JP2005194392A - Coating material, and method and apparatus for coating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-solvent type coating material having excellent drip-proof and moisture-proof properties, providing good operability and usable even for an in-car electronic circuit boards at a low cost; and to provide a method and an apparatus for coating the coating material. <P>SOLUTION: The coating material is used for the electronic circuit board, and comprises a polyolefin rein as a base material and 10-35 wt.% softening material. As a result, a proper viscosity at hot melt processing is possessed when coated on the electronic circuit board to provide good operability and to provide the low-cost coating material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coating material for an electronic circuit board, a coating method thereof, and a coating apparatus.

  Generally, a coating material using a solvent is used as a drip-proof / moisture-proof coating material for an electronic circuit board.

For example, Japanese Patent Application Laid-Open No. 6-154691 (Patent Document 1) discloses a coating material such as an acrylic resin, polyurethane, and epoxy synthetic resin dissolved in a volatile solvent. Since the coating material using such a solvent can be adjusted to an arbitrary viscosity by melting the coating material with the solvent, the coating material can be applied to the electronic circuit board relatively easily.
JP-A-6-154691

  However, in recent years, with the increase of environmental regulations against air pollution of solvents, the use of coating materials using solvents has been banned, and the development of alternative technologies has become indispensable.

  As a solventless type (hot melt type) coating material that does not use a solvent, a silicone resin is conventionally known. The silicone resin as the coating material includes a room temperature curing type and a thermosetting type. However, the room temperature curable silicone resin has a problem that the curing time is long and it is difficult to apply it thinly, resulting in a high material cost. In addition, the use site is limited, for example, siloxane gas generated in the use environment causes contact failure. On the other hand, although the thermosetting silicone resin has a relatively short curing time, there is a problem that flux cleaning is required after reflow soldering, and material costs and processing costs are relatively high. In addition, an example in which a thermoplastic polyamide resin is used as a coating material for an electronic circuit board is known. However, the hygroscopicity is high, and a coating thickness of several mm is necessary to ensure moisture resistance, and the material cost is high. There is a problem that becomes. In particular, coating materials used for in-vehicle electronic circuit boards must be able to withstand severe vehicle environments (−40 ° C. to 125 ° C.), and low-cost solventless coating materials that can withstand this are still unknown. It is not done.

  Patent Document 1 discloses a method for applying a solventless coating material using a curtain coating method called a slit die. However, it is difficult to apply a solventless coating material thinly and uniformly on an electronic circuit board simply by using the curtain coating method.

  Therefore, the present invention is a solvent-free coating material, which is excellent in drip-proof and moisture-proof properties, low in cost and good in workability, and can be used for an on-vehicle electronic circuit board, and its application method and The object is to provide a coating apparatus.

  The inventions according to claims 1 to 8 are inventions relating to a solventless type (hot melt type) coating material.

  The invention described in claim 1 is a coating material for an electronic circuit board, characterized by comprising a polyolefin resin as a base material and containing 10 to 35 wt% of a softening material.

  According to this, it is a solventless coating material based on a polyolefin resin, and contains 10 to 35 wt% softening material, so that it has an appropriate viscosity during hot melt when applied to an electronic circuit board. To have. Therefore, workability is good and a low-cost coating material can be obtained.

  The invention according to claim 2 is characterized in that the polyolefin resin comprises a propylene-ethylene copolymer. The invention described in claim 3 is characterized in that the propylene-ethylene copolymer is a copolymer of 50 to 95 wt% of propylene and 50 to 5 wt% of ethylene.

  According to this, it can be set as the coating material which is excellent in the insulation in high temperature, high humidity, heat resistance, the crack resistance in a thermal cycle, and adhesiveness. Moreover, it can be set as the coating material with sufficient intensity | strength also with respect to the mechanical stress which acts on a soldering part.

  The invention according to claim 4 is characterized in that the polyolefin resin is amorphous or low crystalline.

  According to this, preparation and mixing of a coating material become easy, and low-cost and stable application can be realized.

  As described in claim 5, the softening material is preferably liquid paraffin, paraffin wax, ethylene wax, alicyclic saturated hydrocarbon resin, or a combination thereof.

  The softening material can be uniformly mixed when the polyolefin resin is melted, and does not cause deterioration of the insulating properties of the polyolefin resin after solidification. Therefore, it becomes easy to apply a coating material based on a polyolefin resin, and good insulation characteristics of the polyolefin resin can be maintained even after the application.

  As described in claim 6, it is preferable that the coating material contains 3 wt% or less of a deterioration preventing agent. For example, as described in claim 7, the deterioration preventing material may be 2 wt% or less antioxidant and 1 wt% or less chelating agent (metal deactivator).

  Thereby, the oxidation deterioration of the coating material which uses a polyolefin resin as a base material, and the reaction deterioration by contact with a metal (especially copper) can be suppressed.

  As described in claim 8, the solventless coating material based on the polyolefin resin is suitable for use in an on-vehicle electronic circuit board.

  Coating materials used for automotive electronic circuit boards are insulation and heat resistance in high temperature and high humidity, crack resistance in thermal cycle, adhesion, and sufficient strength against mechanical stress acting on soldered parts. Characteristics that can withstand harsh vehicle environments such as The solvent-free coating material based on the above-mentioned polyolefin resin is a low-cost coating material having characteristics capable of withstanding a severe vehicle environment, and is suitably used for an on-vehicle electronic circuit board.

  The invention described in claims 9 to 11 is an invention relating to a method for applying a solventless coating material.

  The invention according to claim 9 is a coating material applying method for applying a coating material to an electronic circuit board, the heating process for heating the electronic circuit board, and the spraying process for spraying the coating material to the electronic circuit board. It is characterized by having.

  According to this, since the coating material can be sprayed onto the sufficiently heated electronic circuit board, even a solventless coating material that is difficult to apply can be applied thinly.

  The invention according to claim 10 is characterized in that, in the spraying step, the coating material is heated and melted and sprayed onto the electronic circuit board.

  As a result, even a solventless coating material can be melted by heating, adjusted to a predetermined viscosity, and sprayed thinly onto the electronic circuit board.

  Therefore, as described in claim 11, the above-described coating method is a coating method suitable for coating a coating material containing a polyolefin resin as a base material and containing 10 to 35 wt% softening material.

  The inventions according to claims 12 to 15 are inventions relating to the solvent-free coating material and the coating apparatus used in the coating method.

  The invention according to claim 12 is a coating material application device for applying a coating material to an electronic circuit board, wherein the heating means for heating the electronic circuit board, and the spraying for spraying the coating material. Means.

  According to this, the application method described above can be performed by the application apparatus, and even a solventless coating material that is difficult to apply can be applied thinly and uniformly.

  The invention according to claim 13 is characterized in that the spray means has a nozzle head for spraying the coating material onto the electronic circuit board, and the nozzle head is provided with a line-shaped slit, Comb-like spacers are inserted with the tips of the comb teeth facing the electronic circuit board.

  According to this, it is possible to easily control the uniformity and the spraying amount for spraying the molten coating material onto the electronic circuit board.

  In the invention described in claim 14, when the width of the comb teeth in the spacer is w and the pitch of the comb teeth is p, the aperture ratio a = (p−w) / p is 0.53 or more, 0.0. It is characterized by being 87 or less.

  According to this, the molten coating material can be sprayed thinly and uniformly on the electronic circuit board.

  Therefore, as described in claim 15, the coating device is a coating device suitable for coating a coating material comprising a polyolefin resin as a base material and containing 10 to 35 wt% of a softening material.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The present invention relates to a solvent-free (hot-melt type) coating material used for drip-proofing and moisture-proofing an electronic circuit board, and a coating method and coating apparatus therefor.

  Conventionally, a coating material using a solvent has been generally used as a drip-proof / moisture-proof coating material for an electronic circuit board. However, in recent years, with the increase in environmental regulations against air pollution of solvents, coating materials using solvents are becoming prohibited. The present invention was invented as an alternative technique for a conventional coating material using a solvent, thereby clearing environmental regulations and preventing air pollution by the solvent.

  In particular, the present invention assumes a coating material used for an on-vehicle electronic circuit board. Coating materials used for automotive electronic circuit boards act on insulation, heat resistance in high temperature and high humidity, resistance to cracking in thermal cycles, condensation resistance, adhesion to electronic components and boards, and soldering parts A characteristic that can withstand a severe vehicle environment (−40 ° C. to 125 ° C.) such as having sufficient strength against mechanical stress is required.

  The coating material of the present invention is a coating material comprising a polyolefin resin as a base material and containing 10 to 35 wt% of a softening material. This coating material is a solvent-free type coating material that can be hot-melted, and has an appropriate viscosity at the time of hot-melting when applied to an electronic circuit board by containing 10 to 35 wt% softening material. It becomes like this. Therefore, this coating material has good workability with respect to application, and can be applied to an electronic circuit board at a low cost.

  The polyolefin resin is preferably made of a propylene-ethylene copolymer. As a base material of the solventless coating material, for example, when a coating material used for an on-vehicle electronic circuit board is assumed, heat resistance of about 130 ° C. is required. On the other hand, a material having a viscosity as low as possible is suitable for the coating property of the coating material during hot melting. For this reason, a resin material whose viscosity rapidly increases at 130 ° C. is desirable as a solvent-free coating material for vehicle use. For this purpose, a resin having a softening point in the range of 150 to 130 ° C. is suitable. . On the other hand, when a coating material for in-vehicle use is assumed, considering the crack resistance in the thermal cycle, the glass transition point needs to be at least in the range of −29 to −40 ° C. in order not to be a rigid body at low temperatures. . A polyolefin resin composed of a propylene-ethylene copolymer can satisfy both the softening point and the glass transition temperature range by appropriately adjusting the ratio of propylene and ethylene.

  Commercially available materials for propylene-ethylene copolymers include, for example, RT2535 (HUNTSMAN) as a high ethylene material with a large proportion of ethylene relative to propylene, and RT2304 (H2TS as a medium ethylene material with a moderate proportion of ethylene relative to propylene. HUNTSMAN). By appropriately mixing these materials, a copolymer having a desired propylene: ethylene ratio can be obtained. The propylene-ethylene copolymer is preferably a copolymer of 50 to 95 wt% propylene and 50 to 5 wt% ethylene. A coating material based on such a propylene-ethylene copolymer is excellent in insulation at high temperature and high humidity, heat resistance, crack resistance in a cold cycle, and adhesion. In addition, it has sufficient strength against mechanical stress acting on the soldered portion. The blending ratio of ethylene to propylene does not significantly affect the viscosity of the hot melt material described later.

  The polyolefin resin is preferably amorphous or low crystalline. Amorphous or low crystalline polyolefin resin is generally called APAO (Amorphous Poly Alpha Olefin). By using this APAO as the base material of the coating material, blending and mixing are facilitated, and low-cost and stable application can be realized.

  The softening agent added to the above polyolefin resin is a glidant that reduces the viscosity of the coating material and gives it a practical coating property. It is liquid paraffin, paraffin wax, ethylene wax, alicyclic saturated. It is preferably any one of hydrocarbon resins or a combination thereof. The softening agent only needs to have a sufficiently low viscosity in the vicinity of the substrate heating temperature at the time of applying the coating material, and is preferably a solid at room temperature in consideration of stickiness. Therefore, if you want to lower the viscosity of the polyolefin resin, add a lot of liquid paraffin (pour point: 0 ° C or less), and if you want to suppress stickiness, mix it with paraffin wax (softening point: 70-40 ° C). It will be. Depending on the application, a tackifier (alicyclic saturated hydrocarbon resin) may be mixed (softening point: 115 to 60 ° C.) in order to enhance the adhesiveness. In addition, the upper limit of the content of the softening agent is limited by heat resistance, and if heat resistance at 130 ° C. is required, it needs to be 35% or less. A commercially available material for liquid paraffin is, for example, Moresco White P-500 (Matsumura Oil Research Institute). Moreover, as a commercially available material of paraffin wax, there is, for example, paraffin Wax-155 (Nippon Seiki). Moreover, as a commercial material of alicyclic saturated hydrocarbon resin, there exists Alcon P-100 (Arakawa Chemical Industries), for example. These softening materials can be mixed uniformly when the polyolefin resin is melted, and do not deteriorate the insulation characteristics of the polyolefin resin after solidification. For this reason, the coating of the polyolefin resin as a base material can be easily applied, and good insulating properties of the polyolefin resin can be maintained even after the application.

  On the other hand, when applying a solvent-free coating material to an electronic circuit board, the electronic circuit board on which the electronic components are mounted has surface irregularities due to the arrangement of the electronic components, gaps between the electronic components, electrodes under the lead components, etc. is there. For this reason, it is necessary for the coating material to sufficiently wrap around these parts and cover these parts. Therefore, in applying the solventless coating material, the temperature characteristic of the melt viscosity of the coating material melt (hot melt material) is important.

  FIGS. 1-3 are the results of examining the temperature characteristics of the melt viscosity by changing the blending ratio of the polyolefin resin composed of the propylene-ethylene copolymer and the softening material. FIG. 1 is a diagram showing a blending ratio of samples subjected to the test, and FIG. 2 is a graph showing measured viscosities. FIG. 3 is a table showing the evaluation results regarding the measured viscosity and coating property at each temperature.

  Viscosity measurement conditions are as follows. Viscosity measuring device: rheometer (manufactured by Brookfield) Model: DV-III + thermocell, spindle: SC4-21.

  When samples A to N subjected to each test were examined for coatability using a coating apparatus described later, the viscosity at 190 ° C. was 1700 mPa · s or less, the viscosity at 170 ° C. was 2100 mPa · s or less, and 150 ° C. If the material has a viscosity of 4000 mPa · s or less, by appropriately selecting the application conditions (opening ratio of comb-like spacers in the nozzle, hot air pressure, substrate heating temperature, nozzle head speed, etc.) It was found that the film sufficiently flows into the gaps and the like, and good coating properties can be obtained. On the other hand, a material having a viscosity at 130 ° C. of 18000 mPa · s or more is required in order to ensure the dripping and heat resistance of the coating material after application. In FIG. 2, the conditions for the coating property are indicated by hatched lines. Samples B to H and Samples J to N satisfy the conditions for the coating property. FIG. 3 shows the evaluation results regarding the coating property in the bottom column.

  From the above results, the addition range of the softening material to the polyolefin resin is suitably 10 to 35 wt%.

  In addition, when applying the said coating material to the vehicle-mounted electronic circuit board and using it, it is preferable to add deterioration inhibitors, such as antioxidant and a chelating agent (metal deactivator). As a result, deterioration due to high-temperature oxidation of the electronic circuit formed on the electronic circuit board and contact with the metal (especially copper) of the circuit wiring can be suppressed, and severe conditions in the vehicle environment can be dealt with. Since the minimum necessary deterioration inhibitor is sufficient, the coating material preferably contains 3 wt% or less deterioration inhibitor. For example, the deterioration preventing material is a coating material containing 2 wt% or less antioxidant and 1 wt% or less chelating agent (metal deactivator). Thereby, the oxidation deterioration of the coating material which uses a polyolefin resin as a base material, and the reaction deterioration by contact with a metal (especially copper) can be suppressed. Commercially available materials for deterioration inhibitors include, for example, IRGANOX 1010 (Ciba) as a primary antioxidant, IRGAFOS 168 (Ciba) as a secondary antioxidant, and MD1024 (Ciba) as a chelating agent.

  Among the coating materials shown above, an example of a particularly suitable combination as a coating material used for an on-vehicle electronic circuit board is propylene-ethylene copolymer 68 to 73 wt% (high ethylene material 43 to 53 wt%, medium ethylene Material 25-35 wt%), softening material 15-25 wt% (liquid paraffin 14 wt%, alicyclic saturated hydrocarbon resin-5 wt% and liquid paraffin 20 wt%, paraffin wax 0-5 wt%), deterioration inhibitor (primary oxidation prevention) Agent 1.5 wt%, secondary antioxidant 0.2 wt%, chelating material 0.7 wt%). The solvent-free coating material based on this propylene-ethylene copolymer polyolefin resin is a low-cost coating material that can withstand harsh vehicle environments, and is an electronic circuit for vehicles. It is suitably used for a substrate.

  Next, the coating material coating apparatus and coating method will be described with reference to the drawings.

  FIG. 4A is a diagram schematically showing a coating apparatus 100 suitable for coating the solventless coating material.

  A coating apparatus 100 shown in FIG. 4A is a coating apparatus for coating the electronic circuit board 1 with a hot melt material 2 that is a melt of the coating material, and heating means for heating the electronic circuit board 1. 3 and a spraying means 5 for spraying the hot melt material 2 onto the electronic circuit board 1. In addition, in the coating apparatus 100 of FIG. 4A, the code | symbol 6 is an application | coating stage and the code | symbol 7 is an application | coating mask.

  The heating means 3 is a heating furnace in which the electronic circuit board 1 is heated in advance before the hot melt material 2 is applied to the electronic circuit board 1, and includes a heater 3h and a conveyor 3c. The heating means 3 is for suppressing cooling of the hot melt material 2 deposited on the electronic circuit board 1. The heating means 3 may be a batch type instead of the conveyor type as shown in FIG. The electronic circuit board 1 is heated to 100 to 120 ° C. in consideration of the heat resistance of the electronic component to be mounted when the coating material based on the above APAO is used. The heater 3h is preferably a heating mechanism using an infrared heater that has good absorbability with respect to a glass epoxy substrate generally used as the electronic circuit board 1.

  The electronic circuit board 1 conveyed by the conveyor 3c through the heating means 3 is set on the application stage 6 by a robot or the like, and the hot melt material 2 is applied to both surfaces of the electronic circuit board 1 by the spraying means 5. When there is a coating prohibited area on the electronic circuit board 1, selective coating is possible by using the coating mask 7. The plan view of FIG. 4B is a diagram illustrating an example of the coating mask 7.

  The spraying means 5 of FIG. 4A has a nozzle head 5n for spraying the hot melt material 2 onto the electronic circuit board 1. In the coating apparatus 100, either the nozzle head 5 n or the coating stage 6 is scanned in the left-right direction on the paper surface, and the hot melt material 2 is sprayed and applied to the electronic circuit board 1. It is also possible to apply a program by a robot using a nozzle head 5n having a small nozzle width in a direction perpendicular to the paper surface (practically about 15 to 30 mm).

  Reference numeral 5 a in the spraying means 5 is a cartridge containing the hot melt material 2. The hot melt material 2 may be supplied to the nozzle head 5n by an applicator 5b having a heating hose 5c, as shown at the right end of FIG. The cartridge 5a or the applicator 5b includes a heating mechanism for holding the hot melt material 2 that is a melt of the coating material in a molten state, but the illustration is omitted for simplification. The temperature of the hot melt material 2 of the cartridge 5a or the applicator 5b is, for example, 180 ° C. to 200 ° C. in the case of a coating material based on a polyolefin resin.

  The nozzle head 5n in the spraying means 5 is provided with a line-shaped slit 5s in a direction perpendicular to the paper surface of FIG. In addition, a comb-like spacer 5k is inserted into the slit 5s so that the tip of the comb tooth faces the electronic circuit board 1. By the comb-like spacers 5k, the hot melt material 2 passing through the slits 5s is uniformly dispersed in a direction perpendicular to the paper surface. In addition, by appropriately setting the aperture ratio described later, it is possible to easily control the amount of spraying of the hot melt material 2 to the electronic circuit board 1. On the other hand, a hot air outlet 5f is arranged near the line-shaped slit 5s at the tip of the nozzle head 5n. The hot melt material 2 that has reached the tip of the nozzle head 5n through the slit 5s is stretched into a fiber shape and blown off by the pressure of the high-pressure hot air that is blown out from the blowout port 5f, as shown in FIG. The electronic circuit board 1 is sprayed onto the electronic circuit board 1 in the form of curtain fibers in a direction perpendicular to the paper surface.

  FIG. 4C is a plan view of the comb-like spacer 5k. The comb-shaped spacer 5k has an aperture ratio a = (p−w) / p of 0.53 or more, 0.87, where the width of the comb teeth shown in the figure is w and the pitch of the comb teeth is p. The following are used.

  The size of the comb-like spacer 5k greatly affects the applicability of the hot melt material 2. As comb-like spacers for curtain spray used for conventional adhesive application, etc., p = 1.25 mm, w = 0.9 mm, a = 0.28, p = 1 mm, w = 0.5 mm, a = There is an example of 0.5 coater (sun tool). However, when the spacers having these aperture ratios were tested, it was difficult to form a coating film that was not missing.

  The portion of the comb tooth width w in FIG. 4C is a guide for uniformly dispersing the hot melt material 2 in the direction perpendicular to the paper surface. As for the coating property of the coating film, it was confirmed by a test that the width w of the comb teeth is smaller and the pitch p of the comb teeth is larger. However, the minimum width w that can be practically processed is 0.25 to 0.3 mm in the case of a spacer having a thickness of about 0.3 mm. If the pitch p of the comb teeth is too large, the uniformity of dispersion in the direction perpendicular to the paper surface is deteriorated, and the discharged hot melt material 2 is easy to entrain air, so that bubbles are formed in the coating film. Many are taken in. For this reason, the practical maximum pitch p is 2 mm or less. Therefore, the aperture ratio a of the comb-like spacer 5k in the coating apparatus 100 is 0.53 (w = 0.3 mm, p = 0.65 mm) or more and 0.87 (w = 0.25 mm, p) as described above. = 2 mm) or less, the hot melt material 2 can be sprayed thinly and uniformly on the electronic circuit board 1.

  Next, typical application conditions are shown below.

  Heating temperature of the electronic circuit board 1: 100 to 120 ° C, melting temperature of the hot melt material 2: 195 ° C, pressurization of the hot melt material 2: 0.4 MPa, hot air temperature: 215 ° C, hot air pressure: 0.3 MPa or more, The temperature of the nozzle head 5n: 205 ° C., the coating height of the nozzle head 5n: 30 mm from the upper surface of the electronic circuit board 1, and the moving speed of the nozzle head 5n: 8 m / min.

  In each of the above conditions, the hot air pressure greatly affects the applicability. When the hot air pressure is 0.1 to 0.2 MPa, the wrapping under the electronic component is insufficient, and the hot air pressure is set to 0.3 MPa or more to increase the scattering energy of the hot melt material 2. Improved.

  In a conventional method for applying a coating material to an electronic circuit board, there is no heating process of the electronic circuit board 1 by the heating means 3. Since the hot melt fiber is fine, its heat capacity is small, and if the electronic circuit board 1 is not heated, it is cooled rapidly immediately after being attached to the electronic circuit board 1. For this reason, in the conventional coating method, only a coating film with irregularities and many holes can be obtained. On the other hand, in the coating method of the present invention using the coating apparatus 100 of FIG. 4A, the electronic circuit board 1 to which the hot melt material 2 is sprayed is sufficiently heated in the overheating process by the heating means 3. For this reason, the hot melt material 2 sprayed in the form of curtain fibers flows moderately, spreads thinly and evenly on the surface of the electronic circuit board 1, and becomes a coating film with no unpainted areas.

  As described above, the hot melt material 2, which is a melt of the coating material, is applied to the electronic circuit board 1 by the coating apparatus 100 shown in FIG. It can be applied thinly and uniformly. Therefore, the coating apparatus 100 of FIG. 4A and the coating method using the same are a coating comprising a polyolefin resin having a predetermined viscosity when heated and melted as a base material and containing 15 to 35 wt% softening material. A coating apparatus and a coating method suitable for coating a material.

In the test which investigates the temperature characteristic of melt viscosity, it is a figure which shows the mixture ratio of the polyolefin resin and softening material of the sample used for the test. It is the result of having investigated the temperature characteristic of melt viscosity about the sample of FIG. It is the result of having investigated the temperature characteristic of the melt viscosity about the sample of FIG. 1, and was the figure which showed the evaluation result regarding the measured viscosity and coating property in each temperature as a table | surface. (A) is a figure which shows typically the coating device suitable for application | coating of a solventless type coating material. (B) is a figure which shows an example of an application mask. (C) is a top view of a comb-tooth shaped spacer.

Explanation of symbols

1 Electronic circuit board 2 Hot melt material (coating material)
DESCRIPTION OF SYMBOLS 3 Heating means 3c Conveyor 3h Heater 5 Spraying means 5k Spacer 5n Nozzle head 5s Slit 6 Coating stage 7 Coating mask 100 Coating device

Claims (15)

Electronic circuit board coating material,
A coating material comprising a polyolefin resin as a base material and containing 10 to 35 wt% of a softening material.   The coating material according to claim 1, wherein the polyolefin resin is made of a propylene-ethylene copolymer.   The coating material according to claim 2, wherein the propylene-ethylene copolymer is a copolymer of 50 to 95 wt% of propylene and 50 to 5 wt% of ethylene.   The coating material according to any one of claims 1 to 3, wherein the polyolefin resin is amorphous or low crystalline.   The coating according to any one of claims 1 to 4, wherein the softening material is liquid paraffin, paraffin wax, ethylene wax, alicyclic saturated hydrocarbon resin, or a combination thereof. Wood.   The coating material according to any one of claims 1 to 5, wherein the coating material contains a deterioration preventing agent of 3 wt% or less.   The coating material according to claim 6, wherein the deterioration preventing material comprises an antioxidant of 2 wt% or less and a chelating agent (metal deactivator) of 1 wt% or less.   The coating material according to claim 1, wherein the electronic circuit board is a vehicle-mounted electronic circuit board. A coating material application method for applying a coating material to an electronic circuit board,
A heating step of heating the electronic circuit board;
And a spraying step of spraying the coating material onto the electronic circuit board.   The coating method according to claim 9, wherein in the spraying step, the coating material is heated and melted and sprayed onto the electronic circuit board.   11. The coating material application method according to claim 9, wherein the coating material comprises a polyolefin resin as a base material and contains 10 to 35 wt% of a softening material. A coating material application device for applying a coating material to an electronic circuit board,
Heating means for heating the electronic circuit board;
An apparatus for applying a coating material, comprising: spraying means for spraying the coating material. The spraying means has a nozzle head for spraying the coating material onto the electronic circuit board;
The nozzle head is provided with a line-shaped slit,
13. The coating material coating apparatus according to claim 12, wherein a comb-like spacer is inserted into the slit so that the tip of the comb tooth faces the electronic circuit board.   When the width of the comb teeth in the spacer is w and the pitch of the comb teeth is p, the aperture ratio a = (p−w) / p is 0.53 or more and 0.87 or less. The coating material coating apparatus according to claim 13.   The coating material coating apparatus according to any one of claims 12 to 14, wherein the coating material comprises a polyolefin resin as a base material and contains 10 to 35 wt% of a softening material.

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