Semiconductor device for improving heat dissipation and mounting structure thereof

A semiconductor device includes a semiconductor element, a first lead (1), a plurality of second leads and a sealing resin. The first lead includes a mounting portion mounting the semiconductor element, four connecting portions extending from four corners of the mounting portion, respectively, and four first terminal portions connected to front ends of the connecting portions, respectively. A part of each first terminal portion is exposed from the sealing resin. The second leads are arranged in a plural quantity between adjacent first terminal portions when viewed in a thickness direction. Each second lead includes a second terminal portion having a part exposed from the sealing resin, and a joining portion extending from the second terminal portion toward the mounting portion. A connecting portion width dimension of the connecting portion is greater than a joining portion width dimension of the joining portion of the second lead adjacent to the connecting portion.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device and a mounting structure of the semiconductor device.

DESCRIPTION OF THE PRIOR ART

Semiconductor devices in quad flat non-leaded (QFN) packages have been developed as surface-mounted semiconductor devices on wiring substrates. Patent publication 1 discloses an example of a QFN semiconductor device. In a QFN semiconductor device, a plurality of electrode pads are disposed along four side surfaces, respectively. Further, a semiconductor device having a heat sink for releasing heat emitted from a semiconductor element is disposed on a back surface of the QFN semiconductor device.

FIG.17shows a bottom view of such conventional semiconductor device A100. The semiconductor device A100exposes, from the back surface of the sealing resin5, a first lead mounted with a semiconductor device. When the semiconductor device A100is mounted on a wiring substrate, the back surface of the first lead1is connected to a heat sink land of the wiring substrate. Accordingly, heat emitted by the semiconductor element is transmitted through the first lead1to the heat sink land and is released.

Further, electrode pads that expose a plurality of second leads2from the back surface of the sealing resin5are disposed on the bottom surface of the semiconductor device A100, wherein each of the second leads2is connected to a semiconductor element3via a bonding wire4. The plurality of electrodes pads are arranged side-by-side in a plural quantity along each of the four side surfaces. When the semiconductor device A100is mounted on the wiring substrate, the electrode pads are connected to the electrode pad lands of the wiring substrate, respectively. Accordingly, the electrode pad lands are arranged around the heat sink land. Thus, it would be difficult to expand the heat sink land on the surface of the wiring substrate, or to arrange wires for connecting the electrode pad lands around the heat sink land to the heat sink land. That is to say, it would be difficult to expand the heat dissipation area on the surface of the wiring substrate, in a way that an area sufficient for thorough heat dissipation cannot be ensured on the surface of the wiring substrate.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Present Invention

The present invention is conceived of on the basis of the foregoing situations, and aims to provide a semiconductor device that ensures a heat dissipation area on the surface of a mounted wiring substrate.

Technical Means for Solving the Problems

The present invention provides a semiconductor device, including: a semiconductor element; a first lead, being rectangular in shape when viewed in a thickness direction, including a mounting portion, four connecting portions and four first terminal portions, wherein the semiconductor element is mounted on the mounting portion, the connecting portions extend from four corners of the mounting portion, respectively, and the first terminal portions are connected to front ends of the plurality of connecting portions respectively; a plurality of second leads, arranged in a plural quantity in parallel to each edge of the mounting portion between the adjacent first terminal when viewed in the thickness direction; and a sealing resin, covering at least a part of each of the first lead and the second leads. A part of each of the first terminal portions is exposed from the sealing resin. Each of the second leads includes a second terminal portion having a part exposed from the sealing resin, and a joining portion extending from the second terminal portion toward the mounting portion. A dimension of a connecting portion width of the connecting portion is greater than a dimension of a joining portion width of the joining portion of the second lead adjacent to the connecting portion, wherein the dimension of the connecting portion width is a dimension in a direction perpendicular to the extension direction of the connecting portion and the thickness direction, and the dimension of the joining portion width is a dimension in a direction perpendicular to the extension direction of the joining portion and the thickness direction.

Effects of the Present Invention

According to the present invention, the mounting portion mounted with the semiconductor element is connected to the first terminal portions by the connecting portions having a larger width dimension. Because a part of each first terminal portion is exposed from the sealing resin, the exposed parts of the first terminal portions may be connected to the lands on the wiring substrate when the semiconductor device is mounted on the wiring substrate. Thus, the semiconductor device of the present invention is capable of release heat emitted by the semiconductor device to the lands connected to first terminal portions on the wiring substrate via the connection portion. The lands connected to the first terminal portions may be expanded to a region closer to an outer side than a region surrounded by the lands connected to the second leads. Therefore, the semiconductor device of the present invention ensures the heat dissipation area on the surface of the mounted wiring substrate.

Other features and advantages of the present invention are to become more apparent with the details given with the accompanying drawings below.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Specific details of the present invention are given in the preferred embodiments with the accompanying drawings below.

First Embodiment

A semiconductor device A1according to the first embodiment of the present invention is described with reference toFIG.1toFIG.6. The semiconductor device A1includes a first lead1, second leads2, a semiconductor element3, bonding wires4and a sealing resin5. The semiconductor device A1is in a so-called quad flat non-leaded (QFN) package.

FIG.1shows a top view of the semiconductor device A1.FIG.2shows a top view of a main part of the semiconductor device A1.FIG.3shows a bottom view of the semiconductor device A1.FIG.4shows a section diagram ofFIG.1along the line IV-IV.FIG.5shows a section diagram ofFIG.1along the line V-V.FIG.6shows an enlarged top view of the main part. InFIG.2andFIG.6, for better understanding, an imaginary line (double-dotted line) is used for the sealing resin5to indicate the contour of the sealing resin5.

The semiconductor device A1in these drawings is a device that is surface mounted on a wiring substrate of various apparatuses. When viewed in the thickness direction, the semiconductor device A1is rectangular in shape. For illustration purposes, the thickness direction of the semiconductor device A1is set as a z direction, a direction along one side of the semiconductor device A1(left-right direction inFIG.1) and perpendicular to the z direction is set as an x direction, and a direction perpendicular to the z direction and the x direction (top-down direction inFIG.1) is set as a y direction. The dimensions of the semiconductor device A1are not specifically defined. In this embodiment, for example, the dimension of the semiconductor device A1in the x direction is approximately 2 to 10 mm, the dimension in the y direction is approximately 2 to 10 mm, and the dimension in the z direction is 0.5 to 2 mm.

The first lead1and the second leads2contain metal, and preferably contain any one of Cu and Ni, an alloy thereof or a 42 alloy. In this embodiment, an example of the first lead1and the second leads2containing Cu is described. Each of the first lead1and the second leads2has a thickness of, for example, 0.08 to 0.5 mm, and approximately 0.125 mm in this embodiment. The first lead1and the second leads2are formed by, for example, etching processing of a metal plate. Further, the first lead1and the second leads2may also be formed by implementing punching processing or bending processing on a metal plate.

As shown inFIG.2, when viewed in the z direction, the first lead1is disposed at the center of the semiconductor device A1, and extends to two end portions of the semiconductor device A1in the x direction and the y direction. The first lead1supports the semiconductor element3and dissipates heat emitted by the semiconductor element3. Further, the first lead1may also be electrically connected to the semiconductor element3. The first lead1includes a mounting portion110, four first terminal portions120and four connecting portions130.

The mounting portion110is located at the center of the first lead1when viewed in the z direction, and is substantially rectangular in shaped when viewed in the z direction. When viewed in the z direction, the sides of the mounting portion110are parallel to the x direction or the y direction. The mounting portion110has a mounting portion main surface111and a mounting portion back surface112. The mounting portion main surface111and the mounting portion back surface112face opposite sides in the z direction. The mounting portion main surface111is a surface facing the top inFIG.4andFIG.5. The mounting portion main surface111is a surface mounted with the semiconductor element3. The mounting portion back surface112is a surface facing the bottom inFIG.4andFIG.5. The mounting portion back surface112is exposed from the sealing resin5, and becomes a back surface terminal. In this embodiment, the mounting portion main surface111is larger than the mounting portion back surface112. Further, the mounting portion main surface111and the mounting portion back surface112may also be equally sized.

The first terminal portions120are disposed on four corners of the semiconductor device A1, respectively, when viewed in the z direction. Each first terminal portion120is rectangular in shape when viewed in the z direction. Each first terminal portion120has a first terminal portion main surface121, a first terminal portion back surface122and two first terminal portion end surfaces123. The first terminal portion main surface121and the first terminal portion back surface122face opposite directions in the z direction. The first terminal portion main surface121is surface facing the top inFIG.4andFIG.5. The first terminal portion back surface122is a surface facing the bottom inFIG.4andFIG.5. The first terminal portion end surfaces123are surfaces connecting the first terminal portion main surface121and the first terminal portion back surface122, and are perpendicular to the first terminal portion main surface121and the first terminal portion back surface122. One of the first terminal portion end surfaces123faces an outer side in the x direction, and the other first terminal portion end surface123faces an outer side in the y direction. The first terminal portion back surface122and the two first terminal portion end surfaces123are individually exposed from the sealing resin5and are connected to one another to become terminals (referring toFIG.5).

Each connecting portion130is connected to the mounting portion110and the respective first terminal portion120. The connecting portions130extend radially from the four corners of the mounting portion110at the center of the semiconductor device A1, respectively, when viewed in the z direction, and are connected to the respective first terminal portions120disposed on the four corners of the semiconductor device A1. The connecting portions130have a thickness (the dimension in the z direction) of approximately one-half of the thickness of the mounting portion110. The connecting portions130are formed by, for example, half-etching processing. Each connecting portion130has a connecting portion main surface131and a connecting portion back surface132. The connecting portion main surface131and the connecting portion back surface132face opposite sides in the z direction. The connecting portion main surface131is a surface facing the top inFIG.4andFIG.5. The connecting portion main surfaces131, the mounting portion main surface111and the first terminal portion main surfaces121are an integral surface (referring toFIG.2andFIG.5) of a same plane. The connecting portion back surface132is a surface facing the bottom inFIG.4andFIG.5.

A surface coating layer (not shown) is formed on all parts of the first lead1that are exposed from the sealing layer5. In this embodiment, a surface coating layer is formed on the mounting portion back surface112, the first terminal portion back surfaces122and the first terminal portion end surfaces123. The surface coating layer contains a material having solder wettability more than that of the base material of the first lead1, and contains, for example, Au in this embodiment. The surface coating layer is formed by, for example, substitution electroless plating. Further, forming of the surface coating layer is optional

As shown inFIG.2, the plurality of second leads2are arranged at intervals on two end portions of the semiconductor device A1in the x direction or on two end portions of the semiconductor device A1in the y direction, and are spaced from the first lead1. More specifically, between two first terminal portions120disposed on one end of the semiconductor device A1(the upper end inFIG.2) in the y direction, a plurality of second leads2are arranged in a row in parallel to an edge of one side of the mounting portion110(the upper side inFIG.2) in the y direction. Further, between two first terminal portions120disposed on another end of the semiconductor device A1(the lower end inFIG.2) in the y direction, a plurality of second leads2are arranged in a row in parallel to an edge of another side of the mounting portion110(the lower side inFIG.2) in the y direction. Further, between two first terminal portions120disposed on one end of the semiconductor device A1(the right end inFIG.2) in the x direction, a plurality of second leads2are arranged in one column in parallel to an edge of one side of the mounting portion110(the right side inFIG.2) in the x direction. Further, between two first terminal portions120disposed on another end of the semiconductor device A1(the left end inFIG.2) in the x direction, a plurality of second leads2are arranged in one column in parallel to an edge of another side of the mounting portion110(the left side inFIG.2) in the x direction.

The second leads2are electrically connected to the semiconductor element3by the bonding wires4, respectively. Each second lead2includes a joining portion210and a second terminal portion220.

The second terminal portion220is rectangular in shape when viewed in the z direction. In the second leads2, the mounting portion110with respect to the first lead1is disposed on an opposite side. The second terminal portion220has a second terminal portion main surface221, a second terminal portion back surface222and a second terminal portion side surface223. The second terminal portion main surface221and the second terminal portion back surface222face opposite sides in the z direction. The second terminal portion main surface221is a surface facing the top inFIG.4andFIG.5. The second terminal portion back surface222is a surface facing the bottom ofFIG.4andFIG.5. The second terminal portion end surface223is a surface connecting the second terminal portion main surface221and the second terminal portion back surface222, and faces, in the second terminal portion220, a side opposite to the mounting portion110of the first lead1. The second terminal portion back surface222and the second terminal portion end surface223are individually exposed from the sealing resin5and are connected to each other to form terminals (referring toFIG.4).

The joining portion210extends from the second terminal portion220toward the mounting portion110of the first lead1. In this embodiment, as the second leads2arranged in parallel to the edges on two sides of the mounting portion110in the y direction are disposed closer the sides on two ends in the x direction, the more inclining the joining portion210is relative to the y direction. Further, as the second leads2arranged in parallel to the edges on two sides of the mounting portion110in the x direction are disposed closer the sides on two ends in the y direction, the more inclining the joining portion210is relative to the x direction. The design above is aimed to more readily connect the semiconductor element3mounted on the mounting portion main surface111to the second terminal portions220of the second leads2by the bonding wires4. In this embodiment, the joining portions210of the second leads2respectively disposed closest to the side on the two ends (adjacent to the connecting portions130) extend substantially in parallel to the extension directions of the adjacent connecting portions130. Further, whether or not the joining portions210are inclined relative to the x direction or the y direction is optional.

The joining portions210have a thickness (dimension in the z direction) that is approximately one-half of the thickness of the second terminal portions220. The joining portions210are formed by, for example, half-etching processing. Each joining portion210has a joining portion main surface211and a joining portion back surface212. The joining main surface211and the joining portion back surface212face opposite sides in the z direction. The joining portion main surface211is a surface facing the top inFIG.4andFIG.5. The joining portion main surface211is a surface for bonding to the bonding wires4. The joining portion main surface211and the second terminal portion main surface221are of the same plane (referring toFIG.2andFIG.4). The joining portion back surface212is a surface facing the bottom inFIG.4andFIG.5. Further, the joining portions210may also have a thickness equal to the thickness of the second terminal portions220. In this case, the joining portion back surfaces212and the second terminal portion back surfaces222are of the same plane.

A surface coating layer (not shown) is formed on all parts of the second leads2that are exposed from the sealing layer5. In this embodiment, the surface coating layer is formed on the second terminal portion back surfaces222and the second terminal portion end surfaces223. This surface coating layer is the same with the surface coating layer of the first lead1, for example, containing Au and formed by substitution electroless plating. Further, forming of the surface coating layer is optional.

In this embodiment, as shown inFIG.6, the dimension of the connecting portion130of the first lead1in a direction perpendicular to the extension direction of the connecting portion130and the z direction, that is, a connecting portion width dimension W1, is sufficiently large. More specifically, the connecting portion width dimension W1is greater than a joining portion width dimension W2of the joining portion210of the second lead2adjacent to the connecting portion130, and is approximately three times the joining portion width dimension W2, wherein the joining portion width dimension W2is a dimension in a direction perpendicular to the extension direction of the joining portion210and the z direction. Further, the connecting portion width dimension W1is not specifically defined, and is ideally equal to or more than twice the joining portion width dimension W2. In this embodiment, the connecting portion width dimension W1is approximately 0.3 mm. Further, the connecting portion width dimension W1is preferably equal to or more than 0.2 mm.

Further, in this embodiment, as shown inFIG.6, a minimum distance L1between (the joining portion210of) two second leads2adjacent to the connecting portion130of the first lead1and interposed with the connecting portion130is sufficiently large. More specifically, the minimum distance L1is approximately five times a minimum distance L2between one of the second leads2and the connecting portion130. Further, the minimum distance L1is not specifically defined, and is ideally at least four times the minimum distance L2. That is to say, an ideal ratio of the minimum distance L2to the minimum distance L1is equal to or less than ¼.

The semiconductor element3is an element that practices electrical functions of the semiconductor device A1. The semiconductor element3is not limited to a specific type, and may be appropriately selected from various type of integrated circuit elements, an active functional element or a passive functional element. As shown inFIG.1andFIG.2, in this embodiment, the semiconductor element3is rectangular in shape when viewed in the z direction.

The semiconductor element3has an element main surface31, an element back surface32and a plurality of electrode pads33. The element main surface31and the element back surface32face opposite sides in the z direction. The element main surface31is a surface facing the top inFIG.4andFIG.5. The element back surface32is a surface facing the bottom inFIG.4andFIG.5. As shown inFIG.2, the plurality of electrode pads33are disposed on the element main surface31, and are disposed in a plural quantity in a row on each edge of the rectangular element main surface31in this embodiment. Further, the configuration of the electrode pads33is not specifically defined. The semiconductor element3is mounted on the mounting main surface111of the first lead1. More specifically, the element back surface32of the semiconductor element3is mounted on the mounting main surface111by a bonding material6. The bonding material6includes common insulative bonding materials or electrically conductive bonding materials. In this embodiment, an insulative bonding material is used as the bonding material6because electrode pads are not disposed on the element back surface32. Further, when electrode pads are disposed on the element back surface32and the electrode pads are electrically connected to the first lead1, an electrically conductive bonding material is used as the bonding material6.

The plurality of bonding wires4electrically connect the semiconductor element3to the second leads2. In this embodiment, the plurality of electrode pads33formed on the element main surface31of the semiconductor element3are connected to the joining portion main surfaces211of the plurality of second leads2by the plurality of bonding wires4, respectively. The material of the bonding wires4is not specifically defined, and may be, for example, Au, Al and Cu. In this embodiment, the bonding wires4contain, for example, Au.

The sealing resin5covers a part of each of the first lead1and the second leads2, the semiconductor element3and the bonding wires4. The sealing resin5includes, for example, black epoxy. Further, the material of the sealing resin5is not specifically defined.

The sealing resin5has a resin main surface51, a resin back surface52and resin side surfaces53. The resin main surface51and the resin back surface52face opposite sides in the z direction. The resin main surface51is a surface facing the top inFIG.4andFIG.5. The resin back surface52is a surface facing the bottom inFIG.4andFIG.5. The resin side surfaces53are surfaces connecting the resin main surface51and the resin back surface52. In this embodiment, the resin side surfaces53are four in quantity, and individually face the x direction or the y direction.

The sealing resin5covers parts other than the mounting portion back surface112, the first terminal portion back surface122and the first terminal portion side surfaces123in the first lead1. The mounting portion back surface112, the first terminal portion back surface122and the first terminal portion side surfaces123are exposed from the sealing resin5. The mounting portion back surface112, the first terminal portion back surface122and the resin back surface52are of the same plane. The first terminal portion end surfaces123and the resin side surfaces53are of the same plane. Further, the sealing resin5covers parts other than the second terminal portion back surfaces222and the second terminal portion end surfaces223of the second leads2. The second terminal portion back surface222and the second terminal portion end surfaces223are exposed from the sealing resin5. The second terminal portion back surfaces222and the resin back surface52are of the same plane. The second terminal portion end surfaces223and the resin side surfaces53are of the same plane.

Next, details of mounting the semiconductor device A1on the wiring substrate are given below.FIG.7andFIG.8are drawings for illustrating mounting structures of the semiconductor device A1on a wiring substrate9.FIG.7shows a top view of a state in which the semiconductor device A1is mounted on the wiring substrate9.FIG.8shows an enlarge section diagram of a main part ofFIG.7along the line VIII-VIII. Further, inFIG.7, an imaginary line (double-dotted line) is used for the semiconductor device A1to indicate the contour of the semiconductor device A1.

The wiring substrate9is, for example, a substrate formed by a base material containing glass epoxy and having a Cu-containing wiring pattern formed thereon. Further, the materials of the base material and the wiring pattern are not specifically defined. As shown inFIG.7, the wiring substrate9includes a mounting portion land91, first terminal portion lands92, second terminal portion lands93, connecting wires94and second terminal portion connecting wires95as the wiring pattern.

The mounting portion land91is a rectangular land, and has sides thereof disposed in parallel to the x direction or the y direction. Each first terminal portion land92is a rectangular land located on a line elongated from the diagonal line of the mounting portion land91. For one mounting portion land91, four first terminal portion lands92are disposed around the mounting portion land91. The sides of each first terminal portion land92are parallel to the sides of the mounting portion land91. That is to say, the sides of each first terminal portion land92are parallel to the x direction or the y direction. Each connecting wire94is a wire connecting the mounting portion land91with the first terminal portion land92, and extends along the direction of the diagonal line of the mounting portion land91. Four connecting wires94are disposed for one mounting portion land91, and each connecting wire94is connected to the mounting portion land91and any one of the four first terminal portion lands92. In the semiconductor device A1, in order to arrange the connecting portion130, the gap (the minimum distance L1) between two second leads2individually adjacent to the connecting portion130and interposed with the connecting portion130is sufficiently large. Thus, the gap between two second terminal portion lands93respectively connected to the two second leads2also becomes sufficiently large. Therefore, the connecting wire94may be disposed between the two second terminal portion lands93.

The second terminal portions93are shaped as long rectangles extending toward the mounting portion land91, and are disposed in a plural quantity around the mounting portion land91. The second terminal portion lands93are spaced from one another between two adjacent first terminal portion lands92, and are disposed at intervals from the mounting portion land91, the first terminal portion lands92and the connecting wires94. More specifically, between two first terminal portion lands92disposed on one side (the upper side inFIG.7) of the mounting portion land91in the y direction, a plurality of second terminal portion lands93are arranged in a row in parallel to the x direction. Further, between two first terminal portion lands92disposed on another side (the lower side inFIG.7) of the mounting portion land91in the y direction, a plurality of second terminal portion lands93are arranged in a row in parallel to the x direction. Further, between two first terminal portion lands92disposed on one side (the right side inFIG.7) of the mounting portion land91in the x direction, a plurality of second terminal portion lands93are arranged in a row in parallel to the y direction. Further, between two first terminal portion lands92disposed on another side (the left side inFIG.7) of the mounting portion land91in the x direction, a plurality of second terminal portion lands93are arranged in a row in parallel to the y direction. The second terminal portion connecting wires95are wires connected to the second terminal portion lands93. One second terminal portion connecting wire95is disposed for one second terminal portion land93, and so the second terminal portion connecting wires95are disposed in a quantity equal to that of the second terminal portion lands93. Each second terminal portion connecting wire95extends toward a side opposite to the mounting portion land91with respect to the respective second terminal portion land93.

In this embodiment, as shown inFIG.7, the dimension of each connecting wire94in a direction perpendicular to the extension direction of the connecting wire94and the z direction, that is, a connecting wire width dimension W3, is sufficiently large. More specifically, the connecting wire width dimension W3is greater than a second terminal portion land width dimension W4of the second terminal portion land93adjacent to the connecting wire94, and is approximately three times the second terminal portion land width dimension W4, wherein the second terminal portion land width dimension W4is a dimension in a direction perpendicular to the extension direction of the second terminal portion land93and the z direction. Further, the connecting wire width dimension W3is not specifically defined, and is ideally equal to or more than twice the second terminal portion land width dimension W4. In this embodiment, the connecting wire width dimension W3is approximately 0.3 mm. Further, the connecting wire width dimension W3is ideally equal to or more than 0.2 mm.

Further, in this embodiment, as shown inFIG.7, a minimum distance L3between two second terminal portion lands93individually adjacent to the connecting wire94and interposed with the connecting wire94is sufficiently large. More specifically, the minimum distance L3is approximately five times a minimum distance L4between one of the two second terminal portion lands93and the connecting wire94. Further, the minimum distance L3is not specifically defined, and is ideally at least four times the minimum distance L4. That is to say, a ratio of the minimum distance L4to the minimum distance L3is ideally equal to or less than ¼.

Further, the shapes of the mounting portion land91, the first terminal portion lands92and the second terminal portion lands93are not limited to being rectangles.

The semiconductor device A1is mounted on the wiring substrate9, and as shown inFIG.8, the terminals are bonded to the wiring pattern of the wiring substrate9by a solder99. The mounting back surface112of the first lead1is bonded to the mounting portion land91. The first terminal portion back surface122of the first lead1is bonded to any one first terminal portion land92. The second terminal portion back surface222of one second lead2is bonded to any one second terminal portion land93.

Further, the mounting portion land91and the first terminal portion lands92may also be connected through vias to a wiring pattern disposed inside the wiring substrate9or a wiring pattern formed on a surface of an opposite side.

Next, effects of the semiconductor device A1are described below.

According to the embodiment, the semiconductor device A1enables the mounting portion back surface112exposed from the sealing resin5to be connected to the mounting portion land91, thereby being mounted to the wiring substrate9. The semiconductor element3is mounted on the mounting portion110. The mounting portion land91is connected to the first terminal portion land92by the connecting wire94. In contribution to the sufficiently large connecting wire width dimension W3, heat emitted by the semiconductor element3is transmitted through the mounting portion110, the mounting portion land91and the connecting wires94to the first terminal portion lands92and is released. That is to say, a heat dissipation area on the wiring substrate9is enlarged to a total area of the mounting portion land91, the connecting wires94and the first terminal portion lands92. Therefore, the semiconductor device A1ensures the heat dissipation area on the surface of the wiring substrate9.

Further, according to the embodiment, the mounting portion110mounted with the semiconductor element3is connected to the first terminal portions120by the connecting portions130. The first terminal portion back surfaces122are exposed from the sealing resin5. The semiconductor device A1enables the first terminal portion back surfaces122to be connected to the first terminal portion lands92, thereby being mounted to the wiring substrate9. In contribution to the sufficiently large connecting portion width dimension W1, heat emitted from the semiconductor element3is transmitted through the mounting portion110, the connecting portions130and the first terminal portions120to the first terminal portion lands92on the wiring substrate9and is released. That is to say, the semiconductor device A1further promotes heat dissipation toward the first terminal portion lands92using the connecting portions130and the first terminal portions120.

FIG.9toFIG.11are drawings for illustrating a simulated heat dissipation state in which the semiconductor device A1is mounted on the wiring substrate9.FIG.9andFIG.10are drawings for illustrating a semiconductor device A1′ and a wiring substrate9′ used for comparison, andFIG.11is a drawing showing the simulation result.

FIG.9shows a top view of the semiconductor device A1′ used for comparison, and is a drawing corresponding toFIG.1. As shown inFIG.9, compared to the semiconductor device A1, the semiconductor device A1′ is not provided with the first terminal portions120, and is provided with floating pins130′ in substitution for the connecting portions130, and the second leads2are disposed in proximity of the floating pins130′.FIG.10shows a top view of a state in which the semiconductor device A1′ is mounted on the wiring substrate9′, and is a drawing corresponding toFIG.7. Further, inFIG.10, an imaginary line (double-dotted line) of the semiconductor device A1′ indicates the contour of the semiconductor device A1′. As shown inFIG.10, the wiring substrate9′ is a wiring substrate in which the connecting wires94are not disposed in the wiring substrate9.

FIG.11(a)shows a diagram of temperature distribution in the wiring substrate9′ mounted with the semiconductor device A1′ after heat dissipation of the semiconductor element3.FIG.11(b)shows a diagram of temperature distribution in the wiring substrate9mounted with the semiconductor device A1after heat dissipation of the semiconductor element3. As shown inFIG.11(a), in the wiring substrate9′ mounted with the semiconductor device A1′, the temperature of only the mounting portion land91(near the center ofFIG.11(a)) rises. On the other hand, as shown inFIG.11(b), in the wiring substrate9mounted with the semiconductor device A1, heat of the mounting portion land91(near the center ofFIG.11(b)) is transmitted to the first terminal portion lands92(near four corners ofFIG.11(b)) and is released. Thus, compared to the wiring substrate9′ (referring toFIG.11(a)) mounted with the semiconductor device A1′, the temperature of the mounting portion land91is lowered. Further, thermal resistance of the wiring substrate9′ mounted with the semiconductor device A1′ is 34.0° C./W, and in comparison, thermal resistance of the wiring substrate9mounted with the semiconductor device A1is 27.7° C./W. It is apparent that thermal resistance is lowered and the heat dissipation effect is improved.

Further, according to this embodiment, the joining portion210of the second lead2adjacent to the connecting portion130extends substantially in parallel to the extension direction of the connecting portion130, and thus the connecting portion width dimension W1is further increased.

Further, according to this embodiment, each first terminal portion120includes a terminal connected and formed by the first terminal portion end surface123exposed from the sealing resin side surface53and the first terminal portion back surface122exposed from the sealing resin back surface52(referring toFIG.5). When the semiconductor device A1is mounted on the wiring substrate9, the terminal is bonded to the first terminal portion land92formed on the wiring substrate9by the solder99. A welding fillet (referring toFIG.8) formed by the solder99is formed on the first terminal portion end surface123, and so the bonding state of the first terminal portion120may also be determined according to the appearance after mounting. Further, the welding fillet formed on the first terminal portion end surface123may be used to reinforce mounting strength.

Further, in this embodiment, a situation where the first terminal portion end surfaces123, the second terminal portion end surfaces223and the resin side surfaces53of the sealing resin5are of the same plane is described; however, the present invention is not limited to such example. The first terminal portion end surfaces123and the second terminal portion end surfaces223may protrude from the resin side surfaces53, or may be recessed from the resin side surfaces53. Further, the first terminal portion end surfaces123and the second terminal portion end surfaces223may be flat or bent, or may be formed as protrusions or recesses. Further, the shapes of the first terminal portion end surfaces123and the second terminal portion end surfaces223are not specifically defined.

Further, in this embodiment, a situation where the mounting portion back surface112is connected to the mounting portion land91is described; however, the present invention is not limited to such example. For example, as shown inFIG.12, the wiring substrate9may selectively exclude the mounting portion land91and the connecting wires94. In this case, the first terminal portions120connected to the mounting portion110via the connecting portions130are also connected to the first terminal portion lands92. Thus, heat emitted by the semiconductor element3is transmitted through the mounting portion110, the connecting portions130and the first terminal portions120to the first terminal portion lands92and is released. Therefore, the heat dissipation area on the surface of the wiring substrate9may be ensured by enlarging the area of the first terminal portion lands92.

Second Embodiment

A semiconductor device A2according to the second embodiment of the present invention is described with reference toFIG.13andFIG.14. In these drawings, components identical or similar to those of the semiconductor device A1are denoted by the same numerals, and repeated details are omitted.

FIG.13shows a bottom view of the semiconductor device A2, and is a drawing corresponding toFIG.3of the first embodiment.FIG.14shows an enlarged section diagram of a main apart of a state in which the semiconductor device A2is mounted on the wiring substrate9, and is a drawing corresponding toFIG.8of the first embodiment.

The semiconductor device A2of this embodiment differs from the semiconductor device A1in that, the mounting portion back surfaces112are not exposed from the sealing resin5. The mounting portion110of this embodiment has a thickness (the dimension in the z direction) equal to the thickness of the connecting portions130, and is approximately one-half of the thickness of the first terminal portions120. The mounting portion110is formed, for example, by half-etching processing. Thus, in this embodiment, the mounting portion back surface112is not exposed from the sealing resin5.

In this embodiment, the first terminal portions120connected to the mounting portion110via the connecting portions130are also connected to the first terminal portion lands92, and thus heat emitted by the semiconductor element3is transmitted through the mounting portion110, the connecting portions130and the first terminal portions120to the first terminal portion lands92and is released. Therefore, the heat dissipation area on the surface of the wiring substrate9may be ensured by enlarging the area of the first terminal portion lands92.

Third Embodiment

A semiconductor device A3according to the third embodiment of the present invention is described with reference toFIG.15andFIG.16. In these drawings, components identical or similar to those of the semiconductor device A1are denoted by the same numerals, and repeated details are omitted.

FIG.15shows a bottom view of the semiconductor device A3, and is a drawing corresponding toFIG.3of the first embodiment.FIG.16shows an enlarged section diagram of a main apart of a state in which the semiconductor device A3is mounted on the wiring substrate9, and is a drawing corresponding toFIG.8of the first embodiment.

The semiconductor device A3of this embodiment differs from the semiconductor device A1in that, the connecting portion back surfaces132are exposed from the sealing resin5. The connecting portions130of this embodiment have a thickness (the dimension in the z direction) is equal to the thickness of the mounting portion110and the first terminal portions120. The connecting portion back surfaces132, the mounting portion back surface112and the first terminal portion back surfaces122are an integral surface of the same plane, and also become the same plane with the resin back surface52. Thus, in this embodiment, the connecting portion back surfaces132are also exposed from the sealing resin5. As shown inFIG.16, the connecting portion back surfaces132are bonded to the connecting wires94by the solder99.

In this embodiment, the effects the same with those of the first embodiment are also achieved. Hence, according to this embodiment, the connecting portions130have a thickness more than the thickness of the connecting portions130of the first embodiment, and the connecting portions130may more readily transmit heat from the mounting portion110toward the first terminal portions120. Further, because the connecting portion back surfaces132are connected to the connecting wires94, heat emitted by the semiconductor element3may also be transmitted to the connecting wires94through the connecting portions130. Therefore, the semiconductor device A3is capable of further promoting heat dissipation.

The semiconductor device and the mounting structures of the semiconductor device of the present invention are not limited to the examples given in the foregoing embodiments. Various design modifications may be made to the specific configurations of the components of the semiconductor device and the mounting structures of the semiconductor device of the present invention.

A semiconductor device, comprising:a semiconductor element;a first lead, being rectangular in shape when viewed in a thickness direction, comprising a mounting portion, four connecting portion and four first terminal portions, wherein the semiconductor element is mounted on the mounting portion, the connecting portions extend from four corners of the mounting portion, respectively, and the first terminal portions are connected to front ends of the connecting portions, respectively;a plurality of second leads, arranged, when viewed in the thickness direction, in a plurality quantity and in parallel to each edge of the mounting portion between two adjacent of the first terminal portions; anda sealing resin, covering at least a part of each of the first lead and the second leads; wherein,a part of each of the first terminal portions is exposed from the sealing resin,each of the second leads comprises a second terminal and a joining portion, wherein a part of each of the second terminal portions is exposed from the sealing resin, and the joining portion extends from the second terminal portion toward the mounting portion, anda dimension of a connecting portion width of the connecting portion is greater than a dimension of a joining portion width of the joining portion of the second lead, the dimension of the connecting portion width is a dimension in a direction perpendicular to an extension direction of the connecting portion and the thickness direction, and the dimension of the joining portion width is a dimension in a direction perpendicular to an extension direction of the joining portion and the thickness direction.
(Note 2)

The semiconductor device according to note 1, wherein the dimension of the connecting portion width is equal to or more than twice the dimension of the joining portion width.

The semiconductor device according to note 1 or 2, wherein the dimension of the connecting portion width is equal to or more than 0.2 mm.

The semiconductor device according to any one of notes 1 to 3, wherein a ratio of a minimum distance L2to a minimum distance L1is equal to or less than ¼, the minimum distance L1is a minimum distance between two of the second leads individually adjacent to the connecting portion and interposed with the connecting portion, and the minimum distance L2is a minimum distance between one of the second leads and the connecting portion.

The semiconductor device according to any one of notes 1 to 4, wherein the mounting portion has a mounting portion main surface mounted with the semiconductor element, and a mounting back surface facing a side opposite to the mounting portion main surface in the thickness direction; and the mounting portion back surface is exposed from the sealing resin.

The semiconductor device according to note 5, wherein the connecting portion has a connecting portion main surface facing a side same with the mounting portion main surface in the thickness direction, and the mounting portion main surface and the connecting portion main surface are of a same plane.

The semiconductor device according to note 5 or 6, wherein the first terminal portion has a first terminal portion back surface facing a side same with the mounting portion back surface in the thickness direction, and the first terminal portion back surface is exposed from the sealing resin.

The semiconductor device according to note 7, wherein the first terminal portion further has a first terminal portion end surface perpendicular to the first terminal portion back surface and exposed from the sealing resin.

The semiconductor device according to any one of notes 5 to 8, wherein the connecting portion is covered by the sealing resin.

The semiconductor device according to any one of claims5to9, wherein the connecting portion has a connecting portion back surface facing a side same with the mounting portion back surface in the thickness direction, and the connecting portion back surface is exposed from the sealing resin.

The semiconductor device according to any one of notes 5 to 10, wherein the extension direction of the joining portion of each of the second leads inclines relative to an extension direction of the second terminal portion, and becomes more inclined as getting closer to the second lead of the connecting portion.

The semiconductor device according to any one of notes 5 to 11, wherein the extension direction of the joining portion of the second lead adjacent to the connecting portion is substantially parallel to the extension direction of the connecting portion.

A mounting structure, comprising:the semiconductor device according to any one of notes 5 to 12; anda wiring substrate for mounting the semiconductor device, the wiring substrate comprising:a mounting portion land, bonded to the mounting portion back surface;four first terminal portion lands, bonded to the first terminal portions, respectively;a plurality of second terminal portion lands, bonded to the second terminal portions, respectively; andfour connecting wires, connected to the mounting portion land and the first terminal portion lands, respectively.
(Note 14)

The mounting structure according to note 13, wherein the second terminal portion lands extend toward the mounting portion land; and a dimension of a connecting wire width of the connecting wire is greater than a dimension of a second terminal portion land width of the second terminal portion land adjacent to the connecting wire, the dimension of the connecting wire width is a dimension in a direction perpendicular to an extension direction of the connecting wire and the thickness direction, and the dimension of the second terminal portion land width is a dimension in a direction perpendicular to an extension direction of the second terminal portion land and the thickness direction.

The mounting structure according to note 14, wherein the dimension of the connecting wire width is equal to or more than twice the dimension of the second terminal portion land width.

The mounting structure according to note 14 or 15, wherein the dimension of the connecting wire width is equal to or more than 0.2 mm.

The mounting structure according to any one of notes 14 to 16, wherein a ratio of a minimum distance L4to a minimum distance L3is equal to or less than ¼, the minimum distance L3is a minimum distance between two of the second terminal portion lands individually adjacent to the connecting wire and interposed with the connecting wire, and the minimum distance L4is a minimum distance between one of the second terminal portion lands and the connecting wire.