Coupling waveguide and waveguide coupling method

Abstract

[Problem] To provide a coupling waveguide that can be easily manufactured and with which deterioration of transmission characteristics can be avoided. [Solution] A coupling waveguide 1 according to an embodiment that comprises: a waveguide 10 configured to propagate radio waves and provided with an opening window W1 for emitting the radio waves to the outside; a waveguide 20 provided with an opening window W2 for absorbing radio waves from the outside, configured to propagate the radio waves absorbed from a second opening window, and coupled to the waveguide 10 such that the opening window W2 at least partially overlaps the opening window W1; and an anisotropic conductive film 30 that covers the opening window W1 and the opening window W2, and bonds together the waveguide 10 and the waveguide 20.

Description

Connection waveguide and waveguide connection method

[0001] The present invention relates to a coupling waveguide and a method for coupling waveguides, and more particularly to a coupling waveguide in which waveguides are coupled to each other, and a method for coupling waveguides to each other.

[0002] Conventionally, techniques for connecting waveguides to each other have been known. For example, Patent Document 1 describes a technique for connecting two waveguides via an opening window in a conductor layer using a rectangular frame-shaped conductive joint.

[0003] The above method requires high-precision alignment between the waveguide window and the frame-shaped conductive joint. Widening the window window is one way to increase the alignment margin. However, this can lead to impedance mismatching, which can degrade transmission characteristics.

[0004] Patent No. 6349437

[0005] The problem to be solved by the present invention is to provide a coupling waveguide that can be easily manufactured and that can avoid deterioration of transmission characteristics.

[0006] A connecting waveguide according to the present invention comprises: a first waveguide configured to propagate radio waves and having a first opening window for radiating the radio waves to the outside; a second waveguide configured to absorb radio waves from the outside and through which the radio waves absorbed from the second opening window propagate, the second waveguide being connected to the first waveguide such that the second opening window at least partially overlaps the first opening window; and an anisotropic conductive film covering the first opening window and the second opening window and bonding the first waveguide and the second waveguide together.

[0007] Furthermore, in the connecting waveguide, when the connecting portion between the first waveguide and the second waveguide is viewed in the thickness direction, the conductive particles of the anisotropic conductive film may be contained in an overlapping portion between the first opening window and the second opening window.

[0008] Furthermore, in the connecting waveguide, the first waveguide may include: a first dielectric layer having a first main surface and a second main surface; a first conductive layer provided on the first main surface; a second conductive layer provided on the second main surface and having the first opening window; a first post row in which a plurality of conductive posts that penetrate the first dielectric layer and electrically connect the first conductive layer and the second conductive layer are arranged along the direction of propagation of the radio waves; and a second post row in which a plurality of conductive posts that penetrate the first dielectric layer and electrically connect the first conductive layer and the second conductive layer are arranged parallel to the first post row.

[0009] Furthermore, in the connecting waveguide, the second waveguide may include: a second dielectric layer having a third main surface and a fourth main surface; a third conductive layer provided on the third main surface and having the second opening window; a fourth conductive layer provided on the fourth main surface; a third post row in which a plurality of conductive posts that penetrate the second dielectric layer and electrically connect the third conductive layer and the fourth conductive layer are arranged along the direction of propagation of the radio waves; and a fourth post row in which a plurality of conductive posts that penetrate the second dielectric layer and electrically connect the third conductive layer and the fourth conductive layer are arranged parallel to the third post row.

[0010] Furthermore, in the connecting waveguide, the first opening window and the second opening window may have a slit shape extending in a direction perpendicular to the propagation direction of the radio waves, and the opening widths of the first opening window and the second opening window may be the same.

[0011] Furthermore, in the connecting waveguide, the first opening window and the second opening window may have a slit shape extending in a direction perpendicular to the propagation direction of the radio waves, and the opening widths of the first opening window and the second opening window may be different.

[0012] In the connecting waveguide, the second waveguide may be a waveguide having the second opening window.

[0013] The connecting waveguide may further include a horn antenna connected to an end of the waveguide.

[0014] Furthermore, in the connecting waveguide, the first opening window and the second opening window may be slit-shaped extending in a direction perpendicular to the direction of propagation of the radio waves, and the size of the conductive particles contained in the anisotropic conductive film may be smaller than the width of the slit-shaped first and second opening windows.

[0015] A waveguide connection method of the present invention includes the steps of: preparing a first waveguide configured to allow radio waves to propagate and having a first opening window for radiating the radio waves to the outside; preparing a second waveguide configured to allow radio waves to be absorbed from the outside and through which the radio waves absorbed from the second opening window propagate; and covering the first opening window and the second opening window with an anisotropic conductive film and connecting the first waveguide and the second waveguide so that the first opening window and the second opening window at least partially overlap.

[0016] In the waveguide connection method, the density of conductive particles contained in the anisotropic conductive film may be increased to reduce reflection at the connection portion between the first waveguide and the second waveguide.

[0017] According to the present invention, it is possible to provide a coupling waveguide that can be easily manufactured and that can avoid deterioration of transmission characteristics.

[0018] 5 is a perspective view of a coupling waveguide according to an embodiment. FIG. 6 is an exploded perspective view of a coupling waveguide according to an embodiment. FIG. 7 is a perspective view of a waveguide according to an embodiment. FIG. 8 is a plan view of a waveguide according to an embodiment. FIG. 9 is a cross-sectional view taken along line A-A in FIG. 4. FIG. 10 is an exploded perspective view of a coupling waveguide according to a modified example of an embodiment. FIG. 11 is an X-ray photograph of a coupling portion of sample A. FIG. 12 is a graph showing the results of measuring the transmission characteristics of sample A. FIG. 13 is an X-ray photograph of a coupling portion of sample B. FIG. 14 is a graph showing the results of measuring the transmission characteristics of sample B. FIG. 15 is a graph showing the results of a simulation using a three-dimensional analysis model of sample A and sample B. FIG. 16 is a graph showing the results of a simulation of the relationship between the width of an opening window and insertion loss, with the position of the opening window as a parameter. FIG. 17 is a graph showing the results of a simulation of the relationship between the width of an opening window and insertion loss, with the position of the opening window as a parameter.

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, components having equivalent functions are designated by the same reference numerals. The drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, and the like may differ from the actual ones. Furthermore, terms used in this specification that specify shapes, geometric conditions, physical characteristics, and their degrees, such as "parallel," "orthogonal," "equal," and "same," as well as dimensions and values ​​of physical characteristics, are not limited to their strict meanings but are interpreted to include a range within which similar functions can be expected.

[0020] <Coupling Waveguide> A coupling waveguide 1 according to an embodiment will be described with reference to FIGS.

[0021] As shown in FIGS. 1 and 2 , the coupling waveguide 1 includes a waveguide 10 (first waveguide), a waveguide 20 (second waveguide) coupled to the waveguide 10, and an anisotropic conductive film 30 that bonds the waveguide 10 and the waveguide 20 together.

[0022] The waveguide 10 is configured to allow radio waves to propagate through it. As will be described later, in this embodiment, the waveguide 10 is a substrate integrated waveguide (SIW), and signals propagate through it as radio waves. The waveguide 10 is provided with an opening window W1 (first opening window) for radiating radio waves to the outside.

[0023] The waveguide 20 is provided with an opening window W2 (second opening window) for absorbing radio waves from the outside, and is configured so that the absorbed radio waves propagate through the opening window W2. The waveguide 20 is connected to the waveguide 10 so that the opening window W2 at least partially overlaps with the opening window W1 when the connection portion is viewed in the thickness direction.

[0024] The aperture window W1 and the aperture window W2 are slit-shaped and extend in a direction perpendicular to the propagation direction of the radio waves. The length of the aperture window W1 and the aperture window W2 is equal to the width of the waveguide 10 (width a in FIG. 5 ). In this embodiment, the aperture width of the aperture window W1 and the aperture window W2 is the same. However, the aperture widths of the aperture window W1 and the aperture window W2 may be different. For example, the aperture window W1 may be formed larger than the aperture window W2 so that the aperture window W2 fits within the aperture window W1.

[0025] In this embodiment, the waveguides 10 and 20 are substrate integrated waveguides, which are also called substrate buried waveguides or post-wall waveguides.

[0026] The anisotropic conductive film 30 is an anisotropic conductive film (ACF) containing a plurality of conductive particles CP. The anisotropic conductive film 30 is provided so as to cover the opening window W1 and the opening window W2, and bonds the waveguide 10 and the waveguide 20 together. The waveguide 10 and the waveguide 20 (more specifically, the conductive layers of the respective waveguides) are electrically connected via the anisotropic conductive film 30. The anisotropic conductive film 30 also functions as an adhesive, bonding the waveguide 10 and the waveguide 20 together.

[0027] 1, when the connecting portion between the waveguide 10 and the waveguide 20 is viewed in the thickness direction, the conductive particles CP of the anisotropic conductive film 30 are contained in the overlapping portion between the opening window W1 and the opening window W2. The size of the conductive particles CP contained in the anisotropic conductive film 30 is smaller than the width of the slit-shaped opening windows W1 and W2.

[0028] As shown in FIG. 1 , in the coupling waveguide 1 of this embodiment, a microstrip line MSL1 is connected to a waveguide 10, and a microstrip line MSL2 is connected to a waveguide 20. The microstrip lines MSL1 and MSL2 have signal lines on the upper surface of a dielectric layer that taper in width at the end, and a ground layer (not shown) is provided on the lower surface of the dielectric layer. The microstrip line MSL1 and the waveguide 10 may be integrally configured with a common dielectric layer. Similarly, the microstrip line MSL2 and the waveguide 20 may be integrally configured with a common dielectric layer.

[0029] Furthermore, the planar shape of the waveguides 10 and 20 is not limited to the linear shape shown in FIG. 1, but may have a shape having curved portions.

[0030] The detailed configuration of the waveguide 10 will be described with reference to FIGS.

[0031] The waveguide 10 includes a dielectric layer 11 (first dielectric layer) having an upper surface (first principal surface) and a lower surface (second principal surface), a conductive layer 12 (first conductive layer) provided on the upper surface of the dielectric layer 11, a conductive layer 13 (second conductive layer) provided on the lower surface of the dielectric layer 11 and having an opening window W1, a plurality of conductive posts 14 constituting a first post row, and a plurality of conductive posts 15 constituting a second post row. A portion of the conductive layer 13 is removed to form the opening window W1.

[0032] In this embodiment, the dielectric layer 11 is made of a flexible material such as liquid crystal polymer (LCP). The dielectric layer 11 is not limited to a single layer, and may be made of multiple layers. The material of the dielectric layer 11 is not particularly limited, and may be polyimide (PI), modified polyimide (MPI), polyethylene naphthalate (PEN), polyether ether ketone (PEEK), fluororesin (PFA, PTFE, etc.), etc. The dielectric layer 11 may also be made of a non-flexible material such as ceramic. The conductive layers 12 and 13 are conductive layers made of copper foil, etc. A portion of the conductive layer 13 is removed to form an opening window W1.

[0033] 3 and 4, the plurality of conductive posts 14 are arranged along the direction of propagation of radio waves propagating within the waveguide 10 (the longitudinal direction of the waveguide 10). Similarly, the plurality of conductive posts 15 are arranged along the direction of propagation of radio waves propagating within the waveguide 10. The radio waves propagating within the waveguide 10 form electromagnetic field patterns such as TE10 and travel while being reflected by the first post row and the second post row.

[0034] In addition to the conductive posts 14 and 15, a plurality of conductive posts 16 are provided to surround the opening window W1. This allows the radio waves propagated within the waveguide 10 to be efficiently radiated to the outside from the opening window W1. Furthermore, in this embodiment, a plurality of conductive posts 17 are provided behind the conductive posts 16 (toward the end of the waveguide 10). This makes it possible to prevent the radio waves propagated within the waveguide 10 from being radiated from the end of the waveguide 10.

[0035] As shown in Figure 5, a plurality of conductive posts 14 penetrate the dielectric layer 11 and electrically connect the conductive layer 12 and the conductive layer 13. Similarly, a plurality of conductive posts 15 penetrate the dielectric layer 11 and electrically connect the conductive layer 12 and the conductive layer 13. The conductive posts 16 and 17 are configured in a similar manner. Note that the conductive posts 14, 15, 16, and 17 are not limited to the configuration shown in Figure 5 as long as they are configured as interlayer connection paths that electrically connect the conductive layer 12 and the conductive layer 13. For example, the conductive posts 14 to 17 may be vias including lands (intermediate lands) in the dielectric layer 11, or may be vias in which a plurality of vias are stacked in the thickness direction of the dielectric layer 11, or vias stacked in staggered positions with the stacking positions offset, or may be plated through holes.

[0036] The first and second post rows are arranged parallel to each other. A waveguide through which radio waves propagate is formed within waveguide 10 by conductive layer 12, conductive layer 13, the first and second post rows. As shown in Figure 5, when the distance between conductive post 14 and conductive post 15 (the horizontal width of the waveguide) is a and the thickness of dielectric layer 11 (the vertical width of the waveguide) is b, the cutoff frequency fc of waveguide 10 is given by the following equation:

[0037] Here, c ０ is the dielectric constant of a vacuum, and ε ｒ is the relative permittivity of the dielectric material of the dielectric layer 11. Note that the waveguide forms multiple electromagnetic field patterns depending on the frequency, but in order to transmit a signal in the TE10 mode, which has the highest transmission efficiency, the vertical width b of the waveguide needs to be smaller than the horizontal width a of the waveguide.

[0038] In this embodiment, both the waveguide 10 and the waveguide 20 are substrate integrated waveguides, and the waveguide 20 has the same structure as the waveguide 10 .

[0039] The configuration of the waveguides 10 and 20 is not limited to SIW, and at least one of them may be a waveguide made of a rectangular metal tube. For example, as shown in Fig. 6, instead of the waveguide 20, a waveguide 20A configured as a waveguide having an opening window W2 may be connected to the waveguide 10. A horn antenna 40 may be connected to the end of the waveguide 20A. The horn antenna 40 may also be connected to the end of an SIW waveguide.

[0040] [Example] Next, the results obtained by measuring the transmission characteristics of the coupling waveguide 1 according to the above embodiment will be described. Here, two samples (sample A and sample B) with different densities of conductive particles CP contained in the anisotropic conductive film 30 were prepared and measured. Note that there is no difference between sample A and sample B other than the density of the conductive particles CP.

[0041] In samples A and B, the width a of the waveguide cross section was 2.8 mm, and the length b was 0.225 mm. A liquid crystal polymer with a relative dielectric constant of 2.9 was used as the dielectric layer. The widths of the opening windows W1 and W2 were 100 μm. In fabricating the samples, the waveguide 10 and the waveguide 20 were connected so that the opening windows W1 and W2 were approximately aligned.

[0042] Different anisotropic conductive films were used for Sample A and Sample B. The thickness of the anisotropic conductive film was 40 μm. The density of conductive particles in Sample A was approximately 70 particles / mm ２ The density of the conductive particles in sample B was approximately 350 particles / mm ２ As described above, Sample B has a higher density of conductive particles than Sample A. The diameter of the conductive particles is approximately 30 to 40 μm. In preparing Samples A and B, an ACF for IC cards, which can be bonded at low temperature and low pressure, was used.

[0043] Figure 7 is an X-ray photograph of the connection portion of the fabricated sample A, observed from above. This X-ray photograph confirms the conductive posts 14, 15, 16, and 17, the open windows W1 and W2, and the conductive particles CP. The conductive particles CP are present in the open windows W1 and W2. Note that in Figure 7, only the components of the waveguide on the left side are labeled.

[0044] The transmission characteristics of the above samples A and B were measured using an RF probe and a vector network analyzer. The measured transmission characteristics included those of the waveguides 10 and 20 as well as those of the microstrip lines MSL1 and MSL2.

[0045] Figure 8 is a graph showing the results of measuring the transmission characteristics of sample A. Looking at the characteristics of parameter S21, we see that the insertion loss decreases (the transmitted signal increases) at frequencies higher than the cutoff frequency (approximately 32 GHz). Furthermore, looking at parameter S11, we see that the reflected component decreases at frequencies higher than the cutoff frequency. Thus, it was confirmed that sample A has the desired characteristics as a waveguide.

[0046] Figure 9 is an X-ray photograph of the connection portion of the fabricated sample B, observed from above. This X-ray photograph confirms the presence of conductive posts 14, 15, 16, and 17, the opening windows W1 and W2, and conductive particles CP. It can also be seen that more conductive particles CP are present in the opening windows W1 and W2 than in sample A. Note that in Figure 9, only the components of the waveguide on the left side are labeled.

[0047] 10 is a graph showing the results of measuring the transmission characteristics of Sample B. As with Sample A, the transmitted signal increases and the reflected component decreases at frequencies higher than the cutoff frequency, confirming that Sample B has the desired characteristics as a waveguide.

[0048] Furthermore, comparing the measurement results of Sample A and Sample B, the waveform ripples (S11 and S21) are reduced in Sample B at frequencies higher than the cutoff frequency. This means that Sample B has less signal reflection at the connecting portion than Sample A. The reason for this is thought to be that Sample B has a larger number of conductive particles CP present in the open windows W1 and W2, which narrows the effective width of the open windows and improves the transmission characteristics.

[0049] To verify the above considerations, three-dimensional analytical models of Sample A and Sample B were created and electromagnetic field analysis simulations were performed. Figures 11(a) and 11(b) are graphs showing the simulation results. Figure 11(a) shows the frequency characteristics of parameter S21, and Figure 11(b) shows the frequency characteristics of parameter S11. These results show that Sample B, which uses an anisotropic conductive film with a high density of conductive particles, has lower insertion loss and reflection loss than Sample A.

[0050] Furthermore, to investigate the effect of the window opening width on the transmission characteristics, several models of the connecting waveguide (excluding the anisotropic conductive film) were created using the window opening width as a parameter, and the simulation results are shown in Figures 12 and 13. The only difference between Figures 12 and 13 is the vertical width of the waveguide cross section (thickness of the dielectric layer). Figure 12 shows the case where the dielectric layer thickness is 0.2 mm, and Figure 13 shows the case where the dielectric layer thickness is 0.4 mm.

[0051] 12 and 13, the horizontal axis represents the width of the aperture, and the vertical axis represents the insertion loss at 50 GHz. P0.3, P0.4, and P0.5 in the graphs represent the positions of the aperture in the waveguide (the positions from the end of the waveguide). For example, P0.1 indicates that the aperture is located 0.3 mm away from the end of the waveguide.

[0052] As can be seen from Figures 12 and 13, the wider the opening window width (slot width), the greater the insertion loss. Therefore, a narrower opening window width is advantageous for improving transmission characteristics. This result also suggests that the transmission characteristics were improved in Sample B, which uses an anisotropic conductive film containing a high concentration of conductive particles, because the effective opening window width was smaller than in Sample A, which uses an anisotropic conductive film containing a low concentration of conductive particles.

[0053] <Waveguide Coupling Method> A waveguide coupling method for manufacturing the above-described coupling waveguide 1 will be described.

[0054] A waveguide 10 is prepared that is configured to allow radio waves to propagate and has an opening window W1 for radiating the radio waves to the outside. Also, a waveguide 20 is prepared that is configured to allow radio waves to propagate and has an opening window W2 for absorbing radio waves from the outside. Note that the waveguides 10 and 20 may have the same structure or different structures.

[0055] After preparing the waveguides 10 and 20, the opening window W1 and the second opening window are covered with the anisotropic conductive film 30, and the waveguide 10 and the waveguide 20 are connected so that the opening window W1 and the opening window W2 at least partially overlap when viewed in the thickness direction of the connected portion. In this process, for example, the waveguide 10 and the waveguide 20 are stacked with the anisotropic conductive film 30 sandwiched therebetween so that the opening window W1 and the opening window W2 overlap, and then the stack is subjected to a heat and pressure treatment. The anisotropic conductive film 30 may be an ACF for IC cards, which can be bonded at relatively low temperatures and low pressures.

[0056] Based on the measurement results and simulation results of the above sample, the reflection of radio waves at the connection portion between the waveguide 10 and the waveguide 20 may be reduced by increasing the density of the conductive particles contained in the anisotropic conductive film.

[0057] <Effects> As described above, in this embodiment, the waveguide 10 and the waveguide 20 are connected via the anisotropic conductive film 30 so that the opening window W1 and the opening window W2 at least partially overlap each other. This makes it easy to align the waveguide 10 and the waveguide 20, and also ensures desired transmission characteristics.

[0058] Therefore, according to this embodiment, it is possible to provide a coupling waveguide that can be easily manufactured and that can prevent deterioration of transmission characteristics.

[0059] Furthermore, by using an anisotropic conductive film containing a high concentration of conductive particles, the effective width of the window is reduced, thereby improving transmission characteristics (insertion loss, reflection loss).It is also possible to make the width of the windows W1 and W2 relatively wide to further facilitate alignment.

[0060] Based on the above description, a person skilled in the art may conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. Elements from different embodiments may be combined as appropriate. Various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present invention, which is derived from the content defined in the claims and their equivalents.

[0061] REFERENCE SIGNS LIST 1 coupling waveguide 10, 20 waveguide 11 dielectric layer 12, 13 conductive layer 14, 15, 16, 17 conductive post 30 anisotropic conductive film 40 horn antenna CP conductive particle MSL1, MSL2 microstrip line W1, W2 aperture window

Claims

1. A coupled waveguide comprising: a first waveguide configured to allow radio waves to propagate and having a first opening window for radiating the radio waves to the outside; a second waveguide configured to absorb radio waves from the outside and through which radio waves absorbed from the second opening window propagate, the second waveguide being coupled to the first waveguide such that the second opening window at least partially overlaps the first opening window; and an anisotropic conductive film covering the first opening window and the second opening window and bonding the first waveguide and the second waveguide together.

2. A coupling waveguide according to claim 1, wherein, when the coupling portion between the first waveguide and the second waveguide is viewed in the thickness direction, conductive particles of the anisotropic conductive film are contained in the overlapping portion between the first opening window and the second opening window.

3. The coupling waveguide according to claim 1, wherein the first waveguide comprises: a first dielectric layer having a first main surface and a second main surface; a first conductive layer provided on the first main surface; a second conductive layer provided on the second main surface and having the first opening window; a first post row comprising a plurality of conductive posts that penetrate the first dielectric layer and electrically connect the first conductive layer and the second conductive layer, arranged along the direction of propagation of the radio waves; and a second post row comprising a plurality of conductive posts that penetrate the first dielectric layer and electrically connect the first conductive layer and the second conductive layer, arranged parallel to the first post row.

4. The coupling waveguide according to claim 3, wherein the second waveguide comprises: a second dielectric layer having a third main surface and a fourth main surface; a third conductive layer provided on the third main surface and having the second opening window; a fourth conductive layer provided on the fourth main surface; a third post row comprising a plurality of conductive posts that penetrate the second dielectric layer and electrically connect the third conductive layer and the fourth conductive layer, arranged along the direction of propagation of the radio waves; and a fourth post row comprising a plurality of conductive posts that penetrate the second dielectric layer and electrically connect the third conductive layer and the fourth conductive layer, arranged parallel to the third post row.

5. A connecting waveguide as described in claim 4, wherein the first opening window and the second opening window are slit-shaped extending in a direction perpendicular to the direction of propagation of the radio waves, and the opening widths of the first opening window and the second opening window are the same.

6. The connecting waveguide according to claim 4, wherein the first opening window and the second opening window are slit-shaped extending in a direction perpendicular to the direction of propagation of the radio waves, and the opening widths of the first opening window and the second opening window are different.

7. The coupling waveguide according to claim 3, wherein said second waveguide is a waveguide having said second opening window.

8. The linking waveguide of claim 7, further comprising a horn antenna connected to an end of said waveguide.

9. The coupling waveguide according to claim 1, wherein the first opening window and the second opening window are slit-shaped extending in a direction perpendicular to the direction of propagation of the radio waves, and the size of the conductive particles contained in the anisotropic conductive film is smaller than the width of the slit-shaped first and second opening windows.

10. A waveguide connection method comprising the steps of: preparing a first waveguide configured to allow radio waves to propagate and having a first opening window for radiating the radio waves to the outside; preparing a second waveguide configured to allow radio waves to be absorbed from the outside and through which the radio waves absorbed from the second opening window propagate; and covering the first opening window and the second opening window with an anisotropic conductive film and connecting the first waveguide and the second waveguide so that the first opening window and the second opening window at least partially overlap.

11. The waveguide coupling method according to claim 10, wherein reflection at the coupling portion between the first waveguide and the second waveguide is reduced by increasing the density of conductive particles contained in the anisotropic conductive film.

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