Method for manufacturing component-embedded substrate

A component-embedded substrate includes a component embedded in an uncured resin layer of a second layer. After curing the resin layer, a hole passing through the second layer in the vertical direction is formed. The hole is filled with an electroconductive paste to form a second interlayer connection conductor. A first in-plane conductor including a plurality of lands, a first layer, and the second layer are respectively stacked in that order and pressed to join together, and the first layer is heated to form an integrated structure. A method for manufacturing the component-embedded substrate can form an interlayer connection conductor having a small diameter and high straightness and thus can achieve a miniaturized component-embedded substrate including interlayer connection conductors at a narrow pitch.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a component embedded substrate and a method for manufacturing a component-embedded substrate made of a resin in which a component is embedded.

2. Description of the Related Art

As electronic apparatuses become smaller and more sophisticated, various component-embedded substrates have been proposed which closely contain electronic components, such as capacitors, chip resistors, chip coils, and ICs, with high functionality.

Such component-embedded substrates include a component-embedded layer that is prepared by mounting components on, for example, a multilayer substrate (multilayer printed circuit board), a wired transfer plate, and embedding the components in a resin. In the component-embedded layer, a hole, through which in-plane conductors disposed on the upper and lower surfaces will be electrically connected, is formed by a laser or the like. In order to give electroconductivity to the hole, the inter wall of the hole is plated or the hole is filled with an electroconductive paste. Thus, an interlayer connection conductor is formed such that the upper and lower in-plane conductors are electrically connected to each other.

The hole in which the interlayer connection conductor is formed may be called a “through-hole” or a “blind hole”, depending on how the hole is formed.

The through-hole is formed by irradiating the component-embedded layer with laser light from above with no in-plane conductor disposed on the upper or the lower surface of the component-embedded layer (see, for example, Japanese Unexamined Patent Application Publication No. 11-220262 (paragraphs [0056]-[0064], FIG. 2, etc.)). In Japanese Unexamined Patent Application Publication No. 11-220262, the through-hole is filled with an electroconductive paste and then a resin embedding the components is cured with the in-plane conductors disposed on the upper and lower surfaces. Thus, the component-embedded layer having the through-hole and the in-plane conductors are integrated with one another.

The blind hole is formed by irradiating the component-embedded layer with laser light from above with the in-plane conductor disposed on the lower surface. For example, components and an in-plane conductor are disposed in an uncured resin, followed by curing the resin to integrate the components and the in-plane conductor. Then, a blind hole is formed in the component-embedded layer and filled with an electroconductive paste.

When a through-hole is formed as described in Japanese Unexamined Patent Application Publication No. 11-220262, the through-hole is formed in an uncured resin, then the in-plane conductors and the component-embedded layer are integrated, and the resin is cured. Since the resin shrinks when being cured, the straightness of the through-hole is reduced which causes displacement from the land of the in-plane conductor.

The blind hole is formed with a land of the in-plane conductor used as the bottom. When laser light is irradiated to form a blind hole, the laser light is reflected from the land and the reflected laser light cuts the resin to form the blind hole. Consequently, the diameter of the hole becomes large. Also, in order to prevent damage to the land, only weak laser light should be irradiated. This makes the shape of the hole tapered (i.e., having a trapezoidal section). When the hole in this state is plated from the upper surface of the component-embedded layer, the plating layer needs to extend to and cover the bottom of the blind hole, or when an electroconductive paste is injected from the upper surface of the component-embedded layer, the paste needs to reach the bottom of the blind hole. In order to cover the bottom of the blind hole as above, the diameter of the hole (diameter of the upper open end of the hole) must be increased. Consequently, the lands for blind holes cannot be arranged with a narrow pitch, and thus the miniaturization of the component-embedded substrate is prevented.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide both a method for manufacturing a component-embedded substrate that provides a highly straight interlayer connection conductor having a small diameter and thus can achieve a miniaturized substrate with high reliability, and provide such a component-embedded substrate.

Accordingly, a method for manufacturing a component-embedded substrate according to a preferred embodiment of the present invention includes a step of forming a first in-plane conductor including a plurality of lands, a step of forming a first interlayer connection conductor in a first layer made of an uncured resin at a position corresponding to a specific one of the lands, a step of embedding a component in a second layer made of an uncured resin and subsequently curing the second layer, a step of forming a second interlayer connection conductor passing through the cured second layer from the upper surface to the lower surface at a position corresponding to the first interlayer connection conductor, and a step of stacking the first in-plane conductor, the first layer, and the second layer in that respective order and subsequently curing the first layer, thereby integrating the first in-plane conductor, the first layer, and the second layer. Thus, the first in-plane conductor, the first interlayer connection conductor, and the second interlayer connection conductor are electrically connected from one to another.

A method for manufacturing a component-embedded substrate according to a preferred embodiment of the present invention includes a step of forming a first interlayer connection conductor in a first layer made of an uncured resin having a first in-plane conductor including a plurality of lands. The first interlayer connection conductor has a bottom defined by a specific one of the lands. The method also includes the step of embedding a component in a second layer made from an uncured resin and subsequently curing the second layer, a step of forming a second interlayer connection conductor passing through the second layer from the upper surface to the lower surface at a position corresponding to the first interlayer connection conductor, and a step of stacking the first layer and the second layer in that order and subsequently curing the first layer, thereby integrating the first layer and the second layer. Thus, the first in-plane conductor, the first interlayer connection conductor, and the second interlayer connection conductor are electrically connected to one to another.

The method for manufacturing a component-embedded substrate according to a preferred embodiment of the present invention preferably includes a step of forming a second in-plane conductor electrically connected to the second interlayer connection conductor on the upper surface of the second layer.

A method for manufacturing a component-embedded substrate according to a preferred embodiment of the present invention, may preferably further include a step of preparing an uncured third layer having a second in-plane conductor on one surface thereof and disposing the third layer on the second layer, thereby electrically connecting the second in-plane conductor to the second interlayer connection conductor.

A method for manufacturing a component-embedded substrate according to a preferred embodiment of the present invention may preferably further include a step of exposing the component after the step of embedding the component in the uncured second layer and curing the second layer.

In a method for manufacturing a component-embedded substrate according to a preferred embodiment of the present invention, the component may be embedded in the uncured second layer after the component is mounted on an electrode formed on a transfer plate, and the transfer plate is removed from the second layer after the second layer is cured.

In a method for manufacturing a component-embedded substrate according to a preferred embodiment of the present invention, the first layer and the second layer may be formed of the same material.

A component-embedded substrate according to a preferred embodiment of the present invention includes a first in-plane conductor including a plurality of lands, a first layer disposed on the first in-plane conductor, a first interlayer connection conductor provided in the first layer and electrically connected to a specific one of the lands, a second layer provided by a resin embedding a component, disposed on the first layer, a second interlayer connection conductor disposed in the second layer and electrically connected to the first interlayer connection conductor, and a second in-plane conductor disposed on the upper surface of the second layer and electrically connected to the second interlayer connection conductor.

A component-embedded substrate of a preferred embodiment of the present invention includes a first in-plane conductor including a plurality of lands, a resin first layer disposed on the first in-plane conductor, an interlayer connection conductor disposed in the first layer and electrically connected to a specific one of the lands, a second layer made of a resin embedding a component, disposed on the first layer, a second interlayer connection conductor disposed in the second layer and electrically connected to the first interlayer connection conductor, a resin third layer disposed on the second layer, a third interlayer connection conductor disposed in the third layer and electrically connected to the second interlayer connection conductor, and a second in-plane conductor disposed in the upper surface of the third layer and electrically connected to the third interlayer connection conductor.

Since the second layer in a preferred embodiment of the present invention embeds a component, the second layer is higher than the other layers. In the method of a preferred embodiment of the present invention, the second layer is cured after embedding the component, and then a second interlayer connection conductor is formed in a through-hole. Consequently, the straightness of the second interlayer connection conductor can be prevented from being degraded, and the reliability of the entire component-embedded substrate can be enhanced. Also, since the second interlayer connection conductor is provided in the through-hole, but not a blind hole, the second interlayer connection conductor can have a small diameter. Accordingly, the component-embedded substrate can be miniaturized. In particular, the invention according to a preferred embodiment of the present invention reduces the thickness of the second layer up to the height of the component, thereby forming a highly straight through-hole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Preferred Embodiment

A first preferred embodiment will now be described with reference toFIGS. 1 to 5.FIG. 1is a sectional view of a component-embedded substrate, andFIGS. 2A to 5are representations of a method for manufacturing the component-embedded substrate.

The component-embedded substrate40shown inFIG. 1includes a first in-plane conductor2including a plurality of lands2aon the upper surface of a base plate1. A first layer6made of a resin, for example, is disposed on the upper surface of the first in-plane conductor2. The first layer6is provided with a first interlayer connection conductor5in it so as to be electrically connected to a specific land2aof the plurality of lands2aon the upper surface of the base plate1. A second layer11made of a resin, for example, is further provided on the upper surface of the first layer6, and in which a component9is embedded. Also, a second interlayer connection conductor8is formed and electrically connected to the first interlayer connection conductor5. A second in-plane conductor13is provided on the upper surface of the second layer11and electrically connected to the second interlayer connection conductor8. In the first layer6, other first interlayer connection conductors5are provided at the positions corresponding to the electrodes10of the component9. These first interlayer connection conductors5are electrically connected to other specific lands2aof the first in-plane conductor2. In other words, the first in-plane conductor2and the second in-plane conductor13are connected through a specific first interlayer connection conductor5and second interlayer connection conductor8, and the first in-plane conductor2and the electrodes10of the component9are connected through other specific first interlayer connection conductors5.

The first in-plane conductor2may be provided on the surface of a base plate1made of a resin, a glass epoxy, a multilayer rein plate, or the like, or may be provided using a transfer plate made of, for example, SUS.

The first layer6and the second layer11are preferably formed of a thermosetting resin, such as an epoxy resin, from the viewpoint of ease of curing. Also, a photo-curable resin that can be cured by UV light may be used. It is desirable that a material difficult to shrink with heat be selected. Preferably, the first layer6and the second layer11are formed of the same material, so that the thermal expansion coefficient or other properties can be made uniform in the component-embedded substrate and, thus, the reliability can be enhanced.

The first interlayer connection conductors5and the second interlayer connection conductor8are each filled with an electroconductive paste. Thus, the first in-plane conductor2and the second in-plane conductor13disposed in the lower surface or on the upper surface of the component-embedded substrate40are electrically connected to each other, and the first in-plane conductor2and the electrodes10of the component9embedded in the second layer11are electrically connected to each other.

Now, a method for manufacturing the component-embedded substrate40will be described.

FIGS. 2A-2Bare representations of the step of forming the first in-plane conductor2. First, a copper foil layer3is formed on the upper surface of a base plate1shown inFIG. 2A, as shown inFIG. 2B. Then, the copper foil layer3is patterned into a first in-plane conductor2including a plurality of lands2aby, for example, etching, as shown inFIG. 2C. Alternatively, the first in-plane conductor2may be formed by plating the entire upper surface of the base plate1to form an electroconductive layer of an electroconductive metal, such as copper or a copper alloy, and patterning the electroconductive layer.

If the first in-plane conductor2is formed using a transfer plate made of, for example, SUS, the first in-plane conductor2can be transferred to the first layer6by forming and pressing an uncured first layer6on the transfer plate and then removing the transfer plate.

FIGS. 3A-3Care representations of the step of forming the first layer6. An uncured resin first layer6shown inFIG. 3Ais irradiated with laser light from above, corresponding to the positions of the lands2aof the first in-plane conductor2. Thus, holes7are formed so as to pass through the first layer6in the vertical direction, as shown inFIG. 3B. Then, as shown inFIG. 3C, the holes7are filled with an electroconductive paste to form first interlayer connection conductors5.

In this instance, the electroconductive paste is, for example, a resin paste containing an electroconductive material (e.g., metal).

Alternatively, the inner walls of the holes7shown inFIG. 3Bmay be plated to form the first interlayer connection conductors5, instead of filling the holes7with the electroconductive paste. The first interlayer connection conductors5may be formed by plating the inner walls of the holes7and subsequently filling the holes7with an electroconductive paste or a non-electroconductive paste, or by injecting the electroconductive paste into the holes7up to a predetermined height and subsequently plating the inner walls of the holes7.

The first layer6is formed thin without embedding a component or the like. Accordingly, the holes7are hardly deformed by the curing shrinkage of the resin even if the holes7are formed in the first layer6in an uncured state and then the first layer6is cured as described below.

FIGS. 4A-4Eare a representation of the step of forming the second layer11. First, a second layer11made of an uncured resin is prepared, as shown inFIG. 4A, and a component9, such as a chip capacitor, a chip resistor, a chip coil, or an IC, etc., is embedded in the second layer11, as shown inFIG. 4B. In the figure, reference numeral10designates the electrodes of the component9. Then, the second layer11embedding the component9is cured, as shown inFIG. 4C, and the first layer6is irradiated with laser light corresponding to the position of a specific first interlayer connection conductor5to form a hole12passing through the second layer11in the vertical direction, as shown inFIG. 4D. Subsequently, as shown inFIG. 4E, the hole12is filled with an electroconductive paste to form a second interlayer connection conductor8.

Instead of filling the hole12with the electroconductive paste, the inner wall of the hole12shown inFIG. 4Dmay be plated to form the second interlayer connection conductor8. The second interlayer connection conductor8may be formed by filling the plated hole12with an electroconductive paste or a non-electroconductive paste, or by injecting the electroconductive paste into the hole12up to a predetermined height and subsequently plating the inner wall of the hole12.

Although the second layer11is preferably formed of the same thermosetting epoxy resin as the first layer6, other thermosetting or photo-curable resins may of course be used. As with the first layer6, a material that is difficult to shrink is desirably used.

Since the component9is embedded in the second layer11, the second layer11has a certain height. Since the hole12is formed with the second layer11cured, the hole12is not deformed after the formation. Also, since the hole12is formed as a through-hole without disposing an in-plane conductor on the upper surface or the lower surface of the second layer11, the second interlayer connection conductor8is not tapered, but is straight.

Turning now toFIG. 5, the first in-plane conductor2including the plurality of lands2a, the first layer6, and the second layer11are integrated. In this instance, the first in-plane conductor2of the base plate1, the first layer6, and the second layer11are stacked in that order and pressed to join together. In this state, the first layer6is cured to electrically connect a specific land2aof the first in-plane conductor2, the corresponding first interlayer connection conductor5, and the second interlayer connection conductor8to one another, and other specific lands2a, the corresponding first interlayer connection conductors5, and the electrodes10of the component9to one another.

Finally, the upper surface of the integrated component-embedded substrate40is plated with an electroconductive metal, such as copper or a copper alloy, to form an electroconductive layer. The electroconductive layer is patterned by etching or the like to form a second in-plane conductor13. Thus, the component-embedded substrate40as shown inFIG. 1is completed. The second in-plane conductor13may not be patterned. If, for example, the resulting component-embedded substrate40is formed on the uppermost layer of a multilayer substrate, the second in-plane conductor13is formed over the entire upper surface of the second layer11so as to act as a shield electrode.

In the first preferred embodiment, as described above, the hole12is a through-hole formed without disposing an in-plane conductor on the upper surface or the lower surface. Therefore, the diameter of the hole12intended for the second interlayer connection conductor8is not increased, and accordingly a narrow pitch wiring can be made. Also, since the second interlayer connection conductor8is formed after curing the second layer11, the straightness of the second interlayer connection conductor8is not degraded by any curing shrinkage of the second layer11. Consequently, a reliable wiring can be made. As described above, the first interlayer connection conductors5are formed with the first layer6uncured. However, the straightness of the first interlayer connection conductors5is hardly affected by the curing shrinkage of the first layer6because of the small thickness of the first layer. Therefore, the pitch can be reduced in the entire component-embedded substrate40and the reliability can be increased, by forming the hole12intended for the second interlayer connection conductor8with a small diameter, and by maintaining the straightness of the hole12.

Second Preferred Embodiment

A second preferred embodiment will be described with reference toFIGS. 6 to 8.FIG. 6is a sectional view of a component-embedded substrate50, andFIGS. 7A to 8are representations of a method for manufacturing the component-embedded substrate50. InFIGS. 6 to 8, the same reference numerals as inFIGS. 1 to 5designate the same or equivalent elements.

As with the component-embedded substrate40of the first preferred embodiment, the component-embedded substrate50of the present preferred embodiment includes a first in-plane conductor2, a first layer6, and a second layer11. While the first in-plane conductor2, the first layer6, and the second layer11have the same structure as in the first preferred embodiment, the present preferred embodiment is different from the first preferred embodiment in that a third layer16having a second in-plane conductor17is provided on the second layer11, as shown inFIG. 6.

FIGS. 7A-7Care a representation of the step of forming the third layer16on which the second in-plane conductor17is disposed. As shown inFIG. 7A, the second in-plane conductor17is formed of, for example, copper foil on the upper surface of the third layer16made of an uncured resin. Since the third layer16is uncured, the copper foil second in-plane conductor17can be easily formed by pressing the copper foil to join. Then, the third layer16is irradiated with laser light from below corresponding to the position of the second interlayer connection conductor8in the second layer11. Thus a hole18is formed with the second in-plane conductor17used as the bottom, as shown inFIG. 7B. Then, the hole18is filled with an electroconductive paste to form a third interlayer connection conductor19, as shown inFIG. 7C.

Instead of filling the hole18with the electroconductive paste, the inner wall of the hole18shown inFIG. 7Bmay be plated to form the third interlayer connection conductor19. The third interlayer connection conductor19may be formed by plating the inner wall of the hole18and subsequently filling the plated hole18with an electroconductive paste, or by injecting the electroconductive paste into the hole18up to a predetermined height and subsequently plating the hole18.

Although the third layer16is preferably formed of a thermosetting epoxy resin as the first layer6and the second layer11in the first preferred embodiment, other thermosetting or photo-curable resins may be used. A material that is difficult to shrink is desirable. Preferably, the first layer6, the second layer11, and the third layer16are formed of the same material, so that the thermal expansion coefficient and other properties can be made uniform in the component-embedded substrate and, thus, the reliability can be enhanced.

The third layer16is formed to be thin without embedding a component. Accordingly, the hole18is hardly deformed by the shrinkage of the third layer16even if the hole18is formed in an uncured third layer16and then the third layer16is cured. The hole18intended for the third interlayer connection conductor19is a blind hole with the second in-plane conductor17used as the bottom, and the third interlayer connection conductor19is tapered as shown inFIG. 7. Since the hole has a small thickness, however, the hole18is not necessarily formed to a large diameter so as to be closely filled with an electroconductive paste. Thus, the shape and diameter of the hole18intended for the third interlayer connection conductor19hardly affect the reliability and the reduction in pitch of the entire component-embedded substrate.

Turning now toFIG. 8, the first in-plane conductor2, the first layer6, the second layer11, and the third layer16are respectively stacked in that order and pressed to be joined together. In this state, the first layer6and the third layer16are cured by heating or other desirable steps to electrically connect a specific land2aof the first in-plane conductor2, the corresponding first interlayer connection conductor5, the second interlayer connection conductor8, and the third interlayer connection conductor19to one another, and other specific lands2a, the corresponding first interlayer connection conductors5, and the electrodes10of the component9to one another. Thus, the component-embedded substrate50shown inFIG. 6is assembled.

The copper foil layer formed on the upper surface of the integrated component-embedded substrate50may be patterned into the second in-plane conductor17by, for example, etching. Alternatively, an electroconductive layer may be formed of an electroconductive metal, such as copper or a copper alloy, by plating or other desirable steps. A transfer plate made of, for example, SUS may be used for forming the second in-plane conductor17.

In the second preferred embodiment as well as the first preferred embodiment, as described above, the second interlayer connection conductor8is formed after the second layer11is cured. Consequently, the straightness of the second interlayer connection conductor8is not degraded. Since the hole12intended for the second interlayer connection conductor8is a through-hole, the diameter of the hole12is not increased. By straightly forming the second interlayer connection conductor8with a small diameter in the highest second layer11, the pitch can be reduced in the entire component-embedded substrate50and the reliability can be enhanced.

In the second preferred embodiment, the third layer16having the second in-plane conductor17is provided. Consequently, the step of plating the upper surface of the second layer11to form an electroconductive layer is not required after integrating the first in-plane conductor2, the first layer6, and the second layer11, unlike the first preferred embodiment. In addition, the third interlayer connection conductor19is formed with the second in-plane conductor17used as the bottom. Thus, the reliability in continuity can be enhanced between the second in-plane conductor17and the third interlayer connection conductor19.

Third Preferred Embodiment

A third preferred embodiment will be described with reference toFIGS. 9 to 11.FIG. 9is a sectional view of a component-embedded substrate60, andFIGS. 10A to 11are representations of a method for manufacturing the component-embedded substrate60. InFIGS. 9 to 11, the same reference numerals as inFIGS. 1 to 8designate the same or equivalent elements.

The component-embedded substrate60of the present preferred embodiment is different from the component-embedded substrate50of the second preferred embodiment in that the first layer6is stacked and pressed on the first in-plane conductor2to join together and subsequently first interlayer connection conductors22are formed with the first layer uncured, as shown inFIG. 9. The second layer11, the third16, and the second in-plane conductor17are formed in the same manner as in the second preferred embodiment.

FIG. 10is a representation of the step of forming the first layer6of the present preferred embodiment. As shown inFIG. 10A, a first in-plane conductor2including a plurality of lands2ais formed on the upper surface of a base plate1in the same manner as the first in-plane conductor2of the first preferred embodiment, and then an uncured resin first layer6is formed on the first in-plane conductor2. Then, the first in-plane conductor2is irradiated with laser light corresponding to the positions of the lands2ato form holes21with the lands2aused as the bottoms, as shown inFIG. 10B. Then, the holes21are filled with an electroconductive paste to form first interlayer connection conductors22, as shown inFIG. 10C. Although the holes21of the first interlayer connection conductors22are tapered (with a trapezoidal section), this is not a problem because of the small thickness of the first layer6. The holes21may be plated instead of filling the holes21with an electroconductive paste.

Turning now toFIG. 11, the first layer6including the first in-plane conductor2, the second layer11, and the third layer16including the second in-plane conductor17are integrated. In this state, the first layer6and the third layer16are cured by heating or other desirable steps to electrically connect a specific lands2aof the first in-plane conductor2, the corresponding first interlayer connection conductor22, the second interlayer connection conductor8, and the third interlayer connection conductor19, and the second in-plane conductor17to one another, and other specific lands2a, the corresponding first interlayer connection conductors22, and the electrodes10of the component9are electrically connected to one another. Thus, the component-embedded substrate60shown inFIG. 9is assembled.

In the third preferred embodiment as well, as described above, the second interlayer connection conductor8is formed with the second layer11cured. Consequently, the straightness of the second interlayer connection conductor8is not degraded. Since the hole12(shown inFIG. 4D) intended for the second interlayer connection conductor8is a through-hole, the diameter of the holes12is not increased. By straightly forming the second interlayer connection conductor8with a small diameter in the highest second layer11, the pitch can be reduced in the entire component-embedded substrate60and the reliability can be enhanced.

In the second preferred embodiment, the first interlayer connection conductors22are formed with the first in-plane conductor2used as the bottoms. Consequently, the reliability in continuity can be enhanced between the first in-plane conductor2and the first interlayer connection conductors22.

If the first in-plane conductor2is formed using a transfer plate made of, for example, SUS, an uncured first layer6is formed and pressed on the transfer plate to join together, and the transfer plate is removed after curing the first layer6through predetermined steps. Thus, the first in-plane conductor2can be transferred to the first layer6.

Modification

A modification of the third preferred embodiment will be described with reference toFIGS. 12 to 14.FIG. 12is a sectional view of a component-embedded substrate70, andFIGS. 13 and 14are representations of a method for manufacturing the component-embedded substrate70. InFIGS. 12 to 14, the same reference numerals as inFIGS. 1 to 11designate the same or equivalent parts.

In the component-embedded substrate70of the modification, the second in-plane conductor17of the component-embedded substrate60according to the third preferred embodiment is replaced with a second in-plane conductor26provided on a transfer plate25, as shown inFIG. 12. The transfer plate25including the second in-plane conductor26is stacked and pressed on an uncured resin third layer16to join together. The second in-plane conductor26is embedded in the third layer16at this point. In this state, the third layer is irradiated with laser light corresponding to the positions of a plurality of lands of the second in-plane conductor26. Thus, a hole (not shown) is formed with the second in-plane conductor26used as the bottom. The hole is filled with an electroconductive paste to form a third interlayer connection conductor28.

Turning now toFIG. 13, the first layer6including the first in-plane conductor2, the second layer11, and the third layer16including the second in-plane conductor26are stacked in that order and pressed to join together. In this state, the first layer6and the third layer16are cured by heating or other desirable steps to electrically connect a specific land2aof the first in-plane conductor2, the corresponding first interlayer connection conductor22, the second interlayer connection conductor8, the third interlayer connection conductor28, and the corresponding land26aof the second in-plane conductor26to one another, and other specific lands2a, the corresponding first interlayer connection conductors22, and the electrodes10of the component9to one another. Thus, the component-embedded substrate70shown inFIG. 12is assembled. Then, the transfer plate25is removed from the upper surface of the third layer16, as shown inFIG. 14.

In this modification, the first in-plane conductor2embedded in the first layer6may also be formed using a transfer plate, as well as the second in-plane conductor26embedded in the third layer16.

If the second in-plane conductor26is formed using a transfer plate made of, for example, SUS, an uncured third layer16is formed and pressed on the transfer plate to join together, and the transfer plate25is removed after curing the third layer16by heating or other desirable steps. Thus, the second in-plane conductor26can be transferred into the third layer16. This process does not require a step of forming the second in-plane conductor17by patterning after integration of the first layer6, the second layer11, and the third layer16. The same can apply the first in-plane conductor2.

Although the first layer6, the second layer11, and the third layer16are preferably formed from the same thermosetting epoxy resin, other thermosetting or photo-curable resins may be used. A material resistant to shrinkage is desirable. Preferably, the first layer6, the second layer11, and the third layer16are formed of the same material, so that the thermal expansion coefficient and other properties can be made uniform in the component-embedded substrate and, thus, the reliability can be enhanced.

Fourth Preferred Embodiment

A fourth preferred embodiment will be described with reference toFIGS. 15 to 18.FIG. 15is a sectional view of a component-embedded substrate80, andFIGS. 16A to 18are representations of a method for manufacturing the component-embedded substrate80. InFIGS. 15 to 18, the same reference numerals as inFIGS. 1 to 14designate the same or equivalent parts.

The component-embedded substrate80of the present preferred embodiment is substantially the same as in the first and second preferred embodiments, but is different in that the upper surface of the second layer31embedding the component9is ground to expose the component9at the upper surface of the second layer31, thus reducing the thickness of the second layer31before the second layer31, the first layer6, and the third layer32are integrated, as shown inFIG. 15. The first layer6is formed in the same manner as in the first and second preferred embodiments.

FIGS. 16A-16Fis a representation of the step of forming the second layer31. First, an uncured resin second layer31is prepared, as shown inFIG. 16A, and components9, such as chip capacitors, chip resistors, chip coils, and ICs, are embedded, as shown inFIG. 16B. In the figures, reference numeral10designates the electrodes of the component9. Then, the second layer31embedding the component9is cured, as shown inFIG. 16C, and the upper surface of the second layer31is mechanically ground to expose the components9at the upper surface of the second layer31, and thus the thickness of the second layer31is reduced.

Turning now toFIG. 16E, the second layer31is irradiated with laser light corresponding to the position of a specific first interlayer connection conductor5in the first layer6to form a hole33passing through the second layer31in the vertical direction. Subsequently, the hole33is filled with an electroconductive paste to form a second interlayer connection conductor34, as shown inFIG. 16F.

Since the hole33is formed with the second layer31cured, the hole33is not deformed after the formation. Since the hole33is a through-hole formed without disposing an in-plane conductor on the upper surface or the lower surfaces of the second layer31, the second interlayer connection conductor34is not tapered, but is straight. In addition, the thickness of the second layer31is reduced to the extent that the component9is exposed at the upper surface of the second layer, and accordingly, the shape of the hole33can be straighter.

The third layer32is formed in the same manner as in the modification of the third preferred embodiment. More specifically, as shown inFIG. 17, a transfer plate35including a second in-plane conductor36is disposed on the uncured resin third layer32and pressed to join together. The second in-plane conductor36is embedded in the third layer32at this point. In this state, the third layer32is irradiated with laser light from below corresponding to the positions of lands36aof the second in-plane conductor36. Thus, the holes (not shown) are formed with the second in-plane conductor36used as the bottoms. The holes are filled with an electroconductive paste to form third interlayer connection conductors38.

Turning now toFIG. 17, the first in-plane conductor2, the first layer6, the second layer31, and the third layer32including the second in-plane conductor36are stacked in the order to be joined together. In this state, the first layer6and the third layer32are cured by heating or other suitable steps to electrically connect a specific land2aof the first in-plane conductor2, the corresponding first interlayer connection conductor5, the second interlayer connection conductor34, the third interlayer connection conductor38, and the corresponding land36aof the second in-plane conductor36to one another, and other specific lands2a, the corresponding first interlayer connection conductors5, the electrodes10of the components, the corresponding third interlayer connection conductor38, and the corresponding land36aof the second in-plane conductor36to one another. Thus, the component-embedded substrate80is assembled. The transfer plate35is finally removed from the upper surface of the third layer32, as shown inFIG. 18.

The first in-plane conductor2in the first layer6may also be formed using a transfer plate, as well as the second in-plane conductor36in the third layer32.

In the fourth preferred embodiment, the thickness of the second layer31is reduced before being integrated with the first layer6and the third layer32. Accordingly, the second interlayer connection conductor34can be formed straighter, and the diameter of the hole33intended for the second interlayer connection conductor34can be reduced. Thus, the pitch can be reduced. If the electrodes10of the component9are exposed at the upper surface of the second layer31, the electrodes10and the third interlayer connection conductor38in the third layer32can be electrically connected directly. Thus, wiring can be more arbitrarily performed and effective wiring becomes possible.

The step of reducing the thickness of the second layer31may be performed after forming the hole33, or after filling the hole33with an electroconductive paste to form the second interlayer connection conductor34, without limiting to the time before forming the hole33, as long as this step is performed after curing the second layer31embedding the component9and before integrating the first layer6, the second layer31, and the third layer32.

In the fourth preferred embodiment, the second in-plane conductor36is formed using the transfer plate35made of, for example, SUS. This method does not require the step of patterning the second in-plane conductor36by etching or the like after the integration of the first layer6, the second layer31, and the third layer32.

The formation of the third layer32is not limited to using the transfer plate35as in the present preferred embodiment. For example, the second in-plane conductor may be formed by patterning a plated electroconductive layer, a copper foil, or the like, by etching or the like.

The reduction of the thickness of the second layer31is not limited to mechanical grinding of the upper surface of the second layer31, and other techniques may be applied. For example, the second layer31may be cut to a predetermined height so that the component9can be exposed at the upper surface of the second layer31. The electrodes10of the component9may be exposed as above, or may not be exposed.

The inner wall of the hole33shown inFIG. 16Emay be plated to form the second interlayer connection conductor34instead of filling the hole33with an electroconductive paste. The second interlayer connection conductor34may be formed by filling a plated hole33with an electroconductive paste or a non-electroconductive paste, or by injecting the electroconductive paste into the hole33up to a predetermined height and subsequently plating the inner wall of the hole33.

Although the first layer6, the second layer31, and the third layer32are preferably formed of a thermosetting epoxy resin, other thermosetting or photo-curable resins may be used. A material resistant to shrinkage is preferably used. Preferably, the first layer6, the second layer31, and the third layer32are formed of the same 3 material, so that the thermal expansion coefficient and other properties can be made uniform in the component-embedded substrate and, thus, the reliability can be increased.

Fifth Preferred Embodiment

A fifth preferred embodiment will be described with reference toFIGS. 19 to 23.FIG. 19is a sectional view of a component-embedded substrate90, andFIGS. 20A to 23are representations of a method for manufacturing the component-embedded substrate90. InFIGS. 19 to 23, the same reference numerals as inFIGS. 1 to 18designate the same or equivalent elements.

The component-embedded substrate90of the present preferred embodiment is substantially the same as in the fourth preferred embodiment, but is different in that the component9is mounted on electrodes42and embedded in a resin layer in a second layer41, as shown inFIG. 19. The first layer6, the third layer32, and the second in-plane conductor36are formed in the same manner as in the fourth preferred embodiment.

FIGS. 20A to 21Dare representations of the step of forming the second layer41. First, a transfer plate43including electrodes42as shown isFIG. 20Ais prepared, and the component9is mounted with its electrodes10aligned with the positions corresponding to the electrodes42, as shown inFIG. 20B. Then, the electrodes42and the component9are embedded in an uncured second layer41, followed by curing, as shown inFIGS. 20C and 20D. Then, the transfer plate43is removed as shown inFIG. 20E.

After the removal of the transfer plate43, the upper surface of the second layer41is ground to expose the component9at the upper surface of the second layer41, as shown inFIGS. 21A and 21B. Then, the second layer41is irradiated with laser light corresponding to the position of a specific first interlayer connection conductor5in the first layer6to form a hole44passing through the second layer41in the vertical direction, as shown inFIG. 21C. In addition, as shown inFIG. 21D, the hole44is filled with an electroconductive paste to form a second interlayer connection conductor45.

Since the hole44is formed with the second layer41cured, the hole44is not deformed after the formation. Since the hole44is a through-hole formed without disposing an in-plane conductor on the upper or the lower surface, the second interlayer connection conductor45is not tapered, but is straight. In addition, the thickness of the second layer41is reduced to the extent that the component9is exposed at the upper surface of the second layer, and accordingly, the shape of the hole44can be straighter.

The third layer32is formed in the same manner as in the fourth preferred embodiment. More specifically, a transfer plate35including the second in-plane conductor36is disposed on the uncured resin third layer32and pressed to be joined together, as shown inFIG. 19. The second in-plane conductor36is embedded in the third layer32at this point. In this state, the third layer32is irradiated with laser light from below corresponding to the positions of a plurality of lands36aof the second in-plane conductor36. Thus, the holes (not shown) are formed with the second in-plane conductor36used as the bottoms. The holes are filled with an electroconductive paste to form third interlayer connection conductors38.

Then, the first in-plane conductor2, the first layer6, the second layer41, and the third layer32are stacked in that order and pressed to join together, as shown inFIG. 22. In this state, the first layer6and the third layer32are cured by heating or other desirable steps to electrically connect a specific land2aof the first in-plane conductor2, the corresponding first interlayer connection conductor5, the second interlayer connection conductor45, the corresponding third interlayer connection conductor38, and the corresponding land36aof the second in-plane conductor36to one another, and other specific lands, the corresponding first interlayer connection conductors5, the electrodes42, and the electrodes10of the components, the corresponding third interlayer connection conductor38, and the corresponding lands36aof the second in-plane conductor36to one another. Thus, the component-embedded substrate90shown inFIG. 19is assembled and the transfer plate35is removed from the upper surface of the third layer32, as shown inFIG. 23.

The first in-plane conductor2in the first layer6may also be formed using a transfer plate, as well as the second in-plane conductor36in the third layer32.

In the fifth preferred embodiment, as described above, the component9is embedded in the uncured second layer41after being mounted on the electrode42. Accordingly, the component9is difficult to displace when the second layer41is cured, and the first layer6, the second layer41, and the third layer32can be integrated with high positioning accuracy.

Since the thickness of the second layer41is reduced before being integrated with the first layer6and the third layer32, the second interlayer connection conductor45can be formed straighter. Thus, diameter of the hole44intended for the second interlayer connection conductor45can be reduced and the pitch can be reduced. If the electrodes10of the component9are exposed at the upper surface of the second layer41, the electrodes10and the third interlayer connection conductor38in the third layer can be electrically connected directly. Thus, wiring can be more arbitrarily performed and effective wiring becomes possible.

The step of reducing the thickness of the second layer41may be performed after forming the hole44, or after filling the hole44with an electroconductive paste to form the second interlayer connection conductor45, without limiting to the time before forming the hole44, as long as this step is performed after embedding the component9in the second layer41and before integrating the first layer6, the second layer41, and the third layer. The thickness of the second layer41may not be reduced.

In the fifth preferred embodiment, the second in-plane conductor36is formed using the transfer plate35made of, for example, SUS. This method does not require the step of patterning the second in-plane conductor36by etching or the like after the integration of the first layer6, the second layer41, and the third layer32.

The formation of the third layer32is not limited to using the transfer plate35as in the present preferred embodiment. For example, the second in-plane conductor may be formed by patterning a plated electroconductive layer, a copper foil, or the like, by etching or the like.

The reduction of the thickness of the second layer41is not limited to mechanical grinding of the upper surface of the second layer41, and other techniques may be applied. For example, the second layer41may be cut to a predetermined height so that the component9can be exposed at the upper surface of the second layer41. The thickness of the second layer41may not be reduced.

As with the first to fourth preferred embodiments, the inner wall of the hole44shown inFIG. 21Cmay be plated to form the second interlayer connection conductor45, instead of filling the hole44with an electroconductive paste. The interlayer connection conductor45may be formed by filling a plated hole44with an electroconductive paste or a non-electroconductive paste, or injecting the electroconductive paste into the hole33up to a predetermined height and subsequently plating the inner wall of the hole44.

Although the first layer6, the second layer41, and the third layer32are preferably formed of a thermosetting epoxy resin, other thermosetting or photo-curable resins may be used. A material difficult to shrink is desirably used. Preferably, the first layer6, the second layer41, and the third layer32are formed of the same material, so that the thermal expansion coefficient and other properties can be made uniform in the component-embedded substrate and, thus, the reliability can be increased.

The present invention is not limited to the above-described preferred embodiments, and various modifications may be made without departing from the scope and spirit of the invention.

For example, the first preferred embodiment may be modified to a form in which the first layer6is formed of an uncured resin on the upper surface of the base plate1having the first in-plane conductor2including a plurality of lands2aon the upper surface, and the uncured first layer6is irradiated with laser light from above corresponding to the position of a specific land2aof the first in-plane conductor2to form the first interlayer connection conductor22with the land2aused as the bottom, as in the third preferred embodiment. The first interlayer connection conductor in the second, fourth, and fifth preferred embodiments may also be formed in the same manner.

The first layer and the second layer may be formed of the same material, and the third layer may also be formed of the same material.

The present invention can be applied to component-embedded substrates having various functions and characteristics.