Method of producing a radio frequency member
A method of producing a radio frequency member to construct a radio frequency confinement device based on a waffle iron structure includes providing an intermediate work of a plate shape or a block shape, the intermediate work including a main surface which is shaped as a plane or a curved surface and a plurality of rods extending away from the main surface. An interval between a side surface of one of the plurality of rods and a side surface of another rod that is adjacent to the one rod monotonically increases in a direction away from the main surface. The method also includes forming an electrically-conductive plating layer on the main surface and at least the side surface of the plurality of rods by immersing at least a portion of the intermediate work in plating solution.
1. A method of producing a radio frequency member of a radio frequency confinement device with a waffle iron structure, the radio frequency confinement device being used for a ridge waveguide device or an antenna device including such a ridge waveguide device, or used with an electric circuit including a monolithic microwave integrated circuit (MMIC), the method comprising:
providing an intermediate work of a plate shape or a block shape, the intermediate work including a main surface which is shaped as a plane or a curved surface and a plurality of rods extending away from the main surface, wherein an interval between a side surface of one of the plurality of rods and a side surface of another rod that is adjacent to the one rod monotonically increases in a direction away from the main surface; and
forming an electrically-conductive plating layer on the main surface and at least the side surface of the plurality of rods by immersing at least a portion of the intermediate work in a plating solution; wherein
the plurality of rods define at least a portion of the waffle iron structure; and
a width of each of the plurality of rods is smaller than λm/2, where λm is a wavelength, in free space, of an electromagnetic wave having a highest frequency in an operating frequency hand of the radio frequency member.
2. The method of producing a radio frequency member of claim 1 , wherein
the side surface of each of the plurality of rods connects, at a root thereof, to the main surface via a first curved surface; and
a radius of curvature of the first curved surface is greater than a radius of curvature of a portion at which an upper surface of each of the plurality of rods connects to the side surface.
3. The method of producing a radio frequency member of claim 1 , wherein
the intermediate work includes a ridge extending along the main surface;
the ridge includes an upper surface on an apex thereof, the upper surface being flat and stripe-shaped;
a side surface of the ridge is surrounded by at least some of the plurality of rods; and
a distance between the side surface of the ridge and the side surface of each of the rods which surround the side surface of the ridge monotonically increases in the direction away from the main surface.
4. The method of producing a radio frequency member of claim 1 , wherein
the side surface of each of the plurality of rods connects, at a root thereof, to the main surface via a first curved surface;
a radius of curvature of the first curved surface is greater than a radius of curvature of a portion at which an upper surface of each of the plurality of rods connects to the side surface thereof;
the intermediate work includes a ridge extending along the main surface;
the ridge includes an upper surface on an apex thereof, the upper surface being flat and stripe-shaped;
a side surface of the ridge is surrounded by at least some of the plurality of rods; and
a distance between the side surface of the ridge and the side surface of each of the rods which surround the side surface of the ridge monotonically increases in the direction away from the main surface.
5. The method of producing a radio frequency member of claim 1 , wherein
the intermediate work includes a ridge extending along the main surface;
the ridge includes an upper surface on an apex thereof, the upper surface being flat and stripe-shaped;
a side surface of the ridge is surrounded by at least some of the plurality of rods;
a distance between the side surface of the ridge and the side surface of each of the rods which surround the side surface of the ridge monotonically increases in the direction away from the main surface;
the side surface of the ridge connects, at a root thereof, to the main surface via a second curved surface; and
a radius of curvature of the second curved surface is greater than a radius of curvature of a portion at which the upper surface of the ridge connects to the side surface of the ridge.
6. The method of producing a radio frequency member of claim 3 , wherein
the forming the plating layer includes forming an electrically-conductive plating layer on the side surface of the ridge and the upper surface of the ridge; and
a thickness of a portion of the plating layer that covers the upper surface of the ridge is greater than a thickness of a portion of the plating layer that covers the main surface of the intermediate work located between a root of the ridge and rods that are adjacent to the ridge.
7. The method of producing a radio frequency member of claim 1 , wherein
the intermediate work includes a ridge extending along the main surface;
the ridge includes an upper surface on an apex thereof, the upper surface being flat and stripe-shaped;
a side surface of the ridge is surrounded by at least some of the plurality of rods;
a distance between the side surface of the ridge and the side surface of each of the rods which surround the side surface of the ridge monotonically increases in the direction away from the main surface;
the side surface of the ridge connects, at a root thereof, to the main surface via a second curved surface;
a radius of curvature of the second curved surface is greater than a radius of curvature of a portion at which the upper surface of the ridge connects to the side surface of the ridge;
the forming the plating layer includes forming an electrically-conductive plating layer on the side surface and an upper surface of the ridge; and
a thickness of a portion of the plating layer that covers the upper surface of the ridge is greater than a thickness of a portion of the plating layer that covers the main surface of the intermediate work located between a root of the ridge and rods that are adjacent to the ridge.
8. The method of producing a radio frequency member of claim 1 , wherein
each of the plurality of rods includes a flat upper surface;
the side surface of each of the plurality of rods connects, at a root thereof, to the main surface via a first curved surface;
a radius of curvature of the first curved surface is greater than a radius of curvature of a portion at which an upper surface of each of the plurality of rods connects to the side surface;
the intermediate work includes a ridge extending along the main surface;
the ridge includes an upper surface on an apex thereof, the upper surface of the ridge being flat and stripe-shaped;
a side surface of the ridge is surrounded by at least some of the plurality of rods; and
a distance between the side surface of the ridge and the side surface of each of the rods which surround the side surface of the ridge monotonically increases in the direction away from the main surface.
9. The method of producing a radio frequency member of claim 1 , wherein the intermediate work is placed with an attitude such that, when immersed in the plating solution, the main surface extends in a direction which is parallel to the direction of gravity or which forms an angle of 45 degrees or smaller with the direction of gravity.
10. The method of producing a radio frequency member of claim 1 , wherein
the intermediate work includes a ridge extending along the main surface;
the ridge includes an upper surface on an apex thereof, the upper surface of the ridge being flat and stripe-shaped;
a side surface of the ridge is surrounded by at least some of the plurality of rods;
a distance between the side surface of the ridge and the side surface of each of the rods which surround the side surface of the ridge monotonically increases in the direction away from the main surface;
the side surface of the ridge connects, at a root thereof, to the main surface via a second curved surface;
a radius of curvature of the second curved surface is greater than a radius of curvature of a portion at which the upper surface of the ridge connects to the side surface of the ridge;
the forming the plating layer includes forming an electrically-conductive plating layer on the side surface and the upper surface of the ridge;
a thickness of a portion of the plating layer that covers the upper surface of the ridge is greater than a thickness of a portion of the plating layer that covers the main surface of the intermediate work located between the root of the ridge and rods that are adjacent to the ridge; and
the intermediate work is placed with an attitude such that, when immersed in the plating solution, the main surface extends in a direction which is parallel to the direction of gravity or which forms an angle of 45 degrees or smaller with the direction of gravity.
11. The method of producing a radio frequency member of claim 8 , wherein,
the providing the intermediate work includes performing an injection molding to provide the intermediate work being made of a resin;
dies which are used in the injection molding include:
one or more side surface dies defining an air gap including an inner peripheral surface of a same shape as the side surface of the ridge; and
one or more end surface dies including a surface of a same shape as the upper surface of the ridge; and
the injection molding is performed while an end of the air gap defined by the one or more side surface dies is occluded by the one or more end surface dies.
12. The method of producing a radio frequency member of claim 1 , wherein the interval between the side surface of one of the plurality of rods and the side surface of another rod that is adjacent to the one rod is less than 2 mm.
13. The method of producing a radio frequency member of claim 1 , wherein
the side surfaces of each of the plurality of rods is connected, at a root thereof, to the main surface via a first curved surface;
a radius of curvature of the first curved surface is greater than a radius of curvature of a portion at which an upper surface of each of the plurality of rods connects to the side surface;
the intermediate work includes a ridge extending along the main surface;
the ridge includes an upper surface on an apex thereof, the upper surface of the ridge being flat and stripe-shaped;
a side surface of the ridge is surrounded by at least some of the plurality of rods;
a distance between the side surface of the ridge and the side surface of each of the rods which surround the side surface of the ridge monotonically increases in the direction away from the main surface; and
the interval between the side surface of one of the plurality of rods and the side surface of another rod that is adjacent to the one rod is less than 2 mm.
14. The method of producing a radio frequency member of claim 6 , wherein an angle of contact of the plating solution with a surface of a portion of the intermediate work is greater than 0 degrees and smaller than 90 degrees.