Antenna module

Abstract

The objective of this invention is to reduce transmission loss between electronic components and antenna patterns in an antenna module that already encapsulates electronic components and antenna patterns. The solution provided by this invention is an antenna module 100, comprising: a multilayer substrate 10, and electronic components 30 embedded in the multilayer substrate 10. The multilayer substrate 10 includes: an insulating layer 12 in which the electronic components 30 are embedded, an internal conductor layer 72, and an antenna layer 78. The internal conductor layer 72 includes a signal pattern S1 facing the main surface 31 of the electronic component 30 via the insulating layer 12. The antenna layer 78 includes an antenna pattern ANT1 connected to the signal pattern S1. The surface of the signal pattern S1 has a surface A1 on the side facing the main surface 31 of the electronic component 30, and a surface A2 on the opposite side. The surface roughness of surface A1 is smaller than that of surface A2.

Description

[Technical Field]

[0001] This invention relates to antenna modules. [Previous Technology]

[0002] Patent Document 1 discloses an antenna module that encapsulates electronic components such as an RFIC (Radio Frequency IC) and an antenna pattern. [Prior Art Documents] [Patent Documents]

[0003] Patent Document 1: Japanese Patent Publication No. 2022-533763 [Summary of the Invention]

[0004] (Problem to be solved by the invention) In such an antenna module, it is required to reduce the transmission loss between electronic components and antenna pattern.

[0005] The present invention provides a method to reduce transmission loss between electronic components and antenna patterns in an antenna module that encapsulates electronic components and antenna patterns. (Technical means to solve the problem)

[0006] One embodiment of the antenna module of the present invention comprises: a multilayer substrate having a plurality of conductor layers and a plurality of insulating layers alternately laminated thereon; and an electronic component having a plurality of pad electrodes including signal pads on its main surface side; the plurality of insulating layers including a first insulating layer in which the electronic component is embedded, and the plurality of conductor layers including a first inner conductor layer and an antenna layer; the first inner conductor layer including: a first signal pattern, one end of which is electrically connected to the signal pad, and at least a portion thereof is opposite to the main surface of the electronic component via the first insulating layer; the antenna layer including: an antenna pattern electrically connected to the other end of the first signal pattern; the surface of the first signal pattern having a first surface located on the side opposite to the main surface of the electronic component, and a second surface located on the opposite side of the first surface, wherein the surface roughness of the first surface is less than the surface roughness of the second surface. (Effects compared to prior art)

[0007] According to the present invention, a technique is provided to reduce transmission loss between electronic components and antenna patterns in an antenna module that encapsulates electronic components and antenna patterns.

Implementation Method

[0009] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0010] FIG1 is a schematic perspective view showing the appearance of an antenna module 100 according to an embodiment of the present invention. The antenna module 100 is flat and has four antenna patterns ANT1 to ANT4 disposed on its surface. A plurality of terminal electrodes are disposed on the back side of the antenna module 100.

[0011] Figure 2 is a partial schematic cross-sectional view of the antenna module 100. As shown in Figure 2, the antenna module 100 includes: a multilayer substrate 10 having a plurality of conductor layers 71-78 and a plurality of insulating layers 11-17 alternately laminated thereon; and electronic components 30 embedded in the multilayer substrate 10. Here, insulating layers 11, 13-17 are all core insulating layers, which are made of a core material formed by impregnating a core material with resin. In contrast, insulating layer 12 does not contain a core material that would hinder the embedding of the electronic components 30. Furthermore, insulating layers 13 and 14 may also be made of a material with a dielectric loss tangent smaller than that of insulating layer 12.

[0012] The outermost conductor layer 71 on one side is covered by solder resist 21. The outermost conductor layer 78 on the other side is covered by solder resist 22. Solder resist 21 forms the back surface 101 of the antenna module 100. A plurality of terminal electrodes, including signal terminals 41 and ground terminals 42, are exposed from the openings in the solder resist 21. The signal terminals 41 and ground terminals 42 are connected to the conductor layer 71. The conductor layer 71 forms a terminal layer, and the surface of the conductor layer 71 exposed from the solder resist 21 can also be used as a terminal electrode. The plurality of terminal electrodes can also be considered as part of the conductor layer 71. Solder resist 22 forms the surface 102 of the antenna module 100. Conductor layers 72-77 all form inner conductor layers.

[0013] Electronic component 30 is embedded in insulating layer 12. Insulating layer 12 is composed of two insulating layers 12A and 12B, and electronic component 30 is embedded between them. Electronic component 30 may be an RFIC chip. Electronic component 30 has: a main surface 31 on which circuit elements such as transistors are formed; a back surface 33 on the opposite side of main surface 31; a redistribution layer 32 disposed on main surface 31; and a plurality of pad electrodes disposed on redistribution layer 32. The plurality of pad electrodes includes signal pads P1, P2 and ground pads P3. Electronic component 30 is embedded in insulating layer 12 with main surface 31 facing back surface 101 and back surface 33 facing surface 102. In redistribution layer 32, in addition to signal patterns connected to signal pads P1, P2, etc., ground patterns may also be provided in most areas where no signal patterns are provided. Signal pad P1 is connected to one end of signal pattern S1 located on conductor layer 72 via through conductor V4. Signal pad P2 is connected to signal terminal 41. Ground pad P3 is connected to ground terminal 42 via through conductor V6 and ground pattern G1 located on conductor layer 72.

[0014] The other end of signal pattern S1 is connected to one end of signal pattern S2 located in conductor layer 74 via through conductor V1 penetrating insulating layer 12, signal pattern S3 located in conductor layer 73, and through conductor V5 penetrating insulating layer 13. The other end of signal pattern S2 is connected to antenna pattern ANT1 located in conductor layer 78 via through conductor V2 penetrating insulating layers 14-17. Other antenna patterns ANT2-ANT4 are also formed on conductor layer 78, which constitutes the antenna layer. Through conductor V2 is composed of a plurality of intervals, which are composed of through conductors V21-V24 penetrating insulating layers 14-17 respectively. Through conductors V21-V24 are arranged in positions that overlap when viewed from the stacking direction. Through conductor V22 is a cylindrical conductor pattern formed on the inner wall of the through hole penetrating insulating layer 15. The area surrounded by the through conductor V22 is filled with insulating resin 50.

[0015] With the above configuration, in the antenna module 100, the main surface 31 and redistribution layer 32 of the electronic component 30 and the emitting surface (A8, described below) of the antenna pattern ANT1 are arranged so that they do not face each other in the stacking direction (they face opposite directions in the stacking direction). Specifically, the main surface 31 and redistribution layer 32 of the electronic component 30 face the back surface 101 of the antenna module 100, while the emitting surface of the antenna pattern ANT1 faces the surface 102 of the antenna module 100. In this way, interference between the antenna patterns ANT1~ANT4 and the signal pads P1 and P2 of the electronic component 30 can be suppressed, thereby obtaining stable antenna characteristics.

[0016] Ground pattern G1 is connected to ground pattern G2, which is disposed on conductor layer 73, via a through conductor V3 that penetrates insulating layer 12. Viewed from the stacking direction, most of electronic component 30 overlaps with ground pattern G2. Ground pattern G2 is connected to ground pattern G4, located on conductor layer 74, via a through conductor V7 that penetrates insulating layer 13. Ground pattern G4 is connected to ground pattern G3, located on conductor layer 75, via a through conductor V8 that penetrates insulating layer 14. Most of signal pattern S2 is surrounded by ground patterns G2 and G3.

[0017] As shown in FIG. 2, the surface of the conductor layer 72 containing the signal pattern S1 has: surface A1, which is in contact with the insulating layer 12 and located on the side opposite to the main surface 31 of the electronic component 30; and surface A2, which is in contact with the insulating layer 11 and located on the opposite side of surface A1. The surface of the conductor layer 74 containing the signal pattern S2 has: surface A3, which is in contact with the insulating layer 13 and located on the side opposite to the ground pattern G2; and surface A4, which is in contact with the insulating layer 14 and located on the side opposite to the ground pattern G3. The surface of the conductor layer 73 containing the signal pattern S3 has: surface A5, which is in contact with the insulating layer 12 and located on the side opposite to the electronic component 30; and surface A6, which is in contact with the insulating layer 13 and located on the opposite side of surface A5. The surface of the conductor layer 78 containing the antenna pattern ANT1 has: a surface A7, which is in contact with the insulating layer 17 and located on the side in contact with the through conductor V2; and a surface A8, which is in contact with the solder resist 22 and located on the opposite side of surface A7.

[0018] The surface roughness of surface A1 of conductor layer 72 can be less than the surface roughness of surface A2 of conductor layer 72. Therefore, the transmission loss of RF signal flowing through signal pattern S1 is reduced. Since a portion of signal pattern S1 covers the main surface 31 of electronic component 30 through insulating layer 12, the impedance on surface A1 side is lower than that on surface A2 side due to the ground potential of electronic component 30 itself or the ground potential obtained by the ground pattern provided on redistribution layer 32. As a result, due to the skin effect, the current density flowing through the surface of signal pattern S1 is higher on surface A1 side than on surface A2 side. Therefore, if the surface roughness of surface A1 is set to be less than that of surface A2, the transmission loss of RF signal flowing near surface A1 of signal pattern S1 is reduced. On the other hand, the surface A2 side with lower current density has a larger surface roughness, thus its adhesion to insulating layer 11 is improved.

[0019] Insulating layer 13 can be thinner than insulating layer 14. In this case, the surface roughness of surface A3 of conductor layer 74 can be less than the surface roughness of surface A4 of conductor layer 74. Therefore, the transmission loss of RF signal flowing through signal pattern S2 is reduced. This is because when insulating layer 13 is thinner than insulating layer 14, the distance T13 between surface A3 of signal pattern S2 and ground pattern G2 is shorter than the distance T14 between surface A4 of signal pattern S2 and ground pattern G3. Therefore, the impedance on the surface A3 side is lower than the impedance on the surface A4 side. On the other hand, since surface A4 has a larger surface roughness, its engagement with insulating layer 14 is improved. Furthermore, if the materials of insulating layers 13 and 14 are made of materials with a dielectric loss tangent smaller than that of insulating layer 12, the transmission loss of RF signal flowing through signal pattern S2 will be further reduced.

[0020] The surface roughness of surface A5 of conductor layer 73 can be less than that of surface A6 of conductor layer 73. Therefore, the transmission loss of the RF signal flowing through signal pattern S3 is reduced. This is because surface A5 of signal pattern S3 faces the electronic component 30 side, and therefore, due to the ground potential of the electronic component 30 itself, the impedance on surface A5 side is lower than that on surface A6 side. On the other hand, surface A6 has a larger surface roughness, thus its adhesion to insulating layer 13 is improved.

[0021] The surface roughness of surface A8 of conductor layer 78 can be less than that of surface A7 of conductor layer 78. Therefore, the transmission loss of RF signal flowing through antenna pattern ANT1 is reduced. This is because the RF signal emitted from antenna pattern ANT1 is concentrated on the surface A8 side. On the other hand, surface A7 has a larger surface roughness, thus its engagement with insulating layer 17 is improved.

[0022] Figures 3A to 3K are process diagrams used to illustrate the manufacturing method of antenna module 100.

[0023] First, as shown in FIG3A, after forming the through-hole 51 in the insulating layer 15, a conductive member such as Cu is formed on the entire surface including the inner surface of the through-hole 51. Thereby, a conductor layer 75 is formed on the upper surface side of the insulating layer 15, a conductor layer 76 is formed on the lower surface side of the insulating layer 15, and a through conductor V22 is formed on the inner surface of the through-hole 51. Next, as shown in FIG3B, the space surrounded by the through conductor V22 is filled with insulating resin 50 for electrolytic plating, and the conductor layers 75 and 76 are patterned. Thereby, a grounding pattern G3 is formed on the conductor layer 75. Next, as shown in FIG3C, insulating layers 14 and 16, each covering the conductor layers 75 and 76, are formed. Then, through conductors V21 and V23, each penetrating the insulating layers 14 and 16, are formed, and conductor layers 74 and 77, respectively located on the surfaces of the insulating layers 14 and 16, are patterned. In this way, a signal pattern S2 and a ground pattern G4 are formed on the conductor layer 74.

[0024] Here, in order to make the surface roughness of the surface A3 of the conductor layer 74 less than the surface roughness of the surface A4 of the conductor layer 74, copper foil with a smaller surface roughness of surface A3 and a larger surface roughness of surface A4 can be pre-deposited on the insulating layer 14 to form the conductor layer 74. In this case, after the copper foil constituting the conductor layer 74 is deposited on the insulating layer 14, the surface A3 of the conductor layer 74 can be etched as needed to adjust the surface roughness of the surface A3 of the conductor layer 74.

[0025] Next, as shown in FIG3D, insulating layers 13 and 17 are formed, each covering the conductor layers 74 and 77. Then, through conductors V5 and V24 are formed, each penetrating the insulating layers 13 and 17, and conductor layers 73 and 78 located on the surfaces of the insulating layers 13 and 17 are patterned. Thereby, a signal pattern S3 and a ground pattern G2 are formed on conductor layer 73, and an antenna pattern ANT1 is formed on conductor layer 78. Conductor layer 78 is covered by solder resist 22.

[0026] Here, to make the surface roughness of surface A5 of conductor layer 73 less than the surface roughness of surface A6 of conductor layer 73, copper foil with a smaller surface roughness of surface A5 and a larger surface roughness of surface A6 can be deposited on insulating layer 13 in advance to form conductor layer 73. In this case, after depositing the copper foil constituting conductor layer 73 on insulating layer 13, surface A5 of conductor layer 73 can be etched as needed to adjust the surface roughness of surface A5 of conductor layer 73. Similarly, to make the surface roughness of surface A8 of conductor layer 78 less than the surface roughness of surface A7 of conductor layer 78, copper foil with a smaller surface roughness of surface A8 and a larger surface roughness of surface A7 can be deposited on insulating layer 17 in advance to form conductor layer 78. In this case, after depositing the copper foil constituting conductor layer 78 on insulating layer 17, surface A8 of conductor layer 78 can be etched as needed to adjust the surface roughness of surface A8 of conductor layer 78.

[0027] Next, as shown in FIG3E, after forming the insulating layer 12A covering the conductor layer 73, the electronic component 30 is mounted on the surface of the insulating layer 12A. Next, as shown in FIG3F, an insulating layer 12B and a conductor layer 72 are formed on the surface of the insulating layer 12A to embed the electronic component 30. Here, in order to make the surface roughness of the surface A1 of the conductor layer 72 less than the surface roughness of the surface A2 of the conductor layer 72, the surface A2 of the conductor layer 72 can be roughened by etching after the insulating layer 12B on which the copper foil constituting the conductor layer 72 is attached is deposited on the surface of the insulating layer 12A.

[0028] Next, as shown in FIG3G, the conductor layer 72 formed on the surface of the insulating layer 12B is patterned, and through holes 61 and 62 are formed in the insulating layers 12A and 12B using the patterned conductor layer 72 as a mask. The through hole 61 is configured to penetrate the insulating layers 12A and 12B, and the conductor layer 73 is exposed on its bottom surface. The through hole 62 is located at a position overlapping with the electronic component 30, and the solder pad electrode is exposed on its bottom surface.

[0029] Next, as shown in FIG3H, through-holes 61 and 62 are filled with conductive members, and the conductor layer 72 is patterned. This forms through conductors V1 and V3, and a signal pattern S1 and a ground pattern G1 are formed on the conductor layer 72. Next, as shown in FIG3I, an insulating layer 11 is formed covering the conductor layer 72. Then, through conductors are formed through the insulating layer 11, and the conductor layer 71 located on the surface of the insulating layer 11 is patterned. Next, as shown in FIG3J, after covering the conductor layer 71 with solder resist 21, as shown in FIG3K, an opening 63 is formed in the solder resist 21. Then, by forming terminal electrodes in the opening 63, the structure shown in FIG2 can be obtained.

[0030] Thus, in the antenna module 100 of this embodiment, the surface roughness of the surface with higher current density on the surface of the signal patterns S1-S3 and antenna pattern ANT1 through which RF signals flow is reduced. For example, regarding signal pattern S1 and signal pattern S2 which is electrically connected to S1 via the through conductor V1, the surface roughness of the side with higher current density is reduced based on the ground pattern of the electronic component 30 (specifically, the ground pattern formed on the redistribution layer 32). This reduces the transmission loss of the RF signal. On the other hand, since the surface of the signal patterns S1-S3 and antenna pattern ANT1 through which RF signals flow is roughened, their adhesion to the insulating layer can be ensured. Moreover, since signal pattern S2 is shielded by the upper and lower ground patterns G2 and G3, crosstalk between antenna patterns ANT1-ANT4 via signal pattern S2 is also reduced.

[0031] Figure 4 is a partial schematic cross-sectional view of the antenna module of the modified example.

[0032] The modified antenna module shown in Figure 4 differs from the structure shown in Figure 2 in that the insulating layer 14 is thinner than the insulating layer 13. In this case, the surface roughness of surface A4 of conductor layer 74 can be less than the surface roughness of surface A3 of conductor layer 74. Therefore, the transmission loss of the RF signal flowing through signal pattern S2 can be reduced. This is because when the insulating layer 14 is thinner than the insulating layer 13, the distance T14 between surface A4 of signal pattern S2 and ground pattern G2 becomes shorter than the distance T13 between surface A3 of signal pattern S2 and ground pattern G3. Therefore, the impedance on the surface A4 side is lower than the impedance on the surface A3 side. On the other hand, since surface A3 has a larger surface roughness, its engagement with insulating layer 13 is improved.

[0033] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Various modifications can be made without departing from the spirit of the present invention, and such modifications are of course included within the scope of the present invention.

[0034] The technology of the present invention includes the following configuration examples, but is not limited thereto.

[0035] One embodiment of the antenna module of the present invention comprises: a multilayer substrate having a plurality of conductor layers and a plurality of insulating layers alternately laminated thereon; and an electronic component having a plurality of pad electrodes including signal pads on its main surface side; the plurality of insulating layers including a first insulating layer in which the electronic component is embedded; the plurality of conductor layers including a first inner conductor layer and an antenna layer; the first inner conductor layer including: a first signal pattern, one end of which is electrically connected to the signal pad, and at least a portion thereof facing the main surface of the electronic component via the first insulating layer; the antenna layer including: an antenna pattern electrically connected to the other end of the first signal pattern; the surface of the first signal pattern having a first surface on the side facing the main surface of the electronic component and a second surface on the opposite side of the first surface, the surface roughness of the first surface being less than the surface roughness of the second surface. Therefore, it can ensure the interlocking of the conductor layer and the insulating layer and reduce the transmission loss between the electronic component and the antenna pattern.

[0036] In the above-described antenna module, it may also comprise a plurality of conductor layers, further including a second inner conductor layer, the second inner conductor layer comprising: a second signal pattern, one end of which is electrically connected to the other end of the first signal pattern via a first through conductor penetrating the first insulating layer, and the other end of which is electrically connected to an antenna pattern via a second through conductor. Therefore, the antenna pattern can be disposed on the back side of the electronic component.

[0037] In the above-described antenna module, the antenna pattern may also have a 7th surface located on the side connected to the 2nd through conductor, and an 8th surface located on the opposite side of the 7th surface. The back surface located on the opposite side of the main surface of the electronic component faces the 7th surface of the antenna pattern, and the main surface of the electronic component faces the 8th surface of the antenna pattern. Therefore, since interference between the antenna pattern and the signal pads of the electronic component can be suppressed, stable antenna characteristics can be obtained. In this case, the surface roughness of the 8th surface may be less than that of the 7th surface. Therefore, the transmission loss of the RF signal flowing through the antenna pattern is reduced.

[0038] In the above-mentioned antenna module, the plurality of conductor layers may further include: a third inner conductor layer located between the second inner conductor layer and the first insulating layer; and a fourth inner conductor layer located between the second inner conductor layer and the antenna layer; the plurality of insulating layers may further include: a second insulating layer located between the second inner conductor layer and the third inner conductor layer; and a third insulating layer located between the second inner conductor layer and the fourth inner conductor layer; the third inner conductor layer includes a first ground pattern that overlaps with the second signal pattern when viewed from above, the fourth inner conductor layer includes a second ground pattern that overlaps with the second signal pattern when viewed from above, and the plurality of pad electrodes may further include ground pads; the first ground pattern, the second ground pattern, and the ground pads are electrically connected to each other. Therefore, the second signal pattern is shielded by being sandwiched between the first ground pattern and the second ground pattern.

[0039] In the above-described antenna module, the second insulating layer may be thinner than the third insulating layer, and the surface of the second signal pattern may have a third surface in contact with the second insulating layer and a fourth surface in contact with the third insulating layer, wherein the surface roughness of the third surface is less than that of the fourth surface. Therefore, the transmission loss of the RF signal flowing through the second signal pattern is reduced. Alternatively, the third insulating layer may be thinner than the second insulating layer, and the surface of the second signal pattern may have a third surface in contact with the second insulating layer and a fourth surface in contact with the third insulating layer, wherein the surface roughness of the fourth surface is less than that of the third surface. Therefore, the transmission loss of the RF signal flowing through the second signal pattern is reduced.

[0040] In the above-mentioned antenna module, the second and third insulating layers may also be made of a material with a dielectric loss tangent smaller than that of the first insulating layer. Therefore, the transmission loss of the RF signal flowing through the second signal pattern is further reduced.

[0041] In the above-described antenna module, the third internal conductor layer may further include a third signal pattern. The third signal pattern is connected to the other end of the first signal pattern via the first through conductor and to one end of the second signal pattern via the third through conductor. The surface of the third signal pattern has a fifth surface located on the side opposite to the first insulating layer and a sixth surface located on the opposite side of the fifth surface. The surface roughness of the fifth surface is less than the surface roughness of the sixth surface. Therefore, the transmission loss of the RF signal flowing through the third signal pattern is reduced. [Simplified Explanation of the Diagram]

[0008] FIG1 is a schematic perspective view showing the appearance of an antenna module 100 according to an embodiment of the present invention. FIG2 is a partial schematic cross-sectional view of the antenna module 100. FIG3A to FIG3K are process diagrams illustrating the manufacturing method of the antenna module 100. FIG4 is a partial schematic cross-sectional view of a modified antenna module.

Claims

1. An antenna module comprising: a multilayer substrate having a plurality of conductor layers and a plurality of insulating layers alternately laminated thereon; and an electronic component having a plurality of pad electrodes including signal pads on a main surface side; the plurality of insulating layers including a first insulating layer in which the electronic component is embedded; the plurality of conductor layers including a first inner conductor layer and an antenna layer; the electronic component having a back surface located opposite to the main surface; the electronic component being embedded in the first insulating layer with the main surface facing the first inner conductor layer and the back surface facing the antenna layer; the first inner conductor layer including: a first signal pattern, one end of which is electrically connected to the signal pads, and at least a portion of which is opposite to the main surface of the electronic component via the first insulating layer; and the antenna layer including: an antenna pattern electrically connected to the other end of the first signal pattern. The surface of the first signal pattern has a first surface located on the side opposite to the main surface of the electronic component, and a second surface located on the opposite side of the first surface. The surface roughness of the first surface is less than that of the second surface.

2. As in request item 1, the antenna module, wherein, The plurality of conductor layers further include a second inner conductor layer, which includes a second signal pattern, one end of which is electrically connected to the other end of the first signal pattern via a first through conductor penetrating the first insulating layer, and the other end of which is electrically connected to the antenna pattern via a second through conductor.

3. The antenna module as described in request item 2, wherein, The antenna pattern has a 7th surface located on the side connected to the 2nd through conductor and an 8th surface located on the opposite side of the 7th surface. The back surface of the electronic component and the 7th surface of the antenna pattern are opposite to each other, and the main surface of the electronic component and the 8th surface of the antenna pattern are opposite to each other.

4. The antenna module as described in request item 3, wherein, The surface roughness of the eighth surface is less than that of the seventh surface.

5. The antenna module as described in any of requests 2 to 4, wherein, The plurality of conductor layers further include: a third inner conductor layer located between the second inner conductor layer and the first insulating layer; and a fourth inner conductor layer located between the second inner conductor layer and the antenna layer; the plurality of insulating layers further include: a second insulating layer located between the second inner conductor layer and the third inner conductor layer; and a third insulating layer located between the second inner conductor layer and the fourth inner conductor layer; the third inner conductor layer includes a first ground pattern that overlaps with the second signal pattern in plan view; the fourth inner conductor layer includes a second ground pattern that overlaps with the second signal pattern in plan view; the plurality of pad electrodes further include ground pads; the first ground pattern, the second ground pattern, and the ground pads are electrically connected to each other.

6. The antenna module as described in request item 5, wherein, The second insulating layer is thinner than the third insulating layer. The surface of the second signal pattern has a third surface in contact with the second insulating layer and a fourth surface in contact with the third insulating layer. The surface roughness of the third surface is less than that of the fourth surface.

7. The antenna module as described in claim 5, wherein, The third insulating layer is thinner than the second insulating layer. The surface of the second signal pattern has a third surface in contact with the second insulating layer and a fourth surface in contact with the third insulating layer. The surface roughness of the fourth surface is less than that of the third surface.

8. The antenna module as described in request item 5, wherein, The second and third insulating layers mentioned above are made of materials with a dielectric loss tangent smaller than that of the first insulating layer.

9. The antenna module as described in claim 5, wherein, The third inner conductor layer further includes a third signal pattern, which is connected to the other end of the first signal pattern via the first through conductor and to one end of the second signal pattern via the third through conductor. The surface of the third signal pattern has a fifth surface located on the side opposite to the first insulating layer and a sixth surface located on the opposite side of the fifth surface. The surface roughness of the fifth surface is less than the surface roughness of the sixth surface.

Images