JP4855507B2 - Method for manufacturing printed wiring board having reflector function - Google Patents

Description

  The present invention is a method for producing a printed wiring board having a function as a light reflecting plate, in particular, a solder resist suitable for use as a permanent mask of a printed wiring board and a white solder resist film having a high reflectance, The printed wiring board formed by applying twice is related with the manufacturing method of the printed wiring board which has a function as a light reflection board of the backlight which used the light emitting diode element (LED) as the light source.

  2. Description of the Related Art In recent years, many display devices such as liquid crystals that can be made thin have been used as display devices for notebook personal computers and desktop personal computers, televisions, mobile phones, and the like. For example, since a liquid crystal display device itself is not a light emitter, a planar light source called a backlight is installed. The planar light source is required to have high utilization efficiency, and the light reflecting material used therefor is required to have higher performance.

  Thus, the reflector plays a large role in uniformly irradiating the entire screen of the liquid crystal display device. Reflective plates that satisfy this role are required to have a high degree of reflection characteristics. Conventionally, a film containing fine bubbles inside, a film added with a white pigment, etc., alone or with these films and a metal plate It has been used by attaching plastic plates.

  As the film, for example, after holding a roll formed by overlapping a thermoplastic polyester resin sheet and a separator in a pressurized inert gas atmosphere and containing the inert gas in the thermoplastic polyester resin sheet, A thermoplastic polyester resin foam sheet obtained by heating and foaming a thermoplastic polyester resin sheet containing the inert gas under normal pressure is known (Patent Document 1), MCPET (registered trademark): MC Pet (Furukawa) It is marketed under the name of “Electric Industry Co., Ltd.”. However, such a white film requires a molding process as a reflector and is not suitable for a molding process when a complicated shape is imparted.

  On the other hand, in recent years, light-emitting diodes (LEDs) that emit light at low power have come to be used in backlights for liquid crystal displays such as mobile terminals, personal computers, and televisions. Increasingly, light emitting diodes are directly mounted on printed wiring boards.

  Therefore, in order to efficiently use the light of the light emitting diode, for example, a printed wiring board having a white solder resist film described in Patent Document 2 and Patent Document 3 has been developed.

  However, by simply applying the white solder resist, when the film thickness is reduced, sufficient reflectivity as a reflector cannot be achieved, while the film thickness is required to obtain a high reflectivity. When the thickness is increased, it becomes impossible to meet the demand for high resolution that requires miniaturization, and it is difficult to realize a printed wiring board for a light emitting diode mounted with high reflectivity and high density.

  Moreover, if the white solder resist is formed with a thick film only from the photosensitive resin composition, it can meet the demand for high resolution, but the photopolymerization initiator that is an essential component of the photosensitive resin composition itself Has a problem that the surface of the photosensitive resin composition film is changed to yellow and the reflectance is lowered.

JP-A-8-72084 JP2007-322546A JP2008-211036

  In view of the above circumstances, an object of the present invention is a method for manufacturing a printed wiring board having a high-reflectance solder resist film, which can efficiently use light from a light-emitting diode element (LED), and has heat resistance, An object of the present invention is to provide a method for producing a printed wiring board on which a solder resist film having a high reflectance function, which has excellent resolution and can suppress coloring due to deterioration of reflectance over time, is formed.

In the first aspect of the present invention , a white solder resist A is applied to the substrate surface on which the electronic circuit wiring is formed and cured, and a white solder resist B is further applied on the white solder resist A. and curing, the method for manufacturing a printed wiring board having a reflector function of containing Muba backlight, the white solder resist a is a photosensitive resin composition, and the image formed by the photographic development process, the The white solder resist B is a thermosetting resin composition, and after the printing mask corresponding to the developed pattern of the photosensitive resin composition is placed on the developed photosensitive resin composition, the thermosetting is performed. It is a manufacturing method of a printed wiring board characterized by forming a coat of a property resin composition by a screen printing method . That is, after the white solder resist A is applied and dried, the white solder resist B is further applied onto the white solder resist A to form a two-layer white solder resist film. Since the white solder resist film has a two-layer structure, the film thickness of each white solder resist film can be made thinner than the film thickness of the conventional single-layer white solder resist film. Moreover, the aspect of this invention is a manufacturing method of the printed wiring board characterized by the DRY film thickness of the said white solder resist A being thicker than the thickness of the said electronic circuit wiring.

  A second aspect of the present invention is a method for producing a printed wiring board, wherein the white solder resist A is a photosensitive resin composition, and an image is formed by a photographic development method.

  A third aspect of the present invention is a method for producing a printed wiring board, wherein the white solder resist B is a thermosetting resin composition and a film is formed by a screen printing method.

  A fourth aspect of the present invention is a method for manufacturing a printed wiring board, wherein the reflectance of the coating film of the white solder resist B is equal to or higher than the reflectance of the coating film of the white solder resist A. That is, among the white solder resist films having a two-layer structure, the reflectance of the outer white solder resist film is equal to or higher than the reflectance of the white solder resist film on the substrate side.

  The fifth aspect of the present invention is a method for manufacturing a printed wiring board, further comprising a step of applying a white solder resist C on the white solder resist B and curing it. That is, in this aspect, the white solder resist film has a three-layer structure.

  A sixth aspect of the present invention is a method for producing a printed wiring board, wherein the white solder resist C is a thermosetting resin composition, and a film is formed by a screen printing method.

  In a seventh aspect of the present invention, the reflectance of the coating film of the white solder resist C is not less than the reflectance of the coating film of the white solder resist A and not less than the reflectance of the coating film of the white solder resist B. This is a method for manufacturing a printed wiring board. That is, the reflectance of the outermost white solder resist film is equal to or greater than the reflectance of the white solder resist film on the substrate side and in the middle layer.

  According to the first aspect of the present invention, since the white solder resist is applied in two steps, a sufficient film thickness of the white solder resist can be formed, and a sufficient reflectance as a reflector can be obtained. Furthermore, since the white solder resist is applied in two steps, the film thickness in one coating step can be made thinner than before, and high resolution of the coating can also be obtained. Therefore, it is possible to easily manufacture a printed wiring board for a light emitting diode that realizes high reflectance and high-density mounting.

  According to the second aspect of the present invention, since the white solder resist A on the substrate side of the two layers of the white solder resist film is a photosensitive resin composition, ink bleeding and printing sagging can be prevented, and the white solder resist film of the white solder resist film can be prevented. The resolution can be further improved.

  According to the third aspect of the present invention, the outer white solder resist B of the two layers of the white solder resist film is a thermosetting resin composition containing no photopolymerization initiator. Can be prevented from changing to yellow and the reflectance decreasing.

  According to the fourth aspect of the present invention, since the reflectance of the white solder resist B film is equal to or higher than the reflectance of the white solder resist A film, the white color on the surface of the printed wiring board changes over time. The light from the light source such as the light emitting diode element can be efficiently used.

  According to the fifth aspect of the present invention, since the white solder resist C film is further formed on the white solder resist B film, it is possible to form a sufficient thickness of the white solder resist, and thus sufficient as a reflector. Reflectance can be obtained. Further, since the white solder resist film of the printed wiring board can be made thick, it has excellent hiding power.

  According to the sixth aspect of the present invention, since the white solder resist C constituting the outermost layer film is a thermosetting resin composition, the printed wiring board surface changes to yellow even in a three-layer structure for thickening the film. Thus, it is possible to prevent the reflectance from decreasing.

  According to the seventh aspect of the present invention, since the reflectance of the white solder resist C film which is the outermost layer is equal to or higher than the reflectance of the white solder resist A and B films, even in the three-layer structure for thickening, the time Discoloration of the surface of the printed wiring board due to progress can be suppressed, and light from a light source such as a light emitting diode element can be used efficiently.

It is a fragmentary sectional view of the printed wiring board manufactured with the manufacturing method concerning the example of an embodiment of the present invention. 2 is an explanatory diagram of a printed wiring board according to Embodiment 1. FIG. It is explanatory drawing of the printed wiring board of Example 2. FIG. 6 is an explanatory diagram of a printed wiring board according to Embodiment 3. FIG. FIG. 10 is an explanatory diagram of a printed wiring board of Example 4. FIG. 10 is an explanatory diagram of a printed wiring board of Example 5. (A) The figure is explanatory drawing of the printed wiring board of the comparative examples 1 and 3, The same (b) figure is explanatory drawing of the printed wiring board of the comparative examples 2 and 4. FIG. It is explanatory drawing of resolution evaluation using the minimum opening diameter.

  Next, a method for manufacturing a printed wiring board according to an embodiment of the present invention will be described. As shown in FIG. 1, here, a printed wiring board 1 provided with an electronic circuit wiring 5 formed by etching a copper foil laminated on a substrate 4 is used. A printed wiring board 1 in which the white solder resist covering the substrate 4 has a two-layer structure, the photosensitive resin composition is used for the white solder resist A on the substrate 4 side, and the thermosetting resin composition is used for the outer white solder resist B. The manufacturing method will be described.

  As shown in FIG. 1, the printed wiring board 1 coated with the two-layer white solder resist manufactured by the manufacturing method according to the embodiment of the present invention polishes the surface of the substrate 4 on which the electronic circuit wiring 5 is formed ( For example, after buffing), the photosensitive resin composition that is the white solder resist A is applied and cured to form the photosensitive resin composition film 2, and then the thermosetting resin composition that is the white solder resist B The product is applied on the photosensitive resin composition film 2 and then cured to form the thermosetting resin composition film 3.

  Specifically, the photosensitive resin composition film 2 is applied by applying a photosensitive resin composition, which is a white solder resist A, to the polished substrate 4 surface by a screen printing method so that the DRY film thickness becomes a predetermined thickness. A step of preliminarily drying the substrate 4 coated with the photosensitive resin composition; and a step of covering the photosensitive resin composition film 2 formed by the preliminary drying with an exposure mask having a predetermined pattern; It forms by passing through the process of exposing, and the process of developing, after removing the mask covered after exposure.

  The thermosetting resin composition film 3 has a step of covering the photosensitive resin composition film 2 with a printing mask having a predetermined pattern and thickness, and a DRY film thickness from the printing mask to a predetermined thickness. The thermosetting resin composition film is subjected to a step of applying a thermosetting resin composition by a screen printing method and a step of predrying the substrate 4 on which the thermosetting resin composition is applied. 3 is formed. Then, the photosensitive resin composition film 2 and the thermosetting resin composition film 3 are further cured by heat-treating the substrate 4 on which the thermosetting resin composition film 3 is formed at a predetermined temperature, so that two layers are formed. A printed wiring board 1 coated with a white solder resist is manufactured.

  First, the formation process of the photosensitive resin composition film 2 will be described in detail. Although the photosensitive resin composition to be used will not be specifically limited if it becomes a white coating film, For example, (A) carboxyl group containing photosensitive resin, (B) photoinitiator, (C) diluent, ( There is a white photosensitive resin composition containing D) titanium oxide and (E) an epoxy compound.

  The component (A) is preferably a resin having a carboxyl group that does not have an aromatic ring, but is not particularly limited, and is a photosensitive carboxyl group-containing resin having one or more photosensitive unsaturated double bonds, Any of the carboxyl group-containing resins having no photosensitive unsaturated double bond can be used. As an example of the component (A), a radical polymerizable unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid was reacted with at least a part of the epoxy group of the alicyclic skeleton epoxy resin having two or more epoxy groups in the molecule. Thereafter, the resulting hydroxyl group can be reacted with a polybasic acid anhydride.

  (B) component will not be specifically limited if it is a photoinitiator generally used, For example, an oxime system initiator, a benzoin, an acetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1- ON, 1-hydroxycyclohexyl phenyl ketone, benzophenone and the like. The usage-amount of a photoinitiator is 5-20 mass parts with respect to 100 mass parts of photosensitive resin of (A) component, for example.

  The diluent of component (C) is, for example, a photopolymerizable monomer, in order to obtain a coating film having acid resistance, heat resistance, alkali resistance, etc. by sufficiently photocuring the photosensitive resin of component (A). Used for. Examples of the photopolymerizable monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and the like. Can be mentioned. The addition amount of a diluent is 2.0-40 mass parts with respect to 100 mass parts of photosensitive resin of (A) component, for example.

  (D) Titanium oxide of a component is a titanium oxide particle which has an anatase and a rutile crystal structure, and is used in order to whiten a coating film. From the viewpoint of whiteness, rutile type titanium oxide is preferable. In order to raise the whiteness of a coating film, the usage-amount of a titanium oxide is 10-120 mass parts with respect to 100 mass parts of photosensitive resin which is (A) component, for example.

  The epoxy compound of component (E) is a white photosensitive resin composition that increases the cross-linking density of the cured coating film, and is a resin cured film that is less susceptible to discoloration and reflectance reduction of the white coating film due to UV irradiation and thermal history. For example, an epoxy resin is added. Examples of the epoxy resin include bisphenol A type epoxy resin, novolak type epoxy resin (phenol novolak type epoxy resin, o-cresol novolak type epoxy resin, p-tert-butylphenol novolak type, etc.), bisphenol F and bisphenol S with epichlorohydrin. Bisphenol F-type and bisphenol S-type epoxy resins obtained by reaction, alicyclic epoxy resins having cyclohexene oxide groups, tricyclodecane oxide groups, cyclopentene oxide groups, and the like, tris (2,3-epoxypropyl) isocyanurate , Triglycidyl isocyanurate having a triazine ring such as triglycidyl tris (2-hydroxyethyl) isocyanurate, dicyclopentadiene type epoxy resin, Adama It can be exemplified Tan type epoxy resin. The usage-amount of an epoxy resin is 10-50 mass parts with respect to 100 mass parts of photosensitive resin which is (A) component, for example.

  Next, the process of apply | coating the above-mentioned photosensitive resin composition is demonstrated. In order to apply the photosensitive resin composition to the substrate 4, for example, a screen printing method is used. At this time, the screen printing of the photosensitive resin composition is full-surface printing, and the lower limit of the DRY film thickness is 10 μm from the viewpoint of protection against peeling due to external impact in the work process, preferably prevention of the underlying conductor oxidation The upper limit of the DRY film thickness is 30 μm from the viewpoint of solvent removal from the coating film and its hardness, preferably 25 μm from the viewpoint of preventing entrainment of bubbles during coating. The thickness of the photosensitive resin composition during screen printing is adjusted.

  The preliminary drying step of the photosensitive resin composition is for forming the photosensitive resin composition film 2 by volatilizing the solvent from the photosensitive resin composition to make the surface of the coating tack-free. The preliminary drying temperature is preferably 50 to 100 ° C., and the drying time is preferably 20 to 25 minutes. The heating device in the preliminary drying step is not particularly limited, and for example, a hot air furnace or an electric furnace can be used.

In the exposure process of the photosensitive resin composition film 2, exposure by direct laser writing or exposure by active energy rays using a negative mask that prevents passage of active energy rays is performed. In the exposure with active energy rays, as a negative mask to be covered, a negative film is used when the active energy rays are ultraviolet rays, a metallic mask when electron rays are used, and a lead mask when X-rays are used. In the embodiment of the present invention, it is preferable to use ultraviolet rays for the active energy rays in that a simple negative film can be used. The irradiation amount of the active energy ray is 10 to 1000 mJ / cm ² . In the exposure using the negative film, for example, a negative film having a pattern other than the soldering land of the electronic circuit wiring 5 pattern is made to adhere to the photosensitive resin composition film 2 and then irradiated with ultraviolet rays. Is done.

  In the developing step, the photosensitive resin composition film 2 is developed by removing the non-exposed areas corresponding to the soldering lands with a dilute alkaline aqueous solution. As a specific example, there is a developing method in which a non-exposed area is removed by spraying a diluted alkaline aqueous solution onto the photosensitive resin composition film 2. Although the dilute alkali aqueous solution used is not specifically limited, For example, 0.5-5 mass% sodium carbonate aqueous solution can be used.

  Next, details of the step of forming the thermosetting resin composition film 3 formed on the developed photosensitive resin composition film 2 will be described. The thermosetting resin composition to be used is not particularly limited as long as it becomes a white coating film. For example, (A) an epoxy resin, (B) a compound having a carboxyl group as an epoxy curing agent, (C) curability. There is a white thermosetting resin composition containing an accelerating compound, (D) an organic solvent, and (E) titanium oxide.

  The epoxy resin of component (A) is not particularly limited as long as it is generally used. For example, “Epicron 840”, “Epicron 1050”, “Epicron 3050”, (Dainippon Ink), which are bisphenol A type epoxy resins, are used. Chemical industry).

  (B) Although it does not specifically limit about the compound which has a carboxyl group as an epoxy hardening | curing agent of a component, What does not have an aromatic ring is desirable, for example, Daicel Chemical Industries "Cyclomer P (ACA) Z-251" , “Cyclomer P (ACA) Z-250”, “Cyclomer P (ACA) Z-300”, “Cyclomer P (ACA) Z-320” and the like. The usage-amount is 50-150 mass parts with respect to 100 mass parts of epoxy resins of (A) component, for example.

  (C) The sclerosing | hardenable acceleration | stimulation compound of a component is not specifically limited if it crosslinks an epoxy resin, and is generally used, For example, a melamine, imidazole, a dicyandiamide etc. are mentioned. The usage-amount is 0.01-10 mass parts with respect to 100 mass parts of epoxy resin of (A) component, for example.

  The organic solvent of component (D) is only required to be compatible with the components (A) and (B). For example, ketones such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene And the like. The usage-amount is 1-500 mass parts with respect to 100 mass parts of epoxy resins of (A) component, for example.

  In addition, the titanium oxide of (E) component is the same as the description of the titanium oxide described in the said photosensitive resin composition, Moreover, the usage-amount is with respect to 100 mass parts of epoxy resins of (A) component, For example, 10 to 120 parts by mass.

  Next, the process of apply | coating the above-mentioned thermosetting resin composition is demonstrated. After a printing mask corresponding to the pattern of the developed photosensitive resin composition film 2 is placed on the photosensitive resin composition film 2, the above-described thermosetting resin composition is applied by a screen printing method. At this time, the lower limit of the DRY film thickness of the thermosetting resin composition is 10 μm from the point of reflectance, preferably 20 μm from the point of higher reflectance, and the upper limit of the DRY film thickness is The thickness of the thermosetting resin composition at the time of screen printing is adjusted so as to be 30 μm from the point of solvent removal in the medium and its hardness, and preferably 25 μm from the point of prevention of bubble entrainment during coating.

  The pre-drying step of the thermosetting resin composition is for forming the thermosetting resin composition film 3 by volatilizing the solvent from the thermosetting resin composition to bring the surface of the coating into a tack-free state. It is. The predrying conditions are preferably a predrying temperature of 50 to 100 ° C. and a drying time of 20 to 25 minutes as in the predrying step of the photosensitive resin composition, and the heating device is not particularly limited. Etc. can be used.

  In the post-cure process for further curing the photosensitive resin composition film 2 and the thermosetting resin composition film 3, for example, the heating temperature is 130 to 170 ° C., and the heating time is 20 to 80 minutes. A heating apparatus is not specifically limited, For example, a hot stove or an electric furnace can be used.

  Next, another embodiment of the present invention will be described. In the above embodiment, the photosensitive resin composition is used as the white solder resist A on the substrate 4 side, and the thermosetting resin composition is used as the outer white solder resist B. Instead, the white solder resist A is heated. A photosensitive resin composition may be used for the curable resin composition and the white solder resist B. Moreover, the photosensitive resin composition may be used for both the white solder resists A and B, and the thermosetting resin composition may be used for both the white solder resists A and B.

  Further, a white solder resist C may be further coated on the white solder resist B to make the solder resist film thicker. The white solder resist C may be a photosensitive resin composition or a thermosetting resin composition, and the post-cure process may be performed once after the white solder resist C is applied. Of course, if necessary, a white solder resist may be applied on the white solder resist C and cured to form a white solder resist film having four or more layers.

  In the above embodiment, full-screen printing by the screen printing method is used, but it is not particularly limited as long as it is a coating means that can be applied uniformly. For example, instead of the screen printing method, a spray coater, a honmelt coater, a bar coater, etc. Applicators, blade coaters, knife coaters, air knife coaters, curtain flow coaters, roll coaters, gravure coaters, offset printing, dip coaters, brush coating, and other conventional methods can all be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to this.

  A printed wiring board was produced by the steps described below. The description of the printed wiring board 1 according to Examples 1 to 5 is shown in FIGS. 2 to 6, the description of the printed wiring board 11 according to Comparative Examples 1 and 3 is shown in FIG. The description of the printed wiring board 11 is shown in FIG. In addition, the same code | symbol was attached | subjected to the structure same as FIG.

  In Examples 1 to 4, a solder resist A film 7 and a solder resist B film 8 were formed on the substrate 4, and in Example 5, a solder resist C film 9 was further formed. In Comparative Examples 1 and 3, only the solder resist A film 12 was formed, and in Comparative Examples 2 and 4, only the solder resist A film 13 was formed.

-Surface treatment of substrate 4: Buffing and formation of photosensitive resin composition film Photosensitive resin composition: DSR-330S70-11W (manufactured by Tamura Kaken Co., Ltd.)
Coating: Screen printing coating film thickness: DRY 20-23 μm
Pre-drying :: 20 minutes at 70 ° C. (25 minutes in BOX furnace)
Exposure: 400 mJ / cm ² on resist (OMW HMW-680GW)
Development: 1% Na ₂ CO ₃ -30 ° C.-0.1 MPa-60 seconds Post cure: 60 minutes at 150 ° C. (70 minutes in BOX furnace). However, only when coating as the outermost layer.
-Formation of thermosetting resin composition film Thermosetting resin composition: RPW-210 (manufactured by Tamura Kaken Co., Ltd.)
Coating: Screen printing coating film thickness: DRY 20-23 μm
Pre-drying :: 20 minutes at 70 ° C. (25 minutes in BOX furnace)
Post cure: 60 minutes at 150 ° C. (70 minutes in BOX furnace). However, only when coating as the outermost layer.

  Table 1 shows the types and thicknesses of the resin compositions of the solder resist films of Examples 1 to 5 and Comparative Examples 1 to 4.

  Subsequently, in order to investigate various properties of the solder resist films of Examples 1 to 5 and Comparative Examples 1 to 4 produced in the above process, the tests were conducted as follows.

(1) Measurement of reflectivity The reflectivity was measured at 450 nm using a spectrophotometer U-3410 (manufactured by Hitachi, Ltd .: φ60 mm integrating sphere). In Table 1, the initial reflectance is the reflectance of the solder resist film of the substrate 4 produced in the above process. The reflectance after heat treatment is used as an index for confirming the heat resistance and the presence or absence of reflectance deterioration with time. The solder resist film of the substrate 4 heat-treated at 260 ° C. for 5 minutes. Is the reflectance.
(2) Visual evaluation after heating About the solder resist film of the substrate 4 which is used as an index for confirming heat resistance and the presence or absence of a color change from white to yellow over time, and heat-treated at 150 ° C. for 1000 hours. The degree of discoloration was evaluated visually. A white color with no discoloration confirmed ◎, a slight discoloration to yellow is observed, but there is no quality problem, ○, a discoloration to yellow is observed, and there is a possibility of causing a quality problem The case where the discoloration to yellow was markedly problematic in terms of quality was evaluated as x, in four stages.
(3) Resolution As shown in FIG. 8, the minimum opening diameter (φ) 6 that can form a circular pattern as an opening is taken as the resolution value.
(4) Pencil hardness Press the B to 9H pencil sharpened so that the tip of the core is flat on the solder resist film at an angle of about 45 °, and the pencil hardness will not cause peeling of the coating film. Recorded.

  As apparent from Table 1, in Examples 1 to 5 in which two or more layers of solder resist films were formed, the initial and post-heat treatment reflectivities, visual evaluation after heating, resolution, and pencil hardness were all evaluated. Excellent characteristics were obtained in the items. Accordingly, it has been found that Examples 1 to 5 are excellent in heat resistance, resolution, and reflectance, and can suppress deterioration in reflectance and discoloration to yellow over time. In particular, Examples 2 and 5 using the photosensitive resin composition for the solder resist A and the thermosetting resin composition for the solder resist B or C constituting the outermost layer provided excellent characteristics for all the evaluation items. In particular, Example 5 having a total film thickness of 60 μm was extremely excellent in reflectance.

  Moreover, from the results of the reflectances of Examples 2 and 3, when the thermosetting resin composition is used for the solder resist B, the reflectance is higher both at the initial stage and after the heat treatment than when the photosensitive resin composition is used. Therefore, it has been found that discoloration of the solder resist film of the printed wiring board can be particularly suppressed. This is because the thermosetting resin composition does not contain a photopolymerization initiator that changes to yellow over time, and therefore, by using the thermosetting resin composition for the solder resist B, It is considered that the reflectance of the solder resist film is higher than that when the photosensitive resin composition is used for the solder resist B.

  On the other hand, for Comparative Examples 1 to 4, which are conventional products in which a single layer solder resist film is formed, in Comparative Example 1, visual evaluation and pencil strength after heating, in Comparative Example 2, resolution and pencil strength, comparison In Examples 3 and 4, the initial and post-heat treatment reflectances and the visual evaluation after heating were inferior.

  A printed wiring board on which a solder resist film having a high reflectance function that can suppress coloring due to heat resistance, resolution, and deterioration of reflectance over time can be obtained. High utility value in the technical field of lights.

DESCRIPTION OF SYMBOLS 1 Printed wiring board 2 Photosensitive resin composition film 3 Thermosetting resin composition film 4 Board | substrate 7 Solder resist A film 8 Solder resist B film 9 Solder resist C film 12 Solder resist A film 13 Solder resist A film

Claims (6)

A step of the substrate surface which electronic circuit wiring is formed, by applying a white solder resist A, cured,
The white on the solder resist A, a further white solder resist B is applied, a method for manufacturing a printed wiring board having a step of curing, the reflector functions including Muba backlight,
The white solder resist A is a photosensitive resin composition, and an image is formed by photographic development. The white solder resist B is a thermosetting resin composition, and the developed pattern of the photosensitive resin composition is formed. A method for producing a printed wiring board, comprising: coating a corresponding printing mask on the developed photosensitive resin composition, and then forming a film on the thermosetting resin composition by a screen printing method. The printed wiring board manufacturing method according to claim 1, wherein the white solder resist A has a DRY film thickness larger than a thickness of the electronic circuit wiring .   The method for producing a printed wiring board according to claim 1, wherein the reflectance of the coating film of the white solder resist B is equal to or higher than the reflectance of the coating film of the white solder resist A.   Furthermore, the manufacturing method of the printed wiring board of Claim 1 including the process of apply | coating the white solder resist C on the said white solder resist B, and making it harden | cure. The said white soldering resist C is a thermosetting resin composition, and a film is formed by the screen printing method, The manufacturing method of the printed wiring board of Claim 4 characterized by the above-mentioned. The reflectance of the coating film of the white solder resist C is, the white solder resist A coating reflectivity over the, and claim 4, characterized in that said at white solder resist B of coating reflectance or more or 5. A method for producing a printed wiring board according to 5 .

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