Electronic device

Abstract

To provide an electronic device capable of improving connection reliability of a semiconductor package.SOLUTION: An electronic device 10 comprises a printed circuit board 30, a surface-mounted semiconductor package 41 and a case 21 which is a stationary structure. The case 21 includes a portion which is opposed to one face 301 of the printed circuit board 30. The printed circuit board 30 includes a plurality of fixing holes 31 for fixture to the case 21. A direction of warpage of the printed circuit board 30 and a direction of warpage of the semiconductor package 41 in temperature fluctuation are reverse to each other. The printed circuit board 30 includes a stress relaxation section 32 for relaxing a stress which acts on a mounting part of the semiconductor package 41 by the difference in the direction of warpage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The disclosure in this specification relates to an electronic device.

Background Art

[0002] Patent Document 1 discloses an electronic device including a printed circuit board, a semiconductor package mounted on the printed circuit board, and a fixing structure. The printed circuit board has through holes for screw fastening and is fixed to the fixing structure by screw fastening. The description of the prior art document is incorporated herein by reference as an explanation of the technical elements in this specification.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, by providing a slit between the through hole and the semiconductor package, the distortion generated around the through hole due to screw fastening is suppressed, and the connection reliability of the semiconductor package located near the through hole is ensured. However, even if the printed circuit board and the semiconductor package have a common configuration, there may be cases where connection reliability can be ensured without providing a slit depending on the mounting position of the semiconductor package. Also, even when the semiconductor package is mounted at a position away from the through hole, the connection reliability may decrease. From the above viewpoints, or from other viewpoints not mentioned, further improvements are required for the electronic device.

[0005] One of the objects of the present disclosure is to provide an electronic device capable of improving the connection reliability of a semiconductor package.

Means for Solving the Problems

[0006] An electronic device according to one aspect of the disclosure includes a printed circuit board (30) having a front surface (301) and a back surface (302) opposite to the front surface in the thickness direction, a surface-mounted semiconductor package (41) mounted on the printed circuit board, a fixing structure (21) having a portion facing the front surface, and is provided with The printed circuit board has a plurality of fixing holes (31) for fixing the printed circuit board to the fixing structure, When the temperature fluctuates, the direction of warping of the printed circuit board and the direction of warping of the semiconductor package are opposite to each other in the direction along the thickness direction, The printed circuit board has a stress relaxation portion (32) that relaxes the stress acting on the mounting portion of the semiconductor package due to the different directions of warping.

[0007] It has been found that when the direction of warping of the semiconductor package during temperature fluctuation is opposite to the direction of warping of the printed circuit board, stress concentrates on the mounting portion of the semiconductor package and the connection reliability decreases. According to the disclosed electronic device, since it has a stress relaxation portion, the stress acting on the mounting portion of the semiconductor package due to the different directions of warping can be relaxed. Therefore, the connection reliability of the semiconductor package can be improved.

[0008] The plurality of aspects disclosed in this specification adopt different technical means to achieve their respective purposes. The claims and the reference numerals in parentheses described in this column exemplify the correspondence with the parts of the embodiments described later, and are not intended to limit the technical scope. The objects, features, and effects disclosed in this specification will become clearer by referring to the subsequent detailed description and the accompanying drawings.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Hereinafter, a plurality of embodiments will be described with reference to the drawings. In each embodiment, the same reference numerals may be assigned to corresponding components, and redundant explanations may be omitted. When only a part of the configuration is described in each embodiment, for the other parts of the configuration, the configurations of other embodiments described previously can be applied. Also, not only the combinations of configurations explicitly shown in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined with each other as long as there is no problem with the combination.

[0011] (First Embodiment) First, the schematic configuration of the electronic device will be described. The electronic device may be mounted on a moving body, for example. The moving body is, for example, a vehicle, an aircraft, a ship, a construction machine, an agricultural machine, etc. As an example, the electronic device of this embodiment is mounted on a vehicle.

[0012] <Electronic Device> FIG. 1 is a cross-sectional view showing an example of an electronic device. FIG. 1 is a cross-sectional view taken along line I-I shown in FIG. 2 in the electronic device. Hereinafter, the thickness direction of the printed circuit board is indicated as the Z direction. Also, one direction orthogonal to the Z direction is indicated as the X direction, and the direction orthogonal to both the Z direction and the X direction is indicated as the Y direction. Unless otherwise specified, the shape viewed from the Z direction in plan view, in other words, the shape along the XY plane defined by the X direction and the Y direction is defined as the planar shape. The plan view from the Z direction may be simply referred to as the plan view.

[0013] As shown in FIG. 1, the electronic device 10 includes a housing 20, a printed circuit board 30, and electronic components 40. As an example, the electronic device 10 of the present embodiment further includes screws 50 and a heat dissipation gel 60. The electronic device 10 may further include a connector (not shown). The connector is mounted on the printed circuit board 30 in order to electrically connect the circuit constituted by the printed circuit board 30 and the electronic components 40 to the outside (external device) of the electronic device 10.

[0014] The housing 20 forms the outer shell of the electronic device 10. The housing 20 houses other elements constituting the electronic device 10. The housing 20 may be formed using a metal material such as Al or Fe, or may be formed using a resin material such as PPS or PBT. It may be formed using ceramic. For example, a part of the housing 20 may be formed using a metal material and another part may be formed using a resin material. The planar shape of the housing 20 is, for example, substantially rectangular.

[0015] As an example, the housing 20 of the present embodiment includes a case 21 and a cover 22. The case 21 and the cover 22 are formed using Al. The case 21 has a box shape with one surface open in the Z direction. The case 21 has opposing walls 211, side walls 212, a plurality of pedestals 213, and screw holes 214. The opposing wall 211 faces one surface 301 of the printed circuit board 30. The side wall 212 is continuous with the opposing wall 211. The side wall 212 extends in the Z direction from the opposing wall 211.

[0016] The pedestal 213 protrudes from the opposing wall 211 and supports the printed circuit board 30. The pedestal 213 may be provided away from the side wall 212 or may be provided in a manner continuous with the side wall 212. The case 21 has four pedestals 213 to support the four corners of the printed circuit board 30. The screw holes 214 are provided in each of the pedestals 213. The case 21 corresponds to a fixed structure.

[0017] The cover 22 is assembled to the case 21. In the assembled state, the cover 22 provides an accommodation space together with the case 21. The cover 22 is provided, for example, to close the opening of the case 21. The cover 22 is fixed to the case 21 by screw fastening or the like.

[0018] The printed circuit board 30 may be referred to as a substrate, a wiring board, a printed wiring board, etc. The printed circuit board 30 has a front surface 301 and a back surface 302. The back surface 302 is the surface opposite to the front surface 301 in the Z direction, which is the thickness direction of the printed circuit board 30. The planar shape of the printed circuit board 30 is not particularly limited. As an example, the printed circuit board 30 of the present embodiment is substantially rectangular in plan view.

[0019] The printed circuit board 30 has an insulating base material and a conductor. The insulating base material is formed using a material having electrical insulation properties such as resin. As the insulating base material, for example, a material containing only resin may be adopted, or a combination of a glass cloth, a non-woven fabric, etc. and resin may be adopted. The conductor is formed using a metal material having good conductivity such as Cu. The conductor includes a wiring layer. The wiring layer may be referred to as a wiring, a wiring pattern, a conductor pattern, etc. The wiring layer may be formed, for example, by patterning a metal foil or by printing. At least a part of the conductor constitutes a circuit together with the electronic component 40. Therefore, the printed circuit board 30 on which the electronic component 40 is mounted may be referred to as a circuit board.

[0020] The wiring includes at least surface wiring disposed on the surface layer on the side of one surface 301 with respect to the base material. The wiring may include surface wiring disposed on the surface layer on the back surface 302 side, or may include inner layer wiring disposed inside the base material. That is, the printed circuit board 30 may be a single-sided board, a double-sided board, or a multi-layer board. As an example, the printed circuit board 30 of the present embodiment is a glass epoxy board in which wiring layers are arranged in multiple layers. The printed circuit board 30 has lands, which are electrode portions of the wiring layer, on the surface layers of one surface 301 and the back surface 302.

[0021] In addition to the wiring layer, the conductor may include a via conductor or a through-hole land. The via conductor is formed by disposing a conductor such as plating in a through-hole (via) formed in an insulating layer constituting the insulating base material. The via conductor electrically connects, for example, wiring layers disposed in different layers. The through-hole land is formed on the wall surface of a through-hole that penetrates the printed circuit board 30 in the Z direction. The conductor may include a conductor that does not provide a wiring function, for example, a conductor for heat dissipation.

[0022] The printed circuit board 30 has fixing holes 31. The fixing holes 31 penetrate the printed circuit board 30 in the Z direction. The fixing holes 31 are holes for fixing the printed circuit board 30 to the case 21. The fixing holes 31 are provided at the four corners of the printed circuit board 30. The fixing holes 31 are provided so as to overlap with the screw holes 214 in a plan view. The fixing holes 31 may be referred to as mounting holes or the like. Screws 50 are inserted into the fixing holes 31. The screws 50 are screwed into the screw holes 214 of the pedestal 213 in a state of passing through the fixing holes 31. The printed circuit board 30 is fixed to the case 21 (housing 20) by screw fastening.

[0023] The electronic component 40 is mounted on the printed circuit board 30. The electronic component 40, together with the conductors of the printed circuit board 30, provides a circuit. The electronic component 40 is soldered to the corresponding lands. The electronic component 40 includes at least a surface-mounted semiconductor package 41. The semiconductor package 41 may be referred to as an IC package. The electronic component 40 may include only the semiconductor package 41, or may include, in addition to the semiconductor package 41, a component different from the semiconductor package 41. The electronic component 40 may be arranged on only one surface 301, or may be arranged on only the back surface 302. It may be arranged on each of the one surface 301 and the back surface 302.

[0024] As an example, the electronic device 10 of the present embodiment includes a plurality of electronic components 40. The electronic components 40 are arranged on each of the one surface 301 and the back surface 302. The semiconductor package 41 is arranged on the one surface 301. A heat dissipation gel 60 is in close contact with the semiconductor package 41. The heat dissipation gel 60 is interposed between the semiconductor package 41 and the inner surface of the opposing wall 211 of the case 21 of the housing 20. Thereby, the heat generated by the semiconductor package 41 can be released to the case 21 (housing 20) through the heat dissipation gel 60. Note that the arrangement of the semiconductor package 41 is not limited to the example shown in FIG. 1. The semiconductor package 41 may be arranged on the back surface 302, or may be arranged on each of the one surface 301 and the back surface 302.

[0025] <Printed Circuit Board> Next, based on FIGS. 2 to 4, the structure of the printed circuit board will be described in more detail. FIG. 2 is a plan view showing an example of the printed circuit board. FIG. 3 is a plan view showing another example of the printed circuit board. In FIGS. 2 and 3, semiconductor packages mounted on the printed circuit board are shown together. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2. In FIG. 4, for the sake of simplicity, only the case, which is a fixed structure of the housing, is shown. Also, the case is shown in a simplified manner. Only the semiconductor package is shown as the electronic component. The P direction shown in FIG. 4 is a predetermined direction along line IV-IV.

[0026] As shown in FIGS. 2 and 3, the printed circuit board 30 has a substantially rectangular planar shape with the X direction as the longitudinal direction and the Y direction as the short side direction. The printed circuit board 30 has side surfaces 303, 304, 305, and 306 as side surfaces connecting the front surface 301 and the back surface 302. The side surface 304 is the surface opposite to the side surface 303 in the X direction. The side surface 306 is the surface opposite to the side surface 305 in the Y direction.

[0027] The printed circuit board 30 has a plurality of fixing holes 31 as described above. The fixing holes 31 are provided around the four corners of the printed circuit board 30 having a substantially rectangular planar shape. The printed circuit board 30 has four fixing holes 311, 312, 313, and 314 as the fixing holes 31. The fixing hole 311 is provided at a corner (corner portion) defined by two side surfaces 303 and 304. The fixing hole 312 is provided at a corner defined by two side surfaces 304 and 305. The fixing hole 313 is provided at a corner defined by two side surfaces 305 and 306. The fixing hole 314 is provided at a corner defined by two side surfaces 306 and 303.

[0028] Hereinafter, in the printed circuit board 30, the portion fixed to the case 21 by the screw 50, that is, the fixing hole 31 and its periphery may be indicated as the fixing portion 315. The fixing portion 315 is a portion that overlaps with the head of the screw 50 in a plan view. In FIG. 4, for convenience, the screw hole 214, the fixing hole 31, and the screw 50 are omitted, and the fixing portion 315 is shown. One of the fixing portions 315 shown in FIG. 4 corresponds to the fixing hole 311, and the other corresponds to the fixing hole 313.

[0029] The printed circuit board 30 further has a stress relaxation portion 32. The stress relaxation portion 32 relaxes the stress acting on the mounting portion (soldering portion) of the semiconductor package 41 when the warping direction of the semiconductor package 41 is different from (opposite to) the warping direction of the printed circuit board 30 as will be described later. As an example, the stress relaxation portion 32 of the present embodiment includes a slit 321 and a partitioning portion 322.

[0030] The slit 321 penetrates the printed circuit board 30 in the Z direction and extends in a predetermined direction within the XY plane. The slit 321 blocks the transmission of stress starting from the fixing hole 31 (fixing portion 315). The slit 321 partitions a part of the printed circuit board 30 including the fixing hole 31 (fixing portion 315). The slit 321 is provided corresponding to the fixing hole 31. The slit 321 is provided individually with respect to the fixing hole 31. The slit 321 is provided near the four corners of the printed circuit board 30. The slit 321 is arranged so as to cross at least one of a plurality of virtual straight lines L1, L2, L3, L4, L5, L6 that virtually connect different fixing holes 31, for example, their centers, to each other in a plan view. In FIGS. 2 and 3, the virtual straight lines are indicated by two-dot chain lines.

[0031] The virtual straight line L1 is a straight line that virtually connects the fixing holes 311 and 312. The virtual straight line L2 is a straight line that virtually connects the fixing holes 311 and 314. The virtual straight line L3 is a straight line that virtually connects the fixing holes 311 and 313. The virtual straight line L4 is a straight line that virtually connects the fixing holes 312 and 313. The virtual straight line L5 is a straight line that virtually connects the fixing holes 312 and 314. The virtual straight line L6 is a straight line that virtually connects the fixing holes 313 and 314.

[0032] In this embodiment as an example, for all the virtual straight lines L1, L2, L3, L4, L5, L6, at least one slit 321 is arranged so as to cross them. Each slit 321 is arranged so as to cross two virtual straight lines. The slit 321 opens to the side surface of the printed circuit board 30. The slit 321 opens to the first side surface of the printed circuit board 30 having a substantially rectangular shape in plan view and extends from the first side surface toward the second side surface located opposite to the first side surface. All the slits 321 have a common shape with each other in a plan view.

[0033] Specifically, the slit 321 corresponding to the fixing hole 311 opens on the side surface 303, extends toward the side surface 305, and crosses the virtual straight lines L2 and L3. The slit 321 corresponding to the fixing hole 312 opens on the side surface 304, extends toward the side surface 306, and crosses the virtual straight lines L1 and L5. The slit 321 corresponding to the fixing hole 312 is arranged such that it is rotated 90° clockwise around an axis substantially parallel to the Z direction with respect to the slit 321 corresponding to the fixing hole 311. The slit 321 corresponding to the fixing hole 313 opens on the side surface 305, extends toward the side surface 303, and crosses the virtual straight lines L3 and L4. The slit 321 corresponding to the fixing hole 313 is arranged such that it is rotated 90° clockwise around an axis substantially parallel to the Z direction with respect to the slit 321 corresponding to the fixing hole 312. The slit 321 corresponding to the fixing hole 314 opens on the side surface 306, extends toward the side surface 304, and crosses the virtual straight lines L5 and L6. The slit 321 corresponding to the fixing hole 314 is arranged such that it is rotated 90° clockwise around an axis substantially parallel to the Z direction with respect to the slit 321 corresponding to the fixing hole 313. The plurality of slits 321 have rotational symmetry.

[0034] The shape and the extending length of the slit 321 are not particularly limited. In the examples shown in FIGS. 2 and 3, each of the slits 321 crosses two virtual straight lines. The stress relaxation portion 32 may adopt any of the slits 321 shown in FIGS. 2 and 3. The slit 321 shown in FIG. 2 has a first slit portion 3211 and a second slit portion 3212. One end of the first slit portion 3211 opens on the side surface and extends in a direction orthogonal to the side surface. The second slit portion 3212 is connected to the end opposite to the opening end of the first slit portion 3211 and extends in an oblique direction so as to narrow the width of the partition portion 322. For example, the first slit portion 3211 of the slit 321 corresponding to the fixing hole 311 extends in the X direction, and the second slit portion 3212 extends in an oblique direction so as to approach the side surface 304.

[0035] The slit 321 shown in FIG. 3 is longer than the slit 321 shown in FIG. 2. The slit 321 shown in FIG. 3 has a third slit portion 3213 in addition to the first slit portion 3211 and the second slit portion 3212. The first slit portion 3211 and the second slit portion 3212 are the same as the configuration shown in FIG. 2. The third slit portion 3213 is continuous with the end portion of the second slit portion 3212 on the side opposite to the first slit portion 3211, and extends substantially parallel to the first slit portion 3211. For example, the third slit portion 3213 of the slit 321 corresponding to the fixing hole 311 extends in the X direction.

[0036] The partitioning portion 322 is a portion partitioned by the slit 321 on the printed circuit board 30 and includes the fixing hole 31 (fixing portion 315). The partitioning portion 322 is an area inside the slit 321. The end portion of the partitioning portion 322 is defined by the slit 321. The broken lines shown in FIGS. 2 and 3 indicate the end portions of the partitioning portion 322. The partitioning portion 322 extends generally in the X direction or the Y direction. The partitioning portion 322 is provided so as to be elastically deformable (spring deformable). The partitioning portion 322 relaxes the stress starting from the fixing hole 31 (fixing portion 315) by deformation.

[0037] The partitioning portion 322 including the fixing hole 311 extends in the X direction from the fixing hole 311 (fixing portion 315). The partitioning portion 322 including the fixing hole 312 extends in the Y direction from the fixing hole 312. The partitioning portion 322 including the fixing hole 313 extends in the X direction from the fixing hole 313. The partitioning portion 322 including the fixing hole 314 extends in the Y direction from the fixing hole 314.

[0038] <Semiconductor Package> Next, based on FIGS. 2 to 5, the structure of the semiconductor package will be described in more detail. FIG. 5 is a cross-sectional view showing an example of the semiconductor package. FIG. 5 is a cross-sectional view corresponding to FIG. 4.

[0039] The semiconductor package 41 may be a package with leads protruding from the main body, or a non-lead package without protruding leads. As an example, the semiconductor package 41 of this embodiment is a non-lead package as shown in FIG. 5. As the non-lead package, QFN, SON, BGA, etc. can be adopted. QFN is the abbreviation of Quad Flat Non-leaded package. SON is the abbreviation of Small Outline Non-leaded package. BGA is the abbreviation of Ball Grid Array. The semiconductor package 41 of this embodiment is QFN.

[0040] The semiconductor package 41 has a lower surface 411, an upper surface 412, and a side surface 413 as the surfaces forming the outer contour. The lower surface 411 is the surface facing the printed circuit board 30. The lower surface 411 may be referred to as the bottom surface, the opposing surface, etc. The upper surface 412 is the surface opposite to the lower surface 411 in the Z direction. The side surface 413 is the surface connecting the lower surface 411 and the upper surface 412. In the example shown in FIG. 4, the heat dissipation gel 60 is interposed between the upper surface 412 of the semiconductor package 41 and the inner surface of the opposing wall 211 of the case 21.

[0041] The semiconductor package 41 includes a lead frame 42, a semiconductor chip 43, and a sealing resin body 44. The lead frame 42 is a metal plate formed using a metal material with good conductivity such as Cu. As an example, the lead frame 42 of this embodiment is formed using Cu. The lead frame 42 may be referred to as a conductor, a metal plate, etc. The lead frame 42 has an island 421 and a plurality of terminals 422. The semiconductor chip 43 is disposed on the island 421. The island 421 may be referred to as a heat sink, a heat dissipation plate, a heat spreader, a heat pad. The island 421 is substantially flush with the lower surface 411 and exposed from the lower surface 411. The island 421 is soldered to the corresponding land of the printed circuit board 30. The land may be a land providing a circuit or a land providing a heat dissipation function without providing a circuit function.

[0042] Terminal 422 is soldered to a corresponding land on the printed circuit board 30. Terminal 422 may be referred to as an electrode, an electrode pad, etc. Terminal 422 is arranged so as to surround the island 421 in plan view. A plurality of terminals 422 are arranged along each of the four sides on the lower surface 411 having a substantially rectangular shape in plan. Terminal 422 is substantially flush with the lower surface 411 and exposed from the lower surface 411. Each of the plurality of terminals 422 is substantially flush with the side surface 413 and exposed from the side surface 413. Terminal 422 is exposed from the four side surfaces 413.

[0043] The semiconductor chip 43 is formed by forming elements and integrated circuits on a semiconductor substrate. As an example, the semiconductor chip 43 of the present embodiment is formed by forming an integrated circuit on a semiconductor substrate made of Si. The semiconductor chip 43 is arranged on one surface of the island 421 and joined to the island 421. One surface is the surface opposite to the exposed surface. The semiconductor chip 43 has pads (not shown) on the surface opposite to the island 421. The pads of the semiconductor chip 43 are electrically connected to the terminals 422 via a conductive member (not shown) such as a bonding wire.

[0044] The encapsulating resin body 44 encapsulates the semiconductor chip 43. The encapsulating resin body 44 forms the outer contour of the semiconductor package 41. A part of each of the island 421 and the terminal 422 is encapsulated by the encapsulating resin body 44. The encapsulating resin body 44 may be referred to as a molding resin, an encapsulant, etc.

[0045] <Warpage of the semiconductor package> Next, with reference to FIG. 6, the warpage of the semiconductor package will be described. FIG. 6 shows the relationship between the amount of shrinkage and the warpage when the temperature decreases. The solid line with inward arrows at both ends indicates the magnitude of shrinkage (shrinkage amount). The two-dot chain line indicates the warpage shape of the semiconductor package when the temperature decreases. FIG. 6 corresponds to FIG. 5.

[0046] The semiconductor package 41 warps during temperature fluctuations due to the difference in the linear expansion coefficients of its components. In the semiconductor package 41 illustrated in FIG. 5, the linear expansion coefficient of Cu that constitutes the lead frame 42 is approximately 16 ppm / °C, and the linear expansion coefficient of Si that constitutes the semiconductor chip 43 is approximately 3 ppm / °C. Therefore, when the temperature decreases, the lead frame 42 shrinks significantly in the direction orthogonal to the Z direction. On the other hand, the amount of shrinkage of the semiconductor chip 43 is small. Thus, as indicated by the dashed-dotted line in FIG. 6, the outer peripheral portion of the semiconductor package 41 warps convex downward, so-called C- warpage occurs.

[0047] Note that the strength of the encapsulation resin body 44 is weaker than that of Cu and Si. Also, the linear expansion coefficient of the encapsulation resin body 44 is generally selected to be 8 to 14 ppm / °C, which is approximately the intermediate value between Cu and Si, so as to approach the linear expansion coefficient of the printed circuit board 30. Therefore, the C- warpage cannot be eliminated by the encapsulation resin body 44. When the temperature decreases, C- warpage occurs in the semiconductor package 41.

[0048] Here, the case of temperature decrease has been exemplified, but the same applies during temperature increase. Due to the above-described difference in linear expansion coefficients, the lead frame 42 expands significantly during temperature increase. On the other hand, the amount of expansion of the semiconductor chip 43 is small. Thus, the outer peripheral portion warps convex upward, so-called smile warpage occurs.

[0049] <Effect on the warpage of the printed circuit board and the mounting portion of the semiconductor package> Next, based on FIGS. 7 to 10, the warpage of the printed circuit board will be described. Also, the relationship between the warpage of the printed circuit board and the warpage of the semiconductor package, and the influence on the mounting portion of the semiconductor package will be described. FIGS. 7 to 10 show reference examples. The reference examples are different from the present embodiment in that stress relaxation portions such as slits are not provided on the printed circuit board. In the reference examples, an "r" is added to the end of the reference numerals of the related elements of the present embodiment. FIGS. 7 to 10 correspond to FIG. 4. However, for the sake of convenience, the heat dissipation gel is omitted. Similar to FIG. 6, the solid line with inward arrows at both ends indicates the magnitude of shrinkage (shrinkage amount). The two-dot chain line indicates the warpage shape of the printed circuit board when the temperature decreases. The dashed line indicates the warpage shape of the semiconductor package when the temperature decreases.

[0050] In the reference example shown in FIG. 7, the case 21r, which is a fixed structure, is formed using Al. The linear expansion coefficient of Al constituting the case 21r is 21 to 23 ppm / °C, and the linear expansion coefficient of the printed circuit board 30r is approximately 14 ppm / °C. Therefore, when the temperature decreases with the printed circuit board 30r fixed to the case 21r, the case 21r (opposing wall 211r) shrinks significantly in the direction perpendicular to the Z direction. On the other hand, the shrinkage amount of the printed circuit board 30r is small. Therefore, the outer peripheral portion of the printed circuit board 30r warps convex upward, so-called smile warpage occurs.

[0051] The semiconductor package 41r is disposed on one surface 301r of the printed circuit board 30r. The semiconductor package 41r has the same configuration as the semiconductor package 41 shown in FIG. 5. Therefore, when the temperature decreases, the semiconductor package 41r warps concave downward at the outer peripheral end as indicated by the dashed line, so-called cry warpage occurs. Therefore, the warpage of the printed circuit board 30r is forcibly changed to the cry warpage shape at the portion where the semiconductor package 41r is mounted.

[0052] As described above, when the direction of the warp of the printed circuit board 30r and the direction of the warp of the semiconductor package 41r due to the difference in the linear expansion coefficients of the case 21r and the printed circuit board 30r are along the Z direction and opposite to each other, a sudden deformation stress is applied to the mounting portion (soldering joint portion) of the semiconductor package 41r. Specifically, when the temperature drops, the case 21r shrinks and pulls the printed circuit board 30r, causing displacement between the fixing portions 315r (fixing holes) of the printed circuit board 30r, and deforming in the direction in which the distance between the fixing portions 315r becomes shorter. The stress caused by this deformation acts on the semiconductor package 41r starting from the fixing portions 315r (fixing holes). In particular, in an environment where the temperature change is large, such as in in-vehicle products, and there are many cold and heat cycles, the connection reliability of the mounting portion is likely to decrease. That is, the solder life is likely to decrease.

[0053] When the temperature rises, the case 21r expands more than the printed circuit board 30r, so a smile warp occurs in the printed circuit board 30r. As described above, a smile warp occurs in the semiconductor package 41r. The semiconductor package 41r is arranged on one surface 301r, and the directions of the warps are opposite. Therefore, the connection reliability of the mounting portion of the semiconductor package 41r is likely to decrease.

[0054] In the reference example shown in FIG. 8, the semiconductor package 41r is arranged on the back surface 302r of the printed circuit board 30r. Other configurations are the same as those in the reference example shown in FIG. 7. When the temperature drops, a smile warp occurs in the printed circuit board 30r due to the difference in the linear expansion coefficients of the case 21r and the printed circuit board 30r.

[0055] When the temperature drops, a cli warp with a downward convex outer peripheral end occurs in the semiconductor package 41r as shown by the broken line. However, the semiconductor package 41r is arranged on the back surface 302r. For this reason, the directions of the warps of the printed circuit board 30r and the semiconductor package 41r are the same (common direction). Therefore, it is possible to suppress the application of a sudden deformation stress to the mounting portion (soldering joint portion) of the semiconductor package 41r.

[0056] Note that when the temperature rises, a C - shaped warp occurs in the printed circuit board 30r. A smile - shaped warp occurs in the semiconductor package 41r. The semiconductor package 41r is disposed on the back surface 302r, and the directions of the warps are the same. Therefore, it is possible to suppress the application of a rapid deformation stress to the mounting portion of the semiconductor package 41r.

[0057] In the reference example shown in FIG. 9, the case 21r, which is a fixed structure, is formed using Fe. The linear expansion coefficient of Fe constituting the case 21r is 10 - 12 ppm / °C, which is smaller than the linear expansion coefficient of the printed circuit board 30r (approximately 14 ppm / °C). When the temperature decreases, the printed circuit board 30r shrinks significantly in the direction orthogonal to the Z - direction. On the other hand, the amount of shrinkage of the case 21r (opposing wall 211r) is small. Therefore, a downward - convex warp, so - called C - shaped warp, occurs in the outer peripheral portion of the printed circuit board 30r.

[0058] When the temperature decreases, a C - shaped warp with the outer peripheral end convex downward as indicated by the dashed line occurs in the semiconductor package 41r. The semiconductor package 41r is disposed on one surface 301r of the printed circuit board 30r as in FIG. 7. For this reason, the directions of the warps of the printed circuit board 30r and the semiconductor package 41r become the same. Therefore, it is possible to suppress the application of a rapid deformation stress to the mounting portion (soldering joint portion) of the semiconductor package 41r.

[0059] Note that when the temperature rises, a smile - shaped warp occurs in the printed circuit board 30r. A smile - shaped warp occurs in the semiconductor package 41r. The semiconductor package 41r is disposed on one surface 301r, and the directions of the warps are the same. Therefore, it is possible to suppress the application of a rapid deformation stress to the mounting portion of the semiconductor package 41r.

[0060] In the reference example shown in FIG. 10, the semiconductor package 41r is disposed on the back surface 302r of the printed circuit board 30r. Other configurations are the same as those of the reference example shown in FIG. 9. When the temperature decreases, due to the difference in the linear expansion coefficients between the case 21r and the printed circuit board 30r, a warpage occurs in the printed circuit board 30r. When the temperature decreases, the semiconductor package 41r has a warpage with the outer peripheral end convex downward as shown by the dashed line. However, the semiconductor package 41r is disposed on the back surface 302r. Therefore, the directions of warpage of the printed circuit board 30r and the semiconductor package 41r are opposite to each other. Thus, the connection reliability of the mounting portion of the semiconductor package 41r is likely to decrease.

[0061] Note that when the temperature rises, since the case 21r expands less than the printed circuit board 30r, a smile warpage occurs in the printed circuit board 30r. The semiconductor package 41r has a smile warpage. The semiconductor package 41r is disposed on the back surface 302r, and the directions of warpage are opposite to each other. Thus, the connection reliability of the mounting portion of the semiconductor package 41r is likely to decrease.

[0062] As described above, it has been found that the relationship between the warpage of the printed circuit board 30r based on the difference in the linear expansion coefficient from the fixed structure and the direction of warpage of the semiconductor package 41r based on the difference in the linear expansion coefficient of the components is important for the connection reliability of the mounting portion of the semiconductor package 41r. For example, it has been found that when the directions of warpage are opposite, stress concentrates on the mounting portion of the semiconductor package 41r and the connection reliability decreases.

[0063] <Effect of stress relaxation portion> Next, based on FIGS. 11 and 12, the effect of the stress relaxation portion will be described. FIGS. 11 and 12 both show simulation results. FIG. 11 shows the warpage amount characteristics of the printed circuit board when the temperature decreases from 20°C to -40°C when the directions of warpage of the printed circuit board and the semiconductor package are different.

[0064] As a configuration with different warpage directions, a printed circuit board was fixed to a case (housing) made of Al, and a semiconductor package was arranged on one surface of the printed circuit board, that is, the same configuration as shown in Fig. 7 was used. Then, the warpage amount (variation in depth dimension) of the printed circuit board was sampled along the diagonal line of the printed circuit board. In Fig. 11, the case without a slit (stress relaxation portion) is shown by a solid line, the case with a small slit is shown by a broken line, and the case with a large slit is shown by a two-dot chain line. Note that the size of the slit indicates the length of the slit. The small slit corresponds to the configuration shown in Fig. 2. The large slit corresponds to the configuration shown in Fig. 3.

[0065] Since the case, which is a fixing structure, is formed using Al, when the temperature decreases, a smile warpage occurs in the printed circuit board based on the difference in the linear expansion coefficients between the case and the printed circuit board. Also, a cli warpage occurs in the semiconductor package. Since the semiconductor package is arranged on one surface of the printed circuit board, the warpage directions of the printed circuit board and the semiconductor package are opposite. When no slit (stress relaxation portion) is provided, it is clear from the result shown by the solid line in Fig. 11 that what was a smile warpage from the fixing hole (fixing portion) has rapidly deformed into a cli warpage. That is, it is clear that a rapid deformation stress is applied to the mounting portion (soldering portion) of the semiconductor package, which is the boundary between the smile warpage and the cli warpage.

[0066] When a small slit is provided, it is clear from the result shown by the broken line in Fig. 11 that it bends rapidly around the fixing hole and the warpage amount is reduced, that is, the stress is relaxed. Also, it is clear that the printed circuit board becomes almost flat in the region closer to the center of the board than the slit. When a large slit is provided, the effect of the slit becomes more prominent. It is clear from the result shown by the two-dot chain line in Fig. 11 that the effect of stress relaxation and the effect of making the central region flat are further enhanced.

[0067] Figure 12 shows the warp amount characteristics of the printed circuit board when the temperature drops from 20°C to -40°C with the same warp direction. As a configuration with the same warp direction, a printed circuit board was fixed to a case (housing) made of Al, and a semiconductor package was arranged on the back surface of the printed circuit board, that is, the same configuration as shown in Fig. 8 was used. Then, the warp amount of the printed circuit board was sampled along the diagonal. In Fig. 12, no slit (stress relaxation part) is shown by a solid line, a small slit is shown by a broken line, and a large slit is shown by a two-dot chain line. Also, for comparison, the result without a slit shown in Fig. 11 is shown by a one-dot chain line.

[0068] When the temperature drops, a smile warp occurs on the printed circuit board based on the difference in the linear expansion coefficients of the case and the printed circuit board. Also, a cry warp occurs in the semiconductor package. Since the semiconductor package is arranged on the back surface of the printed circuit board, the warp direction of the printed circuit board and the warp direction of the semiconductor package are the same. When no slit (stress relaxation part) is provided, it is clear from the result shown by the solid line in Fig. 12 that it does not deform into a cry warp in the mounting area of the semiconductor package and becomes a smile warp throughout the area. That is, it is clear that no sudden deformation stress is applied to the mounting part (soldering joint) of the semiconductor package. This point is also clear from the comparison between the solid line and the one-dot chain line shown in Fig. 12.

[0069] When a small slit is provided, it is clear from the result shown by the broken line in Fig. 12 that it bends suddenly around the fixing hole and the warp amount is reduced. Also, it is clear that the printed circuit board becomes almost flat in the area on the center side of the substrate compared to the slit. When a large slit is provided, it is clear from the result shown by the two-dot chain line in Fig. 12 that the effect of flattening the central area is further enhanced. Note that the results of the small slit and the large slit were almost the same in Figs. 11 and 12.

[0070] <Summary of the First Embodiment> According to this embodiment, as shown in FIGS. 1 and 4, the linear expansion coefficient of the case 21, which is a fixed structure, is larger than that of the printed circuit board 30. For example, when the temperature decreases, a smile warp with the outer peripheral portion convex upward occurs in the printed circuit board 30 as in the configuration shown in FIG. 7. The semiconductor package 41 includes a lead frame 42, a semiconductor chip 43 disposed on the lead frame 42, and a sealing resin body 44. Therefore, when the temperature decreases, a clipless warp with the outer peripheral end convex downward occurs in the semiconductor package 41 as shown in FIG. 6. The semiconductor package 41 is disposed on one surface 301 of the printed circuit board 30, and the warp direction of the printed circuit board 30 and the warp direction of the semiconductor package 41 are opposite when the temperature decreases.

[0071] For example, when the temperature rises, a clipless warp occurs in the printed circuit board 30. A smile warp occurs in the semiconductor package 41. The semiconductor package 41 is disposed on one surface 301, and the warp directions are opposite.

[0072] In such a configuration where the warp directions are opposite when the temperature fluctuates, a stress relaxation portion 32 is provided in the printed circuit board 30. The stress relaxation portion 32 relaxes the stress acting on the mounting portion (soldering joint portion) of the semiconductor package 41 due to the different warp directions. Therefore, the connection reliability of the semiconductor package 41 can be improved.

[0073] As illustrated, a non-lead package may be used as the semiconductor package 41. In the case of a non-lead package, since there are no leads protruding from the encapsulation resin body 44, stress relaxation due to elastic deformation of the leads cannot be achieved. Compared with packages having leads, the connection reliability is likely to decrease due to the application of stress. That is, the solder life is likely to decrease. In particular, in an environment where the temperature change is large, such as in in-vehicle products, and there are many thermal cycles, the connection reliability is likely to decrease. By providing the stress relaxation portion 32 in a configuration where the direction of warping is reversed while adopting the non-lead type semiconductor package 41, the connection reliability of the non-lead type semiconductor package 41 can be improved. Further, by using a non-lead package, the size of the printed circuit board 30, and thus the size of the electronic device 10, can be reduced.

[0074] Note that, as the semiconductor package 41, a package having leads protruding from the encapsulation resin body 44 may be adopted. Due to the effect of the stress relaxation portion 32, a part of the stress acting on the mounting portion of the semiconductor package 41 can be relaxed because the direction of warping is different. The other part of the stress can be relaxed by the elastic deformation of the leads.

[0075] As illustrated, the stress relaxation portion 32 may be provided around the fixing hole 31 (fixing portion 315). By providing it around the fixing hole 31 (fixing portion 315) which is the starting point of the stress, it becomes easier to reduce the stress.

[0076] As illustrated, the stress relaxation portion 32 may be configured to include a portion that relaxes stress by elastic deformation. By elastically deforming (spring-deforming), the stress acting on the mounting portion of the semiconductor package 41 can be effectively relaxed.

[0077] As illustrated, the stress relaxation portion 32 may be configured to include a slit 321 provided individually for the fixing hole 31 and a partitioning portion 322. Since the slit 321 penetrates the printed circuit board 30, the transmission of stress can be blocked by the slit 321. That is, the transmission range of stress can be restricted. The partitioning portion 322 partitioned by the slit 321 elastically deforms due to the application of stress. The stress can be relaxed by the elastic deformation of the partitioning portion 322.

[0078] As illustrated, the slit 321 may be arranged so as to cross at least one of a plurality of virtual straight lines L1, L2, L3, L4, L5, L6 that virtually connect different fixing holes 31 to each other. Displacement is applied between the fixing holes 31 with temperature fluctuations, and deformation stress acts starting from the fixing holes 31. Therefore, by arranging the slit 321 so as to cross the virtual straight line, the displacement between the fixing holes 31 can be suppressed, and the stress acting on the mounting portion of the semiconductor package 41 can be relaxed.

[0079] Preferably, at least one slit 321 is arranged so as to cross all the virtual straight lines L1, L2, L3, L4, L5, L6. Since the slit 321 is always positioned between the fixing holes 31, the stress acting on the mounting portion of the semiconductor package 41 can be effectively relaxed.

[0080] As illustrated, the slit 321 may be provided so as to open to the side surface of the printed circuit board 30. When the slit 321 is provided up to the end of the printed circuit board 30 in this way, it is easy to restrict the stress transmission range. Further, the connection portion between the partitioning portion 322 and the mounting area becomes one place, and the partitioning portion 322 is easily elastically deformed.

[0081] As illustrated, in the printed circuit board 30 having a substantially rectangular planar shape, the slit 321 may be provided so as to open to the first side surface and extend from the first side surface toward the second side surface opposite to the first side surface. According to this, the width of the partitioning portion 322 becomes narrow and long, and it becomes easy to elastically deform. Therefore, the stress acting on the mounting portion of the semiconductor package 41 can be effectively relaxed.

[0082] <Modification Example> The arrangement of the semiconductor package 41 is not limited to one surface 301. For example, as shown in FIG. 13, in a configuration where the semiconductor package 41 is provided on the back surface 302, a stress relaxation portion 32 may be provided on the printed circuit board 30. In FIG. 13, the case 21 is formed using Fe. Therefore, for example, when the temperature decreases, a warpage occurs in the printed circuit board 30. Although warpage occurs in the semiconductor package 41, since it is arranged on the back surface 302, the direction of warpage of the printed circuit board 30 and the direction of warpage of the semiconductor package 41 are opposite during temperature fluctuations. By providing the stress relaxation portion 32, the stress acting on the mounting portion (soldering joint portion) of the semiconductor package 41 can be relaxed, and the connection reliability can be improved.

[0083] In the configuration shown in FIG. 13, when the temperature rises, a smile warpage occurs in the printed circuit board 30. A smile warpage occurs in the semiconductor package 41. The semiconductor package 41 is arranged on the back surface 302, and the direction of warpage is opposite. By providing the stress relaxation portion 32, the stress acting on the mounting portion (soldering joint portion) of the semiconductor package 41 can be relaxed, and the connection reliability can be improved. Note that in the configuration shown in FIG. 13, a heat dissipation gel 60 may be arranged between the semiconductor package 41 and a cover 22 (not shown).

[0084] Although an example of Al is shown as the material of the case 21 having a linear expansion coefficient larger than that of the printed circuit board 30, it is not limited thereto. For example, resin materials such as PPS and PBT may be used. Although an example of Fe is shown as the material of the case 21 having a linear expansion coefficient smaller than that of the printed circuit board 30, it is not limited thereto. For example, ceramics or the like may be used.

[0085] As shown in FIG. 14, fixing holes 33 for reinforcing the fixing of the printed circuit board 30 to the case 21 (fixed structure) may be provided in the printed circuit board 30. The fixing hole 31 corresponds to the first fixing hole, and the fixing hole 33 corresponds to the second fixing hole. By providing the fixing holes 33, the mounting strength to the case 21 can be increased. The fixing holes 33 are provided in a region 34 surrounded by all the slits 321. The region 34 is a region that blocks the transmission of stress starting from the fixing hole 31 with the slits 321. The fixing holes 33 are arranged between the slits 321. In the example shown in FIG. 14, the fixing holes 33 are provided in the central region of the board. No stress starting from the fixing hole 31 is transmitted to the fixing holes 33 provided in the region 34. Therefore, the slits 321 are not required for the fixing holes 33, and the fixing holes 33 function as holes for improving the mounting strength between the printed circuit board 30 and the case 21.

[0086] The shape and arrangement of the slits 321 are not limited to the above example. For example, as shown in FIG. 15, non - continuously provided slits 321 may be employed. The slits 321 are divided into a plurality in the extending direction. Also, as shown in FIG. 16, the slits 321 may be arranged in multiple layers. The slits 321 are arranged in multiple layers in the radial direction from the fixing hole 31.

[0087] (Second Embodiment) This embodiment is a modified example based on the preceding embodiment, and the description of the preceding embodiment can be incorporated by reference. In the preceding embodiment, in the semiconductor package, the upper surface of the semiconductor chip was covered with a sealing resin body. Instead, a semiconductor package having a configuration in which a metal plate material is arranged on the semiconductor chip may be used.

[0088] <Semiconductor Package and Warpage> FIG. 17 is a cross-sectional view showing an example of a semiconductor package in the electronic device according to this embodiment. FIG. 17 corresponds to FIG. 5. In FIG. 17, similar to FIG. 6, the relationship between the amount of shrinkage and the warp during temperature drop is shown. The solid line with inward arrows at both ends indicates the magnitude of shrinkage (amount of shrinkage). The two-dot chain line indicates the warped shape of the semiconductor package during temperature drop.

[0089] The semiconductor package 41 is a QFN-type leadless package, similar to the previous embodiment. The semiconductor package 41 includes a lead frame 42, a semiconductor chip 43, and a sealing resin body 44, similar to the configuration shown in the previous embodiment (see FIG. 5). The semiconductor package 41 of this embodiment further includes a clip 45 made of a metal plate material. The sealing resin body 44 seals the clip 45 together with the semiconductor chip 43.

[0090] The clip 45 is formed using a metal material with good conductivity such as Cu. The clip 45 is mounted on the semiconductor chip 43. Such a structure is used for power semiconductors that conduct large currents such as power MOS. The semiconductor chip 43 of this embodiment has a MOSFET formed on a semiconductor substrate. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. In the semiconductor chip 43, a drain electrode is formed on the lower surface facing the lead frame 42, and a source electrode is formed on the upper surface. The clip 45 is solder-bonded to the source electrode.

[0091] When the clip 45 is thicker than the lead frame 42 and / or the clip 45 is larger than the island 421, the effect of the clip 45 becomes stronger than that of the lead frame 42 on the semiconductor chip 43 during expansion and contraction. For example, when the temperature drops, even if the materials of the lead frame 42 and the clip 45 are both Cu, the shrinkage strength on the clip 45 side becomes stronger. Therefore, in the semiconductor package 41, a smile warp with the outer peripheral portion convex upward occurs as shown by the two-dot chain line. When the temperature rises, a cli warp with the outer peripheral portion convex downward occurs in the semiconductor package 41.

[0092] In the above package structure, since Si is sandwiched between Cu, the influence of the semiconductor chip 43 can be offset. In particular, when the thickness of the clip 45 is increased, the strength on the clip 45 side becomes stronger than that of the lead frame 42, so that it is deformed by being pulled to the clip 45 side. The strength is proportional to the cube of the thickness.

[0093] <Influence on the warp of the printed circuit board and the mounting portion of the semiconductor package> Next, based on FIGS. 18 to 21, the warp of the printed circuit board will be described. Also, the relationship between the warp of the printed circuit board and the warp of the semiconductor package and the influence on the mounting portion of the semiconductor package will be described. FIGS. 18 to 21 show reference examples. FIGS. 18 to 21 correspond to FIGS. 7 to 10. The reference example is different from the present embodiment in that a stress relaxation portion such as a slit is not provided on the printed circuit board. In the reference example, an r is added to the end of the reference numerals of the related elements of the present embodiment. The solid line with inward arrows at both ends indicates the magnitude of shrinkage (shrinkage amount). The two-dot chain line indicates the warp shape of the printed circuit board when the temperature drops. The broken line indicates the warp shape of the semiconductor package when the temperature drops.

[0094] In the reference example shown in FIG. 18, the case 21r which is a fixed structure is formed using Al. When the temperature drops, the case 21r (opposing wall 211r) shrinks greatly in the direction orthogonal to the Z direction. On the other hand, the shrinkage amount of the printed circuit board 30r is small. A smile warp with the outer peripheral portion convex upward occurs in the printed circuit board 30r.

[0095] The semiconductor package 41r has the same configuration as the semiconductor package 41 shown in FIG. 17. When the temperature decreases, a smile warp with an upwardly convex outer peripheral end occurs in the semiconductor package 41r as indicated by the broken line. The semiconductor package 41r is disposed on one surface 301r. For this reason, the direction of warping of the printed circuit board 30r and the direction of warping of the semiconductor package 41r become the same. Therefore, it is possible to suppress the application of a sudden deformation stress to the mounting portion (soldering joint portion) of the semiconductor package 41r.

[0096] When the temperature rises, a C-shaped warp occurs in the printed circuit board 30r. A C-shaped warp occurs in the semiconductor package 41r. The semiconductor package 41r is disposed on one surface 301r, and the directions of warping are the same. Therefore, it is possible to suppress the application of a sudden deformation stress to the mounting portion of the semiconductor package 41r.

[0097] In the reference example shown in FIG. 19, the semiconductor package 41r is disposed on the back surface 302r of the printed circuit board 30r. Other configurations are the same as those in the reference example shown in FIG. 18. When the temperature decreases, due to the difference in the linear expansion coefficients between the case 21r and the printed circuit board 30r, a smile warp occurs in the printed circuit board 30r.

[0098] When the temperature decreases, a smile warp with an upwardly convex outer peripheral end occurs in the semiconductor package 41r as indicated by the broken line. The semiconductor package 41r is disposed on the back surface 302r. For this reason, the direction of warping of the printed circuit board 30r and the direction of warping of the semiconductor package 41r become opposite to each other. Therefore, a sudden deformation stress is applied to the mounting portion (soldering joint portion) of the semiconductor package 41r, and the connection reliability of the mounting portion of the semiconductor package 41r is likely to decrease.

[0099] When the temperature rises, a C-shaped warp occurs in the printed circuit board 30r. A C-shaped warp also occurs in the semiconductor package 41r. The semiconductor package 41r is disposed on the back surface 302r, and the direction of the warp is reversed. Therefore, the connection reliability of the mounting portion of the semiconductor package 41r is likely to decrease.

[0100] In the reference example shown in FIG. 20, the case 21r, which is a fixing structure, is formed using Fe. When the temperature decreases, the printed circuit board 30r shrinks significantly in the direction orthogonal to the Z direction. On the other hand, the amount of shrinkage of the case 21r (opposing wall 211r) is small. A C-shaped warp with a downward convex outer peripheral portion occurs in the printed circuit board 30r.

[0101] When the temperature decreases, a smile warp with an upward convex outer peripheral end occurs in the semiconductor package 41r as shown by the broken line. The semiconductor package 41r is disposed on one surface 301r of the printed circuit board 30r. For this reason, the direction of the warp of the printed circuit board 30r and the direction of the warp of the semiconductor package 41r are reversed. Therefore, the connection reliability of the mounting portion of the semiconductor package 41r is likely to decrease.

[0102] When the temperature rises, a smile warp occurs in the printed circuit board 30r. A C-shaped warp occurs in the semiconductor package 41r. The semiconductor package 41r is disposed on one surface 301r, and the direction of the warp is reversed. Therefore, the connection reliability of the mounting portion of the semiconductor package 41r is likely to decrease.

[0103] In the reference example shown in FIG. 21, the semiconductor package 41r is disposed on the back surface 302r of the printed circuit board 30r. Other configurations are the same as those of the reference example shown in FIG. 20. When the temperature decreases, due to the difference in the coefficient of linear expansion between the case 21r and the printed circuit board 30r, a smile warp occurs in the printed circuit board 30r. When the temperature decreases, the semiconductor package 41r has a smile warp with the outer peripheral end convex upward as shown by the dashed line. Since the semiconductor package 41r is disposed on the back surface 302r, the direction of the warp of the printed circuit board 30r and the direction of the warp of the semiconductor package 41r are the same. Therefore, it is possible to suppress the application of a sudden deformation stress to the mounting portion (soldering portion) of the semiconductor package 41r.

[0104] Note that when the temperature rises, a smile warp occurs in the printed circuit board 30r. A cli warp occurs in the semiconductor package 41r. The semiconductor package 41r is disposed on the back surface 302r, and the directions of the warps are the same. Therefore, it is possible to suppress the application of a sudden deformation stress to the mounting portion (soldering portion) of the semiconductor package 41r.

[0105] FIGS. 22 to 26 show the simulation results of the deformation accompanying temperature fluctuations. FIGS. 22, 23, and 24 show the simulation results when the temperature changes to a low temperature in the same structural model as the reference example shown in FIG. 18. FIG. 22 is a side view of the electronic device as viewed from the Y direction. FIG. 23 shows the warp of the printed circuit board. FIG. 24 shows the warp of the semiconductor package.

[0106] In the electronic device 10r, the semiconductor package 41r is disposed on one surface 301r of the printed circuit board 30r. The case 21r is formed using Al, and as shown in FIGS. 22 and 23, a smile warp occurs in the printed circuit board 30r during low temperature fluctuations. As shown in FIGS. 23 and 24, a smile warp occurs in the semiconductor package 41r. It is clear that the directions of the warps are the same.

[0107] Figs. 25 and 26 show the simulation results when the temperature changes to low temperature in a structural model with slits (stress relaxation parts) added to Figs. 22 to 24. Fig. 25 is a side view of the electronic device seen from the Y direction. Fig. 25 corresponds to Fig. 22. Fig. 26 shows the warp of the printed circuit board.

[0108] As shown in Fig. 26, slits 321r and partition parts 322r are provided at the four corners of the printed circuit board 30r. As shown in Figs. 25 and 6, it is clear that even if displacement is applied to the fixing holes of the printed circuit board 30r, the deformation can be absorbed by providing the slits 321r and the partition parts 322r.

[0109] Regarding the semiconductor package structure shown in Fig. 17, a simulation was also performed on the warp amount characteristics of the printed circuit board when the temperature dropped from 20°C to -40°C. The simulation was carried out at three levels of no slit (stress relaxation part), small slit, and large slit for each of the cases where the warp direction of the printed circuit board is different from the warp direction of the semiconductor package and the cases where the warp directions are the same. Although not shown in the drawings, the same results as in the prior embodiment (see Figs. 11 and 12) were obtained.

[0110] <Electronic device> Fig. 27 shows an example of the electronic device according to this embodiment. Fig. 27 corresponds to Fig. 4. In Fig. 27, for the sake of convenience, only the case, which is a fixing structure, of the housing is shown. Also, the case is shown in a simplified manner. As the electronic component, only the semiconductor package is shown. Also, the screw holes, fixing holes, and screws are omitted.

[0111] As shown in FIG. 27, the electronic device 10 includes a semiconductor package 41 having the structure shown in FIG. 17. The semiconductor package 41 is disposed on the back surface 302 of the printed circuit board 30. The case 21, which is a fixing structure, is formed using Al. The printed circuit board 30 has a stress relaxation portion 32. The stress relaxation portion 32 includes a slit 321 and a partitioning portion 322 as shown in the previous embodiment. The stress relaxation portion 32 has the same configuration as the configuration shown in the previous embodiment (see FIGS. 2 and 3). The stress relaxation portion 32 is provided individually for each fixing portion 315 (fixing hole). In the configuration shown in FIG. 27, a heat dissipation gel 60 may be disposed between the semiconductor package 41 and a cover 22 (not shown). Other configurations are the same as those shown in the previous embodiment.

[0112] <Summary of the Second Embodiment> According to the electronic device 10 of the present embodiment, the same effects as those of the electronic device 10 shown in the previous embodiment can be achieved. For example, in the configuration shown in FIG. 27, the linear expansion coefficient of the case 21, which is a fixing structure, is larger than the linear expansion coefficient of the printed circuit board 30. For example, when the temperature decreases, the printed circuit board 30 has a smile warp in which the outer peripheral portion is convex upward, similar to the configuration shown in FIG. 19. The semiconductor package 41 includes a clip 45 (metal plate material) disposed on the semiconductor chip 43, and a smile warp occurs when the temperature decreases as shown in FIG. 17. The semiconductor package 41 is disposed on the back surface 302 of the printed circuit board 30, and the direction of warping of the printed circuit board 30 and the direction of warping of the semiconductor package 41 are opposite when the temperature decreases.

[0113] For example, when the temperature rises, a cli warp occurs in the printed circuit board 30. A cli warp occurs in the semiconductor package 41. The semiconductor package 41 is disposed on the back surface 302, and the direction of warping is opposite.

[0114] In a configuration where the direction of warping during temperature fluctuations is reversed in this way, a stress relaxation portion 32 is provided on the printed circuit board 30. The stress relaxation portion 32 relaxes the stress acting on the mounting portion (soldering portion) of the semiconductor package 41 due to the different directions of warping. Therefore, the connection reliability of the semiconductor package 41 can be improved.

[0115] The appearance of the semiconductor package shown in the previous embodiment (see FIG. 5) and the appearance of the semiconductor package of this embodiment (see FIG. 17) appear to be almost the same. However, due to the difference in the internal structure, the direction of warping when the temperature changes is reversed. Thus, even for semiconductor packages 41 that appear the same in appearance, the direction of warping when the temperature changes may be different. However, based on the findings obtained, in a configuration where the direction of warping during temperature fluctuations is reversed, a stress relaxation portion 32 is provided on the printed circuit board 30. Without arbitrarily providing a stress relaxation portion, the connection reliability of the semiconductor package 41 can be improved.

[0116] <Modification Example> The arrangement of the semiconductor package 41 is not limited to the back surface 302. For example, as shown in FIG. 28, in a configuration where the semiconductor package 41 is provided on one surface 301, a stress relaxation portion 32 may be provided on the printed circuit board 30. In FIG. 28, the case 21 is formed using Fe. For this reason, for example, a curl warping occurs in the printed circuit board 30 when the temperature decreases. A smile warping occurs in the semiconductor package 41. Since the semiconductor package 41 is arranged on one surface 301, the direction of warping of the printed circuit board 30 and the direction of warping of the semiconductor package 41 during temperature fluctuations are reversed. By providing the stress relaxation portion 32, the stress acting on the mounting portion (soldering portion) of the semiconductor package 41 can be relaxed, and the connection reliability can be improved.

[0117] In the configuration shown in FIG. 28, when the temperature rises, a smile warp occurs on the printed circuit board 30. A cli warp occurs in the semiconductor package 41. The semiconductor package 41 is disposed on one surface 301, and the direction of the warp is reversed. By providing the stress relaxation portion 32, the stress acting on the mounting portion (soldering portion) of the semiconductor package 41 can be relaxed, and the connection reliability can be improved. In the configuration shown in FIG. 28, a heat dissipation gel 60 may be disposed between the semiconductor package 41 and the case 21.

[0118] (Third Embodiment) This embodiment is a modification example based on the preceding embodiment, and the description of the preceding embodiment can be incorporated. In the preceding embodiment, the semiconductor package included only one semiconductor chip. Instead, a multi-chip package may be used as the semiconductor package.

[0119] <Semiconductor Package> FIG. 29 is a cross-sectional view showing an example of a semiconductor package in the electronic device according to this embodiment. FIG. 29 corresponds to FIG. 17. In FIG. 29, similar to FIG. 17, the relationship between the shrinkage amount and the warp during temperature drop is shown. The solid line with inward arrows at both ends indicates the magnitude of shrinkage (shrinkage amount). The two-dot chain line indicates the warp shape of the semiconductor package during temperature drop.

[0120] The semiconductor package 41 shown in FIG. 29 is a QFN type non-lead package, similar to the preceding embodiment. The semiconductor package 41 has a structure in which the configurations shown in FIG. 5 and FIG. 17 are arranged side by side in a common (single) package. The semiconductor package 41 includes a lead frame 42, semiconductor chips 43A and 43B, a sealing resin body 44, and a clip 45. A power MOSFET for driving a large current is formed in the semiconductor chip 43B. A control IC for controlling the driving of the MOSFET of the semiconductor chip 43B is formed in the semiconductor chip 43A. Such a semiconductor package 41 is sometimes referred to as an IPD.

[0121] The semiconductor chip 43A corresponds to the semiconductor chip 43 shown in FIG. 5. The semiconductor chip 43A is disposed on one of the islands 421 of the lead frame 42. Pads (not shown) are formed on the upper surface of the semiconductor chip 43A, and the pads are electrically connected to the terminals 422 via bonding wires. The upper surface of the semiconductor chip 43A is covered with a sealing resin body 44. The semiconductor chip 43B corresponds to the semiconductor chip 43 shown in FIG. 17. A clip 45 is joined to the upper surface of the semiconductor chip 43B. In the example shown in FIG. 32, the semiconductor chip 43B is disposed on an island 421 different from that of the semiconductor chip 43A. Alternatively, the semiconductor chips 43A and 43B may be disposed on a common (single) island 421.

[0122] In the stacked portion including the semiconductor chip 43A, the linear expansion coefficient of Cu constituting the lead frame 42 is larger than the linear expansion coefficient of Si constituting the semiconductor chip 43. Therefore, when the temperature decreases, the lead frame 42 shrinks greatly, and a clipless warp with the outer peripheral portion convex downward occurs. In the stacked portion including the semiconductor chip 43B, the clip 45 is thicker than the lead frame 42 and / or the clip 45 is larger than the island 421. Therefore, when the temperature decreases, even if the materials of both the lead frame 42 and the clip 45 are Cu, the shrinkage strength on the clip 45 side becomes stronger. Thus, a smile warp with the outer peripheral portion convex upward occurs. A clipless warp and a smile warp appear in the single semiconductor package 41.

[0123] The same applies when the temperature rises. When the temperature rises, a smile warp occurs in the stacked portion of the semiconductor chip 43A, and a clipless warp occurs in the stacked portion of the semiconductor chip 43B. A clipless warp and a smile warp appear in the single semiconductor package 41.

[0124] <Electronic device> FIG. 30 shows an example of the electronic device according to the present embodiment. FIG. 30 corresponds to FIG. 4. In FIG. 30, for convenience, only the case, which is a fixed structure, of the housing is shown. Also, the case is shown in a simplified manner. As the electronic component, only the semiconductor package is shown. Also, the screw holes, the fixing holes, the screws, and the heat dissipation gel are omitted.

[0125] As shown in FIG. 30, the electronic device 10 includes the semiconductor package 41 having the structure shown in FIG. 29. The semiconductor package 41 is disposed on one surface 301 of the printed circuit board 30. The case 21, which is a fixed structure, is formed using Al. The printed circuit board 30 has a stress relaxation portion 32. The stress relaxation portion 32 includes, for example, a slit 321 and a partitioning portion 322. The stress relaxation portion 32 has the same configuration as the configuration shown in the previous embodiment (see FIGS. 2 and 3). The stress relaxation portion 32 is provided individually for each fixing portion 315 (fixing hole).

[0126] FIG. 31 shows another example of the electronic device. In FIG. 31, the semiconductor package 41 is disposed on the back surface 302 of the printed circuit board 30. Other configurations are the same as those of the example shown in FIG. 30.

[0127] <Summary of the Third Embodiment> As shown in the present embodiment, a multi-chip package may be adopted as the semiconductor package 41. The multi-chip package has a semiconductor chip 43A on which a clip 45 is not disposed on the upper surface and a semiconductor chip 43B on which a clip 45 (metal plate material) is disposed on the upper surface. In such a configuration, as shown in FIG. 29, a warpage in the opposite direction to the warpage of the printed circuit board 30 exists in the semiconductor package 41 when the temperature fluctuates, whether the semiconductor package 41 is mounted on either the one surface 301 or the back surface 302. By providing the stress relaxation portion 32 regardless of the mounting surface, the stress acting on the mounting portion of the semiconductor package 41 due to the warpage in the opposite direction can be relaxed.

[0128] If the stress relaxation portion 32 is not provided, the connection reliability of the mounting portion of the portion warping in the direction opposite to the warp of the printed circuit board 30 among the stacked portions including the semiconductor chip 43A and the stacked portions including the semiconductor chip 43B decreases. That is, the solder life decreases. As a result, the product life also decreases. By providing the stress relaxation portion 32, the solder life of the portion warping in the opposite direction can be improved, and thus the product life can be improved.

[0129] Note that the electronic device is not limited to the configurations shown in FIGS. 30 and 31. A configuration in which the coefficient of linear expansion of the case 21 is smaller than the coefficient of linear expansion of the printed circuit board 30 may be employed. In this case, regardless of whether the semiconductor package 41 is mounted on either the front surface 301 or the back surface 302, there is a warping portion in the semiconductor package 41 that is opposite to the warp of the printed circuit board 30. Therefore, by providing the stress relaxation portion 32 regardless of the mounting surface, the stress acting on the mounting portion of the semiconductor package 41 due to the reverse warp can be relaxed.

[0130] (Fourth Embodiment) This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be incorporated by reference. In the preceding embodiment, a single semiconductor package was provided. Instead, a configuration in which a plurality of types of semiconductor packages are mounted on a common surface may be employed.

[0131] FIG. 32 shows an example of an electronic device according to this embodiment. FIG. 32 corresponds to FIG. 4. In FIG. 32, for the sake of convenience, only the case, which is a fixed structure among the housings, is shown. Also, the case is shown in a simplified manner. As electronic components, only semiconductor packages are shown. Also, screw holes, fixing holes, screws, and heat dissipation gel are omitted. The broken line shown in FIG. 32 indicates the warping shape of the semiconductor package when the temperature decreases. The two-dot chain line indicates the warping shape of the printed circuit board when the temperature decreases.

[0132] As shown in FIG. 32, the electronic device 10 includes a semiconductor package 41A having the same configuration as that shown in FIG. 5, and a semiconductor package 41B having the same configuration as that shown in FIG. 17. The semiconductor package 41A corresponds to the first semiconductor package, and the semiconductor package 41B corresponds to the second semiconductor package. The semiconductor package 41A includes a lead frame 42A, a semiconductor chip 43A, and a sealing resin body 44A. The lead frame 42A corresponds to the first lead frame, and the semiconductor chip 43A corresponds to the first semiconductor chip. The sealing resin body 44A corresponds to the first sealing resin body. The semiconductor package 41B includes a lead frame 42B, a semiconductor chip 43B, a sealing resin body 44A, and a clip 45. The lead frame 42B corresponds to the second lead frame, and the semiconductor chip 43B corresponds to the second semiconductor chip. The sealing resin body 44B corresponds to the second sealing resin body.

[0133] The two types of semiconductor packages 41A and 41B are arranged on the common surface of the printed circuit board 30. In the example shown in FIG. 32, the semiconductor packages 41A and 41B are arranged on one surface 301. The semiconductor packages 41A and 41B are arranged on the back surface 302. The case 21, which is a fixing structure, is formed using, for example, Al. The printed circuit board 30 has a stress relaxation portion 32. The stress relaxation portion 32 includes, for example, a slit 321 and a partition portion 322. The stress relaxation portion 32 has the same configuration as the configuration shown in the previous embodiment (see FIGS. 2 and 3). The stress relaxation portion 32 is provided individually for each fixing portion 315 (fixing hole).

[0134] <Summary of the Fourth Embodiment> As shown in this embodiment, a semiconductor package 41A (first semiconductor package) and a semiconductor package 41B (second semiconductor package) are arranged on a common surface of the printed circuit board 30. When the temperature fluctuates, one of the semiconductor packages 41A and 41B has a C-shaped warp, and the other has a smile warp. No matter whether the two types of semiconductor packages 41A and 41B are mounted on either the front surface 301 or the back surface 302, the warping direction of one of the semiconductor packages 41A and 41B is opposite to the warping direction of the printed circuit board 30. Therefore, by providing the stress relaxation portion 32 regardless of the mounting surface, the stress acting on the mounting portion of the semiconductor package 41 due to the reverse warp can be relaxed.

[0135] In the configuration shown in FIG. 32, for example, when the temperature decreases, a smile warp occurs in the printed circuit board 30. A C-shaped warp occurs in the semiconductor package 41A, and a smile warp occurs in the semiconductor package 41B. Therefore, among the semiconductor packages 41A and 41B arranged on the front surface 301, the warping direction of the semiconductor package 41A is opposite to the warping direction of the printed circuit board 30. Among the semiconductor packages 41A and 41B arranged on the back surface 302, the warping direction of the semiconductor package 41B is opposite to the warping direction of the printed circuit board 30. Therefore, the semiconductor package 41A arranged on the front surface 301 and the semiconductor package 41B arranged on the back surface 302 correspond to the semiconductor package 41 in which stress acts on the mounting portion due to the different warping directions. By providing the stress relaxation portion 32, the connection reliability between the semiconductor package 41A arranged on the front surface 301 and the semiconductor package 41B arranged on the back surface 302 can be improved. Similar to the multi-chip package, the product life can be improved.

[0136] Note that the electronic device is not limited to the configuration shown in FIG. 32. The two types of semiconductor packages 41A and 41B may be arranged only on one surface 301, or may be arranged only on the back surface 302. The configuration may be such that the linear expansion coefficient of the case 21 is smaller than the linear expansion coefficient of the printed circuit board 30. In this case, in the configuration shown in FIG. 32, the semiconductor package 41B arranged on one surface 301 and the semiconductor package 41A arranged on the back surface 302 correspond to the semiconductor package 41 in which stress acts on the mounting portion due to the different warping directions. By providing the stress relaxation portion 32 regardless of the mounting surface, the stress acting on the mounting portion of the semiconductor package 41 due to the reverse warping can be relaxed.

[0137] (Fifth Embodiment) This embodiment is a modification example based on the preceding embodiment, and the description of the preceding embodiment can be incorporated. In the preceding embodiment, slits and partition portions were provided as stress relaxation portions. Instead of this, grooves and thin portions may be provided.

[0138] FIG. 33 is a cross-sectional view showing a part of the printed circuit board of the electronic device according to this embodiment. In FIG. 33, the periphery of the fixing hole and the stress relaxation portion is shown. The printed circuit board 30 shown in FIG. 33 has a stress relaxation portion 32 provided corresponding to the fixing hole 31, as in the preceding embodiment. The stress relaxation portion 32 is provided individually for a plurality of fixing holes 31. The stress relaxation portion 32 includes a groove 323 and a thin portion 324.

[0139] The groove 323 is a non-penetrating hole extending in a predetermined direction. The groove 323 may open to one surface 301 or may open to the back surface 302. In the example shown in FIG. 33, the groove 323 opening to one surface 301 and the groove 323 opening to the back surface 302 are provided so as to overlap along the extending direction.

[0140] The thin portion 324 is a portion whose thickness is made thinner than the peripheral portion of the groove 323 by the groove 323. The thin portion 324 is provided adjacent to the groove 323 in the Z direction. In the example shown in FIG. 33, the thin portion 324 is sandwiched between the groove 323 that opens to one surface 301 and the groove 323 that opens to the back surface 302. The thin portion 324 connects the portion on the fixing hole 31 side with respect to the groove 323 and the portion on the side opposite to the fixing hole 31 via the groove 323. Due to the application of stress, the thin portion 324 elastically deforms (spring deformation). Since the groove 323 does not penetrate the printed circuit board 30, for example, the groove 323 for the fixing hole 311 may be provided such that one end opens to the side surface 303 and the other end opens to the side surface 304. Other configurations are the same as those shown in the previous embodiment.

[0141] <Summary of the Fifth Embodiment> As shown in this embodiment, the stress relaxation portion 32 may be configured to include a portion that relaxes stress by elastic deformation. By elastically deforming (spring deformation), the stress acting on the mounting portion of the semiconductor package 41 due to the reverse warp can be effectively relaxed.

[0142] As exemplified, the stress relaxation portion 32 may be configured to include an unpenetrated groove 323 and a thin portion 324 adjacent to the groove 323 in the Z direction. The transmission range of stress can be limited by the unpenetrated groove 323. The thin portion 324 adjacent to the groove 323 elastically deforms due to the application of stress. By the elastic deformation of the thin portion 324, the stress can be relaxed.

[0143] The stress relaxation portion 32 including the slit 321 and the partition portion 322 shown in the previous embodiment may be replaced with the stress relaxation portion 32 including the groove 323 and the thin portion 324 shown in this embodiment.

[0144] (Sixth Embodiment) This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be incorporated. In the preceding embodiment, examples including slits and grooves as stress relaxation portions were shown. Instead of this, an extended portion extending from the main body portion may be provided.

[0145] FIG. 34 is a cross-sectional view showing a part of a printed circuit board among the electronic devices according to the present embodiment. The printed circuit board 30 shown in FIG. 34 has a stress relaxation portion 32 provided corresponding to the fixing holes 31, as in the previous embodiment. The stress relaxation portions 32 are provided individually for the plurality of fixing holes 31. The stress relaxation portion 32 includes an extended portion 325 continuous with the main body portion 35.

[0146] The main body portion 35 is the main part of the printed circuit board 30. Conductors such as wiring layers are arranged in the main body portion 35, and electronic components 40 including semiconductor packages 41 are mounted. The printed circuit board 30 has four extended portions 325. Fixing holes 31 are provided in the extended portions 325. The extended portions 325 extend from the main body portion 35 toward the fixing positions with the case 21. The extended portions 325 shown in FIG. 34 extend in one direction. The extended portions 325 extend in the X direction or the Y direction. Due to the application of stress, the extended portions 325 elastically deform (spring deformation). Other configurations are the same as those shown in the previous embodiment.

[0147] <Summary of the Sixth Embodiment> As shown in the present embodiment, the stress relaxation portion 32 may be configured to include a portion that relaxes stress by elastic deformation. By elastically deforming (spring deforming), the stress acting on the mounting portion of the semiconductor package 41 due to the reverse warp can be effectively relaxed.

[0148] As exemplified, the stress relaxation portion 32 may be configured to include an extended portion 325 extending from the main body portion 35 and provided with fixing holes 31. The extended portion 325 elastically deforms due to the application of stress. By the elastic deformation of the extended portion 325, the stress can be relaxed.

[0149] <Modification Example> The shape of the extended portion 325 is not limited to the above example. For example, as shown in FIG. 35, the extended portion 325 may include a first extended portion 3251 and a second extended portion 3252. The first extended portion 3251 extends in a predetermined direction. The second extended portion 3252 is connected to the first extended portion 3251 and extends in a direction different from the predetermined direction. In the example shown in FIG. 35, one of the ends of the first extended portion 3251 is connected to the main body portion 35, and the other end is connected to the second extended portion 3252. For example, the first extended portion 3251 extends in the X direction, and the second extended portion 3252 extends in the Y direction. Also, the first extended portion 3251 extends in the Y direction, and the second extended portion 3252 extends in the X direction. The first extended portion 3251 extends in a direction orthogonal to the side surface of the printed circuit board 30 (main body portion 35). The second extended portion 3252 extends along the side surface of the printed circuit board 30. The extended portion 325 has a substantially L-shaped plane. According to the configuration shown in FIG. 35, the length from the fixing hole 31 to the main body portion 35 becomes longer, and the extended portion 325 is more likely to elastically deform. Also, an increase in size can be suppressed.

[0150] The stress relaxation portion 32 including the slit 321 and the partition portion 322 shown in the previous embodiment may be replaced with the stress relaxation portion 32 including the extended portion 325 shown in this embodiment.

[0151] (Other Embodiments) The disclosure in this specification, drawings, etc. is not limited to the illustrated embodiments. The disclosure includes the illustrated embodiments and modifications by those skilled in the art based on them. For example, the disclosure is not limited to the combination of parts and / or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes those in which parts and / or elements of the embodiments are omitted. The disclosure includes the replacement or combination of parts and / or elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some of the disclosed technical scopes are shown by the description of the claims, and should be understood to include all changes within the meaning and scope equivalent to the description of the claims.

[0152] The disclosure in the specification, drawings, etc. is not limited by the description in the claims. The disclosure in the specification, drawings, etc. encompasses the technical idea described in the claims and further extends to technical ideas that are more diverse and extensive than the technical idea described in the claims. Therefore, various technical ideas can be extracted from the disclosure in the specification, drawings, etc. without being restricted by the description in the claims.

[0153] When an element or layer is referred to as "above", "connected", "connected to", or "coupled to", it may be directly above, connected, connected to, or coupled to another element or layer, and there may be intervening elements or intervening layers. In contrast, when an element is referred to as "directly above", "directly connected", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or intervening layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between", "adjacent" vs. "directly adjacent", etc.). As used in this specification, the term "and / or" includes any combination and all combinations of one or more of the associated listed items. That is, the description of A and / or B means at least one of A and B.

[0154] Spatially relative terms such as "inner", "outer", "back", "lower", "low", "upper", "high", etc. are used herein to facilitate descriptions of the relationship of one element or feature to another element or feature as illustrated. Spatially relative terms can be intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the drawings. For example, if the device in the figures is turned over, an element described as "under" or "directly under" another element or feature will be oriented "above" the other element or feature. Thus, the term "under" can encompass both upward and downward orientations. The device may be oriented in other directions (rotated 90 degrees or other orientations), and the spatially relative descriptors used in this specification will be interpreted accordingly.

[0155] (Disclosure of Technical Ideas) This specification discloses a plurality of technical ideas described in a plurality of clauses listed below. Some clauses may be described in a multiple dependent form that alternatively cites preceding clauses in subsequent clauses. Further, some clauses may be described in a multiple dependent form that cites clauses in other multiple dependent forms. The clauses described in these multiple dependent forms define a plurality of technical ideas.

[0156] <Technical Idea 1> A printed circuit board (30) having a front surface (301) and a back surface (302) that is opposite to the front surface in the board thickness direction; A surface-mounted semiconductor package (41) mounted on the printed circuit board; A fixing structure (21) having a portion facing the front surface; Comprising: The printed circuit board has a plurality of fixing holes (31) for fixing the printed circuit board to the fixing structure; When the temperature fluctuates, the direction of warping of the printed circuit board and the direction of warping of the semiconductor package are in directions along the board thickness direction and are opposite to each other. The printed circuit board has a stress relaxation portion (32) that relaxes the stress acting on the mounting portion of the semiconductor package due to different directions of warping, an electronic device.

[0157] <Technical Idea 2> The semiconductor package is a non-lead package, the electronic device according to Technical Idea 1.

[0158] <Technical Idea 3> The stress relaxation portion is provided around the fixing hole, the electronic device according to Technical Idea 1 or Technical Idea 2.

[0159] <Technical Idea 4> The stress relaxation portion includes a portion that relaxes the stress by elastic deformation, the electronic device according to Technical Idea 3.

[0160] <Technical Idea 5> The stress relaxation portion is provided individually for the fixing holes, and includes a slit (321) that penetrates the printed circuit board in the board thickness direction, and a partition portion (322) that is partitioned by the slit and in which the fixing hole is provided, the electronic device according to Technical Idea 4.

[0161] <Technical Idea 6> The slit is arranged so as to cross at least one of a plurality of virtual straight lines that virtually connect the fixing holes that are different from each other in a plan view in the board thickness direction, the electronic device according to Technical Idea 5.

[0162] <Technical Idea 7> For all the virtual straight lines, at least one of the slits is arranged so as to cross, the electronic device according to Technical Idea 6.

[0163] <Technical Idea 8> The slit opens to a side surface of the printed circuit board, and the electronic device according to any one of Technical Ideas 5 to 7.

[0164] <Technical Idea 9> The printed circuit board has a rectangular shape in a plan view in the plate thickness direction. The slit opens to a first side surface of the printed circuit board and extends from the first side surface toward a second side surface located opposite to the first side surface. The electronic device according to Technical Idea 8.

[0165] <Technical Idea 10> The printed circuit board is provided separately from the first fixing hole which is the fixing hole, and has a second fixing hole (33) for reinforcing the fixing of the printed circuit board to the fixing structure. The second fixing hole is provided in a region surrounded by all the slits. The electronic device according to any one of Technical Ideas 5 to 9.

[0166] <Technical Idea 11> The stress relaxation portion includes an unpenetrated groove (323) and a thin portion (324) that is adjacent to the groove in the plate thickness direction and connects a portion on the fixing hole side of the groove and a portion on the side opposite to the fixing hole via the groove. The electronic device according to Technical Idea 4.

[0167] <Technical Idea 12> The printed circuit board has a main body portion (35) and an extended portion (325) that extends from the main body portion and is provided with the fixing hole. The stress relaxation portion includes the extended portion. The electronic device according to Technical Idea 4.

[0168] <Technical Idea 13> The extended portion includes a first extended portion (3251) that extends in a predetermined direction and a second extended portion (3252) that is continuous with the first extended portion and extends in a direction different from the predetermined direction. The electronic device according to Technical Idea 12.

[0169] <Technical Idea 14> The semiconductor package includes a lead frame (42), a semiconductor chip (43) having a lower surface and an upper surface and disposed on the lead frame such that the lower surface faces the lead frame, and a sealing resin body (44) that seals the semiconductor chip so as to contact the upper surface. The linear expansion coefficient of the fixing structure is larger than that of the printed circuit board. The semiconductor package is an electronic device according to any one of Technical Ideas 1 to 13 mounted on the one surface.

[0170] <Technical Idea 15> The semiconductor package includes a lead frame (42), a semiconductor chip (43) having a lower surface and an upper surface and disposed on the lead frame such that the lower surface faces the lead frame, and a sealing resin body (44) that seals the semiconductor chip so as to contact the upper surface. The linear expansion coefficient of the fixing structure is smaller than that of the printed circuit board. The semiconductor package is an electronic device according to any one of Technical Ideas 1 to 13 mounted on the back surface.

[0171] <Technical Idea 16> The semiconductor package includes a lead frame (42), a semiconductor chip (43) disposed on the lead frame, a metal plate member (45) disposed on the semiconductor chip, and a sealing resin body (44) that seals the semiconductor chip and the metal plate member. The linear expansion coefficient of the fixing structure is larger than that of the printed circuit board. The semiconductor package is an electronic device according to any one of Technical Ideas 1 to 13 mounted on the back surface.

[0172] <Technical Idea 17> The semiconductor package includes a lead frame (42), a semiconductor chip (43) disposed on the lead frame, a metal plate member (45) disposed on the semiconductor chip, and a sealing resin body (44) that seals the semiconductor chip and the metal plate member. The linear expansion coefficient of the fixing structure is smaller than that of the printed circuit board, The semiconductor package is an electronic device according to any one of Technical Ideas 1 to 13 mounted on the one surface.

[0173] <Technical Idea 18> The semiconductor package is a multi-chip package, The semiconductor package includes a lead frame (42), a first semiconductor chip (43A) disposed on the lead frame, a second semiconductor chip (43B) disposed on the lead frame, a metal plate member (45) disposed on the second semiconductor chip, and a sealing resin body (44) that seals the first semiconductor chip, the second semiconductor chip, and the metal plate member, and is an electronic device according to any one of Technical Ideas 1 to 13.

[0174] <Technical Idea 19> A first semiconductor package (41A) including a first lead frame (42A), a first semiconductor chip (43A) having a lower surface and an upper surface and disposed on the first lead frame such that the lower surface faces the first lead frame, and a first sealing resin body (44A) that seals the first semiconductor chip in contact with the upper surface; A second semiconductor package (41B) including a second lead frame (42B), a second semiconductor chip (43B) disposed on the second lead frame, a metal plate member (45) disposed on the second semiconductor chip, and a second sealing resin body (44B) that seals the second semiconductor chip and the metal plate member; and The first semiconductor package and the second semiconductor package are mounted on a common surface of the printed circuit board, One of the first semiconductor package and the second semiconductor package is a semiconductor package in which the direction of warping during temperature variation is opposite to the direction of warping of the printed circuit board, and is an electronic device according to any one of Technical Ideas 1 to 13.

Description of Reference Numerals

[0175] 10… Electronic device, 20… Housing, 21… Case, 211… Opposing wall, 212… Side wall, 213… Pedestal, 214… Screw hole, 22… Cover, 30… Printed circuit board, 301… One side, 302… Back side, 303, 304, 305, 306… Side surfaces, 31, 311, 312, 313, 314… Fixing holes, 315… Fixing part, 32… Stress relaxation part, 321… Slit, 3211… First slit part, 3212… Second slit part, 3113… Third slit part, 322… Partition part, 323… Groove, 324… Thin part, 325… Extended part, 3251… First extended part, 3252… Second extended part, 33… Fixing hole, 34… Region, 35… Main body part, 40… Electronic component, 41, 41A, 41B… Semiconductor package, 411… Bottom surface, 412… Top surface, 413… Side surface, 42, 42A, 42B… Lead frame, 421… Island, 422… Terminal, 43, 43A, 43B… Semiconductor chip, 44, 44A, 44B… Encapsulated resin body, 45… Clip, 50… Screw, 60… Heat dissipation gel

Claims

1. A printed circuit board (30) having a front surface (301) and a back surface (302) which is opposite to the front surface in the thickness direction, A surface-mounted semiconductor package (41) mounted on the printed circuit board, A fixing structure (21) having a portion facing the front surface, Comprising: The printed circuit board has a plurality of fixing holes (31) for fixing the printed circuit board to the fixing structure, The direction of warping of the printed circuit board and the direction of warping of the semiconductor package during temperature variation are in directions along the thickness direction and are opposite to each other, The printed circuit board has a stress relaxation portion (32) that relaxes the stress acting on the mounting portion of the semiconductor package due to different directions of warping, an electronic device.

2. The semiconductor package is a non-lead package, the electronic device according to Claim 1.

3. The stress relaxation portion is provided around the fixing hole, the electronic device according to Claim 2.

4. The stress relaxation portion includes a portion that relaxes the stress by elastic deformation, the electronic device according to Claim 3.

5. The stress relaxation portion is provided individually for the fixing holes, and includes a slit (321) that penetrates the printed circuit board in the thickness direction and a partition portion (322) that is partitioned by the slit and in which the fixing hole is provided, the electronic device according to Claim 4.

6. The slit is arranged so as to cross at least one of a plurality of virtual straight lines that virtually connect different fixing holes in a plan view in the thickness direction, the electronic device according to Claim 5.

7. For all the virtual straight lines, at least one slit is arranged so as to cross, the electronic device according to Claim 6.

8. The slit opens to the side surface of the printed circuit board, the electronic device according to Claim 5.

9. The printed circuit board has a rectangular shape in a plan view in the thickness direction, The slit opens to the first side surface of the printed circuit board and extends from the first side surface toward the second side surface located opposite to the first side surface, the electronic device according to Claim 8.

10. The printed circuit board is provided separately from the first fixing hole which is the fixing hole, and has a second fixing hole (33) for reinforcing the fixing of the printed circuit board to the fixing structure, The electronic device according to claim 5, wherein the second fixing hole is provided in a region surrounded by all of the slits.

11. The electronic device according to claim 4, wherein the stress relaxation portion includes an unpenetrated groove (323) and a thin portion (324) that is adjacent to the groove in the plate thickness direction and connects a portion on the fixing hole side of the groove and a portion on the opposite side of the fixing hole via the groove.

12. The printed circuit board has a main body portion (35) and an extended portion (325) that extends from the main body portion and is provided with the fixing hole. The electronic device according to claim 4, wherein the stress relaxation portion includes the extended portion.

13. The electronic device according to claim 12, wherein the extended portion includes a first extended portion (3251) that extends in a predetermined direction and a second extended portion (3252) that is connected to the first extended portion and extends in a direction different from the predetermined direction.

14. The semiconductor package has a lead frame (42), a semiconductor chip (43) that has a lower surface and an upper surface and is disposed on the lead frame such that the lower surface faces the lead frame, and a sealing resin body (44) that seals the semiconductor chip in contact with the upper surface. The linear expansion coefficient of the fixing structure is larger than the linear expansion coefficient of the printed circuit board. The electronic device according to any one of claims 1 to 13, wherein the semiconductor package is mounted on the one surface.

15. The semiconductor package has a lead frame (42), a semiconductor chip (43) that has a lower surface and an upper surface and is disposed on the lead frame such that the lower surface faces the lead frame, and a sealing resin body (44) that seals the semiconductor chip in contact with the upper surface. The linear expansion coefficient of the fixing structure is smaller than the linear expansion coefficient of the printed circuit board. The electronic device according to any one of claims 1 to 13, wherein the semiconductor package is mounted on the back surface.

16. The semiconductor package has a lead frame (42), a semiconductor chip (43) disposed on the lead frame, a metal plate member (45) disposed on the semiconductor chip, and a sealing resin body (44) that seals the semiconductor chip and the metal plate member. The linear expansion coefficient of the fixing structure is larger than the linear expansion coefficient of the printed circuit board. The electronic device according to any one of claims 1 to 13, wherein the semiconductor package is mounted on the back surface.

17. The semiconductor package includes a lead frame (42), a semiconductor chip (43) disposed on the lead frame, a metal plate member (45) disposed on the semiconductor chip, and a sealing resin body (44) that seals the semiconductor chip and the metal plate member. The linear expansion coefficient of the fixing structure is smaller than the linear expansion coefficient of the printed circuit board. The semiconductor package is the electronic device according to any one of claims 1 to 13, mounted on the one surface.

18. The semiconductor package is a multi-chip package. The semiconductor package includes a lead frame (42), a first semiconductor chip (43A) disposed on the lead frame, a second semiconductor chip (43B) disposed on the lead frame, a metal plate member (45) disposed on the second semiconductor chip, and a sealing resin body (44) that seals the first semiconductor chip, the second semiconductor chip, and the metal plate member. The semiconductor package is the electronic device according to any one of claims 1 to 13.

19. A first semiconductor package (41A) including a first lead frame (42A), a first semiconductor chip (43A) having a lower surface and an upper surface and disposed on the first lead frame such that the lower surface faces the first lead frame, and a first sealing resin body (44A) that seals the first semiconductor chip in contact with the upper surface. A second semiconductor package (41B) including a second lead frame (42B), a second semiconductor chip (43B) disposed on the second lead frame, a metal plate member (45) disposed on the second semiconductor chip, and a second sealing resin body (44B) that seals the second semiconductor chip and the metal plate member. The first semiconductor package and the second semiconductor package are mounted on a common surface of the printed circuit board. One of the first semiconductor package and the second semiconductor package is the semiconductor package in which the direction of warping during temperature variation is opposite to the direction of warping of the printed circuit board. The semiconductor package is the electronic device according to any one of claims 1 to 13.

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