WO2022216700A1

WO2022216700A1 - Integrated isolated dc-dc convertor module

Info

Publication number: WO2022216700A1
Application number: PCT/US2022/023471
Authority: WO
Inventors: Takayuki TANGE
Original assignee: Murata Manufacturing Co., Ltd.; Murata Power Solutions
Priority date: 2021-04-09
Filing date: 2022-04-05
Publication date: 2022-10-13

Abstract

A module includes a first substrate with a first primary conductor path and a first secondary conductor path, a second substrate with a second primary conductor path and a second secondary conductor path, and a magnetic core between the first substrate and the second substrate. The first substrate faces the second substrate. The first primary conductor path is electrically connected to the second primary conductor path by a first conductive pillar provided between the first substrate and the second substrate. The first secondary conductor path is electrically connected to the second secondary conductor path by a second conductive pillar provided between the first substrate and the second substrate. An electrical component is located between the first substrate and the second substrate. The module includes an encapsulant that encapsulates the magnetic core, the first conductive pillar, the second conductive pillar, and the electrical component.

Description

INTEGRATED ISOLATED DC-DC CONVERTOR MODULE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to electrical converters. More specifically, the present invention relates to modules that include an isolated DC-DC converter.

2. Description of the Related Art

[0002] Known DC-DC converters that provide isolation that meet UL compliance have included embedded magnetic cores. For example, Figs. 1 and 3 show known modules 100 and 200 with embedded cores 130 and 230, and Fig. 2 shows a known embedded core 150. However, such known modules are relatively large in size, and it is desirable to reduce the footprint of modules that are mounted to a substrate on which other surface-mounted components are provided.

[0003] The module 100 shown in Fig. 1 includes a protective layer 140, which is typically solder resist. However, a solder resist layer cannot be used as a solid insulator for UL compliance. Accordingly, the module 100 shown in Fig. 1 may require additional reinforced isolation to prevent electrical shocks, which would increase the size of the module 100.

[0004] As shown in Fig. 2, to ensure UL compliance, the traces of the primary winding 160 and the secondary winding 170 are required to be spaced a predetermined distance apart. The embedded core 150 in Fig. 2 includes bifilar windings around a magnetic core 180 such that a significant gap is required between the primary winding 160 and the secondary winding 170.

For example, to meet the reinforced isolation requirement of UL compliance, the gap between the primary winding 160 and the secondary winding 170 must be at least 0.4 mm. Accordingly, a module included in the embedded core 150 will have a relatively large size due to this gap requirement, and the transformer with the embedded core 150 may have poor transformer coupling.

[0005] As shown in Fig. 3, module 200 includes an embedded core 230. However, additional electrical components cannot be embedded with the core 230. SUMMARY OF THE INVENTION

[0006] To overcome the problems described above, preferred embodiments of the present invention provide modules with electrical converters with embedded electrical components, which can include surface-mounted electrical components, resulting in modules with significantly reduced sizes.

[0007] A module according to a preferred embodiment of the present invention includes at least one first substrate including a first primary conductor path and a first secondary conductor path, at least one second substrate including a second primary conductor path and a second secondary conductor path, and a magnetic core between the at least one first substrate and the at least one second substrate. The at least one first substrate faces the at least one second substrate. The first primary conductor path is electrically connected to the second primary conductor path by at least one first conductive pillar provided between the at least one first substrate and the at least one second substrate. The first secondary conductor path is electrically connected to the second secondary conductor path by at least one second conductive pillar provided between the at least one first substrate and the at least one second substrate. At least one electrical component is located between the at least one first substrate and the at least one second substrate. The module includes an encapsulant that encapsulates the magnetic core, the at least one first conductive pillar, the at least one second conductive pillar, and the at least one electrical component.

[0008] The at least one electrical component can include a circuit component electrically connected to the first primary conductor path or the second primary conductor path. The at least one electrical component can include a circuit component electrically connected to the first secondary conductor path or the second secondary conductor path. The at least one electrical component can include a surface-mounted electrical component that is mounted to a surface of the at least one first substrate or the at least one second substrate.

[0009] The magnetic core can have a toroidal shape with a center hole. The at least one first conductive pillar can include a first conductive pillar that passes through the center hole of the magnetic core and an additional first conductive pillar that does not pass through the center hole of the magnetic core. The at least one second conductive pillar can include a second conductive pillar that passes through the center hole of the magnetic core and an additional second conductive pillar that does not pass through the center hole of the magnetic core. [0010] The at least one first substrate can include at least two first substrate layers that separate the first primary conductor path from the first secondary conductor path. The at least two first substrate layers can be thin film insulators.

[0011] The at least one second substrate can include at least two second substrate layers that separate the second primary conductor path from the second secondary conductor path. The at least two second substrate layers can be thin film insulators.

[0012] An electrical input or output connection can be provided on a surface of the at least one second substrate that does not face the at least one first substrate.

[0013] The first primary conductor path, the second primary conductor path, and the at least one first conductive pillar can define a primary transformer winding. The first secondary conductor path, the second secondary conductor path, and the at least one second conductive pillar can define a secondary transformer winding. The primary transformer winding can at least partially surround the secondary transformer winding.

[0014] The first primary conductor path can be electrically connected to the at least one first conductive pillar by at least one first via provided in the at least one first substrate. The second primary conductor path can be electrically connected to the at least one second conductive pillar by at least one second via provided in the at least one second substrate.

[0015] The module can include a DC-DC converter. The at least one electrical component can be directly mounted to the at least one first substrate. The encapsulant can include an epoxy resin with a silica filler.

[0016] A module according to a preferred embodiment of the present invention includes a first substrate, a second substrate, and an encapsulant layer between the first and the second substrates. The encapsulant layer encapsulates each of first conductive pillars physically and electrically connecting the first and the second substrates, a first electrical component connected to the first substrate, and a magnetic core. A first winding of the module includes the first conductive pillars, electrically connected to the first electrical component, and extends around the magnetic core and through the first and the second substrates. [0017] The module can further include a second winding. The encapsulant layer can include second conductive pillars physically and electrical connecting the first and the second substrates, and the second winding can include the second conductive pillars and extends around the magnetic core and through the first and the second substrates.

[0018] When viewed in plan, at least a portion of the first electrical component can overlap with the magnetic core. The module can further include a second electrical component connected to the first substrate and a third electrical component connected to the second substrate. When viewed in plan, the second and the third electrical components can at least partially overlap with each other. The second winding can be electrically connected to the second and the third electrical components. A portion of the first winding can extend around a portion of the second winding in a multilayer arrangement.

[0019] The module can further include a second electrical component connected to an exterior surface of the module. The module can include a DC-DC converter. The encapsulant layer can include an epoxy resin with a silica filler.

[0020] A system according to a preferred embodiment of the present invention includes a mother substrate and one of the modules of the various other preferred embodiments of the present invention attached to the mother substrate.

[0021] A method of manufacturing a module according to a preferred embodiment of the present invention includes providing a first substrate with a first electronic component and first conductive pillars connected to the first substrate, providing a second substrate, connecting the first and the second substrates together with a magnetic core between the first and the second substrate such that the first conductive pillars physically and electrically connect the first and the second substrates, and applying an encapsulant to form an encapsulant layer between the first and the second substrates and to encapsulate the first electronic component, the first conductive pillars, and the magnetic core. The module includes a first winding that includes the first conductive pillars, that is electrically connected to the first electrical component, and that extends around the magnetic core and through the first and the second substrates.

[0022] The encapsulant layer can include second conductive pillars that physically and electrical connect the first and the second substrates, and the module can include a second winding that includes the second conductive pillars and that extends through the first and the second substrates and includes the first conductive pillars. When viewed in plan, at least a portion of the first electrical component can overlap with the magnetic core. A second electrical component can be connected to the first substrate, and a third electrical component can be connected to the second substrate. When viewed in plan, the second and the third electrical components can at least partially overlap with each other. The second winding can be electrically connected to the second and the third electrical components. A portion of the first winding can extend around a portion of the second winding in a multilayer arrangement.

[0023] The method can further include connecting a second electrical component to an exterior surface of the module. The module can include a DC-DC converter. The method can further include attaching the module to a mother substrate. The encapsulant can include an epoxy resin with a silica filler.

[0024] The above and other features, elements, steps, configurations, characteristics, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS [0025] Fig. 1 shows a known module with an embedded core.

[0026] Fig. 2 shows a known embedded core with bifilar windings.

[0027] Fig. 3 shows a known module with an embedded core.

[0028] Fig. 4 shows a multilayer winding arrangement of a transformer that can be used with a module according to a preferred embodiment of the present invention.

[0029] Figs. 5-11 show a process for manufacturing a module according to a preferred embodiment of the present invention.

[0030] Fig. 12 shows a modification to the module of Fig. 11.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0031] Preferred embodiments of the present invention will now be described with reference to Figs. 4-12. In the preferred embodiments of the present invention, modules with significantly reduced sizes can be provided. In addition, preferred embodiments of the present invention also provide modules with embedded electrical components, which can include surface-mounted electrical components. As described below, the isolation between the different components can be provided by encapsulating surface-mounted electrical components and conductive pillars and by separating the primary traces from the secondary traces by substrate layers.

[0032] Fig. 4 shows a multilayer winding arrangement of a transformer 15 that can be used with a module according to a preferred embodiment of the present invention. For clarity of illustration, substrate layers and encapsulating material are not shown in Fig. 4. In contrast to Figs. 1-3 in which portions of the primary and secondary windings are located on the same upper and lower layer, the primary and secondary windings of the transformer 15 in Fig. 4 include a multilayer arrangement in which portions of the primary and secondary windings are located on different upper layers and on different lower layers.

[0033] As shown in Fig. 4, the transformer 15 includes a magnetic core 30 surrounded by outer windings and inner windings. The outer windings include upper traces 12 and lower traces 22, which are physically and electrically connected by conductive pillars 32. The inner windings include upper traces 13 and lower traces 23, which are physically and electrically connected by conductive pillars 33. The conductive pillars 32 and 33 can be copper conductors or the like. The upper traces 12 of the outer windings can be located on a different layer above the upper traces 13 of the inner windings, and the lower traces 22 of the outer windings can be located on a different layer below the lower traces 23 of the inner windings. The outer winding can be the primary winding or can be the secondary winding, and the inner winding can be the secondary winding or can be the primary winding.

[0034] Figs. 5-11 show a process for manufacturing the module 1 according to a preferred embodiment of the present invention.

[0035] As shown in Fig. 5, an upper substrate 10 can be provided. The upper substrate 10 can be manufactured by, for example, a press PCB (print circuit board) stack-up process. As shown in Fig. 5, the upper substrate 10 can include multiple layers. The upper substrate 10 includes traces 12 and traces 13. Although the traces 13 are shown on the top of the upper substrate 10 in Fig. 5, it is possible that the traces 13 are included in an interior layer of the upper substrate 10, in which case the traces 13 can be connected to the top surface of the upper substrate 10 by vias. The traces 12 can be included in the primary winding or the secondary winding, and the traces 13 can be included in the secondary winding or the primary winding. The upper substrate 10 can include at least four total substrate layers, with two intermediate substrate layers 11 provided between the traces 12 and the traces 13. The two intermediate substrate layers 11 can define thin film insulators with predetermined dielectric strengths. Vias 14 can be provided in the intermediate substrate layers 11 to provide an electrical connection for the traces 12.

[0036] As shown in Fig. 6, electrical components 16 and 17 and conductive pillars 32 and 33 are provided on the upper substrate 10. The electrical components 16 and 17 and the conductive pillars 32 and 33 are physically and electrically connected to the upper substrate 10 by solder 19 or the like. As shown in Fig. 4, each end of the traces 12 can include two conductive pillars 32, although a different number of conductive pillars can be used. The electrical components 16 and 17 can be included in the primary-side circuits, i.e., the circuits connected to the primary winding of the transformer, and/or the secondary-side circuits, i.e., the circuit connected to the second winding of the transformer. The electrical components 16 and 17 can be any component used to implement a DC-DC converter. The electrical components 16 and 17 can be mounted to the upper substrate 10 by any suitable method, including surface mounting. The electrical components 16 and 17 can be active components, e.g., transistors, and/or can be passive components, e.g., resistors, capacitors, inductors, diodes, etc. The conductive pillars 32 provide an electrical connection for the traces 12, and the conductive pillars 33 provide an electrical connection for the traces 13. A clearance of at least 0.4 mm can be provided between the closest surfaces of the conductive pillars 32 and 33.

[0037] As shown in Fig. 7, a lower substrate 20 can be provided. The lower substrate 20 can also be manufactured by, for example, a press PCB stack-up process. The lower substrate 20 include traces 22 and traces 23. Although the traces 23 are shown on the top of the lower substrate 20 in Fig. 7, it is possible that the traces 23 can be included in an interior layer of the lower substrate 20, in which case the traces 23 can be connected to the top surface of the upper substrate 10 by vias. The traces 22 can be included in the primary winding or the secondary winding, and the traces 23 can be included in the secondary winding or the primary winding. The lower substrate 20 can include at least four total substrate layers, with two intermediate substrate layers 21 provided between the primary traces 22 and the secondary traces 23. The two intermediate substrate layers 21 can define thin film insulators with predetermined dielectric strengths. Vias 24 can be provided in the intermediate substrate layers 21 to provide an electrical connection for the primary traces 22. Input/output connections 28 can also be provided on at least one outer surface of the lower substrate 20. [0038] As shown in Fig. 8, electrical components 26 are provided on the lower substrate 20. The electrical components 26 are physically and electrically connected to the lower substrate 20 by solder or the like. The electrical components 26 can be included in the primary-side circuits and/or the secondary-side circuits. The electrical components 26 can be any component used to implement a DC-DC converter. The electrical components 26 can be mounted to the lower substrate 20 by any suitable method, including surface mounting. The electrical components 26 can be active components, e.g., transistors, and/or can be passive components, e.g., resistors, capacitors, inductors, diodes, etc.

[0039] As shown in Fig. 9, a magnetic core 30 is placed on the lower substrate 20, and solder 29 or the like is deposited on the lower substrate 20 to provide a physical and electrical connection to the conductive pillars 32 and 33. A height of the magnetic core 30 may be, for example, about 0.3 mm, within manufacturing tolerances.

[0040] As shown in Fig. 10, the upper substrate 10, including the electrical components 16 and 17 and conductive pillars 33 and 34, is mounted on the lower substrate 20. The electrical components 16 and the electrical components 26 can, collectively, define primary-side circuit components and/or secondary-side circuit components. As shown in Fig. 10, the conductive pillars 32 electrically connect the traces 12 of the upper substrate 10 to the traces 22 of the lower substrate 20 via the vias 14 in the upper substrate 10 and the vias 24 in the lower substate 20, and the conductive pillars 33 electrically connect the traces 13 of the upper substrate 10 to the traces 23 of the lower substrate 20. As an example, a distance between the closest surfaces of the upper substrate 10 and the lower substrate 20 may be at least about 0.5 mm, within manufacturing tolerances. Accordingly, an outer winding can include the traces 12 and 22, vias 14 and 24, and pillars 32, and an inner winding can include the traces 13 and 23 and pillars 33. As shown in Fig. 4, the inner and outer windings can be located on one side of the magnetic core 30. The magnetic core 30 can have a toroidal shape with a center hole. Some of the conductive pillars 32 and 33 can be included in the center hole of the magnetic core 30, and other of the conductive pillars 32 and 33 can be located on the exterior of the magnetic core 30.

[0041] As shown in Fig. 10, the electrical component 17 can be located above a portion of the magnetic core 30 such that, when viewed in plan, at least a portion of the electrical component 17 overlaps with the magnetic core 30. Additionally, the components 16 and 26 can be located such that, when view in plan, the electrical components 16 and 26 at least partially overlap with each other. This arrangement of the electrical components 16, 17, and 26 can help reduce the size of the module 1.

[0042] As shown in Fig. 11, the electrical components 16, 17, and 26 located between the upper substrate 10 and the lower substrate 20 can be included within an encapsulant 39, defining an encapsulant layer 50 between the upper substrate 10 and the lower substrate 20. The encapsulant 39 can be applied, for example, by injection molding a compound by transfer molding. The compound of the encapsulant 39 can be, for example, an epoxy resin with a silica filler. Accordingly, the module 1 is provided. The input/output connections 28 can connect the module 1 to other electrical components, for example, another substrate such as a PCB.

[0043] By encapsulating the electrical components 16, 17, and 26 with the conductive pillars 32 and 33 and the magnetic core 30, the module 1 can be provided with a compact size, while also meeting isolation requirements to ensure UL compliance.

[0044] As compared with the known converters 100 and 200 shown in Figs. 1 and 3, previously unused space around the windings can be utilized by the module 1. Accordingly, the module 1 can be provided with a significantly reduced size. In addition, the traces 12 and 22 can be separated from the traces 13 and 23 by only the intermediate substrate layers 11 and 21, which significantly reduces an overall size of the module 1. According to UL compliance requirements, two thin film insulators (i.e., the intermediate substrate layers 11 and 21) can be used to reduce the requirement of at least a 0.4-mm spacing of the primary and secondary windings. Furthermore, with the reduced size and close physical arrangement of the traces 12 and 22 and the traces 13 and 23, the module 1 provides a transformer with significantly improved coupling.

[0045] Fig. 12 shows one example of a modification 1A of the module 1 shown in Fig. 11. As shown in Fig. 12, electrical components 46 can be mounted on an exterior surface of the upper substrate 10. Additionally or alternatively, the module 1A can be mounted on a mother substrate 40 by the input/output connections 28, and the electrical components 47 can be mounted on the mother substrate 40 at a location that is adjacent to or in a vicinity of the module 1A, as shown in Fig. 12. The electrical components 46 and 47 can be included in the primary-side circuits and/or the secondary-side circuits. However, the electrical components 46 and 47 can also be components of other circuits. Locations of the electrical components 46 and 47 can be determined according to UL creepage and clearance requirements.

[0046] The modules 1 and 1A described above implement DC-DC converters, and electrical components 16, 17, and 26 can be any components that are used to implement DC-DC converters. However, the modules 1 and 1A and the electrical components 16, 17, and 26 can also be used to implement other circuitry, in particular, circuitry that includes a high isolation barrier.

[0047] It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A module comprising: at least one first substrate including a first primary conductor path and a first secondary conductor path; at least one second substrate including a second primary conductor path and a second secondary conductor path; and a magnetic core between the at least one first substrate and the at least one second substrate, wherein the at least one first substrate faces the at least one second substrate; the first primary conductor path is electrically connected to the second primary conductor path by at least one first conductive pillar provided between the at least one first substrate and the at least one second substrate; the first secondary conductor path is electrically connected to the second secondary conductor path by at least one second conductive pillar provided between the at least one first substrate and the at least one second substrate; at least one electrical component is located between the at least one first substrate and the at least one second substrate; and the module includes an encapsulant that encapsulates the magnetic core, the at least one first conductive pillar, the at least one second conductive pillar, and the at least one electrical component.

2. The module according to claim 1, wherein the at least one electrical component includes a circuit component electrically connected to the first primary conductor path or the second primary conductor path.

3. The module according to claim 1, wherein the at least one electrical component includes a circuit component electrically connected to the first secondary conductor path or the second secondary conductor path.

4. The module according to claim 1, wherein the at least one electrical component includes a surface-mounted electrical component that is mounted to a surface of the at least one first substrate or the at least one second substrate.

5. The module according to one of claims 1-4, the magnetic core has a toroidal shape with a center hole.

6. The module according to claim 5, wherein the at least one first conductive pillar includes a first conductive pillar that passes through the center hole of the magnetic core and an additional first conductive pillar that does not pass through the center hole of the magnetic core.

7. The module according to claim 5, wherein the at least one second conductive pillar includes a second conductive pillar that passes through the center hole of the magnetic core and an additional second conductive pillar that does not pass through the center hole of the magnetic core.

8. The module according to one of claims 1-7, wherein the at least one first substrate includes at least two first substrate layers that separate the first primary conductor path from the first secondary conductor path.

9. The module according to claim 8, wherein the at least two first substrate layers are thin film insulators.

10. The module according to one of claims 1-9, wherein the at least one second substrate includes at least two second substrate layers that separate the second primary conductor path from the second secondary conductor path.

11. The module according to claim 10, wherein the at least two second substrate layers are thin film insulators.

12. The module according to one of claims 1-11, wherein an electrical input or output connection is provided on a surface of the at least one second substrate that does not face the at least one first substrate.

13. The module according to one of claims 1-12, wherein: the first primary conductor path, the second primary conductor path, and the at least one first conductive pillar define a primary transformer winding; and the first secondary conductor path, the second secondary conductor path, and the at least one second conductive pillar define a secondary transformer winding.

14. The module according to claim 13, wherein the primary transformer winding at least partially surrounds the secondary transformer winding.

15. The module according to one of claims 1-14, wherein: the first primary conductor path is electrically connected to the at least one first conductive pillar by at least one first via provided in the at least one first substrate; and the second primary conductor path is electrically connected to the at least one second conductive pillar by at least one second via provided in the at least one second substrate.

16. The module according to one of claims 1-15, wherein the module includes a DC-DC converter.

17. The module according to one of claims 1-16, wherein the at least one electrical component is directly mounted to the at least one first substrate.

18. The module of one of claims 1-17, wherein the encapsulant includes an epoxy resin with a silica filler.

19. A module comprising: a first substrate; a second substrate; an encapsulant layer between the first and the second substrates and encapsulating each of: first conductive pillars physically and electrically connecting the first and the second substrates; a first electrical component connected to the first substrate; and a magnetic core; and a first winding including the first conductive pillars, electrically connected to the first electrical component, and extending around the magnetic core and through the first and the second substrates.

20. The module of claim 19, further comprising a second winding; wherein the encapsulant layer includes second conductive pillars physically and electrical connecting the first and the second substrates; and the second winding includes the second conductive pillars and extends around the magnetic core and through the first and the second substrates.

21. The module of claim 20, wherein, when viewed in plan, at least a portion of the first electrical component overlaps with the magnetic core.

22. The module of claims 20 or 21, further comprising: a second electrical component connected to the first substrate; and a third electrical component connected to the second substrate.

23. The module of claim 22, wherein, when viewed in plan, the second and the third electrical components at least partially overlap with each other.

24. The module of claim 22 or 23, wherein the second winding is electrically connected to the second and the third electrical components.

25. The module of one of claims 20-24, wherein a portion of the first winding extends around a portion of the second winding in a multilayer arrangement.

26. The module of one of claims 19-21, further comprising a second electrical component connected to an exterior surface of the module.

27. The module of one of claims 19-26, wherein the module includes a DC-DC converter.

28. The module of one of claims 19-27, wherein the encapsulant layer includes an epoxy resin with a silica filler.

29. A system comprising: a mother substrate; and the module of one of claims 1-28 attached to the mother substrate.

30. A method of manufacturing a module, the method comprising: providing a first substrate with a first electronic component and first conductive pillars connected to the first substrate; providing a second substrate; connecting the first and the second substrates together with a magnetic core between the first and the second substrate such that the first conductive pillars physically and electrically connect the first and the second substrates; and applying an encapsulant to form an encapsulant layer between the first and the second substrates and to encapsulate the first electronic component, the first conductive pillars, and the magnetic core; wherein the module includes a first winding that includes the first conductive pillars, that is electrically connected to the first electrical component, and that extends around the magnetic core and through the first and the second substrates.

31. The method of claim 30, wherein the encapsulant layer includes second conductive pillars that physically and electrical connect the first and the second substrates; and the module includes a second winding that includes the second conductive pillars and that extends through the first and the second substrates and includes the first conductive pillars.

32. The method of claim 31, wherein, when viewed in plan, at least a portion of the first electrical component overlaps with the magnetic core.

33. The method of claims 31 or 32, wherein a second electrical component is connected to the first substrate; and a third electrical component is connected to the second substrate.

34. The method of claim 33, wherein, when viewed in plan, the second and the third electrical components at least partially overlap with each other.

35. The method of claim 33 or 34, wherein the second winding is electrically connected to the second and the third electrical components.

36. The method of one of claims 31-35, wherein a portion of the first winding extends around a portion of the second winding in a multilayer arrangement.

37. The method of one of claims 30-32, further comprising connecting a second electrical component to an exterior surface of the module.

38. The method of one of claims 30-37, wherein the module includes a DC-DC converter.

39. The method of one of claims 30-38, further comprising attaching the module to a mother substrate.

40. The method of one of claims 30-39, wherein the encapsulant includes an epoxy resin with a silica filler.