JP4148573B2 - Mold type converter and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a package structure of a small and thin mold type converter for supplying a stable DC power to a load portion of an electronic device, for example.
[0002]
[Prior art]
In recent years, with the miniaturization of electronic devices, electronic components that are components of electronic devices are also required to be small and thin.
For this reason, conventionally, in mold-type converters, various attempts have been made to improve the size and thickness, such as surface mounting electronic components such as a transformer on a substrate.
[0003]
[Problems to be solved by the invention]
However, the conventional molded converter has not been sufficiently reduced in size and thickness.
On the other hand, in the mold type converter, the L value (self-inductance value) of the transformer fluctuates due to the expansion and contraction of the mold resin during the resin sealing process, so it is difficult to stabilize the characteristics. There was a problem.
[0004]
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a small and thin mold converter having stable characteristics and small variations. .
[0005]
[Means for Solving the Problems]
The invention of claim 1, wherein has been made in order to achieve the above object, an insulating substrate on which predetermined electronic components are mounted on the surface of the other side to together if at least the transformer is mounted on one surface, the a mold converter and a package portion for sealing the predetermined electronic components on at least the transformer and the other surface of the insulating substrate on one surface of the insulating substrate, the package unit, the linear expansion coefficient of 10 in ^{~ 12 × 10 -6 · K -1} , and is composed of a mold resin made of a thermosetting low stress epoxy resin, the transformer, between the magnetic core of the primary winding and the secondary winding side A predetermined gap is provided, and at least the gap of the magnetic core is filled with a thermosetting resin having a linear expansion coefficient of 10 to 12 × 10 ⁻⁶ · K ⁻¹ so that the constituent members of the transformer are fixed in advance. der those who are It is characterized in.
According to a second aspect of the present invention, in the first aspect of the invention, in the transformer, at least a gap space between the magnetic cores is filled with a thermosetting resin different from the mold resin constituting the package portion. It is characterized by that.
According to a third aspect of the present invention, in the first aspect of the present invention, the transformer is characterized in that at least a gap space between the magnetic cores is filled with the mold resin constituting the package portion .
The invention of claim 4, wherein, in the invention according to any one of claims 1 to 3, wherein the insulating substrate is characterized in that the linear expansion coefficient of 7~12 × 10 ^-6 · K ^-1 .
According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the corner portion of the bobbin of the transformer is formed in a curved surface or a chamfered shape .
According to a sixth aspect of the present invention, there is provided an insulating substrate in which at least a transformer is mounted on one surface and a predetermined electronic component is mounted on the other surface, and at least a transformer on one surface of the insulating substrate. A method of manufacturing a mold type converter comprising a step of forming a package part by sealing a predetermined electronic component on the other surface of the insulating substrate with a mold resin, wherein a linear expansion coefficient is used as the mold resin of the package part. Is 10-12 × 10 ⁻⁶ · K ⁻¹ , and is made of a thermosetting low stress epoxy resin, and the transformer is between the primary winding side and secondary winding side magnetic cores. A predetermined gap is provided, and at least the gap of the magnetic core is filled with a thermosetting resin having a linear expansion coefficient of 10 to 12 × 10 ⁻⁶ · K ⁻¹ so that the constituent members of the transformer are fixed in advance. It is characterized by using what is worn.
[0006]
For the present invention, the mold resin package portion sealing the predetermined electronic components on at least transformer and insulating the other surface of the substrate on the one surface of the insulating substrate, a coefficient of linear expansion. 10 to 12 × 10 ^{-6 -Since} it is K ^-1 and is made of a thermosetting low stress epoxy resin, the amount of expansion and contraction of the mold resin in the resin sealing process is small, and fluctuations in the L value of the transformer can be suppressed. It is possible to obtain a mold type converter having stable characteristics.
Moreover, according to the present invention, since the thermosetting resin having a linear expansion coefficient of 10 to 12 × 10 ⁻⁶ · K ⁻¹ is filled at least in the gap between the magnetic cores of the transformer, the constituent members are fixed in advance. , it is possible to carry out during the resin sealing step without voids or the like occurs, easily and reliably sealed, it is possible to provide a mold converter with stable characteristics.
Further, Oite the present invention, lever using any of various different from the molding resin for sealing the resin filling the like gap transformer core, it is possible to expand the selection range of the transformer.
Furthermore, since the Oite the present invention, the corner portions of the transformer bobbin by forming into a curved or chamfered shape, it is possible to smoothly flow the resin in the vicinity of the corner portions of the transformer bobbins during resin sealing, It becomes possible to reduce molding defects.
In addition, when the corner portion of the bobbin of the transformer is an acute angle, it tends to be the starting point of the mold crack, but the crack can be prevented by making the corner portion of the bobbin curved or chamfered like the present invention, and it is thinner. Since resin molding is possible, the package can be thinned.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of a mold type converter according to the present invention will be described in detail with reference to the drawings.
FIG. 1A is a plan view showing the configuration of the mold converter of the present embodiment, FIG. 1B is a front sectional view showing the internal configuration of the embodiment, and FIG. It is a bottom view which shows the structure of embodiment.
[0008]
As shown in FIGS. 1A to 1C, the mold type converter 1 according to the present embodiment includes a rectangular insulating substrate 2 on which a wiring pattern (not shown) of a predetermined DC-DC converter circuit is formed. Various electronic components 4 and 5 are surface-mounted on both surfaces of the insulating substrate 2. The electronic components 4 and 5 on the insulating substrate 2 are sealed by a package portion 3 formed by molding resin, which will be described later.
[0009]
In the present embodiment, it is preferable to use the insulating substrate 2 having a linear expansion coefficient of 7 to 12 × 10 ⁻⁶ · K ⁻¹ from the viewpoint of expansion and contraction stress.
[0010]
As such an insulating substrate 2, for example, a substrate made of ceramics such as Al ₂ O ₃ or a substrate laminated with glass-epoxy resin is used.
[0011]
The dimensions of the insulating substrate 2 are about 30 mm in length, about 20 mm in width, and about 1 mm in thickness.
[0012]
As shown in FIGS. 1A to 1C, a small transformer 6 and various electronic components (coil, IC chip, etc.) are formed on one surface of the insulating substrate 2 (the lower surface in FIG. 1B). Resistor, capacitor, etc.) 5 are fixed by, for example, soldering.
[0013]
Moreover, the various electronic components 4 which comprise a DC-DC converter are being fixed also to the other surface (upper side surface in FIG.1 (b)) of the insulated substrate 2 by soldering etc., for example.
[0014]
FIG. 2 is a plan view showing the insulating substrate fixed to the lead frame.
In the case of the present embodiment, the insulating substrate 2 on which the electronic components 4 and 5 are mounted is sealed with a mold resin while being fixed to the lead frame 7.
[0015]
The lead frame 7 is made of, for example, a metal material such as a copper alloy or an iron-nickel alloy (for example, 42 alloy). As shown in FIG. 2, a rectangular outer frame portion 7a and the outer frame portion It is composed of a plurality of connection portions 7b and 7c provided inside 7a.
[0016]
Here, the connecting portion 7b of the lead frame 7 is formed integrally with the outer frame portion 7a so as to extend in the longitudinal direction. In the case of the present embodiment, a pair of connection portions 7 b are provided on both sides of the four insulating substrates 2 fixed to the lead frame 7. In this case, the end portions of the respective connection portions 7b are arranged to face each other with an interval slightly shorter than the width of the insulating substrate 2.
[0017]
In the present embodiment, as shown in FIG. 2, after the opposite long edges of the insulating substrate 2 are placed on the tip of the connecting portion 7 b of the lead frame 7 and soldered, for example, a known transfer molding method is used. The package part 3 is formed by
[0018]
That is, the lead frame 7 to which the insulating substrate 2 is fixed is placed in a cavity of a mold (not shown), the mold is closed, and a tablet-like resin is put into the mold pot. Here, the mold is kept at a high temperature of about 160 to 180 ° C., and the charged resin starts to melt from the surface in contact with the mold.
[0019]
Then, by lowering a plunger (not shown) attached to the transfer molding machine, the molten resin flows from the pot of the mold into the cavity.
Further, when the predetermined time has elapsed and the resin has hardened, the mold is opened and the molded product is taken out.
[0020]
Thereafter, the connecting portion 7c of the lead frame 7 is cut, and the connecting portion 7b after the cutting is formed into a gull wing shape by bending to obtain a terminal portion 8 having a shape suitable for surface mounting. By such a method, it is possible to obtain a surface-mounted mold converter 1 having a length of about 37 mm, a width of about 28 mm, and a height of about 8 mm.
[0021]
FIG. 3 is a schematic configuration diagram for illustrating a dimensional relationship of the package part 3 in the present embodiment.
In order to obtain a thin mold type converter 1 in the present invention, it is necessary to make the thickness of the package part 3 as thin as possible.
Therefore, in the present embodiment, the package is formed so that the thickness of the upper resin portion of the highest electronic component 4 or 5 mounted on each surface of the insulating substrate 2 is smaller than a predetermined value. The part 3 is formed.
On the other hand, when the thickness of the package part 3 is too thin, a problem arises because the withstand voltage decreases.
[0022]
Considering these points, in the case of the present embodiment, for example, the thickness D ₁ of the resin portion on the surface of the IC chip 4A having the highest height among the electronic components 4 mounted on one surface of the insulating substrate 2 is set. The thickness is preferably 0.4 to 1 mm, more preferably 0.45 to 0.5 mm.
[0023]
Similarly, the thickness D ₂ of the resin portion on the surface of the transformer 6 mounted on the other surface of the insulating substrate 2 is preferably configured to be 0.4 to 1 mm, and more preferably is 0.2 mm. It is 45-0.5 mm.
[0024]
FIG. 4A is a front view showing the external configuration of the transformer in the present embodiment, and FIG. 4B is a side view showing the external configuration of the transformer.
5A is a front view showing the structure of a general transformer core, FIG. 5B is a front view showing the structure of the transformer core of the present embodiment, and FIG. FIG. 6 is an enlarged view of a portion A indicated by a one-dot chain line in FIG.
[0025]
4A and 4B, the transformer 6 used in the present embodiment includes a pair of cores (magnetic cores) 9 and 10 made of a magnetic material and a bobbin 11 as in the conventional example. It is configured.
[0026]
Moreover, as shown in FIG.5 (b), the primary winding 12 and the secondary winding 13 which comprise a DC-DC converter circuit are wound by winding part 9a, 10a of each core 9,10. .
[0027]
By the way, in the above-described resin molding, a force acts so as to contract the cores 9 and 10 of the transformer 6, and a gap between the winding portions 9a and 10a of the cores 9 and 10 of the transformer 6 (see FIG. (Not shown) and the resin flows into the spaces 14 and 15, the cores 9 and 10 expand and contract, and the L value of the transformer 6 changes.
[0028]
Therefore, in the present embodiment, a resin having a linear expansion coefficient close to that of the insulating substrate 2 is used as the sealing mold resin.
[0029]
In this case, the linear expansion coefficient of the preferred mold resin is 10~12 × 10 ^-6 · K ^-1.
[0030]
A resin having a linear expansion coefficient smaller than 10 × 10 ⁻⁶ · K ⁻¹ is difficult to realize with the current technology. On the other hand, if the linear expansion coefficient of the mold resin is larger than 12 × 10 ⁻⁶ · K ⁻¹ , There is a disadvantage that the effects of the invention cannot be sufficiently achieved.
[0031]
An example of such a resin is a low stress epoxy resin. In addition, it is good to use the high filling type resin which 80-90% of fillers (for example, silica etc.) contain in resin.
[0032]
Moreover, it is preferable that the glass transition temperature (Tg) of mold resin is 155-185 degreeC from the viewpoint on the storage temperature and manufacturing technology of a semiconductor component.
[0033]
The transformer 6 used in the present embodiment has a size of about 11 mm in length, about 11 mm in width, and about 4 mm in height, which is larger than the other electronic components 5. It may cause the flow to be hindered.
[0034]
Therefore, in the present embodiment, each corner portion 11a of the bobbin 11 is formed in a curved surface or a chamfered shape.
[0035]
In this case, the radius or chamfering size of the curved surface of each corner portion 11a is preferably 0.2 to 2 mm, and more preferably 0.5 to 1 mm.
[0036]
If the radius of the curved surface or the chamfered size of each corner portion 11a is smaller than 0.2 mm, the flow of the resin at the time of molding is likely to be inhibited, and the corner portion 11a may be a starting point and cause a mold crack. There is an inconvenience. On the other hand, if the radius of the curved surface or the chamfer size of each corner portion 11a is larger than 2 mm, there is an inconvenience that the miniaturization of the transformer is hindered.
[0037]
By the way, as shown in FIG. 5 (a), in the case of this type of transformer 6, the opposing surfaces of the winding portions 9a and 10a of the cores 9 and 10 are generally in contact with each other. When the transformer 6 having a simple structure is used, a gap is generated in the facing surfaces of the winding portions 9a and 10a of the cores 9 and 10 due to the expansion of the resin described above during resin sealing, and the L value changes greatly. It becomes impossible.
[0038]
Therefore, as shown in FIGS. 5B and 5C, in the present embodiment, a predetermined gap G is formed in advance between the opposing surfaces 90 and 100 of the winding portions 9a and 10a of the cores 9 and 10. Like to do.
[0039]
In the present embodiment, the mold resin is applied to the gaps G of the opposed surfaces 90 and 100 of the winding portions 9a and 10a of the cores 9 and 10 at the time of molding so that the gap amount does not change due to thermal stress or the like. Try to fill.
[0040]
Here, in order to minimize the change in the L value, the size of the gap G is preferably 0.1 to 1 mm, and more preferably 0.5 to 1 mm.
[0041]
According to the present embodiment having such a configuration, since the linear expansion coefficient of the mold resin constituting the package unit 3 is 12 × 10 ⁻⁶ · K ⁻¹ or less, the mold resin in the resin sealing step Since the amount of expansion and contraction is small and fluctuations in the L value can be suppressed, the mold type converter 1 having stable characteristics can be obtained.
[0042]
Particularly in the present embodiment, since a predetermined gap G is provided between the winding portions 9a and 10a of the cores 9 and 10 of the transformer 6, a change in the distance between the magnetic cores is small during resin sealing. As a result, the fluctuation of the L value can be minimized, so that the molded converter 1 having more stable characteristics can be obtained.
[0043]
Furthermore, in this embodiment, since the corner portion 11a of the bobbin 11 of the transformer 6 is formed in a curved surface or a chamfered shape, in the vicinity of the corner portion 11a of the bobbin of the transformer 6 during resin sealing. Resin can be made to flow smoothly, thereby reducing molding defects.
[0044]
In addition, according to the present embodiment, the corner portion 11a of the bobbin 11 can be formed into a curved surface or a chamfered shape, thereby preventing mold cracks and enabling a thinner resin mold. Can be achieved.
[0045]
FIG. 6A is a front view showing an external configuration of a transformer according to another embodiment of the present invention, and FIG. 6B is a cross-sectional view showing an internal configuration of the transformer.
As shown in FIGS. 6A and 6B, in the present embodiment, a predetermined thermosetting resin 20 is provided between the winding portions 9a and 10a of the cores 9 and 10 of the transformer 6 and in the space portions 14 and 15. Thus, each member constituting the transformer 6 is fixed in advance.
[0046]
As the thermosetting resin 20 for fixing the transformer 6, it is preferable to use a thermosetting resin having a linear expansion coefficient of 10 to 12 × 10 ⁻⁶ · K ^{−1 for} the same reason as the sealing mold resin.
[0047]
As such a thermosetting resin 20, for example, various resins can be used in addition to the low stress epoxy resin used in the above-described molding.
[0048]
According to the present embodiment having such a configuration, the thermosetting resin 20 is preliminarily filled in the narrow gap portion of the transformer 6 (for example, the gap G between the winding portions 9a and 10a of the cores 9 and 10). Therefore, it is possible to easily and reliably perform resin sealing without generating voids in the cores 9 and 10 during the resin sealing process, thereby providing the mold type converter 1 having more stable characteristics. can do.
[0049]
Further, according to the present embodiment, various resins different from the mold resin can be used as the resin filling the gap G and the space portions 14 and 15 of the winding portions 9a and 10a of the cores 9 and 10 of the transformer 6. Therefore, there is an advantage that the selection range of the transformer 6 can be expanded.
[0050]
The present invention is not limited to the above-described embodiment, and various changes can be made.
For example, in the above-described embodiment, the package portion is formed by transfer molding. However, the present invention is not limited to this, and for example, the package portion may be formed by injection molding.
[0051]
Further, the corner portion of the insulating substrate can be formed into a curved surface or a chamfered shape. In that case, the fluidity of the mold resin in the resin sealing step can be improved, and molding defects can be further reduced.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a small and thin mold type converter having stable characteristics and little variation.
[Brief description of the drawings]
FIG. 1A is a plan view showing a configuration of an embodiment of a mold type converter according to the present invention. FIG. 1B is a front sectional view showing an internal configuration of the embodiment. FIG. FIG. 2 is a bottom view showing the configuration. FIG. 2 is a plan view showing the insulating substrate fixed to the lead frame in the embodiment. FIG. 3 is a schematic configuration diagram for showing the dimensional relationship of the package portion in the embodiment. 4A is a front view showing the external configuration of the transformer in the present embodiment. FIG. 4B is a side view showing the external configuration of the transformer. FIG. 5A is a general transformer core configuration. Front view shown (b): Front view showing the configuration of the core of the transformer of the present embodiment (c): Enlarged view of the portion A indicated by the alternate long and short dash line in FIG. 5 (b) FIG. 6 (a): Book The front view which shows the external appearance structure of the trans | transformer in other embodiment of invention. (B : Partial sectional view showing an internal structure of the transformer EXPLANATION OF REFERENCE NUMERALS
DESCRIPTION OF SYMBOLS 1 ... DC-DC converter 2 ... Insulation board 3 ... Package part 4, 5 ... Electronic component 6 ... Transformer 7 ... Lead frame 9, 10 ... Core (magnetic core)
11 ... Bobbin 12 ... Primary winding 13 ... Secondary winding 14, 15 ... Space 20 ... Thermosetting resin

Claims (6)

When at least transformer on one side is mounted an insulating substrate in which a predetermined electronic components are mounted on the surface of the other side to together, it said on one surface of the insulating substrate at least transformer and the other of said insulating substrate a predetermined electronic components on the surface a mold converter and a package portion for sealing,
The package part is composed of a mold resin having a linear expansion coefficient of 10 to 12 × 10 ⁻⁶ · K ⁻¹ and made of a thermosetting low stress epoxy resin,
In the transformer, a predetermined gap is provided between the magnetic cores on the primary winding side and the secondary winding side, and a linear expansion coefficient is 10 to 12 × 10 ⁻⁶ · K ⁻¹ at least between the gaps of the magnetic core. The mold type converter is characterized in that the thermosetting resin is filled and the components of the transformer are fixed in advance . 2. The mold type converter according to claim 1, wherein the transformer is filled with a thermosetting resin different from the mold resin constituting the package portion in at least a gap space between the magnetic cores . The transformer has at least claim 1 Symbol placement mold converter of the said molding resin constituting the package portion in the space of the gap between the magnetic core, characterized in that it is filled. The insulating substrate is claims 1 to 3 any one mold converter according to, characterized in that the linear expansion coefficient of 7~12 × 10 ^-6 · K ^-1. The mold type converter according to any one of claims 1 to 4, wherein a corner portion of the bobbin of the transformer is formed in a curved surface or a chamfered shape. On at least a transformer on one surface of the insulating substrate and on the other surface of the insulating substrate with respect to an insulating substrate on which at least a transformer is mounted on one surface and a predetermined electronic component is mounted on the other surface A method for manufacturing a mold type converter comprising a step of sealing a predetermined electronic component with a mold resin to form a package part,
As the mold resin of the package part, the linear expansion coefficient is 10 to 12 × 10 ^-6 ・ K ^-1 And using a thermosetting low stress epoxy resin,
As the transformer, a predetermined gap is provided between the magnetic cores on the primary winding side and the secondary winding side, and a linear expansion coefficient is 10 to 12 × 10 at least between the gaps of the magnetic core. ^-6 ・ K ^-1 A method of manufacturing a mold converter, characterized in that the transformer is filled with a thermosetting resin and the components of the transformer are fixed in advance.

Images