TW201436679A - Method of applying a stress relieving material to an embedded magnetic component - Google Patents

Abstract

A method of manufacturing a substrate includes providing a substrate with a cavity and a post in the cavity, dispensing an elastic filling material in the cavity, inserting a magnetic core including a core hole such the post extends through the core hole, curing the elastic filling material, forming holes in the substrate outside of the cavity and in the post, and forming via-in-via structures in the holes.

Description

Method of applying a stress relief material to an embedded magnetic component

This invention relates to substrates having embedded magnetic components. More particularly, the present invention relates to substrates having embedded magnetic components surrounded by stress relief materials.

It is known to provide a transformer by embedding a core 206 (also referred to as a ferrite core) in a printed circuit board 202 and by forming a winding around the core 206 using conductors 208 and vias 210, as in, for example, FIG. 21 of the present application. The figure corresponds to the pattern in U.S. Patent No. 8,203,418.

U.S. Patent No. 8,203,418 provides an integrated planar transformer and electronic component including at least one broadband planar transformer disposed in a planar substrate. U.S. Patent No. 8,203,418 uses a cylindrical cavity 204 to hold the core 206. The core 206 has a ring shape with a hole therebetween. The hole in the middle of the core 206 is filled with an epoxy material, and the epoxy material is drilled to form a passage. The cavity 204 of U.S. Patent No. 8,203,418 is cylindrical such that the central portion of the core 206 is supported by an epoxy material and exposed to a laminating load applied to the different layers during the lamination process. The compressive load of the planar substrate and the core 206. Since the central portion of the core 206 is an epoxy material, it is difficult to create a path in the central portion of the core 206. The mismatch in the coefficient of thermal expansion (CTE) of the materials used in the planar substrate and the center core will result Thermal stress, which will cause the via and/or the dielectric material used therein to be destroyed.

U.S. Patent No. 7,271,697 provides a small circuit and inductor component in which a multilayer printed circuit is formed on each side of a planar substrate. U.S. Patent No. 7,271,697 uses a pre-impregnated composite fiber material (prepreg material) to fill the space surrounding the core. The reason for using the prepreg material in U.S. Patent No. 7,271,697 is that it contributes to the manufacturing process and the prepreg material has the same coefficient of thermal expansion as the planar substrate because the prepreg and the planar substrate are made of the same material. However, the inventors of the present application subsequently found that the prepreg material conforms to the space during lamination and imparts a certain amount of pressure to the core which negatively affects the magnetic permeability properties of the core due to magnetostriction.

U.S. Patent Application Publication No. 2008/0816124 teaches a wireless inductive device and a method of making such an inductive device. The manufacturing method of U.S. Patent Application Publication No. 2008/0816124 includes forming a conductor on two substrates (top and bottom) and magnetically connecting the two substrates between the two substrates to produce an inductive device. U.S. Patent Publication No. 2008/0816124 does not use a cushioning material to prevent compression of the core during the manufacturing process, which can result in damage to the core and also negatively affect the magnetic permeability properties of the core due to magnetostriction.

U.S. Patent No. 8,234,778 teaches a substrate inductive device and a method for fabricating an inductive device that includes three substrates: a top, a bottom, and a middle. The top and bottom substrates contain conductors and the intermediate substrate contains a core with electrical contacts. The three substrates are connected or assembled to create a device. This configuration is difficult to manufacture in mass production and provides a lower via hole density.

In order to solve the problems described above, a preferred embodiment of the present invention provides a method of providing a substrate having an embedded magnetic member surrounded by a stress relief material that protects the magnetic member from mechanical stress and eliminates Magnetostrictive effect on magnetic components should.

A method of manufacturing a substrate according to a preferred embodiment of the present invention includes providing a substrate having a cavity and a pillar in the cavity, dispensing the elastic filler material into the cavity, and inserting a core including the core hole to cause the cylinder Through the core hole, the elastic filling material is solidified, holes are formed in the substrate outside the cavity and in the column body, and a hole mesoporous structure is formed in the hole.

The method preferably further includes forming a conductor connected to the pore structure in the pore. The conductor and the hole-to-hole structure preferably provide primary and secondary windings of the transformer.

A method of manufacturing a substrate according to a preferred embodiment of the present invention includes providing a substrate having a cavity and a pillar in the cavity, inserting a core including a coating of an elastic filler material and a core hole such that the pillar penetrates the core hole, A hole is formed in the substrate outside the cavity and in the column body, and a hole mesoporous structure is formed in the hole.

Preferably, the method further comprises providing a prepreg ring in the cavity prior to the step of inserting the core. The method preferably further includes forming a conductor connected to the pore structure in the pore. The conductor and the hole-to-hole structure preferably provide primary and secondary windings of the transformer.

The step of forming the pore structure in the pore preferably includes forming a metal layer in the pore. The step of forming the pore structure in the pore preferably further includes forming an insulating coating over the metal layer in the pore. The step of forming the pore structure in the pore preferably further comprises forming a metal layer over the insulating coating.

The above and other features, components, steps, features and advantages of the present invention will become more apparent from

10‧‧‧Substrate

11‧‧‧ cavity

12‧‧‧Cylinder

13‧‧‧Flexible filling material

14‧‧‧Magnetic core

15‧‧‧ copper foil

16‧‧‧ access hole

17‧‧‧ Copper plating

18‧‧‧Conductor

19‧‧‧Polypylene coating

20a‧‧‧Pre-drilled adhesive

20b‧‧‧Bronze/copper foil

21‧‧‧ access hole opening

22‧‧‧ copper plating

23‧‧‧Conductors

30‧‧‧Substrate

31‧‧‧ cavity

32‧‧‧Cylinder

33‧‧‧Elastic material coating

34‧‧‧Magnetic core

34a‧‧‧Prepreg ring

34b‧‧‧Prepreg layer

35‧‧‧ copper foil

36‧‧‧ access hole

37‧‧‧copper plating

38‧‧‧Conductors

202‧‧‧Printed circuit board

204‧‧‧ cylindrical cavity

206‧‧‧Magnetic core

208‧‧‧ conductor

210‧‧‧ pathway

1-12 show the fabrication of an embedded magnetic element in accordance with a first preferred embodiment of the present invention The method of the substrate.

1 is a perspective view of a substrate 10 having a cavity 11.

2 is a cross-sectional side view showing the core 14 inserted into the cavity 11.

3 is a perspective view of a substrate 10 having a magnetic core 14.

4 is a cross-sectional side view showing the copper foil 15 laminated to the substrate 10.

FIG. 5 is a cross-sectional side view showing the via hole 16 drilled in the substrate 10.

FIG. 6 is a cross-sectional side view showing copper plating 17 on the substrate 10 and in the via hole 16.

FIG. 7 is a perspective view of conductor 18 shown on substrate 10.

FIG. 8 is a side cross-sectional view showing the parylene coating 19 on the substrate 10.

Fig. 9 is a side cross-sectional view showing the pre-drilled adhesive 20a and the copper layer 20b laminated on the substrate 10.

FIG. 10 is a side cross-sectional view showing the via hole opening 21 in the copper foil 20b formed on the substrate 10.

FIG. 11 is a side cross-sectional view showing the copper plating 22 formed on the substrate 10 and in the via hole 16.

FIG. 12 is a perspective view showing the conductor 23 formed on the substrate 10.

13-20 show a method of fabricating a substrate having an embedded magnetic component in accordance with a second preferred embodiment of the present invention.

FIG. 13 is a perspective view of a substrate 30 having a cavity 31.

FIG. 14 is a cross-sectional side view showing the core 34 inserted into the cavity 31.

15 is a perspective view of a substrate 30 having a pre-coated core 34.

FIG. 16 is a cross-sectional side view showing the prepreg layer 34b and the copper foil 35 on the substrate 30.

17 is a cross-sectional side view showing the prepreg layer 34b and the copper foil 35 laminated to the substrate 30.

FIG. 18 is a cross-sectional side view showing the via hole 36 drilled in the substrate 30.

19 is a cross-sectional side view showing copper plating 37 on substrate 30 and via holes 36.

FIG. 20 is a perspective view of conductor 38 shown on substrate 30.

Figure 21 shows a known method of embedding a magnetic core in a printed circuit board.

1-12 show a method of fabricating a substrate having an embedded magnetic component in accordance with a first preferred embodiment of the present invention. 13-20 show a method of fabricating a substrate having an embedded magnetic component in accordance with a second preferred embodiment of the present invention.

In contrast to U.S. Patent No. 8,203,418, a preferred embodiment of the invention includes an annular cavity comprising a support cylinder disposed on a planar substrate intermediate the annular cavity. The support cylinder reduces the lamination load on the core. In a preferred embodiment of the invention, the via in the center of the core is formed in the support pillar of the planar substrate and is not formed in an epoxy material such as U.S. Patent No. 8,203,418. Since the passage is formed in the support cylinder instead of the epoxy material in the preferred embodiment of the present invention, the passage can be formed more reliably. Since the vias are disposed in a majority of the homogeneous material of the planar substrate, thermal stress can be significantly reduced and prevented because there is no mismatch in the coefficient of thermal expansion between the planar substrate and the epoxy material. The annular cavity significantly reduces and prevents any stress from acting on the core. The support cylinder of the planar substrate will absorb the compressive load imparted during lamination of the circuit layer, thereby significantly reducing the compressive force applied to the core.

A preferred embodiment of the present invention solves the problems associated with the method of U.S. Patent No. 7,271,697 by reducing the load applied to the core during the manufacturing steps of forming the transformer. A preferred embodiment of the present invention uses an elastomeric filler material dispensed in a precise volume around the space of the core to prevent compression of the magnetic material and to eliminate voids. Known voids can lead to manufacturing processes Layered. The elastomeric filler material is preferably a low viscosity crucible material; however, other suitable materials can be used, including other elastomeric materials that can withstand the conditions of the manufacturing process, such as temperature. Typically, the volume of the elastomeric fill material is determined prior to the start of manufacture. Surface scanning can be used, for example, to determine the volume of the cavity and core. The volume of the elastomeric filler material can then be determined by subtracting the core volume from the cavity volume, taking into account the properties of the elastomeric filler material, such as expansion or contraction during any curing process. The volume of the elastomeric filler material is preferably accurately determined because excessive elastic filler material can cause cracking. The volume of the elastomeric fill material is equal to or substantially equal to the cavity volume minus the core volume within manufacturing tolerances. Manufacturing tolerances include tolerances associated with the formation of cavities and cores and the specific properties of the type of elastomeric fill material used.

By using a controlled volume of elastomeric filler material, a preferred embodiment of the present invention ensures that the elastomeric filler material is only located in the space surrounding the core and does not migrate to the circuit region where the via will be formed. The volume of the elastomeric fill material to be dispensed is equal to or substantially equal to the annular cavity volume minus the core volume. The use of an automatic dispensing device to apply the elastomeric filler material eliminates the possibility of overfilling/deficient cavity containing the core. This also prevents the elastic fill material from migrating to the via hole area.

Preferred embodiments of the invention include a method of embedding a magnetic material in a planar substrate. More specifically, preferred embodiments of the present invention include a method of embedding a magnetic core in a printed circuit board or a rigid flex circuit. The method of the preferred embodiment of the present invention achieves a high yield manufacturing process that produces small circuits with high functional reliability and embedded cores for inductors or transformers. The embedded process and circuit configuration enable efficient and reproducible fabrication of small circuits and small magnetic devices with high voltage, high current capacity, and high resistance to physical stress. The elastomeric filler material used to fill the annular cavity protects the core from mechanical stress and eliminates the magnetostrictive effect on the core.

Some preferred embodiments of the present invention preferably include a hole-to-hole structure in which the vias share the same via hole, the via hole significantly reducing and preventing leakage inductance between the primary winding and the secondary winding of the transformer and reducing the total number of via holes Thereby allowing further miniaturization. U.S. Patent No. 8,203,418 B2 and/or U.S. Patent Publication No. 2008/0186124 A1 does not utilize the pore mesoporous structure, and thus the higher wiring density that may be obtained by the pore structure in the pores cannot be achieved.

In a preferred embodiment of the invention in which the aperture structure is used, a plurality of coaxial independent conductors are fabricated on the walls of the via holes drilled in the planar substrate near the core. The planar substrate is typically a printed circuit board or a rigid flexible circuit. The printed circuit board can be made of FR-4 epoxy laminate or any other suitable material. Any suitable material may be used including, for example, a polyimide-based cladding, a copper-coated polyimide, an epoxy resin, an acrylic adhesive, a copper-clad epoxy laminate.

1-12 show a method of fabricating a substrate having an embedded magnetic component in accordance with a first preferred embodiment of the present invention.

A substrate 10 having an embedded magnetic component is fabricated in accordance with a first preferred embodiment of the present invention. The substrate 10 preferably has a planar shape. Substrate 10 is typically a printed circuit board, such as an FR-4 epoxy laminate. As shown in FIG. 1, a cavity 11 is formed in the substrate 10 using a numerically controlled (NC) controlled depth wiring machine. The cavity 11 preferably has an annular shape with the cylinder 12 at the center of the cavity 11. Any other suitable method of creating a cavity can be used including, for example, embossing and molding. The possible methods that can be used depend on the type of substrate used. Instead of having a circular perimeter, the perimeter of the cavity 11 can have any suitable shape including, for example, an elliptical or square shape.

Next, as shown in FIG. 2, the elastic fill material 13 is dispensed into the cavity 11 using a controlled volume automatic dispensing device. The elastic filler material 13 is preferably a low viscosity tantalum material. also Any other elastomeric material that can withstand the conditions of the manufacturing process, such as temperature, can be used.

The core 14 is inserted into the cavity 11. Preferably, the pick and place device is used; however, the core 14 can be inserted into the cavity 11 using any suitable method, including manual insertion. The core 14 is typically ferrite; however, other suitable magnetically permeable materials, such as powder cores, may also be used. The choice of material for the core 14 affects the type of material that can be used for the elastomeric fill material 13.

An additional elastic fill material 13 is dispensed on top of the core 14. The additional elastic fill material 13 is dispensed using the same controlled volume automatic dispensing device for dispensing the original elastic fill material 13 into the empty cavity 11. However, additional elastic fill material 13 can be dispensed using different equipment.

All of the elastic filler material 13 is then thermally cured. The conditions (including time and temperature) used to thermally cure the elastomeric filler material depend on the material used for the elastomeric filler material. Curing produces a substrate 10 having a magnetic core 14 inserted into the cavity 11 as shown in FIG.

As shown in FIG. 4, copper foil 15 is laminated on the top and bottom surfaces of substrate 10. It is preferred to use a vacuum lamination process to laminate the copper foil 15; however, other suitable processes may be used. While laminated copper is preferred, other suitable electrically conductive materials can be used and other suitable methods of providing electrically conductive materials can be used. For example, instead of using copper, other conductive materials such as silver or aluminum can be used; and instead of laminated copper, conductive ink can be printed.

FIG. 5 shows via holes 16 drilled in the substrate 10 around the core 14 and within the cylinder 12. The via hole 16 is preferably drilled using an NC drill; however, the via hole 16 can be formed using any suitable method or machine.

6 shows the top and bottom surfaces of the substrate 10 and the via holes 16 plated with copper plating 17.

In FIG. 7, conductors 18 are formed on the top and bottom surfaces of substrate 10. The conductor 18 is preferably printed and etched using a standard PCB process. The conductor 18 can be used as, for example, a winding of a transformer.

Next, as shown in FIG. 8, a parylene coating 19 is applied to the top and bottom surfaces of the substrate 10 and into the via holes 16 to form an insulator, whereby a hole mesoporous structure can be formed. Epoxides, polymers, liquid polyamines or any other insulating material can be used in place of parylene.

As shown in FIG. 9, the pre-drilled adhesive and copper layer 20 are laminated on the top and bottom surfaces of the substrate 10. Vacuum lamination is preferred to laminate the pre-drilled adhesive with copper layer 20; however, other suitable processes can be used.

As shown in FIG. 10, via hole openings 21 are formed on the top and bottom surfaces of the substrate 10. The via opening 21 is preferably printed and etched using a standard PCB process.

Next, as shown in FIG. 11, copper plating 22 is plated on the top and bottom surfaces of the substrate 10 and in the via holes 16 to form a via-hole structure.

Finally, in FIG. 12, conductors 23 are formed on the top and bottom surfaces of the substrate 10. The conductor 23 is preferably printed and etched using a standard PCB process. The conductor 23 can be a secondary winding of a transformer having a turns ratio of 5:1.

13-20 show a method of fabricating a substrate having an embedded magnetic component in accordance with a second preferred embodiment of the present invention. One difference between the first preferred embodiment of the present invention and the second preferred embodiment is that the core 34 is pre-coated with an elastomeric material and the pre-impregnated (prepreg) ring is used to fill the cavity 31. The second preferred embodiment removes the dispensing step and the curing step of the elastic filler material 13 and prevents the generation of polyfluorene oxide on the surface of the substrate 30, thereby increasing the yield.

In order to fabricate a substrate having an embedded magnetic component in accordance with a second preferred embodiment of the present invention, a substrate 30 is provided. Like the substrate 10, the substrate 30 preferably has a planar shape. Substrate 30 is typically a printed circuit board, such as an FR-4 epoxy laminate. As shown in FIG. 13, a cavity 31 is formed in the substrate 30 using an NC controlled depth wiring machine. The cavity 31 preferably has an annular shape with the cylinder 32 at the center of the cavity 31. Any other suitable method of creating a cavity can be used including, for example, embossing and molding. The possible methods that can be used depend on the type of substrate used. Instead of having a circular perimeter, the perimeter of the cavity 31 can have any suitable shape including, for example, an elliptical or square shape.

Next, as shown in Figures 14 and 15, a core 34 having a coating 33 of elastomeric material is provided. The elastomeric coating 33 is preferably a low viscosity tantalum material. Any other elastomeric material that can withstand the conditions of the manufacturing process, such as temperature, can also be used. A prepreg ring 34a is also provided. The prepreg ring 34a is preferably a resin impregnated composite fiber fabric. Preferred materials are medium or high Tg epoxy prepregs.

The prepreg ring 34a is inserted into the cavity 31, and then the core 34 is inserted into the cavity 31. The prepreg ring 34a is preferably inserted into the cavity 32 using a pick and place device; however, the prepreg ring 34a can be inserted into the cavity 31 in any suitable manner, including manual insertion. The core 34a is preferably inserted into the cavity 31 using a pick and place device; however, the core 34 can be inserted into the cavity 31 in any suitable manner, including manual insertion. The core 34 is typically ferrite; however, other suitable magnetically permeable materials, such as powder cores, may also be used. The choice of material for the core 34 affects the type of material that can be used for the elastomeric coating 33.

As shown in FIG. 16, a combination of prepreg layers 34b layered on top of copper foil 35 is preferably laminated to the top of substrate 30. The prepreg ring 34a and the prepreg layer 34b are preferably made of the same material. As shown in Figure 17, the prepreg layer 34b is preferably at a specified pressure and at a specified temperature. And the copper foil 35 is laminated to the top surface of the substrate 30. Other suitable processes can also be used. While laminated copper is preferred, other suitable electrically conductive materials can be used and other suitable methods of providing electrically conductive materials can be used. For example, instead of using copper, other conductive materials such as silver or aluminum can be used; and instead of laminated copper, conductive ink can be printed. The copper foil 35 may also be laminated to the substrate 30 using an epoxy adhesive. The molten resin from the prepreg ring 34a and the prepreg layer 34b fills the voids in the cavity between the core 34 and the substrate 30 during the lamination process.

FIG. 18 shows via holes 36 drilled in the substrate 30 around the core 34 and within the post 32. The via hole 36 is preferably drilled using an NC drill; however, the via hole 36 can be formed using any suitable method or machine.

19 shows the top and bottom surfaces of the substrate 30 and the via holes 36 plated with copper plating 37.

In FIG. 20, conductors 38 are formed on the top and bottom surfaces of substrate 30. The conductor 38 is preferably printed and etched using a standard PCB process. The conductor 38 can be used as, for example, a winding of a transformer.

A hole mesoporous structure can be formed in the substrate 30 using the steps discussed above with respect to Figures 8-12.

It should be understood that the above description is only illustrative of the invention. Various substitutions and modifications can be made by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and

10‧‧‧Substrate

11‧‧‧ cavity

12‧‧‧Cylinder

Claims (13)

A method of manufacturing a substrate, comprising: providing a substrate having a cavity and a pillar in the cavity; distributing an elastic filling material into the cavity; inserting a core including a core hole such that the cylinder penetrates the core hole Curing the elastic filling material; forming a hole in the substrate outside the cavity and in the column; and forming a hole mesoporous structure in the holes. The method of claim 1, further comprising forming a conductor connected to the pore structure in the pores. The method of claim 2, wherein the conductors and the mesoporous structures of the holes provide primary and secondary windings of the transformer. The method of claim 1, wherein the step of forming the pore structure in the pores comprises forming a metal layer in the pores. The method of claim 4, wherein the step of forming the pore structure in the pores further comprises forming an insulating coating over the metal layer in the pores. The method of claim 5, wherein the step of forming the pore structure in the pore further comprises forming a metal layer over the insulating coating. A method of manufacturing a substrate, comprising: providing a substrate having a cavity and a pillar in the cavity; inserting a core including a coating of an elastic filler material and a core hole such that the pillar penetrates the core hole; Forming a hole in the substrate outside the cavity and in the column; and forming a hole-hole structure in the holes. The method of claim 7, further comprising providing a prepreg ring in the cavity prior to the step of inserting the core. The method of claim 7, further comprising forming a conductor connected to the pore structure in the pores. The method of claim 9, wherein the conductors and the mesoporous structures of the holes provide primary and secondary windings of the transformer. The method of claim 7, wherein the step of forming the pore structure in the pores comprises forming a metal layer in the pores. The method of claim 11, wherein the step of forming the pore structure in the pores further comprises forming an insulating coating over the metal layer in the pores. The method of claim 12, wherein the step of forming the pore structure in the pore further comprises forming a metal layer over the insulating coating.