JP2021009868A - Manufacturing method of wiring board - Google Patents

Abstract

To provide a manufacturing method of a wiring board including an electronic component well.SOLUTION: A manufacturing method of a wiring board includes preparing a substrate 1a on which a cavity C is formed, and accommodating an electronic component E in a cavity C, and a first adhesive layer 21 is formed at the bottom of the cavity C, the fluidity of the first adhesive layer 21 is reduced, and a second adhesive layer 22 is formed on the first adhesive layer 21 with reduced fluidity, the electronic component E is placed on the second adhesive layer 22, and the electronic component E is housed in the cavity C by curing the first adhesive layer 21 and the second adhesive layer 22.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a wiring board.

Patent Document 1 discloses a multilayer printed wiring board in which a semiconductor element is housed in a recess provided in a resin insulating layer. In Patent Document 1, the semiconductor element is accommodated in the recess by accommodating the semiconductor element having the adhesive layer formed on the lower surface side opposite to the terminal surface of the semiconductor element in the recess, and then heat-treating the adhesive layer. It is done by curing.

International Publication No. 2007/043714

In the method for manufacturing a multilayer printed wiring board of Patent Document 1, a metal layer for ensuring the storage and adhesion of semiconductor elements is formed on the bottom surface of the recess. However, when the semiconductor element is placed with the adhesive layer facing the metal layer and during thermosetting, the adhesive may move, causing misalignment in the recess of the housed semiconductor element.

The method for manufacturing a wiring board of the present invention includes preparing a substrate on which a cavity is formed and accommodating an electronic component in the cavity. Then, accommodating the electronic component in the cavity forms the first adhesive layer at the bottom of the cavity, reduces the fluidity of the first adhesive layer, and reduces the fluidity. Forming a second adhesive layer on the first adhesive layer, placing an electronic component on the second adhesive layer, and curing the first adhesive layer and the second adhesive layer. Including to let.

According to the embodiment of the present invention, it is possible to provide a method for manufacturing a wiring board in which problems such as misalignment and inclination do not occur in electronic components housed in the cavity of the wiring board.

The cross-sectional view which shows an example of the wiring board manufactured by the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the cavity formation process of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the cavity formation process of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the cavity formation process of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the cavity formation process of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the cavity formation process of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the cavity formation process of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the wiring board of one Embodiment of this invention. The figure which shows an example of the manufacturing method of the wiring board of one Embodiment of this invention.

An embodiment of the method for manufacturing a wiring board of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a part of a wiring board 1 which is an example of a wiring board manufactured by the method for manufacturing a wiring board according to an embodiment of the present invention. The manufacturing method of the portion of the wiring board 1 shown in FIG. 1 is shown in FIGS. 2A to 2D. As shown in FIG. 1, the wiring board 1 includes a substrate 1a having a bottomed cavity C in the resin insulating layer 10 and an electronic component E housed in the cavity C.

In the example of FIG. 1, the electronic component E is housed in the cavity C via the first adhesive layer 21 and the second adhesive layer 22 formed on the bottom surface C1 of the cavity C. The electronic component E housed in the cavity C is not limited to these, but is a semiconductor element, a passive element, an interposer having a rewiring layer, a semiconductor element having a rewiring layer, a WLP (Wafer Level Package), and the like. IPD (Integrated Passive device) and the like can be mentioned. The electronic component E is arranged so that the lower side surface E2, which is the opposite surface of the terminal surface E1 of the electronic component E, faces the bottom surface C1 of the cavity C. That is, the electronic component E is fixed to the bottom surface C1 of the cavity C by the lower side surface E2 side being brought into close contact with the first adhesive layer 21 and the second adhesive layer 22.

The cavity C can be formed in any resin insulating layer 10 of the substrate 1a. The substrate 1a may be, for example, a build-up wiring board in which a plurality of resin insulating layers 10 and a plurality of conductor layers 11 are alternately laminated. In the example of FIG. 1, the substrate 1a includes a resin insulating layer 10 and a conductor layer 11 formed of, for example, a copper foil and a copper plating film on both sides of the resin insulating layer 10. The resin insulating layer 10 includes a via conductor 12 that penetrates the resin insulating layer 10 and connects the conductor layers 11 to each other.

The size of the cavity C can be appropriately selected depending on the electronic component E to be accommodated. For example, in the example shown in FIG. 1, the cavity C is formed so as to have a depth corresponding to the thickness of one resin insulating layer 10. However, the number of layers of the resin insulating layer 10 forming the side surface of the cavity C is not limited to the example of FIG. For example, two or more resin insulating layers 10 may form the side surface of the cavity C. Further, the planar shape of the cavity C can also be formed into an arbitrary planar shape depending on the shape of the electronic component housed in the cavity C and the like.

A method of accommodating the electronic component E in the cavity C of the substrate 1a shown in FIG. 1 will be specifically described with reference to FIGS. 2A to 2D, and a method of manufacturing the wiring board 1 of FIG. 1 will be shown. In the attached drawings, it is not intended to show an accurate ratio of the size and shape of each component including the cavity C of the wiring board.

First, the substrate 1a having the cavity C shown in FIG. 2A is prepared. The cavity C is formed by removing the place where the cavity C of the resin insulating layer 10a of the substrate 1a is formed. The removal can be performed by forming a recess by, for example, counterbore processing. However, the substrate 1a provided with the cavity C may be formed by laminating the resin insulating layer 10a having the openings on the resin insulating layer 10 (10b) instead of providing the recesses by such processing. In the substrate 1a, the resin insulating layer 10 can be formed by using an arbitrary insulating material. Therefore, the resin insulating layer 10a on which the cavity C is formed is the resin insulating layer 10 formed by using an arbitrary insulating material. Examples of the insulating material include resin materials such as epoxy resin, bismaleimide triazine resin (BT resin), and phenol resin. Each resin insulating layer 10 including the resin insulating layer 10a formed by using these resin materials may contain a reinforcing material such as glass fiber or aramid fiber and / or an inorganic filler such as silica.

In the present embodiment, the resin insulating layer 10b is exposed on the bottom surface C1 of the cavity C. That is, the surface of the resin insulating layer 10b on the resin insulating layer 10a side forms the bottom surface C1 of the cavity C.

Next, as shown in FIG. 2B, the first adhesive layer 21 is formed on the bottom surface C1 of the cavity C. The first adhesive layer 21 is formed by applying the first adhesive material 21a onto the bottom surface C1 of the cavity C. Examples of the first adhesive material 21a include epoxy resin and the like. Preferably, the first adhesive material 21a is an adhesive that is cured and used by irradiation with light and heating. As will be described later, in one embodiment, the first adhesive material 21a is used after being cured by heating to a semi-cured state by proceeding with curing by irradiation with light. However, a thermosetting adhesive may be used as the first adhesive material 21a, and thermosetting may be performed so that the degree of curing is increased in two steps.

The first adhesive material 21a is preferably applied using an inkjet device. Therefore, the first adhesive material 21a is liquid at room temperature (25 ° C.). The viscosity of the first adhesive material 21a at 25 ° C. is preferably about 10 mPa · s or more and about 100 mPa · s or less. It is considered that the thickness accuracy of the layer of the first adhesive material 21a after coating is high. Further, it is considered that voids are unlikely to occur in the formed first adhesive layer 21. The first adhesive material 21a is applied onto the bottom surface C1 of the cavity C, for example, with a thickness t1 of about 15 μm or more.

The first adhesive material 21a is then preferably photocured. The semi-cured first adhesive layer 21 with reduced fluidity is formed.

Next, the second adhesive layer 22 is formed on the semi-cured first adhesive layer 21. As shown in FIG. 2C, the second adhesive material 22a for forming the second adhesive layer 22 is applied onto the semi-cured first adhesive layer 21. The second adhesive material 22a may be the same adhesive material as the first adhesive material 21a, but may be different. As the second adhesive material 22a, if it contains a thermosetting resin, it can be used satisfactorily.

The second adhesive material 22a is preferably applied using an inkjet device. Therefore, the second adhesive material 22a is liquid at room temperature (25 ° C.) like the first adhesive material 21a. The viscosity of the second adhesive material 22a at 25 ° C. is preferably about 10 mPa · s or more and about 100 mPa · s or less. It is considered that the thickness accuracy of the layer of the second adhesive material 22a after coating is high. Further, it is considered that voids are unlikely to occur in the formed second adhesive layer 22. The second adhesive material 22a is applied onto the semi-cured first adhesive layer 21 having a thickness t2 of about 5 μm or more, for example.

Here, preferably, the first adhesive material 21a and the second adhesive material 22a have the following formula: the thickness t1 of the first adhesive material 21a and the thickness t2 of the second adhesive material 22a.
0.6 <t1 / (t1 + t2) <0.9
Each is applied so as to satisfy. In the present embodiment, the first adhesive material 21a is semi-cured before the application of the second adhesive material 22a. When the electronic component E is housed in the cavity C, it may be necessary to increase the thickness of the adhesive layer to increase the distance of the electronic component E from the bottom surface C1 of the cavity C. In the present embodiment, the ratio of the semi-cured first adhesive material 21a to the total thickness of the adhesive layer (total thickness of the first adhesive layer 21 and the second adhesive layer 22) is second. 2 It is made larger than the layer of the adhesive material 22a. Even if the thickness of the adhesive layer is increased, it is considered that the position shift or inclination of the electronic component E due to the deformation of the adhesive layer is unlikely to occur when the electronic component E is placed on the adhesive layer. .. The sum of the thickness t1 of the first adhesive material 21a and the thickness t2 of the second adhesive material 22a is about 5 μm or more and about 50 μm or less. When the thickness of the adhesive layer is about 5 μm or more, it is considered that the effect of preventing the deformation of the adhesive layer by the semi-cured first adhesive material 21a can be sufficiently obtained. Further, when the thickness of the adhesive layer is about this level, the stress that can be generated due to the difference in the coefficient of thermal expansion between the electronic component E and the resin insulating layer 10b (see FIG. 2A) forming the bottom surface C1 of the cavity C is reduced. It is thought that it can be done.

The electronic component E is then placed on the coated second adhesive material 22a, as shown in FIG. 2D. In the electronic component E, the lower side surface E2 of the electronic component E, which is the opposite surface of the terminal surface E1, faces the second adhesive material 22a in the cavity C so that the terminal surface E1 of the electronic component E is exposed from the cavity C. It is placed in. In the present embodiment, the first adhesive layer 21 in the adhesive layer is in a semi-cured state, and a thinner layer of the second adhesive material 22a is formed on the first adhesive layer 21, so that the lower side surface of the electronic component E is formed. When E2 comes into contact with the second adhesive material 22a, the electronic part E is directed toward the second adhesive material 22a in order to remove air bubbles that may be formed between the lower side surface E2 of the electronic component E and the interface between the second adhesive material 22a. There is no need for the process of pushing in. Since it is not necessary to push the electronic component E to be placed toward the adhesive layer, it is not necessary to form the layer of the adhesive material smaller than the planar shape of the electronic component E. In the present embodiment, the first adhesive material 21a and the second adhesive material 22a may be applied to the entire surface of the bottom surface C1 of the cavity C.

Next, the semi-cured first adhesive layer 21 and the second adhesive material 22a are cured. Curing is preferably performed by thermosetting. The first adhesive layer 21 and the second adhesive layer 22 are formed, and the electronic component E is fixed in the cavity C by both the adhesive layers 21 and 22.

Thermosetting is performed, for example, by heating to a temperature of about 100 ° C. or higher and about 200 ° C. or lower. As a result, the first adhesive layer 21 and the second adhesive layer 22 are completely cured. In the present embodiment, since the first adhesive layer 21 is in a semi-cured state before the main curing in this step, the first adhesive material may move or be deformed even when heated. There is no risk of it going away. On the other hand, since the layer of the uncured second adhesive material 22a is relatively thin, it is considered that the degree of deformation is small even if the fluidity of the second adhesive material 22a is increased by heating.

When the electronic component E is placed on the uncured adhesive layer and heated to cure the adhesive layer, it increases during heating, especially when a relatively thick adhesive layer is formed. Due to the fluidity of the adhesive, there is a problem that the electronic component E is fixed or tilted toward one end in the cavity C. According to this embodiment, the layer of the first adhesive material 21a that is in a semi-cured state and the layer of the second adhesive material 22a that is in an uncured state when the electronic component E is placed in the cavity C The thicknesses t1 and t2 are, as described above, the formula:
0.6 <t1 / (t1 + t2) <0.9
It has been selected to meet. Therefore, the first adhesive layer 21 occupies a thicker portion of the adhesive layer for fixing the electronic component E. In the present embodiment, the first adhesive layer 21 that occupies a larger portion of the adhesive layer is already in a semi-cured state when the electronic component E is placed in the cavity C. It is considered that the problem that the electronic component E moves or tilts during heating does not occur. Since the thickness t2 of the layer of the second adhesive material 22a is thin, it is considered that there is almost no effect of causing the misalignment of the electronic component E.

Therefore, this embodiment is considered to be particularly advantageous when a relatively thick adhesive layer is required between the lower side surface E2 of the electronic component E and the bottom surface C1 of the cavity C.

It is considered that the adhesive strength of the first adhesive layer 21 in the semi-cured state is lower than that in the uncured state. However, since the uncured second adhesive material 22a is applied onto the semi-cured first adhesive layer 21, after the second adhesive material 22a is cured, the first adhesive layer 21 and the second adhesive layer 21 are adhered. The agent layer 22 adheres well. Similarly, the uncured second adhesive material 22a satisfactorily adheres the electronic component E to the first adhesive layer 21 after curing.

The heating process for thermosetting the first adhesive layer 21 and the second adhesive layer 22 may be performed with vacuuming. In some cases, the air bubbles existing in the applied first adhesive material 21a and the second adhesive material 22a can be defoamed. Further, it is considered that air bubbles that may be generated when the electronic component E is placed on the second adhesive material 22a can also be removed. If air bubbles are present between the electronic component E and the adhesive layer, problems such as peeling of the electronic component E from the adhesive layer may occur. It may cause a deterioration in the manufacturing yield of the wiring board 1. Therefore, it may be preferable to remove air bubbles to further improve the adhesion of the electronic component E to the adhesive layer. It is considered that the quality reliability of the wiring board 1 is further improved. For example, the heating process can be performed under a vacuum reach of about 5 kPa or less.

Subsequently, an example of a method for forming the cavity C will be described (FIGS. 3A to 3F). However, the method of forming the cavity is not limited to the method shown. Further, for example, the place where the cavity C is formed on the substrate 1a is not limited. As described above, the cavity C can be formed in any resin insulating layer 10 of the substrate 1a. For example, in the example shown in FIGS. 3A to 3F, the cavity C is formed so that the resin insulating layer 10b, which is the resin insulating layer 10 in the build-up layer of the substrate 2a, is exposed on the bottom surface C1 of the cavity C (). FIG. 3F). However, the cavity C may be formed in, for example, the resin insulating layer 10 (resin insulating layer 10b in FIG. 3F) directly above the carrier plate 5. In this case, the metal foil 51 of the carrier plate 5 is exposed on the bottom surface C1 of the cavity C.

As shown in FIG. 3A, the carrier plate 5 has a carrier 50 and a metal foil 51 on its surface. The metal foil 51 includes a carrier metal foil 52 bonded to one surface, and the carrier metal foil 52 and the carrier 50 are joined by thermocompression bonding or the like. The metal foil 51 and the carrier metal foil 52 are bonded with a separable adhesive such as a thermoplastic adhesive, or are fixed only at the edges. The carrier 50 is, for example, a glass epoxy substrate. Further, a double-sided copper-clad laminate may be used as the carrier plate 5. However, the carrier 50 and the carrier plate 5 are not limited to these.

The resin insulating layer 10 and the conductor layer 11 are laminated on the carrier plate 5 by using a general method for manufacturing a build-up wiring board. As shown in FIG. 3B, the resin insulating layer 10b is formed by laminating, for example, a film-shaped epoxy resin or prepreg. A through hole for a via conductor (not shown) may be formed in the insulating layer 10b at a desired position. Then, for example, using the semi-additive method, as shown in FIG. 3C, a second conductor layer 11b having the desired conductor pattern on the resin insulating layer 10b (and, if desired, in the through hole for the via conductor). A via conductor is formed simultaneously and integrally with the formation of the second conductor layer 11b). The second conductor layer 11b includes the conductor pattern 110 at a position where the cavity C is formed.

Subsequently, as shown in FIG. 3D, the resin insulating layer 10a and the first conductor layer 11a are laminated on the resin insulating layer 10b and the second conductor layer 11b. Simultaneously and integrally with the formation of the first conductor layer 11a, the via conductor 12 connecting the first conductor layer 11a and the second conductor layer 11b formed on both sides of the resin insulating layer 10a is formed at a desired position. To. Therefore, the via conductor 12, the first conductor layer 11a, and the second conductor layer 11b are formed of the same plating film (electroless plating film and electrolytic plating film) made of, for example, copper or nickel.

Subsequently, the cavity C is formed in the resin insulating layer 10a by counterbore processing using a laser or the like, as shown in FIG. 3E. For example, by irradiating the inside of the peripheral edge of the conductor pattern 110 of the second conductor layer 11b with a laser beam, the place where the cavity C of the resin insulating layer 10a is formed is removed. In the formation of the cavity C, the conductor pattern 110 of the second conductor layer 11b provided at the position of the bottom surface C1 of the cavity C can function as a stopper layer. Therefore, the conductor pattern 110 is exposed on the bottom surface C1 of the cavity C after counterbore processing.

Next, the conductor pattern 110 is removed by etching or the like. As shown in FIG. 3F, a substrate 2a having a cavity C is obtained. The resin insulating layer 10b is exposed on the bottom surface C1 of the cavity C.

The method described in FIGS. 2B to 2D described above is applied, and the electronic component E is housed in the cavity C of the substrate 2a (FIGS. 3G to 3I). First, a semi-cured first adhesive layer 21 is formed on the bottom surface C1 of the cavity C (FIG. 3G). Next, a second adhesive material 22a for forming the second adhesive layer 22 is applied onto the semi-cured first adhesive layer 21 (FIG. 3H). After the electronic component E is placed on the second adhesive material 22a, the semi-cured first adhesive layer 21 and the second adhesive material 22a are cured (FIG. 3I). A wiring board 2 in which the electronic component E is housed in the cavity C via the first and second adhesive layers 21 and 22 can be formed without causing a problem such as misalignment.

For example, after the wiring board 2 shown in FIG. 3I is formed, the electronic component E may be sealed in the cavity C, and after the sealing, the electronic component E and the resin insulating layer 10a and the first conductor layer 11a are above. A build-up layer may be further formed (on the side opposite to the carrier plate 5).

Further, in the example of the wiring plate 2, the metal foil 51 and the carrier metal foil 52 are softened by heating the thermoplastic adhesive that adheres the two, and the joint portion in which the two are fixed at the edge is formed. It can be separated by excision or the like. Therefore, the carrier 50 can be removed from the wiring board 2 by separating the metal foil 51 and the carrier metal foil 52. The metal leaf 51 exposed by separation can be removed, for example, by etching. As a result, the build-up layer can be further laminated on the side of the wiring board 2 on which the carrier plate 5 is formed. A wiring board in which the electronic component E is well housed can be formed in the build-up layer.

The conditions and order of the manufacturing method described above can be changed as appropriate. Depending on the structure of the wiring board to be manufactured, some steps may be omitted or another step may be added. For example, the adhesive layer may be formed using an adhesive material that has good adhesiveness even in a semi-cured state in which the fluidity is reduced. In this case, the second adhesive material 22 for adhering the electronic component E to the first adhesive layer 21 may not be required.

The manufacturing method of the present embodiment can be applied to various wiring boards manufactured by a manufacturing method including a step of accommodating an electronic component in a cavity.

1, 2 Wiring board 1a, 2a Substrate 5 Carrier board C Cavity C1 Bottom surface of cavity E Electronic parts E1 Terminal surface of electronic parts E2 Lower side surface of electronic parts 10, 10a, 10b Resin insulating layer 11 Conductor layer 11a First conductor layer 11b 2nd conductor layer 110 Conductor pattern 12 Via conductor 21 1st adhesive layer 21a 1st adhesive material 22 2nd adhesive layer 22a 2nd adhesive material 50 Carrier 51 Metal foil 52 Carrier Metal foil

Claims (6)

Preparing the substrate on which the cavity is formed and
Containing electronic components in the cavity and
It is a manufacturing method of a wiring board provided with
Accommodating electronic components in the cavity
Forming a first adhesive layer at the bottom of the cavity and
To reduce the fluidity of the first adhesive layer and
Forming a second adhesive layer on the first adhesive layer having reduced fluidity, and
Placing an electronic component on the second adhesive layer and
It includes curing the first adhesive layer and the second adhesive layer. The method for manufacturing a wiring board according to claim 1.
Forming the first adhesive layer at the bottom of the cavity includes forming the first adhesive layer with a thickness of t1.
Forming the second adhesive layer on the first adhesive layer having reduced fluidity includes forming the second adhesive layer with a thickness of t2.
t1 and t2 are the formulas:
0.6 <t1 / (t1 + t2) <0.9
Meet. The method for manufacturing a wiring board according to claim 1.
Curing the first adhesive layer and the second adhesive layer includes heating the first adhesive layer and the second adhesive layer under vacuuming. The method for manufacturing a wiring board according to claim 1.
Decreasing the fluidity of the first adhesive layer includes semi-curing the first adhesive layer by light irradiation. The method for manufacturing a wiring board according to claim 2.
Forming the first adhesive layer with the thickness t1 and forming the second adhesive layer with the thickness t2 is such that the sum of t1 and t2 is 5 μm or more and 50 μm or less. It includes forming one adhesive layer and the second adhesive layer. The method for manufacturing a wiring board according to claim 1.
Forming the first adhesive layer at the bottom of the cavity and forming the second adhesive layer on the first adhesive layer having reduced fluidity are the first adhesive material and the second adhesive material. Includes each application by inkjet.

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