Isolator

Abstract

To provide an isolator with improved reliability.SOLUTION: An isolator according to an embodiment includes a substrate including a first rigid substrate, which is a rigid substrate, and a first flexible printed wiring board, which is a flexible printed board, that is stacked in a first direction on the first rigid substrate, a first coil provided at the first flexible printed wiring board, a second coil provided at the first flexible printed wiring board and facing, with a space from, the first coil in the first direction, a first semiconductor chip provided on the substrate, a second semiconductor chip provided on the substrate, a first wire provided in the substrate and connecting the first semiconductor chip and the first coil, and a second wire provided in the substrate and connecting the second semiconductor chip and the second coil.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to an isolator. [Background technology]

[0002] Isolators are known for transmitting signals between a transmitting circuit and a receiving circuit that are electrically isolated from each other. Some isolators use a light-emitting element or a light-receiving element, while others use a coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-061236 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide an isolator with improved reliability. [Means for solving the problem]

[0005] The isolator of the embodiment includes a substrate having a first rigid substrate that is a rigid substrate and a first flexible printed wiring board that is a flexible printed wiring board stacked in a first direction on the first rigid substrate, a first coil provided on the first flexible printed wiring board, a second coil provided on the first flexible printed wiring board and facing and spaced apart from the first coil in the first direction, a first semiconductor chip provided on the substrate, a second semiconductor chip provided on the substrate, first wiring provided in the substrate and connecting the first semiconductor chip and the first coil, and second wiring provided in the substrate and connecting the second semiconductor chip and the second coil.

[0006] and a second wire connecting the electrode pad to the second semiconductor chip. The isolator of another embodiment includes a substrate having a first die pad, a first semiconductor chip provided on the first die pad, a second die pad provided at a distance from the first die pad, a first rigid substrate provided on the second die pad and being a rigid substrate, and a first flexible printed wiring board that is a flexible printed wiring board stacked in a first direction on the first rigid substrate; a first coil provided on the first flexible printed wiring board, a second coil provided on the first flexible printed wiring board and facing and spaced apart from the first coil in the first direction, an electrode pad provided on the substrate and connected to the second coil by a third wiring provided in the substrate, a third die pad provided at a distance from the first die pad and the second die pad, a second semiconductor chip provided on the third die pad, a first wire connecting the first semiconductor chip to the second die pad, and a second wire connecting the electrode pad to the second semiconductor chip. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic plan view of an isolator 100 according to a first embodiment. [Figure 2] FIG. 1 is a schematic plan view of an isolator 100 according to a first embodiment. [Figure 3] 1 is a cross-sectional view of an isolator 100 according to a first embodiment. [Figure 4] FIG. 3 is a cross-sectional view showing an example of the internal structure of a first flexible printed wiring board. [Figure 5] FIG. 2 is a cross-sectional view of an isolator 101 according to a first modified example of the first embodiment. [Figure 6] FIG. 10 is a cross-sectional view of an isolator 200 according to a second embodiment. [Figure 7] FIG. 10 is a cross-sectional view of an isolator 300 according to a third embodiment. [Figure 8] FIG. 11 is a cross-sectional view of an isolator 301 according to a first modified example of the third embodiment. [Figure 9]FIG. 10 is a cross-sectional view of an isolator 400 according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0009] The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing.

[0010] For example, in the cross-sectional views shown in the present specification, some laminated structures are shown, but the thickness ratio of each layer in the laminated structure is not necessarily the same as that in reality. Even if one layer is shown thicker than another layer in the cross-sectional view, in reality, the thicknesses of one layer and the other layer may be approximately the same, or one layer may be thinner than the other layer. In other words, the dimensions such as thicknesses shown in the drawings in the present specification may differ from the actual dimensions.

[0011] The direction from the first rigid substrate to the first flexible printed wiring board is defined as the Z direction (first direction). The direction perpendicular to the Z direction is defined as the X direction (second direction), and the direction intersecting the X and Z directions is defined as the Y direction (third direction). In this embodiment, the X direction, Y direction, and Z direction are shown as being orthogonal to each other, but they are not limited to being orthogonal as long as they intersect with each other.

[0012] For the sake of explanation, the positive direction in the Z direction is referred to as "up" and the negative direction in the Z direction is referred to as "down." However, the "up" and "down" directions are not limited to the direction of gravity or the directions when the semiconductor device is mounted.

[0013] In the present specification and the drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0014] (First embodiment) FIG. 1 is a schematic plan view illustrating an isolator 100 according to this embodiment.

[0015] The isolator 100 includes a substrate 10, a first semiconductor chip 31, a first wiring 41, a first coil 21, a second coil 22, a second wiring 42, and a second semiconductor chip 32. These components are covered with a resin part 70 (not shown in Fig. 1). The isolator 100 is, for example, a semiconductor package.

[0016] 1 does not show external connection terminals connected to the first semiconductor chip 31 and the second semiconductor chip 32. The isolator 100 has lead frames 61 and 62 as terminals, as will be shown in FIG.

[0017] A plurality of coils including a first coil 21 and a second coil 22 are provided within the substrate 10. Each of the plurality of coils has, for example, a spiral shape in a plan view. The second coil 22 is disposed above the first coil 21 (in the positive Z direction) and is spaced apart from the first coil 21. In FIG. 1, the first coil 21 and the second coil 22 overlap. The first coil 21 and the second coil 22 are provided so as to be magnetically coupled.

[0018] 1, there are provided two first coils 21 and two second coils 22. However, the numbers of first coils 21 and second coils 22 are not limited to the example shown in FIG. 1, and may be one each, or three or more each.

[0019] The first wiring 41 electrically connects the first semiconductor chip 31 and the first coil 21. The second wiring 42 electrically connects the second semiconductor chip 32 and the second coil 22.

[0020] 2 is a schematic plan view illustrating the isolator 100 according to this embodiment. Unlike FIG. 1, a portion of the isolator 100 is shown three-dimensionally to show how the first coil 21 and the second coil 22 overlap.

[0021] A first wiring 41 is provided between the first semiconductor chip 31 and the first coil 21. For example, a plurality of first wirings 41 are formed, and each is electrically connected to the center and outer edge of the first coil 21. Here, with regard to the center and outer edge of the coil, the center is defined as a portion including one end of a coil obtained, for example, by forming a conductor into a spiral shape, and the outer edge is defined as a portion including the other end. An electrical signal can be transmitted from the first semiconductor chip 31 to the first coil 21 via the first wiring 41. The electrical signal refers to, for example, the direction or magnitude of a current, or a change in the magnitude of the current over time.

[0022] 2 shows an example in which the isolator 100 has two first coils 21 and two second coils 22. The second coils 22 are disposed above the first coils 21. The second coils 22 and the second semiconductor chip 32 are electrically connected by second wiring 42. For example, a plurality of second wirings 42 are formed, and each second wiring 42 is electrically connected to the center and outer edge of the second coil 22.

[0023] The first coil 21 and the second coil 22 are magnetically coupled when a magnetic field generated by a current flowing through the first coil 21 penetrates the second coil 22, causing a current to flow through the second coil 22 due to electromagnetic induction. In FIG. 2, an upward arrow indicates a magnetic field in the positive Z direction generated by the first coil 21. Because the second coil 22 is disposed above the first coil 21, the magnetic field shown in the figure penetrates the second coil 22.

[0024] Next, the operation of the isolator 100 will be described with reference to Figure 2. In the following, an example will be described in which the first semiconductor chip 31 is on the input side and the second semiconductor chip 32 is on the output side. The isolator 100 transmits signals from the first semiconductor chip 31 to the second semiconductor chip 32, which are insulated from each other.

[0025] First, when an input signal flows to the first semiconductor chip 31, the input signal flows to the first coil 21 via the first wiring 41. The current flowing through the first coil 21 generates a magnetic field in the Z direction as shown in FIG.

[0026] The second coil 22 is spaced apart from the first coil 21, and an insulator (not shown in FIG. 2) is interposed between the first coil 21 and the second coil 22. In other words, the potential of the first coil 21 and the potential of the second coil 22 can generally be different. On the other hand, a magnetic field can pass through the insulator and reach the second coil 22 from the first coil 21. When the magnetic field in the Z direction penetrates the second coil 22, an induced current flows in the second coil 22.

[0027] The current flowing through the second coil 22 reaches the second semiconductor chip 32 through the second wiring 42. In this way, an electrical signal is transmitted from the first semiconductor chip 31 to the second semiconductor chip 32.

[0028] 3 is a cross-sectional view showing an example of the cross-sectional structure of the isolator 100. FIG. 3 is a cross-sectional view taken along the line AA′ in FIG.

[0029] 3, the isolator 100 includes a substrate 10, a first coil 21, a second coil 22, a first semiconductor chip 31, a second semiconductor chip 32, a first wiring 41, a second wiring 42, conductive layers 51 and 52, lead frames 61 and 62, and a resin part 70. Portions of the lead frames 61 and 62 protrude from the resin part 70 and are used as external connection terminals of the isolator 100.

[0030] Substrate 10 has a structure in which first rigid substrate 11, first flexible printed wiring board 12, and second rigid substrate 13 are stacked. First flexible printed wiring board 12 is provided on first rigid substrate 11. Second rigid substrate 13 is provided on first flexible printed wiring board 12. However, when simply saying that they are stacked, it does not necessarily mean that they are arranged in a predetermined order from bottom to top, but rather that they are overlapped in the Z direction.

[0031] First rigid substrate 11 and second rigid substrate 13 are rigid substrates containing, for example, epoxy resin. First flexible printed wiring board 12 is a flexible printed circuit (hereinafter also referred to as FPC board) having a film containing, for example, polyimide or liquid crystal polymer. First flexible printed wiring board 12 is formed into a film-like shape using, for example, a polyimide film or a PET film as a base material, and is a wiring board with lower rigidity than first rigid substrate 11 and second rigid substrate 13.

[0032] First flexible printed wiring board 12 is provided between first rigid substrate 11 and second rigid substrate 13. A layer containing a conductive material can be disposed on both sides of first flexible printed wiring board 12 in the vertical direction (Z direction) to form a coil. As shown in FIG. 3 , first coil 21 is formed on the lower surface side of first flexible printed wiring board 12, and second coil 22 is formed on the upper surface side of first flexible printed wiring board 12.

[0033] The first coil 21 and the second coil 22 are provided so as to face each other and spaced apart in the Z direction, which is the thickness direction of the substrate 10. The detailed internal structure of the first flexible printed wiring board 12 will be described later with reference to FIG.

[0034] The electrical connection between the first semiconductor chip 31 and the first wiring 41 and the electrical connection between the first semiconductor chip 31 and the conductive layer 51 are maintained by the adhesive layer 31a. Fig. 3 shows an example in which the first semiconductor chip 31 and the second semiconductor chip have multiple electrodes on their bottom surfaces. The multiple adhesive layers 31a and 32a are each connected to a different electrode.

[0035] The conductive layer 51 is electrically connected to the lead frame 61 by an adhesive layer 61a. The adhesive layers 31a and 61a include, for example, solder or silver paste.

[0036] The adhesive layer 32a maintains the electrical connection between the second semiconductor chip 32 and the second wiring 42, and the electrical connection between the second semiconductor chip 32 and the conductive layer 52. The conductive layer 52 is also electrically connected to the lead frame 62 by the adhesive layer 62a. The adhesive layers 32a and 62a include, for example, solder or silver paste.

[0037] Although not shown in the cross-sectional view of Figure 3, the first wiring 41 and the second wiring 42 are provided in multiple numbers, for example, and are electrically connected to the central and outer edge portions of the first coil 21 and the second coil 22.

[0038] 3, the first semiconductor chip 31 and the second semiconductor chip 32 input and output electrical signals on their bottom surfaces (surfaces in the negative Z direction). Electrical signals are transmitted from the lead frame 61 to the first wiring 41 via the first semiconductor chip 31, or in the reverse direction. For example, the first semiconductor chip 31 processes electrical signals input from the lead frame, generates electrical signals corresponding to the center and outer edge of the first coil 21, and outputs them to the multiple first wirings 41. The second semiconductor chip 32 receives electrical signals from the center and outer edge of the second coil 22 via the second wiring 42, processes the electrical signals, and outputs them to the lead frame 62.

[0039] The first semiconductor chip 31 and the first coil 21 are electrically connected by a first wiring 41 provided on the substrate 10. The first wiring 41 extends from the upper surface of the second rigid substrate 13 through the second rigid substrate 13 and the first flexible printed wiring board 12, passes through the lower surface of the first flexible wiring board 12, and reaches the first rigid substrate 11. The first wiring 41 may be provided, for example, along the Z direction between the upper surface of the second rigid substrate 13 and the lower surface of the first flexible wiring board 12. Then, the first wiring 41 extends within the XY plane on the first rigid substrate 11 and reaches below the first coil 21. Finally, the first wiring 41 extends in the Z direction and is connected to the first coil 21.

[0040] Although one example of the shape of the first wiring 41 has been described above, the shape of the first wiring 41 is not limited to this. It is desirable that the first wiring 41 have a larger proportion of the portion extending in the Z direction, because this can suppress deterioration of characteristics due to interference between the magnetic field generated by the first coil 21 and the magnetic field generated around the first wiring 41.

[0041] The second coil 22 and the second semiconductor chip 32 are electrically connected by a second wiring 42. The second wiring 42 extends from the second coil 22 through the second rigid substrate 13 in the positive Z direction from the top surface of the second rigid substrate 13. Then, it extends within the XY plane inside the second rigid substrate 13. Finally, it extends in the Z direction through the second rigid substrate 13 to reach the top surface of the second rigid substrate 13. Although the shape of the second wiring 42 has been described above, the shape of the second wiring 42 is not limited to this. It is desirable that the proportion of the portion of the second wiring 42 extending in the Z direction be as large as possible, because this can suppress deterioration of characteristics due to interference between the magnetic field penetrating the second coil 22 and the magnetic field generated around the second wiring 42.

[0042] Of the first wiring 41 and the second wiring 42, the portions that are provided in the Z direction can be formed, for example, by drilling the substrate 10 in the Z direction to form via holes and filling them with a conductive material. Also, of the first wiring 41 and the second wiring 42, the portions that are provided in the XY plane can be obtained by forming a layer containing a conductive material in a multilayer structure of the first rigid substrate 11 and the second rigid substrate 13, which are rigid substrates.

[0043] The operation of isolator 100 will be described again with reference to FIG. 3. The description will be given assuming that lead frame 61 is an input terminal and lead frame 62 is an output terminal. Lead frame 61 inputs an electrical signal to first semiconductor chip 31 via conductive layer 51. First semiconductor chip 31 performs predetermined processing on the received input signal and transmits the signal to first wiring 41. Although not shown in the cross-sectional structure of FIG. 3, it is understood that first wiring 41 has a portion connected to the center of first coil 21 and a portion connected to the outer edge.

[0044] The first coil 21 receives a signal from the first semiconductor chip 31. A current based on the input signal received by the lead frame 61 flows through the first coil 21. The current flowing through the first coil 21 generates a magnetic field in the Z direction in FIG.

[0045] When the magnetic field reaches second coil 22, which is electrically insulated from first coil 21 by first flexible printed wiring board 12, a current flows through second coil 22 due to electromagnetic induction. The current flowing through second coil 22 passes through second wiring 42 as an electrical signal and reaches second semiconductor chip 32. Second semiconductor chip 32 performs predetermined processing on the received electrical signal and outputs it to lead frame 62 via conductive layer 52.

[0046] An example of a manufacturing method for the isolator 100 according to this embodiment will be described below. First, the first coil 21, the second coil 22, the first wiring 41, the second wiring 42, and the conductive layers 51 and 52 are formed on the substrate 10. Next, the first semiconductor chip 31 and the second semiconductor chip 32 are mounted via adhesive layers 31a and 32a. Furthermore, the lead frames 61 and 62 are provided via adhesive layers 61a and 62a. Then, the lead frames 61 and 62 are sealed with a resin part 70, except for the portions that will become the input and output terminals.

[0047] Next, an example of the structure of the first flexible printed wiring board 12 will be described with reference to Fig. 4. The first flexible printed wiring board 12 has a base material 12a and an insulator 12b. The base material 12a is a film-like insulating material containing, for example, polyimide or liquid crystal polymer. The insulator 12b contains, for example, a thermosetting resin such as prepreg.

[0048] The first coil 21 is provided on the lower surface of the substrate 12a. The second coil 22 is provided on the upper surface of the substrate 12a. Insulators 12b are provided on both the upper and lower surfaces of the substrate 12a so as to cover the first coil 21 and the second coil 22. Here, the insulators 12b are provided with a thickness at least equal to or greater than the thickness in the Z direction of the first coil 21 and the second coil 22. The insulators 12b enable the upper and lower surfaces of the first flexible printed wiring board 12 to be kept flat.

[0049] The substrate 10 is formed by providing a first rigid substrate 11 and a second rigid substrate 13, which are rigid substrates, above and below the first flexible printed wiring board 12 shown in FIG.

[0050] With the isolator 100 according to this embodiment, deformation of the first flexible printed wiring board 12 is suppressed when the lead frames 61, 62, the first semiconductor chip 31, and the second semiconductor chip 32 are mounted on the substrate 10, thereby suppressing deformation of the substrate 10 and improving the reliability of the isolator. When we say deformation of the substrate, we mean bending of the substrate and displacement of the substrate.

[0051] For example, when the first semiconductor chip 31 is placed, the substrate 10 receives a local force in the Z direction in Fig. 3. This is because the first semiconductor chip 31, which is located in the positive direction of the Z direction as viewed from the substrate 10, needs to be pressed in the negative direction of the Z direction to be bonded to the substrate 10. In other words, mounting the first semiconductor chip 31 applies stress to the substrate 10.

[0052] For comparison, we will now consider the case where a semiconductor chip is mounted on a substrate consisting solely of a flexible printed wiring board. In a substrate consisting solely of a flexible printed wiring board, the stress applied to the flexible printed wiring board during mounting of a semiconductor chip or the like can cause the flexible printed wiring board to bend. Furthermore, a substrate consisting solely of a flexible printed wiring board is lighter than a substrate including a rigid board, and is therefore more susceptible to misalignment. In other words, a substrate consisting solely of a flexible printed wiring board can bend unintentionally and cause misalignment.

[0053] On the other hand, according to this embodiment, the substrate 10 has a laminated structure including a rigid substrate and a flexible printed wiring board, and deformation of the flexible printed wiring board is suppressed because the rigid substrate is greater in rigidity than the flexible printed wiring board. Therefore, deformation of the substrate 10 is suppressed, and reliability can be improved.

[0054] The substrate 10 has a first rigid substrate 11 and a second rigid substrate 13, which are rigid substrates. A first flexible printed circuit board 12, which is, for example, an FPC substrate, is sandwiched between the rigid substrates in the Z direction. Therefore, deformation of the substrate 10 requires a greater stress to deform the two-layer rigid substrate. This can further suppress deformation of the substrate 10.

[0055] By suppressing deformation of the first flexible printed wiring board 12 and improving mounting stability, failures and defects caused by deformation of the substrate 10 are suppressed, thereby improving yield. Here, high mounting stability means that the substrate 10 can maintain a stable structure without deformation when, for example, a semiconductor chip or a lead frame is mounted on the substrate 10. According to this embodiment, by suppressing deformation of the substrate 10, the reliability of the isolator 100 can be improved.

[0056] By suppressing deformation of the substrate 10, it is possible to ensure reliable electrical connection, and also to maintain good efficiency of magnetic coupling between coils by suppressing deformation of the substrate 10. Therefore, it is possible to suppress loss in signal transmission and improve signal transmission performance.

[0057] Furthermore, in the isolator 100 according to this embodiment, the first wiring 41 and the second wiring 42 are realized by internal wiring of the substrate 10, eliminating the need for electrical connection by wires or the like. In other words, wireless wiring is possible. Therefore, it is possible to omit the wire bonding process, improving manufacturing efficiency and shortening the manufacturing process.

[0058] Furthermore, according to the isolator 100 of this embodiment, by mounting the first coil 21 and the second coil 22 on the first flexible printed wiring board 12, which is a flexible printed wiring board, it is possible to precisely control the distance in the Z direction between the first coil 21 and the second coil 22 and increase the magnetic coupling constant. The shorter the distance in the Z direction between the first coil 21 and the second coil 22, the less loss there is in the magnetic field generated by the first coil 21, allowing it to reach the second coil 22. In other words, a high magnetic coupling constant means that there is less loss in the transmission of a signal as a magnetic field from the first coil 21 to the second coil 22. Compared to forming coils on a board made only of a rigid board, forming coils on the top and bottom surfaces of the thinner flexible printed wiring board 12 makes it possible to increase the magnetic coupling constant.

[0059] The first wiring 41 and the second wiring 42 include a portion that extends along the Z direction and a portion that is provided in the XY plane. Focusing on the portion of the first wiring 41 that extends from below the first semiconductor chip 31 to the first rigid substrate 11, the wiring extends along the Z direction, so the magnetic field generated when a current flows is perpendicular to the Z direction. The magnetic field generated by the first coil 21 in the Z direction is perpendicular to the magnetic field generated when a current flows through the portion of the first wiring 41 that is parallel to the Z direction. The perpendicular magnetic fields suppress magnetic field interference and can suppress deterioration of signal transmission characteristics due to noise.

[0060] Furthermore, the portions of the first wiring 41 and the second wiring 42 that are provided in the first rigid substrate 11 and the second rigid substrate 13 parallel to the XY plane are spaced apart in the Z direction from the first coil 21 and the second coil 22. Because they are spaced apart from the first coil 21 and the second coil 22, magnetic field interference can be suppressed.

[0061] Because magnetic field interference between the coils (first coil 21 and second coil 22) and the wiring (first wiring 41 and second wiring 42) depends on the layout of the wiring, etc., there is a risk that magnetic field interference will be exacerbated if the positional relationship between the coils and the wiring changes due to deformation of the substrate 10. According to this embodiment, it is possible to suppress the deterioration of characteristics due to magnetic field interference between the coils and the wiring by suppressing deformation of the substrate 10.

[0062] (First Modification of the First Embodiment) 5 shows a cross-sectional structure of an isolator 101 according to a first modification of the first embodiment. Description of parts common to the isolator 100 according to the first embodiment will be omitted.

[0063] The isolator 101 according to this embodiment differs from the isolator 100 according to the first embodiment in the structure for connecting the first semiconductor chip 31 and the first coil 21 or the second semiconductor chip 32 and the second coil 22.

[0064] The first wiring 41 has a first portion 41a formed on the first flexible printed wiring board 12. The first portion 41a of the first wiring 41 extends along the lower surface of the first flexible printed wiring board 12 and is connected to the first coil 21.

[0065] The second wiring 42 has a first portion 42a formed on the first flexible printed wiring board 12. The first portion 42a of the second wiring 42 extends along the upper surface of the first flexible printed wiring board 12 and is connected to the second coil 22.

[0066] The first portion 41a of the first wiring 41 and the first portion 42a of the second wiring 42 are provided in, for example, the insulator 12b shown in Fig. 4 of the first flexible printed wiring board 12. For example, they may be formed by adding a step of forming a layer containing a conductive material to the step of forming the insulator 12b.

[0067] For example, a plurality of first portions 41a of the first wiring 41 are provided and connected to the center and outer edge portions of the first coil 21, respectively. The plurality of first portions 41a are connected to the plurality of first wirings 41, respectively. The plurality of first portions 42a of the second wiring 42 are provided and connected to the center and outer edge portions of the second coil 22, respectively. The plurality of first portions 42a are connected to the plurality of second wirings 42, respectively.

[0068] According to the isolator 101 of this modified example, the first portions 41a and 42a are provided on the first flexible printed wiring board 12, which makes it possible to shorten the wiring length for electrically connecting the semiconductor chip (31 or 32) and the coil (21 or 22).

[0069] Since the electrical connection between the semiconductor chip and the coil can be made using shorter wiring, the magnetic field generated by the current flowing through the wiring can be reduced. This can prevent the deterioration of characteristics due to magnetic field interference. Loss in signal transmission between the first coil 21 and the second coil 22 can be further reduced.

[0070] (Second embodiment) 6 shows a cross-sectional structure of an isolator 200 according to the second embodiment. Description of parts common to the isolator 100 according to the first embodiment will be omitted.

[0071] The isolator 200 according to this embodiment has back surface electrodes 57 and 58. The back surface electrode 57 is electrically connected to the first semiconductor chip 31 (or to the adhesive layer 31a provided thereunder) via a conductive layer 53 provided under the first semiconductor chip 31 and a through conductive region 55 provided between the conductive layer 53 and the back surface electrode 57. The back surface electrode 57 is, for example, an input terminal.

[0072] The back electrode 58 is electrically connected to the second semiconductor chip 32 (or the adhesive layer 32a provided thereunder) via a conductive layer 54 provided under the second semiconductor chip 32 and a through conductive region 56 provided between the conductive layer 54 and the back electrode 58. The back electrode 58 is, for example, an output terminal.

[0073] The conductive layers 53 and 54 are formed on the second rigid substrate 13. The back electrodes 57 and 58 are formed on the first rigid substrate 11. The conductive layers 53 and 54 and the back electrodes 57 and 58 are obtained by forming a layer containing a conductive material on a rigid substrate having a multilayer structure, for example.

[0074] The through conductive regions 55, 56 penetrate the first rigid substrate 11, the first flexible printed wiring board 12, and the second rigid substrate 13 in the Z direction. The through conductive regions 55, 56 are formed, for example, by drilling the substrate 10 in the Z direction to form via holes and filling them with a conductive material.

[0075] With the isolator 200 according to this embodiment, the input terminal and output terminal can be formed by exposing electrodes on the rear surface. This makes it possible to provide a package that can be applied to a mounting form different from that of the isolator 100 according to the first embodiment. Various terminal structures for the package are possible, including the isolator 100 according to the first embodiment and the isolator 200 according to this embodiment.

[0076] (Third embodiment) 7 shows the cross-sectional structure of an isolator 300 according to the third embodiment. Description of parts common to the isolator 100 according to the first embodiment will be omitted.

[0077] The substrate 10 of the isolator 300 has a two-layer structure made up of a first rigid substrate 11 and a first flexible printed wiring board 12. The first rigid substrate 11 is a rigid substrate, and the first flexible printed wiring board 12 is a flexible printed wiring board. The first flexible printed wiring board 12 is provided on the first rigid substrate 11.

[0078] Conductive layers 51 and 52 are formed on the upper surface of first flexible printed wiring board 12. Conductive layers 51 and 52 are formed, for example, in insulator 12b of first flexible printed wiring board 12 shown in FIG.

[0079] First semiconductor chip 31 and second semiconductor chip 32 are provided on first flexible printed wiring board 12 via adhesive layers 31a and 32a. Lead frames 61 and 62 are provided on conductive layers 51 and 52 via adhesive layers 61a and 62a. Lead frame 61 is, for example, an input terminal, and lead frame 62 is, for example, an output terminal.

[0080] The first wiring 41 extends through the first flexible printed wiring board 12 and the first rigid substrate 11, and connects the adhesive layer 31a below the first semiconductor chip 31 to the first coil 21. The shape of the first wiring 41 is not limited to the shape shown in Fig. 7, and may be formed, for example, from only wiring provided inside the first flexible printed wiring board 12.

[0081] The second wiring 42 connected to the second coil 22 is formed in the insulator 12b shown in Fig. 4 of the first flexible printed wiring board 12. The second wiring 42 extends along the upper surface of the first flexible printed wiring board 12 and connects to the second coil 22. The multiple second wirings 42 connected to the center and outer edge of the second coil 22 are connected to the second semiconductor chip 32 via the adhesive layer 32a.

[0082] In the isolator 300 according to this embodiment, the substrate 10 has a two-layer structure, which allows for a smaller package. The substrate 10 is made up of a first rigid substrate 11, which is a rigid substrate, and a first flexible printed wiring board 12, which is a flexible printed wiring board. Compared to the isolator 100 according to the first embodiment, the thickness of the substrate 10 can be made thinner by the amount of the second rigid substrate 13. This allows for a smaller package.

[0083] Furthermore, since the substrate 10 includes the first rigid substrate 11, it is possible to suppress deformation of the first flexible printed wiring board 12. This makes it possible to improve the reliability of the isolator 300.

[0084] According to the example shown in FIG. 7, the electrical connection between the second coil 22 and the second semiconductor chip 32 does not require a wire bonding process, which makes it possible to shorten the manufacturing process.

[0085] Furthermore, since the wiring length of the first wiring 41 can be made shorter than in the first embodiment, it is possible to suppress deterioration of characteristics related to signal transmission due to magnetic field interference between the first wiring 41 and the first coil 21 and second coil 22 provided on the first flexible printed wiring board 12. Note that the second wiring 42 shown in Fig. 3 is not required, which further suppresses magnetic field interference.

[0086] (First modified example of the third embodiment) An isolator 301 according to a first modified example of the third embodiment will be described with reference to Fig. 8. Description of some parts common to the isolator 300 shown in Fig. 7 will be omitted.

[0087] Figure 8 shows an example in which the second semiconductor chip 32 has electrodes that transmit electrical signals from the top surface (the surface in the positive direction of the Z direction) to the bottom surface (the surface in the negative direction of the Z direction) or vice versa.

[0088] A first coil 21 is formed on the lower surface of the first flexible printed wiring board 12, and a second coil 22 is formed on the upper surface. An electrode pad 59 electrically connected to the second coil 22 is provided on the second coil 22. The other end of a wire W0 connected to the electrode pad 59 is connected to the upper surface of the second semiconductor chip 32. The wire W0 is connected to the electrode pad 59 by wire bonding.

[0089] A plurality of electrode pads 59 are provided, for example, in the XY plane, and are connected to the center and outer edge of the second coil 22, respectively, and a plurality of wires W0 are also provided.

[0090] According to the isolator 301 of the first modified example of the third embodiment, deformation of the substrate 10 can be suppressed when electrical connection is made between the top surface of a semiconductor chip (e.g., second semiconductor chip 32) and a coil (e.g., second coil 22) by wire bonding. The substrate 10 has the first rigid substrate 11, which is a rigid substrate, below the first flexible printed wiring board 12, which is an FPC board, and deformation of the first flexible printed wiring board 12 can be suppressed. The reliability of the isolator 301 can be improved.

[0091] (Fourth embodiment) 9 shows a cross-sectional structure of an isolator 400 according to the fourth embodiment. Description of parts common to the isolator 100 according to the first embodiment will be omitted.

[0092] The isolator 400 has a first semiconductor chip on a first die pad 81. It also has a substrate 10 on a second die pad 82. It has a second semiconductor chip 32 on a third die pad 83. The first die pad 81, the second die pad 82, and the third die pad 83 are provided spaced apart from each other.

[0093] The first semiconductor chip 31 has electrodes on its upper surface, and its lower surface in contact with the first die pad 81 is electrically insulated from the first die pad 81. The second semiconductor chip 32 has electrodes on its upper surface, and its lower surface in contact with the third die pad 83 is electrically insulated from the third die pad 83.

[0094] As will be described later, wiring including a coil is provided inside the substrate 10, and part of the wiring is electrically connected to the second die pad .

[0095] The first semiconductor chip 31 and the second die pad 82 are connected via a wire W1. The wire W1 contacts the top surface of the first semiconductor chip 31 and the top surface of the second die pad 82. The substrate 10 and the second semiconductor chip 32 are connected via a wire W2.

[0096] The substrate 10 has a two-layer structure in which a first rigid substrate 11 and a first flexible printed wiring board 12 are stacked. The first rigid substrate 11 is a rigid substrate. The first flexible printed wiring board 12 is an FPC substrate. In the example shown in FIG. 9, the first rigid substrate 11 is provided on the first flexible printed wiring board 12.

[0097] A first coil 21 and a second coil 22 are provided on the first flexible printed wiring board 12. The internal structure of the first flexible printed wiring board 12 may be similar to that of the example shown in FIG. 4, for example. The first coil 21 is provided on the lower surface of the first flexible printed wiring board 12, and the second coil 22 is provided on the upper surface of the first flexible printed wiring board 12. The first coil 21 is electrically connected to the second die pad 82. The second coil 22 is electrically insulated from the first coil 21.

[0098] A third wiring 43 connected to the second coil 22 is provided so as to penetrate the first rigid substrate 11 in the Z direction. The third wiring 43 is connected to an electrode pad 59 provided on the upper surface of the first rigid substrate. A wire W2 is connected to the electrode pad 59.

[0099] The isolator 400 also has external terminals 84 and 85. The external terminals 84 and 85 are provided spaced apart from the first die pad 81, the second die pad 82, and the third die pad 83, respectively. The external terminal 84 is, for example, an input terminal. The external terminal 85 is, for example, an output terminal.

[0100] The external terminal 84 and the first semiconductor chip 31 are electrically connected via wire W3. The external terminal 85 and the second semiconductor chip 32 are electrically connected via wire W4. That is, the first semiconductor chip 31 has a plurality of electrodes on its upper surface, one of which is connected to the second die pad 82 via wire W1 and the other of which is connected to the external terminal 84 via wire W3. The second semiconductor chip 32 has a plurality of electrodes on its upper surface, one of which is connected to the electrode pad 59 via wire W2 and the other of which is connected to the external terminal 85 via wire W4.

[0101] Next, a description will be given of the operation of the isolator 400. An example will be described in which the external terminal 84 is an input terminal and the external terminal 85 is an output terminal.

[0102] An electrical signal input to external terminal 84 reaches first semiconductor chip 31 via wire W3. First semiconductor chip 31 performs predetermined processing on the received electrical signal and outputs it to wire W1. The signal output from first semiconductor chip 31 reaches first coil 21 via wire W1 and second die pad 82.

[0103] The first coil 21 generates a magnetic field in response to the received electrical signal. For example, in FIG. 9, a magnetic field in the Z direction is generated. The magnetic field in the Z direction passes through the second coil 22, which is separated from the first coil in the Z direction. A current flows through the second coil 22 due to electromagnetic induction. A signal is transmitted between the first coil and the second coil via the magnetic field.

[0104] The signal transmitted to the second coil 22 flows to the wire W2 via the third wiring 43 and the electrode pad 59. The signal is transmitted to the second semiconductor chip 32 through the wire W2. The second semiconductor chip 32 performs predetermined processing on the signal and outputs it to the wire W4. The signal transmitted by the wire W4 to the external terminal 85 becomes the output signal.

[0105] According to the isolator 400 of this embodiment, it is possible to reduce the thickness of the substrate 10 and the size of the package, while suppressing deformation of the first flexible printed wiring board 12 and improving reliability.

[0106] The substrate 10 has a two-layer structure of a first rigid substrate 11 and a first flexible printed wiring board 12. The thickness of the substrate 10 can be made thinner than that of the isolator 100 according to the first embodiment. Reducing the thickness of the substrate 10 allows for a more compact package.

[0107] The first rigid substrate 11 is a rigid substrate, and can suppress deformation of the first flexible printed wiring board 12 when, for example, the wire W2 is provided by wire bonding, thereby improving the reliability of the isolator 400.

[0108] Note that first rigid substrate 11 may have an area smaller than first flexible printed wiring board 12. Electrode pads 59 are provided on first rigid substrate 11. Stress is applied to substrate 10 during the wire bonding process of connecting wire W2 to electrode pad 59, but because first rigid substrate 11, which is a rigid substrate, is located at least below electrode pad 59, the stress during mounting of wire W2 can be distributed to first rigid substrate 11. Reducing the amount of material constituting first rigid substrate 11 allows for reduction in manufacturing costs.

[0109] According to at least one of the embodiments described above, the substrate 10 has at least a two-layer structure consisting of a rigid substrate layer and a flexible printed wiring board layer, which can suppress deformation of the first flexible printed wiring board 12 on which the first coil 21 and the second coil are arranged. The mounting stability of the isolator is improved, and failures and defects are suppressed, thereby improving the reliability of the isolator. Furthermore, by forming coils on the top and bottom surfaces of the first flexible printed wiring board 12 and shortening the distance in the Z direction between the first coil 21 and the second coil 22, the magnetic coupling coefficient can be increased, improving signal transmission performance. Furthermore, with regard to the structure connecting the first semiconductor chip 31 (second semiconductor chip 32) and the first coil 21 (second coil 22), deterioration of signal transmission characteristics due to magnetic field interference from wiring can be suppressed.

[0110] The embodiments have been described above with reference to specific examples. However, the embodiments are not limited to these specific examples. In other words, designs that are appropriately modified by a person skilled in the art from these specific examples are also included within the scope of the embodiments as long as they have the characteristics of the embodiments. The elements, as well as their arrangement, materials, conditions, shapes, sizes, etc., of the above-mentioned specific examples are not limited to those exemplified and can be modified as appropriate.

[0111] Although the above description has been given of an isolator using a coil, it is also possible to apply the present invention to an isolator using a capacitor.

[0112] Furthermore, the elements of each of the above-described embodiments can be combined to the extent technically possible, and combinations of these are also included within the scope of the embodiments as long as they include the features of the embodiments. In addition, within the scope of the concept of the embodiments, a person skilled in the art may conceive of various modifications and alterations, and it is understood that these modifications and alterations also fall within the scope of the embodiments.

[0113] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0114] 100, 101, 200, 300, 301, 400, 401... Isolators 11. First rigid board 12. First flexible printed wiring board 13 Second rigid board 21. First coil 22 Second coil 31. First semiconductor chip 32. Second semiconductor chip 31a, 32a...adhesive layer 41...1st wiring 42...2nd wiring 41a...first part 42a...first part 43...Third wiring 51, 52, 53, 54...Conductive layers 55, 56...through conductive area 57, 58 Back electrode 61, 62 Lead frame 61a, 62a...Adhesive layer 70···Resin part 81 First die pad 82 Second die pad 83 Third die pad 84, 85 External terminals W0, W1, W2, W3, W4... wires

Claims

1. a substrate including a first rigid substrate that is a rigid substrate, and a first flexible printed wiring board that is a flexible printed wiring board stacked on the first rigid substrate in a first direction; a first coil provided on the first flexible printed wiring board; a second coil provided on the first flexible printed wiring board and facing the first coil in the first direction and spaced apart from the first coil; a first semiconductor chip provided on the substrate; a second semiconductor chip provided on the substrate; a first wiring provided in the substrate and connecting the first semiconductor chip and the first coil; a second wiring provided in the substrate and connecting the second semiconductor chip and the second coil; An isolator having

2. the first flexible printed wiring board is provided on the first rigid substrate, The substrate further includes a second rigid substrate provided on the first flexible printed wiring board. The isolator of claim 1 .

3. the first wiring extends in the first direction from an upper surface of the second rigid substrate to a lower surface of the first flexible printed wiring board; The isolator of claim 2 .

4. the first wiring is formed on the first flexible printed wiring board, extends along a lower surface of the first flexible printed wiring board, and has a first portion connected to the first coil; The isolator of claim 3 .

5. a resin portion that seals the first semiconductor chip and the second semiconductor chip; a plurality of lead frames electrically connected to the first semiconductor chip or the second semiconductor chip, respectively; further comprising The isolator of claim 3 .

6. a resin portion that seals the first semiconductor chip and the second semiconductor chip; a plurality of back electrodes provided on the first rigid substrate and exposed from the resin portion; a through-hole conductive region extending in the first direction within the substrate; a conductive layer connecting the through conductive region and the first semiconductor chip or the second semiconductor chip; 4. The isolator of claim 3 further comprising:

7. a first die pad; a first semiconductor chip provided on the first die pad; a second die pad provided spaced apart from the first die pad; a substrate provided on the second die pad, the substrate including: a first rigid substrate that is a rigid substrate; and a first flexible printed wiring board that is a flexible printed wiring board that is stacked on the first rigid substrate in a first direction; a first coil provided on the first flexible printed wiring board; a second coil provided on the first flexible printed wiring board and facing the first coil in the first direction and spaced apart from the first coil; an electrode pad provided on the substrate and connected to the second coil by a third wiring provided in the substrate; a third die pad provided at a distance from the first die pad and the second die pad; a second semiconductor chip provided on the third die pad; a first wire connecting the first semiconductor chip and the second die pad; a second wire connecting the electrode pad and the second semiconductor chip; An isolator having

8. The first flexible printed wiring board is a substrate having the first coil provided on a lower surface and the second coil provided on an upper surface; and insulators provided on each of an upper surface and a lower surface of the base material so as to sandwich the base material in the first direction, the insulators having a thickness equal to or greater than the thickness of the first coil or the second coil in the first direction.

8. The isolator according to claim 1.

9. the substrate is made of a film-like insulating material containing polyimide, The insulator includes a thermosetting resin.

9. The isolator of claim 8.

Images