JP2014168029A - Process of manufacturing circuit board that eliminates need of character and symbol printing and such by a screen printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of manufacturing a circuit board capable of printing characters and such without using character and symbol printing and such by a screen printing.SOLUTION: The process of manufacturing a circuit board in which, by changing ultraviolet light irradiation amount to a combined coat of a coloring ink layer and a solder resist ink layer (also called as a permanent resist) containing an epoxy resin and an acrylic resin to generate a difference of ratio in crosslinking density and a degree of polymerization of the solder resist ink on the circuit board, differences in refractive index and transparency are generated to make color of the coloring ink visible.

Description

Detailed Description of the Invention

  The present invention uses a solder resist ink (hereinafter referred to as MSR) containing an epoxy resin and an acrylic resin partially remaining in carboxylic acid, and changes the UV irradiation amount or the amount of drying heat to change the crosslinking density of the MSR layer.・ Circuit board that changes the refractive index and transparency by changing the ratio of the degree of polymerization, etc., and the letters for recognition of mounted parts, etc., turn the background color by virtue of the difference in the refractive index and transparency, so that even minute characters can be clearly seen It is related with the manufacturing method.

  The circuit board is coated with solder resist to protect the copper circuit, etc. In order to provide accurate information on the mounted components on this solder resist, identification characters and symbols such as names of mounted components are screen printed. Is printed.

  However, in recent years, lighter, thinner, and smaller sizes have been drastically advanced. In the printing method using screen printing, the size and resolution of characters are influenced by the mesh of the screen plate used. The mesh size through which ink for letters, symbols, etc. can pass is limited, making it impossible to meet the demand for lower case letters.

  Furthermore, since a high-performance product is required, the mounting area of the circuit board is reduced, the mounted components are downsized, and many components are mounted. In the current screen character printing method, the size of characters has reached the limit, and it has become impossible to physically represent all characters.

  Also, character printing by the screen printing method requires frequent cleaning of the back side of the plate with an organic solvent during work so that the plate is not clogged. In addition, the organic solvent is used in an open state to remove ink adhering to the plate after printing. Also, in order to store the printing plate, it is necessary to wash and remove the ink that could not be removed by the dipping method or the spraying method, and a large amount of organic solvent is used in this process. As a result, the deterioration of the working environment and the problem of air pollution are becoming issues.

  The printed matter by screen printing has the disadvantage that the lines become jagged due to mesh mesh, and the lowercase letters etc. are unclear and unreadable, so the lowercase letters and symbols etc. are clear from miniaturization of parts and high density mounting Is required.

  Character printing by the screen printing method takes a great deal of time to adjust the position of the plate and the adjustment of the plate elongation and the position after printing. Furthermore, a series of work such as fine adjustment during work can only be performed by skilled workers. The Japanese circuit board manufacturing industry handles many kinds of small lots, and the number of plate replacements is large. As a result, it takes a lot of time to print characters. The current situation is that the number of personnel has been increased to surpass production. At present, the ratio of personnel in this process is higher than that in other processes, leading to an increase in manufacturing costs.

  Character printing plates using the screen printing method need to be stored for several years in order to produce repeat products, and a large storage space is required to store the printing plates. Storage management costs are one of the factors that increase manufacturing costs. .

  Since the recognition characters (hereinafter referred to as “characters”) such as component mounting are printed on the solder resist, the surface has 10-20 μm irregularities due to the rise of the ink, which is caused by poor bonding of the mounting components or dropping of fine components. Many defective products occur, and a great deal of time is wasted on re-registration, which increases manufacturing costs. The screen character printing method has a fatal negative factor in such a small surface mount component.

  As an alternative to the screen printing method, a method of printing characters and the like by applying ink on a substrate with a roll coater and performing exposure development, and a coating method using an ink jet printer are disclosed. (For example, see Patent Documents 1 and 2)

JP 2002-214778 A JP-A-9-133502

  In screen character printing, since the lines of characters, symbols, etc. are formed in a jagged manner, lowercase letters, symbols, etc. are unclear. Furthermore, there is a limit to the ink passing mesh, and it is impossible to follow the circuit board corresponding to the minimum surface mount component. Also, as an alternative to the screen printing method, fine characters can be printed by a method of printing characters by applying ink on a substrate with a roll coater and performing exposure development, or a coating method using an ink jet printer. However, since the ink is applied onto the solder resist surface as in the case of screen printing, printing in a flat state cannot be performed.

  In screen character printing, it takes a lot of time to set a printing plate, and skill is required for printing. In order to increase productivity, many skilled workers are required. Moreover, the required area of the printing plate is required to be 3 to 5 times that of the character printing portion, which requires a large place for storage.

  Screen character printing uses a large amount of organic solvent, which deteriorates the working environment and increases the air pollution load. Depending on the solvent used, there may be a risk of cancer induction. In addition, since many of the operations are performed open, they are at risk of organic solvent poisoning.

  The present invention is to provide a circuit board manufacturing method capable of solving the above-described problems.

As a result of intensive studies to solve the above problems, the present inventor uses a photographic method, and maintains a flat solder resist surface by following the procedure described below, and clearly reads even lowercase letters such as mounted parts. As a result, the present invention has been completed by establishing a circuit board manufacturing method.
However, if black processing or brown processing is performed like a multi-substrate and the color can be used as a recognition character for a mounted component or the like, it should be noted that there is no problem even if the colored ink layer processing is omitted.

As an example of the procedure,
(1) Circuit forming substrate by etching, etc. (2) Surface preparation and drying (3) Primer treatment (may be removed) (4) Drying A (5) MSR coating (6) Drying B (7) ▼ Primary exposure ⇒ ▲ 8 ▼ Secondary exposure ⇒Development ⇒ ▲ 9 ▼ Dry ⇒To the next process

  The surface conditioning and drying may be performed by a general method, but the unevenness on the circuit surface is preferably within 3 μm, but the unevenness is not a problem if there is no problem in function.

  Characteristic ink can be read clearly by using a colored ink having a functional group as a primer layer as shown in FIG. 1 or by providing an ink layer between MSR layers as shown in FIG. A method for manufacturing a circuit board according to claim 1. However, it should be noted that there is no problem even if the color of the colored ink changes due to exposure.

  Although it does not care about the coating method of colored ink, it is desirable to apply as uniformly as possible using roll coating, curtain coating, spray coating, electrostatic coating, etc., and the coating thickness is 2 μm to 300 μm, preferably 5 μm to 150 μm. If the coating thickness is 2 μm or less, characters and the like will not be clear, and if it is 300 μm or more, the distinction difference between identification characters will not change and the effect will not be exhibited.

  The drying A needs to obtain a dry state in which the colored ink and the MSR are not mixed at the time of application in the next step, the temperature is 40 ° C. to 100 ° C., the time is 5 minutes to 60 minutes, and preferably the temperature is 50 ℃ -80 ℃, time is 10-30 minutes. If the drying is sweet, it mixes with the MSR, and the sharpness of characters and the like is lost. If the drying is strong, the non-tip portion does not come off at the time of development, adheres to the base material, and hinders the mounting of parts. It is recommended to use a hot air dryer for drying.

  The MSR is desirably applied uniformly (FIGS. 1 and 2), and the coating thickness is 2 μm to 300 μm, preferably 5 μm to 150 μm. If the coating thickness is 2 μm or less, pinholes and the like are formed, and sufficient circuit protection cannot be achieved. Above 300 μm, the UV irradiation dose does not reach the deep part sufficiently within the working time considering productivity, the deep part MSR is obtained at the time of development, and the metallic copper that is the circuit is not protected, and corrosion is caused in the subsequent processes. This is a cause of disconnection and migration.

  In MSR, the mixing ratio of the epoxy resin and the acrylic resin is arbitrary, but the character can be made clearer by increasing the ratio of the epoxy resin slightly more than the acrylic resin. Circuit board manufacturing method.

  The proportion of the epoxy resin is 40% to 80%, preferably 50.1% to 65%. If it is 40% or less, or 80% or more, it is difficult to obtain contrast between the transparent portion and the opaque portion with respect to the change in the irradiation amount of ultraviolet rays, and the characters become unclear.

  Dry B may be in a dry state that does not interfere with exposure in the next step, and the temperature is 40 ° C to 120 ° C, preferably 60 ° C to 95 ° C. The time is 5 to 100 minutes, preferably 10 to 70 minutes. When the dry state is sweet, MSR adheres to the film used, and it takes time to remove the ink and the workability deteriorates. Moreover, the thickness of the MSR layer becomes insufficient by adhering to the film, which hinders circuit protection. If the drying is excessive, the crosslinking / polymerization reaction proceeds excessively by the amount of heat, and the MSR remains in the non-image area, which is an unnecessary part of the solderist, in the development process, making it impossible to mount the parts.

  The primary exposure is set as shown in FIG. 3, and the image area, which is the position of the component to be mounted, cuts ultraviolet rays with a mask film and irradiates a small amount of the non-image area. The irradiation amount is MSR in the development process. ((4)) is reduced to such an extent that it does not flow out, thereby reducing the crosslink density and the degree of polymerization due to the reaction between the epoxy resin and the acrylic resin. As a result, an MSR coating film close to the transparency of the original MSR is obtained.

In the case of using a negative type MSR and setting as shown in FIG. 3, the primary exposure uses a film for a negative type solder resist and irradiates ultraviolet rays. Dose is ^{10mJ / cm 2 ~300mJ / cm 2} , preferably ^{40mJ / cm 2 ~150mJ / cm 2} . If it is 10 mJ / cm ² or less, the MSR is removed in the development process due to insufficient crosslinking and polymerization. If it is 300 mJ / cm ² or more, crosslinking / polymerization proceeds excessively, the transparency is lowered, and the characters become unclear.
Needless to say, when using positive type colored ink and solder resist ink, the reverse type film is used.

  4 or 6, set the part mounting position and the character line area, cut the ultraviolet rays with a mask film, and irradiate only the non-image area, epoxy resin and acrylic The method for producing a circuit board according to claim 1, wherein an MSR coating film having a low degree of transparency is obtained by increasing the crosslinking density and the degree of polymerization by reaction with a resin.

In the primary exposure when set as shown in FIG. 4 or FIG. 6, ultraviolet rays are irradiated using a photomask film in which the component mounting position is a negative type and the identification characters and symbols are processed into a positive type. The irradiation amount is 50 mJ / cm ^{2 to} 800 mJ / cm ² , preferably 100 mJ / cm ^{2 to} 600 mJ / cm ² . At 50 mJ / cm ² or less, due to insufficient crosslinking and polymerization, the resin film in the non-image area is highly transparent and the identification characters are unclear. If it is 800 mJ / cm ² or more, the sharpness of the identification character is not changed, and time and energy are wasted.

  The secondary exposure is set as shown in FIG. 4, and the ultraviolet rays at the character position and the component position to be mounted are cut, and the non-image area is irradiated. By making the irradiation amount larger than the irradiation amount of the primary exposure, the reaction between the epoxy resin and the acrylic resin in the non-image area proceeds, and as shown in the schematic diagram of FIG. The circuit board according to claim 1, wherein the transparency of the MSR coating film is lowered to cause a difference in transparency between the MSR coating film at the character position and the MSR coating film at the non-image area. Method.

When the MSR used is a negative type, the secondary exposure is set after overlaying a negative type solder resist film and a positive type component mounting identification film (hereinafter referred to as character film) on the indicated position on the circuit board. Irradiate ultraviolet rays. Dose is ^{100mJ / cm 2 ~1500mJ / cm 2} , preferably ^{200mJ / cm 2 ~800mJ / cm 2} . When the irradiation amount is 100 mJ / cm ² or less, a difference in transparency between the image portion such as the character portion and the non-image portion of the MSR layer cannot be obtained at the time of development, and the character or the like becomes unclear and is not useful. At 1500 mJ / cm ² or more, affected by the diffuse reflection of light, the image area is also cross-linked and polymerized, and the position of the mounted part cannot be developed (so-called fogging occurs). become unable.
Needless to say, all the films used in the case of using the positive type colored ink and the solder resist ink use the opposite film as in the case of using the negative type ink.

  Alternatively, when the film is set as shown in FIG. 4 or FIG. 6 in the primary exposure, the image area at the component mounting position is cut off the ultraviolet rays by the mask film, and the image area such as characters. The non-image area is irradiated with a small amount, the reaction between the epoxy resin and the acrylic resin in the image area such as characters is suppressed, and the cross-link density and the degree of polymerization are reduced, so that the resin transparency of the character area is high. A method for producing a circuit board according to claim 1, wherein a coating film is obtained.

  9. The method of manufacturing a circuit board according to claim 1, wherein a mask film for solder and a mask film of characters / symbols are used in an overlapping manner.

  9. The method of manufacturing a circuit board according to claim 1, wherein a mask film in which a solder portion and a character portion are synthesized on the same film is used.

  As shown in FIG. 7, the component mounting position which is the image line portion can block 100% of ultraviolet rays, the identification character positions of components to be mounted can be blocked by 50 to 95%, and the non-image area portion can transmit 100% ultraviolet rays. A method for producing a circuit board according to claim 1, wherein a light and dark film having a function is used.

When using a film with light and shade, after setting it so as to match the designated position of the circuit board, irradiation with ultraviolet rays may be performed once, and the irradiation amount is 100 mJ / cm ^{2 to} 1000 mJ / cm ² , preferably 200 mJ / cm ^{2 to} 800 mJ / cm ² . When the irradiation amount is 100 mJ / cm ² or less, the resin film in the non-image area is highly transparent and the identification characters are unclear due to insufficient crosslinking and polymerization. If it is 1000 mJ / cm ² or more, the sharpness of the identification character is not changed, and not only the working time is wasted but also the fogging phenomenon occurs.

  Development, drying, post-exposure, etc. may be performed according to the handling instructions of the solder resist ink manufacturer used.

  By changing the irradiation amount of ultraviolet rays on the MSR coating film, which is a mixture of epoxy resin and residual acrylic resin with some carboxylic acid, it is possible to print minute characters, etc., which was impossible with screen printing, This makes it possible to support circuit boards on which ultra-small surface-mounted components are mounted, thereby helping to make effective use of resources.

  The amount of the organic solvent used can be reduced by 1/50 to 1/70 as compared with the screen printing method, which contributes to the improvement of the working environment and thus greatly contributes to the reduction of the environmental load.

  Because it is a photographic method, the film and the substrate can be combined with pins, etc., so that even if they are not skilled workers, anyone can work efficiently and productivity is greatly improved, which can contribute to reduction of production costs.

  Since the storage is a film, the storage area can be reduced by about 1/100 or more compared to the screen printing method, which can contribute to a reduction in storage cost.

  Since the solder resist surface is flat, it is easy to mount micro-parts, and it is possible to contribute to improvement of productivity by reducing redo such as missing parts.

The board | substrate cross section at the time of using colored ink as a primer layer for a lower layer. The board | substrate sectional drawing at the time of using colored ink between MSR layers. Substrate cross-section during primary exposure Substrate cross-section during secondary exposure Schematic diagram of difference in crosslinking density and degree of polymerization depending on exposure amount Cross-sectional view of the substrate during exposure when using a synthetic mask film Cross-sectional view of the substrate during exposure when using a mask film with shading Substrate cross-section after development

  The present invention will be described with reference to examples and comparative examples. However, the scope of the present invention is not limited to these examples, and various modifications can be made without departing from the spirit of the present invention. is there.

Common equipment used in the examples and comparative examples of the present invention,
(1) Tokai Shinei Electronics Co., Ltd. test substrate, double-sided through-hole substrate that has been etched, its size is 500 dm ² (250 mm × 200 mm) (hereinafter referred to as substrate)
(2) Abrasion # 180 was made with a scrubbing machine manufactured by Ishii Co., Ltd. for leveling (brush polishing).
(3) The coloring ink is applied by a screen printer DF65 P manufactured by Mino Group.
(4) Solder resist ink is applied by a screen printer DF65P manufactured by Mino Group.
(5) The coloring ink is SSR-6500C manufactured by Yamaei Chemical Co., Ltd.
(6) The hot air dryer is a BOX dryer manufactured by Mesh Co., Ltd.
(7) The exposure machine is THE-7000MC manufactured by Hitec Corporation.
(8) The developer is a 2% (v / v) solution of trade name developer D-701 manufactured by Yamatoya Corporation.
(9) The developing machine is manufactured by Tokyo Chemical Industry Co., Ltd.
(10) The mask film for solder resist is a negative type for testing by Tokai Shinei Electronics Co., Ltd.
(11) The mask film for characters is a positive type for testing by Tokai Theological Electronics Co., Ltd.

  A method for creating evaluation equipment used in Examples and Comparative Examples of the present invention.

  Creation of evaluation equipment when colored ink is used as a primer layer.

Outline of creation of evaluation equipment of Example Substrate ⇒ Surface conditioning and drying ⇒ Colored ink application ⇒ Dry A ⇒ Application of MSR ⇒ Dry B ⇒ Primary exposure ⇒ Secondary exposure ⇒ Development (30 ° C, 0.25 MPa, effective chamber length Adjust the speed so that development can be done at 1/2) ⇒Dry (50min / 150 ℃) ⇒Evaluation

The working conditions of Examples 1 to 9 are shown in Table-1.
The MSR used is the product name SSR-6600W of Sanei Chemical Co., Ltd.

The working conditions of Comparative Examples 1 and 2 are shown in Table-2.
The used solder resist ink does not contain an epoxy resin (hereinafter referred to as SR), product name Photofiner PSR-4000 CC02 / CA-40 manufactured by Taiyo Ink Manufacturing Co., Ltd.

  Creation of evaluation equipment when a colored ink layer is applied between MSR layers.

Outline of preparation of evaluation equipment in Examples Substrate ⇒ Surface-conditioning and drying ⇒ Application of primary MSR ⇒ Drying C ⇒ Application of colored ink ⇒ Drying D ⇒ Application of secondary MSR ⇒ Drying E ⇒ Primary exposure ⇒ Secondary exposure ⇒ Development ( (Adjust the speed so that development is possible at 30 ° C, 0.25 MPa, 1/2 of the effective chamber length) ⇒ Drying (50 minutes / 150 ° C) ⇒ Evaluation

The working conditions of Examples 10 to 13 are shown in Table-3.
The MSR used is the product name SSR-6600 of Sanei Chemical Co., Ltd.

The working conditions of Comparative Examples 3 to 4 are shown in Table-4.
SR used is the product name Photofiner PSR-4000 CC02 / CA-40 of Taiyo Ink Manufacturing Co., Ltd.

  Creation of evaluation equipment when combined with drying temperature.

Outline of preparation of evaluation equipment of Example Substrate ⇒ Surface-conditioning and drying ⇒ Application of colored ink ⇒ Dry F ⇒ Application of primary MSR ⇒ Dry G ⇒ Application of secondary MSR ⇒ Dry H ⇒ Exposure ⇒ Development (30 ° C, 0. Adjust the speed so that development is possible at 25MPa and 1/2 of the effective chamber length) ⇒Dry (50min / 150 ℃) ⇒Evaluation

The working conditions of Examples 14 to 17 are shown in Table-5.
The MSR used is the product name SSR-6600W of Sanei Chemical Co., Ltd.

The working conditions of Comparative Example 5 are shown in Table-6.
SR used is the product name Photofiner PSR-4000 CC02 / CA-40 of Taiyo Ink Manufacturing Co., Ltd.

  Creation of evaluation equipment when the solder part and the character part are created on the same film.

Outline of Preparation of Evaluation Equipment of Example The same film was used as a mask film for primary exposure.
Substrate ⇒ Surface smoothing and drying ⇒ Application of colored ink ⇒ Drying A ⇒ Application of MSR ⇒ Drying B ⇒ Primary exposure ⇒ Secondary exposure ⇒ Development (30 ° C, 0.25 MPa, effective chamber length 1/2) Speed adjustment) ⇒ Drying (50 min / 150 ° C) ⇒ Evaluation

The working conditions of Examples 18 to 20 are shown in Table-7.
The MSR used is the product name SSR-6600W of Sanei Chemical Co., Ltd.

  Creation of evaluation equipment when using light and shade film.

Outline of creation of evaluation equipment of Example Substrate ⇒ Surface conditioning and drying ⇒ Colored ink application ⇒ Dry A ⇒ Application of MSR ⇒ Dry B ⇒ Dark film set ⇒ Exposure ⇒ Development (30 ° C, 0.25 MPa, 1 of effective chamber length) Adjust speed so that development can be performed at 1/2) ⇒ Dry (50 minutes / 150 ° C) ⇒ Evaluation

The working conditions of Examples 21 to 24 are shown in Table-8.
The MSR used is the product name SSR-6600W of Sanei Chemical Co., Ltd.

The working conditions of Comparative Examples 6-7 are shown in Table-9.
SR used is the product name Photofiner PSR-4000 CC02 / CA-40 of Taiyo Ink Manufacturing Co., Ltd.

  In the evaluation method, characters such as identification characters / symbols are clearly readable, readable, unclear, but not readable on the circuit board after MSR and SR processing in the brightness of the office. The stage was evaluated visually.

  The evaluation results are shown in Table-10.

(1) Substrate (2) Circuit (3) Colored ink layer (4) MSR layer (5) Solder resist photomask (6) Character photomask (7) Photomask with density difference (8) Composite photo mask

Claims (8)

  The circuit board is mixed with an epoxy resin and a partially carboxylic acid remaining acrylic resin, or a solder resist ink with a partially carboxylic acid remaining acrylic resin added to the epoxy resin and applied with ultraviolet light. By changing the amount, changing the refractive index and transparency of the solder resist ink layer, the difference in refractive index and transparency makes it possible to visually identify the identification characters and symbols of mounted parts etc. with the background color. Circuit board manufacturing method.   A colored ink having a functional group is provided as a primer layer between the circuit board and the solder resist ink coating layer. The method for manufacturing a circuit board according to claim 1, wherein the thickness is 2 μm to 300 μm.   A colored ink layer having a functional group is provided between the solder resist ink layer and the solder resist ink layer. The method for manufacturing a circuit board according to claim 1, wherein the thickness is 2 μm to 300 μm.   Perform the primary exposure using the solder resist mask film, and then perform the secondary exposure by overlaying the solder resist mask film and the character / symbol mask film, or reverse the exposure order and perform irradiation. The method for manufacturing a circuit board according to claim 1, wherein the amount is changed.   Solder resist part and character / symbol part are synthesized on the same film, then primary exposure is performed using a mask film, and then secondary exposure is performed with a mask film for solder resist, or this exposure order is reversed. The method for manufacturing a circuit board according to claim 1, wherein the irradiation amount is changed.   4. The method of manufacturing a circuit board according to claim 1, wherein the mask film is light and shaded so that a difference in the amount of transmitted ultraviolet rays can be generated in the image line portion of the mask film.   By changing the amount of drying heat, changing the refractive index and transparency of the solder resist ink layer, and by the difference in the refractive index and transparency, the identification characters of mounted parts etc. can be visually recognized with the background color, Item 6. A method for manufacturing a circuit board according to Item 1-5.   8. The method of manufacturing a circuit board according to claim 1, wherein an identification character / symbol such as a mounted component is not added on the surface of the solder resist ink layer.

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