Dry film resist and method for manufacturing printed wiring board

Abstract

A dry film resist has: a resist layer; an intermediate layer disposed on the resist layer; and a support layer disposed on the intermediate layer. The elongation of the resist layer from after the resist layer is cured until the resist layer breaks is 1.5% or more.

Description

Technical Field

[0001] This disclosure relates to a dry film resist and a method for manufacturing printed wiring boards. This application claims priority to Japanese Patent Application No. 2023-190105, filed November 7, 2023. The entire contents of that Japanese patent application are incorporated herein by reference. Background Technology

[0002] For example, International Publication No. 2009 / 054705 (Patent Document 1) discloses a dry film resist. The dry film resist disclosed in Patent Document 1 has a photosensitive resin layer, a resin protective layer, and a base film. The resin protective layer is disposed on the photosensitive resin layer. The base film is disposed on the resin protective layer.

[0003] The dry film resist described in Patent Document 1 is adhered to a substrate by means of a photosensitive resin layer disposed on the substrate. After being adhered to the substrate, in order to eliminate the effects of light scattering caused by the lubricant contained in the base film and surface damage, the base film is peeled off. It should be noted that the reaction between the photosensitive resin contained in the photosensitive resin layer after the base film is peeled off and oxygen is suppressed by a resin protective layer. The photosensitive resin layer and the resin protective layer are exposed and developed to form a resist pattern with openings.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2009 / 054705 Summary of the Invention

[0007] The dry film resist disclosed herein comprises: a resist layer; an intermediate layer disposed on the resist layer; and a support layer disposed on the intermediate layer. The elongation of the resist layer after curing until it breaks is 1.5% or more. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view of dry film resist 100.

[0009] Figure 2 This is a cross-sectional view of the flexible printed circuit board 90 wound around the iron core 91.

[0010] Figure 3 This is a cross-sectional view of the printed wiring board 200.

[0011] Figure 4 This is a manufacturing process diagram of printed wiring board 200.

[0012] Figure 5This is a cross-sectional view illustrating the through-hole forming process S2.

[0013] Figure 6 This is a cross-sectional view illustrating the conductive treatment process S3.

[0014] Figure 7A This is a cross-sectional view illustrating the dry film resist application process S41.

[0015] Figure 7B This is a cross-sectional view illustrating the first support layer peeling process S42.

[0016] Figure 7C This is a cross-sectional view illustrating the first exposure process S43.

[0017] Figure 7D This is a cross-sectional view illustrating the second support layer peeling process S44.

[0018] Figure 7E This is a cross-sectional view illustrating the second exposure process S45.

[0019] Figure 7F This is a cross-sectional view illustrating the developing process S46.

[0020] Figure 8 This is a cross-sectional diagram illustrating the electroplating process S5.

[0021] Figure 9 This is a cross-sectional view illustrating the resist pattern removal process S6.

[0022] Figure 10A This is a microscope image showing the first example of a defect in the resist pattern 60.

[0023] Figure 10B This is a microscope image showing a second example of a defect in the resist pattern 60.

[0024] Figure 11A This is a microscope image showing the first example of damage to the resist pattern 60.

[0025] Figure 11B This is a microscope image showing a second example of damage to the resist pattern 60. Detailed Implementation

[0026] [The technical problem this disclosure aims to solve]

[0027] However, the dry film resist described in Patent Document 1 is sometimes damaged during exposure and development to form a resist pattern. This disclosure was made in view of the aforementioned problems of the prior art. More specifically, this disclosure provides a dry film resist capable of suppressing damage during exposure and development to form a resist pattern.

[0028] [The Effects of This Disclosure]

[0029] The dry film resist according to this disclosure can suppress damage during exposure and development to form a resist pattern.

[0030] [Description of embodiments of this disclosure]

[0031] First, embodiments of this disclosure will be described.

[0032] (1) The dry film resist according to one embodiment includes: a resist layer; an intermediate layer disposed on the resist layer; and a support layer disposed on the intermediate layer. The elongation of the resist layer after curing until the resist layer breaks is 1.5% or more.

[0033] According to the dry film resist described in (1) above, damage can be suppressed when the resist pattern is formed during exposure and development.

[0034] (2) In the dry film resist mentioned in (1) above, the elastic modulus of the resist layer after curing can be 3 GPa or higher.

[0035] According to the dry film resist described in (2) above, damage can be further suppressed during exposure and development to form a resist pattern. It should be noted that when the elastic modulus of the resist layer is less than 3 GPa, there is a risk that the resist layer may be damaged by penetrating the intermediate layer.

[0036] (3) In the dry film resist of (1) or (2) above, the thickness of the intermediate layer may be more than 1 μm and less than 10 μm.

[0037] According to the dry film resist described in (3) above, the resolution during exposure can be improved while further suppressing damage to the resist pattern during exposure and development.

[0038] (4) In the dry film resists mentioned in (1) to (3) above, the thickness of the support layer may be 10 μm or more and 100 μm or less.

[0039] According to the dry film resist described in (4) above, the operability of applying dry film resist can be improved.

[0040] (5) A method for manufacturing a printed wiring board according to an embodiment includes: a step of preparing a base film; a step of pasting a first dry film resist; a step of patterning the first dry film resist to form a first resist pattern; and a step of forming wiring. The base film has a first main surface and a second main surface. A first conductive layer is formed on the first main surface. The first dry film resist has a first resist layer, a first intermediate layer disposed on the first resist layer, and a first support layer disposed on the first intermediate layer, and is pasted such that the first resist layer is disposed on the first conductive layer. The first resist pattern is formed by exposing and developing the first resist layer and the first intermediate layer, and has a first opening that exposes the first conductive layer. The step of forming wiring includes: an electrolytic plating step, in which a first electrolytic plating layer is formed on the first conductive layer exposed from the first opening by electrolytic plating; a removal step, in which the first resist pattern is removed from the first conductive layer; and an etching step, in which a portion of the first conductive layer located below the first resist pattern is removed by etching.

[0041] According to the manufacturing method of the printed wiring board described in (5) above, it is possible to suppress wiring defects.

[0042] (6) The manufacturing method of the printed wiring board in (5) above may also include: a step of pasting a second dry film resist; and a step of patterning the second dry film resist to form a second resist pattern. A second conductive layer may also be formed on the second main surface. The second dry film resist may also have a second resist layer, a second intermediate layer disposed on the second resist layer, and a second support layer disposed on the second intermediate layer, and be pasted in such a way that the second resist layer is disposed on the second conductive layer. The second resist pattern may also be formed by exposing and developing the second resist layer and the second intermediate layer, and have a second opening that exposes the second conductive layer. In the electroplating process, a second electroplating layer may also be formed on the second conductive layer exposed from the second opening. In the removal process, the second resist pattern may also be removed from the second conductive layer. In the etching process, a portion of the second conductive layer located below the second resist pattern may also be removed by etching.

[0043] [Details of the embodiments of this disclosure]

[0044] Next, details of embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following drawings, the same or equivalent parts will be labeled with the same reference numerals, and repeated descriptions will not be given. The dry film resist involved in the embodiments will be designated as dry film resist 100. The printed wiring board involved in the embodiments will be designated as printed wiring board 200.

[0045] (Composition of dry film resist 100)

[0046] The following describes the composition of dry film resist 100.

[0047] Figure 1 This is a cross-sectional view of dry film resist 100. (Example) Figure 1 As shown, the dry film resist 100 has a resist layer 10, an intermediate layer 20 and a support layer 30.

[0048] The resist layer 10 is made of a photosensitive resin material. The resist layer 10 has a first surface 10a and a second surface 10b. The first surface 10a and the second surface 10b are end faces in the thickness direction of the resist layer 10. The second surface 10b is the surface opposite to the first surface 10a.

[0049] The elongation at break (elongation at break of the resist layer 10) of the resist layer 10 after curing is 1.5% or more. The elongation at break of the resist layer 10 after curing is preferably 1.8% or more, more preferably 2.1% or less. The elongation at break of the cured resist layer 10 can be adjusted, for example, by changing the number of bonds (atoms) between curable groups in the compound containing curable groups in the constituent material of the resist layer 10, or by changing the flexibility of the structure between the curable groups in the compound containing curable groups in the constituent material of the resist layer 10. The elongation at break of the cured resist layer 10 is measured by the following method.

[0050] In the determination of the elongation at break after the resist layer 10 has cured, firstly, after the resist layer 10 is bonded to the flexible printed circuit board 90, it is cured by exposure. The exposure conditions are set as follows: development time is twice the development time for the unexposed portion to disappear, and the number of levels in the staged exposure table (Stouffer™ 41 levels) is 12. As a result, a pattern of the resist layer 10 with a width of 20 μm is formed on the main surface 90a of the flexible printed circuit board 90.

[0051] Figure 2 This is a cross-sectional view of the flexible printed circuit board 90 wound around the iron core 91. (See diagram below.) Figure 2 As shown, in the determination of the elongation at break after the resist layer 10 has cured, the second step is to wind the flexible printed circuit board 90 around the iron core 91. At this time, the flexible printed circuit board 90 is wound in a manner in which the pattern of the resist layer 10 is orthogonal to the axis of the iron core, and the bending angle of the flexible printed circuit board 90 during winding is set to 180°.

[0052] With the flexible printed circuit board 90 wound around the iron core 91, observe whether the resist layer 10 is broken. If no breakage is observed in the resist layer 10, wound the flexible printed circuit board 90 around the iron core 91 with an outer diameter reduced by 0.2 mm, and similarly observe whether the resist layer 10 is broken. Repeat this operation by successively reducing the outer diameter of the iron core 91 by 0.2 mm until a breakage is observed in the resist layer 10. It should be noted that the outer diameter of the iron core 91 initially wound with the flexible printed circuit board 90 is, for example, 3.0 mm.

[0053] In the determination of elongation at break after the resist layer 10 has cured, thirdly, the bending center position of the main surface 90b and the flexible printed circuit board 90 is calculated based on the following formula 1 (in Figure 2 The distance between the two layers (represented by dashed lines) is c (unit: μm). It should be noted that in Equation 1, a is the thickness of the flexible printed circuit board 90 (unit: μm), b is the thickness of the resist layer 10 (unit: μm), E1 is the elastic modulus of the flexible printed circuit board 90 (unit: GPa), and E2 is the elastic modulus of the resist layer 10 (unit: GPa).

[0054]

[0055] In determining the elongation at break after the resist layer 10 has cured, fourthly, the elongation at break after the resist layer 10 has cured is calculated by substituting c, obtained as described above, into Equation 2 below. It should be noted that in Equation 2, r is the radius of the iron core 91.

[0056]

[0057] The elastic modulus of the resist layer 10 is, for example, 3 GPa or more. Preferably, the elastic modulus of the resist layer 10 is 4 GPa or more, more preferably 5 GPa or more. For example, the elastic modulus of the resist layer 10 is 8 GPa or less. Preferably, the elastic modulus of the resist layer 10 is 7 GPa or less, more preferably 6 GPa or less. The elastic modulus of the resist layer 10 is determined by the following method.

[0058] First, the resist layer 10 is cured by exposure. The exposure conditions are set as follows: development time is twice the time required for the unexposed portion to disappear, and the level of the staged exposure table (Stouffer™ 41 levels) is, for example, level 12. Second, the elastic modulus of the cured resist layer 10 is measured. The elastic modulus of the resist layer 10 is measured using a Berkovich indenter in a Bruker Hysitron TI980 TriboIndenter under a maximum load of 10 N and a vibration frequency of 200 Hz. It should be noted that the elastic modulus of the cured resist layer 10 can be adjusted, for example, by changing the density of the curable groups in the constituent materials of the resist layer 10.

[0059] The intermediate layer 20 is made of an oxygen-barrier resin material. That is, the intermediate layer 20 is used to inhibit the reaction between the material of the resist layer 10 and oxygen in the air during the peeling of the support layer 30, thus making the photocuring reaction of the resist layer 10 difficult to occur during exposure. The material of the intermediate layer 20 can be any water-soluble or alkali-soluble resin; specific examples of the material for the intermediate layer 20 include vinyl alcohol resin, phenolic resin, and acrylic resin. Since the intermediate layer 20 needs to adhere tightly to the resist layer 10 after the support layer 30 is peeled off, acrylic resin is preferred as the material for the intermediate layer 20. The tack of the intermediate layer 20 is, for example, 1 kN / m. 2 Above and 50kN / m 2 The following is preferred: 2kN / m 2 Above and 20kN / m 2 The following is a further preferred value: 4kN / m 2 Above and 15kN / m 2 The following applies. If the adhesion of the intermediate layer 20 is too weak, it will easily peel off from the resist layer 10, resulting in a loss of barrier properties against the resist layer 10. On the other hand, if the adhesion of the intermediate layer 20 is too strong, it will cause problems in the second exposure process S45 (see reference). Figure 4 In the process, when the intermediate layer 20 contacts the worktable 70 (refer to...), Figure 7D The material will adhere to the worktable 70, causing abnormal transport. The tackiness of the intermediate layer 20 can be adjusted by changing the type, molecular weight, and proportion of the constituent materials of the intermediate layer 20. The tackiness of the intermediate layer 20 is determined by applying 600 gf (approximately 6 N) of pressure to the intermediate layer 20 for 60 seconds with a 5 mm diameter stainless steel probe, and then measuring the peak intensity applied to the probe when it is moved vertically at a speed of 600 mm / min.

[0060] The intermediate layer 20 has a third surface 20a and a fourth surface 20b. The third surface 20a and the fourth surface 20b are end faces of the intermediate layer 20 in the thickness direction. The fourth surface 20b is the surface opposite to the third surface 20a. The intermediate layer 20 is disposed on the resist layer 10. More specifically, the intermediate layer 20 is disposed on the first surface 10a such that the fourth surface 20b is opposite to the first surface 10a.

[0061] The thickness of the intermediate layer 20 is defined as thickness T1. Thickness T1 is the distance between the third surface 20a and the fourth surface 20b. Thickness T1 is preferably 0.05 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, and even more preferably 1.5 μm or more and 3 μm or less.

[0062] The support layer 30 is a layer used to maintain the rigidity of the dry film resist 100. Specific examples of the support layer 30 include polyethylene terephthalate (PET).

[0063] The support layer 30 has a fifth surface 30a and a sixth surface 30b. The fifth surface 30a and the sixth surface 30b are end faces of the support layer 30 in the thickness direction. The sixth surface 30b is the surface opposite to the fifth surface 30a. The support layer 30 is disposed on the intermediate layer 20. More specifically, the support layer 30 is disposed on the third surface 20a such that the sixth surface 30b is opposite to the third surface 20a.

[0064] The thickness of the support layer 30 is defined as thickness T2. Thickness T2 is the distance between the fifth surface 30a and the sixth surface 30b. Thickness T2 is preferably 10 μm or more, more preferably 15 μm or more. Thickness T2 is preferably 100 μm or less, more preferably 60 μm or less.

[0065] It should be noted that the dry film resist 100 may also have a resin protective layer 80. The resin protective layer 80 is disposed on the second surface 10b. Specific examples of the constituent materials of the resin protective layer 80 include polyethylene, polypropylene, and polyester resin. The thickness of the resin protective layer 80 is preferably 5 μm or more, more preferably 10 μm or more. The thickness of the resin protective layer 80 is preferably 50 μm or less, more preferably 30 μm or less.

[0066] (Composition of printed wiring board 200)

[0067] The following describes the structure of the printed wiring board 200.

[0068] Figure 3 This is a cross-sectional view of printed wiring board 200. (Example) Figure 3 As shown, the printed wiring board 200 has a base film 40, a first wiring 51 and a second wiring 52.

[0069] The base film 40 is made of a flexible, electrically insulating material. Polyimide is a specific example of the base film 40's constituent material. The base film 40 has a first main surface 40a and a second main surface 40b. The first main surface 40a and the second main surface 40b are end faces of the base film 40 in the thickness direction. The second main surface 40b is the surface opposite to the first main surface 40a.

[0070] The first wiring 51 is disposed on the first main surface 40a, and the second wiring 52 is disposed on the second main surface 40b. The first wiring 51 and the second wiring 52 each have a conductive layer 53 and an electrolytic plating layer 54.

[0071] A conductive layer 53 is disposed on the main surfaces of the base film 40 (on the first main surface 40a and the second main surface 40b). The conductive layer 53 may have, for example, a first layer 53a and a second layer 53b. The first layer 53a is disposed on the main surfaces of the base film 40 (on the first main surface 40a and the second main surface 40b). The second layer 53b is disposed on the first layer 53a. The constituent material of the first layer 53a is, for example, a nickel-chromium alloy. The first layer 53a may be, for example, a sputtered layer (a layer formed by sputtering). The constituent material of the second layer 53b may be, for example, copper. The second layer 53b may be, for example, an electroless plating layer (a layer formed by electroless plating).

[0072] The first wiring 51 has a pad 51a. The second wiring 52 has a pad 52a. The pads 51a and 52a are arranged to overlap when viewed from above. A through-hole 40c is formed in the base film 40 and the first layer 53a. The through-hole 40c penetrates the base film 40 and the first layer 53a along the thickness direction. The second layer 53b is also disposed on the inner wall surface of the through-hole 40c.

[0073] The electroplated layer 54 is formed by electroplating. The electroplated layer 54 is disposed on the conductive layer 53 (on the second layer 53b). The constituent material of the electroplated layer 54 is, for example, copper. The first wiring 51 and the second wiring 52 are electrically connected through the second layer 53b disposed on the inner wall surface of the through hole 40c and the electroplated layer 54.

[0074] (Manufacturing method of printed wiring board 200)

[0075] The following describes the manufacturing method of the printed wiring board 200.

[0076] Figure 4 This is a manufacturing process diagram for printed wiring board 200. (Example) Figure 4 As shown, the manufacturing method of the printed wiring board 200 includes a preparation step S1, a through-hole forming step S2, a conductivity treatment step S3, a resist pattern forming step S4, an electrolytic plating step S5, a resist pattern removal step S6, and an etching step S7.

[0077] In preparation step S1, a base film 40 is prepared. In the base film 40 prepared in preparation step S1, a first layer 53a is disposed on the first main surface 40a and the second main surface 40b.

[0078] After the preparation step S1, the through-hole forming step S2 is performed. Figure 5 This is a cross-sectional view illustrating the through-hole forming process S2. (For example...) Figure 5 As shown, in the through-hole forming process S2, through-hole 40c is formed in the base film 40 and the first layer 53a, for example, by irradiating with a laser.

[0079] The conductive treatment process S3 is performed after the through-hole forming process S2. Figure 6 This is a cross-sectional view illustrating the conductivity treatment process S3. For example... Figure 6 As shown, in the conductivity treatment step S3, a second layer 53b is formed on the first layer 53a, for example, by electroless plating. At this time, the second layer 53b is also formed on the inner wall surface of the through hole 40c.

[0080] After the conductivity treatment step S3, a resist patterning step S4 is performed. In the resist patterning step S4, a resist pattern 60 is formed. The resist patterning step S4 includes a dry film resist bonding step S41, a first support layer peeling step S42, a first exposure step S43, a second support layer peeling step S44, a second exposure step S45, and a developing step S46.

[0081] After the dry film resist application process S41, a first support layer peeling process S42 is performed. After the first support layer peeling process S42, a first exposure process S43 is performed. After the first exposure process S43, a second support layer peeling process S44 is performed. After the second support layer peeling process S44, a second exposure process S45 is performed. After the second exposure process S45, a developing process S46 is performed.

[0082] Figure 7A This is a cross-sectional view illustrating the dry film resist application process S41. (For example...) Figure 7A As shown, in the dry film resist bonding process S41, the dry film resist 100 is bonded. The dry film resist 100 is bonded such that the resist layer 10 is disposed on the conductive layer 53 (i.e., with the second surface 10b facing the conductive layer 53). It should be noted that if the dry film resist 100 has a resin protective layer 80, the resin protective layer 80 is peeled off before the dry film resist bonding process S41.

[0083] Figure 7B This is a cross-sectional view illustrating the first support layer peeling process S42. (For example...) Figure 7BAs shown, in the first support layer peeling process S42, firstly, the base film 40 with the dry film resist 100 adhered to the conductive layer 53 located on the second main surface 40b is placed on the worktable (worktable 70) of the exposure machine with the dry film resist 100 adhered to it facing the worktable. It should be noted that there may sometimes be small protrusions 71 or foreign objects 72 on the surface of the worktable 70. Secondly, the support layer 30 of the dry film resist 100 adhered to the conductive layer 53 located on the first main surface 40a is peeled off.

[0084] Figure 7C This is a cross-sectional view illustrating the first exposure process S43. For example... Figure 7C As shown, in the first exposure process S43, the resist layer 10 and the intermediate layer 20 of the dry film resist 100 of the conductive layer 53 attached to the first main surface 40a are exposed.

[0085] Figure 7D This is a cross-sectional view illustrating the second support layer peeling process S44. (For example...) Figure 7D As shown, in the second support layer peeling process S44, firstly, the base film 40 with the dry film resist 100 adhered to the conductive layer 53 on the first main surface 40a is placed on the worktable 70 with the worktable 70 facing the dry film resist 100. As described above, the support layer 30 has been peeled off from the dry film resist 100 adhered to the conductive layer 53 on the first main surface 40a. Therefore, at this time, the intermediate layer 20 of the dry film resist 100 adhered to the conductive layer 53 on the first main surface 40a is in contact with the worktable 70 (protrusion 71, foreign object 72). Secondly, the support layer 30 of the dry film resist 100 adhered to the conductive layer 53 on the second main surface 40b is peeled off.

[0086] Figure 7E This is a cross-sectional view illustrating the second exposure process S45. (For example...) Figure 7E As shown, in the second exposure process S45, the resist layer 10 and the intermediate layer 20 of the dry film resist 100 of the conductive layer 53 attached to the second main surface 40b are exposed.

[0087] Figure 7F This is a cross-sectional diagram illustrating the developing process S46. For example... Figure 7F As shown, in the developing process S46, the exposed resist layer 10 and intermediate layer 20 are developed. This removes the unexposed portions of the resist layer 10 and intermediate layer 20, resulting in a resist pattern 60 with an opening 61. The conductive layer 53 is exposed through the opening 61.

[0088] Electroplating process S5 is performed after the resist pattern formation process S4. Figure 8 This is a cross-sectional diagram illustrating the electroplating process S5. For example... Figure 8As shown, in the electroplating process S5, an electroplating layer 54 is formed on the conductive layer 53 exposed from the opening 61 by performing electroplating.

[0089] After the electroplating process S5, the resist pattern removal process S6 is performed. Figure 9 This is a cross-sectional view illustrating the resist pattern removal process S6. For example... Figure 9 As shown, in the resist pattern removal process S6, the resist pattern 60 is removed. As a result, the conductive layer 53 located beneath the resist pattern 60 is exposed between the adjacent electroplated layers 54.

[0090] After the resist pattern removal step S6, an etching step S7 is performed. In the etching step S7, the conductive layer 53 located beneath the resist pattern 60 is removed by etching. Through the above steps, a [structure / form] is formed. Figure 3 The printed wiring board 200 with the structure shown is shown.

[0091] (Effect of dry film resist 100)

[0092] The following explains the effect of dry film resist 100.

[0093] Because the support layer 30 contains a lubricant, if the resist layer 10 and the intermediate layer 20 are exposed without peeling off the support layer 30, light may sometimes be reflected or scattered due to the lubricant, resulting in unexposed areas remaining in the resist layer 10 and the intermediate layer 20. If unexposed areas exist in the resist layer 10 and the intermediate layer 20, the resist pattern 60 will be defective, and an electroplated layer 54 will also form at the location of the defect. Therefore, the first wiring 51 and the second wiring 52 may sometimes have defects.

[0094] In the manufacturing method of the printed wiring board 200, the support layer 30 is peeled off when the resist pattern 60 is formed using the dry film resist 100. As a result, unexposed portions are less likely to remain in the resist layer 10 and the intermediate layer 20, thus suppressing defects in the first wiring 51 and the second wiring 52.

[0095] In the manufacturing method of the printed wiring board 200, the elongation at break of the cured resist layer 10 is 1.5% or more. Therefore, according to the manufacturing method of the printed wiring board 200, it is possible to suppress the damage to the resist pattern 60, thereby suppressing defects in the first wiring 51 and the second wiring 52.

[0096] In the manufacturing method of the printed wiring board 200, when the support layer 30 is peeled off during the formation of the resist pattern 60 using the dry film resist 100, the intermediate layer 20 sometimes comes into contact with the worktable 70 (protrusion 71, foreign object 72). The protrusion 71 and foreign object 72 sometimes penetrate the intermediate layer 20 and reach the resist layer 10. Therefore, if the elastic modulus of the resist layer 10 is too low, the resist layer 10, and consequently the resist pattern 60, may be damaged due to contact with the protrusion 71 and foreign object 72.

[0097] On the other hand, if the elastic modulus of the resist layer 10 is high, the resist layer 10 will not be easily damaged even when in contact with the protrusion 71 or the foreign object 72. However, if the elastic modulus of the resist layer 10 is too high, the resist layer 10 may sometimes crack after exposure.

[0098] Regarding this, in the dry film resist 100, the elastic modulus of the resist layer 10 is 3 GPa or higher, thus suppressing damage to the resist layer 10 due to contact with the protrusion 71 and the foreign object 72. In the dry film resist 100, the elastic modulus of the resist layer 10 is 7 GPa or lower, thus suppressing cracking of the resist layer 10 after exposure. As described above, the dry film resist 100 can suppress damage during exposure and development to form the resist pattern 60.

[0099] When the thickness T1 is 1 μm or more, the protrusion 71 and foreign matter 72 are less likely to penetrate the intermediate layer 20 and reach the resist layer 10. Furthermore, when the thickness T1 is 10 μm or less, resolution reduction during exposure can be suppressed. Therefore, when the thickness T1 is 1 μm or more and 10 μm or less, damage to the dry film resist 100 as it forms the resist pattern 60 during exposure and development can be further suppressed while simultaneously improving resolution during exposure.

[0100] When exposure is performed without peeling off the support layer 30, it is difficult to thicken the support layer 30 because exposure occurs through it. However, in the dry film resist 100, since exposure is performed after peeling off the support layer 30, exposure is not problematic even if the support layer 30 is thickened. Therefore, in the dry film resist 100, by setting the thickness T2 to 10 μm or more to increase rigidity, the operability during the dry film resist bonding process S41 can be improved. In the above description, an example of circuit formation using a semi-additive method was shown, but the same effect can be expected in a subtractive method of circuit formation by etching a copper layer. Furthermore, in the above description, an example of forming a printed wiring board was shown, but even more significant effects can be obtained in the manufacturing process of flexible printed wiring boards where the substrate is prone to bending during transport. In addition, further significant effects can be obtained when a roll-to-roll method is used in the exposure and development processes.

[0101] (Example)

[0102] To confirm the effectiveness of dry film resist 100, samples 1 to 7 were prepared as shown in Table 1.

[0103]

[0104] Sample 1 does not have the intermediate layer 20, while samples 2 to 7 do have the intermediate layer 20. In samples 2 to 7, the thickness T1 is set to 2 μm. In sample 1, exposure is performed after the support layer 30 has been removed, while in samples 2 to 7, exposure is performed after the support layer 30 has been removed. In samples 1 to 7, the elongation at break and elastic modulus after the resist layer 10 has cured change.

[0105] In each sample, multiple patterns with a width of 10 μm and a length of 5 mm were formed at 10 μm intervals as resist patterns 60. The formation of resist patterns 60 was evaluated by performing an optical automated visual inspection. The resist defect rate was defined as the value obtained by multiplying the number of patterns with defects greater than 3 μm by the total number of patterns and then multiplying the result by 100. Figure 10A This is a microscope image showing the first example of a defect in the resist pattern 60. Figure 10B This is a microscope image showing a second example of a defect in the resist pattern 60. Figure 10A The image shows an example of a defect in the resist pattern 60 caused by the lubricant in the support layer 30. Figure 10B Examples of resist pattern 60 defects that occur during transport are shown. The resist defect rate was evaluated in each sample, as shown in Table 1.

[0106] The value obtained by multiplying the number of collapsed patterns by the total number of patterns by 100 is set as the resist breakage rate. Figure 11A This is a microscope image showing the first example of damage to the resist pattern 60. Figure 11B This is a microscope image showing a second example of damage to the resist pattern 60. Figure 11A The image shows an example of partial scattering of the damaged resist pattern 60. Figure 11B Examples of partial residues of the damaged resist pattern 60 are shown. The resist breakage rate was evaluated in each sample, as shown in Table 1.

[0107] In sample 2, the resist defect rate was reduced compared to sample 1. Based on this comparison, it was experimentally confirmed that exposure by peeling off the support layer 30 can suppress defects in the resist pattern 60.

[0108] In samples 2 and 7, the elongation at break after curing of the resist layer 10 was less than 1.5%. In samples 3 to 6, the elongation at break after curing of the resist layer 10 was greater than 1.5%. In samples 2 and 7, the resist breakage rate was greater than that in samples 3 to 6. Based on this comparison, it is experimentally clear that by setting the elongation at break after curing of the resist layer 10 to be greater than 1.5%, it is less likely to cause breakage of the resist pattern 60.

[0109] In samples 3 to 5, the elastic modulus of the cured resist layer 10 was above 3 GPa. In sample 6, the elastic modulus of the cured resist layer 10 was less than 3 GPa. The resist defect rate was lower in samples 3 to 5 than in sample 6. Based on this comparison, it is experimentally clear that setting the elastic modulus of the cured resist layer 10 to above 3 GPa can further suppress defects in the resist pattern 60.

[0110] It should be understood that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is set forth not by the above embodiments but by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0111] Explanation of reference numerals in the attached figures

[0112] 100: Dry film resist; 10: Resist layer; 10a: First side; 10b: Second side; 20: Intermediate layer; 20a: Third side; 20b: Fourth side; 30: Support layer; 30a: Fifth side; 30b: Sixth side; 40: Base film; 40a: First main side; 40b: Second main side; 40c: Through hole; 51: First wiring; 51a: Pad; 52: Second wiring; 52a: Pad; 53: Conductive layer; 53a: First layer; 53b: Second layer; 54: Electrolytic plating layer; 60: Resist pattern; 61: Opening; 70: Worktable; 71: Protrusion; 72 : Foreign matter; 80: Resin protective layer; 90: Flexible printed circuit board; 90a: Main surface; 90b: Main surface; 91: Iron core; 200: Printed wiring board; S1: Preparation process; S2: Forming process; S3: Conductivity treatment process; S4: Resist pattern forming process; S41: Dry film resist bonding process; S42: First support layer peeling process; S43: First exposure process; S44: Second support layer peeling process; S45: Second exposure process; S46: Development process; S5: Electrolytic plating process; S6: Resist pattern removal process; S7: Etching process; T1, T2: Thickness.

Claims

1. A dry film resist, comprising: Resist layer; An intermediate layer is disposed on the resist layer; as well as A support layer is disposed on the intermediate layer. The elongation of the resist layer after curing until it breaks is 1.5% or more.

2. The dry film resist according to claim 1, wherein, The elastic modulus of the resist layer after curing is above 3 GPa.

3. The dry film resist according to claim 1, wherein, The thickness of the intermediate layer is greater than 1 μm and less than 10 μm.

4. The dry film resist according to any one of claims 1 to 3, wherein, The thickness of the support layer is more than 10 μm and less than 100 μm.

5. A method for manufacturing a printed wiring board, comprising: The process of preparing the base film; The process of applying the first dry film resist; The process of patterning the first dry film resist to form a first resist pattern; and The process of forming wiring, The base film has a first main surface and a second main surface. A first conductive layer is formed on the first main surface. The first dry film resist has a first resist layer, a first intermediate layer disposed on the first resist layer, and a first support layer disposed on the first intermediate layer, and is adhered such that the first resist layer is disposed on the first conductive layer. The first resist pattern is formed by exposing and developing the first resist layer and the first intermediate layer, and has a first opening that exposes the first conductive layer. The process of forming wiring includes: The electroplating process forms a first electroplated layer on the first conductive layer exposed from the first opening through electroplating. The removal process removes the first resist pattern from the first conductive layer; as well as The etching process removes a portion of the first conductive layer located beneath the first resist pattern by etching.

6. The method for manufacturing a printed wiring board according to claim 5, wherein, The method for manufacturing the printed wiring board further includes: The process of applying the second dry film resist; and The process of patterning the second dry film resist to form a second resist pattern. A second conductive layer is formed on the second main surface. The second dry film resist has a second resist layer, a second intermediate layer disposed on the second resist layer, and a second support layer disposed on the second intermediate layer, and is adhered such that the second resist layer is disposed on the second conductive layer. The second resist pattern is formed by exposing and developing the second resist layer and the second intermediate layer, and has a second opening that exposes the second conductive layer. In the electroplating process, a second electroplated layer is formed on the second conductive layer exposed from the second opening. In the removal process, the second resist pattern is removed from the second conductive layer. In the etching process, a portion of the second conductive layer located beneath the second resist pattern is removed by etching.

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