the pattern of the wiring conductor layer 21) irradiated with the laser beam and the portion along the contour of the underlying layer. A portion of the underlying layer (not shown) that does not match the formed pattern remains. However, when the interval between the adjacent wiring conductor layers 21 is narrow, it is possible to remove not only the contour portion but also the entire underlying layer between the wiring conductor layers 21 by laser beam irradiation as described above.

  Subsequently, a surface conductor layer is formed by thickening a plating layer such as copper on the base layer that matches the pattern of the wiring conductor layer 21 by electroplating, and unnecessary base plating layers other than the base layer are etched. If removed, a circuit board 10 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 10.

A method for mounting the circuit module thus formed on the mounting substrate 100 will be described.
First, as shown in FIG. 3A, the solder layer 40 is formed on the mounting substrate 100 while the supply amount is controlled by a dispenser. At this time, it is desirable to form a wiring conductor layer as a terminal electrode wiring in a corresponding region on the circuit board 10 and also to form a pad 101 on the mounting board 100.

  Then, as shown in FIG. 3B, the solder layer 40 and the second surface 10B of the circuit board 10 are brought close to contact with each other.

  Then, when cured by heating to the solder reflow temperature and cooling, the solder solidifies and shrinks, and the distance between the circuit module and the mounting substrate 100 approaches, so that as shown in FIG. 30 and the pad 101 on the mounting substrate 100 are electrically connected.

  Thus, since the circuit board 10 of the circuit module 1 and the mounting board 100 are connected on the inner side of the package side surface, the stress load due to the thermal cycle is reduced by shortening the distance L1 between the solders. As a result, solder cracks are less likely to occur than in the prior art, connection is ensured, and the attitude angle with respect to the circuit module can be maintained with high accuracy.

  As described above, according to the present invention, it is possible to realize a reliable connection while maintaining a highly accurate angle in mounting a sensor device whose directionality is extremely important, such as a gyro sensor, due to a shortened distance between solders. It becomes possible.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. FIG. 4 is a cross-sectional view of a principal part showing a state in which the circuit module 2 according to the second embodiment of the present invention is mounted on the mounting substrate 100, and FIGS. It is a principal part expanded sectional view which shows a mounting process.
In the above embodiment, the terminal electrode 30 is formed on the second surface 10B of the circuit board 10. However, in this embodiment, the via hole 32 is formed on the second surface 10B of the circuit board 10, and the via hole 32 is formed in the via hole 32. The wiring conductor layer 21 is formed on the concave terminal 31 to form a concave terminal 31. The concave terminal 31 is filled with solder and filled with a solder layer 40 serving as a bonding layer. Here, the concave terminal 31 includes a via hole 32 provided on the second surface 10B so as to reach a wiring layer (not shown) inside the circuit board 10, and a conductor portion provided on the inner wall of the via hole 32. Including those composed of. This conductor portion is formed simultaneously with the wiring conductor layer formed on the surface of the circuit board 10 by plating or the like.

A method for mounting the circuit module thus formed on the mounting substrate 100 will be described.
First, as shown in FIG. 5A, the solder layer 40 is formed on the mounting substrate 100 while the supply amount is controlled by a dispenser. At this time, it is desirable to form the wiring conductor layer 21 as the terminal electrode wiring in the corresponding region on the circuit board 10 and also to form the pad 101 on the mounting board 100.

  Then, as shown in FIG. 5B, the solder layer 40 and the second surface 10B of the circuit board 10 are brought close to contact with each other.

  Then, it is heated to the solder reflow temperature, the solder is solidified and contracted, and the distance between the circuit module and the mounting board is reduced, so that the concave terminal 31 and the pad 101 on the board 100 are formed without a gap as shown in FIG. Are electrically connected.

  With this configuration, since the solder is filled in the concave portion of the concave terminal 31, the stress load applied to the solder itself is reduced, and as a result, solder cracks are less likely to occur. The distance L2 between the solders is also shorter than that in the first embodiment.

  With this configuration, it is possible to easily form the wiring conductor layer by forming it on the inner wall of the via hole in the sputtering or electroless plating process for forming the base layer of the wiring conductor layer, and forming the plating layer on the upper layer. For example, when the wiring conductor layer is formed by a plating method or the like, it can be formed very easily because it only needs to be immersed in a plating bath. According to this configuration, the stress load applied to the solder itself is reduced, and as a result, solder cracks are less likely to occur.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. FIG. 6 is a perspective view showing a circuit module according to Embodiment 3 of the present invention, and FIGS. 7A to 7C are enlarged cross-sectional views of main parts showing a mounting process for mounting the circuit module on a mounting board.
In the embodiment, the via hole 32 is formed in the second surface 10B of the circuit board 10, the wiring conductor layer 21 is formed in the via hole 32, the concave terminal 31 is configured, and the solder in the concave terminal 31 is formed. In this embodiment, the through hole 14 penetrating from the second surface 10B of the circuit board 10 to the first surface 10A opposite to the first surface 10A is formed. A conductor portion is also formed on the inner wall of the through hole 14, and solder reflow is performed while suctioning from the first surface 10A side with a suction nozzle, thereby performing solder connection while letting air escape to the first surface 10A side. Thus, a reliable connection without voids is realized. This conductor portion is also formed simultaneously with the wiring conductor layer formed on the surface of the circuit board 10 by plating or the like.

A method for mounting the circuit module thus formed on the mounting substrate 100 will be described.
First, as in the second embodiment, as shown in FIG. 7A, the solder layer 40 is formed on the mounting substrate 100 while the supply amount is controlled by a dispenser.

  Then, a three-dimensional circuit board in which a conductor portion is formed on the inner wall of the through hole 14 is formed, the element chip 20 is mounted, and electrical connection is made to form the circuit module 3. As shown in FIG. 7B, the circuit module 3 is brought close to a place where the solder layer 40 and the second surface 10 </ b> B of the circuit board 10 come into contact with each other.

  Then, the solder is sucked with a suction nozzle (not shown), heated to the reflow temperature, cooled and solidified and contracted, and the distance between the circuit module and the mounting board is reduced, as shown in FIG. The concave terminal 31 and the pad 101 on the mounting substrate 100 are electrically connected without any gap.

  With this configuration, since the solder layer 40 is filled in the through hole of the concave terminal 31, a reliable connection without a void is realized, the stress load applied to the solder itself is reduced, and as a result, solder cracks further occur. It becomes difficult.

  According to this configuration, the stress load applied to the solder itself is greatly reduced, and as a result, solder cracks are less likely to occur. The distance L3 between the solders is also shorter than that in the second embodiment.

  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-described embodiment, the example in which the three-dimensional wiring board in which the recesses are formed in the element mounting area is used as the circuit board has been described. is there. Here, the circuit board on which the element chip is mounted may be covered with a resin or the like to form a package. However, the circuit board itself may surround the element chip and serve as a package.

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.

1, 2, 3 Circuit module 10 Circuit board 10A First surface 10B Second surface 13 Recess 14 Through hole 20 Element chip 21 Wiring conductor layer 30 Terminal electrode 31 Recessed terminal 32 Via hole 40 Solder layer 100 Mounting substrate (printed wiring substrate) )
101 Pad 110 Circuit board 120 Element chip 130 Solder layer

Claims (7)

A circuit board having at least first and second surfaces;
An element chip mounted on the first surface;
A mounting terminal portion formed on the second surface of the circuit board which is a mounting surface;
A circuit module in which the mounting terminal portion is connected via solder. The circuit module according to claim 1,
The mounting terminal portion is
A circuit module which is a concave terminal formed on the second surface and capable of being filled with the solder. The circuit module according to claim 1,
The concave terminal is a circuit module configured by a via hole provided on the second surface so as to reach a wiring layer inside the circuit board and a conductor provided on an inner wall of the via hole. The circuit module according to claim 3, wherein
The conductor module is a circuit module composed of the same layer as a wiring conductor layer formed on the surface of the circuit board. The circuit module according to claim 3 or 4, wherein
The via hole is a hole formed so as to penetrate from the second surface to the first surface;
A circuit module in which a conductor layer is formed on an inner wall of the hole, and a solder is filled in a part of the via hole. A circuit board having at least a first surface and a second surface facing the first surface;
An element chip mounted on the first surface;
Preparing a circuit module comprising a mounting terminal portion formed on the second surface of the circuit board;
A circuit module mounting method comprising: a step of positioning the circuit module on the mounting substrate having a wiring pattern and fixing the circuit module via solder. A circuit module mounting method according to claim 6, comprising:
The mounting terminal portion includes a via hole provided so as to penetrate from the second surface to the first surface, and a conductor portion provided on the inner wall of the via hole,
The circuit module mounting method, wherein the fixing step is a step of melting and fixing solder while sucking from the first surface side.

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