JP4349270B2 - Wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a method for manufacturing a high-density wiring board in which a plurality of layers of wirings are electrically connected by inner via hole connection.

  In recent years, with the downsizing and high performance of electronic devices, multilayer wiring circuit boards capable of mounting semiconductor chips such as LSIs with high density not only for industrial use but also in the field of consumer equipment are being supplied at low cost. There has been a strong demand. In such a multilayer printed circuit board, it is important that a plurality of wiring patterns formed at a fine wiring pitch can be electrically connected with high connection reliability.

  In addition, in mobile devices represented by mobile phones, in particular, in addition to the trend of integration of functions, the trend of thinning of devices is remarkable in order to improve portability. High density and thinness is required.

  In response to such market demands, instead of the metal plated conductor on the inner wall of the through-hole, which has been the mainstream of interlayer connection of conventional multilayer wiring boards, any electrode of the multilayer wiring board can be connected at any wiring pattern position. There is an inner via hole connection method, that is, an all-layer IVH structure resin multilayer wiring board (Patent Document 1).

  In addition, as an example of forming an all-layer IVH structure resin multilayer wiring board using a film as an electrically insulating substrate, a manufacturing method using wiring transfer is proposed in Patent Documents 2 and 3, and the same Patent Document 4 and Patent Document 5 propose a manufacturing method for forming a multilayer structure using a film.

  According to these techniques, it is possible to fill the via holes of the multilayer wiring board with the conductive paste and connect only the necessary layers, and the inner via holes can be provided directly under the component lands. Size reduction and high-density mounting can be realized. Moreover, since the electrical connection in the inner via hole uses a conductive paste, the stress applied to the via hole can be relieved, and a stable electrical connection can be realized against a dimensional change due to a thermal shock or the like. .

  Here, a typical conventional manufacturing method as an all-layer IVH structure resin multilayer wiring board using this film as an electrically insulating substrate will be described. FIGS. 5A to 5G show examples of double-sided wiring boards, and FIGS. 6A to 6C and FIGS. 7A to 7I show examples of multilayer wiring boards.

  FIGS. 5A to 5G are process cross-sectional views showing a conventional method for manufacturing a double-sided wiring board using a film as an electrically insulating substrate.

  First, as shown in FIG. 5A, the wiring 2 is formed on the support base 1. Next, an adhesive 4 is formed on both sides of the film 3 shown in FIG. A protective film 5 is formed on the surface. Subsequently, as shown in FIG. 5 (c), a through hole 7 is formed in the electrically insulating substrate 6. Drilling, punching, laser processing, or the like is used to form the through hole 7, but laser processing is used when the through hole 7 becomes fine and productivity is required.

  Next, as shown in FIG. 5 (d), the through-hole 7 is filled with a conductive paste 8. When the conductive paste is compressed, the resin in the conductive paste is discharged, and the conductive particle component density in the conductive paste can be substantially improved and densified. This dense conductive paste realizes a stable electrical connection. Since the conductive paste can be filled by printing, the productivity is very excellent. The protective film 5 has a function as a mask in the conductive paste printing process and a function of filling the through hole 7 with more conductive paste after the protective film 5 is peeled off.

  Next, as shown in FIGS. 5E to 5F, the support base material 1 provided with the wiring 2 is bonded by heating and pressing from both sides of the electrically insulating base material 6. In this step, the wiring 2 is embedded in the adhesive 4, and the conductive paste 8 is compressed as described above to densify the conductive paste. As a result, the electrical connection inside the conductive paste is further stabilized, and the wiring 2 and the conductive paste 8 are also brought into high-density contact, thereby stabilizing the electrical connection. Subsequently, when the support base 1 on the front and back surfaces is removed, the double-sided wiring board 9 shown in FIG. 5G is formed.

  6A to 6C are process cross-sectional views showing a conventional manufacturing method in which the double-sided wiring board 9 of FIG. 5G is multilayered.

  First, the double-sided wiring board 9 is as shown in FIG. 5G described above, and has a structure in which the wiring 2 is embedded in the adhesive 4 and the substrate surface becomes flat. The electrically insulating base 12 is composed of a film 3 and an adhesive 4, and the adhesive 4 on the side in contact with the double-sided wiring board is formed thinner than the other. Further, the through-hole 7 and the conductive paste 8 are formed on the electrically insulating substrate 12 by the same manufacturing method as the example of FIG. 5 already described, and the surface protective film 5 is removed. When the supporting base material 1 on which the wiring 2 is further formed is laminated on the double-sided wiring board 9 with the electrically insulating base material 12 provided with the adhesive 4 interposed therebetween, the state shown in FIG.

  Next, the double-sided wiring board 9 and the electrically insulating base material 12 are bonded in the heating and pressing step shown in FIG. At this time, the wiring 2 is embedded in the adhesive 4 and the electrical connection is ensured by compressing the conductive paste 8.

  Next, as shown in FIG. 6C, if the supporting base material 1 is removed while leaving the wiring 2, the four-layer wiring board is completed.

  Further, FIGS. 7A to 7I are process cross-sectional views showing another method for manufacturing a conventional multilayer wiring board using a film as an electrically insulating substrate.

  First, as shown in FIG. 7A, an adhesive 4 is formed on both sides of the film 3, and a protective film 5 is formed on one adhesive surface. A transfer substrate on which the desired wiring 2 is formed on the support substrate 1 is disposed on the side where the protective film of the electrically insulating substrate is not formed. In this state, when bonding is performed by applying temperature and pressure by lamination, the state shown in FIG. 7B is obtained. In this bonding process, it is desirable that the temperature is set to a level necessary for the tackiness of the adhesive to be generated, the pressure is set as small as possible, and the conditions are set so that the wiring 2 is not completely embedded in the adhesive 4. By setting such conditions, compression in the subsequent pressing process is ensured.

  Next, as shown in FIG.7 (c), the through-hole 7 is formed so that the electrically insulating base material 6 and the protective film 5 may be penetrated. The wiring 2 is partially exposed at the bottom of the through hole 7. The through hole 7 closed on the wiring 2 side can be easily realized by laser processing by adjusting the processing energy.

  Next, as shown in FIG. 7D, the through-hole 7 is filled with a conductive paste 8. In order to realize stable filling of the conductive paste into the through-hole 7, it is desirable that printing is repeated. In this state, the surface of the conductive paste and the surface of the protective film 5 are substantially the same height.

  Next, as shown in FIG. 7E, the protective film 5 on the surface is peeled off, and the wiring material 10 is laminated on the side where the protective film is peeled off. At this time, the surface of the conductive paste 8 protrudes substantially from the surface of the adhesive 4 by the thickness of the protective film 5.

  In this state, the state shown in FIG. 7F is obtained by heating and pressurizing with a press and bonding. At this time, the wiring layer 2 is sufficiently embedded in the adhesive 4, and the conductive paste 8 is further compressed. By this compression, the conductive particles in the conductive paste are strongly bonded, and the bonding at the interface between the wiring 2 and the wiring material 10 and the conductive paste 8 is also strong. This strong connection ensures the reliability of connection between the wiring and the conductive paste.

  Subsequently, the wiring material 10 is patterned by etching to complete a double-sided wiring board as shown in FIG.

  Furthermore, by repeating the steps of FIGS. 7 (a) to (g), multilayering is performed as shown in FIG. 7 (h), and finally the supporting base material 1 is removed, so that FIG. A multilayer wiring board as shown can be formed.

According to this manufacturing method, since layers are formed one layer at a time on the support base material 1, a wiring board can be formed with an optimum number of layers necessary for wiring accommodation, so that materials and processes can be set to the minimum necessary, Cost is advantageous. In addition, when multi-layered, the through hole is formed after the electrically insulating base material is pasted on the lower wiring, so that the through hole can be processed aiming at a desired position after recognizing the position of the wiring pattern. This is advantageous in that the positioning accuracy of the wiring and the through hole is excellent.
Japanese Patent Laid-Open No. 06-268345 JP 2000-77800 A JP 2000-340954 A JP 2002-151853 A JP 2001-345539 A

  In any of the above-described wiring board manufacturing methods, the wiring formed on the supporting base material is embedded in the electrically insulating base material by transfer, and the conductive paste is compressed to ensure electrical connection. In other words, in the conventional method of manufacturing a multilayer wiring board, since it is an electrically insulating base material that is difficult to achieve via connection in a through hole, wiring is buried and the conductive paste is forcibly compressed. In this way, electrical connection was realized. That is, the conventional electrical insulating base material has a problem that it is difficult to ensure electrical connection with a conductive paste as a single material.

  In addition, according to the conventional method for manufacturing a wiring board shown in FIGS. 5 and 6, all the wiring is formed by transferring the wiring formed on the support base material, and electrical insulation with low rigidity using a film is performed. Since a wet process such as etching is not performed on the conductive base material alone, it is excellent in transportability, while it is necessary to perform a single pattern formation step in order to form one wiring layer. That is, in the general wiring board manufacturing process, the wiring on the front and back surfaces of the electrically insulating base material is simultaneously formed in one pattern forming process, but in the above example, there is a problem that the productivity of the pattern process is inferior. there were.

  Similarly, the conventional method for manufacturing a wiring board shown in FIG. 7 also does not perform a wet process such as etching alone on a low-rigidity electrically insulating base material using a film. On the other hand, since the wiring layers of the multilayer wiring board are formed one by one, there is a problem inferior in productivity.

  SUMMARY OF THE INVENTION The present invention solves the above-described problems, and provides a highly productive manufacturing method of a high-density wiring board having an all-layer IVH structure using a film, and multilayer wiring in which wiring layers are electrically connected with high reliability. An object is to provide a substrate structure.

  In order to achieve the above object, the present invention has the following configuration.

  According to the first aspect of the present invention, there is provided an electrically insulating substrate provided with an adhesive on both surfaces of a film, a through hole provided in the electrically insulating substrate, and a conductive material filled in the through hole. A multilayer wiring board comprising a conductive paste and a wiring electrically connected to the conductive paste, wherein the multilayer wiring board is composed of an odd number of electrically insulating substrates, and is bonded to an electrically insulating substrate for a core It is a multilayer wiring board whose agent volume is smaller than the adhesive volume in other electrically insulating substrates, and the adhesive volume in the electrically insulating substrate for the core is small, so that the conductive paste spreads to the adhesive Since it can suppress, also in the electrically insulating base material of the core part which does not compress by wiring, the electrical connection equivalent to another electrically insulating base material layer can be ensured.

  In addition, the electrically insulating base material for the core here refers to a so-called double-sided wiring board provided with wirings on both surfaces of the electrically insulating base material and through holes for electrically connecting the wirings. A wiring layer can be multilayered by sequentially laminating an electrically insulating base material on the double-sided wiring board in the manufacturing process of the wiring board.

  Invention of Claim 2 of this invention is a multilayer wiring board of Claim 1 with which the film thickness of the said electrically insulating base material for cores is larger than the film thickness in another electrically insulating base material. By increasing the thickness of the film in the electrically insulating base material of the core portion, the rigidity can be increased, and the wiring of the core portion can be formed with the same material as other electrically insulating base materials with good transportability.

  The invention according to claim 3 of the present invention is the multilayer wiring according to claim 1, wherein the elastic modulus of the film of the electrically insulating substrate for the core is larger than the elastic modulus of the film of the other electrically insulating substrate. It is possible to further improve the transportability by using a film having higher rigidity in the electrically insulating base material of the core portion.

  Invention of Claim 4 of this invention is a multilayer wiring board of Claim 1 whose elasticity modulus of the film of the said electrically insulating base material is 2.5 GPa or more, Comprising: The elasticity modulus of a film is 2. By setting it as 5 GPa or more, a through-hole wall surface can suppress effectively the spreading | diffusion of an electrically conductive paste, the compression of an electrically conductive paste can be improved, and a reliable electrical connection can be implement | achieved as a result.

  The invention according to claim 5 of the present invention is such that the minimum melt viscosity of the adhesive of the electrically insulating substrate for the core is larger than the minimum melt viscosity of the adhesive in the other electrically insulating substrate. The multilayer wiring board according to claim 1, wherein the minimum melt viscosity of the adhesive formed on the electrically insulating base material of the core portion is made larger than that of the other electrically insulating base material layer, so that the conductive property of the core portion is increased. Even in the electrically insulating base material of the core portion that suppresses the spread of the conductive paste to the adhesive and does not compress the wiring, it is possible to ensure the same electrical connection as the other electrically insulating base material layers .

  The invention according to claim 6 of the present invention is the multilayer wiring board according to claim 1, wherein the at least one electrically insulating substrate of the multilayer wiring board has different minimum melt viscosities of the adhesive on the front and back surfaces of the film. In the adhesive on the front and back surfaces of the film, the minimum melt viscosity of the adhesive on the side requiring wiring embedding is made lower than the other, so that the wiring embedding in the adhesive on one side and the conductivity in the adhesive on the other side are conducted. As a result, it is possible to provide a wiring board having excellent moldability and electrical connectivity.

  The invention according to claim 7 of the present invention is the multilayer wiring board according to claim 1, wherein at least one electrically insulating base material of the multilayer wiring board is formed with an adhesive of different materials on the front and back surfaces of the film. As a result, the material design of the electrically insulating base material that achieves both formability and electrical connectivity is widened, and the physical properties of the electrically insulating base material can be changed locally, enabling electronic components to be used on multilayer wiring boards. It is possible to improve functions such as mounting.

  The invention according to claim 8 of the present invention is the multilayer wiring board according to claim 1, wherein the electrically insulating base material of the multilayer wiring board includes an adhesive having a minimum melt viscosity of 100 to 5000 Pa · s. By setting the minimum melt viscosity of the adhesive to 100 to 5000 Pa · s, it is possible to ensure both electrical connection by suppressing the spread of the conductive paste and the embedding of the wiring.

  The invention according to claim 9 of the present invention includes a step of forming a through hole in a first electrically insulating base material provided with an adhesive on both surfaces of the film, and a through hole of the first electrically insulating base material. A step of filling a conductive paste on the substrate, a pressing step of laminating wiring materials on both sides of the first electrically insulating substrate, and bonding them by heating and pressing, and front and back surfaces of the first electrically insulating substrate A step of patterning the wiring material, a step of forming a through hole in the second electrically insulating substrate provided with an adhesive on both sides of the film, and a conductive property in the through hole of the second electrically insulating substrate. The paste filling step, the patterned first electrically insulating substrate, the second electrically insulating substrate filled with the conductive paste, and the wiring material are laminated and bonded by heating and pressing. A process and a patterning process for the wiring material. In the method of manufacturing a wiring board, the adhesive volume in the first electrically insulating substrate is smaller than the adhesive volume in the second electrically insulating substrate. Since the adhesive volume in the insulating substrate is small, the spread of the conductive paste to the adhesive can be suppressed, so even in the first electrically insulating substrate that does not compress the wiring, other electrically insulating groups An electrical connection equivalent to that of the material layer can be ensured.

  The invention according to claim 10 of the present invention shows the softening temperature and the minimum melt viscosity of the adhesive formed on the second electrically insulating substrate in the pressing step of the second electrically insulating substrate. The wiring pattern formed on the first electrically insulating substrate at a midpoint temperature is embedded by 50% or more in the thickness direction with respect to the second electrically insulating substrate. In this method of manufacturing a multilayer wiring board, it is possible to suppress the spread of the conductive paste when the adhesive has the lowest melt viscosity, and as a result, it is possible to achieve both wiring embedding and electrical connection.

  The invention according to claim 11 of the present invention is the production of the multilayer wiring board according to claim 9, wherein the pattern ratio outside the product region of the wiring formed on the first electrically insulating substrate is 50% or more. This method allows the wiring material made of metal to remain in a wide area other than the product area, thereby increasing the rigidity of the electrically insulating substrate and improving the transportability in the wiring formation process of the first electrically insulating substrate. Can be made.

  According to a twelfth aspect of the present invention, in the manufacturing method of the multilayer wiring board according to the ninth aspect, the first electrically insulating substrate is a substantially rectangular sheet shape, and at least two corners are cut off. It is a method, and in the manufacturing process of wet processing such as etching and cleaning, the substrate can be prevented from being bent or damaged by a transfer roller, and productivity can be increased.

  According to the present invention, since the volume of the adhesive in the electrically insulating base material of the core portion is small and the spread of the conductive paste to the adhesive can be suppressed, the electrically insulating base material of the core portion that is not compressed by wiring In addition, it is possible to provide a multilayer wiring board having the same connectivity as other electrically insulating base material layers, and by increasing the rigidity of the electrically insulating base material of the core part, the wiring of the core part can be formed with good transportability. And a manufacturing method with excellent productivity can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
1A to 1J are cross-sectional views of the main manufacturing process of the multilayer wiring board according to the present invention. First, the electrically insulating substrate 6 shown in FIG. 1 (a) has an adhesive 4 formed on both surfaces of a film 3, and further, protective films 5 are formed on the front and back surfaces thereof.

  As the film 3, a flexible wiring board material can be used, and a material having high heat resistance is more preferable. Specifically, polyimide film, aramid film, and LCP film are preferable in terms of heat resistance. As the polyimide film, “Kapton” (trademark of Toray DuPont Co., Ltd.), “Upilex” (trademark of Ube Industries, Ltd.) ), “Apical” (trademark of Kaneka Chemical Co., Ltd.), and “Aramika” (trademark of Asahi Kasei Co., Ltd.) and “Miktron” (trademark of Toray Industries, Inc.) are suitable as the aramid film. As for the thickness, it is possible to use an extremely thin material of about 9 microns for a polyimide film and about 4 microns for an aramid film, and if these are used, an extremely thin multilayer wiring board can be formed. it can. For example, if a 25 micron film of Upilex is used, the elastic modulus is 9.1 GPa, and sufficient rigidity can be obtained to ensure transportability.

  As the adhesive, a thermosetting resin is used, and a material mainly composed of an epoxy resin or a polyimide resin can be used. As a material, a plastic component or a filler may be added in order to provide adhesion to the wiring material or heat resistance. As for the filler, by using an inorganic filler such as silica or alumina, it is possible to adjust physical properties such as increasing the hardness of the adhesive and decreasing the moisture absorption rate. As a method for forming the adhesive 4, an adhesive varnish may be applied directly on the film 3, or an adhesive varnish may be applied on the protective film 5 and attached to the film for transfer. The film surface is generally subjected to corona treatment or plasma treatment in order to improve the adhesion with the adhesive. Here, as an example, an epoxy adhesive was directly applied on both sides of a 25 micron thick polyimide film to a thickness of 3 microns.

  The protective film 5 formed on the front and back surfaces of the electrically insulating substrate 6 is a film mainly composed of PET (polyethylene terephthalate) or PEN (polyethylene naphthalate), and is laminated on both surfaces of the electrically insulating substrate 6 by lamination. The production method is simple and easy to apply. The laminating conditions are performed at a temperature at which the adhesive 4 is softened, and a method of laminating in a short time such as laminating is preferable so as not to advance the curing of the thermosetting resin. Further, as described above, after the adhesive 4 is applied on the protective film 5, the film 3 can be laminated. Here, when a PEN or PET film was used as the protective film, it was excellent in tensile strength, so that even with a thickness of 9 microns, it could be stuck on the electrically insulating substrate 6 without wrinkles by lamination. In addition, since the PEN film can absorb a wavelength of 351 nm, there is an advantage that it is excellent in YAG laser processability of a third harmonic.

  Next, as shown in FIG.1 (b), the through-hole 7 which penetrates the protective film 5 and the electrically insulating base material 6 is formed. The through-hole 7 can be formed by punching, drilling, or laser processing, but if a carbon dioxide laser or YAG laser is used, a small-diameter through-hole can be formed in a short period of time, realizing excellent productivity. it can. As an example, when a carbon dioxide laser is used, an adhesive is formed on both sides of a polyimide film having a thickness of 25 microns, 3 microns each, and a PET film having a thickness of 9 microns is pasted, and an electrically insulating substrate 6 having a total of about 50 microns. On the other hand, a through hole having a diameter of 100 microns could be processed. In addition, when a third harmonic of a YAG laser was used, a 30 μm diameter through-hole could be processed in an electrically insulating substrate having a total thickness of about 40 microns.

  Subsequently, as shown in FIG. 1C, the through-hole 7 is filled with a conductive paste 8. The conductive paste 8 is composed of metal conductive particles such as copper and silver and a resin component. It is more preferable to use a substantially spherical conductive particle because the paste viscosity can be kept low even when the conductive particle ratio in the conductive paste increases.

  At this time, the protective film 5 plays a role of protecting the conductive paste 8 from adhering to the surface of the electrically insulating substrate and a role of ensuring the filling amount of the conductive paste. Since the conductive paste can be filled by printing, it has an advantage of excellent productivity.

  Next, the state shown in FIG. 1D is obtained by peeling off the protective film 5. The conductive paste 8 has a filling amount secured by the protective film 5. That is, the conductive paste 8 is in a state of protruding from the surface of the electrically insulating substrate 6 by the height of the thickness of the protective film 5. Here, when the thickness of the protective film 5 is set to about 5 to 25% of the via diameter, it is more preferable because the amount of the conductive paste taken to the protective film side when the protective film 5 is peeled can be suppressed. As an example, for an electrically insulating base material having a total thickness of about 50 microns using the above-mentioned 25 micron polyimide film and a 9 micron protective film, the amount of protrusion can be secured even at a through hole diameter of 50 microns. It was.

  After the protective film 5 is peeled off, the wiring material 10 is laminated on both surfaces of the electrically insulating base 6 as shown in FIG. 1 (e), and the wiring material 10 is heated and pressed by hot pressing. 6 and when the conductive paste 8 is compressed, the state shown in FIG. Here, an electrolytic copper foil of 9 microns is used as the wiring material 10. However, when the multilayer wiring board is thinned, an electrolytic copper foil with a carrier of 5 microns thickness or a rolled copper foil of 5 microns is used. You can also.

  Moreover, about this electrically conductive paste 8, after filling, many resin 10 exists between the electrically conductive particles 9 in an electrically conductive paste, and sufficient electrical connection is not ensured. On the other hand, in the heating and pressing step, the conductive paste 4 is compressed and the conductive particles in the conductive paste come into close contact with each other, so that electrical connection in the conductive paste can be ensured. The resin component in the conductive paste is indispensable in terms of reducing the viscosity of the conductive paste during the filling process and stably filling fine through holes. Effectively discharging the resin component is important in securing electrical connection.

  Here, it is more preferable to use a thermosetting resin as the resin of the conductive paste, the viscosity is reduced during hot pressing, and the thermosetting resin is discharged out of the through-hole due to the compression of the conductive paste. As a result, the contact of the conductive particles in the conductive paste can be made higher density.

  In FIG. 1 (f), since the wiring material 10 is a flat foil, it is not necessary to embed wiring as the adhesive 4, and it is sufficient to ensure adhesion with the wiring material. The thickness is set to 3 microns. Thus, it is preferable to set the adhesive thickness to the minimum thickness that does not impair the adhesion, and the spread to the adhesive when the conductive paste 8 is compressed is suppressed. That is, the protruding portion of the conductive paste 8 formed by peeling off the protective film 5 is difficult to spread to the periphery during lamination adhesion, and thus the conductive paste in the through hole is effectively compressed. The thickness of the adhesive is not limited to 3 microns and can be adjusted according to the material of the adhesive and the diameter of the through hole.

  The minimum melt viscosity of the adhesive of the electrically insulating base 6 is more preferably higher than the minimum melt viscosity of the adhesive of the electrically insulating base 12 for lamination described later. As described above, the electrically insulating substrate 6 becomes the core portion of the multilayer wiring board, and there is no need to embed wiring in the layering process of the wiring material 10. Therefore, by setting the minimum melt viscosity high, it is possible to further suppress the spread of the conductive paste in the adhesive portion when the wiring material is affixed to the electrically insulating substrate, and obtain a good electrical connection. Can do. Specifically, after the adhesive 4 is applied on the film 3, heating can be performed to advance the curing of the adhesive. This makes it possible to easily increase the melt viscosity of the adhesive. Of course, the rubber component and the thermoplastic component may be reduced as the material of the adhesive, and the melt viscosity may be set high.

  Moreover, as the film 3, it is more preferable that an elasticity modulus is 2.5 GPa or more, and it can suppress that the film part of a through-hole wall surface spreads by compression of the above-mentioned conductive paste. That is, the relaxation of the compressive stress applied to the conductive paste in the through hole can be reduced, and as a result, the contact density of the conductive particles in the conductive paste can be increased and highly reliable electrical connection can be realized.

  Next, when the wiring material 10 is patterned by etching to form the wiring 2, the state shown in FIG. 1G is obtained, and a double-sided wiring substrate 11 in which the wiring 2 protrudes from the electrically insulating substrate 6 can be formed.

  Here, when patterning by etching, it is preferable that the pattern ratio outside the product region of the wiring formed on the electrically insulating substrate is 0.5 or more. Here, the pattern ratio indicates the wiring layer area ratio in the specific region, and is calculated by dividing the wiring layer area on the front and back surfaces of the specific region by twice the specific region area.

  In addition, the product area refers to an area of the wiring board that is fixed to an electronic device or the like and finally functions an electronic circuit. In general, as a method for manufacturing a wiring board, a plurality of product regions 13 are formed on a large double-sided wiring board 11 as shown in FIG.

  As described above, by leaving the wiring material made of metal in a wide area with a pattern ratio of 0.5 or more in addition to the product area, the rigidity of the electrically insulating substrate is increased and the transportability in the wiring forming process is improved. Can do.

  As an example, as shown in FIG. 3B, by forming a mesh-like wiring pattern outside the product region with a pattern ratio of 0.75, the winding of the shower etching on the transfer roller is suppressed, and the polyimide has a thickness of 25 microns. The film was shower-etched with a cut sheet of 500 mm × 300 mm.

  3B shows an example in which the wiring board is dried and a mesh pattern that easily removes moisture is used. However, the pattern may be a solid pattern, and the same effect can be obtained.

  Further, as shown in FIG. 4 as the cut sheet-like double-sided wiring substrate 11, it is more preferable that the two corners preceding the etching conveyance direction are cut off at least. As a result, in the manufacturing process of wet processing such as etching and cleaning, bending of the substrate end due to warping of the end of the wiring board, clogging of the substrate during conveyance, clogging of the substrate during conveyance, and damage to the substrate are reduced. The productivity of the substrate can be increased.

  In FIG. 4, the pattern ratio outside the product area has been described as an example of 1.0. However, the pattern outside the product area is not limited to this, and the same effect can be obtained in another pattern. it can.

  Subsequently, as shown in FIG. 1 (h), after positioning and laminating the electrically insulating base material 12 and the wiring material 10 on both sides of the double-sided wiring board 11, the materials are bonded by heating and pressurizing by a hot press process, and molding When this is done, the state shown in FIG. In addition, you may use resin press sheets, such as PE which supplement wiring embedding in the case of a hot press.

  Here, the electrically insulating base material 12 has the adhesive 4 formed on both surfaces of the film 3, the through holes 7 and the conductive paste 8 are provided, and the protective film 5 on the surface is removed. As the electrical insulating base material 12, the same kind of material as that of the electrical insulating base material 6 described above can be used. However, since the functions required for the electrical insulating base material are different, the materials and configurations are different. It is set to. That is, for this electrically insulating base material 12, since it is necessary to embed the wiring 2, the adhesive volume that is the sum of the adhesive amounts on the front and back surfaces is set larger than the adhesive volume of the electrically insulating base material 6. is doing. The adhesive volume can be adjusted by the pattern of the wiring 2.

  As an example, for a 9-micron wiring 2 having a pattern formed in a 50% region, an electrically insulating substrate 12 having an adhesive formed in a thickness of 20 microns, 10 microns on each side, was used. Here, even if the volume of the adhesive is larger than the example shown in the electrically insulating base material 6, since the wiring 2 is embedded in the adhesive 4 and compresses the conductive paste 8, the electrical connection can be secured. is there. That is, even if some conductive paste spreads on the adhesive 4, the wiring 2 is embedded in the electrically insulating base 12 by the thickness of the wiring 2, so that the conductive paste is substantially compressed and electrically connected. Is done.

  In addition, about the minimum melt viscosity of the adhesive agent 4, in order to make the embedding of the said wiring and the spreading | diffusion suppression of an electrically conductive paste compatible, it is preferable that the minimum melt viscosity is 100-5000 Pa * S. When the melt viscosity is within this range, the adhesive flows sufficiently while suppressing the spread of the conductive paste at the temperature of the minimum melt viscosity at the time of the subsequent hot press molding by heating and pressing, and the electric insulation property A gap between the base 12 and the double-sided wiring board 11 can be filled.

  Moreover, as the film 3 of the electrically insulating base material 12, it is more preferable to set rigidity low in order to embed wiring, and a material thinner than the film 3 of the electrically insulating base material 6 can be used. That is, when the wiring 2 is embedded in the electrically insulating base material 12, the film 3 can easily follow the unevenness caused by the wiring 2, thereby promoting the movement of the adhesive on the front and back surfaces of the electrically insulating base material 12. .

  As an example, when the adhesive 4 of the electrically insulating substrate 12 is formed to 7 microns on the side where the wiring 2 is embedded and 7 microns on the other side, the wiring 2 having a thickness of 9 microns is embedded with the adhesive on the side where the wiring is embedded. For this purpose, the flow of the adhesive must be extremely low.

  However, the other adhesive moves due to the pressure of the wiring 2, and the film 3 is deformed at the same time, so that the flow of the adhesive on the side of embedding the wiring is suppressed, and the wiring 2 is connected to the entire electrically insulating substrate 12. Embed.

  As an example, when a 12.5 micron thick film of Upilex (trademark of Ube Industries, Ltd.) with a 7 micron adhesive formed on both sides is used, it follows the 9 micron thick wiring 2 described above. I was able to. Moreover, even if a 4.5-micron-thick film of Aramika (trademark of Asahi Kasei Co., Ltd.) with a 7-micron adhesive formed on both sides is used, wiring can be embedded by following the same, resulting in 20 An extremely thin electrically insulating base material 12 having a thickness of less than a micron thickness could be formed.

  Moreover, it is more preferable to use a material having a lower elastic modulus as the film 3 of the electrically insulating substrate 12 than the film of the electrically insulating substrate 6. As an example, when a Kapton film (trademark of Toray DuPont Co., Ltd.) is used as the film of the electrically insulating substrate 12, the elastic modulus is 5.7 GPa, and the aforementioned Upilex (trademark of Ube Industries, Ltd.) Compared with the elastic modulus of 9.1 GPa, the followability to the wiring was good.

  By reducing the rigidity of the film 3 of the electrically insulating base material 12 in this way, the followability to the wiring 2 is improved, and as a result, the occurrence of defective wiring embedding when forming a multilayer wiring board is suppressed. It is.

  Further, when the adhesive 4 formed on the film 3 of the electrically insulating substrate 12 has a sufficient adhesive volume on the side where the wiring 2 is embedded, the adhesive may have different minimum melt viscosities on the front and back surfaces. More preferred. In other words, in the adhesive 4 on the front and back surfaces of the film 3 of the electrically insulating base material 12, the minimum melt viscosity of the adhesive on the side requiring wiring embedding is made lower than that on the other side, thereby embedding the wiring in the adhesive on one side. In addition, it is possible to achieve both suppression of spreading of the conductive paste in the adhesive on the other side, and it is possible to provide a wiring board excellent in moldability and electrical connectivity of the electrically insulating base material. That is, the adhesive on the side in contact with the wiring 2 that mainly contributes to the wiring embedding lowers the melt viscosity to improve the flowability and ensure sufficient wiring embedding.

  Thus, even if the adhesive flows, the wiring 2 is embedded in the adhesive 4, so that high compression is obtained and electrical connection can be ensured. On the other hand, since the wiring is not embedded on the other side, the melt viscosity of the adhesive is set high, and the spread of the conductive paste in the adhesive 4 is suppressed.

  A method for forming such an electrically insulating substrate will be described below.

  In the step of forming the electrically insulating substrate 12, when the adhesive is applied and dried on one side of the film 3 and further the adhesive is applied and dried on the other side, the adhesive applied the first time is heat generated by the drying twice. Exposed to. Therefore, by controlling the difference between the amount of heat applied to the adhesive applied for the first time and the amount of heat applied for the second time, the minimum melt viscosity on the side applied for the first time can be set high. Thus, it is possible to provide electrically insulating substrates having different melt viscosities.

  Further, the adhesive formed on the film 3 of the electrically insulating substrate 12 may be made of different materials on the front and back surfaces. By forming the adhesive with different material composition on the front and back surfaces, the aforementioned minimum melt viscosity can be controlled with a wider design margin.

  As an example, on the outermost surface of the wiring board, it is necessary to mount the electronic component with high reliability, and a wiring having high adhesion strength is required. Therefore, the adhesive 4 corresponding to the outermost layer of the wiring board can be set as a material having good adhesion to the wiring material 10. Specifically, an epoxy resin containing a low Tg component is formed on the outer layer side of the film 3 so that a high Tg epoxy is formed on the inner layer side while keeping the peel strength with the wiring material at 1.0 kg / cm or more. By forming the resin, it was possible to ensure the heat resistance of the entire wiring board.

  As another example, when a semiconductor bare chip is mounted by pressure mounting using bumps such as ACF on a multilayer wiring board, inorganic filler is dispersed with high Tg and high density as the adhesive 4 corresponding to the outermost layer. Epoxy resin was used. As a result, sinking of the connection pads on the wiring board side during bare chip mounting was suppressed, and good mountability could be secured.

  Further, in the hot pressing process of the electrically insulating base material 12, the adhesive 4 formed on the electrically insulating base material 12 is formed on the double-sided wiring substrate 11 at a midpoint temperature indicating a softening temperature and a minimum melt viscosity. It is more preferable that 50% or more of the wiring 2 is embedded in the thickness direction with respect to the electrically insulating substrate 12.

  Here, FIGS. 2 (a) to 2 (d) schematically show enlarged and temporal changes in the cross-sectional state around the through-hole 7 in the steps of FIGS. 1 (h) and 1 (i), and explain press forming in detail. .

  FIG. 2A shows an enlarged view of a portion A in FIG. The wiring 2 is formed on the double-sided wiring substrate 11 and has a shape protruding from the substrate surface. The electrically insulating substrate 12 is filled with the conductive paste 8 in the through holes 7. This electrically insulating substrate 12 is composed of a film 3 and an adhesive 4 formed on both surfaces thereof. The wiring material 10 is disposed on the outer side of the electrical insulating base material 12 and is subsequently heated and pressed in a pressing process to bond and form the double-sided wiring board 11, the electrical insulating base material 12, and the wiring material 10.

  Here, as for the temperature of the pressing process, the temperature is raised within a temperature rising rate range of 3 ° C. to 7 ° C. per minute. The temperature can be controlled with good controllability even when forming into a glass.

  In the initial stage of the pressing process, the wiring 2 on the wiring board 11 is not embedded in the adhesive 4 as shown in FIG. When the temperature continues to be increased and the softening temperature of the adhesive 4 is reached, embedding of the wiring 2 in the adhesive 4 becomes remarkable. When the temperature is further increased, the wiring 2 formed on the double-sided wiring board 11 at the midpoint temperature of the humidity indicating the softening temperature of the adhesive 4 and the minimum melt viscosity of the adhesive 4 as shown in FIG. However, 50% or more is embedded in the thickness direction with respect to the electrically insulating substrate 12. In this state, the adhesive 4 is softened and the wiring 2 is embedded, but the adhesive 4 does not flow by the pressing pressure. When the temperature is further increased, the adhesive 4 flows at a temperature showing the minimum melt viscosity, and the adhesive 4 penetrates into the fine gaps. At the same time, the curing reaction of the adhesive becomes remarkable, and when the molding is completed, FIG. d), the state shown in FIG.

Here, with regard to the molding temperature profile and pressure profile, the wiring 2 formed on the double-sided wiring board 11 is electrically insulated at the midpoint temperature of the temperature indicating the softening temperature of the adhesive 4 and the minimum melt viscosity of the adhesive 4. It is set so as to be embedded 50% or more in the thickness direction with respect to the base material 12, and as an example, the adhesive thickness is 10 microns, the minimum melt viscosity is 600p at 120 ° C, and the softening temperature is 60 ° C. When an epoxy resin is used, when heated at a press pressure of 50 kg / cm ² and a temperature rise of 3 ° C. per minute, the 9 μm thick wiring 2 is embedded in the adhesive 4 up to 90% in the depth direction at 90 ° C. It had been.

  In this way, by reducing the amount of wiring 2 embedded at a temperature showing the lowest melt viscosity, the flow of resin in the vicinity of the through hole can be reduced, and as a result, the adhesive 4 shows the lowest melt viscosity. However, it is possible to suppress the spreading of the conductive paste due to the resin flow and to effectively compress the conductive paste.

  The molding conditions are not limited to the above examples, and multi-stage temperatures and pressure profiles may be set in accordance with the material configuration of the electrically insulating base material so as to ensure the above-described embedding amount. .

  Subsequently, when the wiring material 10 on the outermost surface is patterned by etching or the like, the multilayer wiring board shown in FIG. Here, a four-layer board is used as an example of the multilayer wiring board. However, the number of wiring layers is not limited to this, and the number of wiring layers can be increased by repeating the same process.

  As described above, the wiring board and the manufacturing method thereof according to the present invention are excellent in productivity because the both sides of the electrically insulating substrate are simultaneously formed without using transfer for forming the wiring. In addition, for the core part where the conductive paste is hard to be compressed because the wiring is not embedded, the material structure of the electrically insulating base material is set differently from that of the electrically insulating base material for lamination. The spread of the paste is suppressed, the substantial compression of the conductive paste is ensured, and the electrical connection is realized.

  According to the method for manufacturing a wiring board according to the present invention, since the adhesive volume in the electrically insulating base material of the core portion is small and the spread of the conductive paste to the adhesive can be suppressed, the core that does not compress the wiring is performed. Even in the part of the electrically insulating base material, it is possible to provide a multilayer wiring board having the same connectivity as other electrically insulating base material layers, and by increasing the rigidity of the electrically insulating base material in the core part, The core portion can be formed with good performance, and a manufacturing method with excellent productivity can be provided. That is, the present invention is useful for a high-density multilayer wiring board using a film material.

(A)-(j) Process sectional drawing which showed the manufacturing method of the wiring board in Embodiment 1 of this invention for every main process. (A)-(d) Process sectional drawing which expanded and showed the main processes of the manufacturing method of the wiring board in Embodiment 1 of this invention. (A)-(b) Overview of double-sided wiring board in Embodiment 1 of the present invention Overview of double-sided wiring board in Embodiment 1 of the present invention (A)-(g) Process sectional drawing which showed the manufacturing method of the conventional double-sided wiring board for every main process (A)-(c) Process sectional drawing which showed the manufacturing method of the conventional multilayer wiring board for every main process (A)-(i) Process sectional drawing which showed the manufacturing method of the conventional multilayer wiring board for every main process

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support base material 2 Wiring 3 Film 4 Adhesive 5 Protective film 6 Electrical insulating base material 7 Through-hole 8 Conductive paste 9 Double-sided wiring board 10 Wiring material 11 Double-sided wiring board 12 Electrical insulating base material 13 Product area

Claims (12)

An electrically insulating substrate with adhesive on both sides of the film;
A through hole provided in the electrically insulating substrate;
A conductive paste filled in the through holes;
A multilayer wiring board comprising wiring electrically connected to the conductive paste,
A multilayer wiring board in which an adhesive volume of an electrical insulating base material for a core in the multilayer wiring board is smaller than an adhesive volume in another electrical insulating base material. The multilayer wiring board according to claim 1, wherein a film thickness of the electrically insulating base material for the core is larger than a film thickness of the other electrically insulating base material. The multilayer wiring board according to claim 1, wherein the elastic modulus of the film of the electrically insulating base material for the core is larger than the elastic modulus of the film of the other electrically insulating base material. The multilayer wiring board according to claim 1, wherein an elastic modulus of the film of the electrically insulating base material is 2.5 GPa or more. The multilayer wiring board according to claim 1, wherein the minimum melt viscosity of the adhesive of the electrical insulating base material for the core is larger than the minimum melt viscosity of the adhesives of other electrical insulating base materials. The multilayer wiring board according to claim 1, wherein at least one electrically insulating base material of the multilayer wiring board has different minimum melt viscosities of adhesives on the front and back surfaces of the film. The multilayer wiring board according to claim 1, wherein at least one electrically insulating base material of the multilayer wiring board is formed with an adhesive of different materials on the front and back surfaces of the film. The multilayer wiring board according to claim 1, wherein the electrically insulating base material of the multilayer wiring board includes an adhesive having a minimum melt viscosity of 100 to 5000 Pa · s. Forming a through hole in the first electrically insulating base material provided with an adhesive on both sides of the film;
Filling the through hole of the first electrically insulating substrate with a conductive paste;
A pressing step of laminating a wiring material on both sides of the first electrically insulating substrate and bonding by heating and pressing;
Patterning the wiring material on the front and back surfaces of the first electrically insulating substrate;
Forming a through-hole in a second electrically insulating substrate provided with an adhesive on both sides of the film;
Filling the through hole of the second electrically insulating substrate with a conductive paste;
A first step of patterning the first electrically insulating substrate, a second electrically insulating substrate filled with a conductive paste, a pressing step of laminating wiring materials and bonding them by heating and pressing;
In a method for manufacturing a multilayer wiring board comprising a step of patterning the wiring material,
A method for producing a multilayer wiring board, wherein an adhesive volume in the first electrically insulating substrate is smaller than an adhesive volume in the second electrically insulating substrate. In the pressing step of the second electrically insulating substrate, the first electrical insulating material is formed at the midpoint temperature of the softening temperature and the lowest melt viscosity of the adhesive formed on the second electrically insulating substrate. The method for manufacturing a multilayer wiring board according to claim 9, wherein the wiring pattern formed on the insulating base material is embedded in the thickness direction by 50% or more with respect to the second electrically insulating base material. The method for manufacturing a multilayer wiring board according to claim 9, wherein a pattern ratio outside the product region of the wiring formed on the first electrically insulating base material is 50% or more. The method for manufacturing a multilayer wiring board according to claim 9, wherein the first electrically insulating base is a substantially rectangular sheet, and at least two corners are cut off.

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