JP2015144205A - Electronic apparatus, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic apparatus capable of securing a required stand-off height without causing a packaging defect, and to provide a manufacturing method thereof.SOLUTION: At least a part of a non-connection land 24 that is not connected to a lead terminal 32, is disposed within an opposing area 21a of a packaging surface 21, and on the non-connection land 24, a height adjusting solder 42 is provided in contact with a bottom face 31a of a main body part 31 in a semiconductor device 30. The height adjusting solder 42 is brought into contact with the bottom face 31a of the main body part 31 so as to push up the bottom face 31a by fusing solder paste 40 that is partially disposed on a solder resist 22, during reflow processing, collecting and forming the solder paste 40 on the non-connection part 24 so as to be protruded by a surface tension.

Description

  The present invention relates to an electronic device in which terminals of an electronic component are solder-connected to a land of a circuit board, and a manufacturing method thereof.

  Generally, in a circuit board on which electronic components are mounted, solder is used for electrical connection between terminals of the electronic components and lands on the substrate surface. As an important factor related to the thermal fatigue life of the solder connection portion, the standoff height which is the height from the land to the lower surface of the electronic component main body is known. By increasing the standoff height and the solder thickness of the connection portion, the thermal fatigue life of the solder connection portion is improved. This is because the shear strain generated in the solder connection portion due to thermal stress is reduced by increasing the height of the connection portion, and the strain is absorbed by the softness of the solder.

  As a technique related to an electronic device that secures a necessary standoff height, a power semiconductor device disclosed in Patent Document 1 below is known. In this semiconductor device, a plurality of protrusions are formed on a metal plate of a metal substrate on which the packaged power semiconductor is mounted, and each protrusion contacts the lower surface of the packaged power semiconductor so that the metal substrate and The thickness of the solder connecting the package type power semiconductor is constant over the entire joint surface.

JP 2011-181787 A

  However, as disclosed in the above-mentioned Patent Document 1, in the configuration in which each protrusion provided on the substrate surface is brought into contact with the lower surface of the main body of the electronic component to ensure the necessary standoff height, the following problems are caused. Occurs. That is, the distance between the circuit board and the electronic component tends to be larger when the electronic component is mounted after the solder paste is printed, and the amount of contact between the terminal of the electronic component and the solder paste, compared to the case where each of the protrusions is not provided. Will become smaller. Furthermore, due to the above-described protrusions, the sinking of the terminals due to the weight of the electronic component during the reflow process is hindered. Then, depending on the coplanarity of each terminal of the electronic component and the variation of the solder printing amount of the solder paste, there is a problem that the terminal is not in contact with the solder or a mounting failure with a small contact amount is likely to occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electronic device that can secure a necessary stand-off height without causing a mounting failure, and a manufacturing method thereof. There is.

In order to achieve the above object, according to the first aspect of the present invention, the terminal (32) of the electronic component (30, 30a) is a land (21) provided on the mounting surface (21) of the circuit board (20). 23) An electronic device (10) which is solder-connected to the mounting surface and is provided with a protective layer (22) having lower solder wettability than the exposed land on the mounting surface, and the substrate of the main body (31) in the electronic component At least a part of the unconnected land (24) not connected to the terminal is disposed in the facing region (21a) of the mounting surface facing the side surface (31a), and contacts the side surface of the substrate on the unconnected land. Solder (42) is provided, and the solder paste (40) at least partially disposed on the protective layer melts during reflow processing and collects on the unconnected land due to surface tension. By being formed as rise, characterized by contacting as push to the substrate side.
In addition, the code | symbol in the parenthesis of a claim and the said means shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  According to the first aspect of the present invention, at least a part of the unconnected land is disposed in the facing region of the mounting surface, and solder that contacts the side surface of the substrate is provided on the unconnected land. This solder is formed so that the solder paste, at least a part of which is disposed on the protective layer, melts during reflow processing and gathers and rises on the unconnected land due to surface tension. To touch.

  As a result, when the electronic component is mounted after the solder paste is arranged by printing or the like, the force that pushes up the main body of the electronic component does not act, so the coplanarity of each terminal of the electronic component and the solder print amount of the solder paste The terminals of the electronic component and the solder paste can be reliably brought into contact without being affected by variations. During the reflow process, the melted solder is formed so as to gather and rise on the unconnected land due to surface tension, so that the solder contacts the side surface of the electronic component main body so as to push up. The electronic component is pushed up by the agglomerated solder. In this way, the pushing force that did not occur before the reflow process acts on the electronic component during the reflow process, so that the necessary standoff height and solder thickness can be ensured without causing mounting defects.

It is sectional drawing which shows schematic structure of the electronic device which concerns on 1st Embodiment. It is a top view which shows the circuit board of FIG. FIG. 3 is an enlarged top view showing the vicinity of the semiconductor device of FIG. 2. It is sectional drawing by the cut surface equivalent to the XX line of FIG. It is explanatory drawing which shows the positional relationship of the opposing area | region of a mounting surface, and each unconnected land. It is explanatory drawing for demonstrating the manufacturing process which mounts a semiconductor device on a circuit board. It is explanatory drawing for demonstrating the state by which a semiconductor device is pushed up with the solder for height adjustment condensed on the unconnected land. It is sectional drawing which shows the principal part of the electronic device which concerns on the 1st modification of this embodiment. It is explanatory drawing which shows the positional relationship of the opposing area | region of the mounting surface in the 1st modification, and the solder paste aggregated in an unconnected land. It is sectional drawing which shows the principal part of the electronic device which concerns on the 2nd modification of this embodiment. It is explanatory drawing which shows the principal part of the electronic device which concerns on the 3rd modification of this embodiment. It is explanatory drawing which shows the principal part of the electronic device which concerns on the 4th modification of this embodiment.

[First Embodiment]
A first embodiment that embodies an electronic device and a manufacturing method thereof according to the present invention will be described below with reference to the drawings.
The electronic device 10 shown in FIG. 1 is employed in an environment where the temperature change is large, and is configured as an electronic control unit (Electronic Control Unit) that controls in-vehicle equipment such as an engine mounted on the vehicle, for example. . The electronic device 10 is configured by housing a circuit board 20, another board, and the like in a housing 11. As shown in FIGS. 1 and 2, electronic components such as a semiconductor device 30 and an external connector 12 are mounted on the mounting surface 21 of the circuit board 20.

  Next, the mounting state of the semiconductor device 30 will be described in detail with reference to FIGS. FIG. 3 is an enlarged top view showing the vicinity of the semiconductor device 30 of FIG. 4 is a cross-sectional view taken along the line XX in FIG. FIG. 5 is an explanatory diagram showing the positional relationship between the facing region 21 a of the mounting surface 21 and each unconnected land 24. In FIG. 5, the semiconductor device 30 and each land 23 are not shown for convenience.

  As shown in FIGS. 3 and 4, the semiconductor device 30 is a QFP (Quad Flat Package) type semiconductor package, and includes a main body portion 31 in which a semiconductor element such as an IC chip is sealed by a sealing member, and an inner lead. A plurality of lead terminals 32 led out from each side surface of the main body 31 are provided so that the portion is sealed together with the semiconductor element by a sealing member.

  A solder resist 22 is provided as a protective layer on the mounting surface 21 of the circuit board 20, and a plurality of lands 23 electrically connected to the lead terminals 32 of the semiconductor device 30 are exposed from the solder resist 22. Is arranged. The solder resist 22 is an insulating film having lower solder wettability than each land 23 and an unconnected land 24 described later. The semiconductor device 30 is electrically connected to the circuit board 20 by solder connection via the corresponding land 23 and solder 41 at each lead terminal 32.

  As shown in FIGS. 4 and 5, the mounting surface 21 has a rectangular shape that is not connected to the lead terminal 32 at the four corners of a substantially rectangular facing region 21 a that faces the lower surface 31 a that is the side surface of the body 31. Connection lands 24 are respectively provided so as to be exposed from the solder resist 22. Each unconnected land 24 functions as a height control land for controlling the height of a height adjusting solder 42 to be described later. A portion in the facing area 21a is opposed to the facing area 21a. It arrange | positions so that it may become wider than an outer part.

  On each unconnected land 24, solder that contacts the lower surface 31a of the main body 31 (hereinafter also referred to as height adjusting solder 42) is provided. This height adjusting solder 42 functions to secure the necessary standoff height and solder thickness by pushing up the four corners of the lower surface 31a during reflow processing, as will be described later, and is the same material as the solder 41. It is comprised by.

  Next, a manufacturing process for mounting the semiconductor device 30 on the circuit board 20 as a part of the manufacturing method of the electronic device 10 will be described in detail with reference to FIGS. 6 and 7. FIG. 6 is an explanatory diagram for explaining a manufacturing process for mounting the semiconductor device 30 on the circuit board 20. FIG. 7 is an explanatory diagram for explaining a state in which the semiconductor device 30 is pushed up by the height adjusting solder 42 aggregated on the unconnected land 24.

  First, as shown in FIG. 6A, a circuit board 20 is prepared so that each land 23 and each unconnected land 24 are exposed from a solder resist 22 provided on the mounting surface 21. Next, the solder paste 40 containing the flux is added to each land 23 and is disposed at a position where it melts during reflow processing and gathers on the unconnected land 24 due to surface tension.

  Specifically, as shown in FIG. 6B, the solder paste 40 is partially covered with the unconnected land 24 and the remaining portion is covered with the solder resist 22, and outside the opposed region 21 a than the unconnected land 24. It arrange | positions using mask printing etc. so that it may become a large surface area. Further, the solder paste 40 provided on the land 23 is arranged so as to protrude to the solder resist 22.

  Next, as shown in FIG. 6C, the semiconductor device 30 is mounted (mounted) on the circuit board 20 so that each lead terminal 32 is brought into contact with the solder paste 40 on the corresponding land 23. At this time, the solder paste 40 covering a part of the unconnected land 24 is not in contact with the lower surface 31a of the main body 31 because it is disposed outside the facing region 21a.

  Subsequently, a reflow process is performed in which the circuit board 20 on which the semiconductor device 30 is mounted is heated in a reflow furnace as described above. As a result, the solder paste 40 covering the lands 23 and the unconnected lands 24 is heated. At this time, as shown in FIG. 7A, the remaining part of the solder paste 40 partially covering the unconnected land 24 covers the solder resist 22 having low solder wettability. (Hereinafter, also referred to as a molten solder 40a) aggregates so as to avoid the solder resist 22 on the surface tension. Accordingly, as shown in FIG. 7B, the molten solder 40a moves so as to spread out on the unconnected land 24 having higher solder wettability than the solder resist 22 so as to leave a part of the flux 40b. To do.

  Since the solder paste 40 to be agglomerated on the unconnected lands 24 is arranged to have a larger surface area than the unconnected lands 24, the molten solder 40a is formed on the unconnected lands 24 as shown in FIG. Gathers together and comes into contact with the lower surface 31a of the main body 31 so as to be pushed up.

  As the molten solder 40a in contact with the lower surface 31a solidifies in this way, as shown in FIG. 6D, a height adjusting solder 42 for lifting the semiconductor device 30 from below is formed. Since the main body 31 is lifted as described above, each lead terminal 32 is also lifted in contact with the molten solder, and the molten solder that has wetted the lead terminal 32 is solidified, so that the necessary standoff height is increased. Solder 41 having a solder thickness that can ensure the thickness is formed.

  As described above, in the electronic device 10 according to the present embodiment, at least a part of the unconnected land 24 that is not connected to the lead terminal 32 is disposed in the facing region 21 a of the mounting surface 21, and on the unconnected land 24. A height adjusting solder 42 that contacts the lower surface 31a of the main body 31 in the semiconductor device 30 is provided. This solder 42 for height adjustment is formed so that a part of the solder paste 40 disposed on the solder resist 22 melts during reflow processing and gathers on the unconnected land 24 due to surface tension. It comes into contact with the lower surface 31a of the main body 31 so as to push it up.

  In the method for manufacturing the electronic device 10 according to the present embodiment, at least one of the unconnected lands 24 that are not connected to the lead terminal 32 in the facing region 21 a of the mounting surface 21 that faces the lower surface 31 a of the main body 31 in the semiconductor device 30. The circuit board 20 on which the portion is arranged is prepared (first step), and the solder paste 40 is added to the land 23 and melted during the reflow process, and is arranged on the unconnected land 24 by the surface tension to rise. (Second step) The semiconductor device 30 is mounted on the circuit board 20 so that the lead terminals 32 are brought into contact with the solder paste 40 on the lands 23 (third step), and collected on the unconnected lands 24 by reflow treatment. The upper surface 31a of the main body 31 is pushed up by the height-adjusting solder 42, and the lead terminal 32 and the land 23 are soldered. Connecting (fourth step).

  Thereby, when the semiconductor device 30 is mounted after the solder paste 40 is arranged by printing or the like, a force that pushes up the main body portion 31 of the semiconductor device 30 does not act, so the coplanarity of each lead terminal 32 of the semiconductor device 30 The lead terminal 32 and the solder paste 40 can be reliably brought into contact with each other without being affected by variations in the amount of solder printing of the solder paste 40. During the reflow process, the molten solder 40a is brought into contact with the lower surface 31a of the main body 31 of the semiconductor device 30 in a state where the molten solder 40a is gathered and raised on the unconnected land 24 due to surface tension. The electronic component is pushed up by the molten solder 40 a aggregated on the connection land 24. In this way, the pushing force that did not occur before the reflow process acts on the semiconductor device 30 during the reflow process, so that the necessary standoff height and solder thickness can be ensured without causing mounting defects.

  In particular, since the solder paste 40 to be agglomerated on the unconnected lands 24 is arranged to have a larger surface area than the unconnected lands 24, the molten solder 40 a that has gathered and swelled on the unconnected lands 24 is the solder paste 40. Therefore, the semiconductor device 30 can be reliably pushed up. That is, the standoff height and the solder thickness can be adjusted according to the amount of the solder paste 40 applied.

  Further, in the same way as a normal SMD (surface mounted device) mounting method, the unconnected land 24 and the printing of the solder paste 40 that aggregates on the unconnected land 24 generate a pushing force during the reflow process. Therefore, there is no need to provide protrusions and the like, and there is no adverse effect on printing stability using a metal mask or the like. In addition, since it is not necessary to provide the mounting surface 21 with a projection or the like, an increase in manufacturing cost due to the adoption of the present invention can be suppressed.

  The push-up forces by the respective height adjusting solders 42 act on the four corners of the lower surface 31a, so that the semiconductor device 30 can be prevented from being pushed up so as to be inclined with respect to the mounting surface 21.

  Further, since the solder paste 40 to be agglomerated on the unconnected lands 24 is arranged so that at least a part thereof covers the unconnected lands 24, the molten solder 40 a has a higher solder wettability than the surrounding solder resist 22. The molten solder 40 a can be easily collected on the unconnected land 24 because it flows out from the overlapping portion with the connected land 24 toward the unconnected land 24.

  Furthermore, since the solder paste 40 to be agglomerated on the unconnected lands 24 is disposed outside the facing region 21a, even in the semiconductor device 30 in which the distance from the mounting surface 21 to the lower surface 31a of the main body 31 is shortened, It can prevent that the solder paste 40 before a reflow process contacts the main-body part 31. FIG.

  The solder paste 40 provided on the lands 23 to be soldered to the lead terminals 32 is arranged so as to protrude onto the solder resist 22. For this reason, the amount of molten solder that wets the lead terminals 32 is increased as compared with the case where the solder paste 40 is disposed so as not to protrude onto the solder resist 22, so that the semiconductor device 30 is pushed up as described above. Even if it is possible, the lead terminal 32 and the corresponding land 23 can be reliably soldered.

  FIG. 8 is a cross-sectional view illustrating a main part of an electronic device according to a first modification of the present embodiment. FIG. 9 is an explanatory diagram showing the positional relationship between the opposing region 21 a of the mounting surface 21 and the solder paste 40 that is aggregated on the unconnected lands 24 in the first modification. In FIG. 9, illustration of the semiconductor device 30, each land 23, and the like is omitted for the sake of convenience, and the solder paste 40 is illustrated by broken lines.

  As a first modification of the present embodiment, when the semiconductor device 30 having a relatively long distance from the mounting surface 21 to the lower surface 31a of the main body 31 is solder-connected to the circuit board 20, it is aggregated into the unconnected lands 24. The solder paste 40 may be disposed in the facing region 21a. Specifically, as illustrated in FIG. 8 and FIG. 9, the solder paste 40 to be aggregated on the unconnected land 24 is covered with the outer portion of the unconnected land 24, and the inner portion is wider. Can be arranged in a trapezoidal shape. As a result, even if the area occupied by the solder paste 40 is increased, the mounting area outside the opposing region 21a is not affected. Therefore, it is possible to prevent the mounting area from being reduced by arranging the solder paste 40 to be aggregated on the unconnected lands 24. it can.

FIG. 10 is a cross-sectional view illustrating a main part of an electronic device according to a second modification of the present embodiment. FIG. 10A illustrates a state before the reflow process in which the semiconductor device 30 is mounted on the circuit board 20. FIG. 10B shows a state after the reflow process.
As a second modification of the present embodiment, the solder paste 40 to be agglomerated on the unconnected lands 24, as illustrated in FIG. 10A, removes all of the unconnected lands 24 exposed from the solder resist 22 from the surrounding solder resist. It may be arranged so as to cover 22. Thus, as can be seen from FIG. 10 (B), the amount of wet spread of the solder paste 40 can be reduced. Aggregation on the connection land 24 can be facilitated.

In addition, this invention is not limited to the said embodiment, For example, you may actualize as follows.
(1) FIG. 11 is an explanatory diagram showing a main part of an electronic device according to a third modification of the present embodiment. FIG. 12 is an explanatory diagram illustrating a main part of an electronic device according to a fourth modification of the present embodiment.
The characteristic configuration of the present invention is not limited to being applied to the electronic device 10 in which the QFP type semiconductor package is solder-connected to the land 23 provided on the mounting surface 21 of the circuit board 20, for example, SOP (Small Outline Package). The present invention can be applied to an electronic device in which terminals of electronic components are solder-connected to lands 23 of the circuit board 20 such as a semiconductor package).

  For example, as illustrated in FIG. 11, when an SOP type semiconductor package is employed as the semiconductor device (electronic component) 30a, a plurality of locations on the mounting surface 21 that are symmetric with respect to two sides where the lead terminals 32 are not provided. Further, an unconnected land 24 for forming the height adjusting solder 42 can be disposed. Further, as illustrated in FIG. 12, an unconnected land 24 for forming a wide height adjusting solder 42 is disposed at a location on the mounting surface 21 that is symmetrical with respect to two sides where the lead terminal 32 is not present. You can also. Thereby, since the amount of solder constituting the height adjusting solder 42 can be increased, the pushing force of the main body 31 by the height adjusting solder 42 can be increased.

(2) The unconnected land 24 exposed from the solder resist 22 is not limited to being formed in a rectangular shape or a trapezoidal shape, and may be formed in, for example, a circular shape or the like in accordance with the surrounding mounting state.

(3) The unconnected land 24 is not limited to be arranged so that the portion in the facing region 21a is wider than the portion outside the facing region 21a with respect to the facing region 21a. The part outside the facing area 21a may be arranged so as to be wider than the part inside the facing area 21a, or all the parts may be arranged inside the facing area 21a.

DESCRIPTION OF SYMBOLS 10 ... Electronic device 21 ... Mounting surface 21a ... Opposite area | region 22 ... Solder resist (protective layer)
23 ... Land 24 ... Unconnected land 30, 30a ... Semiconductor device (electronic component)
31 ... Body 31a ... Lower surface (side surface of substrate)
32 ... Lead terminal 40 ... Solder paste 41 ... Solder 42 ... Solder for height adjustment

Claims (10)

The terminals (32) of the electronic components (30, 30a) are soldered to lands (23) provided on the mounting surface (21) of the circuit board (20), and the soldering wettability is higher than the exposed lands on the mounting surface. An electronic device (10) provided with a low protective layer (22),
At least a part of the unconnected land (24) not connected to the terminal is disposed in the facing region (21a) of the mounting surface facing the substrate side surface (31a) of the main body (31) in the electronic component,
Solder (42) that contacts the side surface of the substrate is provided on the unconnected land,
The solder is formed so that the solder paste (40) at least partially disposed on the protective layer melts during reflow processing and gathers and rises on the unconnected land due to surface tension. An electronic device which is brought into contact with the side surface so as to be pushed up.   The electronic device according to claim 1, wherein at least a part of the solder paste is disposed on the unconnected land.   The electronic device according to claim 2, wherein the solder paste is disposed outside the facing region.   The electronic device according to claim 2, wherein the solder paste is disposed in the facing region.   5. The electronic device according to claim 1, wherein the solder paste provided on the land to be soldered to the terminal is disposed so as to protrude onto the protective layer. 6. The terminals (32) of the electronic components (30, 30a) are soldered to lands (23) provided on the mounting surface (21) of the circuit board (20), and the soldering wettability is higher than the exposed lands on the mounting surface. A method of manufacturing an electronic device (10) provided with a low protective layer (22), comprising:
The circuit in which at least a part of an unconnected land (24) not connected to the terminal is disposed in a facing region (21a) of the mounting surface facing the substrate side surface (31a) of the main body (31) in the electronic component. A first step of preparing a substrate;
A second step of adding the solder paste (40) onto the land, and melting and reflowing the solder paste (40) on the unconnected land due to surface tension;
A third step of mounting the electronic component on the circuit board so that the terminal contacts the solder paste on the land;
A fourth step of pushing up the side surface of the substrate by the solder (42) gathered on the unconnected land by reflow treatment and solder-connecting the terminal and the land;
An electronic device manufacturing method comprising:   The method of manufacturing an electronic device according to claim 6, wherein in the second step, at least a part of the solder paste is disposed on the unconnected land.   8. The method of manufacturing an electronic device according to claim 7, wherein, in the second step, the solder paste is disposed outside the facing region.   8. The method of manufacturing an electronic device according to claim 7, wherein in the second step, the solder paste is disposed in the facing region.   The solder paste disposed on the land that is solder-connected to the terminal in the second step is disposed so as to protrude onto the protective layer. The manufacturing method of the electronic device as described in any one of.

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