JP2014103380A - Coating film and formation method of the same, and light-emitting diode device using the coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating film and a formation method of the same, capable of preventing a color change caused by corrosion of a metallic material surface even when used in heat processing at production or in an outdoor environment for a long term, and capable of forming a coating film excellent also in wire-bonding characteristics on a metallic material surface.SOLUTION: Under an ambient pressure, a hexamethyldisiloxane compound is mixed with a nitrogen gas as a carrier gas and sprayed into a nitrogen plasma gas, the hexamethyldisiloxane compound is polymerized by being made a radical, and a polysiloxane film of a thickness of 4 nm to 14 nm, composed of polysiloxane whose main chain is -(Si-O-Si)- is formed on a metallic material surface.

Description

  The present invention relates to a coating film formed on the surface of a metal material, particularly silver or a silver alloy, a method for forming the coating film, and a light-emitting diode device including the coating film.

  Connectors and lead frames, which are connection parts for electronic devices, are often made of copper alloy-based materials such as brass and phosphor bronze, with copper or nickel underplating, and then silver plating on top. Yes. Since silver is a good conductor of electricity and heat, it is widely used as a plating material for connectors and lead frames. However, the silver plating material is easily discolored in the air, and in particular, corrodes in an atmosphere containing sulfur and changes its color to brown or blue-black, resulting in poor electrical contact.

  By the way, in recent years, the use of a white light emitting diode device has attracted attention as a new light source and lighting fixture to replace incandescent bulbs and fluorescent lamps from the viewpoints of energy saving and environmental conservation. A light-emitting diode (LED) device is designed so that a pedestal of a lead frame is processed and an LED chip is placed at a position surrounded by a reflective portion, and light emitted from the LED chip can be efficiently extracted by the reflective portion. . If necessary, the LED chip is sealed with an epoxy resin or the like.

  A metal film such as silver, aluminum, or gold is used as a reflective material used in the reflective portion of the LED device. In particular, silver is the most suitable material as a reflector because of its high glossiness and high reflectance. However, depending on the environment, silver may be discolored due to oxidation or sulfuration, and such discoloration deteriorates the performance of the silver film as a reflector. In particular, in LED devices, there is a problem of deterioration in light reflection performance due to discoloration due to heat treatment in the LED manufacturing process or discoloration due to use in a high temperature environment.

  In order to avoid these problems, surface treatment is performed on the metal film. Specifically, discoloration due to corrosion is prevented by treating the surface of these metal films with a predetermined treatment liquid.

  For example, JP-A-5-311492 describes a method of treating a silver plating material in a solution containing an inhibitor (corrosion inhibitor). Japanese Patent Application Laid-Open No. 9-249977 describes a method of applying a surface treatment liquid containing a lubricant and an emulsifier to a specific inhibitor such as benzotriazole. In these methods, a certain effect of preventing discoloration due to corrosion of the silver-plated material is recognized, but the preventive effect is not sufficient, and partial discoloration is unavoidable depending on the use environment.

  On the other hand, in JP 2004-169157 A, for the purpose of improving the strength and corrosion resistance of the silver plating layer, the silver plating layer is composed of an organic compound having a thione group or a mercapto group, a nitrogen-containing heterocyclic compound, A method of treating with an organic compound that reacts or has an affinity for silver is described. However, the corrosion resistance in this technique is merely an evaluation of peeling and clouding in the case of spraying an aqueous solution in which a small amount of acetic acid and cupric chloride is added to 5% by mass saline, and in an atmosphere containing sulfur. The relationship between discoloration due to corrosion, heat treatment in LED manufacturing processes, and heat resistance in high temperature environments is unclear.

  In addition, JP 2011-202239 A discloses a surface treatment agent containing a specific inhibitor such as benzotriazole, iodide and / or bromide, and having a pH adjusted to 4-7. The publication describes a method of direct current electrolysis using a metal material as an anode to a surface treatment agent containing a specific inhibitor such as benzotriazole and having a pH adjusted to 4-7. According to these, a coating film with improved heat resistance is said to be obtained. However, they cannot be colored practically because the coating film itself is inevitably colored, and the denseness and sulfidation resistance of the coating film are not sufficient.

  As described above, the conventional surface treatment agent has a problem that it is inferior to any of the denseness, sulfidation resistance, and heat resistance of the obtained coating film. Even if it is used for coating surface treatment, if corrosive gas permeates during product manufacture or use, the coating film's anti-discoloration properties will deteriorate and the light reflection performance of the metal coating will deteriorate. The problem arises. In addition, since both are wet surface treatments, it is difficult to uniformly form a thin coating film having a thickness of 100 nm or less. The reflective part of the LED device is also a kind of connection part such as a lead frame, and wire bonding is used for connection to the LED chip, etc., but when the coating film is too thick or the wettability is inferior There is a problem in wire bonding properties, and the bonding may be insufficient.

Japanese Patent Application Laid-Open No. 2010-58111 relates to the formation of a reflecting surface of a reflector in a vehicle lamp. A plasma CVD method is used on a base material to form a reflecting layer such as an undercoat layer, a silver deposited film, etc. A dry surface treatment for laminating a coat layer is described. In this method, a silicon oxide film (SiO _x film) formed by plasma polymerization using a silane compound such as hexamethyldisiloxane (HMDSO) is used for the undercoat layer and the topcoat layer. According to this dry surface treatment, a coating structure can be obtained in which the metal film and the coating film can be formed in a shorter time than the wet surface treatment, and the reflection efficiency does not decrease. In addition, since the film forming material does not diffuse into the factory, the working environment can be maintained well. However, the surface treatment by the plasma CVD method is generally expensive and requires a large vacuum apparatus or a decompression apparatus, which causes an increase in production cost and deterioration of productivity.

  Japanese Patent Application Laid-Open No. 2004-510571 discloses a polymer formation by introducing a spray liquid coating material made of an organosilicon compound such as dimethylsiloxane into an atmospheric pressure plasma discharge and exposing a substrate such as a metal to the spray coating material. Disclosed is a method of polymerizing the material to form a coating that protects the substrate from corrosion and provides a barrier to oxidation. Further, it is described that a coating derived from siloxane can be oxidized by an oxygen-containing plasma treatment, and a siloxane polymer can be formed by a plasma treatment under non-oxidizing conditions. However, in this technique, the activation of the raw material which is converted into plasma and atomized at the same time is performed at the same time, so that the activation of the raw material becomes non-uniform, resulting in a uniform polysiloxane film. There is a problem that can not be. In addition, the thickness of the coating film formed by this technique is about 300 nm. For this reason, it is difficult to apply as a coating film for the reflective portion of the LED device from the viewpoint of bonding properties.

JP-A-5-311492 Japanese Patent Laid-Open No. 9-249977 JP 2004-169157 A JP 2011-202239 A JP 2011-241409 A JP 2010-58111 A JP 2011-102042 A JP 2004-510571 A

  The present invention can prevent discoloration due to corrosion of the surface of a metal material, particularly a silver plating material, even by heat treatment during production or use in an outdoor environment for a long period of time, and also in wire bonding characteristics. An object is to provide an excellent coating film and a method for forming the coating film on the surface of a metal material.

  The coating film of the present invention is a coating film formed on the surface of a metal material, and includes an organosilicon compound having a siloxane bond in a nitrogen plasma gas at least under atmospheric pressure together with a carrier gas containing at least nitrogen. It is characterized by comprising a polysiloxane film having a thickness of 4 nm to 14 nm, which is formed by mixing spraying, radicalizing and polymerizing the organosilicon compound.

The polysiloxane film is preferably composed of a polysiloxane whose main chain is — (Si—O—Si) _n —, and a polysiloxane (general formula: R) mainly having an alkyl group connected to a side chain. ₃ SiO— (R ₂ SiO) _n —SiR ₃ ) (R is an arbitrary alkyl group) is more preferable, and R in the general formula is a dimethylpolysiloxane having a methyl group. Is particularly preferred.

  The coating film of the present invention is suitably applied to a light emitting diode (LED) device. That is, the LED device of the present invention includes a lead frame, a reflection part obtained by processing a pedestal of the lead frame, and an LED chip placed at a position surrounded by the reflection part, and the reflection device The portion includes a metal film and the coating film of the present invention formed thereon. In addition, this invention is applied suitably when the said metal film is a silver film or a silver alloy film.

  When the reflective part is composed of a silver film or a silver alloy film and the coating film formed thereon, the lightness L value of the reflective part is preferably 80 or more, and is 84 or more. Is more preferable.

  On the other hand, in the method for forming a coating film of the present invention, an organic silicon compound having a siloxane bond is mixed and sprayed together with nitrogen gas in a nitrogen plasma gas under atmospheric pressure to radicalize the organic silicon compound. The polysiloxane film obtained by polymerization is formed on the surface of the metal material with a thickness of 4 nm to 14 nm.

  In the present invention, the organosilicon compound is at least one selected from hexamethyldisiloxane (HMDSO), octamethyltrisiloxane (OMTSO), decamethyltetrasiloxane (DMTSO), and octamethylcyclotetrasiloxane (OMCTSO). It is preferable to use seeds. In particular, it is more preferable to use hexamethyldisiloxane.

  For forming the coating film, using an atmospheric pressure plasma polymerization processing apparatus, the distance from the supply nozzle of the apparatus to the surface of the metal material is 5 mm to 30 mm, and the moving speed of the supply nozzle is 10 m / min to It is preferable to carry out at 40 m / min.

The polysiloxane film is preferably composed of a polysiloxane having a main chain of-(Si-O-Si) _n- , and a polysiloxane having a main chain mainly connected to an alkyl group (general formula : R ₃ SiO— (R ₂ SiO) _n —SiR ₃ ) (R is an arbitrary alkyl group) is more preferable, and R is a dimethylpolysiloxane having a methyl group. It is particularly preferable that

  The present invention is suitably applied when the metal material is silver or a silver alloy.

  According to the present invention, a transparent, extremely thin and uniform coating film can be formed on a surface of a metal material in a short time. For this reason, appearance defects such as processing unevenness and spots due to surface treatment hardly occur. In addition, since the coating film obtained by the present invention is excellent in sulfidation resistance and oxidation resistance, it is highly effective in preventing discoloration due to corrosion, and does not cause problems such as deterioration of reflection characteristics. Excellent bonding characteristics.

  In addition, according to the present invention, since the polymerization reaction of the organosilicon compound can proceed efficiently under atmospheric pressure without using a vacuum device or a decompression device, the device configuration can be simplified and the productivity can be improved. Improvements and reductions in production costs can be achieved.

  The coating material used in the atmospheric pressure plasma polymerization treatment of the present invention is a liquid organosilicon compound, which is liquid at room temperature and does not contain organic solvents or heavy metals, and is therefore easy to handle. Excellent safety.

  Hereinafter, an example of an embodiment of the present invention will be described in detail for a coating film and a method for forming the coating film.

1. Coating Film The coating film of the present invention is a coating film formed on the surface of a metal material, and contains at least nitrogen with an organosilicon compound having a siloxane bond in a nitrogen plasma gas under atmospheric pressure. It is characterized by comprising a polysiloxane film having a thickness of 4 nm to 14 nm formed by an atmospheric pressure plasma polymerization process in which the organic silicon compound is radicalized and polymerized by being mixed and sprayed with a carrier gas.

  The material for forming the coating film of the present invention is not particularly limited as long as it is a metal material, and the present invention can be applied to any metal material. However, it is particularly suitable for a silver or silver alloy material that easily changes color in an outdoor environment.

  The coating film of the present invention can also be applied to connectors and lead frames, which are connection parts for ordinary electronic equipment, where deterioration of electrical contact due to corrosion is a problem. It is suitable for a reflection part of a light emitting diode (LED) device in which deterioration of light reflection characteristics becomes a problem due to the influence of heat history during use or use.

(Polysiloxane film)
The type of polysiloxane constituting the polysiloxane film of the present invention is arbitrary, but considering the effect of the present invention, that is, transparency as a reflection / transmission film (being uncolored), denseness as a film, It is preferable that the main chain is composed of polysiloxane having — (Si—O—Si) _n — (siloxane bond). Examples of such polysiloxanes include polysiloxanes represented by the general formula: R ₃ SiO— (R ₂ SiO) _n —SiR ₃ (R is an arbitrary alkyl group), and side chains of R in the above general formula. A polysiloxane having a structure in which a part of the compound is substituted with a phenyl group (—C ₆ H ₅ ) and a polysiloxane having a structure in which carbon is partly substituted with an organic group. Note that the organic group in the present invention, means a functional group containing at least one carbon, for example, an amino group (-RNH _2), carboxyl group (-RCOOH), carbinol group (-ROH), polyether group (-C _n H _{2n + 1)} and the like.

Among these, from the viewpoint of obtaining a highly flexible coating film, the polysiloxane represented by the general formula is more preferable, and from the viewpoint of obtaining a denser coating film, dimethylpolysiloxane in which R is a methyl group. _{(structure: (CH 3) 3 SiO -} [(CH 3) 2 SiO] n -Si (CH 3) 3) is more preferable.

(Film thickness)
The thickness of the coating film (polysiloxane film) of the present invention is in the range of 4 nm to 14 nm, preferably in the range of 6 nm to 12 nm. If the thickness of the coating film is less than 4 nm, corrosion resistance, particularly sufficient sulfidation resistance cannot be obtained, so that the effect of preventing discoloration due to corrosion cannot be sufficiently obtained. Further, when the coating film of the present invention is formed on a metal film, the effect of improving the brightness cannot be obtained sufficiently. On the other hand, if it exceeds 14 nm, the corrosion resistance is sufficient, but the yellowish coloring becomes conspicuous and not only the brightness and appearance characteristics are deteriorated, but also the wire bonding characteristics are deteriorated. In addition, since the insulating property becomes too high, there is a problem that the contact resistance increases.

(Characteristic)
Even if the coating film of the present invention is a very thin film, it becomes a dense protective film and is formed uniformly over the entire surface of the metal material. For this reason, the metal material which exists inside can be protected reliably. As a result, the corrosion resistance (sulfuration resistance and oxidation resistance) of metal materials is excellent, and in particular, the resistance to discoloration (discoloration resistance) caused by corrosion due to sulfidation is used when a conventional surface treatment agent containing an inhibitor is used. Compared with, it can be remarkably improved.

  In addition, the metal material on which the coating film of the present invention is formed can have excellent wire bonding characteristics that mean the bonding strength with the bonding wire. The wire bonding characteristic is usually that a predetermined bond tester is used to clamp the bonding wire bonded to the sample (mating surface) and pull it 90 ° to cut the 2nd bonding portion. It is evaluated by. That is, if the break position is a wire portion, it is evaluated that the wire bonding property is high (bonding strength is sufficiently high), and if the break position is a bonding interface, the wire bonding property is low (bonding strength is insufficient). It is evaluated.

Furthermore, by forming the coating film of the present invention on the surface of the metal material with an appropriate thickness, the L value indicating the brightness (brightness) can be greatly improved. For example, by coating a metal film made of silver or a silver alloy (lightness L value: 70 to 75) with the coating film (polysiloxane film) of the present invention within the range of the film thickness defined by the present invention, The brightness L value can be 80 or more, preferably 84 or more. Here, the lightness L value is defined by the L ^* a ^* b color system (JIS Z8729) where the lightness axis is L ^* , the chromaticity red and green axes are a ^* , and the chromaticity yellow and blue axes b ^* . The value of the lightness axis L ^* when a color is displayed. The lightness L value can be obtained by a spectral colorimeter, assuming that the black lightness L value is 0 and the white lightness L value is 100.

  In addition, since this coating film is formed very firmly, it has the characteristics of high stability and very little deterioration with time. For this reason, even if the metal material in which this coating film was formed was exposed to the outdoor environment for a long period of time, all the above-mentioned characteristics can be maintained in a high state.

2. Next, the method for forming the coating film of the present invention will be described. The polysiloxane film constituting the coating film of the present invention can be formed only by the atmospheric pressure plasma polymerization treatment under limited conditions, that is, the coating film forming method of the present invention.

  Plasma treatment is a technique that has been widely known in the past, but the atmospheric pressure plasma polymerization treatment of the present invention utilizes the feature that a chemical reaction that does not proceed under normal conditions proceeds by activation of reactive particles by atmospheric pressure plasma. It is. Atmospheric pressure plasma is characterized by high productivity because it is suitable for continuous processing, low processing costs because it does not require a vacuum device, and a simple apparatus configuration. The atmospheric pressure plasma in the present invention can be generated by any method such as corona discharge, dielectric barrier discharge, RF discharge, microwave discharge, or arc discharge.

(Plasma gas and carrier gas)
In the conventional plasma treatment, it is common to use an inert gas such as argon (Ar) or helium (He) as the plasma gas and the carrier gas. However, in the atmospheric pressure plasma polymerization treatment of the present invention, it is not essential to use these expensive inert gases, and any carrier gas and plasma gas (ionizing gas) may be used as long as they contain at least nitrogen. be able to. That is, it is possible to use a mixed gas of nitrogen and oxygen that usually contains the atmosphere. Since such a mixed gas is inexpensive and easy to handle, not only can productivity be improved, but also workability can be improved.

  In order to generate nitrogen plasma, the nitrogen content in the plasma gas and the carrier gas is preferably in the range of 30% to 100% by volume. By setting the nitrogen content to 30% by volume or more, oxidation of the organosilicon compound as a coating material by oxygen is prevented, and radicalization can be performed while maintaining the basic skeleton.

However, even if the nitrogen content is 30% by volume or more, depending on the processing conditions, the temperature becomes high in the process of oxygen or air being plasmatized, and the organosilicon compound as the coating material is oxidatively decomposed and obtained. The coating film may become a silicon oxide (SiO _x ) film. In such a case, the content of nitrogen in the plasma gas and the carrier gas is increased to preferably 40% by volume to 100% by volume, more preferably 100% by volume, so that the organosilicon compound is oxidatively decomposed. Can be suppressed.

  In addition, as an apparatus used for converting a gas containing at least nitrogen, preferably nitrogen gas into plasma, there is no particular limitation as long as it can be converted into plasma under atmospheric pressure, and any known plasma can be used. A generator can be used. Here, the atmospheric pressure in the present invention includes atmospheric pressure (1013.25 hPa) and atmospheric pressure in the vicinity thereof, and also includes atmospheric pressure within a range of changes in normal atmospheric pressure.

(Plasmaization conditions)
Conditions for converting plasma gas (nitrogen gas, etc.) into plasma should be selected as appropriate depending on the performance of the equipment used and the desired film thickness. The generator output voltage is preferably in the range of 150V to 350V, more preferably in the range of 200V to 330V, from the viewpoint of radicalization well and forming a high-quality coating film. When the generator output voltage is less than 150 V, the nitrogen gas cannot be sufficiently converted to plasma, and therefore the organosilicon compound cannot be sufficiently radicalized. In addition, when the generator output voltage exceeds 350 V, there is a possibility that a problem of damage to the apparatus occurs.

(Coating material)
As the coating material in the present invention, an organic silicon compound which is liquid at normal temperature and has a siloxane bond can be used. By using such an organosilicon compound, a coating film made of polysiloxane represented by the general formula: R ₃ SiO— (R ₂ SiO) _n —SiR ₃ (R is an arbitrary alkyl group) is formed. be able to.

  Examples of the organosilicon compound include straight-chain siloxanes such as hexamethyldisiloxane (HMDSO), octamethyltrisiloxane (OMTSO), decamethyltetrasiloxane (DMTSO), and cyclic siloxanes such as octamethylcyclotetrasiloxane (OMCTSO). At least one organosilicon compound selected from the group consisting of: Among these coating materials, hexamethyldisiloxane (HMDSO) represented by the following (Formula 1) has a boiling point of 99.5 ° C., is a colorless and odorless liquid, and is stable in air. , And can be preferably used because of its easy handling.

Formula 1

When these organic silicon compounds are used to form the coating film of the present invention, the coating film is formed from dimethylpolysiloxane (structural formula: (CH ₃ ) ₃ SiO — [(CH ₃ ) ₂ SiO]. can be constituted by _{n -Si (CH 3) 3)} .

In addition, as described above, the coating film of the present invention is obtained by forming a part of the side chain of R in the general formula: R ₃ SiO— (R ₂ SiO) _n —SiR ₃ (R is an arbitrary alkyl group) When the polysiloxane having a structure substituted with a phenyl group or a polysiloxane having a structure in which carbon is combined and substituted with an organic group, a part of the side chain of the organosilicon compound is previously substituted with a phenyl group. Alternatively, a material substituted with an organic group may be used as a coating material. Or you may use the mixture which consists of the said organosilicon compound and the other compound which has a phenyl group or an organic group as a coating | coated material.

  A method for mixing and spraying the coating material in the nitrogen plasma gas is not particularly limited, and a known means is used. For example, a mixed gas of a coating material evaporated and atomized at a high temperature and nitrogen made of a carrier gas may be introduced into a nitrogen plasma gas that is plasmatized at atmospheric pressure.

  The coating material thus introduced into the nitrogen plasma gas undergoes a reaction that instantaneously generates radicals when it comes into contact with the nitrogen plasma gas, and the radicals generated while maintaining the basic skeleton are plasma-polymerized, It reacts with the metal present on the surface of the metal material, and a coating film made of polysiloxane is instantaneously formed.

(Nozzle distance, nozzle moving speed)
In the present invention, as described above, the thickness of the coating film is regulated within the range of 4 nm to 14 nm, but the thickness of the peritoneum is appropriately adjusted according to the condition setting of the plasma processing apparatus to be used. For example, when an atmospheric pressure plasma polymerization processing apparatus (Plasma Polymer Lab System PAD-1 type) manufactured by Plasmatreat is used as the plasma processing apparatus, the nozzle distance is 5 mm to 30 mm, preferably 7 mm to 25 mm. The moving speed is set to 10 m / min to 40 m / min, preferably 7 m / min to 35 m / min. When the nozzle distance is less than 5 mm or when the nozzle moving speed is less than 10 m / min, the film thickness of the coating film exceeds 14 nm. Further, when the nozzle distance exceeds 30 mm or the nozzle moving speed exceeds 40 m / min, the film thickness of the coating film is less than 4 nm. Here, the nozzle distance refers to the distance from the tip of a supply nozzle that ejects an organosilicon compound having a siloxane bond, which is a coating material, to the surface of the metal material on which the coating film is formed. The nozzle movement speed refers to the speed at which the supply nozzle moves relative to the metal material.

  Hereinafter, the present invention will be described in more detail with reference to examples. The silver plated copper substrates of Examples 1 to 25 and Comparative Examples 1 to 9 (hereinafter referred to as “samples”) were evaluated by the following evaluation methods (a) to (c).

(A) Sulfide resistance Sulfide resistance was evaluated by observing the appearance of the samples of Examples 1 to 21 and Comparative Examples 1 to 9 with the naked eye at the following stages.

  First, the appearance of each sample in the initial state was observed with the naked eye. Next, each sample was heat-treated at a temperature of 175 ° C. for 1.5 hours, and then subjected to a sulfurization test in which it was left in an ammonium sulfate vapor for 30 minutes. Observed. Further, each sample was subjected to a heat treatment for 1.5 hours at a temperature of 175 ° C. using a hot-air circulating dryer, and the change in appearance before and after the heat treatment was observed with the naked eye. Finally, the sulfidation test was performed again, and changes in appearance before and after the sulfidation test were observed with the naked eye.

  The resistance to sulfidation is “excellent (◎)” when the sample surface is not discolored, “good (○)” when it is discolored to pale yellow, and “possible” when it is discolored to light blue. (Δ) ”and those that changed to dark blue-black were evaluated as“ impossible (×) ”.

(B) Wire-bonding characteristics Wire-bonding characteristics are obtained by using a wire bonder (made by Shinkawa Co., Ltd., UTC-1000) as a wire wire for the samples of Examples 1 to 21 and Comparative Examples 1 to 9. After bonding (2nd bonding part), this gold wire wire is clamped by a bond tester (Dage 5000, manufactured by Dage Co., Ltd.) and pulled by 90 °, and the appearance of the cutting position of the 2nd bonding part of the wire at this time is observed. evaluated. Here, the 2nd bonding portion of the wire means, for example, a bonding position on a substrate (such as a lead frame) on which the capillary moves and bonds after the first bonding (ball bonding) to the LED chip.

  The wire bonding characteristics were evaluated as “good (◯)” when the bonding was strong and the wire itself was cut, and “impossible (×)” when peeled at the bonding surface of the wire and the sample.

(C) Lightness (brightness)
As for the lightness, the lightness L value in the initial state of the samples of Examples 1 to 21 and Comparative Examples 1 to 9, and the lightness L value after heat-treating each sample at 175 ° C. for 1.5 hours, It was measured by a spectral colorimeter for use (manufactured by Murakami Color Research Laboratory, Color-guide) and evaluated by comparing these measured values.

(Examples 1-21, Comparative Examples 1-7)
In Examples 1 to 21 and Comparative Examples 1 to 7, a substrate obtained by subjecting a pure copper substrate to silver plating (lightness L value: 70) having a thickness of 4 μm by electrolytic plating was subjected to atmospheric pressure plasma polymerization treatment. A sample obtained by forming a coating film was used. More specifically, with respect to the base material, hexamethyldisiloxane (HMDSO) is used as a coating film material, nitrogen is used as a carrier gas and a plasma gas, Manufactured by Plasma Polymer Lab System PAD-1 type), a sample obtained by forming a coating film was used. The conditions of the atmospheric pressure plasma polymerization treatment at this time were as shown below.

(Conditions for atmospheric pressure plasma polymerization)
Transmission frequency of plasma generator: 21 kHz
Generator output voltage: 280V
Pressure: Atmospheric pressure (101.25 hPa)
Introduced amount of hexamethyldisiloxane: 20 g / h
Carrier gas and plasma gas: Nitrogen (Nitrogen content: 100%)

  Moreover, in Examples 1-21 and Comparative Examples 1-7, the nozzle distance and the nozzle moving speed when forming the coating film were as shown in Table 1.

For the coating films formed on the surfaces of the samples of Examples 1 to 21 and Comparative Examples 1 to 7, analysis was performed using an infrared spectroscopic analyzer (manufactured by Perkin Elmer Japan, Frontier). All of these coating films were confirmed to be composed of dimethylpolysiloxane represented by the structural formula: (CH ₃ ) ₃ SiO — [(CH ₃ ) ₂ SiO] _n —Si (CH ₃ ) _3. It was done.

(Comparative Examples 8 and 9)
In Comparative Example 8, a sample obtained by subjecting a pure copper substrate to only silver plating having a thickness of 4 μm by an electrolytic plating method, that is, a sample in which no coating film was formed on the silver plating was used as a sample.

  In Comparative Example 9, the pure copper substrate was obtained by subjecting a pure copper substrate to silver plating having a thickness of 4 μm by the electrolytic plating method, and then performing the same treatment as that described in JP 2011-202239 A. A sample was used. Specifically, phosphoric acid is added as a pH adjuster to a treatment solution having the following composition to adjust the pH to 5.5, and the substrate is immersed for about 1 minute at a temperature of 25 ° C. A sample obtained by washing with water, drying at 100 ° C. for 1 minute and evaporating water was used.

(Composition of treatment liquid)
Inhibitor (triazine-2,4,6-trithiol): 0.1 g / L
Potassium iodide: 0.1 g / L
Surfactant (oleyl alcohol ethoxylate): 0.1 g / L
Dissolution aid (butyl propylene glycol): 10 g / L
pH buffer (sodium hydrogen phosphate): 10 g / L

  As a result of analyzing the coating film formed on the surface of the sample of Comparative Example 9 using an infrared spectroscopic analyzer, this coating film was a multilayer of triazine-2,4,6-trithiol. It was confirmed that the film was composed of a film.

(Examples 22 and 23)
In Example 22, a sample obtained in the same manner as in Example 1 was used except that decamethyltetrasiloxane (DMTSO) was used as a material for the coating film. In Example 23, a sample obtained in the same manner as in Example 1 was used except that octamethylcyclotetrasiloxane (OMCTSO) was used as the material for the coating film.

As a result of analyzing the coating films formed on the surfaces of these samples with an infrared spectroscopic analyzer, these coating films are all represented by the structural formula: (CH ₃ ) ₃ SiO — [(CH _{3) 2} SiO] that is constituted by a dimethylpolysiloxane represented by _n -Si (CH _{3) 3} was confirmed. Moreover, as a result of evaluating said (a)-(c) with respect to these samples, it was confirmed that it has a characteristic equivalent to Examples 1-21.

(Example 24)
A sample obtained in the same manner as in Example 1 was used except that a part of the side chain of hexamethyldisiloxane (HMDSO) was substituted with a carboxyl group as a material for the coating film.

As a result of analyzing the coating film formed on the surface of this sample by an infrared spectroscopic analyzer, this coating film has a structural formula: (CH ₃ ) ₃ SiO — [(CH ₃ ) ₂ SiO]. _m - be _{[(C 6 H 5) 2} SiO] is composed of methylphenyl polysiloxane represented by _n -Si (CH _{3) 3} was confirmed. Moreover, as a result of evaluating said (a)-(c) with respect to this sample, it was confirmed that it has a characteristic equivalent to Examples 1-21.

(Example 25)
A sample obtained in the same manner as in Example 1 was used, except that a part of the side chain of hexamethyldisiloxane (HMDSO) substituted with a carboxyl group was used as a material for the coating film.

As a result of analyzing the coating film formed on the surface of this sample by an infrared spectroscopic analyzer, this coating film has a structural formula: (CH ₃ ) ₃ SiO — [(CH ₃ ) ₂ SiO]. _{m - [(COOH) 2 SiO} ] that is constituted by a carboxyl-modified dimethylpolysiloxane represented by _n -Si (CH _{3) 3} was confirmed. Moreover, as a result of evaluating said (a)-(c) with respect to this sample, it was confirmed that it has a characteristic equivalent to Examples 1-21.

(Evaluation)
From Examples 1 to 21, when the coating film (polysiloxane film) of the present invention was formed, no coloration was observed in the film thickness range of 4 nm to 14 nm, and both sulfidation resistance and bonding properties were good. It turns out that it is. Furthermore, when the coating film of the present invention is formed, the lightness L value can be improved as compared with the case of only the metal film (silver plating), and the lightness L value is high even after the heat treatment. It is understood that the value can be maintained.

  Further, from Examples 22 and 23, even when an organosilicon compound other than dimethylpolysiloxane is used as the coating material, a coating film made of dimethylpolysiloxane can be formed as in Examples 1-21. Is understood.

  Furthermore, from Examples 24 and 25, even when a part of the side chain of dimethylpolysiloxane is substituted with a phenyl group or an organic group, a coating film equivalent to Examples 1 to 21 can be formed. Is understood.

  On the other hand, Comparative Examples 1-7 are examples in which the film thickness of the coating layer is not within the scope of the present invention. Comparative Examples 1-4 are examples in which the film thickness of the coating film exceeds 14 nm. In Comparative Examples 1 to 4, it can be evaluated that the resistance to sulfuration is good and the lightness L value is improved, but the wire bonding characteristics are inferior. Comparative Examples 5 to 7 are examples in which the thickness of the coating film is less than 2 nm. In Comparative Examples 5 to 7, the wire bonding characteristics are sufficient, but the sulfide resistance is inferior. Moreover, although the comparative example 8 is an example which does not form a coating film, compared with another Example and comparative example, it is a thing inferior to sulfidation resistance and the brightness L value remarkably. Comparative Example 9 is an example in which a coating film is formed by a conventional technique. Similar to Comparative Examples 1 to 4, Comparative Example 9 has good sulfidation resistance, but is inferior in wire bonding characteristics and brightness L value.

Claims (12)

  A coating film formed on a surface of a metal material, wherein an organosilicon compound having a siloxane bond is mixed and sprayed with a carrier gas containing at least nitrogen in a nitrogen plasma gas at atmospheric pressure, and the organosilicon compound A coating film comprising a polysiloxane film having a thickness of 4 nm to 14 nm, which is formed by radicalizing and polymerizing. The coating film according to claim 1, wherein the polysiloxane film is made of polysiloxane whose main chain is — (Si—O—Si) _n —.   The coating film according to claim 2, wherein the polysiloxane is dimethylpolysiloxane.   A lead frame; a reflection portion obtained by processing a pedestal of the lead frame; and an LED chip placed at a position surrounded by the reflection portion, wherein the reflection portion includes a metal film and the metal film. A light-emitting diode device comprising: the coating film according to claim 1 formed on a surface of the light-emitting diode.   The light emitting diode device according to claim 4, wherein the metal film is a silver film or a silver alloy film.   The light emitting diode device according to claim 5, wherein a lightness L value of the reflecting portion is 80 or more.   Under atmospheric pressure, an organosilicon compound having a siloxane bond is mixed and sprayed with nitrogen gas in a nitrogen plasma gas, and the organosilicon compound is polymerized by radicalization. A method for forming a coating film, comprising forming a thickness of 4 nm to 14 nm on the surface of the film.   The organosilicon compound is at least one selected from hexamethyldisiloxane (HMDSO), octamethyltrisiloxane (OMTSO), decamethyltetrasiloxane (DMTSO), and octamethylcyclotetrasiloxane (OMCTSO). The method for forming a coating film according to claim 7.   The coating film is formed using an atmospheric pressure plasma polymerization processing apparatus, the distance from the supply nozzle of the apparatus to the surface of the metal material is set to 5 mm to 30 mm, and the moving speed of the supply nozzle is set to 10 m / min to 40 m. The method for forming a coating film according to claim 7, which is performed as / min. The method for forming a coating film according to claim 7, wherein the polysiloxane film is made of polysiloxane whose main chain is — (Si—O—Si) _n —.   The method for forming a coating film according to claim 10, wherein the polysiloxane is dimethylpolysiloxane. The method for forming a coating film according to claim 7, wherein the metal material is silver or a silver alloy.