Method for manufacturing laminate

Abstract

The present invention provides a method for manufacturing a laminate in which, when an adhesive sheet is laminated on a wiring board having bumps provided on a surface thereof and the resulting laminate is heat-treated, the bumps will tend not to deform. This method for manufacturing a laminate includes: (a) a step for preparing a wiring board provided with bumps on at least one surface; and (b) a step for laminating, on the surface of the wiring board provided with the bumps, an adhesive sheet provided with a carrier, a peeling layer, and an adhesive layer containing an adhesive material in the stated order. The step of laminating the adhesive sheet on the wiring board includes: (b1) bringing the bumps of the wiring board and the adhesive layer of the adhesive sheet into contact with each other at a vacuum pressure of 3.0 hPa or less to perform first-stage vacuum lamination, and forming a laminate in which the bumps are embedded in the adhesive layer; and (b2) performing second-stage vacuum lamination on the laminate at the vacuum pressure and at a temperature higher than that in the first-stage vacuum lamination.

Description

Manufacturing method of laminate

[0001] The present disclosure relates to a method for manufacturing a laminate.

[0002] In recent years, multilayer printed wiring boards have become widespread in order to increase the packaging density and reduce the size of printed wiring boards. Such multilayer printed wiring boards are used in many portable electronic devices for the purpose of reducing weight and size. However, there is a demand for further reductions in the thickness of interlayer insulating layers and further weight reductions as wiring boards.

[0003] To meet these demands, a coreless build-up method for manufacturing a multilayer printed wiring board has been adopted. The coreless build-up method is a method for forming a multilayer structure by alternately stacking (building up) insulating layers and wiring layers without using a so-called core substrate. In the coreless build-up method, the use of a carrier-attached copper foil has been proposed to facilitate peeling of the support and the multilayer printed wiring board. For example, Patent Document 1 (JP 2005-101137 A) discloses a method for manufacturing a package substrate for mounting a semiconductor element, which includes: attaching an insulating resin layer to the carrier surface of a carrier-attached copper foil to form a support; forming a first wiring conductor on the ultrathin copper layer side of the carrier-attached copper foil through steps such as photoresist processing, patterned electrolytic copper plating, and resist removal; then forming a build-up wiring layer; peeling off the carrier-attached support substrate; and removing the ultrathin copper layer.

[0004] Furthermore, in order to miniaturize embedded circuits as shown in Patent Document 1, a carrier-attached copper foil with an ultrathin copper layer thickness of 1 μm or less is desired. Therefore, in order to achieve a reduced thickness of the ultrathin copper layer, it has been proposed to form the ultrathin copper layer by a vapor phase method such as sputtering. For example, Patent Document 2 (WO 2017 / 150283) discloses a carrier-attached copper foil in which a release layer, an anti-reflection layer, and an ultrathin copper layer are formed by sputtering on a carrier such as glass or ceramics. Furthermore, Patent Document 3 (WO 2017 / 150284) discloses a carrier-attached copper foil in which an intermediate layer (e.g., an adhesion metal layer and a release aid layer), a release layer, and an ultrathin copper layer (e.g., a thickness of 300 nm) are formed by sputtering on a carrier such as glass or ceramics. Patent Documents 2 and 3 also teach that the inclusion of an intermediate layer made of a predetermined metal provides excellent stability in the mechanical peel strength of the carrier, and that the anti-reflection layer exhibits a desirable dark color, thereby improving visibility in image inspection (e.g., automatic image inspection (AOI)).

[0005] In particular, with the further miniaturization and power saving of electronic devices, there is an increasing need for higher integration and thinner semiconductor chips and printed wiring boards. As next-generation packaging technologies to meet such needs, the adoption of fan-out wafer level packaging (FO-WLP) and panel level packaging (PLP) has been considered in recent years. Furthermore, the adoption of a coreless build-up method is also being considered for FO-WLP and PLP. One such method is called the redistribution layer-first (RDL-First) method, in which a wiring layer and, if necessary, a build-up wiring layer are formed on the surface of a coreless support, and the support is further peeled off if necessary, and then the chip is mounted. For example, Patent Document 4 (JP 2015-35551 A) discloses a method for manufacturing a semiconductor device, which includes forming a metal release layer on the main surface of a support made of glass or a silicon wafer, forming an insulating resin layer thereon, forming a redistribution layer including a build-up layer thereon, mounting and sealing a semiconductor integrated circuit thereon, exposing the release layer by removing the support, exposing secondary mounting pads by removing the release layer, forming solder bumps on the surfaces of the secondary mounting pads, and secondary mounting.

[0006] In response to recent technological trends in which the adoption of FO-WLP and PLP is being considered, there is a demand for thinner buildup layers. However, when the buildup layer is thin, the buildup layer may locally bend significantly when peeling the base material from a base material with a buildup layer produced using a coreless buildup method. Such significant curvature of the buildup layer can cause disconnection or peeling of the wiring layer inside the buildup layer, thereby reducing the connection reliability of the wiring layer. To address this problem, it has been proposed to improve handleability by laminating a reinforcing sheet to a multilayer laminate. For example, Patent Document 5 (Japanese Patent No. 6731060) discloses that, in the manufacture of multilayer wiring boards, a reinforcing sheet is laminated to a multilayer wiring layer-containing laminate including a peelable base material via a second release layer that provides a predetermined peel strength. This technique is said to enable the base material and reinforcing sheet to be peeled off in this order without locally causing significant curvature of the multilayer wiring layer. Patent Document 6 (Japanese Patent No. 6731061) discloses laminating a reinforcing sheet having a lower Vickers hardness than a peelable substrate to a multilayer wiring layer laminate, in order to improve the connection reliability of the multilayer wiring layer and the flatness of the multilayer wiring layer surface. Patent Document 7 (Japanese Patent No. 7112962) discloses providing an opening in the reinforcing sheet and using a soluble adhesive layer to laminate the reinforcing sheet to the multilayer laminate. Patent Document 8 (Japanese Patent No. 7208011) discloses using a soluble adhesive layer to laminate the reinforcing sheet to the multilayer laminate, and providing an unoccupied area within a predetermined region where the soluble adhesive layer is not formed. According to the techniques disclosed in Patent Documents 7 and 8, the reinforcing sheet that has served its purpose can be peeled off in an extremely short time by a technique such as dissolution peeling, while minimizing stress on the multilayer laminate.

[0007] Japanese Patent Application Laid-Open No. 2005-101137 International Publication No. 2017 / 150283 International Publication No. 2017 / 150284 Japanese Patent Application Laid-Open No. 2015-35551 Japanese Patent No. 6731060 Japanese Patent No. 6731061 Japanese Patent No. 7112962 Japanese Patent No. 7208011

[0008] Incidentally, mounting bumps (e.g., solder balls) may be provided on the surface of a wiring board equipped with a rewiring layer, etc. From the viewpoint of proceeding with the manufacturing process of the wiring board while protecting such bumps, it would be convenient if a reinforcing adhesive sheet having an adhesive layer on its surface could be laminated on the wiring board so that the bumps are embedded in the adhesive layer. However, when the adhesive sheet is laminated on the wiring board in this manner, voids may occur between the bumps and the adhesive layer, which may cause the bumps to deform during a subsequent heating process (e.g., a reflow process).

[0009] The present inventors have now discovered that when laminating an adhesive sheet onto a wiring substrate having bumps on its surface, by performing two-stage vacuum lamination under conditions of a predetermined vacuum pressure or less, deformation of the bumps is less likely to occur even when the resulting laminate is subjected to a heat treatment.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for producing a laminate in which deformation of the bumps is unlikely to occur when an adhesive sheet is laminated on a wiring board having bumps on its surface and subjected to a heat treatment.

[0011] The present disclosure provides the following aspects. [Aspect 1] A method for producing a laminate, comprising: (a) preparing a wiring substrate having bumps on at least one surface; and (b) laminating an adhesive sheet having, in this order, a carrier, a release layer, and an adhesive layer containing an adhesive material on the surface of the wiring substrate having the bumps, the adhesive sheet comprising: (b1) performing a first-stage vacuum lamination by bringing the bumps on the wiring substrate and the adhesive layer of the adhesive sheet into contact with each other at a vacuum pressure of 3.0 hPa or less to form a laminate in which the bumps are embedded in the adhesive layer, and (b2) performing a second-stage vacuum lamination of the laminate at the vacuum pressure but at a temperature higher than that of the first-stage vacuum lamination. [Aspect 2] The method for producing a laminate according to Aspect 1, further comprising: (c) curing the adhesive layer after step (b) of laminating the adhesive sheet on the wiring substrate. [Aspect 3] A method for producing a laminate according to Aspect 2, further comprising, after step (c) of curing the adhesive layer, (d) a step of heat treating the laminate at a temperature higher than that of the second-stage vacuum lamination. [Aspect 4] A method for producing a laminate according to any one of Aspects 1 to 3, wherein the first-stage vacuum lamination is performed at a temperature of 60°C or higher and lower than 200°C, a pressure of 0.10 MPa or higher, and a pressurization time of 10 seconds to 600 seconds. [Aspect 5] A method for producing a laminate according to any one of Aspects 1 to 4, wherein the second-stage vacuum lamination is performed at a temperature of 150°C or higher and 200°C or lower, a pressure of 0.10 MPa or higher, and a pressurization time of 10 seconds to 600 seconds. [Aspect 6] A method for producing a laminate according to any one of Aspects 1 to 5, wherein the bumps are solder balls having a diameter of 10 μm to 1000 μm and a height of 10 μm to 1000 μm. [Aspect 7] The method for manufacturing a laminate according to any one of Aspects 1 to 6, wherein the bumps are regularly arranged at a pitch (center-to-center distance) of 30 μm or more and 1000 μm or less. [Aspect 8] The method for manufacturing a laminate according to any one of Aspects 1 to 7, wherein the carrier has a Poisson's ratio of 0.15 or more and 0.50 or less. [Aspect 9] The method for manufacturing a laminate according to any one of Aspects 1 to 8, wherein the carrier is made of metal.[Aspect 10] The method for producing a laminate according to any one of Aspects 1 to 9, wherein the carrier is at least one selected from aluminum and aluminum alloys, stainless steel, copper and copper alloys, titanium and titanium alloys, and nickel and nickel alloys. [Aspect 11] The method for producing a laminate according to any one of Aspects 1 to 10, wherein the adhesive material is at least one selected from the group consisting of thermosetting epoxy resins, thermosetting polyimide resins, acrylic resins, and phenolic resins. [Aspect 12] The method for producing a laminate according to any one of Aspects 1 to 11, wherein the adhesive layer has a thickness of 1 μm or more and 2000 μm or less. [Aspect 13] The planar area A of the carrier. Ｃ The planar area A of the adhesive layer Ａ Ratio A Ａ / A Ｃ A method for producing a laminate according to any one of Aspects 1 to 12, wherein the value of the release layer is 0.03 or more and 1.0 or less. [Aspect 14] A method for producing a laminate according to any one of Aspects 1 to 13, wherein the release layer contains carbon. [Aspect 15] A method for producing a laminate according to any one of Aspects 1 to 14, wherein the adhesive sheet further comprises a metal layer provided between the release layer and the adhesive layer.

[0012] FIG. 1 is a process flow diagram showing, in schematic cross-sectional views, an example of a method for producing a laminate of the present invention. FIG. 2 is a schematic cross-sectional view showing one embodiment of a wiring board used in the present invention. FIG. 3 is a schematic cross-sectional view for explaining the mechanism by which bump deformation occurs due to voids present between the bump and the adhesive layer. FIG. 4 is a cross-sectional optical microscope image (magnification: 100x) of the laminate after curing treatment in Example A1 (comparison). FIG. 5 is a cross-sectional optical microscope image (magnification: 100x) of the laminate after curing treatment in Example A6. FIG. 6 is a cross-sectional optical microscope image (magnification: 100x) of the laminate after heat treatment in Example A1 (comparison). FIG. 7 is a cross-sectional optical microscope image (magnification: 100x) of the laminate after heat treatment in Example A6. FIG. 8 is a SEM image (magnification: 300x) of the surface of a solder ball after peeling off the adhesive sheet in Example A1 (comparison). FIG. 9 is a SEM image (magnification: 300x) of the surface of a solder ball after peeling off the adhesive sheet in Example A2 (comparison). FIG. 10 is a SEM image (magnification: 300x) of the surface of a solder ball after peeling off the adhesive sheet in Example A4 (comparison). 1 is a SEM image (magnification: 300x) of the surface of the solder ball after peeling off the adhesive sheet in Example A6.

[0013] The present invention relates to a method for manufacturing a laminate. The method of the present invention includes the steps of (1) preparing a wiring substrate, (2) laminating an adhesive sheet onto the wiring substrate, (3) optionally curing the adhesive layer, (4) optionally heat-treating the laminate, and (5) optionally removing the adhesive sheet. Each of steps (1) to (5) will be described below with reference to the drawings.

[0014] (1) Preparation of Wiring Board An example of a method for manufacturing a laminate according to the present invention is shown in Figure 1. First, as shown in Figure 1(i), a wiring board 10 having bumps 12 on at least one surface is prepared. The bumps 12 may be provided on only one surface of the wiring board 10, or may be provided on both surfaces of the wiring board 10.

[0015] The wiring substrate 10 may be manufactured by any method. An example of a preferred embodiment of the wiring substrate 10 of the present invention is shown in FIG. 2. As shown in FIG. 2, the wiring substrate 10 preferably includes a rewiring layer 10a, and bumps 12 are provided on the rewiring layer 10a. In the present invention, the rewiring layer refers to a layer including an insulating layer and a wiring layer formed inside and / or on the surface of the insulating layer. The wiring substrate 10 may also include a molded resin layer 10b and a second rewiring layer 10c provided on the molded resin layer 10b. The molded resin layer 10b is typically provided on the surface of the rewiring layer 10a opposite to the surface on which the bumps 12 are provided. The molded resin layer 10b is a layer containing a resin for encapsulating electronic elements such as chips. Therefore, the molded resin layer 10b can embed electronic elements. Examples of electronic elements include semiconductor elements, chip capacitors, resistors, etc. Preferred examples of the resin contained in the molded resin layer 10b include epoxy resin and phenolic resin.

[0016] The rewiring layer 10a, the molded resin layer 10b, and the second rewiring layer 10c can be formed according to known techniques. For example, the rewiring layer 10a is obtained by forming a wiring layer and an insulating layer using a carrier-attached metal foil as disclosed in Patent Document 2 (WO 2017 / 150283) and Patent Document 3 (WO 2017 / 150284) by a coreless build-up method. Specifically, a photoresist is laminated on the metal foil of the carrier-attached metal foil, and then exposed and developed to form a predetermined pattern to form a resist pattern. Then, electroplating (e.g., copper electroplating) is performed between the resist patterns. After the resist pattern is peeled off, unnecessary portions of the metal foil exposed by the peeling of the resist pattern (i.e., portions that do not form a wiring pattern) are removed by etching to form the first wiring layer. Then, insulating layers and n-th wiring layer (n is an integer of 2 or greater) are alternately formed on the surface of the carrier-attached metal foil on which the first wiring layer is formed. In this way, a rewiring layer 10a including an insulating layer and a wiring layer formed inside and / or on the insulating layer can be obtained. As shown in FIG. 2, not only the bumps 12 but also an integrated passive device I and the like may be mounted on the rewiring layer 10a.

[0017] After forming the rewiring layer 10a, if desired, pillars (columnar electrodes) P may be formed on the rewiring layer 10a, chips C may be mounted, and the pillars P and chips C may be embedded in insulating resin to form a molded resin layer 10b. At this time, the surface of the molded resin layer 10b may be polished to expose the pillars P and chips C from the molded resin layer 10b. Preferred examples of surface polishing include grinding using a grindstone and chemical mechanical polishing (CMP). Then, a second rewiring layer 10c can be formed on the surface of the molded resin layer 10b by the coreless build-up method described above. If desired, before the step of laminating the adhesive sheet 20 described below, as shown in FIG. 2, a reinforcing sheet 50 may be laminated on the wiring substrate 10 (e.g., on the surface opposite to the surface on which the adhesive sheet 20 is laminated). This further improves the handleability of the wiring substrate 10. The reinforcing sheet 50 may have a configuration similar to that of the adhesive sheet 20 described below, and includes, for example, a carrier 52 , an intermediate layer 54 , a release layer 56 , a metal layer 58 and an adhesive layer 60 .

[0018] The thickness of the wiring substrate 10 is not particularly limited, but is preferably 150 μm or more and 3000 μm or less, more preferably 170 μm or more and 2000 μm or less, and even more preferably 180 μm or more and 1600 μm or less. The size of the wiring substrate 10 is not particularly limited, but is preferably a disk shape with a diameter of 100 mm or more, more preferably a disk shape with a diameter of 200 mm or more and 450 mm or less. According to another preferred embodiment of the present invention, the wiring substrate 10 is a rectangle with short sides of 100 mm or more, more preferably a rectangle with short sides of 150 mm or more and 600 mm or less and long sides of 200 mm or more and 650 mm or less.

[0019] The bumps 12 are typically components for mounting the wiring substrate 10 to another wiring substrate, etc. For this reason, the bumps 12 are preferably solder bumps, more preferably solder balls. The solder balls preferably have a diameter of 10 μm to 1000 μm, more preferably 50 μm to 800 μm, and even more preferably 100 μm to 500 μm. The solder balls also preferably have a height of 10 μm to 1000 μm, more preferably 50 μm to 800 μm, and even more preferably 100 μm to 500 μm. The bumps 12 are preferably regularly arranged on the surface of the wiring substrate 10 at a pitch (center-to-center distance) of 30 μm to 1000 μm, more preferably 50 μm to 800 μm, and even more preferably 100 μm to 500 μm. The solder constituting the solder ball may be a known solder used for printed wiring boards, etc., and is not particularly limited, but is typically made of a metal or alloy containing Sn. The bumps 12 can be formed by any known method, and are not particularly limited. If necessary, a solder resist may be formed on the surface of the wiring substrate 10 (e.g., the rewiring layer 10a).

[0020] (2) Lamination of Adhesive Sheet to Wiring Board As shown in Figures 1(ii) and (iii), an adhesive sheet 20 is laminated on the surface of the wiring board 10 that has the bumps 12. In this process, a two-stage vacuum lamination is performed, as described below. The adhesive sheet 20 comprises, in this order, a carrier 22, a release layer 26, and an adhesive layer 30 containing an adhesive material. Optionally, the adhesive sheet 20 may further comprise an intermediate layer 24 between the carrier 22 and the release layer 26, or may further comprise a metal layer 28 between the release layer 26 and the adhesive layer 30. Preferred embodiments of the adhesive sheet 20 will be described below.

[0021] (2-1) First-Stage Vacuum Lamination As shown in Figure 1(ii), the bumps 12 of the wiring substrate 10 and the adhesive layer 30 of the adhesive sheet 20 are brought into contact with each other to perform the first-stage vacuum lamination. By doing so, it is possible to obtain a laminate 40 in which the bumps 12 are embedded in the adhesive layer 30, as shown in Figure 1(iii). Vacuum lamination can be preferably performed, for example, by using a commercially available vacuum laminator, placing the wiring substrate 10 and the adhesive sheet 20 in a chamber, evacuating the chamber with a vacuum pump to achieve a predetermined vacuum level, and bonding the wiring substrate 10 and the adhesive sheet 20 together at a predetermined temperature and pressure.

[0022] The first stage of vacuum lamination is performed at a vacuum pressure of 3.0 hPa or less, preferably 2.5 hPa or less, more preferably 2.0 hPa or less, and even more preferably 1.0 hPa or less. Since a lower vacuum pressure is preferable, the lower limit is not particularly limited, but is typically 0.5 hPa or more. Note that the vacuum pressure varies depending on the temperature of the chamber, so the numerical value of the vacuum pressure in this specification refers to the vacuum pressure at the highest temperature of vacuum lamination (typically the temperature during the second stage of vacuum lamination).

[0023] The first-stage vacuum lamination is preferably performed at a temperature of 60°C or higher but lower than 200°C, more preferably 80°C or higher but lower than 190°C, and even more preferably 90°C or higher but lower than 180°C. This vacuum lamination is preferably performed at a pressure (pressing pressure) of 0.10 MPa or higher, more preferably 0.20 MPa or higher, and even more preferably 0.30 MPa or higher. The upper limit of the pressing pressure is not particularly limited, but is typically 1.5 MPa or lower, and more typically 1.0 MPa or lower. This vacuum lamination is preferably performed for a pressing time of 10 seconds or higher but lower than 600 seconds, more preferably 30 seconds or higher but lower than 550 seconds, and even more preferably 60 seconds or higher but lower than 500 seconds. This allows the bumps 12 to be more reliably embedded in the adhesive layer 30.

[0024] If only the first-stage vacuum lamination is performed without the second-stage vacuum lamination described below, voids V may exist between the bumps 12 and the adhesive layer 30 after lamination (e.g., at the base of the bumps 12), as shown in FIG. 3(i). These voids V may be, for example, bubbles generated from the adhesive material constituting the adhesive layer 30 or bubbles resulting from gaps formed when bonding the adhesive sheet 20 to the wiring substrate 10. If a high-temperature heat treatment (e.g., 260°C) is performed on the laminate 40 while such voids V are present, deformation of the bumps 12 may occur, as shown in FIG. 3(ii). In other words, the gas in the voids V expands due to the high temperature, pressurizing the bumps 12, which may result in chipping or other defects in the bumps 12.

[0025] (2-2) Second-Stage Vacuum Lamination The laminate 40 obtained in the first-stage vacuum lamination is subjected to a second-stage vacuum lamination. At this time, the second-stage vacuum lamination is performed at a temperature higher than that of the first-stage vacuum lamination. By doing so, air bubbles (voids V) that may exist between the bumps 12 and the adhesive layer 30 can be expelled to the outside of the adhesive layer 30. As a result, deformation of the bumps 12 can be effectively suppressed even when the laminate 40 is subjected to a heat treatment such as reflow.

[0026] The second-stage vacuum lamination is performed at a vacuum pressure of 3.0 hPa or less, as in the first stage, preferably 2.5 hPa or less, more preferably 2.0 hPa or less, and even more preferably 1.0 hPa or less. This allows air bubbles that may exist between the bumps 12 and the adhesive layer 30 to be more effectively expelled to the outside of the adhesive layer 30. Since a lower vacuum pressure is preferable, the lower limit is not particularly limited, but is typically 0.5 hPa or more. The second-stage vacuum lamination may be performed using the same equipment as the first-stage vacuum lamination, or may be performed using a different equipment. For example, the first-stage vacuum lamination may be performed using a commercially available vacuum laminator with the chamber maintained at a predetermined vacuum level, and then the chamber temperature may be increased and the second-stage vacuum lamination may be performed subsequently.

[0027] The second-stage vacuum lamination is preferably performed at a temperature of 150°C to 200°C, more preferably 160°C to 190°C, and even more preferably 170°C to 180°C. The second-stage vacuum lamination temperature is higher than the first-stage vacuum lamination temperature. This vacuum lamination is preferably performed at a pressure (pressing pressure) of 0.10 MPa or more, more preferably 0.20 MPa or more, and even more preferably 0.30 MPa or more. The upper limit of the pressing pressure is not particularly limited, but is typically 1.5 MPa or less, and more typically 1.0 MPa or less. This vacuum lamination is preferably performed for a pressurizing time of 10 seconds to 600 seconds, more preferably 30 seconds to 550 seconds, and even more preferably 60 seconds to 500 seconds. This allows air bubbles that may be present between the bumps 12 and the adhesive layer 30 to be more effectively expelled to the outside of the adhesive layer 30.

[0028] (3) Curing of Adhesive Layer (Optional Step) If desired, the adhesive layer 30 in the laminate 40 is cured. This ensures that the bumps 12 are protected by the adhesive layer 30. The curing process may be appropriately determined depending on the adhesive material constituting the adhesive layer 30, and is not particularly limited. For example, if the adhesive layer 30 is made of a thermosetting resin, the laminate 40 may be heated at a temperature and for a time period that allows the adhesive layer 30 to completely cure (i.e., reach the C-stage). As an example, the curing process is preferably performed at a temperature of 60°C or higher and 250°C or lower, more preferably at a temperature of 80°C or higher and 230°C or lower. Furthermore, this heating process is preferably performed for a heating time of 15 minutes or higher and 300 minutes or lower, more preferably for a heating time of 30 minutes or higher and 200 minutes or lower.

[0029] When the adhesive layer 30 is made of a thermosetting resin, it is permissible for the adhesive layer 30 to be partially cured (i.e., to be in a B-stage state) by the second vacuum lamination step described above. In other words, unless the adhesive layer 30 is completely cured, the adhesive layer 30 has a certain degree of fluidity, and therefore, any air bubbles that may exist between the bumps 12 and the adhesive layer 30 can be expelled to the outside.

[0030] (4) Heat Treatment of Laminate (Optional Step) If desired, the cured laminate 40 is subjected to a heat treatment at a temperature higher than that of the second-stage vacuum lamination. An example of such a heat treatment is reflow. The heat treatment is preferably performed at a temperature of 240°C or higher and 260°C or lower. Furthermore, this heat treatment is preferably performed for a heating time of 1 minute or longer. According to the method of the present invention, the bumps 12 are embedded in the adhesive layer 30 by the above-described two-stage vacuum lamination, and air bubbles (voids V) between the bumps 12 and the adhesive layer 30 are also preferably removed. Therefore, even when a heat treatment is performed at such a high temperature, deformation of the bumps 12 can be effectively suppressed.

[0031] The method of the present invention may further include various known processes for transforming the wiring substrate 10 into a final product before or after the heat treatment of the laminate 40. For example, if the wiring substrate 10 includes a rewiring layer 10a, a molded resin layer 10b, and a second rewiring layer 10c as shown in FIG. 2, the method may further include a process of mounting an electronic element such as a chip on the second rewiring layer 10c after peeling off the reinforcing sheet 50 (if present). This allows for improved integration by stacking multiple IC packages on the substrate, along with the chip C that may be embedded in the molded resin layer 10b. Furthermore, because the adhesive sheet 20 reinforces the wiring substrate 10 and the bumps 12 are embedded in the adhesive layer 30, even when various processes are performed on the laminate 40, it is possible to effectively prevent the wiring substrate 10 (e.g., the rewiring layer) from curving significantly locally and the bumps 12 from deforming.

[0032] (5) Removal of Adhesive Sheet (Optional Step) If desired, after various steps have been performed, the adhesive sheet 20 that has completed its function may be removed from the laminate 40. To remove the adhesive sheet 20, first, the carrier 22 (and the intermediate layer 24, if present) is peeled off at the location of the release layer 26. The carrier 22 may be peeled off by a physical method or by laser lift-off (laser lift-off, LLO). A physical method is a method in which the carrier 22 is separated by peeling it off from the laminate 40 by hand, a jig, a machine, or the like.

[0033] Next, the release layer 26 (and the metal layer 28, if present) is removed from the laminate 40 from which the carrier 22 has been peeled, thereby exposing the adhesive layer 30. The method for removing the release layer 26 is not particularly limited, and a known method may be appropriately selected depending on the material of the release layer 26, etc. For example, if the release layer 26 is a carbon layer, the release layer 26 can be preferably removed by performing oxygen plasma treatment on the laminate 40. In cases where the adhesive sheet 20 has a metal layer 28 and only a small amount of the release layer 26 remains on the laminate 40, the release layer 26 and the metal layer 28 may be removed simultaneously instead of removing the release layer 26 alone. In other words, the metal layer 28 can be removed first, and then the release layer 26 can be removed at the same time. The metal layer 28 can be removed, for example, by contacting the laminate 40 with an etching solution capable of dissolving the metal layer 28.

[0034] The adhesive layer 30 is removed from the laminate 40 from which the release layer 26 and the like have been removed. The method for removing the adhesive layer 30 is not particularly limited, and a known method may be appropriately selected depending on the material and the like of the adhesive layer 30. For example, the adhesive layer 30 can be removed by bringing it into contact with a solution capable of dissolving the adhesive layer 30, thereby dissolving or softening the adhesive layer 30.

[0035] Adhesive Sheet As shown in FIG. 1( ii ), the adhesive sheet 20 used in the method for producing a laminate of the present invention comprises a carrier 22, a release layer 26, and an adhesive layer 30, in this order. The release layer 26 is provided on the carrier 22. The adhesive layer 30 is provided on the release layer 26 and contains an adhesive material. The adhesive sheet 20 preferably further comprises a metal layer 28 between the release layer 26 and the adhesive layer 30. Optionally, the adhesive sheet 20 may further comprise an intermediate layer 24 between the carrier 22 and the release layer 26. Each of the intermediate layer 24, the release layer 26, the metal layer 28, and the adhesive layer 30 may be a single layer composed of one layer, or a multilayer composed of two or more layers.

[0036] The adhesive layer 30 is preferably a layer that can attach the adhesive sheet 20 to the wiring board 10 with the desired adhesion and that can be removed from the wiring board 10 after use. The manner of adhesion between the adhesive sheet 20 and the wiring board 10 via the adhesive layer 30 is not particularly limited, and may be, for example, a mechanical bond (i.e., adhesion due to the anchor effect), a physical interaction (i.e., adhesion due to van der Waals forces), a chemical bond, or the like. Examples of adhesive materials contained in the adhesive layer 30 include phenolic resin, urea resin, melamine resin, epoxy resin, polyimide resin, ethylene-vinyl acetate copolymer resin (EVA), urethane resin, acrylic resin, synthetic rubber, and starch. Preferably, the adhesive material is a thermosetting epoxy resin, a thermosetting polyimide resin, a photosensitive polyimide resin, an acrylic resin, a phenolic resin, or a combination thereof. More preferably, the adhesive material is a thermosetting epoxy resin, a thermosetting polyimide resin, an acrylic resin, a phenolic resin, or a combination thereof.

[0037] The adhesive sheet 20 is used as a reinforcing sheet for the wiring substrate 10, which is subjected to the above-mentioned high-temperature heat treatment (e.g., at 260°C for several minutes). Therefore, it is preferable that the adhesive layer 30 be able to retain its adhesiveness even after undergoing such heat treatment and be removable after use. From this perspective, it is preferable that the adhesive material contain a thermosetting resin. Preferred examples of thermosetting resins include thermosetting epoxy resins, thermosetting polyimide resins, thermosetting phenolic resins, thermosetting melamine resins, and combinations thereof, with thermosetting epoxy resins being more preferred. Examples of adhesive layer products containing thermosetting epoxy resins include TSA-1602 and TSA-16 manufactured by Toray Industries, Inc.

[0038] The adhesive layer 30 preferably has a thickness of 1 μm or more and 2000 μm or less, more preferably 3 μm or more and 1000 μm or less, even more preferably 5 μm or more and 800 μm or less, and particularly preferably 10 μm or more and 500 μm or less. With such a thickness, it is easy to control the adhesion to the wiring substrate 10 within a desired range, and the adhesive sheet 20 can be peeled off and removed in a short time after use as a reinforcing sheet, etc. Furthermore, from the viewpoint of embedding the entire bump 12 in the adhesive layer 30, it is preferable that the thickness of the adhesive layer 30 be equal to or greater than the height of the bump 12.

[0039] The adhesive layer 30 not only exhibits adhesive properties at room temperature, but is also preferably a layer that can be dissolved or softened upon contact with a solvent. Therefore, the adhesive layer 30 preferably contains a solution-soluble resin, such as an acid-soluble resin or an alkali-soluble resin. This solution-soluble resin can be efficiently dissolved or softened upon contact with a solvent, allowing the adhesive layer 30 to be removed more quickly. In particular, the adhesive layer 30 preferably contains an alkali-soluble resin. Preferred examples of alkali-soluble resins include the thermosetting resins described above.

[0040] The method for forming the adhesive layer 30 is not particularly limited, and any known method can be used. For example, the adhesive layer 30 can be formed by applying a coating liquid in which an adhesive material is dissolved in a solvent onto the release layer 26 (or the metal layer 28, if present), and then drying to volatilize the solvent. Alternatively, a commercially available adhesive film may be placed on the release layer 26 (or the metal layer 28, if present), and then the layers may be attached by roll lamination, vacuum lamination, or another method.

[0041] The adhesive sheet 20 has a planar area A Ｃ The planar area A of the adhesive layer 30 Ａ Ratio A Ａ / A Ｃ is preferably 0.03 or more and 1.0 or less, more preferably 0.05 or more and 0.95 or less, even more preferably 0.08 or more and 0.93 or less, and particularly preferably 0.10 or more and 0.90 or less. Ｃ and A Ａ The areas respectively refer to the area of ​​the carrier 22 and the area of ​​the adhesive layer 30 when the adhesive sheet 20 is viewed in plan view. By forming the adhesive layer 30 to be sufficiently large relative to the carrier 22 in this way, the adhesive sheet 20 can be stably and reliably adhered to the wiring substrate 10. Even so, after the carrier 22 is peeled off, the adhesive sheet 20 can be brought into contact with a dissolving solution or the like with most or all of the surface of the adhesive layer 30 exposed, and therefore the adhesive layer 30 can be removed in a short time.

[0042] Typically, the carrier 22 functions to reinforce the wiring substrate 10 and improve its handleability when the adhesive sheet 20 is laminated on the wiring substrate 10. The carrier 22 preferably has a Poisson's ratio of 0.15 to 0.50, more preferably 0.27 to 0.40, and even more preferably 0.29 to 0.35. This allows the adhesive sheet 20 to bend to conform to the irregularities of the wiring substrate 10, making it easier to bond to the wiring substrate 10, even if the wiring substrate 10 has large irregularities due to distortion of the bumps 12 or the wiring substrate 10 itself. As a result, the intrusion of air bubbles between the bumps 12 and the adhesive layer 30 during lamination of the adhesive sheet 20 on the wiring substrate 10 can be effectively prevented, and the adhesive sheet 20 can more reliably reinforce the wiring substrate 10. In the present invention, the Poisson's ratio refers to a value measured and calculated in accordance with JIS Z 2241:2011.

[0043] The carrier 22 is preferably made of metal in view of the above-mentioned Poisson's ratio. Preferred examples of metals constituting the carrier 22 include aluminum and aluminum alloys (e.g., duralumin (e.g., A2017, A2024, and A7075 in JIS standards)), stainless steel, copper and copper alloys (e.g., bronze, phosphor copper, copper-nickel alloy, copper-titanium alloy, etc.), titanium and titanium alloys, and nickel and nickel alloys. The carrier 22 may also be made of glass. Preferred examples of glass constituting the carrier 22 include quartz glass, borosilicate glass, alkali-free glass, soda-lime glass, and aluminosilicate glass.

[0044] The form of the carrier 22 is not limited to a sheet, and may be in other forms such as a film, plate, or foil, as long as it can prevent or suppress curvature of the wiring substrate 10. The carrier 22 may be a laminate of these sheets, films, plates, and foils. From the viewpoints of maintaining the strength of the carrier 22 and making it easy to handle, the thickness of the carrier 22 is preferably 10 μm to 3 mm, more preferably 10 μm to 1 mm, even more preferably 50 μm to 800 μm, and particularly preferably 100 μm to 600 μm. Among these, when the carrier 22 is made of glass, the thickness of the carrier 22 is preferably 300 μm to 3 mm, more preferably 400 μm to 2 mm, and even more preferably 500 μm to 1.8 mm. Furthermore, when the carrier 22 is made of metal, the thickness of the carrier 22 is preferably 100 μm or more and 1 mm or less, more preferably 150 μm or more and 900 μm or less, and even more preferably 200 μm or more and 600 μm or less. When the carrier 22 is a metal sheet (e.g., a stainless steel sheet), the ten-point mean roughness Rz-JIS (measured in accordance with JIS B 0601-2001) of the surface of the metal sheet on which the release layer 26 (or intermediate layer 24, if present) is formed is preferably 0.05 μm or more and 500 μm or less, more preferably 0.5 μm or more and 400 μm or less, and even more preferably 1 μm or more and 300 μm or less. With such a surface roughness, the anchor effect caused by the surface irregularities makes it easier to control the peel strength between the carrier and the adhesive layer to a desired value.

[0045] The optional intermediate layer 24 is interposed between the carrier 22 and the release layer 26 and contributes to ensuring adhesion between the carrier 22 and the release layer 26. Examples of metals constituting the intermediate layer 24 include Cu, Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, In, Sn, Zn, Ga, Mo, and combinations thereof (hereinafter sometimes referred to as metal M). Preferred are Cu, Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, Mo, and combinations thereof. More preferred are Cu, Ti, Zr, Al, Cr, W, Ni, Mo, and combinations thereof. Even more preferred are Cu, Ti, Al, Cr, Ni, Mo, and combinations thereof. Particularly preferred are Cu, Ti, Al, Ni, and combinations thereof. The intermediate layer 24 may be a pure metal or an alloy. The metal constituting the intermediate layer 24 may contain impurities resulting from the raw material components, the film formation process, etc. Furthermore, although not particularly limited, if the intermediate layer 24 is exposed to the atmosphere after formation, the presence of oxygen due to this is acceptable. The upper limit of the metal content is not particularly limited and may be 100 atomic %. The intermediate layer 24 is preferably a layer formed by physical vapor deposition (PVD), more preferably a layer formed by sputtering. From the viewpoint of uniformity of film thickness distribution, the intermediate layer 24 is particularly preferably a layer formed by magnetron sputtering using a metal target. The thickness of the intermediate layer 24 is preferably 10 nm to 1000 nm, more preferably 30 nm to 800 nm, even more preferably 60 nm to 600 nm, and particularly preferably 100 nm to 400 nm. By achieving such a thickness, it is possible to obtain an intermediate layer having a roughness equivalent to that of the carrier. This thickness is a value measured by analyzing a cross section of the layer with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0046] The intermediate layer 24 may have a single layer structure or a structure of two or more layers. When the intermediate layer 24 has a single layer structure, it is preferably a layer containing a metal such as Cu, Al, Ti, Ni, or a combination thereof (e.g., an alloy or an intermetallic compound), more preferably Al, Ti, or a combination thereof (e.g., an alloy or an intermetallic compound), and even more preferably a layer containing primarily Al or a layer containing primarily Ti. On the other hand, when a metal or alloy that does not have sufficiently high adhesion to the carrier 22 is used for the intermediate layer 24, it is preferable for the intermediate layer 24 to have a two-layer structure. An example of a preferred two-layer structure for the intermediate layer 24 is a laminate structure consisting of a Ti-containing layer adjacent to the carrier 22 and a Cu-containing layer adjacent to the release layer 26. Furthermore, changing the balance of the constituent elements and thicknesses of each layer in the two-layer structure also changes the peel strength, so it is preferable to appropriately adjust the constituent elements and thicknesses of each layer. In this specification, the term "metal M-containing layer" also includes alloys containing elements other than metal M, as long as they do not impair the releasability of the carrier. Therefore, the intermediate layer 24 can also be said to be a layer mainly containing the metal M. From the above points of view, the content of the metal M in the intermediate layer 24 is preferably 50 atomic % or more and 100 atomic % or less, more preferably 60 atomic % or more and 100 atomic % or less, even more preferably 70 atomic % or more and 100 atomic % or less, particularly preferably 80 atomic % or more and 100 atomic % or less, and most preferably 90 atomic % or more and 100 atomic % or less.

[0047] When the intermediate layer 24 is made of an alloy, a preferred example of the alloy is a Ni alloy. The Ni alloy preferably has a Ni content of 45% by weight or more and 98% by weight or less, more preferably 55% by weight or more and 90% by weight or less, and even more preferably 65% ​​by weight or more and 85% by weight or less. A preferred Ni alloy is an alloy of Ni and at least one selected from the group consisting of Cr, W, Ta, Co, Cu, Ti, Zr, Si, C, Nd, Nb, and La, and more preferably an alloy of Ni and at least one selected from the group consisting of Cr, W, Cu, and Si. When the intermediate layer 24 is a Ni alloy layer, it is particularly preferred that the layer be formed by magnetron sputtering using a Ni alloy target in terms of uniformity of film thickness distribution.

[0048] The release layer 26 is a layer that enables or facilitates the release of the carrier 22 and, if present, the intermediate layer 24. The release layer 26 may be removable by physical force or by laser lift-off (LLO). When the release layer 26 is made of a material that can be removed by laser lift-off, it may be made of a resin whose interfacial adhesive strength decreases upon irradiation with a laser beam after curing, or it may be a layer of silicon, silicon carbide, metal oxide, or the like that is modified by laser irradiation. The release layer 26 may be either an organic or inorganic release layer, but is preferably an inorganic release layer from the perspective of heat resistance. Examples of organic components used in organic release layers include nitrogen-containing organic compounds, sulfur-containing organic compounds, carboxylic acids, etc. Examples of nitrogen-containing organic compounds include triazole compounds and imidazole compounds. On the other hand, examples of inorganic components used in the inorganic release layer include metal oxides or metal oxynitrides containing at least one of Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, Cu, Al, Nb, Zr, Ta, Ag, In, Sn, and Ga, or carbon layers. Among these, the release layer 26 preferably contains carbon. From the viewpoints of ease of release and film formability, it is more preferable to use a carbon-containing layer, i.e., a layer primarily containing carbon, even more preferably a layer primarily composed of carbon or hydrocarbons, and particularly preferably a layer composed of amorphous carbon, which is a hard carbon film. In this case, the release layer 26 (i.e., the carbon-containing layer) preferably has a carbon concentration of 60 atomic % or more, more preferably 70 atomic % or more, even more preferably 80 atomic % or more, and particularly preferably 85 atomic % or more, as measured by XPS. The upper limit of the carbon concentration is not particularly limited and may be 100 atomic %, but 98 atomic % or less is practical. The release layer 26 may contain impurities (e.g., oxygen, hydrogen, etc. derived from the surrounding environment such as the atmosphere). Furthermore, the release layer 26 may contain metal atoms of types other than the metal contained in the release layer 26 due to the film formation method of the metal layer 28, etc.When a carbon-containing layer is used as the release layer 26, it exhibits low interdiffusibility and reactivity with the carrier. Even when subjected to press processing or the like at temperatures exceeding 300°C, it is possible to prevent the formation of a metallic bond between the metal layer (if present) and the bonding interface due to high-temperature heating, thereby maintaining a state in which the carrier can be easily peeled off and removed. This release layer 26 is also preferably formed by a vapor-phase method such as sputtering, in terms of suppressing excessive impurities in the release layer 26 and facilitating continuous production with the formation of the optional intermediate layer 24. When a carbon-containing layer is used as the release layer 26, its thickness is preferably 1 nm or more and 20 nm or less, and more preferably 1 nm or more and 10 nm or less. This thickness allows for a release layer with the same roughness as the carrier and capable of peeling. This thickness is measured by analyzing the layer cross section using a transmission electron microscope with an energy-dispersive X-ray spectrometer (TEM-EDX).

[0049] The release layer 26 may include a metal oxide layer and a carbon-containing layer, or may be a layer containing both a metal oxide and carbon. In particular, when the adhesive sheet 20 includes an intermediate layer 24 and a metal layer 28, the carbon-containing layer contributes to stable release of the carrier 22, while the metal oxide layer suppresses the diffusion of metal elements derived from the intermediate layer 24 and the metal layer 28 due to heating. As a result, stable release properties can be maintained even after heating at high temperatures, such as 350°C or higher. The metal oxide layer is preferably a layer containing a metal oxide composed of Cu, Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, In, Sn, Zn, Ga, Mo, or a combination thereof. The metal oxide layer is preferably formed by reactive sputtering, which involves sputtering a metal target under an oxidizing atmosphere, because the film thickness can be easily controlled by adjusting the film formation time. The thickness of the metal oxide layer is preferably 0.1 nm or more and 100 nm or less. The upper limit of the thickness of the metal oxide layer is more preferably 60 nm or less, even more preferably 30 nm or less, and particularly preferably 10 nm or less. This thickness is a value measured by analyzing the cross section of the layer using a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX). In this case, the order in which the metal oxide layer and the carbon layer are laminated as the release layer 26 is not particularly limited. Furthermore, the release layer 26 may exist in a mixed phase state (i.e., a layer containing both metal oxide and carbon) in which the boundary between the metal oxide layer and the carbon-containing layer is not clearly defined.

[0050] Similarly, from the viewpoint of maintaining stable releasability even after heat treatment at high temperatures, the release layer 26 may be a metal-containing layer whose surface adjacent to the adhesive layer 30 (or the metal layer 28, if present) is a fluoride-treated surface and / or a nitride-treated surface. The metal-containing layer preferably has a region (hereinafter referred to as "(F+N) region") in which the sum of the fluorine content and the nitrogen content is 1.0 atomic % or more, present over a thickness of 10 nm or more, and the (F+N) region preferably exists on the adhesive layer 30 side of the metal-containing layer. The thickness of the (F+N) region (SiO ２The "density" (converted to atomic percent) is a value determined by performing depth direction elemental analysis of the adhesive sheet 20 using XPS. The fluoride-treated surface or nitride-treated surface can be preferably formed by reactive ion etching (RIE) or reactive sputtering. On the other hand, the metal element contained in the metal-containing layer preferably has a negative standard electrode potential. Preferred examples of the metal element contained in the metal-containing layer include Cu, Ag, Sn, Zn, Ti, Al, Nb, Zr, W, Ta, Mo, and combinations thereof (e.g., alloys and intermetallic compounds). The content of the metal element in the metal-containing layer is preferably 50 atomic % or more and 100 atomic % or less. The metal-containing layer may be a single layer consisting of one layer, or a multilayer consisting of two or more layers. The thickness of the entire metal-containing layer is preferably 10 nm to 1000 nm, more preferably 30 nm to 500 nm, even more preferably 50 nm to 400 nm, and particularly preferably 100 nm to 300 nm. The thickness of the metal-containing layer itself is a value measured by analyzing a cross section of the layer with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0051] Alternatively, the release layer 26 may be a metal oxynitride-containing layer instead of a carbon layer or the like. The surface of the metal oxynitride-containing layer opposite the carrier 22 (i.e., on the adhesive layer 30 side) preferably contains at least one metal oxynitride selected from the group consisting of TaON, NiON, TiON, NiWON, and MoON. Furthermore, when the adhesive sheet 20 includes a metal layer 28, the surface of the metal oxynitride-containing layer facing the carrier 22 preferably contains at least one metal oxynitride selected from the group consisting of Cu, Ti, Ta, Cr, Ni, Al, Mo, Zn, W, TiN, and TaN, in order to ensure adhesion between the carrier 22 and the metal layer 28. This reduces the number of foreign particles on the surface of the metal layer 28 and enables stable peel strength to be maintained even after heating at high temperatures for a long period of time. The thickness of the metal oxynitride-containing layer is preferably 5 nm to 500 nm, more preferably 10 nm to 400 nm, even more preferably 20 nm to 200 nm, and particularly preferably 30 nm to 100 nm, as measured by analyzing a cross section of the layer with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0052] The optional metal layer 28 is a layer made of metal. The presence of the metal layer 28 between the release layer 26 and the adhesive layer 30 allows for smoother release of the carrier 22 (and the intermediate layer 24, if present). The metal layer 28 may be a single-layer structure or a two- or more-layer structure. Preferred examples of metals constituting the metal layer 28 include Ti, Cu, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, In, Sn, Zn, Ga, Mo, and combinations thereof. More preferred are Cu, Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, Mo, and combinations thereof. Even more preferred are Cu, Ti, Al, Cr, Ni, Mo, and combinations thereof. Particularly preferred are Cu, Ti, Al, Ni, and combinations thereof. The metal layer 28 may be a pure metal or an alloy. The metal constituting the metal layer 28 may contain impurities resulting from raw material components, the film formation process, etc. Furthermore, the upper limit of the metal content is not particularly limited and may be 100 atomic %. The metal layer 28 is preferably a layer formed by physical vapor deposition (PVD), more preferably a layer formed by sputtering. The thickness (total thickness) of the metal layer 28 is preferably 10 nm to 1000 nm, more preferably 20 nm to 900 nm, more preferably 30 nm to 800 nm, even more preferably 40 nm to 700 nm, and particularly preferably 50 nm to 500 nm. This allows the metal layer 28 to be removed in an extremely short time, allowing for even faster peeling and removal of the adhesive sheet 20 after use as a reinforcing sheet. The thickness of the metal layer 28 is a value measured by analyzing a cross section of the layer using a transmission electron microscope with an energy dispersive X-ray spectrometer (TEM-EDX).

[0053] The formation of each of the intermediate layer 24 (if present), the release layer 26, and the metal layer 28 (if present) is preferably performed by a physical vapor deposition (PVD) method. Examples of physical vapor deposition (PVD) methods include sputtering, vacuum evaporation, and ion plating. However, sputtering is most preferred because it allows for film thickness control over a wide range, such as 0.05 nm to 5000 nm, and ensures film thickness uniformity over a wide width or area. In particular, forming all of the intermediate layer 24 (if present), the release layer 26, and the metal layer 28 (if present) by sputtering significantly improves manufacturing efficiency. Therefore, the intermediate layer 24 (if present), the release layer 26, and the metal layer 28 (if present) are preferably physical vapor deposition (PVD) films, i.e., films formed by a physical vapor deposition (PVD) method, and more preferably sputtered films, i.e., films formed by a sputtering method.

[0054] Film formation by physical vapor deposition (PVD) can be performed using a known vapor deposition apparatus under known conditions, without any particular limitations. For example, when a sputtering method is employed, the sputtering method may be any of various known methods, such as magnetron sputtering, bipolar sputtering, and facing target sputtering. However, magnetron sputtering is preferred due to its high film formation rate and high productivity. Sputtering can be performed using either a DC (direct current) or RF (radio frequency) power source. Furthermore, while a widely known plate-shaped target can be used, a cylindrical target is preferable from the perspective of target utilization efficiency. The purity of the target is preferably 99.9% or higher. An inert gas such as argon gas is preferably used as the gas used for sputtering. The flow rate of argon gas can be determined appropriately depending on the sputtering chamber size and film formation conditions, without any particular limitations. Furthermore, in order to achieve continuous film formation without operational problems such as abnormal discharge or poor plasma irradiation, the pressure during film formation is preferably in the range of 0.1 Pa to 20 Pa. This pressure range may be set by adjusting the film formation power and the flow rate of argon gas according to the structure and capacity of the apparatus, the exhaust capacity of the vacuum pump, the rated capacity of the film formation power supply, etc. Also, the sputtering power is set to 0.05 W / cm per unit area of ​​the target, taking into consideration the uniformity of the film thickness, productivity, etc. ２ More than 10.0W / cm ２ It may be set appropriately within the following range.

[0055] When the adhesive sheet 20 has a metal layer 28 or the like, it is preferable that the metal layer 28, the optional intermediate layer 24, and the optional release layer 26 (i.e., at least the metal layer 28, e.g., the metal layer 28 and the intermediate layer 24) extend to the edge surfaces of the carrier 22, thereby covering the edge surfaces. That is, it is preferable that not only the surface but also the edge surfaces of the carrier 22 are covered with at least the metal layer 28. Covering the edge surfaces not only prevents infiltration of chemicals into the carrier 22 during the manufacturing process of the wiring substrate 10, but also firmly prevents chipping due to peeling at the side edges when handling the adhesive sheet 20, i.e., chipping of the coating on the release layer 26 (i.e., the metal layer 28). The coated area on the edge surfaces of the carrier 22 is preferably 0.1 mm or more, more preferably 0.2 mm or more, from the surface of the carrier 22 in the thickness direction (i.e., the direction perpendicular to the carrier surface), and even more preferably extends across the entire edge surfaces of the carrier 22.

[0056] The overall thickness of the adhesive sheet 20 is not particularly limited, but is preferably 150 μm or more and 3000 μm or less, more preferably 170 μm or more and 2000 μm or less, and even more preferably 180 μm or more and 1600 μm or less. The size of the adhesive sheet 20 is not particularly limited, but is preferably a disk shape with a diameter of 100 mm or more, more preferably a disk shape with a diameter of 200 mm or more and 450 mm or less. According to another preferred embodiment of the present invention, the adhesive sheet 20 is a rectangle with short sides of 50 mm or more, more preferably a rectangle with short sides of 80 mm or more and 600 mm or less and long sides of 100 mm or more and 650 mm or less. Furthermore, the adhesive sheet 20 is in a form that can be handled by itself.

[0057] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0058] Examples A1 to A6 An adhesive sheet was vacuum laminated onto a wiring board having solder balls. The resulting laminate was then evaluated for deformation of the solder balls. Specifically, the procedure is as follows.

[0059] (1) Preparation of Wiring Board: A wiring board was obtained by forming a rewiring layer on a metal foil with a carrier. Specifically, a 100 mm square, 1.1 mm thick glass substrate (material: soda lime glass) was first prepared as the carrier. A titanium layer (50 nm thick) and a copper layer (200 nm thick) were deposited on this carrier as a two-layer intermediate layer, an amorphous carbon layer (6 nm thick) as a release layer, and a titanium layer (100 nm thick) and a copper layer (300 nm thick) as a two-layer metal foil by sputtering in this order to obtain a metal foil with a carrier. A rewiring layer including an insulating layer (material: polyimide resin) and a wiring layer (material: copper) was formed on this metal foil with a carrier by a coreless build-up method. Then, solder balls with a diameter of 240 μm and a height of 165 μm were regularly formed on the rewiring layer as bumps 12 at a pitch (center-to-center distance) of 400 μm to obtain a wiring board 10.

[0060] (2) Preparation of Adhesive Sheet A 100 mm square, 0.5 mm thick stainless steel (SUS304) sheet (Poisson's ratio 0.29) was prepared as the carrier 22. On this carrier 22, a titanium layer (50 nm thick) and a copper layer (200 nm thick) were deposited as the two-layer intermediate layer 24, an amorphous carbon layer (6 nm thick) was deposited as the release layer 26, and a titanium layer (100 nm thick) and a copper layer (300 nm thick) were deposited as the two-layer metal layer 28 in this order by sputtering. The metal layer 28 was deposited so as to extend to the end face of the carrier 22, thereby covering the end of the release layer 26. Then, a 100 mm square, 200 μm thick thermosetting epoxy resin film (TSA-1602, manufactured by Toray Industries, Inc.) was placed on the metal layer 28 as the adhesive layer 30, and vacuum lamination was performed for 60 seconds under conditions of a pressure of 0.60 MPa and 80°C to obtain an adhesive sheet 20.

[0061] (3) Lamination of Adhesive Sheet to Wiring Board The adhesive layer 30 of the adhesive sheet 20 was abutted against the bumps 12 of the wiring board 10, and a vacuum was drawn using a vacuum pump using a vacuum laminator (MVLP-500 / 600, manufactured by Meiki Seisakusho Co., Ltd.) according to the conditions shown in Table 1, followed by a first-stage vacuum lamination (press pressure: 0.60 MPa). For Examples A2, A3, A5, and A6, after the first-stage vacuum lamination, a second-stage vacuum lamination (press pressure: 0.60 MPa) was subsequently performed using the vacuum laminator according to the conditions shown in Table 1. On the other hand, for Examples A1 and A4, a second-stage vacuum lamination was not performed. In this way, a laminate 40 in which the bumps 12 were embedded in the adhesive layer 30 was obtained.

[0062] (4) Curing Treatment of Adhesive Layer The obtained laminate 40 was heated at 170°C for 2 hours to cure the adhesive layer 30. For reference, cross-sectional optical microscope images (magnification 100x) of the laminate 40 in Examples A1 and A6 after the curing treatment are shown in Figures 4 and 5, respectively. In the laminate of Example A1, air bubbles (voids) were observed at the base of the bumps 12, while in the laminate of Example A6, no air bubbles (voids) were observed between the bumps 12 and the adhesive layer 30.

[0063] (5) Heat Treatment The laminate 40 after the curing treatment was subjected to a reflow process of heat treatment at 260° C. for 1 minute. For reference, cross-sectional optical microscope images (magnification: 100 times) of the laminate 40 after the heat treatment in Examples A1 and A6 are shown in FIGS. 6 and 7, respectively.

[0064] Evaluation The presence or absence of deformation of the solder balls serving as bumps 12 was evaluated according to the following procedure. First, the carrier 22 was physically peeled off together with the intermediate layer 24 from the laminate 40 after reflow. The release layer 26 remaining on the laminate 40 was then removed by ashing. Specifically, the laminate 40 was placed in an ashing chamber, oxygen gas was introduced, and the oxygen was activated using plasma-generating power. This caused carbon, the main component of the release layer 26, to combine with the activated oxygen to form carbon dioxide, thereby removing the release layer 26 as a reaction product gas. The metal layer 28 exposed on the surface of the laminate 40 was then removed by etching. Specifically, the titanium layer was removed by treatment with a hydrogen peroxide-based alkaline etching solution at approximately 40°C for 1 minute, and the copper layer was removed by treatment with a sulfuric acid-hydrogen peroxide-based etching solution at approximately 25°C for 1 minute. After removing the release layer 26 and the metal layer 28, the laminate 40 was immersed in a resist remover (ST-120, manufactured by Tokyo Ohka Kogyo Co., Ltd.) at 50° C. for 3 minutes. This dissolved the adhesive layer 30 exposed on the surface of the laminate 40, exposing the solder balls.

[0065] The exposed solder ball surfaces were observed using a scanning electron microscope at an acceleration voltage of 15.0 kV to check for deformation of the solder balls. This observation was performed on 50 solder balls for each example, and if no deformation (chipping) was observed in any of the solder balls, the solder balls were evaluated as "no deformation." The results are shown in Table 1. For reference, SEM images (magnification 300x) of the surfaces of the solder balls in Examples A1, A2, A4, and A6 after peeling off the adhesive sheet are shown in Figures 8, 9, 10, and 11, respectively.

[0066]

[0067] Example B1: The presence or absence of deformation of the solder balls when the reflow process was repeated was confirmed. Specifically, in the above (5) heat treatment step, the laminate after the curing treatment was subjected to a reflow process in which heat treatment was repeated five times at 260°C for 1 minute. The laminate was produced and evaluated in the same manner as in Example A6. As a result, it was confirmed that there was no deformation of the solder balls in the laminate after reflow.

[0068] REFERENCE SIGNS LIST 10 wiring substrate 10a rewiring layer 10b molded resin layer 10c second rewiring layer 12 bump 20 adhesive sheet 22, 52 carrier 24, 54 intermediate layer 26, 56 release layer 28, 58 metal layer 30, 60 adhesive layer 40 laminate 50 reinforcing sheet C chip I integrated passive device P pillar V gap

Claims

1. A method for manufacturing a laminate, comprising the steps of: (a) preparing a wiring board having bumps on at least one surface; (b) laminating an adhesive sheet having a carrier, a release layer, and an adhesive layer containing an adhesive material, in this order, on the surface of the wiring board having the bumps, (b1) performing a first-stage vacuum lamination by abutting the bumps on the wiring board and the adhesive layer of the adhesive sheet at a vacuum pressure of 3.0 hPa or less to form a laminate in which the bumps are embedded in the adhesive layer; and (b2) performing a second-stage vacuum lamination on the laminate at the vacuum pressure and at a temperature higher than that of the first-stage vacuum lamination.

2. The method for producing a laminate according to claim 1, further comprising, after step (b) of laminating the adhesive sheet on the wiring board, a step (c) of curing the adhesive layer.

3. The method for manufacturing a laminate described in claim 2, further comprising, after step (c) of curing the adhesive layer, a step (d) of subjecting the laminate to a heat treatment at a temperature higher than that of the second stage vacuum lamination.

4. A method for producing a laminate according to any one of claims 1 to 3, wherein the first vacuum lamination step is carried out at a temperature of 60°C or higher and lower than 200°C, a pressure of 0.10 MPa or higher, and a pressure time of 10 seconds or higher and 600 seconds or lower.

5. A method for producing a laminate according to any one of claims 1 to 3, wherein the second vacuum lamination step is carried out at a temperature of 150°C or higher and 200°C or lower, a pressure of 0.10 MPa or higher, and a pressure time of 10 seconds or higher and 600 seconds or lower.

6. The method for manufacturing a laminate according to any one of claims 1 to 3, wherein the bumps are solder balls having a diameter of 10 μm or more and 1000 μm or less and a height of 10 μm or more and 1000 μm or less.

7. The method for manufacturing a laminate according to any one of claims 1 to 3, wherein the bumps are regularly arranged at a pitch (center-to-center distance) of 30 μm or more and 1000 μm or less.

8. The method for producing a laminate according to any one of claims 1 to 3, wherein the carrier has a Poisson's ratio of 0.15 or more and 0.50 or less.

9. The method for producing a laminate according to any one of claims 1 to 3, wherein the carrier is made of metal.

10. The method for producing a laminate according to any one of claims 1 to 3, wherein the carrier is at least one selected from aluminum and aluminum alloys, stainless steel, copper and copper alloys, titanium and titanium alloys, and nickel and nickel alloys.

11. The method for producing a laminate according to any one of claims 1 to 3, wherein the adhesive material is at least one selected from the group consisting of thermosetting epoxy resin, thermosetting polyimide resin, acrylic resin, and phenolic resin.

12. The method for producing a laminate according to any one of claims 1 to 3, wherein the adhesive layer has a thickness of 1 μm or more and 2000 μm or less.

13. Plan view area A of the carrier Ｃ The planar area A of the adhesive layer Ａ Ratio A Ａ / A Ｃ The method for producing a laminate according to any one of claims 1 to 3, wherein is 0.03 or more and 1.0 or less.

14. The method for producing a laminate according to any one of claims 1 to 3, wherein the release layer comprises carbon.

15. A method for producing a laminate according to any one of claims 1 to 3, wherein the adhesive sheet further comprises a metal layer provided between the release layer and the adhesive layer.

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