Printed circuit board, electronic device, and electronic component

Abstract

To prevent molten solder from flowing into a heat transfer through-hole of a bottom electrode connection part to which a bottom electrode of an electronic component is soldered.SOLUTION: The printed board 10 is provided with a heat sink 12 having a rectangular bottom surface electrode, a plurality of terminals formed along outer peripheries of four sides of the bottom surface electrode, and a bottom surface electrode connecting part 12a and a peripheral part 12b formed on a non-use terminal bottom surface on which bottom surfaces of electronic components are soldered, and a plurality of through holes 13 connected to the peripheral part 12b at one end and arranged along the outer periphery of the bottom surface electrode connecting part 12a. In the printed board 10, a slit 16 is formed which avoids the through-hole 13 from the outer periphery of the side 12a of the bottom face electrode-connecting part, passes just under unused terminals when the electronic components are mounted, and extends to the outside of the outer end of the terminal-connecting part 14.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a printed circuit board on which an electronic component that is a surface-mount semiconductor package such as a QFN (Quad Flat Non-leaded package) or a QFP (Quad Flat Package) is mounted, an electronic device in which an electronic component is mounted on a printed circuit board, and an electronic component that is a surface-mount semiconductor package. [Background technology]

[0002] In recent years, with the increasing speed of signals, many surface-mount semiconductor packages such as QFN or QFP have been put into practical use. These packages have a large bottom electrode in the center of the bottom of the package body to strengthen the ground and to prevent heat dissipation, with many terminals located around the bottom electrode.

[0003] Research is also being conducted on printed circuit boards for mounting such surface-mount semiconductor packages, and Patent Document 1 proposes a printed circuit board that prevents the package from lifting up, tilting, or shifting from its designated position from the printed circuit board due to flux gas generated from the flux contained in the solder when the bottom electrodes and terminals of the surface-mount semiconductor package are connected using solder to bottom electrode connection parts and terminal connection parts formed on the surface of the printed circuit board, i.e., when they are electrically connected and physically fixed.

[0004] The printed circuit board shown in Patent Document 1 has an adhesive pattern layer to which the die pad portion of the surface-mounted semiconductor package is soldered, and has adhesive pattern layer grooves that expose the surface of the printed circuit board and through holes that reach the back surface of the printed circuit board to allow the release of vaporized gas from the flux contained in the solder that is generated during soldering. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-060141 Summary of the Invention [Problem to be solved by the invention]

[0006] The printed circuit board shown in Patent Document 1 has adhesive pattern layer grooves and through holes in the adhesive pattern layer to which the die pad portion of the surface-mount semiconductor package is soldered, which reduces the contact area between the die pad portion of the surface-mount semiconductor package and the adhesive pattern layer, resulting in a problem of reduced heat dissipation effect. Furthermore, when the solder is heated and melted, flux gas is generated inside the solder, and instead of remaining inside as a void, it may break through the solder and erupt to the outside. As the solder erupts, there is a risk that some of the molten solder may flow into the through hole.

[0007] The present disclosure has been made in consideration of the above-mentioned points, and aims to obtain a printed circuit board that can suppress the flow of molten solder into through holes that transmit heat from the bottom electrode connection portion while maintaining the contact area between the bottom electrode connection portion and the bottom electrode of an electronic component. [Means for solving the problem]

[0008] The printed circuit board according to the present disclosure comprises a rectangular bottom electrode, a bottom electrode connection portion to which the bottom electrode of an electronic component having a bottom surface with a plurality of terminals and unused terminals formed along the outer periphery of the four sides of the bottom electrode is soldered, a heat sink having on its surface a peripheral portion extending continuously from the outer periphery of the bottom electrode connection portion to the outer periphery of the bottom electrode connection portion, a plurality of through holes each connected at one end to the peripheral portion of the heat sink and arranged along the outer periphery of the bottom electrode connection portion of the heat sink, and a plurality of terminal connection portions formed on the surface along the outer periphery of the four sides of the heat sink and each soldered to a terminal corresponding to a plurality of terminals of the electronic component. A slit is formed on the surface of the printed circuit board, which extends from the outer periphery of the bottom electrode connection part of the heat sink, avoiding the through holes, passing directly under the unused terminals of the electronic component when the electronic component is mounted on the surface, and extending to the outside of the outer end of the terminal connection part. [Effects of the Invention]

[0009] According to the present disclosure, the contact area between the bottom electrode connection portion and the bottom electrode of the electronic component can be maintained, and part of the solder pushed by the flux gas generated when the solder is heated and melted can be prevented from flowing into the through hole that transmits heat from the bottom electrode connection portion. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a surface view showing a mounting surface of an electronic component in a printed circuit board according to a first embodiment. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 3] 3 is a bottom view showing an electronic component mounted on the printed circuit board according to the first embodiment. FIG. [Figure 4] 2 is a cross-sectional view taken along the line AA in FIG. 1, showing a state in which cream solder has been applied. FIG. [Figure 5] 2 is a cross-sectional view taken along line AA in FIG. 1, showing a state in which an electronic component is mounted on the printed circuit board according to the first embodiment. [Figure 6] FIG. 10 is a surface view showing a mounting surface of an electronic component in a printed circuit board according to a second embodiment. [Figure 7] FIG. 10 is a bottom view showing the electronic component according to the third embodiment. [Figure 8] 8 is a cross-sectional view of FIG. 7 taken along line B-B. [Figure 9] FIG. 11 is a surface view showing a printed circuit board on which an electronic component according to a third embodiment is mounted. [Figure 10] 10 is a cross-sectional view taken along line CC in FIG. 9 showing a state in which the electronic component according to the third embodiment is mounted on a printed circuit board. [Figure 11] FIG. 10 is a bottom view showing the electronic component according to the fourth embodiment. [Figure 12] FIG. 11 is a bottom view showing the electronic component according to the fifth embodiment. [Figure 13] FIG. 11 is a surface view showing a printed circuit board on which an electronic component according to a fifth embodiment is mounted. [Figure 14] 14 is a cross-sectional view taken along line DD in FIG. 13 showing a state in which the electronic component according to the fifth embodiment is mounted on a printed circuit board. FIG. [Figure 15] FIG. 13 is a bottom view showing the electronic component according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiment 1 A printed circuit board 10 according to a first embodiment will be described with reference to FIGS. An electronic component 20, which is a surface-mount semiconductor package such as a QFN or QFP, is mounted on the printed circuit board 10 according to the first embodiment. The following description will be given of a case where a QFN is used as the electronic component 20. The case where a QFP is used as the electronic component is substantially the same as the case where a QFN is used. Furthermore, the electrode pads in a QFN and the lead terminals in a QFP are collectively called terminals.

[0012] Before describing printed circuit board 10 according to the first embodiment, electronic component 20, which is a QFN, mounted on printed circuit board 10 will be described with reference to FIG. A bottom electrode 22 having a large area is formed in the center of the bottom surface of the package main body 21 in order to strengthen the ground and to provide a heat dissipation measure.

[0013] The surface of bottom electrode 22 and the bottom surface of package body 21 are on the same plane. That is, the bottom electrode 22 is embedded in the bottom surface of the package body 21 . The planar shape of the package body 21 is rectangular, usually square. The package body 21 has a semiconductor element built in, and is made of a resin material.

[0014] The bottom electrode 22 has the function of dissipating heat generated by the semiconductor element, and is set to ground potential when mounted on the printed circuit board 10 . The bottom electrode 22 is a metal body formed in the center of the bottom surface of the package body 21 . The bottom electrode 22 has a rectangular, usually square, planar shape.

[0015] At the outer peripheral edge of the bottom surface of package body 21, a plurality of terminals are formed on the outside along the periphery of each of the four sides of bottom electrode 22. A plurality of terminals are arranged at equal intervals along each of the four sides of the bottom electrode 22. It should be noted that FIG. 3 shows the number of terminals as an example, and many terminals are arranged at equal intervals along each side.

[0016] The multiple terminals include terminals 23 electrically connected to pads of the semiconductor element, which include multiple signal terminals for transmitting signals, multiple power supply terminals to which a power supply voltage is applied to the semiconductor element, and multiple grounding terminals that are set to ground potential, as well as multiple unused terminals 24 that are dummy terminals and are not connected to, i.e., not used by, the semiconductor element.

[0017] The surfaces of the plurality of terminals 23 and the surfaces of the plurality of unused terminals 24 and the bottom surface of the package body 21 are on the same plane. That is, the plurality of terminals 23 and the plurality of unused terminals 24 are embedded in the outer peripheral edge of the bottom surface of the package body 21 .

[0018] The terminals 23 and the pads of the semiconductor element are electrically connected by bonding wires. The unused terminals 24 are terminals that are not electrically connected to the semiconductor elements and are in an electrically floating state or at ground potential. FIG. 3 shows four unused terminals 24 as an example.

[0019] As shown in Figures 1 and 2, the printed circuit board 10 of embodiment 1 has a heat sink 12, multiple through holes 13, multiple terminal connection portions 14, and resist 15 in the mounting area on the surface of an insulating substrate 11 where electronic components 20 are mounted, and multiple slits 16 are formed. The insulating substrate 11 is made of an insulating material such as a resin material. In FIG. 1, the rectangular area indicated by the dashed line is the area occupied by a package body 21 when an electronic component 20 is mounted in the mounting area of ​​insulating substrate 11.

[0020] The heat sink 12 is a copper foil formed on the surface of the insulating substrate 11 by patterning. The heat sink 12 is at ground potential. The heat sink 12 has a bottom electrode connection portion 12a and a peripheral portion 12b. The bottom electrode 22 of the electronic component 20 is soldered to the bottom electrode connection portion 12a. Cream solder is used. The planar shape of bottom electrode connection portion 12a is the same size and shape as the planar shape of bottom electrode 22, and is the same rectangular shape as bottom electrode 22, usually a square.

[0021] The peripheral portion 12b extends continuously outward from the outer periphery of the bottom surface electrode connection portion 12a. The outer periphery of the peripheral portion 12b is parallel to the outer periphery of the bottom electrode connection portion 12a. A part of a plurality of slits 16 is formed in the peripheral portion 12b.

[0022] The bottom electrode connection portion 12a and the peripheral portion 12b are formed by removing a portion of the rectangular copper foil corresponding to a part of the slit 16 by etching. The copper foil may be patterned by masking a portion corresponding to a part of the slit 16 to form the bottom electrode connection portion 12a and the peripheral portion 12b.

[0023] The plurality of through holes 13 are arranged at positions where peripheral portion 12b is formed along the outer periphery of bottom surface electrode connection portion 12a of heat sink 12. A land on one end of each of the plurality of through holes 13 is thermally and electrically connected to the peripheral portion 12b. The other end land of each of the plurality of through holes 13 is formed on the back surface of the insulating substrate 11 . A metal layer is formed on the inner wall of each of the plurality of through holes 13, connecting the land on one end side to the land on the other end side.

[0024] Each of the plurality of through holes 13 is a heat dissipation path that transfers heat from the bottom electrode 22 of the electronic component 20 to the back side of the insulating substrate 11 . Each of the multiple through holes 13 transmits heat from the bottom electrode 22 of the electronic component 20, which has been transferred to the heat sink 12, from the land on one end to the land on the other end via the metal layer formed on the inner wall, and then to the back side of the insulating substrate 11. In each of the plurality of through holes 13, a heat transfer path is formed from the land on one end to the land on the other end via the metal layer.

[0025] The land on one end of each of the plurality of through holes 13 is formed integrally with the peripheral portion 12b by copper foil, and the copper foil is formed continuously on the inner wall up to the land on the other end. Alternatively, the lands on one end and the other end of each of the plurality of through holes 13 may be formed from copper foil, and the inner walls may be copper plated. Furthermore, a backside heat sink made of copper foil may be provided on the backside of insulating substrate 11, which is thermally and electrically connected to the lands on the other ends of the plurality of through holes 13 respectively. By providing the back surface heat sink, the heat dissipation from the bottom electrodes 22 of the electronic component 20 can be further improved.

[0026] A plurality of terminal connection portions 14 are formed on the surface of insulating substrate 11 along the outer periphery of the four sides of heat sink 12 . The multiple terminal connection portions 14 are provided corresponding to the terminals 23 of the electronic component 20, and when the electronic component 20 is mounted in the mounting area of ​​the insulating substrate 11, each of the multiple terminal connection portions 14 is soldered to a terminal 23 corresponding to each of the multiple terminals 23 of the electronic component 20. Cream solder is used.

[0027] When the electronic component 20 is mounted in the mounting area of ​​the insulating substrate 11, no terminal connection portion is formed directly below the unused terminal 24 of the electronic component 20. Directly below the unused terminals 24 of the electronic component 20, a part of the slit 16 is formed that communicates with one of the slits 16 formed in the peripheral portion 12b.

[0028] Each of the multiple slits 16 extends from the outer periphery of the bottom electrode connection portion 12a of the heat sink 12, avoiding the through hole 13, and when the electronic component 20 is mounted in the mounting area of ​​the insulating substrate 11, passes directly below the unused terminal 24 of the electronic component 20 and extends to the outside of the outer end of the terminal connection portion 14. Each of the plurality of slits 16 serves as a flow path for flux gas from the flux contained in the solder that is generated during soldering.

[0029] Four slits 16 are formed corresponding to the four corners of bottom surface electrode connection portion 12a. Each slit 16 has an inlet portion 16a formed in the peripheral portion 12b along the outer periphery at the corner of the bottom electrode connection portion 12a of the heat sink 12, and a linear outlet portion 16b continuing from the inlet portion 16a and positioned directly below the unused terminal 24 of the electronic component 20. The slits extending from the peripheral portion 12b of the outflow portion 16b, passing directly below the unused terminals 24, to the outside of the outer end of the terminal connection portion 14 are formed by removing the resist 15 by etching.

[0030] The inflow portions 16a of the four slits 16 form an inflow portion surrounding the bottom electrode connection portion 12a. Therefore, when the bottom electrode 22 of the electronic component 20 is soldered to the bottom electrode connection portion 12a, the flux gas generated from the flux contained in the solder is guided to the inlet portion 16a of the four slits 16 and discharged from the outlet portion 16b. Furthermore, the flux gas generated inside the solder cannot remain inside as voids and is ejected to the outside, causing the molten solder to be guided to the inlet portions 16a of the four slits 16 and discharged from the outlet portions 16b.

[0031] The spacing between the inlet portions 16a of the adjacent slits 16 is set to an extent that does not impair heat transfer between the bottom electrode connection portion 12a and the peripheral portion 12b of the heat sink 12. Furthermore, since the outflow portion 16b of each slit 16 passes directly below the unused terminal 24 of the electronic component 20, the position for forming the slit can be secured even if the number of terminals 23 in the electronic component 20 increases and the spacing between the terminals becomes narrow.

[0032] The resist 15 is an insulating material such as a resin material that covers and protects the surface of the printed circuit board 10 other than the bottom electrode connection portion 12a of the heat sink 12, the through holes of the multiple through holes 13, the multiple terminal connection portions 14, and the multiple slits 16. In FIG. 1, the resist on the peripheral portion 12b of the heat sink 12 is omitted to avoid complicating the drawing.

[0033] A method for mounting electronic components 20 on printed circuit board 10 to form an electronic device will now be described. Cream solder 17 is applied to bottom surface electrode connection portion 12a and a plurality of terminals 23 on printed circuit board 10 as shown in FIG. As is generally known, the cream solder 17 is applied by using a metal mask and a squeegee.

[0034] Next, the electronic components 20 are mounted on the printed circuit board 10 by a chip mounter or the like, as is generally known. At this time, the bottom electrode 22 of the electronic component 20 is arranged opposite the bottom electrode connection portion 12a of the heat sink 12 on the printed circuit board 10 via the cream solder 17, as shown in Figure 5, and each of the multiple terminals 23 of the electronic component 20 is arranged opposite the corresponding terminal connection portion 14 on the printed circuit board 10 via the cream solder 17.

[0035] With the electronic component 20 mounted on the printed circuit board 10, it is heated in a reflow furnace or other equipment to melt the cream solder 17, and then cooled, thereby electrically connecting and physically fixing the bottom electrode 22 of the electronic component 20 to the bottom electrode connection portion 12a of the heat sink 12 on the printed circuit board 10, and the multiple terminals 23 of the electronic component 20 to the corresponding terminal connection portions 14 on the printed circuit board 10.

[0036] Flux gas generated from the flux contained in the cream solder 17 when heated in equipment such as a reflow furnace is introduced into the inlet portions 16a of the four slits 16 and is discharged from the outlet portions 16b. Also, a portion of the molten solder pushed by the flux gas is guided to the inflow portions 16a of the four slits 16 and discharged from the outflow portions 16b.

[0037] Since the four slits 16 are formed so as to avoid the through-holes 13, the generated flux gas and the molten solder pushed out by the flux gas do not enter the penetrating holes of the through-holes 13.

[0038] In printed circuit board 10 according to embodiment 1, slit 16 is formed so as to avoid through-hole 13 from the outer periphery of bottom electrode connection portion 12a of heat sink 12, pass directly below unused terminal 24 of electronic component 20 when electronic component 20 is mounted on the surface, and extend to the outside of the outer end of terminal connection portion 14. Therefore, flux gas generated from the flux contained in the solder can be discharged when bottom electrode 22 of electronic component 20 is soldered to bottom electrode connection portion 12a without reducing the contact area of ​​bottom electrode connection portion 12a of heat sink 12 with bottom electrode 22 of electronic component 20.

[0039] Furthermore, in the printed circuit board 10 according to the first embodiment, the generated flux gas and the molten solder pushed out by the flux gas do not enter the penetrating holes of the through-holes 13. Furthermore, in printed circuit board 10 according to embodiment 1, even if the number of terminals 23 in electronic component 20 increases and the interval between the terminals becomes narrower, the positions for forming slits can be secured.

[0040] In embodiment 1, each of the multiple through holes 13 is a through hole that penetrates to the back surface of the insulating substrate 11, or a through hole that is connected to a back surface heat sink on the back surface of the insulating substrate 11. However, each of the multiple through holes 13 may also be a through hole whose other end land is connected to an inner layer metal body (layer) made of copper foil provided in the inner layer of the insulating substrate 11 and is at ground potential.

[0041] Each of the multiple through holes 13 may be connected midway to an inner layer metal body (layer) provided in the inner layer of the insulating substrate 11, and may be a through hole connected to a back side heat sink provided on the back surface of the insulating substrate 11.

[0042] Embodiment 2 A printed circuit board 10A according to the second embodiment will be described with reference to FIG. Printed circuit board 10A according to the second embodiment is the same as printed circuit board 10 according to the first embodiment except for the plurality of slits 16A which are different from the plurality of slits 16 in printed circuit board 10 according to the first embodiment. Therefore, the following description will mainly focus on the plurality of slits 16A, which are the different points. In FIG. 6, the same reference numerals as those in FIGS. 1 to 5 indicate the same or corresponding parts.

[0043] The printed circuit board 10A according to the second embodiment has a heat sink 12, a plurality of through holes 13, a plurality of terminal connection portions 14, and a resist 15 in the mounting area on the surface of the insulating substrate 11 where the electronic component 20 is mounted, and a plurality of slits 16A are formed.

[0044] Each of the multiple slits 16A extends from the outer periphery of the bottom electrode connection portion 12a of the heat sink 12, avoiding the through hole 13, and when the electronic component 20 is mounted in the mounting area of ​​the insulating substrate 11, passes directly below the unused terminal 24 of the electronic component 20 and extends to the outside of the outer end of the terminal connection portion 14.

[0045] Four slits 16A are formed corresponding to the four sides of bottom surface electrode connection portion 12a. Each slit 16A has an inlet portion 16Aa along the outer periphery of the side of the bottom electrode connection portion 12a of the heat sink 12, and a linear outlet portion 16Ab continuing from the inlet portion 16Aa and positioned directly below the unused terminal 24 of the electronic component 20.

[0046] Inflow portions 16Aa of the four slits 16A form an inflow portion surrounding bottom surface electrode connection portion 12a. Therefore, when the bottom electrode 22 of the electronic component 20 is soldered to the bottom electrode connection portion 12a, the flux gas generated from the flux contained in the solder is guided to the inlet portion 16Aa of the four slits 16 and discharged from the outlet portion 16Ab. Furthermore, flux gas generated inside the solder cannot remain inside as voids and is ejected to the outside, and the molten solder is also guided to the inflow portions 16Aa of the four slits 16 and discharged from the outflow portions 16Ab.

[0047] The distance between the inlet portions 16Aa of the adjacent slits 16A is set to an extent that does not impair heat transfer between the bottom electrode connection portion 12a and the peripheral portion 12b of the heat sink 12. Furthermore, since the outflow portion 16Ab of each slit 16A passes directly below the unused terminal 24 of the electronic component 20, the position for forming the slit can be secured even if the number of terminals 23 in the electronic component 20 increases and the spacing between the terminals becomes narrow. The printed circuit board 10A according to the second embodiment has the same effects as the printed circuit board 10 according to the first embodiment.

[0048] Embodiment 3 An electronic component 20A according to a third embodiment will be described with reference to FIGS. Electronic component 20A according to the third embodiment is mounted in a mounting area of ​​insulating substrate 11 on a printed circuit board. The electronic component 20A according to the third embodiment is a surface-mount semiconductor package such as a QFN or QFP. The following description will be given of a case where a QFN is used as electronic component 20A. The case where a QFP is used as an electronic component is substantially the same as the case where a QFN is used. Furthermore, the electrode pads in a QFN and the lead terminals in a QFP are collectively called terminals.

[0049] As shown in FIGS. 7 and 8, electronic component 20A according to the third embodiment includes package body 21, bottom electrode 22, a plurality of terminals 23, and wall portion 25. As shown in FIGS. A semiconductor element is built into the inside of the package body 21, which is made of a resin material. The planar shape of the package body 21 is rectangular, usually square.

[0050] The bottom electrode 22 is formed in the center of the bottom surface of the package body 21 . The surface of bottom electrode 22 and the bottom surface of package body 21 are on the same plane. That is, the bottom electrode 22 is embedded in the bottom surface of the package body 21 . The bottom electrode 22 has a rectangular, usually square, planar shape. The bottom electrode 22 is soldered to a bottom electrode connection on the printed circuit board. Cream solder is used. The bottom electrode 22 has the function of dissipating heat generated by the semiconductor element, and is set to ground potential when mounted on a printed circuit board.

[0051] A plurality of terminals 23 are formed on the outer periphery of the bottom surface of package body 21 along the outer periphery of each of the four sides of bottom electrode 22 . A plurality of terminals 23 are arranged at equal intervals along each of the four sides of the bottom electrode 22. Note that FIG. 7 shows an example of the number of terminals 23, and many terminals 23 are arranged at equal intervals along each side.

[0052] The multiple terminals 23 include terminals electrically connected to pads of the semiconductor elements, including multiple signal terminals for transmitting signals, multiple power supply terminals to which a power supply voltage is applied to the semiconductor elements, and multiple grounding terminals that are set to ground potential, as well as multiple unused terminals that are not connected to, i.e., not used by, the semiconductor elements, which are dummy terminals.

[0053] The surfaces of the terminals 23 and the bottom surface of the package body 21 are flush with each other. That is, the plurality of terminals 23 are embedded in the outer peripheral edge of the bottom surface of the package body 21 . The electrically connected terminals 23 and the pads of the semiconductor element are electrically connected by bonding wires.

[0054] The unused terminals are terminals that are not electrically connected to the semiconductor element and are in an electrically floating state, or are at ground potential. Each of the plurality of terminals 23 is soldered to a corresponding terminal connection portion on the printed circuit board. Cream solder is used.

[0055] Wall portion 25 is formed along the four sides of bottom electrode 22 between bottom electrode 22 and a plurality of terminals 23 on the bottom surface of package body 21, and has a plurality of slits 26 that serve as gas exhaust ports. The cuts 26 are formed at positions facing the center of each of the four sides of the bottom electrode 22 . The wall portion 25 is formed so as to protrude outward from the bottom surface of the package body 21 beyond the bottom surface electrode 22 .

[0056] The wall portion 25 is disposed closer to the bottom electrode 22 than the plurality of terminals 23 and is formed so as to surround the bottom electrode 22 . The wall portion 25 is made of the same material as the package body 21 and is formed at the same time as the package body 21 by, for example, resin molding.

[0057] Next, a printed circuit board 10B on which an electronic component 20A according to the third embodiment is mounted will be described with reference to FIG. The printed circuit board 10B has a heat sink 12, a plurality of through holes 13, a plurality of terminal connecting portions 14, and a resist 15 in a mounting area on the surface of the insulating substrate 11 where the electronic component 20A is mounted.

[0058] In FIG. 9, the rectangular area indicated by the dashed line is the area occupied by the package body 21 when the electronic component 20 is mounted in the mounting area of ​​the insulating substrate 11. In FIG. 9, four L-shaped regions indicated by dashed dotted lines are regions where wall portions 25 are arranged when electronic component 20A is mounted in the mounting region of insulating substrate 11.

[0059] The heat sink 12 is an integrally formed rectangular copper foil having a bottom electrode connection portion 12a and a peripheral portion 12b. The planar shape of bottom electrode connection portion 12a is the same size and shape as the planar shape of bottom electrode 22, and is the same rectangular shape as bottom electrode 22, usually a square. Bottom electrode 22 of electronic component 20A is soldered to bottom electrode connection portion 12a.

[0060] The plurality of through holes 13 are arranged at positions where peripheral portion 12b is formed along the outer periphery of bottom surface electrode connection portion 12a of heat sink 12. Each of the plurality of through holes 13 is a heat dissipation path that transfers heat from bottom electrode 22 of electronic component 20A to the back side of insulating substrate 11. Each of the plurality of through holes 13 forms a heat transfer path.

[0061] A plurality of terminal connection portions 14 are formed on the surface of insulating substrate 11 along the outer periphery of the four sides of heat sink 12 . The plurality of terminal connection portions 14 are provided corresponding to the terminals 23 of the electronic component 20 , and each of the plurality of terminal connection portions 14 is soldered to a corresponding terminal 23 of the electronic component 20 .

[0062] The resist 15 is an insulating material such as a resin material that covers and protects the surface of the printed circuit board 10 other than the bottom electrode connection portion 12a of the heat sink 12, the through holes of the multiple through holes 13, the multiple terminal connection portions 14, and the multiple slits 16. In FIG. 9, the resist on the peripheral portion 12b of the heat sink 12 is omitted to avoid complicating the drawing.

[0063] A method for mounting electronic component 20A on printed circuit board 10B to form an electronic device will be described. Cream solder 17 is applied to bottom surface electrode connection portion 12a and a plurality of terminals 23 on printed circuit board 10B.

[0064] The electronic component 20A is mounted on the printed circuit board 10 by arranging the bottom electrode 22 of the electronic component 20A opposite the bottom electrode connection portion 12a of the heat sink 12 on the printed circuit board 10 via the cream solder 17, and by arranging each of the multiple terminals 23 of the electronic component 20A opposite the corresponding terminal connection portion 14 on the printed circuit board 10B via the cream solder 17. This state is shown in Figure 10.

[0065] With electronic component 20A mounted on printed circuit board 10, it is heated in a reflow furnace or other equipment to melt cream solder 17, and then cooled, thereby electrically connecting and physically fixing bottom electrode 22 of electronic component 20A to bottom electrode connection portion 12a of heat sink 12 on printed circuit board 10B, and each of multiple terminals 23 of electronic component 20A to corresponding terminal connection portion 14 on printed circuit board 10B.

[0066] The end face of the wall portion 25 of the electronic component 20A is brought into close contact with the surface of the resist 15 formed on the peripheral portion 12b of the heat sink 12 of the printed circuit board 10B. As a result, the flux gas generated from the flux contained in the cream solder 17 when heated in equipment such as a reflow furnace is blocked by the wall portion 25 and is guided to the multiple slits 26, which are gas exhaust ports formed in the wall portion 25, and is exhausted from the slits 26. Furthermore, a portion of the molten solder pushed by the flux gas is also blocked by the wall portion 25, guided to the plurality of slits 26 formed in the wall portion 25, and discharged from the slits 26.

[0067] Since the plurality of slits 26 are formed in the wall portion 25 so that the through-holes 13 are not provided on the flow path of the flux gas discharged from the plurality of slits 26 formed in the wall portion 25, the generated flux gas and the molten solder pushed out by the flux gas do not enter the penetrating holes of the through-holes 13.

[0068] Electronic component 20A of embodiment 3 is an electronic component having bottom electrode 22 and multiple terminals 23 on the bottom surface of package body 21, and has wall portion 25 formed along the four sides of bottom electrode 22 between bottom electrode 22 and multiple terminals 23, protruding outward from bottom electrode 22 and having multiple slits 26 that serve as gas exhaust ports.Therefore, flux gas generated from flux contained in the solder can be exhausted when bottom electrode 22 of electronic component 20A is soldered to bottom electrode connection portion 12a without reducing the contact area of ​​bottom electrode connection portion 12a of heat sink 12 with bottom electrode 22 of electronic component 20A. The electronic component 20A according to the third embodiment may be mounted on the printed circuit board 10 according to the first embodiment or the printed circuit board 10A according to the second embodiment.

[0069] Embodiment 4 An electronic component 20B according to the fourth embodiment will be described with reference to FIG. Electronic component 20B according to the fourth embodiment is the same as electronic component 20A according to the third embodiment except for wall portion 25a. Therefore, the following description will mainly focus on the plurality of wall portions 25a, which are the difference. In FIG. 11, the same reference numerals as those in FIGS. 7 to 10 indicate the same or corresponding parts.

[0070] Electronic component 20B according to the fourth embodiment includes package body 21, bottom electrode 22, a plurality of terminals 23, and wall portion 25a. Wall portion 25a is formed along the four sides of bottom electrode 22 between bottom electrode 22 and a plurality of terminals 23 on the bottom surface of package body 21, and has a plurality of slits 26a that serve as gas exhaust ports. The cuts 26a are formed at corners of the bottom electrode 22 at positions facing the outer periphery. The wall portion 25 a is formed so as to protrude outward from the bottom surface of the package body 21 beyond the bottom electrode 22 .

[0071] The wall portion 25 a is disposed closer to the bottom electrode 22 than the plurality of terminals 23 , and is formed so as to surround the bottom electrode 22 . The wall portion 25a is made of the same material as the package body 21, and is formed simultaneously with the package body 21 by, for example, resin molding.

[0072] When electronic component 20B is mounted on printed circuit board 10B, the end faces of wall portions 25a of electronic component 20B are brought into close contact with the surface of resist 15 formed on peripheral portion 12b of heat sink 12 on printed circuit board 10B. As a result, the flux gas generated from the flux contained in the cream solder 17 when heated in equipment such as a reflow furnace is blocked by the wall portion 25a and is guided to the multiple slits 26a, which are gas exhaust ports formed in the wall portion 25a, and is exhausted from the slits 26a. Furthermore, a portion of the molten solder pushed by the flux gas is also blocked by the wall portion 25a, guided to the plurality of slits 26a formed in the wall portion 25a, and discharged from the slits 26a.

[0073] Since the plurality of slits 26a are formed in the wall portion 25a so that the through-hole 13 is not located on the flow path of the flux gas discharged from the plurality of slits 26a formed in the wall portion 25a, the generated flux gas and the molten solder pushed out by the flux gas do not enter the penetrating hole of the through-hole 13.

[0074] The electronic component 20B according to the fourth embodiment has the same effects as the electronic component 20A according to the third embodiment. Electronic component 20B according to the fourth embodiment may be mounted on printed circuit board 10 according to the first embodiment or printed circuit board 10A according to the second embodiment.

[0075] Embodiment 5. An electronic component 20C according to a fifth embodiment will be described with reference to FIGS. Electronic component 20C according to embodiment 5 differs from electronic component 20A according to embodiment 3 in that it is provided with a plurality of gas vent holes 27, but is otherwise the same. Therefore, the following description will mainly focus on the gas vent holes 27, which are the difference. 12 to 14, the same reference numerals as those in FIGS. 7 to 10 indicate the same or corresponding parts.

[0076] As shown in FIGS. 12 and 14, electronic component 20C according to the fifth embodiment includes package body 21, bottom electrode 22, a plurality of terminals 23, wall portion 25, and a plurality of gas vent holes 27. Each gas vent hole 27 passes through the package body 21 from the bottom surface of the package body 21 at the position where the slit 26 of the wall portion 25 is formed, and communicates with the outside of the package body 21 .

[0077] That is, each gas vent hole 27 is formed on the bottom surface of package body 21 between bottom electrode 22 and a plurality of terminals 23 on the bottom electrode 22 side, at a position facing the center of each side of bottom electrode 22 . The gas vent hole 27 penetrates the package body 21 in a straight line from the bottom surface to the surface.

[0078] The gas vent holes 27 are formed by drilling the package body 21 . The gas vent holes 27 may be formed at the same time as the package body 21 is formed by resin molding. The gas vent hole 27 may be a through-hole that penetrates from the bottom surface of the package body 21 to any one of the four side surfaces.

[0079] In FIG. 13, the position of gas vent hole 27 relative to printed circuit board 10B when electronic component 20C is mounted on printed circuit board 10B is indicated by a dashed circle. The printed circuit board 10B shown in FIG. 13 is the same as the printed circuit board 10B shown in FIG. 9 in the third embodiment, and therefore a description thereof will be omitted.

[0080] When electronic component 20C is mounted on printed circuit board 10B, the end faces of wall portions 25 of electronic component 20C are brought into close contact with the surface of resist 15 formed on peripheral portion 12b of heat sink 12 on printed circuit board 10B. As shown in FIG. 14, the gas vent hole 27 communicates with the space formed between the bottom surface of the package body 21 and the surface of the resist 15 formed on the peripheral portion 12b of the heat sink 12 on the printed circuit board 10B.

[0081] As a result, the flux gas generated from the flux contained in the cream solder 17 when heated in equipment such as a reflow furnace is blocked by the wall portion 25 and is guided to the multiple slits 26, which are gas exhaust ports formed in the wall portion 25, and is exhausted from the slits 26. At the same time, the flux gas is discharged to the outside of the package body 21 through the gas vent hole 27 . Furthermore, a portion of the molten solder pushed by the flux gas is also blocked by the wall portion 25, guided to the plurality of slits 26 formed in the wall portion 25, and discharged from the slits 26.

[0082] Electronic component 20C according to the fifth embodiment has the same effects as electronic component 20A according to the third embodiment, and furthermore, can efficiently discharge flux gas. Electronic component 20C according to the fifth embodiment may be mounted on printed circuit board 10 according to the first embodiment or printed circuit board 10A according to the second embodiment.

[0083] Embodiment 6 An electronic component 20D according to the sixth embodiment will be described with reference to FIG. Electronic component 20D according to the sixth embodiment differs from electronic component 20B according to the fourth embodiment in that it is provided with a plurality of gas vent holes 27a, but is otherwise the same. Therefore, the following description will mainly focus on the gas vent holes 27a, which are the difference. In FIG. 15, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts.

[0084] Electronic component 20D according to the sixth embodiment includes package body 21, bottom electrode 22, a plurality of terminals 23, wall portion 25a, and a plurality of gas vent holes 27a. Each gas vent hole 27a passes through the package body 21 from the bottom surface of the package body 21 at the position where the slit 26a of the wall portion 25a is formed, and communicates with the outside of the package body 21.

[0085] That is, each gas vent hole 27 is formed on the bottom surface of package body 21 between bottom electrode 22 and a plurality of terminals 23 on the bottom electrode 22 side, at a position facing the outer periphery of a corner of bottom electrode 22 . The gas vent hole 27a penetrates the package body 21 in a straight line from the bottom surface to the surface.

[0086] The gas vent holes 27 a are formed by drilling the package body 21 . The gas vent holes 27a may be formed at the same time as the package body 21 is formed by resin molding. The gas vent hole 27a may be a through-hole that penetrates from the bottom surface of the package body 21 to any one of the four side surfaces.

[0087] When electronic component 20D is mounted on printed circuit board 10B, the end faces of wall portions 25a of electronic component 20D are brought into close contact with the surface of resist 15 formed on peripheral portion 12b of heat sink 12 on printed circuit board 10B. Further, the gas vent hole 27a communicates with the space formed between the bottom surface of the package body 21 and the surface of the resist 15 formed on the peripheral portion 12b of the heat sink 12 on the printed circuit board 10B.

[0088] As a result, the flux gas generated from the flux contained in the cream solder 17 when heated in equipment such as a reflow furnace is blocked by the wall portion 25a and is guided to the multiple slits 26a, which are gas exhaust ports formed in the wall portion 25a, and is exhausted from the slits 26a. At the same time, the flux gas is discharged to the outside of the package body 21 through the gas vent hole 27a. Furthermore, a portion of the molten solder pushed by the flux gas is also blocked by the wall portion 25a, guided to the plurality of slits 26a formed in the wall portion 25a, and discharged from the slits 26a.

[0089] The electronic component 20D according to the sixth embodiment has the same effects as the electronic component 20A according to the fourth embodiment, and furthermore, can efficiently discharge flux gas. Electronic component 20D according to the sixth embodiment may be mounted on printed circuit board 10 according to the first embodiment or printed circuit board 10A according to the second embodiment.

[0090] It should be noted that the embodiments may be freely combined, any of the components of the embodiments may be modified, or any of the components of the embodiments may be omitted. [Industrial Applicability]

[0091] The printed circuit board according to the present disclosure is applicable to electronic components that are surface-mount semiconductor packages such as QFN or QFP, which are miniaturized and have bottom electrodes formed on the bottom surface of the package body for dissipating generated heat, printed circuit boards on which such electronic components are mounted, and electronic devices equipped with printed circuit boards on which such electronic components are mounted. [Explanation of symbols]

[0092] 10, 10A, 10B printed circuit board, 11 insulating substrate, 12 heat sink, 12a bottom electrode connection portion, 12b peripheral portion, 13 through hole, 14 terminal connection portion, 15 resist, 16, 16A slit, 20, 20A to 20D electronic component, 21 package body, 22 bottom electrode, 23 terminal, 24 unused terminal, 25, 25a wall portion, 26, 26a cut, 27, 27a gas vent hole.

Claims

1. a heat sink having a bottom electrode connection portion to which the bottom electrode of an electronic component is soldered, the bottom electrode having a rectangular bottom electrode, and a plurality of terminals and unused terminals formed along the periphery of four sides of the bottom electrode, and a peripheral portion extending continuously from the periphery of the bottom electrode connection portion on its surface around the periphery of the bottom electrode connection portion; a plurality of through holes, each of which has one end connected to a peripheral portion of the heat sink and is arranged along an outer periphery of a bottom electrode connection portion of the heat sink; a plurality of terminal connection portions formed on a surface along the outer periphery of four sides of the heat sink, the terminal connection portions being soldered to terminals corresponding to the plurality of terminals of the electronic component, respectively; Equipped with a slit formed on the surface, the slit extending from the outer periphery of the bottom electrode connection portion of the heat sink to avoid the through-hole, passing directly under an unused terminal of the electronic component when the electronic component is mounted on the surface, and extending to the outside of the outer end of the terminal connection portion; Printed circuit board.

2. 2. The printed circuit board according to claim 1, wherein the slit has an inlet portion along the outer periphery at a corner of the bottom electrode connection portion of the heat sink, and a linear outlet portion that continues from the inlet portion and is positioned directly below an unused terminal of the electronic component.

3. 2. The printed circuit board according to claim 1, wherein the slit has an inlet portion along the outer periphery of the edge of the bottom electrode connection portion of the heat sink, and a linear outlet portion that continues from the inlet portion and is positioned directly below an unused terminal of the electronic component.

4. The printed circuit board according to any one of claims 1 to 3; an electronic component having a package body, a bottom electrode formed in a central portion of a bottom surface of the package body and soldered to a bottom electrode connection portion of a heat sink on the printed circuit board, and a plurality of terminals and unused terminals formed along the outer periphery of each of four sides of the bottom electrode at an outer peripheral edge of the bottom surface of the package body, the plurality of terminals being soldered to corresponding terminal connection portions on the printed circuit board; An electronic device comprising:

5. The printed circuit board according to any one of claims 1 to 3; an electronic component having a package body, a bottom electrode formed in a central portion of a bottom surface of the package body and soldered to a bottom electrode connection portion of a heat sink on the printed circuit board, a plurality of terminals formed at an outer peripheral end portion of the bottom surface of the package body along the outer peripheries of four sides of the bottom electrode and soldered to corresponding terminal connection portions on the printed circuit board, and a wall portion formed on the bottom surface of the package body between the bottom electrode and the plurality of terminals along the four sides of the bottom electrode, the wall portion having a plurality of slits that are gas exhaust ports and protruding outward from the bottom electrode; An electronic device comprising:

6. 6. The electronic device according to claim 5, wherein a gas vent hole is provided in the bottom surface of the package body at the position where the cut in the wall portion of the electronic component is formed, penetrating the package body and communicating with the outside of the package body.

7. The package body, a bottom electrode formed in the center of the bottom surface of the package body and soldered to a bottom electrode connection portion of a printed circuit board; a plurality of terminals formed along the outer periphery of each of the four sides of the bottom electrode at the outer periphery edge of the bottom surface of the package body; a wall portion formed along four sides of the bottom electrode between the bottom electrode and the plurality of terminals on the bottom surface of the package body, the wall portion having a plurality of slits serving as gas exhaust ports and protruding outward from the bottom electrode; An electronic component comprising:

8. The electronic component according to claim 7 , wherein the gaps in the wall portions are formed at positions facing the centers of the four sides of the bottom electrode.

9. The electronic component according to claim 7 , wherein the gap in the wall portion is formed at a corner of the bottom electrode at a position facing the outer periphery.

10. 10. The electronic component according to claim 7, wherein a vent hole is provided that penetrates the package body from the bottom surface of the package body at the position where the cut in the wall portion is formed, and communicates with the outside of the package body.

11. The package body, a bottom electrode formed in the center of the bottom surface of the package body and soldered to a bottom electrode connection portion of a printed circuit board; a plurality of terminals formed along the outer periphery of each of the four sides of the bottom electrode at the outer periphery edge of the bottom surface of the package body; a gas vent hole that is positioned between the bottom electrode and the plurality of terminals and closer to the bottom electrode than the plurality of terminals, the gas vent hole penetrating the package body from the bottom surface of the package body to communicate with the outside of the package body; An electronic component comprising:

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