Electronic circuit package

Disclosed herein is an electronic circuit package includes: a substrate having a power supply pattern; an electronic component mounted on a surface of the substrate; a mold resin covering the surface of the substrate so as to embed therein the electronic component; a magnetic film formed of a composite magnetic material obtained by dispersing magnetic fillers in a thermosetting resin material, the magnetic film covering upper and side surfaces of the molding resin and an edge portion of the front surface exposed to a side surface of the substrate; and a metal film connected to the power supply pattern and covering the molding resin through the magnetic film.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an electronic circuit package and, more particularly, to an electronic circuit package provided with a composite shielding function having both an electromagnetic shielding function and a magnetic shielding function.

Description of Related Art

In recent years, an electronic device such as a smartphone is equipped with a high-performance radio communication circuit and a high-performance digital chip, and an operating frequency of a semiconductor IC used therein tends to increase. Further, adoption of an SIP (System-In Package) having a 2.5D or 3D structure, in which a plurality of semiconductor ICs are connected by a shortest wiring, is accelerated, and modularization of a power supply system is expected to accelerate. Further, an electronic circuit module having a large number of modulated electronic components (collective term of components, such as passive components (an inductor, a capacitor, a resistor, a filter, etc.), active components (a transistor, a diode, etc.), integrated circuit components (an semiconductor IC, etc.) and other components required for electronic circuit configuration) is expected to become more and more popular, and an electronic circuit package which is a collective term for the above SIP, electronic circuit module, and the like tends to be mounted in high density along with sophistication, miniaturization, and thinning of an electronic device such as a smartphone. However, this tendency poses a problem of malfunction and radio disturbance due to noise. The problem of malfunction and radio disturbance is difficult to be solved by conventional noise countermeasure techniques. Thus, recently, self-shielding of the electronic circuit package has become accelerated, and an electromagnetic shielding using a conductive paste or a plating or sputtering method has been proposed and put into practical use, and higher shielding characteristics are required in the future.

In order to realize the higher shielding characteristics, a composite shielding structure, which has both an electromagnetic shielding function and a magnetic shielding function, is proposed in recent years. In order to realize the composite shielding structure, it is necessary to form, in an electronic circuit package, an electromagnetic shielding by a conductive film (metal film) and a magnetic shielding by a magnetic film.

For example, an electronic circuit module described in JP 2010-087058A has a configuration in which a metal film and a magnetic layer are laminated in this order on a surface of a molding resin. Further, an electronic circuit module described in JP 2011-077430A prevents failures such as cracks occurring when a circuit board is cut by reducing an exposure ratio of a copper foil (inner layer pattern) exposed to the side surface of a substrate.

However, according to the present inventors' study, it is found that the configuration of JP 2010-087058A in which a metal film and a magnetic layer are laminated in this order on a surface of a molding resin cannot obtain sufficient shielding effect as an electronic circuit package for mobile communication device that is increasingly required to achieve a high shielding property in the future. Further, in the configuration of JP 2011-077430A, cracks at cutting can be prevented, but interface peeling or cracks may occur during reflow. That is, during reflow, moisture contained in a substrate or molding resin is vaporized and expanded to generate stress, and a solder used for joining electronic components is re-melted and volume-expanded to generate stress. Such stress causes generation of peeling and cracks at various interfaces at a substrate side surface part.

SUMMARY

The object of the present invention is therefore to provide an electronic circuit package capable of achieving both high composite shielding effect and high reliability during reflow.

An electronic circuit package according to the present invention includes: a substrate having a power supply pattern; an electronic component mounted on a front surface of the substrate; a molding resin that covers the front surface of the substrate so as to embed the electronic component therein; a magnetic film formed of a composite magnetic material obtained by dispersing magnetic fillers in a thermosetting resin material, the magnetic film covering upper and side surfaces of the molding resin and an edge of the front surface exposed to a side surface of the substrate; and a metal film connected to the power supply pattern and covering the molding resin with an intervention of the magnetic film.

According to the present invention, the magnetic film and the metal film are formed in this order on the upper surface of the molding resin, so that high composite shielding characteristics can be obtained. In addition, the magnetic film formed of a composite magnetic material covers the edge of the substrate front surface, so that moisture expanded during reflow becomes movable through the thermosetting resin material, and stress is alleviated. Therefore it becomes possible to prevent interface peeling and cracks at the edge.

In the present invention, it is preferable that the substrate side surface includes an exposed portion at which the power supply pattern is exposed and the metal film is connected to the power supply pattern by covering the exposed portion without an intervention of the magnetic film. With this configuration, the power supply pattern exposed to the substrate side surface is not covered with the magnetic film, thereby making it possible to easily connect the metal film to the power supply pattern.

In the present invention, it is preferable that the substrate further has a solder resist formed on the front surface and the magnetic film covers the interface between the solder resist and the front surface of the substrate which is exposed to the side surface of the substrate. With this configuration, peeling and cracks at the interface between the solder resist and the substrate, and peeling of the metal film can be prevented.

In this case, it is preferable that the substrate further has a first wiring pattern formed on the front surface and the magnetic film covers the interface between the first wiring pattern and the front surface of the substrate which is exposed to the side surface of the substrate. With this configuration, peeling and cracks at the interface between the first wiring pattern and the substrate, and peeling of the metal film can be prevented.

Further, in this case, the magnetic film preferably further covers the interface between the solder resist and the first wiring pattern which is exposed to the side surface of the substrate. With this configuration, peeling and cracks at the interface between the solder resist and the first wiring pattern, and peeling of the metal film can be prevented.

In the present invention, it is preferable that the substrate further has a second wiring pattern embedded therein and the magnetic film further covers the interface between the second wiring pattern and the substrate which is exposed to the side surface of the substrate. With this configuration, peeling and cracks at the interface between the second wiring pattern and the substrate, and peeling of the metal film can be prevented.

In the present invention, the magnetic filler is preferably formed of ferrite or soft magnetic metal and, more preferably, the surface of the magnetic filler is insulation-coated.

In the present invention, it is preferable that the metal film is mainly composed of at least one metal selected from a group consisting of Au, Ag, Cu, and Al and that a surface of the metal film is covered with an antioxidant film.

As described above, according to the present invention, it becomes possible to achieve both high composite shielding effect and high reliability during reflow.

DETAILED DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG. 1is a cross-sectional view illustrating a configuration of an electronic circuit package15A according to the first embodiment of the present invention.

As illustrated inFIG. 1, the electronic circuit package15A according to the present embodiment includes a substrate20, a plurality of electronic components31and32mounted on the substrate20, a mold resin40covering a front surface21of the substrate20so as to embed the electronic components31and32, a magnetic film50covering the mold resin40, and a metal film60covering the magnetic film50and the mold resin40.

Although the type of the electronic circuit package15A according to the present embodiment is not especially limited, examples thereof include a high-frequency module handling a high-frequency signal, a power supply module performing power supply control, an SIP (System-In-Package) having a 2.5D structure or a 3D structure, and a semiconductor package for radio communication or digital circuit. Although only two electronic components31and32are illustrated inFIG. 1, more electronic components are incorporated actually.

The substrate20has a double-sided and multilayer wiring structure in which a large number of wirings are embedded therein and may be any type of substrate including: a thermosetting resin based organic substrate such as an FR-4, an FR-5, a BT, a cyanate ester, a phenol, or an imide; a thermoplastic resin based organic substrate such as a liquid crystal polymer; an LTCC substrate; an HTCC substrate; and a flexible substrate. In the present embodiment, the substrate20has a four-layer structure including wiring layers formed on the front surface21and a back surface22and two wiring layers embedded therein. On the front surface21of the substrate20, a plural of land patterns23are formed. Land patterns23are an internal electrode for connecting to the electronic components31and32. The land patterns23and each of the electronic components31and32are electrically and mechanically connected to each other through a respective solder24(or a conductive paste). For example, the electronic component31is a semiconductor chip such as a controller, and electronic component32is a passive component such as a capacitor or a coil. Some electronic components (e.g., thinned semiconductor chip) may be embedded in the substrate20.

The land patterns23are connected to external terminals26formed on the back surface22of the substrate20through internal wirings25formed inside the substrate20. Upon actual use, the electronic circuit package15A is mounted on an unillustrated mother board, and land patterns on the mother board and the external terminals26of the electronic circuit package15A are electrically connected. A material for a conductor forming the land patterns23, internal wirings25, and external terminals26may be a metal such as copper, silver, gold, nickel, chrome, aluminum, palladium, indium, or a metal alloy thereof or may be a conductive material using resin or glass as a binder; however, when the substrate20is an organic substrate or a flexible substrate, copper or silver is preferably used in terms of cost and/or conductivity. Methods such as printing, plating, foil lamination, sputtering, vapor deposition, and inkjet can be used to form the above conductive materials.

The internal wirings25to which G is added at the end of its sign inFIG. 1are power supply patterns. The power supply patterns25G are typically ground patterns to which a ground potential is to be applied; however, it is not limited to the ground patterns as long as the power supply patterns25G are a pattern to which a fixed potential is to be applied.

The mold resin40covers the surface21of the substrate20so as to embed therein the electronic components31and32. As a material for the mold resin40, a material based on a thermosetting material or a thermoplastic material and blended with fillers for adjusting a thermal expansion coefficient can be used.

A top surface41and a side surface42of the mold resin40are covered with the magnetic film50. Although not particularly limited, it is preferable that the mold resin40and magnetic film50directly contact each other without intervention of an adhesive or the like. The magnetic film50is a film composed of a composite magnetic material in which magnetic fillers are dispersed in a thermosetting resin material and serves as a magnetic shield.

As a thermosetting resin material used for the magnetic film50, an epoxy resin, a phenol resin, a silicone resin, a diallyl phthalate resin, a polyimide resin, an urethane resin, and the like may be used, and the magnetic film50can be formed by using a thick-film formation method such as a printing method, a molding method, a slit nozzle coating method, a spray method, a dispensing method, an injection method, a transfer method, a compression molding method, or a lamination method using an uncured sheet-like resin. Using the thermosetting resin material, reliability required for electronic circuit packages such as heat resistance, insulation performance, impact resistance, falling resistance, and the like can be enhanced.

As the magnetic filler, a ferrite or a soft magnetic metal is preferably used, and a soft magnetic metal having a high bulk permeability is more preferably used. As the ferrite or soft magnetic metal, one or two or more metals selected from a group consisting of Fe, Ni, Zn, Mn, Co, Cr, Mg, Al, and Si and oxides thereof may be exemplified. As specific examples, a ferrite such as Ni—Zn ferrite, Mn—Zn ferrite, Ni—Cu—Zn ferrite, a permalloy (Fe—Ni alloy), a super permalloy (Fe—Ni—Mo alloy), a sendust (Fe—Si—Al alloy), an Fe—Si alloy, an Fe—Co alloy, an Fe—Cr alloy, an Fe—Cr—Si alloy, an Fe—Ni—Co alloy, and Fe, and the like may be exemplified. The shape of the magnetic filler is not especially limited; however, it may be formed into a spherical shape for a high filling level, and fillers having a plurality of particle size distribution may be blended or combined for a densest filling structure. In order to maximize a shield effect by a permeability real component and a thermal conversion effect of a loss by a permeability imaginary component, it is more preferable to form by making flat powder having an aspect ratio of 5 or more orientate.

It is preferable that the surface of the magnetic filler is insulation-coated by an oxide of a metal such as Si, Al, Ti, or Mg, or an organic material for enhancing fluidity, adhesion, and insulation performance. For the insulation coating, an oxide film may be formed by coating a thermosetting material on the surface of the magnetic filler or dehydration reaction of a metal alkoxide, formation of a silicon oxide coating film is most preferable. It is more preferable to apply an organofunctional coupling treatment on the formed coating film.

The composite magnetic material can be formed on the top surface41and side surface42of the mold resin using a known method such as a printing method, a molding method, a slit nozzle coating method, a spray method, a dispensing method, or a lamination method using an uncured sheet-like resin.

The top surface51and side surface52of the magnetic film50, and a part of the side surface27of the substrate20are covered with the metal film60. The metal film60serves as an electromagnetic shielding and is preferably mainly composed of at least one metal selected from a group consisting of Au, Ag, Cu, and Al. The metal film60preferably has a resistance as low as possible and it is most preferable to use Cu in terms of cost and the like. An outer surface of the metal film60is preferably covered with an anticorrosive metal such as SUS, Ni, Cr, Ti, or brass or an antioxidant coating made of a resin such as an epoxy, a phenol, an imide, an urethane, or a silicone. The reason for this is that the metal film60undergoes oxidative deterioration by an external environment such as heat or humidity; and, therefore, the aforementioned treatment is preferable to suppress and prevent the oxidative deterioration. A formation method for the metal film60may be appropriately selected from known methods, such as a sputtering method, a vapor-deposition method, an electroless plating method, an electrolytic plating method. Before formation of the metal film60, pretreatment for enhancing adhesion, such as plasma treatment, coupling treatment, blast treatment, or etching treatment, may be performed. As a base of the metal film60, a high adhesion metal film such as a titanium film, a chromium film, or an SUS film may be formed thinly in advance.

In the present embodiment, the side surface27of the substrate20is formed stepwise. Specifically, a side surface lower portion27bprotrudes from a side surface upper portion27a. The side surface upper portion27aand a step portion27care covered with the magnetic film50, and the side surface lower portion27bis covered with the metal film60without being covered with the magnetic film50. Thus, in the present embodiment, the edge portion of the front surface21exposed to the side surface27of the substrate20is covered with the magnetic film50. In this embodiment, the side surface52of the magnetic film50and the side surface lower portion27bof the substrate20form the same plane.

As illustrated inFIG. 1, the power supply patterns25G are exposed to the side surface lower portion27bof the substrate20. The metal film60is connected to the power supply pattern25G by covering the side surface lower portion27bof the substrate20.

Although not especially limited, it is desirable that a resistance value at an interface between the metal film60and the magnetic film50is equal to or larger than 106Ω. According to this configuration, it becomes possible to prevent deterioration in the magnetic characteristics of the magnetic film50due to inflow of an eddy current because the eddy current generated by electromagnetic wave noise entering the metal film60hardly flows in the magnetic film50. The resistance value at the interface between the metal film60and the magnetic film50refers to a surface resistance of the magnetic film50when the metal film60and magnetic film50directly contact each other and to a surface resistance of an insulating film when the insulating film is present between the metal film60and the magnetic film50.

As methods in order to make a resistance value at an interface between the metal film60and the magnetic film50equal to or higher than 106Ω, a method using a material having a sufficiently high surface resistance as the material for the magnetic film50or a method forming a thin insulating material on the top surface51of the magnetic film50are exemplified.FIG. 2is a cross-sectional view illustrating a configuration of an electronic circuit package15B according to a modification. The electronic circuit package15B differs from the electronic circuit package15A shown inFIG. 1in that a thin insulating film70is interposed between the top surface51of the magnetic film50and the metal film60. By interposing the insulating film70, it becomes possible to make a resistance value at an interface between the metal film60and the magnetic film50equal to or higher than 106Ω even when a material having a comparatively low resistance value is used as the material for the magnetic film50, thereby making it possible to prevent deterioration in magnetic characteristics due to an eddy current. Although not shown in the drawings, the thin insulating film70may be interposed between the side surface52of the magnetic film50and the metal film60.

As described above, in the electronic circuit package15A (and15B) according to the present embodiment, the magnetic film50and metal film60are laminated in this order on the top surface41and side surface42of the mold resin40. With this configuration, as compared with a case where the magnetic film50and metal film60are laminated in the reverse order, electromagnetic noise radiated from the electronic components31and32can be shielded more effectively. This is because the electromagnetic wave noise radiated from the electronic components31and32is partially absorbed when it passes through the magnetic film50, and the remaining electromagnetic wave noise that has not been absorbed is partially reflected by the metal film60and passes through the magnetic film50once again. In this manner, the magnetic film50acts on the incident electromagnetic wave noise twice, thereby effectively shielding the electromagnetic wave noise radiated from the electronic components31and32.

Further, in the present embodiment, since the side surface lower portion27bof the substrate20is covered with the metal film60without being covered with the magnetic film50, the power supply pattern25G exposed to this portion can be connected to the metal film60. Thus, even though the magnetic film50and the metal film60are laminated in this order, the metal film60can be easily connected to the power supply pattern25G.

Further, in the present embodiment, the edge portion of the front surface21exposed to the side surface27of the substrate20is covered with the magnetic film50formed of the composite magnetic material, so that product reliability can be enhanced. That is, during reflow, moisture contained in the substrate20or molding resin40is vaporized and expanded to generate stress, and a solder used for joining electronic components is re-melted and volume-expanded to generate stress. Such stress concentrates on various interfaces exposed to the side surface27of the substrate20, which may cause peeling at the interfaces.

FIGS. 3 to 6are schematic enlarged views of the electronic circuit package15A of the present embodiment and illustrate different cross sections respectively.

In the cross section illustrated inFIG. 3, the edge portion of the front surface21exposed to the side surface27of the substrate20is directly covered with the molding resin40. In such a cross section, moisture vaporized and expanded during reflow concentrates on an interface S1between the front surface21of the substrate20and the molding resin40, causing stress peeling the edge portion of the interface S1to act. However, in the present embodiment, the edge portion of the interface S1is covered with the magnetic film50formed of the composite magnetic material, so that moisture reaching the edge portion of the interface S1becomes movable through the magnetic film50, thus preventing peeling at the interface S1.

In the cross section illustrated inFIG. 4, the side surface of a solder resist SR is exposed from the molding resin40, and thus the edge portion of the front surface21exposed to the side surface27of the substrate20contacts the solder resist SR. The solder resist SR is an insulating layer formed on the front surface21of the substrate20and covers a wiring pattern28formed on the front surface21of the substrate20. If the solder resist SR like this exists, peeling and/or peeing of the metal film60are likely to occur at an interface S2between the solder resist SR and the front surface21of the substrate20and/or an interface S3between the solder resist SR and the molding resin40. However, in the present embodiment, the edge portions of the interfaces S2and S3are each covered with the magnetic film50formed of the composite magnetic material, so that moisture reaching the edge portions of the interfaces S2and S3becomes movable through the magnetic film50, thus preventing peeling at the interfaces S2and S3and peeling of the metal film60.

In the cross section illustrated inFIG. 5, the side surface of the wiring pattern28is exposed from the molding resin40, and thus the edge portion of the front surface21exposed to the side surface27of the substrate20contacts the wiring pattern28. If the wiring pattern28like this exists, peeling and/or peeing of the metal film60are likely to occur at an interface S4between the wiring pattern28and the front surface21of the substrate20and an interface S5between the wiring pattern28and the molding resin40. However, in the present embodiment, the edge portions of the interfaces S4and S5are each covered with the magnetic film50formed of the composite magnetic material, so that moisture reaching the edge portions of the interfaces S4and S5becomes movable through the magnetic film50, thus preventing peeling at the interfaces S4and S5and peeling of the metal film60.

In the cross section illustrated inFIG. 6, both the side surface of the solder resist SR and the side surface of the wiring pattern28are exposed from the molding resin40. If the solder resist SR and wiring pattern28like this exists, peeling and/or peeing of the metal film60are likely to occur at the interfaces S3to S5. However, in the present embodiment, the edge portions of the interfaces S3to S5are each covered with the magnetic film50formed of the composite magnetic material, so that moisture reaching the edge portions of the interfaces S3to S5becomes movable through the magnetic film50, thus preventing peeling at the interfaces S3to S5and peeling of the metal film60.

As described above, in the present embodiment, the edge portions of the front surface21exposed to the side surface27of the substrate20is covered with the magnetic film50formed of the composite magnetic material, so that peeling at the interfaces S1to S5and peeling of the metal film60which may occur during reflow are prevented, whereby reliability is enhanced.

Further, in case that the magnetic film50is directly formed on the upper surface41and side surface42of the molding resin40, an adhesive or the like is not interposed between the molding resin40and the magnetic film50, which is advantageous in reduction in product height.

The following describes a manufacturing method for the electronic circuit package15A according to the present embodiment.

FIGS. 7 to 11are process views for explaining a manufacturing method for the electronic circuit package15A.

As illustrated inFIG. 7, an assembly substrate20A having a multilayer wiring structure is prepared. A plurality of land patterns23are formed on the front surface21of the assembly substrate20A, and a plurality of external terminals26are formed on the back surface22of the assembly substrate20A. Further, a plurality of the internal wirings25including the power supply patterns25G are formed in an inner layer of the assembly substrate20A. A dashed line a inFIG. 7denotes a part to be cut in a subsequent dicing process. As illustrated inFIG. 7, the power supply patterns25G are provided at a position overlapping the dashed line a in a plan view.

Then, as illustrated inFIG. 7, the plurality of electronic components31and32are mounted on the front surface21of the assembly substrate20A so as to be connected to the land patterns23. Specifically, the solder24is provided on the land pattern23, followed by mounting of the electronic components31and32and by reflowing, whereby the electronic components31and32are connected to the land patterns23.

Then, as illustrated inFIG. 8, the front surface21of the assembly substrate20A is covered with the mold resin40so as to embed the electronic components31and32in the mold resin40. As the formation method for the mold resin40, compression, injection, print, dispense, nozzle coating process, and the like can be used.

Subsequently, as illustrated inFIG. 9, a groove44having a width W1is formed along the dashed line a denoting a dicing position. The groove44is formed so as to almost completely cut the molding resin40and so as not to reach the internal wiring25formed inside the substrate20. As a result, the side surface42of the molding resin40and the side surface upper portion27aand step portion27cof the substrate20are exposed inside the groove44.

Subsequently, as illustrated inFIG. 10, the magnetic film50is formed so as to fill the groove44. In this case, in order to enhance adhesion between the molding resin40and the magnetic film50, the upper surface41of the molding resin40may be subjected to blasting or etching to form a physical irregularity thereon, may be subjected to surface modification by means of plasma or short wavelength UV, or may be subjected to organofunctional coupling treatment.

Although it is not essential to completely fill the groove44with the magnetic film50, the magnetic film50needs to have a certain film thickness to fill the groove44with the magnetic film50. As the formation method for the magnetic film50, a thick-film formation method such as a printing method, a molding method, a slit nozzle coating method, a spray method, a dispensing method, an injection method, a transfer method, a compression molding method, or a lamination method using an uncured sheet-like resin can be used. When the magnetic film50is formed by using the printing method, slit nozzle coating method, spraying method, dispensing method, and the like, the viscosity of the composite magnetic material is preferably controlled as needed. The viscosity control may be made by diluting the composite magnetic material with one or two or more solvents having a boiling point of 50° C. to 300° C. The thermosetting material mainly consists of a main agent, a curing agent, and a curing accelerator; however, two or more kinds of main agent or curing agent may be blended according to required characteristics. Further, solvents may be mixed and a coupling agent for enhancing adhesion and fluidity, a fire retardant for flame retardancy, a dye and a pigment for coloration, a non-reactive resin material for imparting flexibility, and a non-magnetic filler for adjusting a thermal expansion coefficient may be blended or combined. The materials may be kneaded or dispersed by a known means such as a kneader, a mixer, a vacuum defoaming stirring machine, or a three-roll mill.

If the insulating film70is interposed between the magnetic film50and the metal film60as in the modification illustrated inFIG. 2, after formation of the magnetic film50, an insulating material such as a thermosetting material, a heat-resistant thermoplastic material, an Si oxide, a low-melting point glass may be thinly formed on the top surface51of the magnetic film50.

Then, as illustrated inFIG. 11, the assembly substrate20A is cut by forming a groove45having a width W2along the dashed line a to divide the assembly substrate20A into individual substrates20. At this time, the width W2of the groove45needs to be thinner than the width W1of the groove44. As a result, the substrates20are individuated while the magnetic film50formed inside the groove44is left. In the present embodiment, because the power supply patterns25G pass the dashed line a as a dicing position, the power supply patterns25G are exposed from the side surface lower portion27bof the substrate20when the assembly substrate20A is cut along the dashed line a.

Then, the metal film60is formed so as to cover the top surface51and side surface52of the magnetic film50, and the side surface lower portion27bof the substrate20, whereby the electronic circuit package15A according to the present embodiment is completed. As a formation method for the metal film60, a sputtering method, a vapor-deposition method, an electroless plating method, and an electrolytic plating method can be used. Before formation of the metal film60, pretreatment for enhancing adhesion, such as plasma treatment, coupling treatment, blast treatment, or etching treatment, may be performed. As a base of the metal film60, a high adhesion metal film such as a titanium or a chromium may be formed thinly in advance.

As described above, in the manufacturing method for the electronic circuit package15A according to the present embodiment, the two grooves44and45having different widths are sequentially formed, so that it is possible to cover the side surface42of the molding resin40with the magnetic film50and to easily connect the metal film60to the power supply pattern25G without requiring complicated processes. Further, direct formation of the magnetic film50on the upper surface41and side surface42of the molding resin40eliminates the need of using an adhesive or the like, which is advantageous in height reduction.

FIG. 12is a cross-sectional view illustrating the configuration of an electronic circuit package15C according to a modification.

The electronic circuit package15C illustrated inFIG. 12differs from the electronic circuit package15A illustrated inFIG. 1in that the magnetic film50covers a wiring pattern29exposed to the side surface27of the substrate20. Other configurations are the same as those of the electronic circuit package15A, so the same reference numerals are given to the same elements, and overlapping description will be omitted.

The wiring pattern29contacting the magnetic film50may be a power supply pattern such as a ground or a signal wiring. However, in case that a material having high conductivity is used as the material of the magnetic film50, the wiring pattern29contacting the magnetic film50needs to be the wiring pattern29which is applied with the same potential as that of the power supply pattern25G that the metal film60contacts. The wiring pattern29is exposed to the side surface upper portion27aof the substrate20, and accordingly the interface between the base material of the substrate20and the wiring pattern29appears at the side surface upper portion27aof the substrate20.

With this configuration, it is possible to prevent not only the peeling between the substrate and the solder resist or between the mold material and the solder resist, crack in the solder resist, mold material, or the substrate, and swelling, peeling, or the like in the metal film60formed as an electromagnetic shield film, but also a peeling in the interface between the substrate20and the wiring pattern29due to expansion of the moisture, thus ensuring higher reliability. Also in this case, by using the composite magnetic material as the material for the magnetic film50, peeling of the wiring pattern29can be prevented more effectively.

The electronic circuit package15C according to the present embodiment can be manufactured by forming the groove44deeper in the process ofFIG. 9.

In this case as well, in case that a material having a comparatively low resistance value is used as the material of the magnetic film50, it is preferable to interpose the thin insulating film70between the upper surface51(and side surface52) of the magnetic film50and the metal film60as in an electronic circuit package15D according to a modification shown inFIG. 13.

Second Embodiment

FIG. 14is a cross-sectional view illustrating the configuration of an electronic circuit package16A according to a second embodiment of the present invention.

As illustrated inFIG. 14, an electronic circuit package16A according to the present embodiment is the same as the electronic circuit package15A according to the first embodiment illustrated inFIG. 1except for the shapes of the substrate20and metal film60. Thus, the same reference numerals are given to the same elements, and overlapping description will be omitted.

In the present embodiment, the side surface27of the substrate20has a three-step form. Specifically, the side surface lower portion27bprotrudes from the side surface upper portion27a, and a side surface lowermost portion27dprotrudes from the side surface lower portion27b. The magnetic film50covers the side surface upper portion27aand step portion27cof the substrate20, and the metal film60is provided so as to cover the side surface lower portion27band a step portion27e. The side surface lowermost portion27dis not covered with the metal film60. In the present embodiment as well, the power supply pattern25G is exposed to the side surface lower portion27bof the substrate20, so that the metal film60is connected to the power supply pattern25G through the side surface lower portion27b. In case that a material having a comparatively low resistance value is used as the material of the magnetic film50, it is preferable to interpose the thin insulating film70between the upper surface51(and side surface52) of the magnetic film50and the metal film60as in an electronic circuit package16B according to a modification shown inFIG. 15.

FIGS. 16 and 17are process views for explaining a manufacturing method for the electronic circuit package16A.

First, the magnetic film50is formed on the upper surface41of the molding resin40and on the inside of the groove44according to the method described usingFIGS. 7 to 10. Then, as illustrated inFIG. 16, a groove46having a width W3is formed along the dashed line a denoting the dicing position. The groove46is formed to have such a depth that the groove46completely cuts the molding resin40and does not completely cut the substrate20. The width W3is made smaller than the width W1of the groove44illustrated inFIG. 9. As a result, the side surface52of the magnetic film50and the side surface lower portion27band step portion27eof the substrate20are exposed inside the groove46. The groove46needs to be formed to have such a depth that the power supply pattern25G is exposed at least from the side surface lower portion27b.

Subsequently, as illustrated inFIG. 17, the metal film60is formed by using a sputtering method, a vapor-deposition method, an electroless plating method, or an electrolytic plating method. As a result, regarding the metal film60, the upper surface51of the magnetic film50and the inside of the groove46are covered with the metal film60. At this time, the power supply pattern25G exposed to the side surface lower portion27bof the substrate20is connected to the metal film60.

Then, the assembly substrate20A is cut along the dashed line a to individuate the substrate20, whereby the electronic circuit package16A according to the present embodiment is completed.

As described above, according to the manufacturing method for the electronic circuit package16A of the present embodiment, the power supply pattern25G is exposed through the groove46which does not completely separate the substrate20, so that the metal film60can be formed before the substrate20is individuated, thus facilitating formation of the metal film60.

FIG. 18is a cross-sectional view illustrating the configuration of an electronic circuit package16C according to a modification.

The electronic circuit package16C illustrated in FIG. differs from the electronic circuit package16A illustrated inFIG. 14in that the magnetic film50covers the wiring pattern29exposed to the side surface upper portion27aof the substrate20. Other configurations are the same as those of the electronic circuit package16A, so the same reference numerals are given to the same elements, and overlapping description will be omitted.

As in the electronic circuit package15C illustrated inFIG. 12, the wiring pattern29contacting the magnetic film50may be a power supply pattern such as a ground or a signal wiring. However, in case that a material having high conductivity is used as the material of the magnetic film50, the wiring pattern29contacting the magnetic film50needs to be the wiring pattern29which is applied with the same potential as that of the power supply pattern25G that the metal film60contacts. The wiring pattern29is exposed to the side surface upper portion27aof the substrate20, and accordingly the interface between the base material of the substrate20and wiring pattern29appears at the side surface upper portion27aof the substrate20.

With the above configuration, peeling of the solder resist and cracks therein can be prevented and, in addition, peeling at the interface between the substrate20and the wiring pattern29and peeling of the metal film60due to expansion of the moisture can be prevented, making it possible to ensure higher reliability.

In this case as well, in case that a material having a comparatively low resistance value is used as the material of the magnetic film50, it is preferable to interpose the thin insulating film70between the upper surface51(and side surface52) of the magnetic film50and the metal film60as in an electronic circuit package16D according to a modification shown inFIG. 19.

While the preferred embodiments of the present invention have been described, the present invention is not limited thereto. It is needless to say that various modifications may be made without departing from the gist of the invention and all of the modifications thereof are included in the scope of the present invention.

EXAMPLES

A sample having the same structure as that of the electronic circuit package15C ofFIG. 12was actually produced. As the assembly substrate20A, a multilayer resin substrate having a plane size of 50 mm×50 mm and a thickness of 0.3 mm.

As a Fe-based spherical magnetic filler, AKT 4.5Si-5.0Cr (D50=30 μm) manufactured by Mitsubishi Steel Mfg. Co., Ltd. and carbonyl iron powder (D50=6 μm) manufactured by BASF Corporation were used, and a SiO2coating was applied by the hydrolysis of metal alkoxide. Then, AKT 4.5Si-5.0Cr and carbonyl iron powder were weighed in a weight ratio of 8:2 and added to a thermosetting resin at 90 wt %. The thermosetting resin and a solvent used were as follows: HP-7200H (dicyclopentadiene type epoxy resin) manufactured by DIC. Co., Ltd. as a main agent; TD2093 (phenol novolac type epoxy resin) manufactured by DIC. Co., Ltd. as a curing agent; wt % of C11Z-CN (imidazole) manufactured by Shikoku Chemicals Corporation relative to the main agent, as a curing accelerator; and butyl carbitol acetate as the solvent. Then, the above resin materials were blended together, followed by kneading and stirring by a vacuum defoaming stirring machine. After that, butylcarbitol acetate was appropriately added so that the viscosity at 10 rpm is 50 Pa·S, followed by kneading and stirring again by the vacuum defoaming stirring machine, whereby a composite magnetic material paste was obtained.

Then, after the groove44ofFIG. 9was formed, the above composite magnetic material paste was printed by screen printing, followed by drying and heat-cured at 180° C. for 60 minutes. As a result, the structure ofFIG. 10was obtained. Thereafter, with the groove45, the assembly substrate20A was individuated into a plane size of 8.5 mm×8.5 mm, and the metal film60was formed on the entire surface of the substrate20except for the back surface22thereof. For the metal film60, a laminated film of Cu (film thickness of 1 μm) and Ni (film thickness of 2 μm) was formed by electroless plating.

As a comparative example, a sample was produced by removing the magnetic film50from the sample of the example. The sample of the comparative example was produced as follows: the processes ofFIGS. 7 and 8were performed; the assembly substrate20A was cut along the dashed line a into individual substrates20; and the metal film60was formed by electroless plating.

Then, water absorption re flow test was performed to each sample. The water absorption test was carried out by performing pretreatment under the conditions of JEDEC MSL3 (60° C., 60% RH, 60 hours), MSL2a (60° C., 60% RH, 120 hours), and MSL1 (85° C., 85% RH, 168 hours) and by making the sample pass through a reflow furnace of 260° C. three times. Then, after the appearance was checked using a microscope, the cross section of the substrate20was exposed by grinding, followed by observation of the cross section using a SEM for checking the number of failures such as peeling or cracks and a failure mode. The number of samples in each condition was22. The results are shown in Table 1.

As shown in Table 1, in the comparative example, the sample subjected to pretreatment under the MSL2a has a 9% failure rate, and sample subjected to pretreatment under the MSL1 has a 32% failure rate. As for the failure mode, swelling of the metal film60is observed through a microscope, and peeling of the metal film60is observed under SEM. On the other hand, in the example, samples subjected to pretreatment under any conditions have no failure. Thus, it is found that internal stress is alleviated by covering a part of the side surface27of the substrate20with the magnetic film50to enhance adhesion of the land pattern23and/or internal wiring25.