Isolator

Abstract

Embodiments provide an isolator capable of improving the power efficiency of a transformer. According to one embodiment, an isolator includes a first pad, a second pad, a first coil, an insulating layer, a third pad, a fourth pad, and a second coil. The first coil includes a first wiring and a second wiring. The first coil is connected to the first pad and the second pad. The second coil includes a third wiring and a fourth wiring. The second coil is disposed so as to face the first coil with an insulating layer interposed therebetween. The second coil is connected to the third pad and the fourth pad. The first wiring and the second wiring are connected in parallel with each other between the first pad and the second pad. The third wiring and the fourth wiring are connected in parallel between the third pad and the fourth pad.

Description

[0001] Reference to related applications

[0002] This application claims the priority of Japanese Patent Application No. 2023-205937 (filing date: December 6, 2023) as a basic application. The present application incorporates all the contents of the basic application by reference. Technical Field

[0003] Embodiments of the present invention relate to isolators. Background Art

[0004] There is known an isolator that transmits a signal to a transmission side circuit and a reception side circuit in a state where the transmission side circuit and the reception side circuit are insulated from each other. Summary of the invention

[0005] An object of the present invention is to provide an isolator capable of improving the power efficiency of a transformer.

[0006] The isolator of the embodiment comprises: a first pad, a second pad, a first coil, an insulating layer, a third pad, a fourth pad, and a second coil. The first coil includes a first wiring and a second wiring. The first coil is connected to the first pad and the second pad. The second coil includes a third wiring and a fourth wiring. The second coil is arranged to be opposite to the first coil via the insulating layer. The second coil is connected to the third pad and the fourth pad. The first wiring and the second wiring are connected in parallel between the first pad and the second pad. The third wiring and the fourth wiring are connected in parallel between the third pad and the fourth pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a plan view showing an example of the planar layout of the isolator according to the first embodiment.

[0008] Figure 2 An example of the cross-sectional structure of the isolator according to the first embodiment is shown along Figure 1 Cross-sectional view of the S1-S1 line.

[0009] Figure 3 It is a plan view showing an example of a planar layout of a primary circuit in a wiring board included in the isolator according to the first embodiment.

[0010] Figure 4 This is a diagram for explaining the cancellation of magnetic flux caused by the phase shift of currents flowing through two wirings.

[0011] Figure 5 This is a plan view showing an example of a planar layout of a secondary circuit in a wiring board included in the isolator according to the first embodiment.

[0012] Figure 6 This is a perspective view showing an example of the structure of a wiring board included in the isolator according to the first embodiment.

[0013] Figure 7 An example of a cross-sectional structure of a wiring board included in the isolator of the first embodiment is shown along Figure 6 Cross-sectional view of the S2-S2 line.

[0014] Figure 8 An example of a cross-sectional structure of a wiring board included in the isolator of the first embodiment is shown along Figure 6 Cross-sectional view of the S3-S3 line.

[0015] Fig. 9 It is a plan view showing an example of a planar layout of a primary circuit in a wiring board included in the isolator according to the second embodiment.

[0016] Fig.10 It is a plan view showing an example of a planar layout of a secondary circuit in a wiring board included in the isolator according to the second embodiment.

[0017] Fig.11 It is a perspective view showing an example of the structure of a wiring board included in the isolator according to the second embodiment.

[0018] Fig.12 is a diagram showing an example of a cross-sectional structure of a wiring board included in the isolator of the second embodiment, along the Fig.11 Cross-sectional view of the S4-S4 line.

[0019] Fig.13 is a diagram showing an example of a cross-sectional structure of a wiring board included in the isolator of the second embodiment, along the Fig.11 Cross-sectional view of line S5-S5.

[0020] Fig.14 is a diagram showing an example of a cross-sectional structure of a wiring board included in the isolator of the second embodiment, along the Fig.11 Cross-sectional view of line S6-S6.

[0021] Fig.15 It is a plan view showing an example of a planar layout of an isolator according to a modified example of the second embodiment.

[0022] Fig.16 An example of a cross-sectional structure of an isolator according to a modified example of the second embodiment is shown along Fig.15 Cross-sectional view of line S7-S7.

[0023] Fig.17 An example of a cross-sectional structure of an isolator according to a modified example of the second embodiment is shown along Fig.15 Cross-sectional view of line S8-S8.

[0024] Fig.18 It is a plan view showing an example of a planar layout of a primary circuit in a wiring board included in an isolator according to a modified example of the second embodiment.

[0025] Fig.19 It is a plan view showing an example of a planar layout of a secondary circuit in a wiring board included in an isolator according to a modified example of the second embodiment.

[0026] Fig. 20 This is a perspective view showing an example of the structure of a wiring board included in an isolator according to a modified example of the second embodiment.

[0027] Fig.21 FIG. 1 is a diagram showing an example of a cross-sectional structure of a wiring board included in an isolator according to a modified example of the second embodiment, along the Fig. 20 Cross-sectional view of line S9-S9.

[0028] Fig. 22 FIG. 1 is a diagram showing an example of a cross-sectional structure of a wiring board included in an isolator according to a modified example of the second embodiment, along the Fig. 20 Cross-sectional view of the S10-S10 line.

[0029] Fig.23 FIG. 1 is a diagram showing an example of a cross-sectional structure of a wiring board included in an isolator according to a modified example of the second embodiment, along the Fig. 20 Cross-sectional view of line S11-S11.

[0030] Fig.24 It is a plan view showing an example of a planar layout of a primary circuit in a wiring board included in an isolator according to a modified example of the first embodiment.

[0031] Fig.25 It is a plan view showing an example of a planar layout of a secondary circuit in a wiring board included in an isolator according to a modified example of the first embodiment.

[0032] Fig.26 This is a perspective view showing an example of the structure of a wiring board included in an isolator according to a modified example of the first embodiment.

[0033] Fig. 27 FIG. 1 is a diagram showing an example of a cross-sectional structure of a wiring board included in an isolator according to a modified example of the first embodiment, along the Fig.26 Cross-sectional view of the S12-S12 line.

[0034] Fig.28 FIG. 1 is a diagram showing an example of a cross-sectional structure of a wiring board included in an isolator according to a modified example of the first embodiment, along the Fig.26 Cross-sectional view of line S13-S13.

[0035] Fig.29 FIG. 1 is a diagram showing an example of a cross-sectional structure of a wiring board included in an isolator according to a modified example of the first embodiment, along the Fig.26 Cross-sectional view of line S14-S14. DETAILED DESCRIPTION

[0036] Hereinafter, the embodiments will be described with reference to the accompanying drawings. The dimensions and ratios of the drawings are not necessarily the same as in reality. In addition, in the following description, the same reference numerals are sometimes used to mark the components having substantially the same function and structure, and repeated descriptions are omitted. In the case where there is no particular distinction between the components having the same structure, different characters or numbers are sometimes added to the end of the same reference numeral. In addition, unless explicitly or obviously excluded, all descriptions of a certain embodiment also apply to the description of another embodiment.

[0037] 1. First Implementation

[0038] The isolator of the first embodiment is described below, taking as an example a digital isolator in which a coil connected to a transmitting circuit is magnetically coupled to a coil connected to a receiving circuit while insulating the transmitting circuit from the receiving circuit, thereby enabling a signal to be transmitted from the transmitting circuit to the receiving circuit.

[0039] 1.1 Structure of Isolator

[0040] use Figure 1 as well as Figure 2 The structure of the isolator will be described. Figure 1 This is a plan view showing an example of the planar layout of the isolator. Figure 2 An example of the cross-sectional structure of an isolator is shown along Figure 1 Cross-sectional view of the S1-S1 line.

[0041] The isolator 1 is, for example, a semiconductor package. Figure 1 as well as Figure 2 As shown, the isolator 1 includes die pads 10 and 20, semiconductor chips 11 and 21, leads 15 and 25, frames 30a and 30b, a transformer TR, and an insulating member 100. Figure 1 In the figure, the insulating member 100 is omitted.

[0042] The die pads 10 and 20 are members for supporting semiconductor chips. The die pad 10 supports the semiconductor chip 11 . The die pad 20 supports the semiconductor chip 21 .

[0043] The leads 15 and 25 are components for connecting the semiconductor chip to external wiring. The isolator 1 includes a plurality of leads 15 and a plurality of leads 25. The leads 15 connect the semiconductor chip 11 to external wiring via bonding wires 16. The number of bonding wires 16 is the same as the number of leads 15. The leads 25 connect the semiconductor chip 21 to external wiring via bonding wires 26. The number of bonding wires 26 is the same as the number of leads 25.

[0044] The frames 30a and 30b are components that support the transformer TR and connect the semiconductor chip 21 to the transformer TR. The frame 30a connects the semiconductor chip 21 to the transformer TR via the bonding wires 24a and the through holes 32a. The frame 30b connects the semiconductor chip 21 to the transformer TR via the bonding wires 24b and the through holes 32b.

[0045] The die pads 10 and 20, the leads 15 and 25, and the frames 30a and 30b constitute a lead frame. Hereinafter, the die pads 10 and 20, the leads 15 and 25, and the frames 30a and 30b are collectively referred to as a "lead frame LF". The lead frame LF has, for example, a plate-like shape. The lead frame LF is made of a conductive material. The lead frame LF includes, for example, a metal material.

[0046] Hereinafter, the plane parallel to the plane of the lead frame LF is referred to as the XY plane. The directions perpendicularly intersecting each other in the XY plane are referred to as the X direction and the Y direction. The direction intersecting the XY plane is referred to as the Z direction. The direction from the lead frame LF toward the semiconductor chips 11 and 21 in the Z direction is also referred to as the upward direction.

[0047] like Figure 1 As shown, the die pads 10 and 20 are arranged to be separated from each other in the X direction. The frames 30a and 30b are arranged to be separated from each other in the Y direction. The frames 30a and 30b are arranged between the die pad 10 and the die pad 20 in the X direction and are separated from the die pads 10 and 20. The plurality of leads 15 are arranged to be separated from each other in the Y direction. The plurality of leads 15 are arranged on the side of the die pad 10 opposite to the side where the frames 30a and 30b are arranged in the X direction and are separated from the die pad 10. The plurality of leads 25 are arranged to be separated from each other in the Y direction. The plurality of leads 25 are arranged on the side of the die pad 20 opposite to the side where the frames 30a and 30b are arranged in the X direction and are separated from the die pad 20.

[0048] The semiconductor chips 11 and 21 are, for example, IC (Integrated Circuit) chips, and are arranged to be separated from each other in the X direction.

[0049] The semiconductor chip 11 includes a circuit 12. The circuit 12 includes a signal transmission and reception circuit and a modulation and demodulation circuit. The circuit 12 is connected to a bonding wire 14a via a wiring (not shown) in the semiconductor chip 11. The circuit 12 is connected to a bonding wire 14b via a wiring (not shown) in the semiconductor chip 11. The circuit 12 is connected to a bonding wire 16 via a wiring (not shown) in the semiconductor chip 11.

[0050] The semiconductor chip 21 includes a circuit 22. The circuit 22 includes a signal transmission and reception circuit and a modulation and demodulation circuit. The circuit 22 is connected to the bonding wire 24a via a wiring (not shown) in the semiconductor chip 21. The circuit 22 is connected to the bonding wire 24b via a wiring (not shown) in the semiconductor chip 21. The circuit 22 is connected to the bonding wire 26 via a wiring (not shown) in the semiconductor chip 21.

[0051] The transformer TR is, for example, an insulating transformer and is disposed between the semiconductor chip 11 and the semiconductor chip 21 in the X direction and is separated from the semiconductor chips 11 and 21 .

[0052] Transformer TR includes, for example, a wiring board 31. Wiring board 31 is, for example, a flexible printed wiring board (FPC: Flexible Printed Circuits) having flexibility. Wiring board 31 has, for example, a plate shape.

[0053] The wiring board 31 includes, for example, a primary circuit FC, an insulating layer, and a secondary circuit SC, which will be described later. The primary circuit FC includes a coil CL1, which will be described later. The secondary circuit SC includes a coil CL2, which will be described later. The wiring board 31 is configured to transmit a signal from the circuit 12 to the circuit 22 or from the circuit 22 to the circuit 12, using the coils CL1 and CL2, while insulating the circuit 12 in the semiconductor chip 11 from the circuit 22 in the semiconductor chip 21. The wiring board 31 will be described in detail later.

[0054] When a signal is transmitted from circuit 12 to circuit 22, circuit 12 functions as a transmission side circuit and circuit 22 functions as a reception side circuit. On the other hand, when a signal is transmitted from circuit 22 to circuit 12, circuit 22 functions as a transmission side circuit and circuit 12 functions as a reception side circuit.

[0055] The insulating member 100 includes, for example, insulating resin. The die pads 10 and 20 , the semiconductor chips 11 and 21 , the bonding wires 14 a , 14 b , 16 , 24 a , 24 b and 26 , the frames 30 a and 30 b , the wiring board 31 , and the through holes 32 a and 32 b are sealed by the insulating member 100 .

[0056] like Figure 2As shown in FIG. 1 , a semiconductor chip 11 is provided on a die pad 10 via an adhesive member 13 . On the semiconductor chip 11 , one end of a bonding wire 14 a and one end of a bonding wire 16 are provided.

[0057] The other end of the bonding wire 16 is provided on the lead 15 .

[0058] The semiconductor chip 21 is provided on the die pad 20 via the adhesive member 23. On the semiconductor chip 21, one end of the bonding wire 24a and one end of the bonding wire 26 are provided.

[0059] The other end of the bonding wire 26 is provided on the lead 25 .

[0060] The other end of the bonding wire 24a is provided on the frame 30a. In addition, a through hole 32a is provided on the frame 30a. The wiring board 31 is provided on the through hole 32a. The other end of the bonding wire 14a is provided on the wiring board 31.

[0061] The die pads 10 and 20, the semiconductor chips 11 and 21, the adhesive members 13 and 23, the bonding wires 14a, 16, 24a and 26, a portion of the lead 15, a portion of the lead 25, the frame 30a, the wiring board 31, and the through hole 32a are covered by the insulating member 100. The leads 15 and 25 are fixed by the insulating member 100 and have portions exposed outside the insulating member 100.

[0062] In addition, the cross-sectional structure on the surface including the bonding wires 14b and 24b and the through hole 32b is similar to Figure 2 The cross-sectional structure on the surface including the bonding wires 14a and 24a and the through hole 32a shown is the same. Specifically, one end of the bonding wire 14b is provided on the semiconductor chip 11. One end of the bonding wire 24b is provided on the semiconductor chip 21. The other end of the bonding wire 24b is provided on the frame 30b. In addition, the through hole 32b is provided on the frame 30b. The wiring board 31 is provided on the through hole 32b. The other end of the bonding wire 14b is provided on the wiring board 31.

[0063] 1.2 Structure of wiring board

[0064] Regarding the structure of the wiring board 31, Figure 3 as well as Figures 5 to 8 Provide explanation.

[0065] Figure 3 FIG. 3 is a top view showing an example of the planar layout of the primary circuit FC in the wiring board 31. Figure 3 As shown, the wiring board 31 includes pads Pd1 and Pd2, and a coil CL1. Figure 3 In the figure, illustration of the secondary circuit SC and the insulating layer in the wiring board 31 is omitted.

[0066] The pad Pd1 is a component that connects the coil CL1 to the bonding wire 14a. The pad Pd2 is a component that connects the coil CL1 to the bonding wire 14b. The pad Pd1 includes a base BP1 and a protrusion PP1 protruding from the base BP1. The protrusion PP1 protrudes from the base BP1 in the X direction. In more detail, the protrusion PP1 protrudes from the base BP1 to the side opposite to the pad Pd2. The pad Pd2 includes a base BP2 and a protrusion PP2 protruding from the base BP2. The protrusion PP2 protrudes from the base BP2 in the Y direction. In more detail, the protrusion PP2 protrudes from the base BP2 to the pad Pd1 side. In this way, the pads Pd1 and Pd2 have, for example, a roughly L-shaped shape when viewed from above (when viewed from the upper side of the paper). The pads Pd1 and Pd2 are made of a conductive material.

[0067] Coil CL1 includes wiring 41 and wiring 42.

[0068] The wiring 41 has a first end E1 and a second end E2. The first end E1 is connected to the base BP1 of the pad Pd1. The second end E2 is connected to the base BP2 of the pad Pd2. The wiring 41 has a spiral shape that is clockwise from the first end E1 and faces outward in a plan view.

[0069] Wiring 42 has a third end E3 and a fourth end E4. The third end E3 is connected to protrusion PP1 of pad Pd1. The fourth end E4 is connected to protrusion PP2 of pad Pd2. Wiring 42 is separated from wiring 41, for example, and has a swirl shape that rotates clockwise from the third end E3 and faces outward in a plan view.

[0070] The wirings 41 and 42 are made of a conductive material. The wirings 41 and 42 include copper, for example.

[0071] The coil CL1 is connected to the pads Pd1 and Pd2 by the above structure. More specifically, in the present embodiment, the wirings 41 and 42 are connected in parallel to each other between the pads Pd1 and Pd2.

[0072] In addition, in the present embodiment, the wirings 41 and 42 are designed with the same size and the same design rules (line width-line pitch) as when the coil CL1 is formed by a single-layer wiring.

[0073] In such a design, for example, the spiral shape of the wiring 41 and 42 is formed into an ellipse. That is, the outer diameter of the coil CL1 in the Y direction is formed to be longer than the outer diameter of the coil CL1 in the X direction. In addition, the spiral shape of the wiring 41 and 42 can be rectangular or polygonal.

[0074] In the Y direction, the total number of turns of the wirings 41 and 42 on the pad Pd2 side of the pad Pd1 is ( Figure 3 In the example of 2) the total number of turns of the wirings 41 and 42 on the side opposite to the pad Pd2 of the pad Pd1 is formed ( Figure 3 3) is less in the example. Therefore, the sum of the length of wiring 41 and the length of wiring 42 is shorter than the length of the wiring when coil CL1 is formed by a single-layer wiring. In addition, the sum of the length of wiring 41 and the length of wiring 42 can also be equal to the length of the wiring when coil CL1 is formed by a single-layer wiring.

[0075] Furthermore, in the present embodiment, the electrical length of the wiring 42 is designed to be equal to the electrical length of the wiring 41. That is, the relationship between the electrical length of the wiring 42 and the electrical length of the wiring 41 is expressed by the following formula (1).

[0076] The electrical length of the wiring 42 = the electrical length of the wiring 41 (1)

[0077] The electrical length is the length calculated based on the speed of the current propagating in the wiring. The speed of the current propagating in the wiring is calculated based on the non-dielectric constant and non-magnetic permeability of the wiring. The speed of the current propagating in the wiring is slower than the speed in a vacuum. The wavelength of the current propagating in the wiring is shorter than the wavelength in a vacuum. For example, when the wavelength of the current propagating in the wiring is 50 [cm], 1 / 4 of the wavelength is 12.5 [cm], and 1 / 4 of the electrical length is about 6 [cm].

[0078] Here, the power efficiency of the transformer TR is described. The power efficiency of the transformer TR is determined by the product of the coupling coefficient k and the Q value. In addition, the power efficiency of the transformer TR also affects the power efficiency of the isolator 1.

[0079] The coupling coefficient k is a value indicating the degree of coupling between two coils constituting the transformer TR. The coupling coefficient k is expressed by the following equation (2).

[0080] k = M / √(L1×L2) (2)

[0081] In the above equation (2), M is the mutual inductance, L1 is the self-inductance of one coil, and L2 is the self-inductance of the other coil.

[0082] The Q value is a value indicating the quality of the coil. The higher the Q value, the lower the loss to high frequencies. The Q value is expressed by the following formula (3).

[0083] Q = ωL / R (3)

[0084] In the above equation (3), ω is the frequency of the current, L is the self-inductance of the coil, and R is the resistance of the coil.

[0085] According to the above formula (3), the smaller the coil resistance R, the larger the Q value. As described above, the power efficiency of the transformer TR depends on the product of the coupling coefficient k and the Q value, so the larger the Q value, the higher the power efficiency of the transformer TR.

[0086] Figure 4 1 is a diagram illustrating the cancellation of magnetic flux caused by the phase shift of the current flowing through the two wirings. Figure 4 In the figure, the waveform of the current flowing through the wiring on one side and the waveform of the current flowing through the wiring on the other side are represented by solid lines and dotted lines, respectively. Hereinafter, the wiring on one side is also referred to as "wiring A". The wiring on the other side is also referred to as "wiring B". The vertical axis represents the current value. The horizontal axis represents the frequency of the current. Figure 4 In the example of FIG. 1 , a state in which the phase of the current flowing through the wiring A and the current flowing through the wiring B is shifted is shown. In addition, a case in which the frequency of the current flowing through the wirings A and B is 600 [MHz] is shown.

[0087] like Figure 4 As shown in FIG. 1 , if the phase of the current flowing through wiring A and the current flowing through wiring B is offset, the magnetic flux Φ1 generated by the current flowing through wiring A and the magnetic flux Φ2 generated by the current flowing through wiring B will cancel each other out. Figure 4 In the example of , the region where the magnetic flux cancellation occurs is indicated by oblique lines as the magnetic flux cancellation region. When the magnetic flux cancellation occurs, the sum of the magnetic flux Φ1 and the magnetic flux Φ2 becomes smaller than when the magnetic flux cancellation does not occur.

[0088] In a transformer in which two coils including wiring A and wiring B are arranged opposite to each other, when the above-mentioned magnetic flux cancellation occurs, the coupling coefficient k is reduced compared to the case where the above-mentioned magnetic flux cancellation does not occur. As described above, the power efficiency of the transformer TR depends on the product of the coupling coefficient k and the Q value, so the larger the coupling coefficient k, the higher the power efficiency of the transformer TR.

[0089] Figure 5 31 is a top view showing an example of a planar layout of the secondary circuit SC in the wiring board 31. Figure 5 As shown, the wiring board 31 includes pads Pd3 and Pd4, and a coil CL2. Figure 5 In the figure, the primary circuit FC and the insulating layer in the wiring board 31 are omitted.

[0090] The configuration of the secondary circuit SC is the same as that of the primary circuit FC. Specifically, it is as follows.

[0091] The pad Pd3 is a component that connects the coil CL2 to the through hole 32a. The pad Pd4 is a component that connects the coil CL2 to the through hole 32b. The pad Pd3 includes a base BP3 and a protrusion PP3 protruding from the base BP3. The protrusion PP3 protrudes from the base BP3 in the X direction. In more detail, the protrusion PP3 protrudes from the base BP3 to the side opposite to the pad Pd4. The pad Pd4 includes a base BP4 and a protrusion PP4 protruding from the base BP4. The protrusion PP4 protrudes from the base BP4 in the Y direction. In more detail, the protrusion PP4 protrudes from the base BP4 to the pad Pd3 side. In this way, the pads Pd3 and Pd4 have, for example, a roughly L-shaped shape when viewed from above. The pads Pd3 and Pd4 are made of a conductive material.

[0092] Coil CL2 includes wiring 51 and wiring 52.

[0093] The wiring 51 has a fifth end E5 and a sixth end E6. The fifth end E5 is connected to the base BP3 of the pad Pd3. The sixth end E6 is connected to the base BP4 of the pad Pd4. The wiring 51 has a spiral shape that rotates clockwise from the fifth end E5 and faces outward in a plan view.

[0094] Wiring 52 has a seventh end E7 and an eighth end E8. Seventh end E7 is connected to protrusion PP3 of pad Pd3. Eighth end E8 is connected to protrusion PP4 of pad Pd4. Wiring 52 is separated from wiring 51, for example, and has a swirl shape that rotates clockwise from seventh end E7 and faces outward in a plan view.

[0095] The wirings 51 and 52 are made of a conductive material. The wirings 51 and 52 include copper, for example.

[0096] According to the above structure, the coil CL2 is connected to the pads Pd3 and Pd4. More specifically, in the present embodiment, the wirings 51 and 52 are connected in parallel to each other between the pads Pd3 and Pd4.

[0097] In addition, in this embodiment, the wirings 51 and 52 are designed with the same size and the same design rules (line width-line spacing) as when the coil CL2 is formed by a single-layer wiring.

[0098] In such a design, for example, the spiral shape of the wiring 51 and 52 is formed into an ellipse. That is, the outer diameter of the coil CL2 in the Y direction is formed to be longer than the outer diameter of the coil CL2 in the X direction. In addition, the spiral shape of the wiring 51 and 52 can be rectangular or polygonal.

[0099] In addition, in the Y direction, the total number of turns of the wirings 51 and 52 on the pad Pd4 side of the pad Pd3 ( Figure 5In the example of 2), the total number of turns of the wirings 51 and 52 on the side opposite to the pad Pd4 of the pad Pd3 is ( Figure 5 3) is less in the example. Therefore, the sum of the length of wiring 51 and the length of wiring 52 is shorter than the length of the wiring when coil CL2 is formed by a single-layer wiring. In addition, the sum of the length of wiring 51 and the length of wiring 52 can also be equal to the length of the wiring when coil CL2 is formed by a single-layer wiring.

[0100] Furthermore, in the present embodiment, the electrical length of the wiring 52 is designed to be equal to the electrical length of the wiring 51 .

[0101] Figure 6 It is a perspective view showing an example of the structure of wiring board 31 . Figure 7 An example of a cross-sectional structure of the wiring board 31 is shown along Figure 6 Cross-sectional view of the S2-S2 line. Figure 8 An example of a cross-sectional structure of the wiring board 31 is shown along Figure 6 Cross-sectional view of the S3-S3 line.

[0102] like Figure 6 to Figure 8 As shown, the wiring board 31 includes pads Pd1 and Pd2, a coil CL1, pads Pd3 and Pd4, a coil CL2, and insulating layers 61 to 65. Figure 6 to Figure 8 Also shown are the bonding wires 14a, 14b, 24a and 24b, the frames 30a and 30b, and the through holes 32a and 32b. Figure 6 In the figure, illustration of the through holes 32a and 32b and the insulating layers 61 to 65 is omitted.

[0103] like Figure 6 As shown, the coil CL1 is arranged above the coil CL2 in the Z direction. That is, the coil CL1 is arranged at a position overlapping with the coil CL2 in the Z direction. In other words, the coil CL2 is arranged to be opposite to the coil CL1 through the insulating layer 63. Figure 6 In the example, pads Pd1 and Pd2, and coil CL1, pads Pd3 and Pd4, and coil CL2 are arranged in an aligned orientation, but can also be arranged in a rotated manner. In other words, coil CL1 and coil CL2 only need to be arranged so that the magnetic flux penetrating coil CL1 passes through coil CL2, and the magnetic flux penetrating coil CL2 passes through coil CL1.

[0104] The pad Pd1 is connected to the bonding wire 14a. The pad Pd2 is connected to the bonding wire 14b. The semiconductor chip 11 is connected to the coil CL1 via the bonding wires 14a and 14b and the pads Pd1 and Pd2.

[0105] The pad Pd3 is connected to the bonding wire 24a via the through hole 32a and the frame 30a. The pad Pd4 is connected to the bonding wire 24b via the through hole 32b and the frame 30b. The semiconductor chip 21 is connected to the coil CL2 via the bonding wires 24a and 24b, the frames 30a and 30b, the through holes 32a and 32b, and the pads Pd3 and Pd4.

[0106] like Figure 7 as well as Figure 8 As shown, the wiring board 31 has a configuration in which insulating layers 61 , 62 , 63 , 64 , and 65 are sequentially stacked.

[0107] like Figure 7 As shown, the insulating layer 61 has an opening for connecting the pad Pd3 to the through hole 32a. The through hole 32a is provided in the opening of the insulating layer 61 and around the opening on the lower surface of the insulating layer 61. In addition, the through hole 32a is connected to the upper surface of the frame 30a. The through hole 32a is made of a conductive material. A bonding wire 24a is provided on the frame 30a.

[0108] An insulating layer 62 is provided on the insulating layer 61 and the through hole 32a. A pad Pd3 and wirings 51 and 52 (coil CL2) are provided in the insulating layer 62. In other words, the pad Pd3 and wirings 51 and 52 are provided on the same layer. The pad Pd3 is provided on the through hole 32a. In other words, the pad Pd3 is connected to the through hole 32a.

[0109] An insulating layer 63 is provided over the insulating layer 62 , the pad Pd3 , and the wirings 51 and 52 .

[0110] An insulating layer 64 is provided on the insulating layer 63. A pad Pd1 and wirings 41 and 42 (coil CL1) are provided in the insulating layer 64. In other words, the pad Pd1 and wirings 41 and 42 are provided in the same layer.

[0111] An insulating layer 65 is provided on the insulating layer 64 and the wirings 41 and 42. The insulating layer 65 has an opening for connecting the pad Pd1 and the bonding wire 14a. The pad Pd1 is provided under the opening of the insulating layer 65. The bonding wire 14a is provided on the pad Pd1.

[0112] like Figure 8 As shown, the insulating layer 61 has an opening for connecting the pad Pd4 to the through hole 32b. The through hole 32b is provided in the opening of the insulating layer 61 and around the opening on the lower surface of the insulating layer 61. In addition, the through hole 32b is connected to the upper surface of the frame 30b. The through hole 32b is made of a conductive material. A bonding wire 24b is provided on the frame 30b.

[0113] The insulating layer 62 is provided on the insulating layer 61 and the through hole 32b. The pad Pd4 is provided in the insulating layer 62. In other words, the pad Pd4 is provided in the same layer as the pad Pd3. The pad Pd4 is provided on the through hole 32b. In other words, the pad Pd4 is connected to the through hole 32b.

[0114] The pad Pd2 is provided in the insulating layer 64. In other words, the pad Pd2 is provided in the same layer as the pad Pd1.

[0115] The insulating layer 65 has an opening for connecting the pad Pd2 and the bonding wire 14b. The pad Pd2 is provided under the opening of the insulating layer 65. The bonding wire 14b is provided on the pad Pd2.

[0116] According to the isolator 1 of the present embodiment, the power efficiency of the transformer TR can be improved.

[0117] In a transformer including two coils each formed of a single-layer wiring wound in a spiral shape, as the number of turns of the coil increases, the single-layer wiring becomes longer, so the resistance of the single-layer wiring (winding resistance) increases in a quadratic curve. As a result, the Q value of the coil decreases. Due to the decrease in the Q value, the power efficiency of the transformer also decreases.

[0118] In contrast, in the present embodiment, the isolator 1 includes pads Pd1 and Pd2, a coil CL1, an insulating layer, pads Pd3 and Pd4, and a coil CL2. The coil CL1 includes wirings 41 and 42. The coil CL1 is connected to the pads Pd1 and Pd2. The coil CL2 includes wirings 51 and 52. The coil CL2 is arranged to be opposite to the coil CL1 via the insulating layer. The coil CL2 is connected to the pads Pd3 and Pd4.

[0119] Wiring 41 and 42 are connected in parallel between pads Pd1 and Pd2. In other words, coil CL1 has a double-layer wiring structure of wiring 41 and 42. Wiring 51 and 52 are connected in parallel between pads Pd3 and Pd4. In other words, coil CL2 has a double-layer wiring structure of wiring 51 and 52.

[0120] As a result, compared with the case where the wirings 41 and 42 are connected in series between the pads Pd1 and Pd2, the combined resistance of the wirings 41 and 42 between the pads Pd1 and Pd2 becomes smaller. Compared with the case where the wirings 51 and 52 are connected in series between the pads Pd3 and Pd4, the combined resistance of the wirings 51 and 52 between the pads Pd3 and Pd4 becomes smaller.

[0121] Therefore, the Q value of coil CL1 is larger than that of coil CL1 formed by a single-layer wiring. The Q value of coil CL2 is larger than that of coil CL2 formed by a single-layer wiring. Thus, according to this embodiment, the power efficiency of transformer TR can be improved.

[0122] In addition, in the present embodiment, the sum of the length of the wiring 41 and the length of the wiring 42 is shorter than the length of the wiring when the coil CL1 is formed by a single-layer wiring. In other words, the total number of turns of the wiring 41 and 42 contained in the coil CL1 is less than the number of turns of the wiring when the coil CL1 is formed by a single-layer wiring. The sum of the length of the wiring 51 and the length of the wiring 52 is shorter than the length of the wiring when the coil CL2 is formed by a single-layer wiring. In other words, the total number of turns of the wiring 51 and 52 contained in the coil CL2 is less than the number of turns of the wiring when the coil CL2 is formed by a single-layer wiring. As a result, the self-inductance of the coil CL1 is reduced compared to the case where the coil CL1 is formed by a single-layer wiring. The self-inductance of the coil CL2 is reduced compared to the case where the coil CL2 is formed by a single-layer wiring.

[0123] According to the above formula (2), the smaller the self-inductance L1 and L2, the smaller the coupling coefficient k. However, the increase in the Q value based on the double-layer wiring structure of the wirings 41 and 42 and the double-layer wiring structure of the wirings 51 and 52 is greater than the decrease in the coupling coefficient k. Therefore, according to this embodiment, the power efficiency of the transformer TR can be improved.

[0124] In addition, the smaller the self-inductance of coil CL1, the larger the resonant frequency of coil CL1. The smaller the self-inductance of coil CL2, the larger the resonant frequency of coil CL2. Therefore, according to the present embodiment, compared with the case where coil CL1 is formed by a single-layer wiring, the resonant frequency of coil CL1 becomes larger. Compared with the case where coil CL2 is formed by a single-layer wiring, the resonant frequency of coil CL2 becomes larger. That is, according to the present embodiment, the frequency band of transformer TR can be expanded. In addition, for example, if the operating frequency of transformer TR is set to 600 [MHz], the resonant frequency of coils CL1 and CL2 is preferably 3 times of 600 [MHz], that is, 1800 [MHz] or more.

[0125] Furthermore, in the present embodiment, the electrical length of the wiring 42 is equal to the electrical length of the wiring 41. The electrical length of the wiring 52 is equal to the electrical length of the wiring 51. Thus, the phase shift between the current flowing through the wiring 41 and the current flowing through the wiring 42 can be suppressed. The phase shift between the current flowing through the wiring 51 and the current flowing through the wiring 52 can be suppressed.

[0126] Therefore, compared with the case where the electrical length of the wiring 42 is different from the electrical length of the wiring 41, the generation of magnetic flux cancellation can be suppressed. Compared with the case where the electrical length of the wiring 52 is different from the electrical length of the wiring 51, the generation of magnetic flux cancellation can be suppressed. As a result, the reduction in the coupling coefficient k can be suppressed. Therefore, according to this embodiment, the power efficiency of the transformer TR can be improved. The longer the lengths of the wirings 41 and 42 and the wirings 51 and 52 are, the greater the cancellation area of ​​the magnetic flux is. Therefore, the lower the operating frequency of the transformer TR is, the more significantly the effect of improving the power efficiency of the transformer TR will be presented.

[0127] In addition, in the present embodiment, pads Pd1 and Pd2 have a substantially L-shaped shape. Pads Pd3 and Pd4 have a substantially L-shaped shape. Thus, the electrical length of wiring 42 can be adjusted to be equal to the electrical length of wiring 41. The electrical length of wiring 52 can be adjusted to be equal to the electrical length of wiring 51.

[0128] 2. Second Implementation

[0129] The isolator of the second embodiment will be described. In the isolator 1A of the second embodiment, the structure of the wiring board 31A is different from that of the first embodiment. In the following description, the parts different from the first embodiment will be mainly described.

[0130] 2.1 Structure of wiring board

[0131] use Figures 9 to 14 The structure of wiring board 31A will be described.

[0132] Fig. 9 FIG. 1 is a top view showing an example of the planar layout of the primary circuit FCA in the wiring board 31A. Fig. 9 As shown, the wiring board 31A includes pads Pd1A, Pd2A, and Pd5, a coil CL1A, through holes 43 and 44, and wiring 45. Fig. 9 In the figure, illustration of the secondary circuit SCA and the insulating layer in the wiring board 31A is omitted.

[0133] The pad Pd5 is a member that connects the wiring 41A and the pad Pd2A via the through holes 43 and 44 and the wiring 45. The pads Pd1A, Pd2A, and Pd5 have, for example, a substantially rectangular shape in a plan view. The pad Pd5 is made of a conductive material.

[0134] The first end E1 of the wiring 41A is connected to the pad Pd1A. The second end E2 of the wiring 41A is connected to the pad Pd5. In addition, the second end E2 is connected to the pad Pd2A via the pad Pd5, the through hole 44, the wiring 45, and the through hole 43. The wiring 41A has a swirl shape that rotates clockwise from the first end E1 and faces outward when viewed from above.

[0135] The third end E3 of the wiring 42A is connected to the pad Pd1A. The fourth end E4 of the wiring 42A is connected to the pad Pd2A. The wiring 42A is separated from the wiring 41A, for example, and has a spiral shape that rotates clockwise from the third end E3 and faces outward in a plan view.

[0136] The through hole 43 is provided below the pad Pd2A. In other words, the through hole 43 is in contact with the pad Pd2A. The through hole 44 is provided below the pad Pd5. In other words, the through hole 44 is in contact with the pad Pd5. The through holes 43 and 44 are made of a conductive material.

[0137] The wiring 45 is a member that connects the through-hole 43 and the through-hole 44. The wiring 45 is provided below the through-holes 43 and 44. In other words, the wiring 45 is in contact with the through-holes 43 and 44. The wiring 45 is made of a conductive material.

[0138] According to the above structure, the coil CL1A is connected to the pads Pd1A and Pd2A. More specifically, in the present embodiment, the wirings 41A and 42A are connected in parallel to each other between the pads Pd1A and Pd2A.

[0139] In the present embodiment, the thickness of the wiring 41A is made thinner than the thickness of the wiring 42A, and the resistance of the wiring 41A is designed to be larger than the resistance of the wiring 42A.

[0140] Furthermore, in the present embodiment, the electrical length of the wiring 42A is designed to be equal to the sum of a length N times the wavelength of the current flowing through the wirings 41A and 42A (N is an integer greater than or equal to 1) and the electrical length of the wiring 41A. That is, the relationship between the electrical length of the wiring 42A and the electrical length of the wiring 41A is expressed by the following formula (4). Hereinafter, the length N times the wavelength of the current flowing through the wirings 41A and 42A is also expressed as "N times the wavelength".

[0141] The electrical length of the wiring 42A =

[0142] N times the wavelength + the electrical length of the wiring 41A (N = 1, 2, 3, ...) (4)

[0143] In the present embodiment, the wiring 42A and the wiring 45 are arranged to be separated from each other and to intersect each other vertically.

[0144] Fig.10 31A is a top view showing an example of the planar layout of the secondary circuit SCA in the wiring board 31A. Fig.10 As shown, the wiring board 31A includes pads Pd3A, Pd4A and Pd6, a coil CL2A, through holes 53 and 54, and wiring 55. Fig.10In the figure, illustration of the primary circuit FCA and the insulating layer in the wiring board 31A is omitted.

[0145] The configuration of the secondary circuit SCA is the same as that of the primary circuit FCA. Specifically, it is as follows.

[0146] The pad Pd6 is a member that connects the wiring 51A and the pad Pd4A via the through holes 53 and 54 and the wiring 55. The pads Pd3A, Pd4A, and Pd6 have, for example, a substantially rectangular shape in a plan view. The pad Pd6 is made of a conductive material.

[0147] The fifth end E5 of the wiring 51A is connected to the pad Pd3A. The sixth end E6 of the wiring 51A is connected to the pad Pd6. In addition, the sixth end E6 is connected to the pad Pd4A via the pad Pd6, the through hole 54, the wiring 55, and the through hole 53. The wiring 51A has, for example, a swirl shape that rotates clockwise from the fifth end E5 and toward the outside when viewed from above.

[0148] The seventh end E7 of the wiring 52A is connected to the pad Pd3A. The eighth end E8 of the wiring 52A is connected to the pad Pd4A. The wiring 52A is separated from the wiring 51A, for example, and has a spiral shape that rotates clockwise from the seventh end E7 and faces outward in a plan view.

[0149] The through hole 53 is provided on the pad Pd4A. In other words, the through hole 53 is connected to the pad Pd4A. The through hole 54 is provided on the pad Pd6. In other words, the through hole 54 is connected to the pad Pd6. The through holes 53 and 54 are made of a conductive material.

[0150] The wiring 55 is a member that connects the through-hole 53 and the through-hole 54. The wiring 55 is provided on the through-holes 53 and 54. In other words, the wiring 55 is in contact with the through-holes 53 and 54. The wiring 55 is made of a conductive material.

[0151] According to the above structure, the coil CL2A is connected to the pads Pd3A and Pd4A. More specifically, in the present embodiment, the wirings 51A and 52A are connected in parallel to each other between the pads Pd3A and Pd4A.

[0152] In the present embodiment, the thickness of the wiring 51A is made thinner than the thickness of the wiring 52A, and the wiring 51A is designed to have a larger resistance than the wiring 52A.

[0153] Furthermore, in the present embodiment, the electrical length of the wiring 52A is designed to be equal to the sum of a length N times the wavelength of the current flowing through the wirings 51A and 52A (N is an integer greater than 1) and the electrical length of the wiring 51A. Hereinafter, the length N times the wavelength of the current flowing through the wirings 51A and 52A is also expressed as "N times the wavelength".

[0154] In addition, in the present embodiment, the wiring 52A and the wiring 55 are arranged to be separated from each other and to intersect each other vertically.

[0155] Fig.11 It is a perspective view showing an example of the structure of wiring board 31A. Fig.12 An example of a cross-sectional structure of the wiring board 31A is shown along Fig.11 Cross-sectional view of the S4-S4 line. Fig.13 An example of a cross-sectional structure of the wiring board 31A is shown along Fig.11 Cross-sectional view of line S5-S5. Fig.14 An example of a cross-sectional structure of the wiring board 31A is shown along Fig.11 Cross-sectional view of line S6-S6.

[0156] like Figure 11 to Figure 14 As shown, the wiring board 31A includes pads Pd1A, Pd2A and Pd5, a coil CL1A, through holes 43 and 44, a wiring 45, pads Pd3A, Pd4A and Pd6, a coil CL2A, through holes 53 and 54, a wiring 55, and insulating layers 71 to 79. Figure 11 to Figure 13 Also shown are the bonding wires 14a, 14b, 24a and 24b, the frames 30a and 30b, and the through holes 32a and 32b. Fig.11 In the figure, the through holes 43 and 44, the wiring 45, the through holes 53 and 54, the wiring 55, the through holes 32a and 32b, and the insulating layers 71 to 79 are omitted from illustration.

[0157] like Fig.11 As shown, coil CL1A is arranged above coil CL2A in the Z direction. That is, coil CL1A is arranged at a position overlapping with coil CL2A in the Z direction. In other words, coil CL2A is arranged to face coil CL1A via insulating layers 73 to 77. Fig.11 In the example, the pads Pd1A, Pd2A and Pd5, and the coil CL1A, the pads Pd3A, Pd4A and Pd6, and the coil CL2A are arranged in an aligned direction, but they can also be arranged in a rotated manner. In other words, the coil CL1A and the coil CL2A only need to be arranged so that the magnetic flux penetrating the coil CL1A penetrates the coil CL2A, and the magnetic flux penetrating the coil CL2A penetrates the coil CL1A.

[0158] The pad Pd1A is connected to the bonding wire 14a. The pad Pd2A is connected to the bonding wire 14b. The semiconductor chip 11 is connected to the coil CL1A via the bonding wires 14a and 14b, the pads Pd1A and Pd2A, the via 43, the wiring 45, the via 44, and the pad Pd5.

[0159] The pad Pd3A is connected to the bonding wire 24a via the through hole 32a and the frame 30a. The pad Pd4A is connected to the bonding wire 24b via the through hole 32b and the frame 30b. The semiconductor chip 21 is connected to the coil CL2A via the bonding wires 24a and 24b, the frames 30a and 30b, the through holes 32a and 32b, the pads Pd3A and Pd4A, the through hole 53, the wiring 55, the through hole 54, and the pad Pd6.

[0160] like Figure 12 to Figure 14 As shown, the wiring board 31A has a configuration in which insulating layers 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , and 79 are stacked in this order.

[0161] like Fig.12 As shown, the insulating layer 71 has an opening for connecting the pad Pd3A to the through hole 32a. The through hole 32a is provided in the opening of the insulating layer 71 and around the opening on the lower surface of the insulating layer 71.

[0162] An insulating layer 72 is provided on the insulating layer 71 and the through hole 32a. A pad Pd3A, and wirings 51A and 52A (coil CL2A) are provided in the insulating layer 72. In other words, the pad Pd3A, and wirings 51A and 52A are provided on the same layer. The pad Pd3A is provided on the through hole 32a. In other words, the pad Pd3A is connected to the through hole 32a.

[0163] An insulating layer 73 is provided over the insulating layer 72, the pad Pd3A, and the wirings 51A and 52A. An insulating layer 74 is provided over the insulating layer 73. An insulating layer 75 is provided over the insulating layer 74. An insulating layer 76 is provided over the insulating layer 75. An insulating layer 77 is provided over the insulating layer 76.

[0164] An insulating layer 78 is provided on the insulating layer 77. The pad Pd1A and the wirings 41A and 42A (coil CL1A) are provided in the insulating layer 78. In other words, the pad Pd1A and the wirings 41A and 42A are provided in the same layer.

[0165] An insulating layer 79 is provided on the insulating layer 78 and the wirings 41A and 42A. The insulating layer 79 has an opening for connecting the pad Pd1A and the bonding wire 14a. The pad Pd1A is provided under the opening of the insulating layer 79.

[0166] like Fig.13 As shown, the insulating layer 71 has an opening for connecting the pad Pd4A to the through hole 32b. The through hole 32b is provided in the opening of the insulating layer 71 and around the opening on the lower surface of the insulating layer 71.

[0167] An insulating layer 72 is provided on the insulating layer 71 and the through hole 32b. A pad Pd4A is provided in the insulating layer 72. In other words, the pad Pd4A and the pad Pd3A are provided in the same layer. The pad Pd4A is provided on the through hole 32b. In other words, the pad Pd4A is in contact with the through hole 32b.

[0168] The pad Pd2A is provided in the insulating layer 78. In other words, the pad Pd2A is provided in the same layer as the pad Pd1A.

[0169] The insulating layer 79 has an opening for connecting the pad Pd2A and the bonding wire 14 b . The pad Pd2A is provided under the opening of the insulating layer 79 .

[0170] like Fig.14 As shown in FIG. 1 , the insulating layer 71 has an opening for exposing the pad Pd6. The pad Pd6 is provided in the insulating layer 72. In other words, the pad Pd6 is provided in the same layer as the pads Pd3A and Pd4A. The pad Pd6 is provided on the opening of the insulating layer 71.

[0171] Through holes 53 and 54 are provided in the insulating layer 73. The through hole 53 is provided on the pad Pd4A. The through hole 54 is provided on the pad Pd6.

[0172] The wiring 55 is provided in the insulating layer 74. The wiring 55 is provided on the through holes 53 and 54.

[0173] The insulating layer 79 has an opening for exposing the pad Pd5. The pad Pd5 is provided in the insulating layer 78. In other words, the pad Pd5 is provided in the same layer as the pads Pd1A and Pd2A. The pad Pd5 is provided under the opening of the insulating layer 79.

[0174] Through holes 43 and 44 are provided in the insulating layer 77. The through hole 43 is provided below the pad Pd2A. The through hole 44 is provided below the pad Pd5.

[0175] The wiring 45 is provided in the insulating layer 76. The wiring 45 is provided under the through holes 43 and 44.

[0176] According to the isolator 1A of the present embodiment, the power efficiency of the transformer TRA can be improved.

[0177] In this embodiment, wiring 41A and 42A are connected in parallel to each other between pad Pd1A and pad Pd2A. In other words, coil CL1A has a double-layer wiring structure of wiring 41A and 42A. Wiring 51A and 52A are connected in parallel to each other between pad Pd3A and pad Pd4A. In other words, coil CL2A has a double-layer wiring structure of wiring 51A and 52A.

[0178] Thus, compared with the case where the wirings 41A and 42A are connected in series between the pads Pd1A and Pd2A, the combined resistance of the wirings 41A and 42A between the pads Pd1A and Pd2A becomes smaller. Compared with the case where the wirings 51A and 52A are connected in series between the pads Pd3A and Pd4A, the combined resistance of the wirings 51A and 52A between the pads Pd3A and Pd4A becomes smaller.

[0179] Therefore, the Q value of the coil CL1A is larger than that of the coil CL1A formed by a single-layer wiring. The Q value of the coil CL2A is larger than that of the coil CL2A formed by a single-layer wiring. Thus, according to this embodiment, the power efficiency of the transformer TRA can be improved.

[0180] In addition, in the present embodiment, the thickness of the wiring 41A is thinner than the thickness of the wiring 42A, and the resistance of the wiring 41A is greater than the resistance of the wiring 42A. The thickness of the wiring 51A is thinner than the thickness of the wiring 52A, and the resistance of the wiring 51A is greater than the resistance of the wiring 52A. As a result, compared with the case where the resistance of the wiring 41A is the same as the resistance of the wiring 42A, the combined resistance of the wirings 41A and 42A between the pads Pd1A and Pd2A becomes smaller. Compared with the case where the resistance of the wiring 51A is the same as the resistance of the wiring 52A, the combined resistance of the wirings 51A and 52A between the pads Pd3A and Pd4A becomes smaller.

[0181] Therefore, compared with the case where the resistance of wiring 41A is the same as the resistance of wiring 42A, the Q value of coil CL1A becomes larger. Compared with the case where the resistance of wiring 51A is the same as the resistance of wiring 52A, the Q value of coil CL2A becomes larger. Therefore, according to this embodiment, the power efficiency of transformer TRA can be improved.

[0182] Furthermore, in the present embodiment, the electrical length of the wiring 42A is equal to the sum of the electrical length of the wiring 41A and the N-times wavelength (N is an integer greater than or equal to 1). The electrical length of the wiring 52A is equal to the sum of the electrical length of the wiring 51A and the N-times wavelength (N is an integer greater than or equal to 1). Thus, the phase shift between the current flowing through the wiring 41A and the current flowing through the wiring 42A can be suppressed. The phase shift between the current flowing through the wiring 51A and the current flowing through the wiring 52A can be suppressed.

[0183] Therefore, compared with the case where the electrical length of the wiring 42A is different from the sum of the electrical length of the wiring 41A and the N times wavelength (N is an integer greater than 1), the generation of magnetic flux cancellation can be suppressed. Compared with the case where the electrical length of the wiring 52A is different from the sum of the electrical length of the wiring 51A and the N times wavelength (N is an integer greater than 1), the generation of magnetic flux cancellation can be suppressed. Thus, the reduction of the coupling coefficient k can be suppressed. Therefore, according to this embodiment, the power efficiency of the transformer TRA can be improved.

[0184] In addition, in the present embodiment, the wiring 42A and the wiring 45 are separated from each other and cross each other vertically. The wiring 52A and the wiring 55 are separated from each other and cross each other vertically. As a result, the direction of the current flowing through the wiring 42A deviates from the direction of the current flowing through the wirings 45 and 41A by 90 degrees. The direction of the current flowing through the wiring 52A deviates from the direction of the current flowing through the wirings 55 and 51A by 90 degrees. Therefore, the direction of the magnetic flux generated by the current flowing through the wiring 42A deviates from the direction of the magnetic flux generated by the current flowing through the wirings 45 and 41A by 90 degrees. The direction of the magnetic flux generated by the current flowing through the wiring 52A deviates from the direction of the magnetic flux generated by the current flowing through the wirings 55 and 51A by 90 degrees.

[0185] Therefore, it is possible to suppress the cancellation of the magnetic flux generated by the current flowing through the wiring 42A and the magnetic flux generated by the current flowing through the wiring 45 and 41A. It is possible to suppress the cancellation of the magnetic flux generated by the current flowing through the wiring 52A and the magnetic flux generated by the current flowing through the wiring 55 and 51A. Thus, it is possible to suppress the reduction of the coupling coefficient k. Therefore, according to this embodiment, the power efficiency of the transformer TRA can be improved.

[0186] 3. Modifications, etc.

[0187] As described above, the isolator (1 / 1A) of the embodiment includes a first pad (Pd1 / Pd1A), a second pad (Pd2 / Pd2A), a first coil (CL1 / CL1A), an insulating layer (63 / 73-77), a third pad (Pd3 / Pd3A), a fourth pad (Pd4 / Pd4A), and a second coil (CL2 / CL2A).

[0188] The first coil (CL1 / CL1A) includes a first wiring (41 / 41A) and a second wiring (42 / 42A). The first coil (CL1 / CL1A) is connected to a first pad (Pd1 / Pd1A) and a second pad (Pd2 / Pd2A). The second coil (CL2 / CL2A) includes a third wiring (51 / 51A) and a fourth wiring (52 / 52A). The second coil (CL2 / CL2A) is arranged to be opposite to the first coil (CL1 / CL1A) via an insulating layer (63 / 73-77). The second coil (CL2 / CL2A) is connected to a third pad (Pd3 / Pd3A) and a fourth pad (Pd4 / Pd4A). The first wiring (41 / 41A) and the second wiring (42 / 42A) are connected in parallel to each other between the first pad (Pd1 / Pd1A) and the second pad (Pd2 / Pd2A). The third wiring (51 / 51A) and the fourth wiring (52 / 52A) are connected in parallel to each other between the third pad (Pd3 / Pd3A) and the fourth pad (Pd4 / Pd4A).

[0189] In addition, the embodiment is not limited to the above-described embodiment, and various modifications are possible.

[0190] 3.1 Modification of the Second Embodiment

[0191] An isolator of a modified example of the second embodiment will be described. The isolator 1B of the modified example of the second embodiment is different from the second embodiment in that the structure of the wiring board 31B is different from that of the second embodiment and the through holes 32a and 32b and the frames 30a and 30b are eliminated. In the following description, the configuration different from the second embodiment will be mainly described.

[0192] 3.1.1 Isolator structure

[0193] use Figure 15 to Figure 17 The structure of the isolator 1B will be described. Fig.15 It is a plan view showing an example of the planar layout of the isolator 1B. Fig.16 An example of the cross-sectional structure of the isolator 1B is shown along Fig.15 Cross-sectional view of line S7-S7. Fig.17 An example of the cross-sectional structure of the isolator 1B is shown along Fig.15 Cross-sectional view of line S8-S8.

[0194] like Figure 15 to Figure 17 As shown, the isolator 1B includes die pads 10 and 20, semiconductor chips 11 and 21, leads 15 and 25, a transformer TRB, and an insulating member 100. Fig.15 In the figure, the insulating member 100 is omitted.

[0195] The die pads 10 and 20 and the leads 15 and 25 constitute a lead frame. Hereinafter, the die pads 10 and 20 and the leads 15 and 25 are collectively referred to as a "lead frame LFB."

[0196] like Fig.15 As shown, the wiring board 31B is disposed on the semiconductor chips 11 and 21. The die pads 10 and 20, the semiconductor chips 11 and 21, the bonding wires 14a, 14b, 16, 24a, 24b and 26, and the wiring board 31B are sealed by the insulating member 100.

[0197] like Fig.16 As shown, one end of the lower surface of the wiring board 31B is provided above the semiconductor chip 11 . The other end of the lower surface of the wiring board 31B is provided above the semiconductor chip 21 .

[0198] like Fig.17 As shown, one end of the bonding wire 24a is provided on the semiconductor chip 21. The other end of the bonding wire 24a is provided on the wiring board 31B.

[0199] 3.1.2 Structure of wiring board

[0200] use Figure 18 to Figure 23 The structure of wiring board 31B will be described.

[0201] Fig.18 FIG. 1 is a top view showing an example of the planar layout of the primary circuit FCB in the wiring board 31B. Fig.18 As shown, the wiring board 31B includes pads Pd1A, Pd2A, Pd5, Pd7, and Pd8, a coil CL1A, through holes 43, 44, 46, and 47, and a wiring 45. Fig.18 In the figure, illustration of the secondary circuit SCB and the insulating layer in the wiring board 31B is omitted.

[0202] The pad Pd7 is a component that connects the coil CL2A to the bonding wire 24a. The pad Pd8 is a component that connects the coil CL2A to the bonding wire 24b. The pads Pd7 and Pd8 have, for example, a substantially rectangular shape when viewed from above. The pads Pd7 and Pd8 are made of a conductive material.

[0203] The through hole 46 is provided below the pad Pd7. In other words, the through hole 46 is in contact with the pad Pd7. The through hole 47 is provided below the pad Pd8. In other words, the through hole 47 is in contact with the pad Pd8. The through holes 46 and 47 are made of a conductive material.

[0204] Fig.19 31B is a top view showing an example of the planar layout of the secondary circuit SCB in the wiring board 31B. Fig.19As shown, the wiring board 31B includes pads Pd3A, Pd4A, Pd6, Pd9, and Pd10, a coil CL2A, through holes 46, 47, 53, 54, and 56, and a wiring 55. Fig.19 In the figure, illustration of the primary circuit FCB and the insulating layer in the wiring board 31B is omitted.

[0205] The pads Pd9 and Pd10 are components for connecting the pad Pd3A and the pad Pd7. The pad Pd9 is provided above the pad Pd3A. The pad Pd10 is provided above the pad Pd4A. The pads Pd9 and Pd10 have, for example, a substantially rectangular shape when viewed from above. The pads Pd9 and Pd10 are made of a conductive material.

[0206] The through hole 46 is provided on the pad Pd10. In other words, the through hole 46 is connected to the pad Pd10. The through hole 47 is provided on the pad Pd4A. In other words, the through hole 47 is connected to the pad Pd4A. The through hole 56 is provided on the pad Pd3A. The through hole 56 is provided under the pad Pd9. In other words, the through hole 56 is connected to the pads Pd3A and Pd9. The through hole 56 is made of a conductive material.

[0207] The structure of the pad Pd3A and the coil CL2A is similar to that shown in the second embodiment. Fig.10 The structure of the pad Pd4A is similar to Fig.10 In addition to this point Fig.10 same.

[0208] Fig. 20 It is a perspective view showing an example of the structure of wiring board 31B. Fig.21 An example of a cross-sectional structure of the wiring board 31B is shown along Fig. 20 Cross-sectional view of line S9-S9. Fig. 22 An example of a cross-sectional structure of the wiring board 31B is shown along Fig. 20 Cross-sectional view of the S10-S10 line. Fig.23 An example of a cross-sectional structure of the wiring board 31B is shown along Fig. 20 Cross-sectional view of line S11-S11.

[0209] like Figure 20 to Figure 23 As shown, the wiring board 31B includes pads Pd1A, Pd2A, Pd5, Pd7 and Pd8, a coil CL1A, through holes 43, 44, 46 and 47, wiring 45, pads Pd3A, Pd4A, Pd6, Pd9 and Pd10, a coil CL2A, through holes 53, 54 and 56, wiring 55, and insulating layers 71 to 79. Figure 20 to Figure 22 The bonding wires 14a, 14b, 24a and 24b are also shown. Fig. 20In the figure, the insulating layers 71 to 79 are omitted.

[0210] like Fig. 20 As shown, pad Pd7 is connected to bonding wire 24a, and pad Pd8 is connected to bonding wire 24b.

[0211] like Fig.21 As shown, a through hole 56 is provided in the insulating layer 73. The through hole 56 is provided on the pad Pd3A.

[0212] The pad Pd9 is provided in the insulating layer 74. The pad Pd9 is provided on the through hole 56.

[0213] like Fig. 22 As shown, a through hole 53 is provided in the insulating layer 73. The through hole 53 is provided on the pad Pd4A.

[0214] The wiring 55 is provided in the insulating layer 74 . The wiring 55 is provided on the through hole 53 .

[0215] A through hole 43 is provided in the insulating layer 77. The through hole 43 is provided below the pad Pd2A.

[0216] The wiring 45 is provided in the insulating layer 76. The wiring 45 is provided under the through hole 43.

[0217] like Fig.23 As shown, pad Pd10 is provided in insulating layer 74. In addition, pad Pd10 is electrically connected to pad Pd9. Through hole 46 penetrates insulating layers 75 to 77. Through hole 46 is provided above pad Pd10. Through hole 46 is provided below pad Pd7. In other words, through hole 46 is connected to pads Pd7 and Pd10. Through hole 47 penetrates insulating layers 73 to 77. Through hole 47 is provided above pad Pd4A. Through hole 47 is provided below pad Pd8. In other words, through hole 47 is connected to pads Pd4A and Pd8.

[0218] According to the isolator 1B of this modification, similarly to the second embodiment, the power efficiency of the transformer TRB can be improved.

[0219] 3.2 Modification of the First Embodiment

[0220] An isolator of a modified example of the first embodiment is described. The isolator 1C of the modified example of the first embodiment is different from the first embodiment in that the structure of the wiring board 31C is different from that of the first embodiment and the through holes 32a and 32b and the frames 30a and 30b are eliminated. In the following description, the configuration different from the first embodiment is mainly described.

[0221] 3.2.1 Isolator structure

[0222] The structure of the isolator 1C is similar to that shown in the second embodiment. Figure 15 to Figure 17 same.

[0223] 3.2.2 Wiring board structure

[0224] use Figure 24 to Figure 29 The structure of wiring board 31C will be described.

[0225] Fig.24 FIG. 31 is a top view showing an example of the planar layout of the primary circuit FCC in the wiring board 31C. Fig.24 As shown, the wiring board 31C includes pads Pd1, Pd2, Pd7, and Pd8, a coil CL1, and through holes 46 and 47. Fig.24 In the figure, illustration of the secondary circuit SCC and the insulating layer in the wiring board 31C is omitted.

[0226] The pad Pd7 is a component that connects the coil CL2 to the bonding wire 24a. The pad Pd8 is a component that connects the coil CL2 to the bonding wire 24b. The pads Pd7 and Pd8 have, for example, a substantially rectangular shape when viewed from above. The pads Pd7 and Pd8 are made of a conductive material.

[0227] The through hole 46 is provided below the pad Pd7. In other words, the through hole 46 is in contact with the pad Pd7. The through hole 47 is provided below the pad Pd8. In other words, the through hole 47 is in contact with the pad Pd8. The through holes 46 and 47 are made of a conductive material.

[0228] The structures of the pads Pd1, Pd2 and the coil CL1 are similar to those shown in the first embodiment. Figure 3 same.

[0229] Fig.25 31C is a top view showing an example of the planar layout of the secondary circuit SCC in the wiring board 31C. Fig.25 As shown, the wiring board 31C includes pads Pd3, Pd4, Pd9 and Pd10, a coil CL2, and through holes 46, 47 and 56. Fig.25 In the figure, illustration of the primary circuit FCC and the insulating layer in the wiring board 31C is omitted.

[0230] The pads Pd9 and Pd10 are components for connecting the pad Pd3 and the pad Pd7. The pad Pd9 is provided above the pad Pd3. The pad Pd10 is provided above the pad Pd4. The pads Pd9 and Pd10 have, for example, a substantially rectangular shape when viewed from above. The pads Pd9 and Pd10 are made of a conductive material.

[0231] The through hole 46 is provided on the pad Pd10. In other words, the through hole 46 is connected to the pad Pd10. The through hole 47 is provided on the pad Pd4. In other words, the through hole 47 is connected to the pad Pd4. The through hole 56 is provided on the pad Pd3. The through hole 56 is provided under the pad Pd9. In other words, the through hole 56 is connected to the pads Pd3 and Pd9. The through hole 56 is made of a conductive material.

[0232] The structure of the pad Pd3 and the coil CL2 is similar to that shown in the first embodiment. Figure 5 The structure of pad Pd4 is similar to Figure 5 In addition to this point Figure 5 same.

[0233] Fig.26 It is a perspective view showing an example of the structure of wiring board 31C. Fig. 27 An example of a cross-sectional structure of the wiring board 31C is shown along Fig.26 Cross-sectional view of the S12-S12 line.

[0234] Fig.28 An example of a cross-sectional structure of the wiring board 31C is shown along Fig.26 Cross-sectional view of line S13-S13. Fig.29 An example of a cross-sectional structure of the wiring board 31C is shown along Fig.26 Cross-sectional view of line S14-S14.

[0235] like Figure 26 to Figure 29 As shown, the wiring board 31C includes pads Pd1, Pd2, Pd7 and Pd8, a coil CL1, through holes 46 and 47, pads Pd3, Pd4, Pd9 and Pd10, a coil CL2, a through hole 56, and insulating layers 61 to 67. Figure 26 to Figure 28 The bonding wires 14a, 14b, 24a and 24b are also shown. Fig.26 In the figure, the insulating layers 61 to 67 are omitted.

[0236] like Fig.26 As shown, pad Pd7 is connected to bonding wire 24a, and pad Pd8 is connected to bonding wire 24b.

[0237] like Figure 27 to Figure 29 As shown in FIG. 1 , the wiring board 31C has a structure in which insulating layers 61, 62, 63, 66, 67, 64, and 65 are sequentially stacked. In other words, the wiring board 31C has the structure shown in the first embodiment. Figure 7 as well as Figure 8 The insulating layer 66 and the insulating layer 67 are provided between the insulating layer 63 and the insulating layer 64 .

[0238] like Fig. 27As shown, a through hole 56 is provided in the insulating layer 63. The through hole 56 is provided on the pad Pd3.

[0239] An insulating layer 66 is provided on the insulating layer 63. An insulating layer 67 is provided on the insulating layer 66. An insulating layer 64 is provided on the insulating layer 67.

[0240] The pad Pd9 is provided in the insulating layer 66. The pad Pd9 is provided on the through hole 56.

[0241] like Fig.28 As shown, pad Pd4 is larger in size than pad Pd2.

[0242] like Fig.29 As shown, a pad Pd10 is provided in the insulating layer 66. In addition, the pad Pd10 is electrically connected to the pad Pd9. A through hole 46 is provided in the insulating layer 67. The through hole 46 is provided above the pad Pd10. The through hole 46 is provided below the pad Pd7. In other words, the through hole 46 is connected to the pads Pd7 and Pd10. The through hole 47 penetrates the insulating layers 63, 66 and 67. The through hole 47 is provided above the pad Pd4. The through hole 47 is provided below the pad Pd8. In other words, the through hole 47 is connected to the pads Pd4 and Pd8.

[0243] According to the isolator 1C of this modification, similarly to the first embodiment, the power efficiency of the transformer TRC can be improved.

[0244] Furthermore, the above-described embodiment and modified examples can also be applied to isolators for two or more channels.

[0245] In this specification, "connected" means electrically connected, and does not exclude the case where another element is interposed therebetween, for example.

[0246] 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 embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are also included in the invention described in the claims and their equivalents.

[0247] Description of Reference Numerals

[0248] 1, 1A, 1B, 1C…isolator, 10, 20…die pad, 11, 21…semiconductor chip, 12, 22…circuit, 13, 23…bonding component, 14a, 14b, 16, 24a, 24b, 26…bonding wire, 15, 25…lead, 30a, 30b…frame, 31, 31A, 31B, 31C…wiring board, 32a, 32b, 43, 44, 46, 47, 53, 54, 56…through hole, 41, 42, 45, 51, 52, 55…wiring, 61-67, 71-79…insulating layer, 100…insulating component, LF, LFB…lead frame, TR, TRA, TRB, TRC…transformer, CL1, CL1A, CL2, CL2A…coil, Pd1, Pd1A, Pd2, Pd2A, Pd3, Pd3A, Pd4, Pd4A, Pd5, Pd6, Pd7, Pd8, Pd9, Pd10…pad.

Claims

1. An isolator, characterized in that: have: A first pad; Second pad; A first coil includes a first wiring and a second wiring, and is connected to the first pad and the second pad; Insulation layer; The third pad; a fourth pad; as well as The second coil includes a third wiring and a fourth wiring, is arranged to face the first coil via the insulating layer, and is connected to the third pad and the fourth pad. The first wiring and the second wiring are connected in parallel between the first pad and the second pad. The third wiring and the fourth wiring are connected in parallel to each other between the third pad and the fourth pad.

2. The isolator according to claim 1, characterized in that The electrical length of the second wiring is equal to the electrical length of the first wiring, The electrical length of the fourth wiring is equal to the electrical length of the third wiring.

3. The isolator according to claim 2, characterized in that The first pad includes a first base and a first protrusion protruding from the first base in a first direction. The second pad includes a second base portion and a second protrusion portion protruding from the second base portion in a second direction intersecting the first direction. The first wiring has a first end connected to the first base portion of the first pad and a second end connected to the second base portion of the second pad. The second wiring has a third end connected to the first protrusion of the first pad and a fourth end connected to the second protrusion of the second pad. The third pad includes a third base portion and a third protrusion portion protruding from the third base portion toward the first direction. The fourth pad includes a fourth base portion and a fourth protrusion portion protruding from the fourth base portion toward the second direction. The third wiring has a fifth end connected to the third base portion of the third pad and a sixth end connected to the fourth base portion of the fourth pad. The fourth wiring has a seventh end connected to the third protruding portion of the third pad and an eighth end connected to the fourth protruding portion of the fourth pad.

4. The isolator according to claim 3, characterized in that: The first wiring has a spiral shape extending from the first end toward the first rotation direction and toward the outside in a plan view, The second wiring is separated from the first wiring and has a spiral shape extending from the third end toward the first rotation direction and toward the outside in a plan view. The third wiring has a spiral shape extending from the fifth end toward the first rotation direction and toward the outside in a plan view, The fourth wiring is separated from the third wiring and has a spiral shape extending from the seventh end toward the first rotation direction and toward the outside in a plan view.

5. The isolator according to claim 4, characterized in that: The swirl shape of the first wiring, the swirl shape of the second wiring, the swirl shape of the third wiring, and the swirl shape of the fourth wiring are ellipses, respectively.

6. The isolator according to claim 4, characterized in that an outer diameter of the first coil in the second direction is longer than an outer diameter of the first coil in the first direction, An outer diameter of the second coil in the second direction is longer than an outer diameter of the second coil in the first direction.

7. The isolator according to claim 4, characterized in that In the second direction, the total number of turns of the first wiring and the second wiring on the second pad side of the first pad is less than the total number of turns of the first wiring and the second wiring on the side of the first pad opposite to the second pad, In the second direction, the total number of turns of the third wiring and the fourth wiring on the fourth pad side of the third pad is smaller than the total number of turns of the third wiring and the fourth wiring on the side of the third pad opposite to the fourth pad.

8. The isolator according to claim 1, characterized in that The electrical length of the second wiring is equal to the sum of the length of N times the wavelength of the current flowing through the first wiring and the second wiring and the electrical length of the first wiring, where N is an integer greater than 1. The electrical length of the fourth wiring is equal to the sum of a length N times the wavelength of a current flowing through the third wiring and the fourth wiring and the electrical length of the third wiring, where N is an integer greater than or equal to 1.

9. The isolator according to claim 8, characterized in that Also available: fifth pad; fifth wiring; a sixth pad; and The sixth wiring, The first wiring has a first end connected to the first pad and a second end connected to the second pad. The second wiring has a third end connected to the first pad and a fourth end connected to the second pad. The second end of the first wiring is connected to the second pad via the fifth pad and the fifth wiring. The second wiring and the fifth wiring are separated from each other and vertically intersect each other. The third wiring has a fifth end connected to the third pad and a sixth end connected to the fourth pad. The fourth wiring has a seventh end connected to the third pad and an eighth end connected to the fourth pad, The sixth end of the third wiring is connected to the fourth pad via the sixth pad and the sixth wiring. The fourth wiring and the sixth wiring are separated from each other and vertically intersect each other.

10. The isolator according to claim 9, characterized in that The first wiring has a spiral shape extending from the first end toward the first rotation direction and toward the outside in a plan view, The second wiring is separated from the first wiring and has a spiral shape extending from the third end toward the first rotation direction and toward the outside in a plan view. The third wiring has a spiral shape extending from the fifth end toward the first rotation direction and toward the outside in a plan view, The fourth wiring is separated from the third wiring and has a spiral shape extending from the seventh end toward the first rotation direction and toward the outside in a plan view.

11. The isolator according to claim 10, characterized in that The swirl shape of the first wiring, the swirl shape of the second wiring, the swirl shape of the third wiring, and the swirl shape of the fourth wiring are ellipses, respectively.

12. The isolator according to claim 8, characterized in that The thickness of the first wiring is thinner than the thickness of the second wiring, The thickness of the third wiring is thinner than the thickness of the fourth wiring.

13. The isolator according to claim 1, characterized in that The second wiring is provided in the same layer as the first wiring, The fourth wiring is provided in the same layer as the third wiring.

14. The isolator according to claim 13, characterized in that The first pad is provided on the same layer as the first wiring and the second wiring, The third pad is provided on the same layer as the third wiring and the fourth wiring.

15. The isolator according to claim 14, characterized in that The second pad is provided on the same layer as the first pad, The fourth pad is provided on the same layer as the third pad.

16. The isolator according to claim 1, characterized in that Also available: A first semiconductor chip is connected to the first coil via the first pad and the second pad; and The second semiconductor chip is connected to the second coil via the third pad and the fourth pad.

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