JP2012089803A - Surface mount component, mounting substrate and mounting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-profile, compact and highly reliable mounting structure with a reduced solder flux residue, even in a surface mount component of a multi-pin structure.SOLUTION: In the mounting structure having a surface mount component 10 having a mounting area in at least one surface of a package 11, and mounted on a printed wiring board 20 as a mounting substrate, at least one of the package 11 and the mounting substrate includes a recess 13 communicating through an outer surface of the package 11, in an area in which the package 11 is opposite to the mounting substrate.

Description

  The present invention relates to a surface-mounted component, a mounting substrate, and a mounting structure, and more particularly to reduction of flux residue during reflow.

  In an inclination detection unit that detects a direction component of gravitational acceleration with an acceleration sensor and detects this as an inclination angle with respect to the direction of gravity, the acceleration sensor needs to be mounted while maintaining the inclination angle on the circuit board with high accuracy.

  Such an acceleration sensor usually has a package structure for surface mounting. In particular, in the structure in which the lead terminal is formed so as to enter the lower surface of the package, the space with the bottom surface of the mounted component is narrow. When a multi-pin semiconductor device having more than 8 pins is configured, the land area is large with respect to the mounting surface, and the space between the mounting substrate and the package is extremely small. For this reason, a solution component such as isopropyl alcohol (IPA) contained in the solder paste does not evaporate during reflow, and tends to remain between the mounting substrate and the package as a flux residue. In particular, flux residue remains easily in the vicinity of the center of the bottom surface of the package, that is, in a region far from the outer surface.

  For this reason, the flux remains between the lands of the mounting board and the back surface of the mounting component, so that moisture is drawn in when the solution component in the flux residue evaporates under high temperature and high humidity. There was a problem of lowering.

  Conventionally, a structure has been proposed in which a thin bonding wire is cut to form a stud, a gap is formed between the mounting substrate and the bottom surface of the electronic component, and cleaning for removing flux after soldering is facilitated. (Patent Document 1).

  A structure in which lead terminals are formed so as to be concave on the bottom and side surfaces of the package has also been proposed (Patent Document 2). In this case, the recess is filled with solder so that it can be connected. For this reason, even if the outflow of solder is reduced, there is no gap between the package and the mounting substrate, and a residue is generated once the flux flows out into the gap during reflow.

  Furthermore, there has also been proposed a semiconductor sensor in which a plurality of protrusions are integrally formed of the same material as the case plate and metallized to form terminal electrodes. (Patent Document 3).

Utility Model Registration No. 2568788 JP 2007-132687 A JP 2007-43017 A

  However, in the mounting structure of Patent Document 1, the thin bonding wire is cut into a stud shape, and as a result, the height is increased by the amount of the stud, thereby preventing a reduction in height.

  Moreover, in the mounting structure of Patent Document 2, the solder joint portion is a recess, but the package and the mounting substrate are in close contact with each other. Further, when the solder is thickened, the height is increased, and a gap is formed between the package and the mounting substrate. However, the solder is likely to flow out of the recess, and if it flows out, a short circuit is likely to occur.

  In the mounting structure disclosed in Patent Document 3, a gap is formed as a result of forming the protrusions. However, in this case as well, the mounting structure is substantially thick and prevents a reduction in height.

Further, in recent years, there has been a demand for small and thin surface-mounted components. For example, as one of the acceleration sensors, as shown in FIGS. 21 (a) and (b) and FIGS. 22 (a) and (b). In addition, the surface-mounted component 110 in which the terminal electrode 112 occupying most of the mounting surface 110a, more than half, is used. As shown in FIGS. 23A and 23B, when the surface mounting component whose mounting area is in the package plane is mounted on the mounting board 120, the gap is small. For this reason, as shown in FIG. 21, the flux residue due to the solder flux tends to remain in the central portion R1 of the mounting surface 110a of the surface mounting component 110. Further, as shown in FIG. 24, the flux residue due to the solder flux also remains on the mounting substrate 120 side, particularly in the inter-land 122 region R2.
As described above, there is a problem that flux residues are likely to remain in the central portions R1 and R2 of the mounting surface.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mounting structure that is low in profile, small in size, and highly reliable, even in a multi-pin surface mount component. To do.

  Accordingly, the present invention provides a mounting structure in which a surface mounting component whose mounting area is in at least one surface of a package is mounted on a mounting substrate, wherein at least one of the package and the mounting substrate is the package and the mounting. A concave portion communicated to the outer surface of the package is provided in a region facing the substrate.

  Also, the present invention is the above surface-mount structure, wherein the package includes a terminal electrode in the surface, and the recess communicates with the outer surface along a side surface of the terminal electrode. Includes configured ones.

  Also, the present invention is the surface mounting structure, wherein the recess has a through hole that penetrates the package or the mounting substrate, and the side surface of the terminal electrode is formed by the through hole so that the side surface of the terminal electrode is the package or the mounting substrate. Includes one configured to communicate with the outer surface of the mounting board.

  Further, the present invention is a surface-mounted component in which a mounting region is in at least one surface of a package, the package includes a terminal electrode in the surface, and the package is provided between the terminal electrodes, Including one having a recess communicated to the outer surface of the package.

  Further, the present invention is the above surface-mounted component, wherein the recess surrounds at least a region of the side surface of the terminal electrode other than the outer surface of the package, and is configured to communicate with the outer surface. Including those that are

  Further, the present invention is the above-described surface mount component, wherein the recess has a through hole that penetrates the package, and the side surface of the terminal electrode communicates with the outer surface of the package through the through hole. Including those configured.

  Further, the present invention is the above surface mount component, wherein the surface mount component includes a plurality of terminal electrodes arranged to face and face the center of the bottom surface of the package, and the concave portion of the package It includes those formed so as to include the center or central axis of the bottom surface.

  Further, the present invention includes the surface mount component, wherein the surface mount component is an acceleration sensor.

Further, the present invention is a mounting substrate having a mounting area for mounting a surface mounting component,
The mounting area includes a number of lands at a position facing the bottom surface of the surface-mounted component,
A recess is formed between the lands.

  In addition, a recessed part means the part which has become low on the basis of the terminal electrode of a mounting component, or the land formation surface of a mounting board | substrate here.

  According to the surface mount structure of the present invention, since it has a groove or a through hole formed on the bottom surface of the mounting substrate or package, the vaporized gas is discharged to the outside through this groove during reflow, and the flux is Since it discharges | emits, the residue of a flux residue can be prevented.

The perspective view which shows the surface mount component of Embodiment 1 of this invention (A) and (b) are a top view and a bottom view of the surface mount component. (A) And (b) is AA sectional drawing and BB sectional drawing of FIG.2 (b). The perspective view which shows the state which mounted the surface mounting component of Embodiment 1 of this invention on the mounting board | substrate. (A) And (b) is a figure which shows the AA cross section and BB cross section of FIG. Diagram showing the mounting area of this printed wiring board The perspective view which shows the surface mount component of Embodiment 2 of this invention (A) and (b) are a top view and a bottom view of the surface mount component. (A) And (b) is AA sectional drawing and BB sectional drawing of FIG.8 (b). The perspective view which shows the state which mounted the surface mounting component of Embodiment 2 of this invention on the mounting board | substrate. (A) And (b) is a figure which shows the AA cross section and BB cross section of FIG. Diagram showing the mounting area of this mounting board The top view of the mounting board of Embodiment 3 of the present invention Sectional view of the mounting board Cross-sectional view of a mounting structure using the same mounting board The figure which shows the modification of Embodiment 1 of this invention, (a) is a top view, (b) is a bottom view. The figure which shows the modification of Embodiment 1 of this invention, (a) is AA sectional drawing of FIG.16 (b), (b) is BB sectional drawing of FIG.16 (b). The figure which shows the other modification of Embodiment 1 of this invention, (a) is AA sectional drawing of FIG.16 (b), (b) is equivalent to BB sectional drawing of FIG.16 (b). Cross-sectional view The figure which shows the further another modification of Embodiment 1 of this invention, (a) is a top view, (b) is a bottom view. The figure which shows the modification of Embodiment 1 of this invention, (a) is AA sectional drawing of (b), (b) is a bottom view. (A) and (b) are a top view and a bottom view of a conventional surface mount component. (A) And (b) is a figure which shows the AA sectional drawing and BB sectional drawing of FIG.21 (b). (A) And (b) is a figure which shows the mounting state of surface mount components Diagram showing the mounting board after reflow

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view showing a surface mounting component according to Embodiment 1 of the present invention, FIGS. 2A and 2B are a top view and a bottom view of the surface mounting component, and FIGS. 3A and 3B. These are AA sectional drawing and BB sectional drawing of FIG.2 (b). 4 is a perspective view showing a state in which the surface-mounted component 10 is mounted on a printed wiring board 20 as a mounting board, and FIGS. 5A and 5B are a cross-sectional view taken along line AA and BB in FIG. It is a figure which shows a cross section. FIG. 6 is a view showing a mounting area of the printed wiring board.

The surface mount component used in this surface mount structure is composed of ten 4 mm × 1.2 mm rectangular terminal electrodes 12 on the lower surface of the package 11 main body, that is, the mounting surface 11 a, with 7 rows and 2 columns at a distance of about 0.7 mm. 10 are arranged, and three groove-like recesses 13 are squeezed between the terminal electrodes arranged in two rows. That is, a groove-shaped recess 13 communicating with the outer surface of the opposing region is provided in the opposing region of the package 11 body and the printed wiring board 20. The outer surfaces of the opposing regions correspond to the outer surface of the package.
The groove width Wc ₁ between the terminal electrodes region width Wc ₂ at the 0.9mm are arranged at 0.4 mm × length 4 mm.
As shown in FIG. 6, the mounting area of the printed wiring board made of aluminum nitride, which is a mounting board, has 5 × 2 rectangular lands 22 corresponding to the terminal electrodes 12 of the surface mounting component 10.

  The surface mount component 10 is a 10-terminal surface mount component on which a sensor is mounted. Inside, a sensor chip for detecting a physical quantity (not shown) is housed, and ten flat terminal electrodes 12 are led out from a ceramic package 11 to a mounting surface 11a. The terminal electrode 12 is in one mounting surface 11a of the package 11 and does not protrude outward.

According to this configuration, the presence of the groove-shaped recess 13 forms a gap between the surface-mounted component 10 and the printed wiring board 20, and the solvent in the flux is efficiently derived during reflow, and the flux residue is removed. Does not remain. In addition, the height of the mounting body is not actually increased, and the thickness can be secured to reduce the residue.
In this way, the residue of flux residue is greatly reduced. Therefore, the connection is stably maintained. Since this sensor can be mounted with good flatness, the inclination angle on the circuit board (mounting board) can be well maintained even when used as an acceleration sensor.

(Embodiment 2)
7 is a perspective view showing a surface-mounted component according to Embodiment 2 of the present invention, FIGS. 8A and 8B are a top view and a bottom view of the surface-mounted component, and FIGS. 9A and 9B. These are AA sectional drawing and BB sectional drawing of FIG.8 (b). FIG. 10 is a perspective view showing a state in which the surface-mounted component 10 is mounted on a printed wiring board 20 which is a mounting board. FIGS. 11A and 11B are a cross-sectional view taken along line AA and BB in FIG. It is a figure which shows a cross section. FIG. 12 is a view showing a mounting area of the printed wiring board.

  The surface mount component used for this surface mount structure is characterized in that three through holes 14 are formed in the region between the terminal electrodes in the center of the package 11 instead of the recess of the first embodiment. . That is, the surface mount component includes a plurality of terminal electrodes 12 arranged so as to face and face the center of the bottom surface of the package, and the through hole 14 is formed so as to include the central axis of the bottom surface of the package 11. It is characterized by.

  Also in this example, ten 4 mm × 1.2 mm rectangular terminal electrodes 12 are arranged on the lower surface, that is, on the mounting surface 11a in five rows and two columns with an interval of about 0.7 mm. Then, three through holes 14 are squeezed between the terminal electrodes 12 arranged in two rows.

  As shown in FIG. 10, the mounting area of the printed wiring board which is the mounting board has a rectangular land 22 of 7 rows and 2 columns corresponding to the terminal electrodes 12 of the surface mounting component 10. Further, a substrate through hole 24 is also formed in the mounting region of the printed wiring board corresponding to the through hole 14 of the surface mount component 10.

  Again, this surface mount component 10 is a 10-terminal surface mount component on which a pressure sensor is mounted. A pressure sensor chip (not shown) is housed inside, and terminal electrodes 12 are led out from a resin package 11.

  According to this configuration, through-holes are formed in the surface-mounted component and the printed wiring board, and the flux can be efficiently led out to the outside through the through-holes so that no flux residue is generated.

(Embodiment 3)
13 to 15 are views showing a surface mounting structure of a surface mounting component according to the third embodiment of the present invention. 13 is a top view of the mounting substrate, FIG. 14 is a cross-sectional view of the mounting substrate, and FIG. 15 is a cross-sectional view of a mounting structure using the mounting substrate.

The printed wiring board 20 used for this surface mount structure is characterized in that a recess 25 is formed in a region where a surface mount component is mounted, and a thin portion 21 is formed. The presence of the thin portion 21 reduces the heat capacity and improves heat dissipation.
That is, the mounting substrate is formed by forming a recess 25 in the surface mounting mounting area and forming a land 22 in the recess 25. The depth of the recess 25 is preferably 0.2 mm or less.
Since other parts are formed in the same manner as in the first embodiment, description thereof is omitted here.

  Also in this example, the terminal electrode may include a plurality of terminal electrodes arranged to face the center of the bottom surface of the package and face each other, and the through hole 14 may be formed to include the central axis of the bottom surface of the package.

  According to this configuration, in addition to the effects of the first embodiment, since the concave portion is formed in the printed wiring board corresponding to the surface mounting component mounting region and is thin, the heat capacity is small, and in the solder reflow process, The temperature rises efficiently and the solder flux easily evaporates. Accordingly, the flux residue is reduced. Thus, by providing both the thin portion 21 and the through hole 14, the flux residue can be more efficiently reduced.

  In the above-described embodiment, the recesses and through holes are formed in the package. However, such recesses and through holes are formed by forming protrusions or forming protrusions in the sealing mold in the resin sealing process. By doing so, it can be easily formed without requiring any additional process.

  In addition, the present invention is particularly effective for a structure in which relatively low terminal electrodes are formed at a high density on the entire mounting surface of the surface mounting component. In particular, it is effective for a surface-mounted component in which terminal electrodes are formed at a high density with 30% or more, particularly 50% or more of the mounting surface as a bonding region. Further, the configuration of the terminal electrode or lead is not limited to the embodiment, and other terminals such as a structure in which the terminal electrode is led straight out from the side surface of the package and the package bottom surface is in close contact with the mounting substrate. Needless to say, the present invention can also be applied to surface mount components having a structure.

Next, a modified example of the present invention will be described.
The following is a modification of the first embodiment.
In the first embodiment, the concave portions are formed in both the surface-mounted component and the printed wiring board, but it goes without saying that either one is effective.
Further, the recess 13 may be continuously formed outward as shown in FIGS. 16 (a) and 16 (b) and FIGS. 17 (a) and 17 (b). .

In this case, as shown in FIGS. 18 (a) and 18 (b), it is desirable to form the recess 13 so that the depth of the recess 13 decreases as it goes outward.
With this configuration, the bottom surface of the recess 13 forms an inclined surface, so that the flux is discharged more efficiently.
Furthermore, in this case, the recess 13 may be formed in a cross shape as shown in FIGS. 19A and 19B.

  16A and 16B are a top view and a bottom view of the surface-mounted component, and FIGS. 17A and 17B are cross-sectional views taken along line AA and BB in FIG. 16B. It is sectional drawing. 18 (a) and 18 (b) are diagrams showing a cross section cut along the same plane as that of FIGS. 17 (a) and 17 (b), and FIGS. 19 (a) and 19 (b) are views of the surface mount component of the modification. It is a top view and a bottom view.

  Furthermore, as shown in FIGS. 20A and 20B, a recess 13 may be formed on the mounting surface of the surface mount component so as to surround the terminal electrode 12. FIG. 20A is a cross-sectional view taken along the line AA in FIG. That is, the recess 13 may be formed so as to surround a region other than the outer surface of the package among the side surfaces of the terminal electrode 12 and communicate with the outer surface of the package. As a result, the flux flows along the groove and is efficiently discharged to the outside. The recess 13 is preferably formed so as to reach the side surface from the mounting surface.

Moreover, in the said embodiment, although the aluminum nitride ceramics with favorable heat dissipation were comprised as an insulating base | substrate which comprises a printed wiring board, it is not limited to this. For example, various substrate materials such as a laminated substrate using a green sheet and a resin-made three-dimensional substrate in which concave portions and through holes are formed by injection molding can be applied.
For example, it may be formed as a green sheet using a ceramic dielectric material LTCC (Low Temperature Co-fired Ceramics) that can be sintered at a low temperature of 1000 ° C. or lower. That is, a predetermined pattern is formed by printing a low-resistivity conductive paste such as Ag or Cu on this LTCC green sheet having a thickness of 10 μm to 200 μm. Then, using the plurality of green sheets as an insulating layer, they are laminated integrally as appropriate, and sintered in a state where a recess or a through hole is formed. Thereby, it can manufacture as an insulating layer (dielectric layer) provided with the recessed part or the through-hole, and the internal conductor layer. As these dielectric materials, for example, Al, Si, Sr as a main component, Ti, Bi, Cu, Mn, Na, K as subcomponents, Al, Mg, Si, Gd-containing materials, Al, A material containing Si, Zr, or Mg is applicable.

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, this ceramic substrate may be formed using HTCC (High Temperature Co-fired Ceramics) technology. On this HTCC ceramic substrate, the dielectric material may be composed mainly of Al ₂ O ₃ and the transmission line may be constructed as a metal conductor that can be sintered at a high temperature such as tungsten or molybdenum as the internal conductor layer. good.

  In addition to ceramic, the insulating substrate can be applied to a resin substrate such as a glass epoxy resin, a polyimide resin, a polyester resin, and a polyethylene terephthalate resin, a laminated substrate using a prepreg, and the like.

  Furthermore, the configuration and material of the circuit unit can be changed as appropriate.

  As mentioned above, although embodiment which applied the invention made by the present inventors was described, this invention is not limited by description and drawing which make a part of indication of this invention by this embodiment. That is, it is needless to say that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above-described embodiments are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Surface mount component 11 Package 12 Terminal electrode 13 Recess 14 Through hole 20 Printed wiring board 21 Thin part 22 Land 24 Substrate through hole 25 Recess

Claims (9)

A surface mounting structure in which a surface mounting component having a mounting area on at least one surface of a package is mounted on a mounting board,
A mounting structure in which at least one of the package and the mounting substrate has a recess communicated to the outer surface of the package in a region where the package and the mounting substrate face each other. The mounting structure according to claim 1,
The package includes a terminal electrode in the plane,
The recess is a mounting structure configured to communicate with the outer surface along a side surface of the terminal electrode. The mounting structure according to claim 2,
The recess has a through hole that penetrates the package or the mounting substrate, and the mounting structure is configured such that a side surface of the terminal electrode communicates with an outer surface of the package or the mounting substrate through the through hole. . A surface mount component whose mounting area is in at least one surface of the package,
The package includes a terminal electrode in the plane,
The package is a surface-mounted component having a recess communicated between the terminal electrodes to the outer surface of the package. The surface mount component according to claim 4,
The concave portion is a surface-mounted component that is a groove configured to surround at least a region of the side surface of the terminal electrode other than the outer surface of the package and communicate with the outer surface. The surface mount component according to claim 4,
The concave portion has a through hole that penetrates the package, and the side surface of the terminal electrode is configured to communicate with the outer surface of the package through the through hole. The surface mount component according to any one of claims 4 to 6,
The surface mount component comprises a plurality of terminal electrodes arranged to face and face the center of the bottom surface of the package,
The surface-mount component formed so that the concave portion includes a center or a central axis of a bottom surface of the package. The surface mount component according to any one of claims 4 to 6,
The surface mount component is a surface mount component which is an acceleration sensor. A mounting board having a mounting area for mounting surface-mounted components,
The mounting area includes a number of lands at a position facing the bottom surface of the surface-mounted component,
A mounting substrate in which a recess is formed between the lands.

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