JPH11204352A - Transformer or circuit module having transformer, and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable realization of further reduction in side and thickness of a transformer. SOLUTION: Coils 2 and 3 are wound on and integrally jointed with magnetic cores 1a and 1b having the surfaces thereof insulation-treated. The coils are mounted on a insulating board 4 having coil housing parts 6 and are encapsulated with an encapsulating resin 11. Metal plating is carried out on the surface of the encapsulating resin 11, thus forming an electromagnetic shielding film. Coil terminals 7 are wound on the magnetic cores 1a and 1b, then fixed by silver paste or the like, and connected to terminal electrodes on the lower side via a conductor pattern 8 and through-holes 10 at the four corners. A circuit module having specified functions can also be produced by mounting a circuit component, such as an IC chip or the like on the board 4 between the coils 2 and 3. In manufacturing, a number of transformers are mounted on large aggregate boards, and working is carried out thereon. Finally, dicing is carried out to take out several of completed products. Thus, a surface- mounted transformer having small size and small thickness and high performance is provided inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for portable equipment, a transformer for use in an electroluminescence (EL) drive circuit for display and illumination, or a circuit module having a transformer and a method of manufacturing the same. About.

[0002]

2. Description of the Related Art In recent years, electronic equipment has been pursued to have higher performance and more functions, as well as smaller size and lighter weight, and surface mounting of components has become widespread as a circuit configuration for this purpose. I
Active and passive circuit components such as a C chip, a resistor, a capacitor, and an inductor are often used which are suitable for surface mounting. Transformers, ie, transformers, are indispensable components in power supply circuits and booster circuits, and various surface-mounting transformers are also supplied.
0, and includes a metal shield cover.

[0003]

These transformers are:
Although the dimensions are much smaller than before, they have not yet been sufficiently miniaturized, and have become a bottleneck in reducing the size and weight of portable devices. The present invention solves this problem and provides a small and high-performance transformer or a circuit module including the transformer.

[0004]

FIG. 1 is a diagram showing the principle of the construction of a transformer. A primary coil and a secondary coil are formed by winding a coil 2 and a coil 3 around a square-shaped magnetic core 1 made of magnetic material. The magnetic core 1 forms a closed magnetic circuit. In the present invention, two U-shaped magnetic cores obtained by dividing the magnetic core 1 into two parts at the center at the right and left sides are used, and the two are wound around each other to form the coil 2 and the coil 3, and the ends of the two magnetic cores are joined to each other. The structure integrated into a square shape is attached to an insulating substrate.
Each terminal of the coil is connected to a terminal pad provided on the substrate, and the terminal pad is connected to a terminal electrode for connection to an external circuit by a conductive pattern. Then, a sealing resin is laminated on the substrate, and a transformer is sealed therein. By forming a metal coating on the surface of the sealing resin by Ni plating or the like, this coating performs an electromagnetic shielding action.

In the present invention, a transformer having such a structure is manufactured using a collective substrate. That is, the transformer is mounted on each area of a large collective substrate including a large number of regions each serving as an individual transformer and having conductive patterns and through holes formed therein. Alternatively, not only the transformer but also components constituting a circuit together with the transformer are mounted together. Then, a frame is provided around the collective substrate, the resin is filled in the frame, the resin is solidified, the frame is removed, and the collective substrate is diced along the boundaries of the respective regions, so that individual resin-sealed complete transformers are formed. Alternatively, a large number of circuit modules having a transformer are taken. When the surface of the sealing resin is covered with the metal shield film as described above, the shield film is required not only on the upper surface but also on the side surfaces of the sealing resin. Therefore, after the sealing resin is solidified, half dicing is performed to a depth substantially reaching the collective substrate along the boundary of each transformer region. As a result, the sealing resin is divided into individual regions by the grooves to form side surfaces, and a metal film formed by electroless plating or the like is formed on the entire surface including the side surfaces. Thereafter, when the collective substrate is fully diced along the boundary of each transformer region, a transformer having a shield film provided on the entire surface of the sealing resin is obtained.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the first embodiment of the transformer according to the present invention.
In this embodiment, components are mounted on a substrate 4 made of an insulating material such as an epoxy resin containing glass.
Coils 2 and 3 are wound around two U-shaped magnetic cores 1a and 1b made of a magnetic material such as a silicon steel plate, permalloy, or ferrite, respectively, and are joined at a joining portion 5 which is an end of the magnetic cores 1a and 1b. The two magnetic cores are joined together to form a square-shaped closed magnetic circuit. The coil end 7 is formed by winding the end of the winding around a magnetic core and fixing the end with a conductive adhesive or paste solder. Although the surfaces of the magnetic cores 1a and 1b are usually insulative due to the formation of an oxide film even in the usual case, in the present embodiment, the magnetic cores 1a and 1b are subjected to chemical vapor deposition such as so-called parylene treatment to insulate the surfaces. Therefore, even if the end of the winding is wound around the magnetic core, there is no short circuit. The formation of the insulating film on the surface of the magnetic core can be performed by powder coating, electrostatic coating, or the like in addition to chemical vapor deposition.

[0007] A coil accommodating portion 6 which is a depression or a through hole is provided in the substrate 4. By inserting the coils 2 and 3 into the coil accommodating portion 6, the lower surfaces of the magnetic cores 1 a and 1 b are brought into contact with the surface of the substrate 4. This suppresses the increase in overall thickness. A conductive pattern 8 is formed on the substrate 4, and the coil terminal 7 is connected to a terminal pad 9 connected to the conductive pattern 8 with a conductive adhesive such as solder. The conductive pattern 8 is connected to each of the through holes 10 at the four corners of the substrate 4. In FIG. 2, the through-hole 10 is a conductively-curved curved surface that connects both surfaces of the substrate, but this portion was a circular through-hole in the manufacturing process. The through hole 10 is connected to a terminal electrode provided on the lower surface of the substrate 4, and this terminal electrode is connected to a circuit board of the device to mount a transformer.

The sealing resin 11 is laminated on the substrate 4 and the magnetic core 1
a, 1b and coils 2, 3 are sealed in a sealing resin 11 to form a completed transformer. Although the transformer is mechanically protected inside the sealing resin 11, a metal coating is formed on the surface of the sealing resin 11 by Ni plating or the like. This metal coating performs an electromagnetic shielding action.

Although the magnetic cores 1a and 1b shown in FIG. 2 have a rectangular cross section perpendicular to the magnetic field, the magnetic core may have a square or circular cross section. When the number of windings of the coil is extremely small, the magnetic core may be an integral part of a square shape from the beginning, but it is generally inconvenient to wind the core around a closed square core and the manufacturing cost is extremely low. It is disadvantageous, and in the present invention, it is wound and joined into a U-shape divided as described above. The joint at the joint 5 must be strong, otherwise the reluctance of this part will increase, the magnetic flux will decrease and the performance of the transformer will decrease.

FIG. 3 shows a couple of structures of the magnetic core joining portion 5. FIG. 3 (A) shows the magnetic cores 1a and 1b whose end faces are butted and joined by welding, bonding or the like. It is of this type. FIG. 3 (B) shows the magnetic cores 1a and 1b each provided with a step at each end, and overlapped and joined by welding, bonding, and the like. FIG. 3 (C) shows the step of the magnetic cores 1a and 1b fastened with screws 12. It was done.

Next, a method of manufacturing such a transformer will be described. For this purpose, an aggregate substrate having a large size is used, and the aggregate substrate includes a region to be a substrate for a large number of transformers. FIG. 4 is a perspective view showing a part of such a collective substrate 14, and each of the regions divided by vertical and horizontal boundaries 15 and 16 corresponds to an individual transformer. What is used for the substrate is the same kind of insulating material as used for the printed circuit board, in addition to the epoxy resin containing glass as described above. As shown in the figure, a large number of coil receiving portions 6 each having a rectangular hole are formed in the collective substrate 14. Also, a large number of conductive patterns 8, terminal pads 9, and through holes 10 are formed on the surface of the collective substrate 14, and the terminal pads 9 are connected to the through holes 10 by conductive patterns 8, and the terminals on the lower surface of the substrate are passed through the through holes 10. It is connected to the electrode.

Next, a conductive adhesive such as a silver paste is applied to the terminal pads 9 of the collective substrate 14 by printing or the like. Then, as shown in FIG. 5, the coils 2, 3 are mounted on the collective board 14 with their positions adjusted so that the coils 2, 3 are accommodated in the coil accommodating portion 6 and the coil terminals 7 are mounted on the terminal pads 9. Then, the conductive adhesive is reflowed to join the coil terminal 7 to the terminal pad 9. Magnetic core 1
The steps of winding the coils 2 and 3 around a and 1b, joining the magnetic cores integrally, and terminating the core to form a transformer component are performed separately from the preparation of the collective substrate 14.

Next, as shown in FIG. 6, a large number of through holes 10 (FIG. 5) of the collective substrate 14 are closed using a mask material 17 such as an adhesive tape. This is to prevent the resin from flowing out of the through hole 10 when filling the sealing resin. Then, the frame 18 is joined around the collective substrate 14.
The frame 18 is for injecting a sealing resin. There is no problem if the coil accommodating portion 6 is a concave portion and has a bottom. In the case of a through hole, though not shown, the lower surface of the collective substrate 14 is also provided over the entire surface or at least a portion of the through hole of the coil accommodating portion 6 It is necessary to cover with a mask material such as an adhesive tape.

Next, as shown in FIG. 7, the inside of a frame 18 is filled with a sealing resin 11 such as an epoxy resin and cured, and
After solidification of 1, the frame 18 is removed. If the assembly board in which the components are mounted and sealed in the resin is diced along the boundary lines 15 and 16, each divided portion becomes an individual transformer as shown in FIG. In the case of this embodiment,
As shown in FIG. 4, the boundaries 15 and 16 of the collective substrate 14 are arranged so as to pass through the center of the through hole 10. Therefore, after division, a part of the through hole 10 has conductive coatings at the four corners of the substrate 4 as shown in FIG. It becomes concave and conducts to terminal electrodes on the lower surface of the substrate.

Although the individual transformers can be obtained by the above steps and can be mounted on a circuit board and used, the sealing resin 11 protects the internal circuit components, but does not have the function of an electromagnetic shield. In order to prevent electromagnetic interference between circuit components and mutual induction between coils, it is possible to attach a metal shield cover to each transformer, but as mentioned earlier, the present invention uses a sealing resin. 1
A metal coating is formed on the surface of the substrate 1 and used as an electromagnetic shielding film. The shield film is formed by, for example, electroless nickel plating. However, if only the surface of the sealing resin 11 filled inside the frame 18 is covered with metal as shown in FIG. At this time, only the upper surface of the sealing resin 11 is metal-coated, and the side surface of the sealing resin 11 is in a state without metal coating. In order to effectively perform electromagnetic shielding, the entire surface of the sealing resin 11 must be covered with metal.

Then, after removing the frame 18 from the one shown in FIG.
The sealing resin 11 is vertically and horizontally halved at a depth reaching the surface of No. 4.
Dicing. FIG. 8 shows a half-diced product in which the sealing resin 11 is divided into grooves 19 and 20 for each region of the individual transformer. Can also form a metal coating. After that, if the collective substrate 14 is fully diced, each of the divided completed transformers has the entire surface of the sealing resin covered with metal, and has high electromagnetic shielding characteristics.

In the above-described method, as shown in FIG.
8 is filled with the sealing resin 11 and half-diced along all of the boundary lines 15 and 16, the frame 18 for resin injection is made into a mesh shape, and resin injection is performed as shown in FIG. As described above, the grooves 19 and 20 may be formed in the sealing resin 11. Alternatively, a part of the groove (for example, groove 1
9 and 20) can be formed by the frame 18 and the remaining grooves can be half-diced or the like. Such a distribution takes into account the complexity of the frame 18 and the time required for resin filling. May be determined.

Next, a second embodiment of the present invention will be described with reference to FIG. Basically, as in the first embodiment shown in FIG.
Are bonded and integrated at a bonding portion 5, a transformer having a closed magnetic path is mounted on the substrate 4, and the coil terminal 7 is bonded to the terminal pad 9 and packaged with the sealing resin 11.

The feature of this embodiment is that the magnetic core 1
In addition to the transformers a and 1b and the coils 2 and 3, an IC chip 21 and other circuit components 23 are mounted between the coil 2 and the coil 3, that is, inside the closed magnetic circuit. Therefore, although not shown, conductive patterns for these circuit components are formed on the substrate 4, and the IC chip 21 is connected to the conductive patterns by wire bonds 22. Unlike the terminal of FIG. 2, a terminal for connection to an external circuit is required other than the terminal for the coil terminal. Therefore, in FIG. Thus, the conductive pattern on the upper surface of the substrate 4 is connected to the terminal electrode on the lower surface.

The second embodiment configured as described above is a functional module that performs a specific circuit operation, whereas the first embodiment is a simple transformer. For example, it is an EL drive circuit. The additional components are located in a location between the two coils, which makes efficient use of space and minimizes the increase in size despite improved functionality.

The manufacturing method of the second embodiment is basically the same as that of the first embodiment shown in FIGS. However,
The collective substrate 14 is provided with bonding pads and conductive patterns for circuit components in addition to the conductive patterns for the transformer, thereby increasing the number of through holes 10 for terminal electrodes. And, of course, in the component mounting process of FIG.
In addition to mounting a transformer including the magnetic cores 1a and 1b and the coils 2 and 3, an IC and other circuit components are mounted.

In the above description, an embodiment of the transformer having a closed magnetic circuit having a U-shaped magnetic core has been described as an embodiment of the transformer. However, there is also a transformer having a closed magnetic path having another shape, for example, a magnetic core having a sun shape and two coils commonly wound around a central magnetic path. As will be readily appreciated, the invention is applicable to such. When a circuit module including not only the transformer but also other circuit elements is configured, circuit components are similarly arranged inside the closed magnetic circuit to effectively use space and to reduce the size.

[0023]

As is evident from the above description, the present invention makes it possible to obtain a transformer that is significantly smaller and thinner. The structure is mechanically protected by the sealing resin, and is electromagnetically shielded by the metal coating on the surface of the sealing resin. Therefore, the size does not increase because a shield case or the like is used as in the related art. Furthermore, by mounting circuit components other than a transformer together, a circuit module including a transformer can be realized.However, since the circuit components are arranged inside the closed magnetic circuit of the transformer, the size increase is minimized in this case as well. Only needs to be done. In terms of manufacturing, processing is advanced using a collective substrate, and finally, a large number of completed transformers are taken at a time by dicing, resulting in extremely high productivity. As a result, a compact and high-performance transformer or a circuit module having the transformer can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the basic configuration of a transformer.

FIG. 2 is a perspective view of a transformer according to the present invention.

FIG. 3 shows a joint of a magnetic core of the transformer of the present invention.

FIG. 4 is a perspective view showing a part of an aggregate substrate used for manufacturing the transformer of the present invention.

FIG. 5 is a perspective view showing a state where the transformer is attached to the collective substrate in the process of manufacturing the transformer of the present invention.

FIG. 6 is a perspective view showing a state in which a frame and a mask material are attached to the collective substrate in the process of manufacturing the transformer of the present invention.

FIG. 7 is a perspective view showing a state in which a sealing resin is filled in a frame attached to the collective substrate in a process of manufacturing the transformer of the present invention.

FIG. 8 is a perspective view showing a state in which the sealing resin on the collective substrate is half-diced in the manufacturing process of the transformer of the present invention.

FIG. 9 is a perspective view of a circuit module including the transformer of the present invention.

FIG. 10 is an external view of a conventional transformer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a, 1b Magnetic core 2, 3 Coil 4 Substrate 5 Joining part 6 Coil accommodating part 7 Coil terminal 8 Conductive pattern 10 Through hole 11 Sealing resin 14 Assembly board 15, 16 Boundary line 17 Mask material 18 Frame 19, 20 Groove 21 IC chip 23 Circuit parts

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 1/18 H01F 15/02 L 9/00 15/04 31/00 RU

Claims (6)

[Claims] 1. A closed magnetic circuit coil in which two magnetic cores each having a winding wound on a magnetic core are joined to each other and integrated, are attached to a substrate, a coil terminal is connected to a terminal electrode of the substrate, and a sealing resin is applied to the substrate. A transformer, wherein the coil is sealed and stacked. 2. A circuit module comprising a transformer, wherein a circuit component is mounted on a substrate inside a closed magnetic circuit of the transformer according to claim 1. 3. A transformer or a transformer characterized in that a metal film is formed on a sealing resin surface of a circuit module provided with the transformer according to claim 1 or the transformer according to claim 2 to form an electromagnetic shield film. Equipped circuit module. 4. A method for manufacturing a transformer, comprising: a conductive adhesive such as a paste solder or the like formed by printing or the like on a conductive pattern of a collective substrate having a large number of completed products and provided with a conductive pattern, a through hole, and the like. Applying a coil having a magnetic core of a closed magnetic circuit to each area of the collective substrate; reflowing the conductive adhesive, joining a coil terminal to a conductive pattern, and fixing the coil; Fixing the frame around the substrate, closing the through holes of the collective substrate with a mask material, filling the sealing resin on the collective substrate surrounded by the frame and solidifying, removing the frame, A method of manufacturing a transformer, wherein a large number of individual finished products are obtained by a process including a step of dicing a collective substrate on which the sealing resin is laminated along a boundary line passing through a through hole. 5. A method of manufacturing a circuit module having a transformer, wherein in the step of mounting the coil on the collective substrate in the method of manufacturing a transformer according to claim 4, another circuit component is provided inside the closed magnetic path of the coil. A method of manufacturing a circuit module having a transformer, wherein the step of fixing the coil by reflowing the conductive adhesive, including mounting the component, includes fixing the circuit component. 6. A method for manufacturing a transformer or a method for manufacturing a circuit module including a transformer, wherein the method for manufacturing a transformer according to claim 4 or the method for manufacturing a circuit module including a transformer according to claim 5. After the step of filling the solidification resin into the collective substrate, solidifying and removing the frame, half dicing the sealant to a depth almost reaching the collective substrate along the boundary line, and electroless plating etc. A transformer or transformer characterized by adding a step of forming a metal film on a sealing resin surface to form an electromagnetic shielding film, and after these steps, taking a large number of individual finished products by a step of full dicing of the collective substrate. The manufacturing method of the circuit module provided with.