Patent Description:
In recent years, a technology relating to a wiring substrate where semiconductor elements or the like are mounted has been attracted attention due to speeding-up and increased capacity of communication. Copper is usually used for a transmission path of the wiring substrate, and there is a case when a nickel-phosphorus layer is deposited on a surface of copper, and a gold layer is further deposited on a surface of the nickel-phosphorus layer.

In recent years, in an antenna device dealing with millimeter waves and microwaves, a microstrip antenna excellent in mass productivity and economic efficiency is widely used because it is possible to form in a planar shape on a substrate by using an integrated-circuit technology or a printed-wiring technology.

Copper is usually used for a radiation element and a ground conductor plate of the microstrip antenna. There is a case when a structure where a nickel-phosphorus layer and a gold layer are sequentially deposited on copper is used. The microstrip antenna transmits and receives high-frequency signals in millimeter-wave and microwave bands through the radiation element.

<CIT> discloses a technology where a loss of a high-frequency signal is reduced by setting a concentration of phosphorus of the nickel-phosphorus layer to <NUM> to <NUM>% to cause non-magnetization of nickel. It is possible to improve transmission characteristics and gain at a transmission/reception time also in the transmission path and the antenna device owing to the technology as stated above. Further, <CIT> discloses a high-frequency transmission line disposed along a surface of an insulating support. <CIT> discloses a high-frequency transmission line having low alternate current (AC) resistance is disposed along a surface of an insulating support, wherein, letting F [Hz] be the frequency of an AC electric signal transmitted by the high-frequency transmission line and Ms [Wb/m] be the saturation magnetization per unit area, the frequency value F and the saturation magnification value per unit area Ms satisfy the following expression (<NUM>): Mss≤(<NUM>×<NUM><NUM>)/F+<NUM>×<NUM>-<NUM>. <CIT> discloses a waveguide which consists of electrically and thermally highly conductive metal and, on its inner surface, has a coating consisting of a metal or a metal alloy having a considerably lower electrical conductivity. <CIT> discloses a wiring structure wherein irregularities whose maximum roughness is about <NUM> pm are formed in a vertical direction to the transmission direction of an interaction on the surface faced with a grounding conductor <NUM> of a signal line <NUM> formed on an insulator <NUM>. Its value is sufficiently large when it is taken into consideration that the thickness S of a surface film at <NUM> is <NUM> pm, and it contributes largely to reduction of a conductor loss due to an increase in the surface area of a conductor. In addition, irregularities whose maximum roughness is about <NUM> pm are formed in a direction parallel to the transmission direction. Its value corresponds to only <NUM>/<NUM> of a wavelength of <NUM> at <NUM>, and an increase is a loss due to reflected waves of a characteristic impedance caused by the uneven parts of a transmission line is hardly generated. That is to say, the insertion loss of an interconnection is reduced largely so as to be suppressed to a loss of about <NUM>% at <NUM>. Irregularities along the direction of an interconnection are formed on a face faced with the grounding conductor of the signal line, and the conductor loss is reduced without increasing a conductor width.

It became clear through actual measurement performed by the present inventors that a loss increased when a frequency of a signal was over <NUM> according to the technology disclosed in <CIT>.

The present invention is made in consideration of the aforementioned circumstances, and an object of the present invention is to provide an alternative to the waveguide disclosed in <CIT>.

To solve the aforementioned problems, the present invention provides a transmission path according to claim <NUM>. Embodiments of the transmission path are described in the dependent claims.

According to the present invention, it is possible to provide an alternative waveguide with little loss even when a signal at a frequency of over <NUM> is transmitted.

Next, illustrative examples will be explained.

<FIG> is a view illustrating a configuration example of a first illustrative example. The first illustrative example illustrated in <FIG> illustrates a configuration of a part of a server used in, for example, a data center or the like. The first illustrative example illustrated in <FIG> includes a backplane substrate <NUM> and unit substrates <NUM>, <NUM>. Here, the backplane substrate <NUM> includes a dielectric substrate <NUM>, a transmission path <NUM>, vias <NUM>, <NUM>, and connectors <NUM>, <NUM>.

Here, the dielectric substrate <NUM> is formed by a dielectric plate-like member. The transmission path <NUM> transmits digital signals between the connectors <NUM>, <NUM>. The vias <NUM>,<NUM> penetrating through the dielectric substrate <NUM> are formed at both end parts of the transmission path <NUM>. The connectors <NUM>, <NUM> where the unit substrates <NUM>, <NUM> are connected are provided at an upper part (an upside in <FIG>) of the dielectric substrate <NUM>. Transmission paths <NUM>, <NUM> which connect between transmission paths <NUM>, <NUM> provided at each inside of the unit substrates <NUM>, <NUM> and the transmission path <NUM> provided at an inside of the backplane substrate <NUM> are respectively provided at insides of the connectors <NUM>, <NUM>.

The unit substrate <NUM> includes a dielectric substrate <NUM>, where the transmission path <NUM> is provided, and vias <NUM>, <NUM> penetrating through the dielectric substrate <NUM> are formed at both end parts of the transmission path <NUM>. An IC (integrated circuit) chip <NUM> is mounted on the dielectric substrate <NUM>, and a non-illustrated connection terminal of the IC chip <NUM> is connected to the transmission path <NUM> through the via <NUM>. The transmission path <NUM> is connected to the transmission path <NUM> at the inside of the connector <NUM> through the via <NUM>.

The unit substrate <NUM> includes a dielectric substrate <NUM>, where the transmission path <NUM> is provided, and vias <NUM>, <NUM> penetrating through the dielectric substrate <NUM> are formed at both end parts of the transmission path <NUM>. An IC chip <NUM> and a circuit element <NUM> such as a capacitor are mounted on the dielectric substrate <NUM>. A non-illustrated connection terminal of the IC chip <NUM> is connected to the transmission path <NUM> through the via <NUM>. The transmission path <NUM> is connected to the transmission path <NUM> at the inside of the connector <NUM> through the via <NUM>.

According to the configuration illustrated in <FIG>, the unit substrate <NUM> operates as a transmission side, the unit substrate <NUM> operates as a reception side, and digital signals are transmitted from the unit substrate <NUM> toward the unit substrate <NUM> through the transmission paths <NUM>, <NUM>, <NUM>. It goes without saying that a reverse operation may be performed.

In the first illustrative example, a nickel-phosphorous layer is applied to the backplane substrate <NUM> and the transmission paths <NUM>, <NUM> which are provided at the unit substrates <NUM>, <NUM>. That is, the transmission paths <NUM>, <NUM> are formed by depositing a plurality of conductor layers on the dielectric substrates <NUM>, <NUM>. In more detail, a copper layer, a nickel-phosphorus layer, and a gold layer are deposited in a stacked state. A content ratio of phosphorus contained in the nickel-phosphorus layer is set to <NUM> mass% (hereinafter, "mass" is accordingly omitted and just denoted as "%") or more and less than <NUM> mass%, and it is thereby possible to reduce transmission loss with respect to a frequency of over <NUM>.

<FIG> is a view illustrating a structural example of a test sample which was used when a loss of a transmission path according to the present illustrative example was actually measured. The test sample illustrated in <FIG> has a structure as same as the transmission paths <NUM>, <NUM> in <FIG>. In an example in <FIG>, the test sample is prepared by forming copper layers <NUM>, <NUM> each as a conductor layer by adhering a copper foil with a thickness of about <NUM> pm on each of both surfaces of the PTFE (poly tetra fluoro ethylene)-based dielectric substrate <NUM> with a thickness of about <NUM>, and subjecting the substrate to an etching process and a through-hole plating treatment. Next, nickel-phosphorus plating is performed by means of electroless plating on surfaces of the copper layers <NUM>, <NUM> to form nickel-phosphorus layers <NUM>, <NUM> each with a thickness of about <NUM> pm. At this time, a concentration of a plating solution is set such that a concentration of phosphorus of each of the nickel-phosphorus layers <NUM>, <NUM> becomes <NUM> mass% or more and less than <NUM> mass%. Next, gold layers <NUM>, <NUM> each with a thickness of about <NUM> are formed on surfaces of the nickel-phosphorus layers <NUM>, <NUM> by means of gold plating. In <FIG>, one formed on an upper side surface of the dielectric substrate <NUM> is the transmission path <NUM> or <NUM>, and one formed on a lower side surface is a ground layer <NUM>.

<FIG> illustrates results of actual measurement of a transmission loss at each frequency when each phosphorus content concentration of the nickel-phosphorus layers <NUM>, <NUM> was changed in the test sample illustrated in <FIG>. In more detail, <FIG> is the results where the loss of the transmission path of the test sample per <NUM> was actually measured while changing the phosphorus content concentration and the frequency.

The phosphorus concentration was measured by dissolving the nickel-phosphorus layer in a nitric acid solution, and subjecting the solution to mass spectrometry by using an inductively coupled plasma atomic emission spectroscopy (manufactured by Shimadzu Corporation, ICPS-<NUM> or the like), or mass spectrometry by EDS (energy dispersive X-ray spectrometry) analysis of a layer cross section, and the thickness of the nickel-phosphorus layer was measured by using a fluorescence X-ray film thickness meter (manufactured by Seiko Instruments Inc. , SFT3200 or the like). Measurement of electric properties was performed by using a network analyzer as described later, and the properties of the sample were judged by measuring the transmission loss.

Here, the transmission loss indicates a ratio of transmittable signals without loss, reflection, and radiation in a sample transmission path by passing high-frequency signals through a test piece. It is judged that the smaller a value of the transmission loss is, the better the properties are. Later-described graphs and tables are represented by values in minus, and in this case, the properties are judged to be good as the values are larger.

As listed in <FIG>, it became clear as a result of the actual measurement that when the phosphorus concentrations were <NUM>, <NUM>, <NUM> mass%, each loss became smaller compared to other concentrations at the frequency higher than <NUM>. That is, when the frequency was <NUM>, each loss became smaller when the phosphorus concentrations were <NUM>, <NUM>, <NUM>% compared to the case when the phosphorus concentration was <NUM> to <NUM>% (-<NUM> dB to -<NUM> dB became -<NUM> dB). However, it became clear that when the frequency became higher, the loss did not change even when the phosphorus concentration changed at <NUM> (the loss was constant to be -<NUM> dB independent from the phosphorus concentration), and each loss became smaller when the phosphorus content concentration was <NUM> to <NUM>% compared to the cases when the phosphorus content concentrations were <NUM>,<NUM>, <NUM>, <NUM>% at <NUM> or more. As a relation between the transmission loss at <NUM> and the phosphorus concentration is illustrated in <FIG>, it can be seen that the transmission loss becomes rapidly smaller when the concentration is below <NUM>%.

It is possible to reduce the loss of the high-frequency signal by using the transmission paths each having the structure similar to <FIG> for the transmission paths <NUM>, <NUM> illustrated in <FIG> and setting the phosphorus concentration of the nickel-phosphorus layer to <NUM> to <NUM>%.

<FIG> illustrates simulation results of an eye-opening height when signals of <NUM> to <NUM> Gbaud were input at <NUM> Vpp to a transmission line having the structure similar to <FIG> with a length of <NUM>. Note that the eye-opening height can be found from an average value at level <NUM>, an average value at level "<NUM>" (zero) which are each calculated while complying with a standard of IEEE802. <NUM> as illustrated in <FIG>, <FIG> σ<NUM> (standard deviation noise at <NUM> × level <NUM>), and <NUM>σ<NUM> (standard deviation noise at <NUM> × level <NUM>) by using the following expression.

As listed in <FIG>, results were obtained where the eye-opening heights improved at a transmission speed faster than <NUM> Gbaud (the transmission speed corresponding to the frequency of <NUM>) when the phosphorus concentration was <NUM> to <NUM>%, and an effect of the present illustrative example could be verified. In more detail, in the case of <NUM> Gbaud, the eye-opening heights were the same to be <NUM> when the phosphorus content concentrations were <NUM> to <NUM>% and <NUM>%. However, as the transmission speed became faster, for example, in the case of <NUM> Gbaud, each eye-opening height was <NUM> when the phosphorus content concentration was <NUM> to <NUM>%, and the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%. In the case of <NUM> Gbaud, each eye-opening height was <NUM> to <NUM> when the phosphorus content concentration was <NUM> to <NUM>%, where the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%. Further, in the case of <NUM> Gbaud, each eye-opening height was <NUM> when the phosphorus content concentration was <NUM> to <NUM>%, where the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%.

As described hereinabove, according to the first illustrative example, it is possible to reduce the loss and increase the eye-opening height by using the transmission path having the stacked structure illustrated in <FIG> for the transmission paths <NUM>, <NUM> transmitting the digital signals and setting the phosphorus content concentration of the nickel-phosphorus layer to <NUM> to <NUM> mass%. As a result, it is possible to reduce occurrence of transmission errors.

<FIG> is a view illustrating a configuration example of a second illustrative example. The second illustrative example illustrated in <FIG> is an example where a nickel-phosphorous layer is applied to an optical/electrical converter which is used in optical communication or the like. An optical/electrical converter <NUM> illustrated in <FIG> includes a dielectric substrate <NUM>, connectors <NUM>, transmission paths <NUM>, an optical/electrical converting part <NUM>, an optical fiber <NUM>, and electronic components <NUM> to <NUM>.

Here, the dielectric substrate <NUM> is formed of, for example, an insulator such as PTFE. Sixteen pieces of connectors <NUM> are disposed at an end part of the dielectric substrate <NUM> formed in a semicircular state, and non-illustrated coaxial cables are respectively connected thereto. Each transmission path <NUM> has a structure similar to <FIG>, and connects between the connector <NUM> and the optical/electrical converting part <NUM>. The optical/electrical converting part <NUM> multiplexes signals input from the transmission paths <NUM>, then converts into optical signals to transfer to the optical fiber <NUM>, and converts optical signals input from the optical fiber <NUM> into electrical signals, then demultiplexes to supply to each of the connectors <NUM> through the transmission paths <NUM>.

In the second illustrative example illustrated in <FIG>, each of the transmission paths <NUM> has a structure similar to <FIG>, and a phosphorus concentration of the nickel-phosphorus layer is set to <NUM> to <NUM> mass%. Signals of over <NUM> (<NUM> Gbaud) are transmitted through each of the transmission paths <NUM>. Accordingly, the signal which is transmitted through the transmission path <NUM> has little loss as illustrated in <FIG>, and the eye-opening height is kept to be high as illustrated in <FIG>. According to the second illustrative example illustrated in <FIG>, it is possible to reduce occurrence of transmission errors between the connectors <NUM> and the optical /electrical converting part <NUM>.

<FIG> is a view illustrating a structural example of an antenna device according to a third illustrative example. In the third illustrative example illustrated in <FIG>, an antenna device <NUM> includes a dielectric substrate <NUM>, a radiation element <NUM>, a power feeding line <NUM>, and a ground conductor plate <NUM>.

Here, the dielectric substrate <NUM> is formed by a dielectric plate-like member, and electrically insulates the radiation element <NUM> and the power feeding line <NUM>, and the ground conductor plate <NUM>.

The radiation element <NUM> is formed by stacking a plurality of conductors as it is described later with reference to <FIG>, and is a patch antenna which radiates high-frequency signals supplied from the power feeding line <NUM> as radio waves.

The power feeding line <NUM> supplies the high-frequency signals such as millimeter waves and microwaves to the radiation element <NUM>.

In the third illustrative example, a nickel-phosphorous layer is applied to the radiation element <NUM>, the power feeding line <NUM>, and the ground conductor plate <NUM>. That is, the radiation element <NUM>, the power feeding line <NUM>, and the ground conductor plate <NUM> are each formed by depositing a plurality of conductor layers on the dielectric substrate <NUM>. In more detail, a copper layer, a nickel-phosphorus layer, and a gold layer are deposited in a stacked state. A phosphorus content ratio contained in the nickel-phosphorus layer is set to <NUM> mass% or more and less than <NUM> mass%, and gain can be thereby improved with respect to a frequency of over <NUM>.

<FIG> is a view illustrating a structural example of a test sample which was used when a loss was actually measured in a case when high-frequency signals were transmitted to the radiation element <NUM> used for the antenna device <NUM> of the present illustrative example. The test sample illustrated in <FIG> has a structure as same as the radiation element <NUM> and the ground conductor plate <NUM> in <FIG>. In an example in <FIG>, the test sample is prepared by forming copper layers <NUM>, <NUM> as conductor layers on the PTFE (poly tetra fluoro ethylene)-based dielectric substrate <NUM> with a thickness of about <NUM> by adhering a copper foil with a thickness of about <NUM> pm on each of both surfaces of the substrate, and subjecting the substrate to an etching process and a through-hole plating treatment. Next, nickel-phosphorus plating is performed by means of electroless plating on surfaces of the copper layers <NUM>, <NUM> to form nickel-phosphorus layers <NUM>, <NUM> each with a thickness of about <NUM> pm. At this time, a concentration of a plating solution is set such that a concentration of phosphorus of each of the nickel-phosphorus layers <NUM>, <NUM> becomes <NUM> mass% or more and less than <NUM> mass%. Next, gold layers <NUM>, <NUM> each with a thickness of about <NUM> are formed on surfaces of the nickel-phosphorus layers <NUM>, <NUM> by means of gold plating.

In the sample illustrated in <FIG>, results where a transmission loss was measured at each frequency when phosphorus content concentrations of the nickel-phosphorus layers <NUM>, <NUM> were changed are listed in <FIG>. In more detail, <FIG> is the results of actual measurement where the losses of the transmission path of the test sample illustrated in <FIG> per <NUM> while changing the phosphorus content concentration and the frequency.

The phosphorus concentration was measured by dissolving the nickel-phosphorus layer in a nitric acid solution, and subjecting the solution to mass spectrometry by using an inductively coupled plasma atomic emission spectroscopy (manufactured by Shimadzu Corporation, ICPS-<NUM> or the like), or mass spectrometry by EDS (energy dispersive X-ray spectrometry) analysis of a layer cross section, and the thickness of the nickel-phosphorus layer was measured by using a fluorescence X-ray film thickness meter (manufactured by Seiko Instruments Inc. , SFT3200 or the like). Measurement of electric properties was performed by using a network analyzer as described later, and the properties of the sample were judged by measuring transmission loss.

Here, the transmission loss indicates a ratio of transmittable high-frequency signals without loss, reflection, and radiation in a sample transmission path by passing the high-frequency signals through a test piece. It is judged that the smaller a value of the transmission loss is, the better the properties are. Later-described graphs and tables are represented by values in minus, and in this case, the properties are judged to be good as the values are larger.

As listed in <FIG>, it became clear as a result of the actual measurement that when the phosphorus concentrations were <NUM>, <NUM>, <NUM> mass%, each loss became smaller compared to other concentrations at the frequency higher than <NUM>. That is, when the frequency was <NUM>, the losses became smaller when the phosphorus concentrations were <NUM>, <NUM>, <NUM>% compared to the case when it was <NUM> to <NUM>% (-<NUM> dB to -<NUM> dB became -<NUM> dB). However, it became clear that when the frequency became higher, the loss did not change even when the phosphorus concentration changed when the frequency was <NUM> (the loss was constant to be -<NUM> dB independent from the phosphorus concentration), and the loss became smaller when the phosphorus content concentration was <NUM> to <NUM>% compared to the cases when the phosphorus content concentrations were <NUM>,<NUM>, <NUM>, <NUM>% when the frequency was <NUM> or more. As a relation between the transmission loss at <NUM> and the phosphorus concentration is illustrated in <FIG>, it can be seen that the transmission loss becomes rapidly smaller when the concentration is below <NUM>%.

It is possible to improve the gain of the antenna device which radiates electromagnetic waves from the radiation element <NUM> by applying the structure similar to <FIG> to the radiation element <NUM>, the power feeding line <NUM>, and the ground conductor plate <NUM> illustrated in <FIG> and setting the phosphorus concentration of the nickel-phosphorus layer to <NUM> to <NUM>%.

<FIG> lists antenna gains at <NUM> when the phosphorus content concentration of the antenna device <NUM> having the structure similar to <FIG> was changed. Note that the antenna gain is an index value representing energy intensity at a radiation angle where radiation becomes the maximum, and efficiency is higher as the value is larger. As listed in <FIG>, when the phosphorus content concentration was <NUM> to <NUM> mass%, the gains improved for <NUM> dBi compared to a case when it was <NUM> mass%.

<FIG> illustrates antenna gain characteristics in all directions of the antenna device <NUM> when the phosphorus content concentration is changed. In <FIG>, a solid line represents characteristics when the phosphorus content concentration is <NUM> to <NUM> mass%, and a dot-and-dash line represents characteristics when the phosphorus content concentration is <NUM> mass%. As illustrated in <FIG>, when the phosphorus content concentration is <NUM> to <NUM> mass%, the gain improves in all directions compared to the case when it is <NUM> mass%.

As described above, in the third illustrative example, it is possible to improve the antenna gain for about <NUM> dBi by using the stacked structure illustrated in <FIG> as each of the radiation element <NUM> and the ground conductor plate <NUM> of the antenna device <NUM>, and setting the phosphorus content concentration of the nickel-phosphorus layer to <NUM> to <NUM> mass%. As a result, the antenna gain can be improved for about <NUM> dBi by using the present illustrative example for both a transmitting antenna and a receiving antenna.

<FIG> is a view illustrating a structural example of an antenna device according to a fourth illustrative example. The fourth illustrative example illustrated in <FIG> is formed as a plate-like inverse F antenna device <NUM>. The plate-like inverse F antenna device <NUM> includes a radiation element <NUM>, a short-circuit part <NUM>, and a power feeding part <NUM>.

Here, the plate-like inverse F antenna device <NUM> is formed by bending an end part of a conductor having the stacked structure illustrated in <FIG>. That is, the radiation element <NUM> and the short-circuit part <NUM> can be formed by bending an end part of the plate-like member including the copper layer <NUM>, the nickel-phosphorus layer <NUM>, and the gold layer <NUM> illustrated in <FIG> almost at a right angle. The power feeding part <NUM> can be formed by connecting a columnar conductor to a part of the radiation element <NUM>.

<FIG> illustrates a disposition example of the plate-like inverse F antenna device <NUM> illustrated in <FIG> on a ground conductor plate <NUM>. In this example, four plate-like inverse F antenna devices <NUM>-<NUM> to <NUM>-<NUM> are disposed on four installation positions A to C. The ground conductor plate <NUM> is formed by stacking the copper layer, the nickel-phosphorus layer, and the gold layer as illustrated in <FIG>.

The plate-like inverse F antenna device <NUM> is one where a part of a linear inverse F antenna device in parallel to a ground plate is made into a plate-like shape. Here, the linear inverse F antenna device is an antenna where a monopole antenna being a basis of an antenna is bent at a right angle in midway, and impedance characteristics are improved by adding a short-circuit line in a vicinity of a power feeding line, and it is named after its F-shape. The plate-like inverse F antenna device <NUM> where the linear inverse F antenna device as stated above is improved is an antenna where a part of the linear inverse F antenna which is in parallel to the ground conductor plate is made into the plate-like shape, and various modifications become possible and flexibility of the antenna increases such that power feeding lines can be located at various positions, a slot (cut) can be formed at the radiation element owing to its plate-like shape. Note that a bandwidth of the plate-like inverse F antenna device <NUM> can be increased to <NUM> times or more as much as a plate-like inverse antenna device having a basic shape by adding a chip resistance element to the short-circuit part <NUM> to make an antenna length to λ/<NUM> and reducing an antenna height to <NUM>λ.

According to the plate-like inverse F antenna device <NUM> illustrated in <FIG> and <FIG>, the antenna gain can be improved as same as the first illustrative example by using the stacked structure illustrated in <FIG> for at least one of the radiation element <NUM>, the short-circuit part <NUM>, the power feeding part <NUM>, and the ground conductor plate <NUM>, and setting the phosphorus content concentration of the nickel-phosphorus layer to <NUM> to <NUM> mass%. The gain can be further improved by applying the present illustrative example to both of a transmitting antenna and a receiving antenna.

<FIG> is a view illustrating a structural example of an antenna device according to a fifth illustrative example. The fifth illustrative example illustrated in <FIG> is formed as an inverse F antenna device <NUM>. In the inverse F antenna device <NUM>, a stacked conductor layer <NUM> having the stacked structure similar to <FIG> is formed on a dielectric substrate <NUM>, and an IC (integrated circuit) <NUM> is mounted thereon.

Here, the stacked conductor layer <NUM> includes a radiation element <NUM> having a rectangular form, a power feeding part <NUM> feeding high-frequency power from the IC <NUM> to the radiation element <NUM>, a short-circuit part <NUM> short-circuiting the radiation element <NUM> to a ground conductor <NUM>, and the ground conductor <NUM> which is kept at a ground potential.

The IC <NUM> is mounted on the ground conductor <NUM>, and feeds the high-frequency power to the radiation element <NUM> through the power feeding part <NUM>.

In the structural example illustrated in <FIG>, all of the radiation element <NUM>, the power feeding part <NUM>, the short-circuit part <NUM>, and the ground conductor <NUM> are each set to have the stacked structure illustrated in <FIG>, but at least one of the above may have the stacked structure illustrated in <FIG>.

According to the F antenna device <NUM> illustrated in <FIG>, the antenna gain can be improved as same as the first illustrative example by using the stacked structure illustrated in <FIG> for at least one of the radiation element <NUM>, the power feeding part <NUM>, the short-circuit part <NUM>, and the ground conductor <NUM>, and setting the phosphorus content concentration of the nickel-phosphorus layer to <NUM> to <NUM> mass%. The gain can be further improved by applying the inverse F antenna device <NUM> illustrated in <FIG> to both of a transmitting antenna and a receiving antenna.

It goes without saying that the above-mentioned illustrative examples that do not describe or limit the present invention. In each of the illustrative examples, the phosphorus content concentration of the nickel-phosphorus layer was set in a range of <NUM> to <NUM> mass%, but it may be set to be the range or less.

<FIG> illustrates results where transmission losses (dB) of a transmission path at <NUM> per <NUM> were measured while changing the phosphorus content concentration of the nickel-phosphorus layer. As illustrated by black circles in <FIG>, the transmission loss decreases as the phosphorus concentration decreases from <NUM>% to <NUM>%. In more detail, in an example in <FIG>, the transmission loss does not largely change even if the phosphorus concentration decreases from <NUM>% to about <NUM>% as illustrated by a dotted line. However, the decrease in the transmission loss becomes obvious when the phosphorus concentration becomes less than <NUM>%, and becomes the minimum when the phosphorus concentration is <NUM>%. Meanwhile, the transmission loss becomes <NUM> dB or more when the phosphorus concentration becomes <NUM>% as illustrated by a hatched circle at a left end in <FIG>.

<FIG> lists results where the transmission losses were measured until the phosphorus concentration became <NUM>% through the method as same as <FIG>. As listed in <FIG>, it became clear as a result of the actual measurement that when the phosphorus concentrations were <NUM>, <NUM>, <NUM> mass%, each loss became smaller compared to a case of <NUM> mass% at the frequency higher than <NUM>. That is, when the frequency was <NUM>, the loss became smaller when the phosphorus concentration was <NUM>% compared to the cases of <NUM> to <NUM>%. However, when the frequency became higher, the loss became constant even when the phosphorus concentration changed at <NUM> except when the phosphorus concentration was <NUM> mass%, and the losses became smaller when the phosphorus content concentrations were <NUM> to <NUM>% compared to the case of <NUM>% at <NUM> or more. When the phosphorus concentration was <NUM> mass%, the loss became larger compared to the case of <NUM> mass% or more.

<FIG> is a view corresponding to <FIG>. As listed in <FIG>, results were obtained where eye-opening heights improved at a transmission speed faster than <NUM> Gbaud (the transmission speed corresponding to the frequency of <NUM>) when the phosphorus concentration was <NUM> to <NUM>%. In more detail, in the case of <NUM> Gbaud, each eye-opening height was <NUM>. However, as the transmission speed became faster, for example, in the case of <NUM> Gbaud, the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%, each eye-opening height was <NUM> when the phosphorus content concentrations were <NUM>, <NUM>%, and the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%. In the case of <NUM> Gbaud, the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%, each eye-opening height was <NUM> when the phosphorus content concentrations were <NUM>, <NUM>%, and the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%. Further, in the case of <NUM> Gbaud, each eye-opening height was <NUM> when the phosphorus content concentrations were <NUM>, <NUM>%, the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%, and the eye-opening height was <NUM> when the phosphorus content concentration was <NUM>%. When the phosphorus concentration was <NUM> mass%, the eye-opening height became lower compared to the case when the phosphorus concentration was <NUM> mass% or more.

<FIG> is a view corresponding to <FIG>, and lists antenna gains at <NUM> when the phosphorus content concentration of the antenna device <NUM> having the structure similar to <FIG> was changed. As listed in <FIG>, the gain improved for <NUM> dBi when the phosphorus content concentration was <NUM> mass% compared to the case of <NUM> mass%, the gain improved for <NUM> dBi when the phosphorus content concentration was <NUM> mass% compared to the case of <NUM> mass%, and the gain improved for <NUM> dBi when the phosphorus content concentration was <NUM> mass% compared to the case of <NUM> mass%. When the phosphorus concentration was <NUM> mass%, the antenna gain was lowered compared to the case of <NUM> mass%.

An optimum value is considered to be in a range of over <NUM> mass% and <NUM> mass% or less from comparisons of <FIG>. Regarding a lower limit value of the optimum value, it turns out that characteristics are improved compared to the case of <NUM> mass% when the lower limit value is <NUM> mass% or more, or <NUM> mass% or more from a simple experimentation up to now, further, when the lower limit value is <NUM> mass% or more, it is preferable because the phosphorus concentration at a plating time can be more easily controlled. When the lower limit value is <NUM> mass% or more, it is further preferable because the phosphorus concentration at the plating time can be more easily controlled, but it may be below <NUM> mass%. Further, it is known that an upper limit value of the optimum value is preferably <NUM> mass% or less, more preferably <NUM> mass% or less, and further preferably <NUM> mass% or less. In addition, solder wettability (for example, reliability of bonding with a solder) of the nickel-phosphorus layer can be improved by setting the value in a range satisfying the above, and more suitable characteristics as the transmission path can be obtained.

<FIG> is a view illustrating processes of plating treatment. As listed in <FIG>, in the processes of the plating treatment, (<NUM>) in an immersion degreasing process, immersing in a degreasing liquid (for example, a liquid with a product name: ICP Clean SC at a concentration of <NUM>/L at a temperature of <NUM>) for four minutes, (<NUM>) in an acid degreasing liquid process, immersing in an acid degreasing liquid (for example, a liquid with a product name: ICP Clean S-<NUM> at a concentration of <NUM>/L at a temperature of <NUM>) for four minutes, (<NUM>) in a soft-etching process, immersing in a soft-etching liquid (for example, a liquid of persulfuric acid soda at a concentration of <NUM>/L at a temperature of <NUM>) for <NUM> seconds, (<NUM>) in a desmutting process, immersing in a liquid, for example, setting <NUM>% sulfuric acid at a concentration of <NUM>/L at a temperature of <NUM> for <NUM> seconds, (<NUM>) in a pre-dipping process, immersing in a liquid setting <NUM>% hydrochloric acid at a concentration of <NUM>/L at a temperature of <NUM> for <NUM> seconds, and (<NUM>) in a catalyst addition process, immersing in a catalyst liquid (for example, a liquid with a product name: ICP accera at a concentration of <NUM>/L at a temperature of <NUM>) for <NUM> seconds.

Next, (<NUM>) in an electroless nickel-phosphorus (Ni-P) plating process, a nickel-phosphorus layer is formed. In this process, the nickel-phosphorus layers each with a film thickness of about <NUM> pm are formed in each of six stages of plating processes in total where pH of a plating solution is changed in a range of <NUM> to <NUM>, a temperature is changed in a range of <NUM> to <NUM>, an Ni concentration of the plating solution is changed in a range of <NUM> to <NUM>/L, and time is changed in a range of <NUM> to <NUM> minutes. It goes without saying that the values are just examples, and values other than the above are acceptable.

(<NUM>) in an electroless Au plating process, a gold layer with a film thickness of about <NUM> pm is formed by immersing in a plating solution with, for example, pH of <NUM>, at the temperature of <NUM>, a concentration of gold (Au) of <NUM>/L for <NUM> minutes.

Finally, (<NUM>) in a drying process, a substrate is completed to be finished.

According to the above-stated processes, a transmission path or a radiation element having the structures illustrated in <FIG> and <FIG> can be formed.

In the above illustrative examples, the microstrip transmission path is made by forming the transmission path <NUM> at the upper side surface of the dielectric substrate <NUM>, and the ground layer <NUM> is formed at the lower side surface as illustrated in <FIG>, but a coplanar transmission path may be formed. Even in such a case, the loss can be reduced with respect to the high-frequency signals of over <NUM>.

Other elements may be contained in the nickel-phosphorus layer in a range not impairing an effect obtained by the present invention. For example, the effect of the present invention can be exerted even if elements such as Fe, Zn, Cr are contained in the nickel-phosphorus layer at a minute amount (for example within <NUM>%).

In each of the above illustrative examples, the transmission path <NUM> has a three-layer structure of the copper layer <NUM>, the nickel-phosphorus layer <NUM>, and the gold layer <NUM>, but may have a structure where, for example, only the nickel-phosphorus layer <NUM> is held at the surface of the dielectric substrate <NUM>. The nickel-phosphorus layer <NUM> may be combined with at least one of the copper layer <NUM> or the gold layer <NUM>. Even in such a structure, it is possible to reduce the loss with respect to the high-frequency signals of over <NUM>.

In each of the above illustrative examples, the nickel-phosphorus layer <NUM> is formed by the electroless plating, but it may be formed by, for example, electroplating, vacuum deposition, and the like other than the electroless plating.

The nickel-phosphorus layer <NUM> may have an amorphous form or a crystalline form.

A layer formed of other metals such as, for example, aluminum may be formed instead of the copper layers <NUM>, <NUM>. Other metals such as, for example, platinum may be used instead of the gold layers <NUM>, <NUM>, or the gold layers <NUM>, <NUM> may not exist.

In each of the above illustrative examples, it is explained while exemplifying the case when the signals transmitted through the transmission path are digital signals, but the similar effect can be expected even when analog signals are transferred. The loss can be reduced regarding the high-frequency signal component of over <NUM> as long as the high-frequency signal component of over <NUM> is contained even if other frequency components are contained.

In each of the above illustrative examples, it is explained while exemplifying the transmission path transmitting electrical signals, but the present invention relates to a waveguide transmitting electromagnetic waves as illustrated in <FIG>. In the embodiment of the invention shown in <FIG>, a waveguide <NUM> is formed by a hollow member <NUM> which is formed to have a rectangular (or circular) shape with a plate-like member having conductivity (for example, copper or aluminum), as illustrated in <FIG>. A nickel-phosphorus layer <NUM> is formed on an internal surface of the hollow member <NUM> as a cross-section thereof is enlarged and illustrated in <FIG>. The nickel-phosphorus layer <NUM> is formed by electroless plating or the like as same as the above-stated cases, and the phosphorus concentration is set to be over <NUM> mass% and less than <NUM> mass%. According to such an embodiment, a loss of the electromagnetic waves transmitted through the waveguide <NUM> can be reduced.

In the third and fourth illustrative examples, it is explained while exemplifying the transmitting antenna device, but the present invention may be applied to a receiving antenna device. According to such a structure, reception gain can be improved.

In the third and fourth illustrative examples, the radiation element <NUM>, the ground conductor plates <NUM>, <NUM>, the power feeding parts <NUM>, <NUM>, and the short-circuit parts <NUM>, <NUM> each have a three-layer structure of the copper layer <NUM>, the nickel-phosphorus layer <NUM>, and the gold layer <NUM>, but for example, a structure where only the nickel-phosphorus layer <NUM> is held on a surface of the dielectric substrate <NUM> may be used. The nickel-phosphorus layer <NUM> may be combined with at least one of the copper layer <NUM> or the gold layer <NUM>. According to such a structure enables to improve the gain when the high-frequency signals of over <NUM> are transmitted/received.

In the third and fourth illustrative examples, it is explained while exemplifying the patch antenna, the plate-like inverse F antenna, and the inverse F antenna, but the nickel-phosphorous layer may be applied to, for example, a normal mode helical antenna where a λ/<NUM> monopole antenna is made into a spiral state to shorten a total length, an inverse L antenna which is made low-profile by bending the λ/<NUM> monopole antenna, and the like. It goes without saying that the nickel-phosphorous layer may be applied to antenna devices other than the above.

In each of the above illustrative examples, all of the radiation element <NUM>, the power feeding line <NUM>, and the ground conductor plate <NUM> each have the stacked structure illustrated in <FIG>, but at least one of the above may have the stacked structure illustrated in <FIG>. In <FIG> and <FIG>, at least a part of the radiation element <NUM>, the short-circuit part <NUM>, and the power feeding part <NUM> may have the stacked structure illustrated in <FIG>, and in <FIG>, at least a part of the radiation element <NUM>, the power feeding part <NUM>, the short-circuit part <NUM>, and the ground conductor <NUM> may have the stacked structure illustrated in <FIG>.

Claim 1:
A transmission path (<NUM>), configured to transmit high-frequency signals each containing a frequency component of <NUM> or more, comprising: a nickel-phosphorus layer (<NUM>) containing nickel and phosphorus, wherein the nickel-phosphorous layer (<NUM>) is formed on an inner surface of a waveguide (<NUM>) formed by a hollow member, characterized in that a phosphorus concentration of the nickel-phosphorus layer (<NUM>) is <NUM> mass% or more and <NUM> mass% or less.