JP2013089812A - Manufacturing method of conductive complex and printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a conductive complex in which a conductive material and a surface modification fluororesin film of low degree of roughening are bonded with sufficient strength, and to provide a printed wiring board.SOLUTION: In the manufacturing method of a conductive complex, the surface of a base material, i.e., a fluororesin film RF, is irradiated with an ion beam from an anode layer ion source 2 at an irradiation voltage of 1.5-3.5 kV, thus modifying and roughening the surface. A fluid containing particles of a conductive material is then applied to the surface of a surface modification fluororesin film thus roughened and heated, thus bonding the conductive particles to the fluororesin film.

Description

  The present invention relates to a method for producing a conductive composite in which a surface-modified fluororesin film and a conductive material are fixed, and a printed wiring board.

  The fluororesin has an excellent characteristic that both the dielectric constant and the power factor are constant and low regardless of temperature and frequency, and the insulation resistance and dielectric breakdown are also very excellent in the resin. In addition, the fluororesin has high chemical stability and excellent heat resistance. For example, in the case of a tetrafluoroethylene resin (PTFE) called a fluororesin that seems to be a fluororesin, the melting point is 327 ° C., which is higher than other general-purpose resins.

Moreover, since the thinly processed film has appropriate flexibility, it can be used for a flexible substrate (printed wiring board).
However, since the surface of a fluororesin is inactive, it is difficult to adhere to a conductive material, which is a major obstacle to the popularization of products on flexible substrates.
Fluororesin copper-clad laminate with fluororesin impregnated glass cloth and fluororesin sheet as a base material and heat-sealed to copper foil as a printed wiring board substrate utilizing the excellent electrical properties of fluororesin is practical (Non-Patent Document 1).

The copper foil that is heat-sealed to a fluororesin sheet or the like is generally used with a thickness of 30 μm or more for convenience of handling. For this reason, a fine etching process of the circuit is not easy, and there is a problem that the fusion-bonded material is deformed due to the difference in thermal expansion coefficient of each material in the heat-fusion process.
In order to solve this problem, there is a movement aiming for thinning and fine wiring by directly plating copper on the surface of the fluororesin. For fixing the copper thin film to the surface of the fluororesin, it is necessary to modify the surface of the hydrophobic fluororesin to improve the adhesive strength with the copper thin film.

  As a method for modifying the surface of the fluororesin, sodium-ammonia treatment has been proposed in which fluorine atoms on the surface of the fluororesin are extracted with metallic sodium and the surface of the fluororesin is chemically modified (Patent Document 1).

JP 2003-151571 A

Internet, URL: http://www.chukoh.co.jp/japan/laminate/page_title.html

  The surface modification by the sodium-ammonia treatment has a high degree of hydrophilicity and enables strong adhesion to the conductive material. However, since sodium-ammonia treatment is a chemical treatment, it has a problem that the modified layer becomes thick and the modified layer impairs heat resistance and chemical resistance, which are the characteristics of the fluororesin. Further, the fluororesin treated with sodium-ammonia has a large degree of surface roughening and is not preferable as a substrate for a printed wiring board.

  The present invention has been made in view of the above-described problems, and manufacture of a conductive composite in which a conductive material or the like and a surface-modified fluororesin film having a small degree of surface roughening are fixed with sufficient strength. It is an object to provide a method and a printed wiring board.

In the method for producing a conductive composite according to the present invention, the surface of the fluororesin film is irradiated with an ion beam from an anode layer ion source at an irradiation voltage of 1.5 kV to 3.5 kV to roughen the surface, A layer of the conductive particles is formed by applying a fluid containing conductive particles to the surface of the fluororesin film and heating or drying.
The fluororesin film is any one of PTFE, modified PTFE, PFA, and ETFE.

  The printed wiring board according to the present invention comprises a fluororesin film and a conductive material, and the fluororesin film has a surface roughened by receiving an ion beam from an anode layer ion source, The fluid containing the conductive material particles is baked or dried on the roughened surface of the fluororesin film, so that the conductive material particles enter the roughened surface of the fluororesin film and anchor. Due to the effect, it is fixed to the fluororesin film.

  According to the present invention, it is possible to provide a method for producing a conductive composite and a printed wiring board in which a conductive material or the like and a surface-modified fluororesin film having a small degree of surface roughening are fixed with sufficient strength. it can.

FIG. 1 is a schematic view of a surface modification apparatus. FIG. 2 is an external view of the ion irradiation apparatus. FIG. 3 is a cross-sectional view orthogonal to the longitudinal direction of the ion irradiation apparatus. FIG. 4 is a view showing a state of ion beam irradiation by the ion irradiation apparatus. FIG. 5 is a diagram showing the influence of the irradiation voltage on the peel strength.

FIG. 1 is a schematic view of the surface modification apparatus 1, FIG. 2 is an external view of the ion irradiation apparatus 2, and FIG. 3 is a cross-sectional view orthogonal to the longitudinal direction of the ion irradiation apparatus 2.
The surface modification device 1 is a device for modifying the surface of the fluororesin film RF constituting the conductive composite.
The surface modification device 1 includes a processing chamber 3, an ion irradiation device 2, an ion irradiation moving device, a holding device 4, a front chamber 5, and a vacuum device 6.

The processing chamber 3 is a sealable room that houses the ion irradiation device 2, the ion irradiation moving device, and the holding device 4.
The ion irradiation apparatus 2 is a rectangular parallelepiped as a whole, and includes a slit 11, a space 12, an anode 13, and a gas flow path 14. The ion irradiation apparatus 2 is an anode layer ion source in which an anode layer type hole thruster is improved.

The slit 11 is a gap formed on one elongated surface 15 (hereinafter referred to as “irradiation side surface 15”) of the ion irradiation apparatus 2 in which both short side edges are curved in an arc shape and both long sides are straight loops. A portion inside the slit 11 in a portion forming the irradiation side surface 15 is called an inner pole 16, and a portion outside the slit 11 is called an outer pole 17.
In the ion irradiation apparatus 2, the material having at least the irradiation side surface 15 is made of a ferromagnetic material, and the inner pole 16 is converted into the S pole by the permanent magnet incorporated into the ion irradiation apparatus 2, and the outer pole 17 is the N pole. The magnetic poles.

The space 12 is a loop-shaped cavity corresponding to the shape of the slit 11 which is provided inside the ion irradiation apparatus 2 and communicates with the outside through the slit 11 and has a width larger than that of the slit 11.
The anode 13 is a loop electrode accommodated in the loop space 12. The anode 13 is made of copper or a copper alloy.

The gas flow path 14 is a flow path for introducing a gas serving as an ion source into the space 12 from the outside of the ion irradiation apparatus 2.
In the ion irradiation apparatus 2, the outer electrode 17 is grounded (earthed), and the anode 13 is connected to a DC power source.
In the ion irradiation apparatus 2, a portion forming the irradiation side surface 15 (may be abbreviated as “irradiation side surface 15”) is grounded, and a voltage is applied between the anode 13. Further, the ion irradiation apparatus 2 has a magnetic field with respect to an axial electric field at the opening portion of the slit 11 because the inner pole 16 is a magnetic pole to the S pole and the outer pole 17 is a magnetic pole to the N pole. It is formed so as to be substantially orthogonal.

In the vicinity of the slit 11 in the loop-shaped space 12 of the ion irradiation apparatus 2, an irradiation side surface 15 is provided.
By the electrons moving between the anode 13 and the anode 13, the gas supplied from the gas flow path 14 is turned into plasma, and ionization is generated. The generated electrons are directed to the irradiation side surface 15, and the ions are accelerated by a thin layer (anode layer) between the anode 13 and the slit 11 and emitted from the slit 11 to the outside.

  The ion irradiation moving device is a device for reciprocating the ion irradiation device 2 in the horizontal direction. The ion irradiation moving device holds the ion irradiation device with the longitudinal direction of the ion irradiation device 2 orthogonal to the horizontal direction (with the longitudinal direction set to the vertical direction). The ion irradiation moving device is designed such that the angle α between the irradiation side surface 15 of the ion irradiation device 2 and the moving direction can be arbitrarily changed in the range of 0 degrees to 90 degrees. The ion irradiation moving device can be operated by changing various moving conditions such as the reciprocating moving speed, the stationary time at the forward and backward movement ends, the number of movements (the forward movement and the backward movement are each once), etc. Can do. The ion irradiation moving device may be configured such that the ion irradiation device 2 moves in the vertical direction, or moves in a direction that is neither horizontal nor vertical.

The holding device 4 is a device for holding the fluororesin film RF to be modified. The holding device 4 includes a thick and strong rectangular glass substrate 21. The glass substrate 21 is incorporated in the holding device 4 so that the surface thereof is vertical.
The holding device 4 can stand still at a position where the distance in the direction orthogonal to the reciprocating direction between the surface of the glass substrate 21 and the ion irradiating device 2 is constant at any position of the ion irradiating device 2 that reciprocates. Arranged. The reason that “can be stationary” is that the holding device 4 can move between the processing chamber 3 and the front chamber 5 as described later.

The front chamber 5 is a sealable room in which the holding device 4 can be accommodated. The front chamber 5 is connected to the processing chamber 3 and is separated from the processing chamber 3 by a door that can be opened and closed remotely. The holding device 4 can move between the front chamber 5 and the processing chamber 3, and the movement of the holding device 4 between the front chamber 5 and the processing chamber 3 is performed from the outside together with the opening and closing of the door separating them. This is done by remote control.
The vacuum device 6 includes a front vacuum pump 25, a rear vacuum pump 26, and a plurality of automatic valves 27, 28, 29, 30, 31.

The pre-stage vacuum pump 25 is an outline pump that is operated at a stage where the degree of vacuum is low, and an oil rotary pump is used. The front-stage vacuum pump 25 is connected to the processing chamber 3 and the front chamber 5 via automatic valves 27 and 28.
The rear vacuum pump 26 is a vacuum pump that is operated to obtain a high degree of vacuum, and a cryopump is used. The rear vacuum pump 26 is connected to the processing chamber 3 via an automatic valve 29.

The automatic valves 30 and 31 are a leak valve for releasing the vacuum state of the front chamber 5 and a leak valve for releasing the vacuum state of the processing chamber 3, respectively.
Next, the surface modification process of the fluororesin film RF by the surface modification apparatus 1 will be described.
FIG. 4 is a diagram showing a state of ion beam irradiation by the ion irradiation apparatus 2.

  First, the fluororesin film RF to be modified is fixed to the glass substrate 21 of the holding device 4. PTFE (polytetrafluoroethylene), modified PTFE (copolymer of 4F monomer and a small amount of perfluoroalkoxide), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), ETFE (Tetrafluoroethylene / ethylene copolymer) is used. Moreover, as for the thickness of a film, 10 micrometers-150 micrometers are preferable.

The fluororesin film RF is cut into a rectangle, and the four corners or two opposite sides are fixed directly or indirectly to the glass substrate 21. A weak tension is applied to the fluororesin film RF so as not to cause wrinkles.
Referring to FIG. 1, a glass substrate 21 to which a fluororesin film RF is fixed is integrated with the holding device 4 in the front chamber 5.

The front chamber 5 and the processing chamber 3 are sealed and shut off from the outside. The door separating the front chamber 5 and the processing chamber 3 is opened.
With the automatic valves 27, 28 opened and the automatic valves 29, 30, 31 closed, the vacuum device 6
The front-stage vacuum pump 25 is activated, and the front chamber 5 and the processing chamber 3 are depressurized.
When the front chamber 5 and the processing chamber 3 reach a predetermined degree of vacuum, for example, 10 ² Pa, the holding device 4 is moved from the front chamber 5 to the processing chamber 3 and the door between the front chamber 5 and the processing chamber 3 is closed. It is done.

  The fluororesin film RF moved into the processing chamber 3 is disposed at an appropriate position according to the distance from the ion irradiation device 2 and the ion irradiation angle α. Here, the ion irradiation angle α is an angle formed by the irradiation direction of the ion beam irradiated to the modification target (fluororesin film RF) and the direction orthogonal to the modification surface. The ion irradiation angle α is the same value as the angle α between the irradiation side surface 15 and the moving direction of the ion irradiation moving device.

The fluororesin film RF is fixed to the glass substrate 21 so that any two opposing sides coincide with the longitudinal direction of the ion irradiation device 2.
Subsequently, when the automatic valves 27 and 28 are closed, the automatic valve 29 is opened, and the front vacuum pump 25 is stopped, the rear vacuum pump 26 is started. The processing chamber 3 is depressurized to a higher degree of vacuum, for example, 10 ⁻² Pa, by the rear vacuum pump 26.

  The ion irradiation device 2 is attached to the ion irradiation moving device so that the angle α between the irradiation side surface 15 and the moving direction of the ion irradiation moving device becomes a set angle. A gas to be ionized is supplied from the gas flow path 14 to the ion irradiation device 2 at a predetermined flow rate. As the gas to be ionized, for example, argon gas, oxygen gas or nitrogen gas is preferable, and these are used alone or in combination. Of these, an argon gas that hardly generates chemically active functional groups is particularly preferable.

When the degree of vacuum in the processing chamber 3 is stabilized at the set value, the ion irradiation device 2 is activated, the ion beam is irradiated onto the fluororesin film RF, and surface modification is started. The ion irradiation apparatus 2 is moved in the horizontal direction from one moving end to the other moving end at a predetermined moving speed by the ion irradiation moving apparatus.
After the ion irradiation apparatus 2 has moved from one of the moving ends to the other moving end for the set number of times, the movement of the ion irradiation apparatus 2 and its operation are stopped, and the surface modification is completed. The surface modification performed here is to roughen the surface by destroying the surface of the fluororesin film RF and the internal molecular structure in the vicinity of the surface by the irradiated ion beam.

  On the fluororesin film RF whose surface has been modified in this way, a predetermined circuit pattern by a fluid containing conductive particles is printed using a known coating technique such as a screen printing method or an ink jet printing method. Examples of the fluid containing conductive particles include a commercially available conductive paste, for example, manufactured by Fujikura Kasei Co., Ltd. containing silver, product names Dotite (registered trademark) FA-333, FA-353N, XA-602N, and Toyo also containing silver. Made of spinning, product name: VYLON (registered trademark), DW-250H-5, 23, DW-260H-1, manufactured by Daiken Chemical Industry Co., Ltd., product name: CA-6178, etc., and conductive material containing copper or conductive carbon Sex paste is used.

The material of the conductive particles to be applied is not particularly limited, but it is preferable that the electric resistance is small and the stability of the formed circuit is good. As the conductive material, copper is preferable in addition to the above-described silver in terms of low firing temperature and electrical properties. The size of the conductive particles is preferably in the nano order for miniaturization of the wiring.
The fluororesin film RF on which the circuit pattern is formed with a fluid containing conductive particles is subjected to a treatment for fixing the conductive particles. In the fixing treatment, in order to thermally cure or dry the dispersion medium of the conductive particles, the dispersion medium is heated to an appropriate treatment temperature for heat curing, or heating and decompression for evaporation of the dispersion medium are performed. After the fixing process, a flexible electronic circuit board in which a circuit pattern made of a conductive material is formed on the surface of the fluororesin film RF is obtained.

  Table 1 shows the results of evaluating the surface modification conditions of the fluororesin film RF performed using the surface modification apparatus 1 and the surface-modified fluororesin film RF. The “peel strength” in Table 1 is the peel strength between the fluororesin film RF and the conductive metal fixed on the surface thereof. “0.1>” in the column of peel strength in Table 1 indicates that the peel strength could not be measured accurately because it was hardly fixed.

Common conditions for surface modification and vulcanization adhesion are shown below.
(1) Ion irradiation device: IZOVA BEAM CLEANING made by IZOVAC
The SYSTEM (anode layer ion source) / ion irradiation device is driven by a drive device of Run Technical Service Co., Ltd. (2) Setting vacuum: 10 ⁻² Pa
(3) Fluororesin film: PTFE-made by Nippon Valqua Industries, VALFLON (registered trademark), thickness 100 μm
(4) Distance between the ion irradiation device and the fluororesin film: distance from the center in the width direction of the irradiation side surface 15 (symbol C in FIGS. 3 and 4) to the fluororesin film in the direction orthogonal to the moving direction of the ion irradiation device 2 ( 4) D) is 100 mm
(5) Fluid containing conductive particles: Daiken Chemical Industries, Ltd., thermosetting type conductive paste CA-6178 containing silver particles
(6) Application treatment of fluid containing conductive particles to fluororesin film: Application by applicator to a thickness of 50 μm (7) Fixing condition: temperature 130 ° C., treatment time 30 minutes In Table 1, “Irradiation voltage” "Is a DC voltage applied between the anode 13 and the irradiation side surface 15 of the ion irradiation apparatus 2, and" movement speed "is the speed at the time of movement of the ion irradiation apparatus 2 in FIG. The number of movements is one movement for one way.

The presence or absence of discoloration in Table 1 was visually observed for the surface-modified fluororesin film.
The peel strength was measured as follows.
First, two fluororesin films RF that have been surface-modified while leaving an unmodified surface are fixed by a fluid containing conductive particles with the modified surfaces facing each other. This is cut into a strip shape with a width of 20 mm to be a measurement sample so that the portion (fluororesin film RF) which is not fixed and separated (because it has not been modified) becomes one side in the longitudinal direction. A sample for measurement (Comparative Example 1) was similarly prepared for the fluororesin film RF that was not subjected to surface modification.

  Resistance force when the fluororesin film RF separated without fixing on one side in the longitudinal direction of the measurement sample is sandwiched between separate upper and lower chucks of the peel strength tester and the upper chuck is raised at a speed of 50 mm / min. Was measured to determine the peel strength (adhesion strength) between the fluororesin film RF and the conductive particle layer. At this time, a peeling test was performed under a so-called 90-degree peeling condition so that the portion to which the fluororesin film RF was fixed was horizontal with respect to the fluororesin film RF held by the upper and lower chucks.

FIG. 5 is a graph showing the influence of the irradiation voltage on the peel strength from the results shown in Table 1.
From Table 1 and FIG. 5, by setting the irradiation voltage to 1.5 kV or more, the peel strength between the fluororesin film RF and the conductive particle layer can be set to 1.3 N / mm or more, which is a practically sufficient strength. it can.
Further, from FIG. 5, by setting the irradiation voltage to 1.5 kV or more and 3.5 kV or less, sufficient peel strength can be obtained between the conductive particle layer without coloring the fluororesin film RF.

Table 2 shows the center line average roughness (Ra) and ten-point average roughness (Rz) of the fluororesin film RF and the fluororesin film RF surface-modified by sodium-ammonia treatment in Example 2 and Example 1. It is the result of measurement.
The measurement of the center line average roughness and the ten-point average roughness was performed in accordance with JIS B0601: 2001. The equipment used was Surfcom 130A manufactured by Tokyo Seimitsu Co., Ltd., with a cutoff value of 0.25 mm and a measurement length of 1.25 mm.

  From Table 2, the fluororesin film RF surface-modified by ion beam irradiation has a less rough surface than the fluororesin film RF surface-modified by sodium-ammonia treatment. It can be seen that this is equivalent to the fluororesin film RF (Comparative Example 1).

Table 3 shows the results of examining the surface composition of the fluororesin film RF by ESCA (Electron Spectroscopy for Chemical Analysis).
In the fluororesin film RF of Example 2 that was surface-modified by ion beam irradiation, fluorine (F) decreased compared to the untreated fluororesin film RF (Comparative Example 1), and carbon (C), oxygen (O ), An increase in elements such as nitrogen (N) is observed. From this, it is presumed that the fluorine atoms on the outermost surface are extracted, and a small amount of O and N that are considered to be derived from air are taken in.

In addition, as a result of observing the surface shape by SPM (scanning probe microscope), the fluororesin film after the surface modification in Example 2 has a surface area of 1.6% before the surface modification. After the modification treatment, the projected area ratio increased to 15.9%.
Also, by observation with an image of SPM and observation with a scanning electron microscope (SEM), fine irregularities were observed on the surface after the surface modification, and the surface area was increased. This increase in surface area and surface irregularities contribute to an increase in the fixing strength of the conductive particle layer.

The adhesion of the conductive particle layer to the fluororesin film RF is obtained by an anchor effect in which conductive fine particles enter the surface of the modified and roughened fluororesin film RF.
In the above-described embodiment, the voltage applied to the ion beam is preferably 1.5 kV or more and 3.5 kV or less. The effect obtained by processing at a voltage lower than this is weak and undesirable. Processing at higher voltages causes severe degradation of the fluororesin, a decrease in vacuum due to the decomposition gas from the resin, and discoloration of the film, which may be due to collision with high-energy ions. Therefore, it is not preferable.

In general, it is known that in an anode layer ion source, an average energy of about half of the numerical value of the voltage applied to the ion source is given to the ion. When the applied voltage is 1.5 kV to 3.5 kV, the average energy of the ion is given. Is about 0.8 to 1.8 keV.
As the number of ions per unit area irradiated to the fluororesin film RF, an amount necessary for the required adhesive strength may be selected, but it is preferably about 10 ¹³ to 10 ¹⁸ pieces / cm ² . If it is 10 ¹³ or less, the required surface modification cannot be obtained and the adhesive strength is lowered. If it is 10 ¹⁸ or more, the modified surface layer is further decomposed, which is inefficient. When ion irradiation is performed, a necessary number of ions may be irradiated at one time, or the target number of ions may be irradiated by repeatedly performing irradiation with a small number of ions. In order to avoid thermal damage to the fluororesin, it is preferable to reduce the irradiation per time and repeat the treatment a plurality of times.

In the method of performing surface modification by the ion irradiation apparatus 2, an ion beam is irradiated while arbitrarily moving the glass substrate 21 holding the fluororesin film RF in two orthogonal directions in the surface (of the glass substrate 21). Thus, the surface modification can be performed only on a specific portion of the fluororesin film RF.
Arbitrary movement of the glass substrate 21 in two orthogonal directions can be performed by controlling the operation of the holding device 4 by a computer. Thus, by controlling the movement of the glass substrate 21 in two orthogonal directions, fluorine can be obtained. Surface modification limited to the portion of the resin film RF where the conductive material is to be fixed can be performed.

The method of roughening the surface of the fluororesin film RF by irradiating with an ion beam can maintain excellent electrical characteristics and the like possessed by the fluororesin on the surface excluding the surface on which the conductive particle layer is formed.
In addition, each structure of the surface modification apparatus 1 and the surface modification apparatus 1 or the overall structure, shape, dimensions, number, material, and the like can be appropriately changed in accordance with the spirit of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a method for producing a conductive composite in which a surface-modified fluororesin film and a conductive material are fixed, and a printed wiring board.

2 Ion irradiation equipment (anode layer ion source)
RF fluoropolymer film

Claims (3)

Irradiating the surface of the fluororesin film with an ion beam from an anode layer ion source at an irradiation voltage of 1.5 kV to 3.5 kV to roughen the surface,
A method for producing a conductive composite, comprising: applying a fluid containing conductive particles to the surface of the fluororesin film and heating or drying the layer of the conductive particles. The method for producing a conductive composite according to claim 1, wherein the fluororesin film is one of PTFE, modified PTFE, PFA, and ETFE. It consists of a fluororesin film and a conductive material,
The surface of the fluororesin film is roughened by receiving an ion beam from an anode layer ion source,
When the fluid containing the conductive material particles is baked or dried on the roughened surface of the fluororesin film, the conductive material particles enter the roughened surface of the fluororesin film. A printed wiring board formed by being fixed to the fluororesin film by an anchor effect.

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