JP2016157840A - Method for manufacturing printed-wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed-wiring board with a low possibility of short-circuit occurrence between mutually adjacent pads and between a pad and a wiring.SOLUTION: A method for manufacturing a printed-wiring board comprising a base insulation layer 1 composed of an insulation material, a conductor layer 2 including a pad 2a and a wiring, and a solder resist layer 4, includes: a solder resist laminating step of covering the base insulation layer and the conductor layer by an uncured solder resist layer composed of a photocurable resin; an exposing step of curing a portion not covered by a mask of a solder resist layer by exposing the solder resist layer in a state in which the position of the solder resist layer corresponding to the position of the pad of the conductor layer is covered by a mask 5; a heat treatment step of temporarily curing the exposed solder resist layer by heating; a developing step of forming an opening 6 in the solder resist layer by developing the temporarily cured solder resist layer; and a heating step of fully curing the developed solder resist layer.SELECTED DRAWING: Figure 4

Description

  The present invention includes a base insulating layer made of an insulating material, a conductor layer formed on the base insulating layer, including a pad and a wiring, and the base insulating layer and the pad formed on the conductor layer. And a solder resist layer having an opening in the printed wiring board.

  Conventionally, a method for manufacturing a printed wiring board as described above is known from Patent Document 1, for example. FIG. 6 is a flowchart for explaining each step of the formation process of the solder resist layer in the conventional printed wiring board manufacturing method described in Patent Document 1.

  In the formation process of the solder resist layer shown in FIG. 6, first, a photocurable resin for forming a solder resist layer is applied on the base insulating layer and the conductor layer including the pads and wirings thereon, and the uncured resin is formed. An SR laminating step S1 for forming a solder resist (hereinafter also referred to as “SR”) layer is performed, and then the solder resist layer in a state where the position of the solder resist layer corresponding to the position of the pad of the conductor layer is covered with a mask Then, an exposure step S2 is performed in which the portion of the solder resist layer that is not covered with the mask is cured. Next, a development process is performed in which an uncured portion of the solder resist layer after exposure is removed by development to form an opening, and finally, a heating process S4 is performed in which the solder resist layer after development is further cured by heating. Thus, a solder resist layer having a predetermined opening is formed on the pad of the conductor layer.

JP-A-9-051156

  In the conventional method for manufacturing a printed wiring board described above, in the process of forming a solder resist layer having an opening on the pad of the conductor layer, the light is exposed particularly among the incompletely exposed portions of the inner wall of the opening that is exposed with the leakage light around the mask. A deep portion having a low curing degree is dissolved during development, and an undercut that exposes the edge of the pad on the inner wall of the opening of the solder resist layer is likely to occur. When such an undercut occurs, a short circuit may occur between adjacent pads and between the pad and the wiring.

  An object of the present invention is to provide a printed wiring board that is less likely to cause a short circuit between adjacent pads and between a pad and a wiring by suppressing the occurrence of an undercut of a solder resist layer. That is.

  The printed wiring board manufacturing method of the present invention includes a base insulating layer made of an insulating material, a conductor layer including pads and wiring formed on the base insulating layer, the base insulating layer, and the conductor layer. A solder resist layer having an opening on the pad, wherein the base insulating layer and the conductor layer are covered with an uncured solder resist layer made of a photocurable resin. Resist laminating step, exposing the solder resist layer in a state where the position of the solder resist layer corresponding to the position of the pad of the conductor layer is covered with a mask, and a portion of the solder resist layer not covered with the mask An exposure step for curing, a heat treatment step for heating and temporarily curing the solder resist layer after the exposure, and a solder after the temporary curing. A developing step of forming the opening in the solder resist layer by developing the resist layer, characterized in that it comprises a heating step of curing the solder resist layer after the development.

  In the manufacturing method of the printed wiring board of this invention, it is preferable that the conditions of the heat processing in a heat processing process are the heating for 10 to 30 minutes at the temperature of 80-120 degreeC. The pitch between adjacent pads is preferably 100 to 150 μm, and the pitch between adjacent pads and wiring is preferably 10 to 50 μm. Furthermore, it is preferable that the solder resist layer contains 15 to 35 mass% of an inorganic filler. Furthermore, it is preferable to irradiate the solder resist layer with ultraviolet rays including all of I-line, H-line and G-line in the exposure step.

  According to the present invention, a base insulating layer made of an insulating material, a conductor layer including pads and wiring formed on the base insulating layer, and formed on the base insulating layer and the conductor layer, In a method of manufacturing a printed wiring board comprising a solder resist layer having an opening on a pad, a heat treatment step is performed after the exposure step and before the development step when the solder resist layer having the opening is formed from a photocurable resin. By carrying out, the incompletely exposed part of the solder resist layer is semi-cured and the unexposed part remains uncured. Therefore, in the development process after the heat treatment process, the semi-cured incompletely exposed part is not removed, but only the unexposed part is removed, and the occurrence of undercut on the inner wall of the opening of the solder resist layer is suppressed. As a result, it is possible to obtain a printed wiring board that is less likely to cause a short circuit between adjacent pads of the conductor layer and between the pads and the wiring than in the prior art.

(A), (B) is a figure for demonstrating the problem which generate | occur | produces in the formation process of the soldering resist layer in the manufacturing method of the conventional printed wiring board, respectively. It is a figure for demonstrating the problem of the printed wiring board resulting from the problem in the formation process of the soldering resist layer in the manufacturing method of the conventional printed wiring board. It is a flowchart for demonstrating each process of the formation process of the soldering resist layer in the manufacturing method of the printed wiring board of one Embodiment of this invention. (A)-(E) are sectional drawings for demonstrating each process of the formation process of the soldering resist layer in the manufacturing method of the printed wiring board of the said embodiment. It is a figure for demonstrating an example of the printed wiring board manufactured with the manufacturing method of the printed wiring board of the said embodiment. It is a flowchart for demonstrating each process of the formation process of the soldering resist layer in the manufacturing method of the conventional printed wiring board.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, a printed wiring board manufacturing method of the present invention will be described with reference to the drawings. First, referring to FIGS. 1A, 1B, and 2, a solder in a conventional printed wiring board manufacturing method will be described. The problem of the printed wiring board resulting from the problem relating to the formation of the resist layer will be described, and then with reference to FIGS. 3, 4A to 5E, and FIG. 5, the printed wiring according to one embodiment of the present invention A method for manufacturing the plate will be described.

  In the method described in Patent Document 1 described above, a completely exposed portion (cured portion) in which ultraviolet rays are sufficiently irradiated to the solder resist layer by exposure using an uncured solder resist layer mask, and a mask As well as an unexposed portion (uncured portion) that is covered with UV rays and is not irradiated with ultraviolet rays, an incompletely exposed portion (semi-cured portion) slightly cured by leakage light (leaked ultraviolet light) around the mask is generated. Here, as shown in FIG. 1A, when the solder resist layer 55 is exposed in a state where the alignment between the mask 51 and the pad 53 of the printed wiring board 52 is shifted, the incompletely exposed portion 54 that is semi-cured by the leaked light. Is formed not only on the pad 53 but also outside the pad 53. And in the incompletely exposed portion 54, the deep portion having a low photocuring degree because it is difficult for ultraviolet rays to reach is dissolved in the developing solution at the time of development. As shown in FIG. 1B, the inner wall of the opening 56 of the solder resist layer 55 is formed. The undercut 57 that exposes the edge of the pad 53 is easily formed.

  However, in the conventional printed wiring board, the distance between the edges of the nearest pads 53 or between the edge of the pads 53 and the wiring 58 is relatively wide, 150 μm or more. Therefore, when the opening 56 is opened at the position of the solder resist layer 55 corresponding to the pad 53, even if the undercut 57 occurs in the opening 56, the electrical connection between the pads 53 or between the pad 53 and the wiring 58 is performed. No peeling of the solder resist layer 55 leading to the connection occurred. As a result, in the conventional printed wiring board, there was no short circuit between the pads or between the pads and the wiring due to the undercut 57 of the solder resist layer 55.

  On the other hand, with recent miniaturization of semiconductor products, the demand for so-called narrow pitches for narrowing the pitch between pads and between pads and wiring has increased. Therefore, as shown in FIG. 2, the plating solution soaks into the undercut 57 of the solder resist layer 55, which has not been a problem with the conventional printed wiring board, when plating the opening 56, and between the pad 53 and the wiring 58. There was a problem that a short circuit occurred. Further, the same short-circuit problem occurred between the pads 53 depending on the wiring pattern. The method for manufacturing a printed wiring board of the present invention reduces or eliminates the problem of undercutting of the solder resist layer.

  FIG. 3 is a flowchart for explaining each step of a solder resist layer forming process in the method for manufacturing a printed wiring board according to the embodiment of the present invention. In the printed wiring board manufacturing method of this embodiment, the solder resist forming process is performed on the base insulating layer and the conductor layer including the pads and wirings on the base insulating layer in the same manner as the normal solder resist forming process. SR laminating step S1 of applying a photocurable resin for layer formation or laminating a photocurable resin film for forming a solder resist layer to form an uncured solder resist (hereinafter also referred to as “SR”) layer. And exposing the solder resist layer in a state where the position of the solder resist layer corresponding to the position of the pad of the conductor layer is covered with a mask, and curing the exposed portion not covered with the mask of the solder resist layer, A development step S3 that removes an uncured portion of the solder resist layer after exposure by development to form an opening, and a solder layer after development. A heating step S4 for further curing the strike layer by heating to form a solder resist layer having a predetermined opening on the pad of the conductor layer, and further, between the exposure step S2 and the development step S3. In addition, a heat treatment step S2-2 for heating and temporarily curing the exposed solder resist layer is provided.

  4A to 4E are cross-sectional views for explaining each process of the solder resist layer forming process in the method for manufacturing a printed wiring board according to the embodiment. Hereinafter, each process of the formation process of the solder resist in the manufacturing method of the printed wiring board of this embodiment is demonstrated according to FIG. 4 (A)-(E). First, as shown in FIG. 4A, an intermediate substrate 3 is prepared by forming a conductor layer 2 including pads and wirings on a base insulating layer 1 made of an insulating material. For example, the SR laminating step S1 is performed in which a photocurable resin film for forming a solder resist layer is laminated to form an uncured solder resist layer 4.

  In the example shown in FIG. 4A, the base insulating layer 1 is formed of a resin such as epoxy or ceramic, for example. The conductor layer 2 is formed by, for example, an additive method, a semi-additive method, a subtractive method, or the like. The conductor layer 2 is made of, for example, copper. The conductor layer 2 includes a plurality of pads 2a for mounting electronic components such as semiconductor elements, and wirings (not shown) such as signal lines and power supplies. As will be apparent from the examples described later, in applying the method of the present embodiment, the pitch between the pads 2a is 100 to 150 μm, and between the edges of the pads 2a and the edges of the pads 2a The distance between the wiring is preferably 10 to 50 μm.

  As a photocurable resin film for forming the solder resist layer 4, a commercially available film can be used. For example, a photosensitive and sheet-like dry film (manufactured by DuPont, trade name “RISTON (thickness: 38 μm)) ”, Trade name“ PFR-800 AUS 410 (thickness: 25 μm) ”manufactured by Taiyo Ink Manufacturing Co., Ltd., trade name“ NIT215 (thickness: 15 μm) ”manufactured by Nichigo Morton, etc.) can be selected. . In addition, when the method of this embodiment is applied so that it may become clear from the Example mentioned later, it is preferable that the soldering resist layer 4 mentioned above contains 15-35 mass% of inorganic fillers.

  Next, as shown in FIG. 4B, on the uncured solder resist layer 4 to be opened, positions corresponding to the positions of the pads 2a of the conductor layer 2 of the intermediate substrate 3 of the solder resist layer 4 are formed. The mask 5 to cover is arrange | positioned, and the exposure process S2 which irradiates an ultraviolet-ray from the upper direction of the mask 5, and hardens the exposed part of the soldering resist layer 4 is implemented. As the mask 5 used in the exposure step S2, for example, a mask formed by a conventional method such as etching processing, additive processing, laser processing, or the like from a commercially available known mask material can be used. As the mask material, for example, a metal mask made of a metal such as a nickel alloy or a nickel-cobalt alloy, or a plastic mask made of a resin such as an epoxy resin or a polyimide resin can be used. As will be apparent from the examples described later, in applying this embodiment, the solder resist layer 4 may be irradiated with ultraviolet rays including all of the I-line, H-line, and G-line in this exposure step S2. preferable. Moreover, exposure by a direct drawing type exposure machine is also possible.

  Next, as shown in FIG. 4C, a heat treatment step S2-2 is performed in which the exposed solder resist layer 4 is heated to bring the incompletely exposed portion into a semi-cured state. The heat treatment here may be under any conditions as long as the incompletely exposed portion is semi-cured while the unexposed portion is not cured. Therefore, the temperature of the heat treatment is preferably lower than the temperature for finally curing the solder resist layer 4. As will be apparent from the examples described later, in applying this embodiment, it is preferable that the heat treatment conditions in the heat treatment step S2-2 be 10 to 30 minutes at a temperature of 80 to 120 ° C.

Next, as shown in FIG. 4D, a developing step S3 is performed in which an unexposed uncured portion generated in the solder resist layer 4 by the exposure through the mask 5 is removed using a developer. . Thereby, the opening 6 can be formed on the pad 2a. As a developing solution used here, a low-concentration alkaline aqueous solution can be used as conventionally known. Specifically, for example, 1 mass% to 3 mass% of sodium carbonate (Na ₂ CO ₃ ). Aqueous solution, potassium carbonate (K ₂ CO ₃ ) aqueous solution, sodium phosphate (Na ₂ PO ₃ ) aqueous solution, potassium phosphate (K ₃ PO ₃ ) aqueous solution, sodium acetate (CH ₂ COONa) aqueous solution, sodium nitrate (NaNO ₃ ) aqueous solution Etc. can be used.

  Finally, as shown in FIG. 4 (E), a heating step S4 for heating the solder resist layer 4 after development to be fully cured to form a solder resist layer 4 having a predetermined opening 6 on the intermediate substrate 3 is performed. carry out. In addition, the heating conditions according to the kind etc. of the soldering resist material conventionally used in order to fully cure a soldering resist layer can be used for the heating conditions for this heating process.

  According to the formation process of the solder resist layer in the manufacturing method of the printed wiring board of the embodiment described above, the heat treatment step S2-2 is performed after the exposure step S2 and before the development step S3. The incompletely exposed part is semi-cured and the unexposed part remains uncured. Therefore, in the development step S3 after the heat treatment step S2-2, the incompletely exposed portion is not removed, but only the unexposed portion is removed, and the occurrence of undercut on the solder resist layer 4 is suppressed. As a result, a printed wiring board having a lower possibility of occurrence of a short circuit between adjacent pads 2a of the conductor layer 2 and between the pads 2a and the wiring can be obtained.

  FIG. 5 is a diagram for explaining an example of a printed wiring board manufactured by the method for manufacturing a printed wiring board according to the above-described embodiment. In this figure, a printed wiring board with bumps is illustrated. The printed wiring board with bumps of the embodiment is formed on a base insulating layer 11 made of an insulating material, a conductor layer 12 including a plurality of pads 12a formed on the base insulating layer 11, and the base insulating layer 11. Each of the bumps 14 includes a solder resist layer 13 having a plurality of openings 13a for exposing the pads 12a and bumps 14 formed on the pads 12a exposed from the openings 13a. A plated metal layer 15 formed on the exposed conductor pad 12a, a solder layer 16 reflow-formed from the solder particles attached to the plated metal layer 15 via an adhesive layer and protruding from the upper surface of the solder resist layer 13, The plated metal layer 15 and the metal alloy layer 17 of the solder layer 16 generated between the plated metal layer 15 and the solder layer 16 by the reflow It is. The base insulating layer 1 may be a single layer as shown in the figure, but may have a laminated structure of a plurality of layers and a conductor layer 2 formed between these insulating layers.

<First embodiment>
First, an SR substrate process S1 is performed to form a copper wiring and a copper pad on one surface of an insulating substrate, and the pitch between the copper pad and the copper wiring is 20 μm, and the pitch between the copper pads is 100 μm. A photo-curable solder resist film containing 50 mass% of inorganic filler on the copper wiring and copper pad of the intermediate substrate (manufactured by Taiyo Ink Manufacturing Co., Ltd., trade name “PFR-800 AUS 410”, thickness 25 μm) ) Was applied to form an uncured solder resist layer. Next, an exposure step S2 is performed to cover the position of the solder resist layer where the opening corresponding to the copper pad is to be formed with a mask, and all of the I, H, and G lines are applied to the solder resist layer. Irradiation with ultraviolet rays (130 mJ). Next, heat treatment step S2-2 was performed, and the exposed solder resist layer was heat treated at 100 ° C. for 20 minutes. Next, development process S3 was implemented and the uncured part was removed by development using a 1 mass% sodium carbonate aqueous solution for the solder resist layer after the heat treatment. Finally, the heating step S4 was performed, and the solder resist layer having openings was heated at 180 ° C. for 40 minutes to be fully cured.

  In the first example, two printed circuit boards (1200 pieces / sheet) of the printed wiring board of the example manufactured based on the manufacturing method of the present embodiment by performing the above steps were prepared as a collective substrate before cutting. Moreover, among each process implemented with the manufacturing method of this embodiment, SR lamination process S1, exposure process S2, development process S3, and heating process S4 were implemented similarly, and the comparison manufactured without implementing heat treatment process S2-2 Two printed wiring boards of the example (1200 pieces / sheet) were prepared as a collective substrate before cutting.

  An energization test for energizing the copper wiring and the copper pad was performed on the prepared printed wiring boards of Examples and Comparative Examples to evaluate whether or not a short circuit occurred between the copper wiring and the copper pad. As a result, in the printed wiring board of the example, no short circuit occurred between the wiring and the pad. On the other hand, in the printed wiring board of the comparative example, a short circuit occurred in the printed wiring board of 156 pieces per collective board before cutting. From this, the usefulness of the manufacturing method of this embodiment which implements heat processing process S2-2 after exposure was able to be confirmed.

<Second embodiment>
In order to obtain a suitable example of the heat treatment conditions in the heat treatment step S2-2 for the printed wiring board of the embodiment in the first embodiment, the heat treatment temperature S2 is changed by changing the temperature and time of the heat treatment as shown in Table 1 below. 2 and the other steps are carried out in the same manner as in the first example, and each of the printed wiring boards of Examples 1 to 6 and Reference Examples 1 to 4 is used as a collective substrate before cutting (1200 pieces / Prepared). An energization test was performed on the prepared printed wiring board in the same manner as in the first example. The results are shown in Table 1 below.

  From the results in Table 1, it was found that the heat treatment conditions in the heat treatment step S2-2 are preferably heat treatment at a temperature of 80 to 120 ° C. for 10 to 30 minutes.

<Third embodiment>
In order to obtain preferred examples of the distance between the edge of the nearest pad and the wiring and between the edges of the pad with respect to the printed wiring board of the embodiment in the first embodiment, as shown in Table 2 below. The same process as in the first example is performed by changing the distance between the pad edge / wiring, and each of the printed wiring boards of Examples 11 to 16 and Reference Examples 11 and 12 is used as a collective substrate before cutting. One sheet (1200 pieces / sheet) was prepared. An energization test was performed on the prepared printed wiring board in the same manner as in the first example. The results of changing the pad / wiring distance are shown in Table 2 below.

  From the results in Table 2, it was found that the nearest pad edge / wiring distance is preferably 10 μm or more. On the other hand, if this distance exceeds 50 μm, it may be impossible to achieve a narrow pitch. Therefore, it has been found that the distance between the nearest pad edge / wiring is preferably 10 to 50 μm. For the same reason, it has been found that the distance between the edges of the nearest pad is preferably 10 to 50 μm.

<Fourth embodiment>
In order to obtain a suitable example of the amount of the inorganic filler added to the solder resist layer with respect to the printed wiring board of the example in the first example, the amount of the inorganic filler added is changed as shown in Table 4 below. The same steps as in the example were performed, and one printed wiring board (1200 pieces / sheet) of each of the printed wiring boards of Examples 21 to 25 and Reference Examples 21 and 22 was prepared as a collective substrate before cutting. An energization test was performed on the prepared printed wiring board in the same manner as in the first example. The results are shown in Table 3 below.

  From the results of Table 3, it was found that the addition amount of the inorganic filler to the solder resist is preferably 15 to 35 mass%.

  According to the method for manufacturing a printed wiring board of the present invention, it is possible to obtain a printed wiring board having a lower possibility of occurrence of a short circuit between pads adjacent to each other and between the pad and the wiring. Due to the formation, it can be suitably used for various printed wiring boards having a problem of short-circuit between adjacent pads and between pads and wiring.

DESCRIPTION OF SYMBOLS 1 Base insulation layer 2 Conductor layer 2a Pad 3 Intermediate board 4 Solder resist layer 5 Mask 6 Opening 11 Base insulation layer 12 Conductor layer 12a Conductor pad 13 Solder resist layer 13a Opening 14 Bump 15 Plating metal layer 16 Solder layer 17 Alloy layer

Claims (5)

A base insulating layer made of an insulating material;
A conductor layer formed on the base insulating layer and including pads and wiring;
A solder resist layer formed on the base insulating layer and the conductor layer and having an opening on the pad;
In a method for producing a printed wiring board comprising:
A solder resist laminating step of covering the base insulating layer and the conductor layer with an uncured solder resist layer made of a photocurable resin;
An exposure step of exposing the solder resist layer in a state where the position of the solder resist layer corresponding to the position of the pad of the conductor layer is covered with a mask and curing a portion of the solder resist layer not covered with the mask; ,
A heat treatment step of heating and temporarily curing the solder resist layer after the exposure; and
A development step of developing the pre-cured solder resist layer to form the opening in the solder resist layer;
A heating step of fully curing the solder resist layer after the development;
A method for manufacturing a printed wiring board, comprising:   The method for manufacturing a printed wiring board according to claim 1, wherein the heat treatment condition in the heat treatment step is heating for 10 to 30 minutes at a temperature of 80 to 120C.   The printed wiring board according to claim 1 or 2, wherein a distance from an edge of the pad to the nearest wiring or an edge of another pad is 10 to 50 µm in the printed wiring board. Method.   The said soldering resist layer contains 15-35 mass% of inorganic fillers, The manufacturing method of the printed wiring board of any one of Claims 1-3 characterized by the above-mentioned.   5. The printed wiring board according to claim 1, wherein in the exposure step, the solder resist layer is irradiated with ultraviolet rays including all of I-line, H-line, and G-line. Method.

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