Antenna substrate and method of manufacturing same

1. An antenna substrate comprising:

a cap substrate including a first insulating layer and a plurality of first antenna conductors arranged in vertical and horizontal directions on upper and lower surfaces of the first insulating layer, the plurality of first antenna conductors being positioned opposite to each other with the first insulating layer therebetween;

a frame substrate including a second insulating layer and a plurality of openings located in the second insulating layer, each of the plurality of openings having an outer periphery that surrounds an individual or a collective number of outer peripheries of the plurality of first antenna conductors in a top view;

a base substrate including a third insulating layer and a plurality of second antenna conductors located on an upper surface of the third insulating layer;

a first adhesive material provided between a lower surface of the first insulating layer and an upper surface of the second insulating layer in a region other than a region where the opening is located, the first adhesive material adhering the first insulating layer and the second insulating layer to each other; and

a second adhesive material provided between a lower surface of the second insulating layer and the upper surface of the third insulating layer in a region other than a region where the opening is located, the second adhesive material adhering the second insulating layer and the third insulating layer to each other, wherein

each of the first adhesive material and the second adhesive material at least includes a plurality of first bonding members and a second bonding member, the plurality of first bonding members being located outside a region where the first antenna conductor is disposed, the second bonding member being partially in contact with the plurality of first bonding members, the second bonding member having an adhesive strength to the second insulating layer greater than that of the first bonding members.

2. The antenna substrate according to claim 1 , wherein the first bonding member includes at least one of solid particles and solid fibers in at least one of the first adhesive material and the second adhesive material.

3. The antenna substrate according to claim 1 , wherein the first bonding member includes at least one of solid particles and solid fibers in both the first adhesive material and the second adhesive material.

4. The antenna substrate according to claim 1 , wherein the first antenna conductors overlap each other on the upper and lower surfaces of the first insulating layer in a top view.

5. The antenna substrate according to claim 4 , wherein, in the plurality of first antenna conductors on the upper surface of the first insulating layer and the plurality of first antenna conductors on the lower surface of the first insulating layer, a first antenna conductor on the upper surface and a first antenna conductor on the lower surface disposed opposite each other with the first insulating layer therebetween have an identical shape and an identical dimension.

6. The antenna substrate according to claim 1 , wherein the opening sandwiched between the cap substrate and the base substrate is a cavity serving as a path for transmitting and receiving electromagnetic waves for signals between the first antenna conductor and the second antenna conductor.

7. A method of manufacturing an antenna substrate, the method comprising:

preparing a cap substrate including a first insulating layer and a plurality of first antenna conductors, the plurality of first antenna conductors being arranged in vertical and horizontal directions with a distance between each pair of adjacent first antenna conductors on upper and lower surfaces of the first insulating layer so to be opposite to each other with the first insulating layer therebetween;

preparing a frame substrate including a second insulating layer and an opening located in the second insulating layer, the opening having an outer periphery that surrounds an individual of or a collective number of outer peripheries of the plurality of first antenna conductors in a top view;

preparing a base substrate including a third insulating layer and a plurality of second antenna conductors disposed on an upper surface of the third insulating layer;

disposing a first bonding member in a region other than a region where the opening is located between a lower surface of the first insulating layer and an upper surface of the second insulating layer and between a lower surface of the second insulating layer and the upper surface of the third insulating layer, disposing the frame substrate and the cap substrate in an order of the frame substrate first and the cap substrate second on the base substrate with the first bonding member between the frame substrate and the cap substrate, and temporarily fixing the frame substrate and the cap substrate to the base substrate, and

disposing a second bonding member partially making contact with the first bonding member between the lower surface of the first insulating layer and the upper surface of the second insulating layer and between the lower surface of the second insulating layer and the upper surface of the third insulating layer, and permanently fixing the base substrate, the frame substrate, and the cap substrate with the second bonding member.

8. The method of manufacturing an antenna substrate according to claim 7 , wherein a bonding member containing at least one of solid particles and solid fibers is used as the first bonding member.