JP2011077140A - Circuit module and method of mounting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terminal structure capable of reducing a stress applied to a solder fillet bonding a circuit module to a mounting board, preventing a bonding failure, and achieving a reliable mounting, when the circuit module is mounted on the mounting board. <P>SOLUTION: The circuit module includes a circuit board 10 having at least first and second surfaces, an element chip 20 mounted on the first surface, and a terminal (terminal electrode) 30 for mounting, which is formed on the second surface of the circuit board serving as a mounting surface in a projecting manner, wherein the terminal 30 has cross-sectionally symmetric recesses serving as solder pools. <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 a terminal shape.

For example, when an electronic component formed by mounting the element chip 120 on the circuit board 110 as shown in FIG. 8 is mounted on the mounting board 100, the solder (layer) 140 is often used. Due to the temperature difference, there is a problem that cracks are likely to occur in the solder layer 140 due to the difference in thermal expansion coefficient between the circuit board 110 of the electronic component (package) and the mounting board 100, and a bonding failure is likely to occur.
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. There has been proposed a method in which the shear stress applied to the solder is dispersed and reduced based on the difference in thermal expansion coefficient to improve the reliability of the solder joint (connection portion) (Patent Document 1).

Japanese Patent Laid-Open No. 04-171790

In the structure of Patent Document 1 above, as shown in FIG. 8, mounting terminal portions are provided at both ends of the package including the circuit board 110, and the mounting terminal portions are mounted so as to cover the side surface of the package and the lower surface. Yes. 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. In particular, the terminal at the end rather than the terminal at the center of the package receives a larger stress because it receives a larger expansion and contraction force in the X and Y directions.
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.

  Therefore, as a structure for relieving stress, a structure in which the terminal portion 130 is convex as shown in FIGS. 9 and 10 has been proposed. However, this shape is likely to cause a solder bridge (short circuit) with an adjacent terminal, and is not practical. Reference numeral 121 denotes a wiring conductor layer.

  The present invention has been made in view of the above circumstances, and when mounting a circuit module on a mounting board, the stress applied to the solder fillet that joins the circuit module and the mounting board is reduced, and bonding failure is prevented. An object of the present invention is to provide a terminal structure capable of realizing highly reliable mounting.

In view of this, the present invention provides a circuit board having at least first and second surfaces, an element chip mounted on the first surface, and a second surface of the circuit board that is a mounting surface. And a terminal module for mounting which is formed, and the terminal part constitutes a circuit module having a recess having a symmetrical cross section to be a solder pool.
With this configuration, a mounting terminal portion that protrudes from the mounting surface of the circuit board, that is, the package, and has a concave section that is symmetrical with respect to the cross section that serves as a solder pool, is mounted on the mounting substrate at that position. For this reason, since the solder layer penetrates and is fixed in the recess having a symmetrical cross section, the stress load applied to the solder itself is reduced, and as a result, solder cracks are less likely to occur than before. Further, due to the presence of the concave portion, the terminal portion is soft and bends, so that the stress is relaxed. Furthermore, since the stress is applied to the symmetrical position, solder cracks are less likely to occur than before. 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 terminal portion has a cross-shaped cross section formed on the second surface and forms a cross-shaped cross section.
According to this configuration, in addition to the above effects, further stress relaxation can be achieved.

The present invention includes the above circuit module, wherein the outer periphery of the second surface of the circuit board is circular.
According to this configuration, it is possible to uniformly disperse the stress due to heat by making the outer periphery of the second surface of the circuit board constituting the package circular. In this circuit board, only the outer periphery protrudes to form the second surface, and may have a donut shape.

The present invention includes the above circuit module in which the terminal portions are arranged on the circumference at equal intervals.
According to this configuration, the thermal stress can be more evenly distributed by arranging the terminal portions at equal intervals on the circumference of the circuit board constituting the package.

According to the present invention, in the above circuit module, the terminal portion includes a cross section formed so as to be symmetrical with respect to a line connecting the center of the terminal portion and the center of the circle.
According to this configuration, in addition to uniform distribution of stress due to heat by making the circuit board constituting the package circular, the terminal section is formed so as to be symmetric, and as a result, the solder layer is also symmetric. It is possible to further relax the stress

According to another aspect of the present invention, there is provided a circuit module including an element chip mounted on an element mounting surface of a circuit board and a mounting terminal portion having a recess having a symmetrical cross section serving as a solder pool so as to protrude from the circuit board. A circuit module mounting method comprising: a preparing step; and a step of positioning the circuit module on the mounting substrate and infiltrating solder into the recess to fix the circuit module.
According to this configuration, the mounting terminal portion having a symmetric recess serving as a solder pool is provided so as to protrude from the circuit board, and the mounting terminal portion is mounted at that position. For this reason, when compared with circuit boards of the same size due to stress relaxation caused by the flexibility of the terminal unevenness and the increase in the amount of solder and the position where the stress is applied (being symmetrical), mounting is possible due to stress relaxation. The stress load due to the thermal cycle in the process is reduced, and as a result, solder cracks are less likely to occur than before.

  According to the present invention, in the circuit module mounting method, the step of preparing the circuit module includes a step of arranging the mounting terminal portions at equal intervals on the periphery of the circular circuit board.

  According to the present invention, when the circuit module is mounted on the mounting substrate, the mounting terminal portion having the concave portion of the cross-section that becomes a solder pool is provided, so that the position where the flexibility and stress are applied (they are symmetrical). As a result, the stress relaxation due to the above and the stress load due to the thermal cycle can be reduced, and as a result, the generation of cracks can be suppressed, and a highly reliable mounting can be realized.

The perspective view of the circuit module of Embodiment 1 of this invention The principal part enlarged view of the circuit module of Embodiment 1 of this invention Sectional drawing 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 1 of this invention. The principal part expanded sectional view which shows the mounting process on the mounting substrate of the circuit module of Embodiment 1 of this invention The perspective view of the circuit module of Embodiment 2 of this invention The perspective view 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. The perspective view which shows the circuit module of a prior art example Sectional drawing 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)
1 is a perspective view showing a state where a circuit module according to a first embodiment of the present invention is viewed from a terminal portion side for mounting, FIG. 2 is an enlarged view of the main part, and FIG. FIG. 4 is an enlarged sectional view of a main part.
As shown in FIGS. 1 to 3, the circuit module 1 according to the present embodiment includes a circuit board 10 on which an element chip 20 that constitutes a gyro sensor is mounted on a first surface 10A that is a main surface. A terminal electrode 30 having a concavo-convex portion and having a cross-shaped cross section is formed as a terminal portion on the second surface 10B facing the first surface 10A. The terminal electrode 30 is composed of a conductor layer formed on the surface of the protrusion formed integrally with the resin circuit board 10 and constitutes a part of the wiring conductor layer 21 formed on the surface of the circuit board. As shown in FIG. 3, the circuit board 10 is brought into contact with a printed wiring board as the mounting board 100, and the space between the terminal electrode 30 formed on the second surface 10B and the mounting board 100 is between the circuit board 10 and the mounting board 100. It is fixed via the solder layer 40. Here, the circuit board 10 is a three-dimensional board in which a concave portion 13 constituting an element mounting region is formed on the first surface 10A. Then, solder bonding is performed on the pad 101 formed of a wiring pattern formed on the mounting substrate 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.

  According to this configuration, as in the conventional example shown in FIG. 8, the terminal electrode 30 faces 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 board 10. It protrudes on the second surface 10B and is formed to have a cross-sectional shape. With this configuration, the terminal electrode 30 is easily bent and acts as a stress absorbing portion to relieve stress. Further, the solder layer 40 formed between the terminal electrode 30 and the mounting substrate 100 penetrates into the concave portion of the terminal electrode so as to be symmetrical, and the stress is relaxed by being applied to the symmetrical position. As a result, the stress load due to the thermal cycle is reduced, and 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, first, a three-dimensional board having projections for terminal portions constituting the circuit board 10 is formed by an injection molding method. Then, the wiring conductor layer 21 is formed on the three-dimensional substrate. In the formation, first, an underlayer made of a conductive thin film is formed on the entire surface of the three-dimensional substrate by performing electroless plating, CVD, sputtering, or the like. Here, a copper thin film is formed by electroless copper plating or sputtering. Then, by irradiating the surface of the three-dimensional substrate 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 three-dimensional substrate along the outline of the wiring conductor layer to be formed by scanning with a galvanometer mirror or the like. The underlayer in the boundary region with the portion that does not match the pattern of the wiring conductor layer is removed. Accordingly, the surface of the three-dimensional substrate is irradiated with the laser beam only on the ground layer (the ground layer matching the pattern of the wiring conductor layer 21) inside the contour irradiated with the laser beam and the portion along the contour of the ground layer. A portion of the underlying layer (not shown) that does not match the 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 by electroplating on the base layer that matches the pattern of the wiring conductor layer 21, and an unnecessary plating layer other than the portion with the base layer is formed. If removed by etching, the 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 1 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, the solder layer 40 and the terminal electrode 30 formed on 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 while penetrating into the concave portion of the cross-shaped terminal portion, and the distance between the circuit module and the mounting substrate 100 is reduced, so that FIG. As shown in b), the terminal electrode 30 and the pad 101 on the mounting substrate 100 are electrically connected without a gap.

  FIG. 4 is an enlarged cross-sectional view of the terminal portion. However, according to the present embodiment, the terminal portion has a cross-shaped cross section, so that the stress is further relaxed by being soft and bending. Compared with the conventional terminal portion structure shown in FIG. 10, the amount of solder applied can be increased, and the stress is more easily dispersed. Further, since the solder penetrates into the concave portion, it hardly protrudes to the outside, and the solder bridge can be prevented.

As described above, since the solder penetrates into the recesses of the terminal portions formed symmetrically in the cross section between the circuit board 10 of the circuit module 1 and the mounting substrate 100 while solidifying and shrinking from the symmetrical direction, the thermal cycle is performed. As a result, solder cracks are less likely to occur than in the conventional case, connection is ensured, and the attitude angle with respect to the circuit module can be maintained with high accuracy.
Further, due to the presence of the concave portion, the terminal portion is soft and bends, so that the stress is relaxed. Furthermore, since the stress is applied to the symmetrical position, solder cracks are less likely to occur than before.

  As described above, according to the present invention, it is possible to securely fix, and 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. Become.

  In the first embodiment, the first surface that is the element mounting surface of the circuit board and the second surface that is the mounting surface are formed so as to face each other. It is also possible to apply to vertical mounting.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. FIG. 6 is a perspective view showing a circuit module 2 according to Embodiment 2 of the present invention.
In the above embodiment, the circuit board 10 is configured by a three-dimensional circuit board whose outer shape is a substantially rectangular parallelepiped. However, in this embodiment, the outer shape is cylindrical, and the center of the terminal portion is formed along the peripheral edge of the end surface. The terminal electrode 30 is formed of 18 protrusions at equal intervals so as to be symmetric with respect to a line connecting the circular center. In the present embodiment, as shown in FIG. 6, the wiring conductor layer 21 forms a striped electrode layer 31 along the radius of the end face in the protruding portion constituting the terminal electrode 30, and this striped electrode layer The solder layer enters the concave surface 32 in a symmetrical position with respect to 31.
The striped electrodes 31 are also formed at the same time as the wiring conductor layer formed on the surface of the circuit board 10 by plating or the like.

  When the circuit module formed in this way is mounted on the mounting substrate 100 with the solder layer 40, the stress is uniformly distributed, so that the stress can be prevented from concentrating on a specific terminal, and more solder cracks can be obtained. Is less likely to occur.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. FIG. 7 is a perspective view showing a circuit module 3 according to Embodiment 3 of the present invention.
In the second embodiment, the circuit board 10 is formed in a cylindrical shape. In the present embodiment, the circuit board 10 is also formed in a cylindrical shape, and the terminal electrode (terminal portion) 30 is formed in a cross-sectional shape as in the first embodiment. It is formed in the shape. Here, the terminal electrode 30 has a cross-shaped cross section formed so as to be symmetric with respect to a line connecting the center of the terminal electrode and the center of the circle. Here too, the terminal electrode 30 is formed by forming the wiring conductor layer 21 on the protrusion formed integrally with the circuit board.
According to this configuration, the circuit board constituting the package can be made circular to disperse the stress due to heat uniformly, and the stress is further reduced by increasing the deflection and the amount of solder due to the cross-shaped terminal. Can be realized.

  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 less, 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 Concave 20 Element chip 21 Wiring conductor layer 30 Terminal electrode 31 Striped electrode layer 32 Concave surface 40 Solder layer 100 Mounting substrate (printed wiring substrate) )
101 Pad 110 Circuit board 120 Element chip 130 Terminal part 140 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 so as to protrude from the second surface of the circuit board which is a mounting surface;
A circuit module in which the terminal portion has a cross-sectionally symmetric recess that becomes a solder pool. The circuit module according to claim 1,
The terminal portion is
A circuit module having a cross-shaped cross section formed on the second surface and forming the cross-shaped cross section. The circuit module according to claim 1 or 2, wherein
The second surface of the circuit board is circular;
The terminal part is a circuit module arranged on a circumference. The circuit module according to claim 3, wherein
The terminal portion is a circuit module arranged on the circumference at equal intervals. The circuit module according to claim 3 or 4, wherein
The circuit module which comprises the cross-shaped cross section which the said terminal part comprised so that it might become symmetrical with respect to the line | wire which connects the center of a recording terminal part, and the said circular center. A step of preparing a circuit module having a mounting terminal portion having a concave portion having a cross-sectional symmetry that becomes a solder pool so as to protrude from the circuit board, while mounting an element chip on an element mounting surface of the circuit board;
The circuit module mounting method comprising: positioning the circuit module on the mounting substrate and fixing the circuit module by infiltrating solder into the recess. A circuit module mounting method according to claim 6, comprising:
The step of preparing the circuit module includes a step of arranging the mounting terminal portions at equal intervals on the periphery of a circular circuit board.

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