JP2015226050A - Method for manufacturing printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a printed circuit board.SOLUTION: The method for manufacturing a printed circuit board of the present invention aims to improve an undercut defect due to an uncured solder resist layer, and the method includes steps of: forming a circuit pattern on a substrate; forming a first solder resist layer by using a photocurable resin on the substrate where the circuit pattern is formed; exposing the first solder resist layer by using a first mask to form a cured region and an uncured region; forming a second solder resist layer on the first solder resist layer by using a photocurable resin; exposing the second solder resist layer by using a second mask to cure a dam-forming part; increasing the height of the dam-forming part by repeating once or more the steps of forming the second solder resist layer and curing the dam-forming part; and developing the substrate where formation and exposure of the solder resist layer are repeated, so as to remove an uncured solder resist layer.

Description

  The present invention relates to a method for manufacturing a printed circuit board, and more particularly to a method for manufacturing a printed circuit board that can prevent an undercut defect of a solder resist layer.

  In recent years, semiconductor packaging technology tends to be miniaturized, thinned, and multifunctional. According to this trend, FCCSP (Flip Chip Chip Scale Package) for package-on-package (PoP) is currently mass-produced, and in printed circuit board (PCB), two steps (2-step) The solder resist (SR) structure is often used.

  Usually, in a two-step solder resist structure, a thin solder resist is formed in a flip chip (FC) region, and a thick solder resist is formed in a PoP (Package on Package) top ball (top ball) region. Is common. In the 2-step solder resist, when the chip is bonded to the flip chip area, the solder resist in the outer PoP topball area acts as an underfill barrier, or the solder resist in the PoP topball area is relatively Therefore, the bumps in the PoP topball region are prevented from being bridged with each other, thereby reducing the pitch. Therefore, in recent years, in order to further reduce the bump pitch in the PoP topball region, it is further required to increase the thickness of the solder resist in the PoP topball region.

  Thus, in order to increase the thickness of the solder resist in the PoP topball region, a solder resist process of two steps or more is performed. When the solder resist is formed to a thickness of 25 to 40 μm, a two-step solder resist opening forming step can be performed. However, in order to form a solder resist of 40 μm or more, it is necessary to coat the solder resist of three steps or more. Conventionally, after first coating with a solder resist, the exposure was performed, and then the second and third coatings with the solder resist were performed. In this case, it is necessary to expose and cure the solder resist layer that has been laminated and thickened in two or more layers in the second exposure step. However, since the thickness of the solder resist is too thick compared to the transmittance of UV, the lower portion of the solder resist is not sufficiently cured by UV. Therefore, in the subsequent development process, the lower region of the uncured solder resist is etched by the etchant, and an undercut (FIG. 1a) defect occurs. In particular, such defects are more serious as the thickness of the solder resist increases.

Korean open patent 2011-0020542

  Accordingly, the present invention has been made to solve the above-described problems in the conventional printed circuit board, and undercuts during the development process for forming the solder resist opening of the printed circuit board. It is an object of the present invention to provide a printed circuit board that can eliminate defects.

  In order to effectively achieve the above object, according to the present invention, a step of forming a circuit pattern on a substrate, and a first solder using a photocurable resin on the substrate on which the circuit pattern is formed. Forming a resist layer; exposing the first solder resist layer using a first mask to form a cured region and an uncured region; and a photocurable resin on the first solder resist layer. Forming a second solder resist layer using, exposing the second solder resist layer using a second mask to cure a dam forming portion, and forming the second solder resist layer The step of forming and repeating the step of curing the dam formation part at least once, increasing the height of the dam formation part, and developing the substrate on which the formation and exposure of the solder resist layer are repeated, Method of manufacturing a printed circuit board comprising the steps of removing the solder resist layer of curing, is provided.

  The dam forming portion may be formed in a PoP (Package on Package) top ball region, and the first solder resist layer may be formed using a liquid photocurable resin.

  Other solder resist layers other than the first solder resist layer can be formed using a solid photocurable resin film, and the outer layer circuit is formed before the step of forming the first solder resist layer. The method may further include pre-treating the substrate having the solder resist.

  The step of forming the cured region and the uncured region by the exposure can be performed by UV-DI (UV Direct Imaging) instead of the first mask, and the dam forming unit is exposed by using the second mask. The step of curing can also be performed by UV-DI (UV Direct Imaging).

  The method may further include performing a post-curing process on the printed circuit board after the developing the substrate.

  The method of manufacturing a printed circuit board according to the present invention can prevent undercut failure when forming a thick solder resist that requires a three-step or more solder resist coating, and has improved reliability. A printed circuit board can be provided.

It is sectional drawing of the state which the undercut (undercut) defect generate | occur | produced with the formation method of the conventional soldering resist. It is sectional drawing of the printed circuit board by the formation method of the soldering resist layer by one form of this invention. It is sectional drawing which showed the state in which the circuit pattern was formed on the board | substrate during the formation process of the soldering resist layer by one form of this invention. It is sectional drawing after forming a 1st soldering resist layer in the formation process of the soldering resist layer by one form of this invention. It is sectional drawing which showed the process of developing a 1st soldering resist layer during the formation process of the soldering resist layer by one form of this invention. It is sectional drawing after forming the 2nd soldering resist layer in the formation process of the soldering resist layer by one form of this invention. It is sectional drawing which showed the process of developing a 2nd soldering resist layer in the formation process of the soldering resist layer by one form of this invention. It is sectional drawing after forming a 3rd soldering resist layer in the formation process of the soldering resist layer by one form of this invention. It is sectional drawing which showed the process of developing a 3rd soldering resist layer in the formation process of the soldering resist layer by one form of this invention. It is sectional drawing after forming a 4th soldering resist layer in the formation process of the soldering resist layer by one form of this invention. It is sectional drawing which showed the process of developing a 4th soldering resist layer in the formation process of the soldering resist layer by one form of this invention. FIG. 4 is a cross-sectional view of a printed circuit board that has been developed during a solder resist layer forming process according to an embodiment of the present invention.

  The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the invention. As used herein, the singular forms may include the plural unless the context clearly dictates otherwise. Also, as used herein, “comprise” and / or “comprising” includes the stated shapes, numbers, steps, actions, members, elements, and / or combinations thereof. It does not exclude the presence or addition of one or more other shapes, numbers, steps, actions, members, elements, and / or combinations thereof.

  Objects, specific advantages and novel features of the present invention will become more apparent from the accompanying drawings and the following detailed description and preferred embodiments. In this specification, it should be noted that when adding reference numerals to the components of each drawing, the same components are given the same number as much as possible even if they are shown in different drawings. I must. Further, in describing the present invention, when it is determined that a specific description of the related art related to the present invention may obscure the gist of the present invention, a detailed description thereof will be omitted. In this specification, terms such as “first” and “second” are used to distinguish one component from other components, and the component is not limited by the terms.

  Hereinafter, the present invention made to improve an undercut defect which has been a problem of a conventional solder resist layer forming method will be described in detail with reference to the accompanying drawings.

  2A to 2J are cross-sectional views illustrating a process of manufacturing a printed circuit board according to an embodiment of the present invention.

  In order to manufacture the printed circuit board 100 according to an embodiment of the present invention, first, the circuit pattern 20 is formed on the substrate with a conductive material (FIG. 2a). At this time, the circuit pattern 20 formed on the substrate can be made of metal. The substrate may include a flip chip area 80 where a flip chip is mounted, and a PoP (Package on Package) top ball area 70 for package on package mounting. it can.

  At this time, since the thickness of the solder resist layer in the flip chip region 80 is not thick, even when the step of forming the solder resist opening 50 by the conventional method as described above is performed, the solder resist layer is exposed during the exposure step. Undercut defects due to uncured material will not occur. However, the PoP topball region 70 having a relatively thick solder resist is not cured in the lower region of the solder resist layer when the conventional method is used when three or more solder resists must be formed. The uncured solder resist layer may be etched during the subsequent development process, resulting in undercut defects (FIG. 1a). In order to prevent the defect, according to one aspect of the present invention, the defect due to the uncured solder resist can be prevented by performing the exposure process each time each solder resist layer is formed. (Fig. 1b)

  Thereafter, the first solder resist layer 31 may be formed on the substrate on which the circuit pattern 20 of the conductive material is formed using a photocurable resin (FIG. 2b).

  At this time, the solder resist layer is formed by a screen printing method, a roller coating method, a curtain coating method, a spray coating method, a solder resist film lamination method, or the like. However, it is not limited to this.

  The screen printing method is a method in which a solder resist pattern is directly printed using plate making. In this case, exposure and development are unnecessary, and curing can be performed directly. The roller coating method is a method in which a photocurable resin having a lower viscosity than that used in the screen printing method is thinly applied to a roller made of a material such as rubber and coated on a substrate. However, this method makes it difficult to adjust the thickness of the solder resist layer to be coated according to the substrate, and it is difficult to form a uniform coating layer. The curtain coating method uses a photo-curing resin having a lower viscosity than that used in the roller coating method, and passes the substrate under the slit while taking out the photo-curing resin through a slit (not shown). In this method, the solder resist layer is coated. This method gives very uniform coating quality and can be applied regardless of the size of the substrate. The spray coating method is a method of coating by spraying a photocurable resin ink, and has an advantage that the thickness of the solder resist layer can be easily adjusted.

  Thereafter, the first solder resist layer 31 may be subjected to a primary exposure process (FIG. 2 c) using the first mask 60.

  At this time, the region to be removed in the subsequent development process blocks the light so as not to be irradiated with UV by the non-transparent region 61 of the first mask 60, thereby forming an uncured solder resist layer (FIGS. 2c and 31). The regions (FIGS. 2c, 41, and 46) that remain so that they remain without being removed even after the development process and serve as the protective film of the printed circuit pattern (FIGS. 2c, 41, and 46) pass through the transmission region 62 of the first mask 60. UV can be irradiated and cured. The solder resist layer (FIGS. 2c, 41, and 46) cured through the primary exposure process remains in the printed circuit board without being removed in the subsequent development process, and serves as a protective layer for the printed circuit pattern. can do. This primary exposure process can also be performed by a UV-DI (UV-Direct Imaging) method without using the first mask. That is, a method may be used in which a specific region is cured by directly irradiating UV onto a desired region of the solder resist layer without using a mask.

  After performing the primary exposure step, the second solder resist layer 32 can be formed on the first solder resist layer using a photocurable resin (FIG. 2d). As described above, the second solder resist layer 32 can also be formed by a screen printing method, a roller coating method, a curtain coating method, a spray coating method, a solder resist film lamination method, or the like, but is not limited thereto. is not.

  Thereafter, a secondary exposure process (FIG. 2 e) can be performed on the second solder resist layer 32 using the second mask 65. At this time, the region (FIGS. 2e and 42) where the dam (dam, FIG. 2J and 40) of the PoP topball region is to be formed is exposed to UV through the transmission region (FIGS. 2e and 67) of the second mask. The regions (FIGS. 2e, 32) that can be cured by subsequent development steps are not exposed to UV by the opaque regions (FIGS. 2e, 66) of the second mask (FIGS. 2e, 65). The light can be blocked to remain as an uncured solder resist layer (FIGS. 2e, 32).

  As described above, the solder resist layer (FIGS. 2e and 42) cured through the secondary exposure process remains on the printed circuit board without being removed in the subsequent development process, and the dam (FIG. 2j 40). This secondary exposure process can also be performed by a UV-DI (UV-Direct Imaging) method without using the second mask. That is, a method may be used in which a specific region is cured by directly irradiating UV onto a desired region of the solder resist layer without using a mask.

  After performing to a secondary exposure process, a 3rd soldering resist layer can be formed on a said 2nd soldering resist layer using a photocurable resin (FIG. 2f, 33). As described above, the third solder resist layer can also be formed by a screen printing method, a roller coating method, a curtain coating method, a spray coating method, or the like, but is not limited thereto.

  Thereafter, a third exposure step (FIG. 2g) can be performed on the third solder resist layer (FIGS. 2f and 33) using the same second mask 65 as that used in the secondary exposure step. The region (FIGS. 2g, 43) where the dam (FIGS. 2j, 40) in the PoP topball region is to be formed is exposed to UV through the transmission region (FIGS. 2g, 67) of the second mask and cured. An area to be removed in a subsequent development step is an uncured solder by blocking light so that UV is not irradiated by the non-transmissive area (FIGS. 2g and 66) of the second mask (FIGS. 2g and 65). It can be left as a resist layer (FIGS. 2g, 33). Thus, the solder resist layer (FIGS. 2g and 43) cured through the third exposure process remains on the printed circuit board without being removed in the subsequent development process, and serves as a protective layer for the printed circuit pattern. be able to. This tertiary exposure process can also be performed by a UV-DI (UV-Direct Imaging) method without using the second mask. That is, a method may be used in which a specific region is cured by directly irradiating UV onto a desired region of the solder resist layer without using a mask.

  The reason for forming the second solder resist layer and the third solder resist layer is to increase the thickness of the solder resist in the PoP topball region 70. By performing the exposure process every time each solder resist layer is formed as in this embodiment, undercut defects due to uncured portions below the solder resist layer can be prevented. Further, since the thick solder resist layer forms a high dam around the pad exposed portion 50 in the PoP topball region 70, it is possible to prevent the bumps from being energized with each other. Thus, a printed circuit board having a fine pitch can be manufactured.

  If a solder resist layer thicker than the thickness of the solder resist layer by the third solder resist layer is necessary, the fourth solder resist layer and the third solder resist layer are formed by the same method as the formation and exposure steps of the fourth solder resist layer. A solder resist layer (FIGS. 2h and 34) can be formed and exposed (FIG. 2i). If necessary, a further solder resist layer may be formed and exposed.

  After all the solder resist layers are formed and exposed, the uncured solder resist can be removed by a development process. The developed printed circuit board (FIG. 2j) may be provided with a PoP topball area dam (FIG. 2j, 40) having a relatively high solder resist layer. The development step can be performed by a method of applying a sodium carbonate aqueous solution, a potassium carbonate aqueous solution, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, or the like by a spray method, but is not limited to the aqueous solution, There may be various other methods that can be used.

If necessary, a post-cure process may be performed on the printed circuit board after the development process is completed. The post-cure process can consist of a photocuring process using energy of 1,000 to 3,000 mJ / cm ² and a thermosetting process performed at a temperature of 150 to 180 ° C. for about 1 to 3 hours.

  Another embodiment according to the present invention will be described in detail with reference to FIGS. 2a to 2j. However, the same contents as those described above may be omitted for a clear explanation of the invention.

  First, a circuit pattern 20 is formed on a substrate with a conductive material (FIG. 2a). The circuit pattern 20 formed on the substrate can be made of metal. The substrate may have a flip chip area 80 where a flip chip is mounted and a PoP topball area 70 for package on package mounting.

  Thereafter, the first solder resist layer 31 can be formed on the substrate on which the circuit pattern 20 of the conductive material is formed using a liquid photocurable resin. By using a liquid photocurable resin, a screen printing method, a roller coating method, a curtain coating method, and a spray coating method can be applied, but the present invention is not limited thereto.

  At this time, the reason for forming the first solder resist layer using the liquid photocurable resin is that the lower region coated with the solder resist layer is a prepreg or an ABF film. This is because the photocurable resin has good wettability with the lower region. Further, since the circuit pattern 20 is formed on the substrate 10 and has a step, it is advantageous in that the step can be easily filled with a liquid solder resist.

  Thereafter, a primary exposure process (FIG. 2 c) can be performed on the first solder resist layer 31 using the first mask 60.

  At this time, the region to be removed in the subsequent development process blocks the light so as not to be irradiated with UV by the non-transparent region 61 of the first mask 60, thereby forming an uncured solder resist layer (FIGS. 2c and 31). The regions (FIGS. 2c, 41, and 46) that remain so that they remain without being removed even after the development process and serve as the protective film of the printed circuit pattern (FIGS. 2c, 41, and 46) pass through the transmission region 62 of the first mask 60. UV can be irradiated and cured. Thus, the solder resist layer (FIGS. 2c, 41, and 46) cured through the primary exposure process remains on the printed circuit board without being removed in the subsequent development process, and serves as a protective layer for the printed circuit pattern. Can do. This primary exposure process can also be performed by a UV-DI (UV-Direct Imaging) method without using the first mask. That is, a method may be used in which a specific region is cured by directly irradiating UV onto a desired region of the solder resist layer without using a mask.

  After performing a primary exposure process, the 2nd soldering resist layer 32 can be formed on the 1st soldering resist layer 31 using a solid-state photocurable resin film (FIG. 2d). At this time, it is preferable to use a solder resist film laminating method or the like in view of the characteristics of the solid photocurable resin film, but it is not limited thereto.

  At this time, the reason for using the solid photocurable resin film is that, in the case of the substrate on which the liquid first solder resist layer is formed, the step of the circuit pattern layer is formed by using the liquid photocurable resin. This is because the use of a solid photocurable resin film in the form of a dry film is advantageous in the manufacturing process because it is flattened by the resist layer.

  Thereafter, a secondary exposure process (FIG. 2 e) can be performed on the second solder resist layer 32 using the second mask 65. At this time, the region where the dam (FIGS. 2j and 40) of the PoP topball region is to be formed is cured through the transmission region (FIGS. 2e and 67) of the second mask and removed in the subsequent development process. The region remains as an uncured solder resist layer (FIGS. 2e and 32) by blocking light so that UV is not irradiated by the opaque regions (FIGS. 2e and 66) of the second mask (FIGS. 2e and 65). Can be.

  The solder resist layer (FIGS. 2e and 42) cured through the secondary exposure process in this manner remains on the printed circuit board without being removed in the subsequent development process, so that the dam (FIGS. 2j and 40 in the PoP topball region) is left. ) Can be. This secondary exposure process can also be performed by a UV-DI (UV-Direct Imaging) method without using the second mask. That is, a method may be used in which a specific region is cured by directly irradiating UV onto a desired region of the solder resist layer without using a mask.

  Thereafter, the formation and exposure of the third solder resist layer can be repeated in the same manner as the formation and exposure of the second solder resist layer. If necessary, the formation and exposure of further solder resist layers can be repeated. May be repeated.

  After all the solder resist layers are thus formed and exposed, the uncured solder resist can be removed by a development process. The developed printed circuit board (FIG. 2j) may be provided with a PoP topball area dam (FIG. 2j, 40) having a relatively high solder resist layer. The development step can be performed by a method of applying a sodium carbonate aqueous solution, a potassium carbonate aqueous solution, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, or the like by a spray method, but is not limited to the aqueous solution, In addition, various methods that can be used may be used.

If necessary, a post-cure process can be performed on the printed circuit board on which the development process has been completed. The post-cure process can consist of a photocuring process using energy of 1,000 to 3,000 mJ / cm ² and a thermosetting process performed at a temperature of 150 to 180 ° C. for about 1 to 3 hours.

Comparative example (conventional method)
A copper clad laminate was prepared, and a 23 μm solder resist layer was coated three times to form a total of 69 μm solder resist layer. Next, after performing the exposure process once, it developed. Then, the depth (FIG. 1a, A) of the soldering resist wall surface eroded by the undercut was measured using the VSEM photograph.

Example A copper-clad laminate was prepared and coated with a 23 μm solder resist layer, followed by an exposure step. The above process was repeated twice to form a solder resist layer having a total thickness of 69 μm, and then developed with a 1% aqueous solution of sodium carbonate for 60 seconds. Then, the depth (FIG. 1a, A) of the soldering resist wall surface eroded by the undercut was measured using the VSEM photograph.

  As shown in Table 1, it can be seen that the solder resist layer according to the embodiment of the present invention has a greatly reduced amount of erosion of the solder resist wall surface due to undercut as compared with the solder resist layer according to the conventional method.

DESCRIPTION OF SYMBOLS 10 Board | substrate 20 Circuit pattern layer 31 1st soldering resist layer 32 2nd soldering resist layer 33 3rd soldering resist layer 34 4th soldering resist layer 40 Solder resist dam of PoP topball area | region 41 1st hardening soldering resist layer 42 2nd hardening Solder resist layer 43 Third cured solder resist layer 44 Fourth cured solder resist layer 46 Flip chip region cured solder resist layer 50 Solder resist opening 60 First mask 61 First mask non-transparent region 62 First mask transmission region 65 Second mask 66 Non-transparent area of second mask 67 Transparent area of second mask 70 PoP top ball area 80 Flip chip area 100 Printed circuit board

Claims (9)

Forming a circuit pattern on the substrate;
Forming a first solder resist layer on the substrate on which the circuit pattern is formed using a photocurable resin;
Exposing the first solder resist layer using a first mask to form a cured region and an uncured region;
Forming a second solder resist layer on the first solder resist layer using a photocurable resin;
Exposing the second solder resist layer using a second mask to cure a dam forming portion;
Repeating the step of forming the second solder resist layer and the step of curing the dam formation portion one or more times to increase the height of the dam formation portion;
Developing the substrate on which the formation and exposure of the solder resist layer are repeated, and removing the uncured solder resist layer.   2. The method of manufacturing a printed circuit board according to claim 1, wherein the dam forming portion is formed in a PoP (Package on Package) top ball region.   2. The method of manufacturing a printed circuit board according to claim 1, wherein the first solder resist layer and the solder resist layer other than the first solder resist layer are formed using photo-curing resins of different materials. .   The printed circuit board manufacturing method according to claim 1, wherein the first solder resist layer is formed using a liquid photocurable resin.   The method for producing a printed circuit board according to claim 1, wherein the solder resist layer other than the first solder resist layer is formed using a solid photocurable resin film.   The method of claim 1, further comprising pre-treating a substrate having the outer layer circuit with a solder resist before the first solder resist layer is formed.   2. The method of manufacturing a printed circuit board according to claim 1, wherein the step of forming a cured region and an uncured region by performing the exposure is performed by UV-DI (UV Direct Imaging) instead of the first mask.   The method of manufacturing a printed circuit board according to claim 1, wherein the step of exposing and curing the dam forming portion is performed by UV-DI (UV Direct Imaging) instead of the second mask.   The method of claim 1, further comprising performing a post-curing process on the printed circuit board after the developing the substrate.

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