JP2017212312A - Wiring board manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit defects due to excess or deficiency of an energy amount of irradiating light in photo sintering.SOLUTION: A manufacturing method of a wiring board 10 comprises the steps of: forming on a substrate 12, a liquid film 14 where copper oxide particles or noble metal oxide particles are dispersed; dehydrating the liquid film 14 formed on the substrate 12 to form a film body 16; performing photo sintering on the film body 16 formed on the substrate 12 to form a conductive film 18 on the substrate 12. An energy density I (kJ/cm) of irradiating light in the photo sintering, the lower limit Iand the upper limit Iof the energy density of the irradiating light and a thermodiffusion ratio x(mm/s) of the substrate satisfy the following formulas (1)-(3): I≤I≤I(1); I=566ln(x)+1021 (2); I=1891ln(x)+3532 (3).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing a wiring board.

  As a method for forming a conductive thin film on a substrate, a dispersion liquid in which a reducing metal compound and a reducing agent are dispersed is deposited on the substrate as a thin film, and the thin film is exposed to pulsed electromagnetic radiation together with the substrate to form a reducing metal. A method of imparting conductivity to the thin film by chemically reacting a compound and a reducing agent is known (see, for example, Patent Document 1).

Special table 2012-505966 gazette

  A liquid film in which copper oxide particles or noble metal oxide particles are dispersed is formed on a substrate, the liquid film is dried to form a film body, and a photo-sintering process is performed on the film body. When the conductive film is formed on the substrate by applying, if the energy amount of the irradiation light becomes excessive, the substrate is melted or the conductive thin film is peeled off from the substrate, and the energy amount of the irradiation light is insufficient. The conductive film becomes high resistance.

  The problem to be solved by the present invention is to provide a method for manufacturing a wiring board capable of suppressing the occurrence of defects due to excess or deficiency of the amount of energy of irradiation light in the photosintering process.

[1] A method of manufacturing a wiring board according to the present invention includes forming a liquid film in which copper oxide particles or noble metal oxide particles are dispersed on a substrate, and drying the liquid film formed on the substrate. Forming a film body and subjecting the film body formed on the substrate to a photo-sintering process to form a conductive film on the substrate, comprising the following (1) to (3) Formula is satisfied.
I _min ≦ I ≦ I _max (1)
I _min = 566 ln (x) +1021 (2)
I _max = 1891ln (x) +3532 (3)
However, I is the energy density (kJ / cm ³ ) of the irradiation light in the photosintering process, I _min is the lower limit value of the energy density of the irradiation light, and I _max is the energy of the irradiation light. It is an upper limit value of the density, and x is the thermal diffusivity (mm ² / s) of the substrate.

[2] In the above invention, a step of adjusting an energy density I of the irradiation light in the photosintering process may be provided.

  In the present invention, by setting the energy density of the irradiation light in the photo-sintering process based on the thermal diffusivity of the substrate, the occurrence of defects due to excess or deficiency of the energy amount of the irradiation light in the photo-sintering process is suppressed. it can.

FIG. 1 is a process diagram for explaining a method of manufacturing a wiring board according to an embodiment of the present invention. 2A to 2C are cross-sectional views for explaining a method of manufacturing a wiring board according to an embodiment of the present invention. FIG. 3 is a graph showing the relationship between the thermal diffusivity of the substrate at room temperature and the minimum success value. FIG. 4 is a graph showing the relationship between the thermal diffusivity of the substrate at room temperature and the irradiation energy density in the test specimen having a volume resistivity higher than 10 ⁻⁴ Ω · cm. FIG. 5 is a graph showing the relationship between the lower limit value of the irradiation energy density and the thermal diffusivity of the substrate at room temperature in the photosintering treatment represented by the following formula (2). FIG. 6 is a graph showing the relationship between the thermal diffusivity of a substrate at room temperature and the maximum success value. FIG. 7 is a graph showing the relationship between the thermal diffusivity at room temperature of the substrate and the irradiation energy density of the test body in which melting was confirmed and the test body in which peeling was confirmed. FIG. 8 is a graph showing the relationship between the upper limit value of the irradiation energy density and the thermal diffusivity of the substrate at room temperature in the photosintering process represented by the following formula (3).

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The manufacturing method of the wiring board 10 which concerns on one Embodiment of this invention is a method of manufacturing the wiring board 10 using a photosintering process. An example of the wiring board 10 is a flexible printed wiring board such as a membrane switch.

  FIG. 1 is a process diagram for explaining a method for manufacturing a wiring board 10 according to the present embodiment. FIGS. 2A to 2C illustrate a method for manufacturing the wiring board 10 according to the present embodiment. It is sectional drawing for demonstrating.

  First, in step S10 of FIG. 1, as shown in FIG. 2 (A), a dispersion liquid in which copper oxide particles or noble metal oxide particles are dispersed is applied onto the substrate 12, thereby producing copper oxide particles or noble metal. A liquid film 14 in which the oxide particles are dispersed is formed on the substrate 12. Examples of the material constituting the substrate 12 include resin materials such as polyethylene terephthalate (PET), ABS resin, polyimide (PI), and glass materials.

  The dispersion liquid constituting the liquid film 1 contains copper oxide particles or noble metal oxide particles, a binder, and a solvent. Examples of the noble metal oxide particles include oxide particles such as silver (Ag), gold (Au), and platinum (Pt). When it contains copper oxide particles, the content is preferably 70 to 80 wt%. In the case of containing noble metal oxide particles, the content is preferably 75 to 85 wt%.

  Examples of the binder include epoxy resins such as bisphenol A (BPA) type epoxy resins, polyvinyl pyrrolidone (PVP), acrylic resins, and the like. The binder content is preferably 3 to 10 wt%. Examples of the solvent include ester solvents such as diethylene glycol monobutyl ether acetate, hydrocarbon solvents such as ethylene glycol, and the like. It is preferable that the content rate of a solvent is 10-30 wt%.

  A method for applying the dispersion liquid onto the substrate 12 is not particularly limited, and either a contact coating method or a non-contact coating method may be used. Examples of the contact coating method include screen printing, gravure printing, offset printing, gravure offset printing, flexographic printing, and the like. Examples of the non-contact coating method include ink jet printing, spray coating method, dispense coating method, and jet dispensing method.

  Note that the number of times of applying the dispersion liquid onto the substrate 12 is not particularly limited to once, and the dispersion liquid may be applied onto the substrate 12 a plurality of times. Further, the composition of the dispersion may be varied for each application.

  Next, in step S20 of FIG. 1, the film body 16 is formed by drying the liquid film 14 and removing the solvent, as shown in FIG. 2B. In this step, the substrate 12 on which the liquid film 14 has been formed is heated for 60 minutes in a nitrogen atmosphere at 100 to 120 ° C. The film body 16 from which the solvent has been removed is a layer containing copper oxide particles or metal oxide particles and a binder.

  Next, in step S30 of FIG. 1, the photosintering apparatus 1 used in the below-described photosintering process is adjusted. The photosintering apparatus 1 is not particularly limited, and examples thereof include xenon lamps, mercury lamps, metal hydride lamps, chemical lamps, carbon arc lamps, infrared lamps and the like, and laser irradiation apparatuses. Examples of the wavelength component included in the pulsed light emitted from the light source of the photosintering apparatus 1 include visible light, ultraviolet light, and infrared light. The wavelength component included in the pulsed light is not particularly limited as long as it is an electromagnetic wave, and may include, for example, X-rays or microwaves.

In this embodiment, as the photosintering apparatus 1, a photobaking apparatus PulseForge series manufactured by NOVACENTRIX is used. In this step, the irradiance (irradiation energy per unit area) (kW / m ² ) of the photosintering apparatus 1 as a pulsed light irradiation apparatus, pulse irradiation time (irradiation time per pulse) (μs), A pulse irradiation interval (μs) and a processing time (msec) are set. This processing time (msec) is the total time of the time when irradiation is on (hereinafter referred to as irradiation time) (msec) and the time when irradiation is off (msec).

Here, the irradiance (kW / m ² ) and the pulse irradiation time (one pulse) so that the irradiation energy density (irradiation energy amount per unit volume) I (kJ / cm ³ ) satisfies the following formula (1): Per irradiation time) (μs), a pulse irradiation interval (μs), and a processing time (msec) are set.
I _min ≦ I ≦ I _max (1)

I _min in the above formula (1) satisfies the following formula (2), and I _max in the above formula (1) satisfies the following formula (3).
I _min = 566 ln (x) +1021 (2)
I _max = 1891ln (x) +3532 (3)
However, I _min is a lower limit value of the irradiation energy density, I _max is an upper limit value of the irradiation energy density, and x is a thermal diffusivity (mm ² / s) of the substrate 12 at room temperature.

The thermal diffusivity x (mm ² / s) of the substrate 12 satisfies the following formula (4).
x = k / (ρ · C _p ) (4)
Here, k is the thermal conductivity (J / (s · mm · K)) of the substrate 12, ρ is the density (kg / mm ³ ) of the substrate 12, and C _p is the specific heat capacity of the substrate 12. (J / (kg · K)).

The irradiation energy density I (J / cm ³ ) is expressed by the following formula (5).
I = I _A · I _t / t (5)
However, _{I A} is the irradiance, _{I t} is the irradiation time, t is the thickness of the substrate 12.

  Next, in step S40 of FIG. 1, the conductive film 18 is formed by subjecting the film body 16 on the substrate 12 to the light sintering process by the photosintering apparatus 1 under the conditions set in step S30. As shown in FIG. 2C, in this step, the reduction of the copper oxide particles or noble metal oxide particles contained in the film body 16 on the substrate 12 and the metal sintering proceed, whereby the conductive film 18 is obtained. Is formed.

Here, the inventor of the present application sets the irradiation energy density I (kJ / cm ³ ) based on the thermal diffusivity x (mm ² / s) of the substrate 12 as a result of performing the experiment described below. Thus, it has been found that, regardless of the type of the substrate 12, it is possible to suppress the occurrence of defects due to excessive or insufficient irradiation energy amount in the photo-sintering process. Hereinafter, experiments conducted by the inventors of the present application will be described.

In this experiment, specimens 1 to 16 shown in Table 1 below were prepared, and after subjecting these specimens 1 to 16 to a light sintering treatment while increasing or decreasing the irradiation energy density, the presence or absence of melting of the substrate 12 The presence or absence of peeling of the conductive film 18 from the substrate 12 was visually confirmed, and the volume resistivity (Ω · cm) of the conductive film 18 was measured. The volume resistivity (Ω · cm) of the conductive film 18 is a value obtained by multiplying the sheet resistance of the conductive film 18 by the thickness of the conductive film 18. The sheet resistance of the conductive film 18 was measured using a resistivity meter (Loresta GP MCP-T610 type manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The thickness of the conductive film 18 was measured using a micrometer. In the evaluation of the volume resistivity of the conductive film 18, 10 ⁻⁴ Ω · cm or more was set as a high resistance in consideration of use with a flexible printed circuit board such as a membrane switch.

First, the following dispersions A and B were prepared.
<Dispersion A>
Mixture of copper oxide (CuO) particles having an average particle size of 5 μm in a ratio of 75 wt%, polyvinyl pyrrolidone in a ratio of 5 wt%, and diethylene glycol monobutyl ether acetate in a ratio of 20 wt% <Dispersion B>
A mixture of silver oxide (AgO) particles with an average particle size of 5 μm at a ratio of 80 wt%, polyvinyl pyrrolidone at 5 wt%, and ethylene glycol at 15 wt%.

Next, one of the dispersions A and B was applied to one surface of the substrate 12. The coating pattern was solid coating, and the following substrates A, B, C, and D were used.
<Substrate A>
Material: PET, Dimensions (length x width x thickness): 30 mm x 30 mm x 0.155 mm, thermal diffusivity: 0.16 mm ² / s
<Substrate B>
Material: ABS, dimensions (length x width x thickness): 30 mm x 30 mm x 2.0 mm, thermal diffusivity: 0.17 mm ² / s
<Substrate C>
Material: PI, dimensions (length x width x thickness): 30 mm x 30 mm x 0.127 mm, thermal diffusivity: 0.21 mm ² / s
<Substrate D>
Material: alkali-free glass, dimensions (length x width x thickness): 30 mm x 30 mm x 0.70 mm, thermal diffusivity: 0.60 mm ² / s

  Next, the substrate 12 on which the liquid film 14 is formed from either of the dispersions A and B is heated for 60 minutes in a nitrogen atmosphere at 100 ° C. to dry the liquid film 14, thereby forming a film body on the substrate 12. 16 was formed. Finally, the conductive film 18 was formed on the substrate 12 by subjecting the film body 16 formed on the substrate 12 to light sintering. The photosintering process was performed using PulseForge 1300 manufactured by novacentrix.

Specifications of test bodies 1 to 16 produced as described above, conditions for photosintering treatment, measurement results of resistance value of conductive film 18 (volume resistivity (Ω · cm)), and evaluation results of peeling / melting Are summarized in Table 1. In addition, peeling of the electrically conductive film 18 from the board | substrate 12 confirmed visually whether the electrically conductive film 18 lifted or scattered from the board | substrate 12 after the light sintering process. In addition, the melting of the substrate 12 was visually confirmed as to whether or not the waveform of the surface of the substrate 12 was deformed after the photosintering process.

As shown in Table 1, in the test bodies 1 to 11, the volume resistivity of the conductive film 18 was 10 ⁻⁴ Ω · cm or less, and peeling of the conductive film 18 from the substrate 12 and melting of the substrate 12 did not occur. From this result, it can be confirmed that the excess or deficiency of the energy amount of the irradiation light did not occur in the photosintering treatment of the test bodies 1 to 11. On the other hand, in the test body 12, the substrate 12 was melted, and in the test body 13, the conductive film 18 was peeled from the substrate 12. In addition, the volume resistivity of the test bodies 12 and 13 was not measurable. From these results, it can be confirmed that the energy amount of the irradiation light was excessive in the photosintering treatment of the test bodies 12 and 13. Moreover, in the test bodies 14-16, although peeling from the board | substrate 12 of the electrically conductive film 18 and melting | fusing of the board | substrate 12 did not arise, the volume resistivity of the electrically conductive film 18 became higher than 10 ^<-4> ohm * cm. From this result, it can be confirmed that the amount of energy of the irradiation light is insufficient in the photosintering treatment of the test bodies 14 to 16.

Based on the above experimental results, the inventors of the present application examined the optimum value of the irradiation energy density I in the photosintering process. First, a method for setting the lower limit value I _min of the irradiation energy density I in the light sintering process will be described.

  Here, among the test bodies 10 and 11 in which good results were obtained for both the volume resistivity and the presence or absence of peeling and melting, the test body 10 having the smallest irradiation energy density among the test bodies 10 and 11 having the substrate type A. It is. In addition, among the test bodies 1 and 2 in which good results were obtained for both the resistance value and the presence or absence of peeling and melting, the test body 2 has the lowest irradiation energy density among the test bodies 1 and 2 whose substrate type is B. . Further, among the test bodies 7, 8, and 9 in which good results were obtained for both the resistance value and the presence or absence of peeling and melting, the test body 7 had the lowest irradiation energy density among the test bodies 7, 8, and 9 having the substrate type C. It is. Furthermore, the irradiation energy density is the smallest among the test bodies 3, 4, 5, and 6 in which the substrate type is D, which has obtained good results for both the resistance value and the presence or absence of peeling and melting. Is the specimen 3.

  Hereinafter, the irradiation energy density of the test body 10 is referred to as the minimum success value of the substrate A, the irradiation energy density of the test body 12 is referred to as the minimum success value of the substrate B, and the irradiation energy density of the test body 13 is referred to as the minimum success value of the substrate C. The irradiation energy density of the test body 5 is referred to as the minimum success value of the substrate D.

FIG. 3 is a graph showing the relationship between the thermal diffusivity x of the substrates A to D at room temperature and the minimum success value _{Imin_s} . As shown in this graph, the relationship between the thermal diffusivity x of the substrates A to D and the minimum success value I _{min — s} is represented by an approximate curve represented by the following equation (7).
I _min — s = 767.58 × ln (x) +1356.8 (6)

FIG. 4 shows the thermal diffusivity at room temperature of the test body 14 (substrate D), the test body 15 (substrate A), and the test body 16 (substrate C) whose volume resistivity is higher than 10 ⁻⁴ Ω · cm. It is a graph which shows the relationship between x and irradiation energy density. Hereinafter, the irradiation energy density of the test specimen having a volume resistivity higher than 10 ⁻⁴ Ω · cm is referred to as a value exceeding the lower limit. As shown in this graph, the relationship between the thermal diffusivity x of the substrates A, C, and D and the lower limit value _{Imin_f} is represented by an approximate curve represented by the following equation (7).
I _min — _f = 365.02 × ln (x) +685.77 (7)

FIG. 5 is a graph showing the relationship between the lower limit value I _min of the irradiation energy density in the photosintering process represented by the above formula (2) and the thermal diffusivity x of the substrates A to D at room temperature. Here, the approximate curve showing the relationship between the lower limit value I _min of the irradiation energy density in the photosintering process and the thermal diffusivity x of the substrates A to D at room temperature is the thermal diffusivity of the substrates A to D at room temperature. The approximate curve of the above equation (6) showing the relationship between x and the minimum success value _{Imin_s,} and the above equation (7) showing the relationship between the thermal diffusivity x of the substrates A to D at room temperature and the lower limit value _{Imin_f.} It is a curve passing through the middle of the approximate curve. Specifically, the slope (566) of the above formula (2) is an arithmetic average of the slope (767.58) of the above formula (6) and the slope (365.02) of the above formula (7). Further, the intercept (1021) of the above formula (2) is an arithmetic average of the intercept (1356.8) of the above formula (6) and the intercept (685.77) of the above formula (7).

Next, a method for setting the upper limit value I _max of the irradiation energy density in the photosintering process will be described.

  Of the test bodies 10 and 11 in which good results were obtained for both the resistance value and the presence / absence of peeling and melting, the test body 11 has the highest irradiation energy density among the test bodies 10 and 11 having the substrate type A. Moreover, the test body 1 has the highest irradiation energy density among the test bodies 1 and 2 in which good results were obtained for both the resistance value and the presence or absence of peeling and melting, and the substrate type is B. . In addition, among the test bodies 7, 8, and 9 in which good results were obtained for both the resistance value and the presence / absence of peeling and melting, the test body 8 has the highest irradiation energy density among the test bodies 7, 8, and 9 having the substrate type C. It is. Furthermore, the irradiation energy density is the highest among the test specimens 3, 4, 5, and 6 in which the substrate type is D, which has obtained good results for both the resistance value and the presence or absence of peeling and melting. Is the specimen 6.

  Hereinafter, the irradiation energy density of the test body 11 is referred to as the maximum success value of the substrate A, the irradiation energy density of the test body 1 is referred to as the maximum success value of the substrate B, and the irradiation energy density of the test body 8 is the maximum success value of the substrate C. The irradiation energy density of the test body 6 is referred to as the maximum success value of the substrate D.

FIG. 6 is a graph showing the relationship between the thermal diffusivity x of the substrates A to D at room temperature and the maximum success value _{Imax_s} . As shown in this graph, the relationship between the thermal diffusivity x of the substrates A to D and the maximum success value _{Imax_s} is indicated by an approximate curve represented by the following equation (8).
I _max — s = 1016.1 × ln (x) +1937.8 (8)

FIG. 7 is a graph showing the relationship between the thermal diffusivity x at room temperature and the irradiation energy density of the specimen 12 (substrate A) whose melting was confirmed and the specimen 13 (substrate C) whose peeling was confirmed. Hereinafter, the irradiation energy density of the specimen in which melting or peeling is confirmed is referred to as an upper limit exceeded value. As shown in this graph, the relationship between the thermal diffusivity x of the substrates A and C and the upper limit value _{Imax_f} is shown by an approximate curve represented by the following equation (9).
I _max — _f = 2766.31 × ln (x) +5125.7 (9)

FIG. 8 is a graph showing the relationship between the upper limit value I _max of the irradiation energy density in the photosintering process represented by the above formula (3) and the thermal diffusivity x of the substrates A to D at room temperature. Here, the approximate curve showing the relationship between the upper limit value I _max of the irradiation energy density in the photosintering process and the thermal diffusivity x of the substrates A to D at room temperature is the thermal diffusivity x of the substrates A to D and success. Between the approximate curve of the above formula (8) showing the relationship with the maximum value I _{max — s} and the approximate curve of the above formula (9) showing the relationship between the thermal diffusivity x of the substrates A to D and the upper limit value I _{max — f} It is a curve that passes through. Specifically, the slope (1891) of the above formula (3) is an arithmetic average of the slope (1016.1) of the above formula (8) and the slope (276.31) of the above formula (9). The intercept (3532) of the above formula (3) is an arithmetic mean of the intercept (1937.8) of the above formula (8) and the intercept (5125.7) of the above formula (9).

That is, the inventor of the present application has a correlation between the excessive range of the energy density (kJ / cm ³ ) of the irradiation light in the photosintering process and the thermal diffusivity x (mm ² / s) of the substrate 12. In addition, there is a new finding that there is a correlation between the excessive range of the energy density (kJ / cm ³ ) of irradiation light in the photosintering process and the thermal diffusivity x (mm ² / s) of the substrate 12. Obtained by experiment. Therefore, the inventor of the present application sets the lower limit value I _min and the upper limit value I _max of the energy density (kJ / cm ³ ) of the irradiation light in the photosintering process, and sets the thermal diffusivity x (mm ² / s) of the substrate 12. It was defined by an approximate curve as a variable. Thereby, regardless of the type of the substrate 12, it is possible to suppress the occurrence of defects in the photosintering process due to the excess or deficiency of the irradiation energy amount.

  The “wiring board 10” in the present embodiment corresponds to an example of the “wiring board” in the present embodiment, and the “board 12” in the present embodiment corresponds to an example of the “board” in the present invention. The “liquid film 14” corresponds to an example of the “liquid film” in the present invention, the “film body 16” in the present embodiment corresponds to an example of the “film body” in the present invention, and the “conductive film 18” in the present embodiment. Corresponds to an example of the “conductive film” in the present invention.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Light sintering apparatus 10 ... Wiring board 12 ... Board | substrate 14 ... Liquid film 16 ... Film body 18 ... Conductive film

Claims (2)

Forming a liquid film in which copper oxide particles or noble metal oxide particles are dispersed on a substrate;
Drying the liquid film formed on the substrate to form a film body;
A method of manufacturing a wiring board, in which a conductive film is formed on the substrate by subjecting the film body formed on the substrate to a light sintering process,
The manufacturing method of the wiring board which satisfies following (1)-(3) Formula.
I _min ≦ I ≦ I _max (1)
I _min = 566 ln (x) +1021 (2)
I _max = 1891ln (x) +3532 (3)
However, I is the energy density (kJ / cm ³ ) of the irradiation light in the photosintering process, I _min is the lower limit value of the energy density of the irradiation light, and I _max is the energy of the irradiation light. It is an upper limit value of the density, and x is the thermal diffusivity (mm ² / s) of the substrate. It is a manufacturing method of the wiring board according to claim 1,
The manufacturing method of a wiring board provided with the process of adjusting the energy density I of the said irradiation light in the said light sintering process.

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