Wiring forming method and transfer mold manufacturing method

Abstract

Provided is a revolutionary wiring forming method that has never been used before, which can form transfer wiring using a transfer mold without flattening a substrate having uneven surfaces. A wiring forming method, wherein a conductive component (2) is filled into a concave portion (4a) of a transfer mold (4) having a predetermined pattern of concave portions (4a), the transfer mold (4) filled with the conductive component (2) is overlapped with the surface of a substrate (1) having uneven surfaces, the conductive component (2) is transferred to the surface of the substrate (1), and a wiring portion (3) is formed on the surface of the substrate (1) using the conductive component (2), wherein the transfer mold (4) is a soft transfer mold having a hardness of 40 to 70 as measured by a type A durometer.

Description

Technical Field

[0001] The present invention relates to a wiring forming method for forming wiring of a predetermined pattern on a substrate, and in particular to a wiring forming method suitable for forming wiring on a surface of a substrate having projections and depressions. Background Art

[0002] Wiring formation using conductive paste can be performed at a lower temperature than conventional wiring formation using metal such as copper wiring or solder, and thus wiring formation and chip mounting on films such as plastic, which have not been possible so far, are possible.

[0003] In the past, the wiring formation using this conductive paste was usually carried out using a printing method. However, there is a limit to the minimum line width of the wiring that can be formed in the printing method. For example, in representative screen printing, the printing of wiring with a width of about 30 μm is considered to be the limit. In addition, a conductive component in the form of a paste or ink is used in the printing method, but it does not harden immediately after printing on the substrate. Therefore, when forming thick wiring (wiring with a high aspect ratio), the wiring oozes out, etc., which reduces the dimensional accuracy. In addition, the shape collapses due to the flow caused by the certain viscosity of the conductive component in the form of a paste or ink. Therefore, the current situation is that the upper limit of the aspect ratio of the wiring that can be formed by the printing method is at most about 0.5.

[0004] On the other hand, in the transfer wiring formation method (imprint method) using a transfer mold, since wiring is miniaturized to a nanometer size and the conductive paste is cured and transferred, wiring with an aspect ratio of 1 or more can be formed.

[0005] Regarding the transfer wiring formation method using the transfer mold, the present applicant has proposed a method for manufacturing a substrate having a conductive portion disclosed in Japanese Patent Application Laid-Open No. 2016-58664 (hereinafter referred to as “conventional example”).

[0006] In this conventional example, a conductive paste is filled in a recessed portion of a mold (marked as a printing plate in Japanese Patent Laid-Open No. 2016-58664) having a recessed portion formed with a pattern identical to a wiring pattern formed on a substrate, and the mold having the conductive paste filled in the recessed portion is overlapped and crimped onto the substrate, thereby transferring the conductive paste filled in the recessed portion of the mold to the substrate, thereby forming wiring of a specified pattern on the substrate.

[0007] However, in the prior art, since a hard transfer mold called a semi-preform is used, it is difficult to form a substrate having concave and convex (steps) on the wiring forming surface where other wirings are already formed. Figure 2As shown, the transfer mold 14 cannot properly contact (stick to) the surface of the substrate 11 due to the unevenness, thereby causing the transferred wiring 13 to float, especially near the wiring step preformed on the substrate 11.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2016-58664 Summary of the invention

[0011] Problems to be solved by the invention

[0012] Thus, in conventional wiring formation, there is a problem that wiring with a high aspect ratio cannot be formed in wiring formation using printing, and there is a problem that wiring formation using a transfer mold is not applicable to substrates having uneven surfaces.

[0013] Therefore, when forming wiring with a high aspect ratio on a substrate with an uneven surface, the current situation is that the substrate with an uneven surface must be flattened, and after the substrate surface is flattened, wiring is formed using a transfer mold. There is a problem of increased man-hours for the flattening process and increased costs.

[0014] The present invention has been made in view of the above-mentioned current situation, and provides an epoch-making wiring forming method which has never been seen before, in which a transfer wiring can be formed using a transfer mold without performing a planarization process on a substrate having an uneven surface.

[0015] Means used to solve problems

[0016] The gist of the present invention will be described with reference to the accompanying drawings.

[0017] A wiring forming method is provided, wherein a conductive component (2) is filled in a concave portion (4a) of a transfer mold (4) having a concave portion (4a) with a prescribed pattern, the transfer mold (4) filled with the conductive component (2) is overlapped with the surface of a substrate (1) having concave and convex portions, the conductive component (2) is transferred to the surface of the substrate (1), and a wiring portion (3) is formed on the surface of the substrate (1) using the conductive component (2). The wiring forming method is characterized in that the wiring forming method comprises: a preparation step of preparing a soft transfer mold (4) having a hardness of 40 to 70 as measured by a type A durometer; and a crimping step of, after overlapping the transfer mold (4) with the surface of the substrate (1), crimping is performed so that the transfer mold (4) is deformed in a manner following the concave and convex portions, so that the surface of the transfer mold (4) is in close contact with the surface of the substrate (1).

[0018] In addition, according to the wiring forming method described in Technical Solution 1, it is characterized in that the concave-convex is a step difference formed by a wiring with an aspect ratio of 1 or more arranged on the surface of the substrate 1, and the crimping process is the following process: after the transfer mold (4) is overlapped with the surface of the substrate (1), crimping is performed so that the transfer mold (4) is deformed in a manner following the concave-convex, so that the surface of the transfer mold (4) is in close contact with the surface of the substrate (1) and the upper surface of the wiring.

[0019] In addition, the wiring forming method according to claim 1 is characterized in that the transfer mold 4 is made of a resin material in which a curing agent is mixed in a main agent having a silicone-based polymer compound as a main component.

[0020] In addition, the wiring forming method according to claim 2 is characterized in that the transfer mold 4 is made of a resin material in which a curing agent is mixed in a main agent having a silicone-based polymer compound as a main component.

[0021] In addition, according to the wiring forming method described in Technical Solution 3, it is characterized in that the resin material is a mixture of the main agent and the hardener in a mixing ratio of approximately 5:1.

[0022] In addition, according to the wiring forming method described in Technical Solution 4, it is characterized in that the resin material is a mixture of the main agent and the hardener in a mixing ratio of approximately 5:1.

[0023] In addition, the wiring forming method according to any one of technical solutions 3 to 6 is characterized in that the transfer mold 4 is obtained by setting the resin material on an original plate having a convex portion with a specified pattern, press-forming it using a supporting substrate, and performing a hardening treatment.

[0024] In addition, according to the wiring forming method described in Technical Solution 7, it is characterized in that the hardening treatment is a room temperature hardening treatment in which hardening is performed at room temperature and a heat hardening treatment in which hardening is performed by heating at a temperature of 200° C. or above.

[0025] In addition, according to the wiring formation method described in Technical Solution 8, it is characterized in that the room temperature curing treatment is carried out for more than 24 hours.

[0026] In addition, the wiring forming method according to Technical Solution 8 is characterized in that the hardening treatment is performed in a space set at 15°C to 30°C for 48 hours, and then the heat hardening treatment is performed at 200°C to 250°C for 30 minutes.

[0027] In addition, the wiring forming method according to Technical Solution 9 is characterized in that the hardening treatment is performed in a space set at 15°C to 30°C for 48 hours, and then the heat hardening treatment is performed at 200°C to 250°C for 30 minutes.

[0028] Effects of the Invention

[0029] As described above, the present invention can form the transfer wiring using the transfer mold even for a substrate having uneven surfaces.

[0030] Therefore, for example, when forming high aspect ratio wiring on a substrate having an uneven surface, by using the present invention, the flattening treatment that was previously required when using a transfer mold is no longer necessary, the corresponding working hours are reduced, and the effects of improved productivity and cost reduction are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is an explanatory diagram showing a wiring formation state when the transfer mold of this embodiment is used.

[0032] Figure 2 It is an explanatory diagram showing a wiring formation state when a conventional transfer mold is used.

[0033] Figure 3 It is a process flow chart of the present embodiment. DETAILED DESCRIPTION

[0034] Preferred embodiments of the present invention will be briefly described below with reference to the accompanying drawings to illustrate the effects of the present invention.

[0035] The conductive member 2 is filled in the recessed portions 4 a of a predetermined pattern formed in the transfer mold 4 , and the transfer mold 4 filled with the conductive member 2 in the recessed portions 4 a is overlapped and pressure-bonded to the surface of the substrate 1 .

[0036] By this pressure contact, the transfer mold 4 is deformed following the irregularities of the substrate surface, and the transfer mold 4 is brought into close contact with the substrate surface.

[0037] As a result, the undesirable situation in which the wiring portion 3 formed by transfer becomes floating (not grounded to the substrate 1) near the wiring step pre-formed on the substrate 1 will not occur. Therefore, even if the substrate with an uneven surface is not flattened, transfer wiring formation using a transfer mold can be performed.

[0038] Therefore, for example, when forming high aspect ratio wiring on a substrate having an uneven surface, by using the present invention, the flattening treatment that was previously required when using a transfer mold is no longer necessary, the corresponding working hours are reduced, and the effects of improved productivity and cost reduction are achieved.

[0039] [Example]

[0040] Specific embodiments of the present invention will be described based on the drawings.

[0041] This embodiment is a wiring forming method in which a conductive member 2 is filled in a concave portion 4a of a transfer mold 4 having concave portions 4a of a predetermined pattern, the transfer mold 4 filled with the conductive member 2 is overlapped with the surface of a substrate 1 having concave and convex portions, the conductive member 2 hardened in the concave portion 4a is transferred to the surface of the substrate 1, and a wiring portion 3 is formed on the surface of the substrate 1 using the conductive member 2. That is, this embodiment is a wiring forming method in which wiring is already formed on the substrate 1, and the wiring portion 3 is formed by transfer on the substrate 1 having concave and convex portions (steps) on the surface due to the wiring by an imprint method using the transfer mold 4.

[0042] First, the transfer mold 4 and the conductive member 2 used in this embodiment will be described.

[0043] The transfer mold 4 of this embodiment is a soft transfer mold 4 generally called a soft preform mold obtained by dropping a resin material on an original plate (master mold) having convex portions of a predetermined pattern, performing pressure molding using a supporting substrate, and then performing a curing treatment.

[0044] Specifically, the transfer mold 4 of the present embodiment is made of silicone resin obtained by hardening a resin material in which a main agent containing a silicone-based polymer compound as a main component and a hardener are mixed, and has a hardness of about 40 to 70 as measured by a type A durometer.

[0045] The recessed portion 4 a formed in the transfer mold 4 is formed into a tapered (forward tapered) recessed portion such that the shape of the wiring portion 3 formed by transfer on the substrate 1 becomes a forward tapered shape.

[0046] Specifically, the transfer mold 4 of this embodiment is manufactured as follows.

[0047] A resin material in which PDMS (polydimethylsiloxane) as a main agent and a hardener were mixed at a mixing ratio of 5:1 was dropped onto an original plate having convex portions formed in a predetermined pattern, and pressure molding was performed using a supporting substrate.

[0048] It should be noted that, in the resin material with PDMS as the main agent, the mixing ratio of the main agent to the hardener is about 10:1 in the past, but in this embodiment, the ratio of the hardener is increased (about 2 times) as described above. This is to reduce the adhesiveness (viscosity) of the surface of the transfer mold 4 after hardening, and to make it easier to scrape off the conductive component 2 on the surface of the transfer mold 4.

[0049] Next, the press-molded resin material is cured at room temperature (15°C to 30°C, preferably 25°C) for 24 hours or more, preferably 48 hours or more. It should be noted that the room temperature curing conditions in this embodiment are 25°C and 48 hours.

[0050] Next, the transfer mold 4 that has been cured at room temperature is removed from the original plate, and a heating device (such as a heating plate, etc.) is used to heat and cure the removed transfer mold 4 at 200°C to 300°C, preferably at 250°C, for about 30 minutes to formally cure the resin material, thereby completing the process.

[0051] The hardness of the transfer mold 4 formed by the above-mentioned manufacturing method is about 60 as measured by a type A hardness meter.

[0052] It should be noted that, in the resin material with PDMS as the main agent, in the past, the resin material dripped onto the original plate was press-formed using a supporting substrate, and then subjected to a heat curing treatment at 100°C to 150°C for about 10 minutes to 35 minutes, and the transfer mold was hardened to a specified hardness by the heat curing treatment. However, in the previous heat curing treatment, due to the difference in thermal expansion coefficients between the transfer mold and the original plate (main material, glass), the pattern shrinkage of more than 2% was also generated in the heat curing treatment at 100°C on the lower limit side. On the other hand, in this embodiment, by setting the curing treatment as a two-stage treatment of room temperature curing treatment and heat curing treatment as described above, the pattern shrinkage can be suppressed to about 0.5%.

[0053] Specifically, in this embodiment, the pattern shrinkage after room temperature curing at 25° C. for 48 hours is about 0.1%, and the pattern shrinkage after heat curing at 250° C. for 30 minutes is about 0.6%.

[0054] The conductive member 2 used in the present embodiment is a conductive paste containing an activated light-curing resin, in which an activated light-curing resin is contained in a conductive paste.

[0055] That is, in the wiring forming method of the present embodiment, the conductive member 2 is not hardened by heating but hardened by activating light such as ultraviolet rays.

[0056] Specifically, the conductive paste can be selected from Ag paste (including nano paste), Cu paste (including nano paste), Au paste (including nano paste), Pt paste (including nano paste), Pd paste (including nano paste), Ru paste (including nano paste), and C paste (including nano paste). This embodiment uses Ag paste.

[0057] In addition, the present embodiment uses a conductive paste whose average particle size is set to 1 / 5 to 1 / 10 of the minimum line width of the wiring portion 3 formed on the substrate 1. That is, for example, when forming a wiring pattern with a minimum L / S (line & space) = 5 μm / 5 μm, a conductive paste whose average particle size is set to 0.5 μm to 1.0 μm is used.

[0058] The activated light-curable resin contained in the conductive paste is an ultraviolet-curable resin, and is contained in the conductive paste so that the volume content in the conductive member 2 becomes 20% to 40%.

[0059] That is, the conductive member 2 of the present embodiment is Ag paste containing ultraviolet curing resin, in which the volume ratio of Ag paste to ultraviolet curing resin is set to 6:4 to 8:2.

[0060] Next, a specific wiring forming method of this embodiment is described.

[0061] As described above, the wiring forming method of the present embodiment is the following wiring forming method: a conductive component 2 is filled in the concave portion 4a of a transfer mold 4 having a concave portion 4a with a prescribed pattern, the transfer mold 4 filled with the conductive component 2 is overlapped with the surface of a substrate 1 having convex and concave portions, the conductive component 2 in the concave portion 4a is transferred to the surface of the substrate 1, and a wiring portion 3 is formed on the surface of the substrate 1 using the conductive component 2.

[0062] That is, Figure 3 As shown, this embodiment comprises: a conductive component filling treatment step, in which the conductive component 2 is filled into the concave portion 4a of the transfer mold 4; a transfer mold overlapping treatment step, in which the transfer mold 4 filled with the conductive component 2 is overlapped on the substrate 1; a conductive component hardening treatment step, in which the conductive component 2 filled in the concave portion 4a of the transfer mold 4 is hardened; and a conductive component transfer treatment step, in which the conductive component 2 hardened in the concave portion 4a of the transfer mold 4 is transferred to the substrate 1 to form a wiring portion 3 of a specified pattern on the substrate 1, and the treatment is performed in this order.

[0063] Hereinafter, each processing step of this embodiment will be described.

[0064] The conductive component filling treatment step is a step in which the following treatment is performed: the transfer mold 4 is set in a manner in which the opening portion of the recess 4a faces upward, and after the conductive component 2 is filled into the recess 4a from above, a scraper (scraper) is used to scrape off the conductive component 2 overflowing from the surface of the transfer mold 4 and the recess 4a, and only the conductive component 2 is filled into the recess 4a.

[0065] It should be noted that, as described above, the transfer mold 4 used in this embodiment has a larger mixing ratio of the hardener to the main agent than in the past, so that the adhesion (stickiness) of the surface of the transfer mold 4 is reduced. Therefore, in the conductive component filling treatment process, the unnecessary conductive components 2 on the surface of the transfer mold 4 can be smoothly scraped off, and the unnecessary conductive components 2 can be prevented from remaining on the surface of the transfer mold 4 as much as possible.

[0066] The transfer mold overlapping treatment step is a step of overlapping the transfer mold 4 in which the concave portion 4 a is filled with the conductive member 2 and the substrate 1 , and pressing the transfer mold 4 to the substrate 1 by applying pressure.

[0067] In this embodiment, a soft transfer mold 4 (soft preform mold) having a hardness of 60 as measured by a type A hardness meter is used as the transfer mold 4. Figure 1 As shown, when the transfer mold 4 is pressed against the substrate 1, the transfer mold 4 elastically deforms following the concavities and convexities of the substrate 1, specifically, following the steps formed by the wiring already formed on the substrate 1, and the surface of the transfer mold 4 (the opening side of the recess 4a) becomes grounded (closely attached) to the surface of the substrate 1 and the upper surface of the wiring already formed on the substrate 1.

[0068] The conductive member curing process is a process of curing the conductive member 2 filled in the concave portion 4 a of the transfer mold 4 . In the present embodiment, the conductive member 2 is cured by ultraviolet irradiation.

[0069] Specifically, ultraviolet rays are irradiated from the bottom side of the concave portion 4a of the transfer mold 4 to harden the contact interface between the conductive component 2 filled in the concave portion 4a of the transfer mold 4 and the inner surface of the concave portion, thereby improving the releasability of the conductive component 2 from the transfer mold 4.

[0070] By curing the conductive member 2 by ultraviolet irradiation as in the present embodiment, the processing time can be significantly shortened compared to the case of curing by heating.

[0071] It should be noted that the conductive member hardening treatment step may be performed before the transfer mold 4 is superimposed on the substrate 1 , that is, before the transfer mold superimposing treatment step.

[0072] In the conductive member transfer process, the transfer mold 4 overlapping the substrate 1 is separated from the substrate 1 , and the conductive member 2 in the recess 4 a of the transfer mold 4 is transferred to the substrate 1 , thereby forming a wiring portion 3 of a predetermined pattern on the substrate 1 .

[0073] Next, the effects of this embodiment will be described below.

[0074] In this embodiment, a soft transfer mold 4 (soft preform mold) having a hardness of 60 as measured by a type A hardness tester is used as the transfer mold 4. Therefore, even if the substrate having an uneven surface is not flattened, transfer wiring formation (wiring formation based on the imprinting method) using the transfer mold can be performed.

[0075] Therefore, for example, when forming wiring with a high aspect ratio (wiring with a high wiring height relative to the wiring width and a large step difference) on a substrate with an uneven surface, a flattening treatment was required in the past. However, the present invention does not require such a flattening treatment, thus reducing the corresponding working hours and achieving the effects of improved productivity and reduced costs.

[0076] Furthermore, the transfer mold 4 used in this embodiment has lower surface adhesiveness (tackiness) than conventional transfer molds, so the workability of scraping off the conductive member 2 using a scraping tool (scraper) is improved.

[0077] Furthermore, the transfer mold 4 used in the present embodiment is hardened by a two-step hardening process of a room temperature hardening process and a heat hardening process, and therefore the pattern shrinkage can be suppressed to about 0.5%.

[0078] In addition, this embodiment uses Ag paste containing UV-curing resin as the conductive component 2, and the conductive component 2 is cured by irradiation with ultraviolet rays. Therefore, compared with the case of using a conductive paste containing a thermosetting resin and curing it by heat treatment, pattern deformation is reduced, stress generation is also suppressed, and complete transfer can be achieved, thereby greatly shortening the curing time and improving productivity.

[0079] In addition, the present embodiment uses a conductive component 2 made of Ag paste whose average particle size is set to 1 / 5 to 1 / 10 of the minimum line width of the wiring portion 3. Therefore, the shape of the wiring portion 3 formed on the substrate 1 becomes a smooth shape with fewer bumps, thereby alleviating the local electric field concentration between the wiring portions 3 and improving the long-term reliability of the wiring portion 3.

[0080] In addition, in the present embodiment, since the shape of the recessed portion 4a of the transfer mold 4 is formed into a cone (a positive cone), the shape of the wiring portion 3 formed by transfer on the substrate 1 becomes a positive cone, thereby improving the demolding properties of the conductive component 2 from the recessed portion 4a of the transfer mold 4 during transfer, and enabling smooth detachment, thereby improving the yield rate in the conductive component transfer process.

[0081] As described above, the present embodiment is a revolutionary wiring forming method unprecedented in the art that achieves the revolutionary effects described above.

[0082] It should be noted that the present invention is not limited to this embodiment, and the specific structure of each component can be designed appropriately.

Claims

1. A wiring forming method, wherein a conductive component is filled in a concave portion of a transfer mold having a concave portion of a predetermined pattern, the transfer mold filled with the conductive component is overlapped with a surface of a substrate having concave and convex portions, the conductive component is transferred to the surface of the substrate, and a wiring portion is formed on the surface of the substrate using the conductive component, characterized in that: The wiring forming method comprises: a preparation step of preparing the transfer mold having a hardness of 40 to 70 as measured by a type A durometer; and In the pressure-bonding step, after the transfer mold is overlapped with the surface of the substrate, pressure-bonding is performed so that the transfer mold is deformed to follow the projections and recesses, and the surface of the transfer mold is brought into close contact with the surface of the substrate.

2. The wiring forming method according to claim 1, characterized in that: The bumps and depressions are step differences formed by wiring with an aspect ratio of 1 or more arranged on the surface of the substrate, and the crimping process is the following process: after the transfer mold is overlapped with the surface of the substrate, crimping is performed so that the transfer mold is deformed in a manner following the bumps and depressions, so that the surface of the transfer mold is in close contact with the surface of the substrate and the upper surface of the wiring.

3. The wiring forming method according to claim 1, characterized in that: The transfer mold is made of a resin material in which a curing agent is mixed into a main agent having a silicone-based polymer compound as a main component.

4. The wiring forming method according to claim 2, characterized in that: The transfer mold is made of a resin material in which a curing agent is mixed into a main agent having a silicone-based polymer compound as a main component.

5. The wiring forming method according to claim 3, characterized in that: The resin material is formed by mixing the main agent and the hardener in a mixing ratio of 5:

1.

6. The wiring forming method according to claim 4, characterized in that: The resin material is formed by mixing the main agent and the hardener in a mixing ratio of 5:

1.

7. The wiring forming method according to any one of claims 3 to 6, characterized in that: The transfer mold is obtained by placing the resin material on an original plate having convex portions of a predetermined pattern, and then performing pressure molding using a supporting substrate and performing a curing treatment.

8. The wiring forming method according to claim 7, characterized in that: The hardening treatment includes a room temperature hardening treatment in which hardening is performed at room temperature and a heat hardening treatment in which hardening is performed by heating at a temperature of 200° C. or higher.

9. The wiring forming method according to claim 8, characterized in that: The room temperature hardening treatment is performed for more than 24 hours.

10. The wiring forming method according to claim 8, characterized in that: The curing treatment is performed in a room set at 15° C. to 30° C. for 48 hours, and then the heat curing treatment is performed at 200° C. to 250° C. for 30 minutes.

11. The wiring forming method according to claim 9, characterized in that: The curing treatment is performed in a room set at 15° C. to 30° C. for 48 hours, and then the heat curing treatment is performed at 200° C. to 250° C. for 30 minutes.

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