JP2006156617A - Wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board which satisfies via connectivity or insulating characteristics while making wiring and vias minuter so as to realize higher density of the wiring board, and also to provide its manufacturing method. <P>SOLUTION: The wiring board is constituted such that the connection of conductive particles 9 and plated wiring 7 is performed on the removal interface by removing conductive particles partially, thereby securing the area of larger connection interface, raising electric connectivity, and as a result, realizing the connection in minuter vias. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  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 response to such market demand, instead of the metal plated conductor on the inner wall of the through-hole, which has been the mainstream for interlayer connection of conventional multilayer wiring boards, any electrode of the multilayer printed wiring board can be placed at any wiring pattern position. There is an inner via hole connection method that can be connected, that is, an all-layer IVH structure resin multilayer substrate (see Patent Document 1). This is because it is possible to connect only necessary layers by filling the via holes of the multilayer printed wiring board and connect the necessary layers, and the inner via hole can be provided directly under the component land, so the board size is reduced. And high-density mounting can be realized. Further, 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. .

  Conventionally, a configuration in which the full-layer IVH structure resin multilayer substrate is manufactured through the processes shown in FIGS. 9A to 9H has been proposed.

  First, an electrically insulating substrate 1 is shown in FIG. Next, as shown in FIG. 9B, protective films 2 are attached to both sides of the electrically insulating substrate 1 by laminating. Subsequently, as shown in FIG. 9C, a through-hole 3 penetrating all of the electrically insulating substrate 1 and the protective film 2 is formed by a laser or the like. Next, after filling the through holes 3 with the conductive paste 4 as shown in FIG. 9 (d), the protective films 2 on both sides are peeled off as shown in FIG. 9 (e). In this state, a foil-like wiring material 5 is laminated from both sides as shown in FIG. 9 (f), and the wiring material 5 is heated and pressed in the step shown in FIG. 9 (g) to adhere to the electrically insulating substrate 1. Let At this time, the conductive paste 4 is compressed in the thickness direction by the heating and pressing step. By this compression, the conductive particles in the conductive paste are brought into contact with high density, and at the same time, the electrical connection between the wiring material 5 and the conductive paste 4 is realized. Next, the double-sided wiring substrate is completed by patterning the wiring material 5 as shown in FIG.

  Further, as an example in which the electrical connectivity with the conductive paste is further improved with respect to the wiring board shown in FIG. 9, a structure manufactured by the steps shown in FIGS. 11 (a) to (i). A holding wiring board has been proposed (see Patent Document 2).

First, when the protective films 2 are formed on both surfaces of the electrically insulating substrate 1 shown in FIG. 11A, the state shown in FIG. 11B is obtained. Next, as shown in FIG.11 (c), the through-hole 3 which penetrates the protective film 2 and the electrically insulating base material 1 is formed. Subsequently, as shown in FIG. 11 (d), the through-hole 3 is filled with the conductive paste 4. Then, the state shown in FIG.11 (e) is obtained by peeling the said protective film 2. FIG. After the protective film 2 is peeled off, a press sheet 6 is laminated on both surfaces of the electrically insulating substrate as shown in FIG. 11 (f), and the conductive paste 4 is compressed by heating and pressurizing, as shown in FIG. 11 (g). It will be in the state shown. Here, when a material having compressibility is used as the electrically insulating substrate 1, the electrically insulating substrate 1 is dimensionally shrunk in the thickness direction after heating and pressing. Next, when the press sheets 6 on both sides are removed, a state as shown in FIG. 11 (h) is obtained, and the conductive paste 4 is exposed on the surface of the electrically insulating substrate 1. Here, as a press sheet, the film which gave the mold release process to the surface of a heat-resistant film is used, and it removes by mechanical peeling. Subsequently, as shown in FIG. 11 (i), a plated wiring 7 to be coupled with the exposed conductive paste 4 is formed. For the wiring formation by plating, electroless plating or electrolytic plating is used. A double-sided wiring board is completed by this wiring pattern formation. The plated wiring formed so as to be bonded to the conductive particles in the conductive paste is excellent in strength at the bonding interface, and a wiring board that realizes stable interlayer connection can be provided.
Japanese Patent Laid-Open No. 06-268345 JP 2001-308534 A

  FIGS. 10A to 10C show the through hole 3 shown in FIGS. 9F to 9H in an enlarged manner. As shown in FIG. 10A, the conductive paste 4 after filling has a large amount of the resin 10 between the conductive particles 9 in the conductive paste, and sufficient electrical connection is not ensured. On the other hand, by applying heat and pressure through the wiring material 5, compression is applied to the conductive paste 4 and the conductive particles 9 in the conductive paste 4 come into close contact as shown in FIG. As a result, electrical connection in the conductive paste can be ensured. However, since the conductive paste 4 protrudes from the electrically insulating substrate 1 as shown in FIG. 10 (a), the surface portion of the conductive paste 4 is not heated when heated and pressed through the wiring material 5. The contact interface area between the spread wiring material 5 and the conductive paste 4 is widened. The spread of the conductive paste 4 changes depending on the protruding state of the conductive paste and the lamination conditions of the wiring material, and the variation becomes significant when processed with a large-sized electrically insulating substrate. As shown in FIG. 10C, it is necessary to design the wiring 11 covering the through hole 3 to be large, which is a factor that hinders high density.

  Further, when the protective film 2 is peeled off or during other manufacturing processes, a small amount of the conductive paste 4 may adhere to the electrically insulating substrate, and as shown in FIG. Exists as. When the wiring 11 becomes finer and the space between the wirings becomes narrower, the influence of the scattering paste 8 cannot be ignored, and in some cases, causes a short circuit failure.

  Further, when the via diameter is further reduced by the conventional configuration and manufacturing method, the contact point between the wiring material and the conductive particles in the conductive paste decreases in inverse proportion to the via area. As a result, a portion where the initial connection resistance value is high occurs, resulting in a problem that the initial connection resistance value varies greatly. In addition, a phenomenon in which the connection resistance value fluctuates in a reliability test such as a temperature cycle test or a pressure cooker test is observed in a portion where the initial connection resistance value is high.

  It is an object of the present invention to provide a wiring board and a method of manufacturing the wiring board that satisfy the requirements of via connectivity and insulation as well as miniaturizing wiring and vias in order to increase the density of the wiring board. It is.

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

  The invention according to claim 1 of the present invention includes an electrically insulating substrate, a through hole provided in the electrically insulating substrate, a conductive paste filled in the through hole, and a conductive paste in the electrically conductive paste. A wiring board electrically connected to the conductive particles, wherein the conductive particles and the plated wiring are connected to each other at a removal interface obtained by partially removing the conductive particles, and the conductive particles By connecting the plated wiring and the plated wiring at the conductive particle removal interface, it is possible to secure a wider connection interface area and improve the electrical connectivity, and as a result, a connection with a fine via can be realized.

  The invention according to claim 2 of the present invention is the wiring substrate according to claim 1, wherein the interface between the plated wiring and the resin in the conductive paste is a roughened shape, and the conductive contact with the plated wiring. By roughening the resin surface in the conductive paste, the adhesion between the plated wiring and the resin can be improved, and as a result, the stress applied to the interface between the conductive particles and the plated wiring can be dispersed and the via connectivity can be improved. Can do.

  The invention according to claim 3 of the present invention is the wiring board according to claim 1, wherein the interface between the plated wiring and the conductive paste is recessed from the surface of the electrically insulating base material. By setting the region where the hole is filled with the conductive paste as an intermediate portion in the thickness direction of the electrically insulating substrate, the substantial diameter of the through hole can be reduced, and finer via connection can be realized.

  The invention according to claim 4 of the present invention is the wiring board according to claim 1, wherein a plurality of protrusions are formed in the plated wiring, and the protrusions are embedded in the conductive paste. By embedding the protruding part of the plated wiring in the conductive paste, the adhesion effect between the plated wiring and the conductive paste can be enhanced by the anchor effect, and a wide connection interface area between the conductive paste can be secured, so via connection Can be improved.

  The invention according to claim 5 of the present invention is such that at least a part of the protruding portion of the plated wiring has a shape in which the cross section perpendicular to the protruding direction is not constant, and the area of the cross section is the bottom and tip of the protruding portion 5. The wiring board according to claim 4, wherein the anchor effect between the conductive paste and the plated wiring can be further enhanced, and as a result, the via connectivity can be improved.

  The invention according to claim 6 of the present invention is the wiring board according to claim 3, wherein the plated wiring on the through hole is thicker than the plated wiring formed other than the through hole. By forming the wiring thicker, it is possible to increase the rigidity of the plated wiring, which enables deformation of the interface between the plated wiring and the conductive paste even when external stress is generated when electronic components are mounted. It is possible to suppress the deterioration of via connectivity.

  The invention according to claim 7 of the present invention is the wiring board according to claim 3, wherein the surface of the plated wiring on the through hole is flat, and the surface of the plated wiring on the through hole is flat. As a result, the connectivity with solder balls, which are connection terminals of electronic components such as BGA and CSP, is improved. As a result, a via-on-pad structure in which the connection terminals with the solder balls are arranged in the through holes can be realized.

  The invention according to claim 8 of the present invention is a multilayer wiring board including at least one wiring board according to claim 1, wherein the wiring board is multilayered by the connection structure according to claim 1. Even in this case, a finer via can be provided.

  The invention according to claim 9 of the present invention includes a step of forming a through hole in an electrically insulating base material containing a thermosetting resin, a step of filling the through hole with a conductive paste, and the electrically insulating group. A hot pressing step of heating and pressing the material and the conductive paste to cure the electrically insulating substrate, a step of partially removing conductive particles in the conductive paste, and electrically connecting the conductive paste to the conductive paste Forming a wiring to be connected, and in the wiring forming step, a method of manufacturing a wiring board that forms a plated wiring that adheres to the electrically insulating base material and bonds with conductive particles in a conductive paste on at least one side Therefore, by connecting the conductive particles to the plated wiring at the conductive particle removal interface, it is possible to secure a wider area of the connection interface and improve the electrical connectivity. Connection with finer vias can be realized.

  Invention of Claim 10 of this invention is a manufacturing method of the wiring board of Claim 9 which removes the electroconductive particle outside a through-hole by the partial removal process of the said electroconductive particle, Comprising: By removing the paste remaining outside the through-hole on the electrically insulating substrate at the same time as the step of removing the conductive particles, it is possible to suppress short-circuit defects between the wires and realize a finer wiring interval Can do.

  According to an eleventh aspect of the present invention, in the partial removal step of the conductive particles, a plurality of stages of conductive particles are removed in the depth direction of the conductive paste. In this method, a plurality of stages of conductive particles are removed in the depth direction of the conductive paste, thereby forming a protruding portion of the plated wiring embedded in the conductive paste in the subsequent plated wiring forming step. As a result, the adhesion between the plated wiring and the conductive paste can be increased by the anchor effect, and a wide connection interface area with the conductive paste can be secured, so that via connectivity can be improved.

  The invention according to claim 12 of the present invention is the method for manufacturing a wiring board according to claim 9, wherein in the step of partially removing the conductive particles, the conductive particles are removed by dissolution. By removing by dissolving, the conductive particles can be partially removed by a simple method.

  The invention according to claim 13 of the present invention is the method for manufacturing a wiring board according to claim 9, wherein the wiring forming step includes a step of roughening the resin in the electrically insulating base material and the conductive paste. Thus, it is possible to improve the adhesion between the resin in the conductive paste of the plated wiring and the electrically insulating substrate.

  According to a fourteenth aspect of the present invention, the wiring forming step includes a step of forming a seed layer on the entire surface of the electrically insulating substrate, a step of forming a plating resist pattern, and a step of performing electrolytic plating. And a step of removing the plating resist pattern and a step of removing the seed layer. 10. The method of manufacturing a wiring substrate according to claim 9, wherein the conductive layer in the conductive paste is formed by such a wiring forming method. The plated wiring bonded to the particles can be formed more finely.

  According to a fifteenth aspect of the present invention, the wiring forming step includes a step of performing a catalyst treatment on the entire surface of the electrically insulating substrate, a step of forming a plating resist pattern, and a step of performing electroless plating. And a step of removing the plating resist pattern. 10. A method of manufacturing a wiring board according to claim 9, wherein a plating wiring combined with the conductive particles in the conductive paste is obtained by such a wiring forming method. It can be formed finely.

  According to the sixteenth aspect of the present invention, in the hot pressing step, the metal foil that can be removed with the same chemical solution as the chemical solution for removing the conductive particles in the conductive paste is used for the plating wiring of the electrically insulating substrate. The wiring board manufacturing method according to claim 9, wherein the electrically insulating base material is cured with respect to a surface on which the metal foil is formed, and by setting the material of the metal foil in this way, At the same time in the removing step, the conductive particles can be partially removed, and a manufacturing method with excellent productivity can be realized.

  The invention according to claim 17 of the present invention includes a thermosetting resin in the conductive paste, and compresses the conductive paste in the hot press step while the electrically insulating base material and the conductive paste. The method of manufacturing a wiring board according to claim 9, wherein the contact between the conductive particles is further improved by curing while compressing the conductive paste in the through hole in the hot press process, and the result As a result, via connection with excellent connection reliability can be realized.

  According to the present invention, by forming plated wiring on a conductive paste from which conductive particles have been partially removed, vias and wiring can be further refined, and via connectivity and insulating properties are satisfied. A wiring board and a manufacturing method thereof can be provided.

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

(Embodiment 1)
1A to 1J show the manufacturing process of the wiring board according to the present invention.

  First, the electrically insulating substrate 1 shown in FIG. 1A is a composite material of fiber and resin, and glass fiber or organic fiber is impregnated with epoxy resin, polyimide resin, BT resin, PPE resin, PPO resin or the like. Adhesives are formed on both sides of the material and materials such as polyimide, aramid, PTFE, LCP and other porous films impregnated with epoxy resin, polyimide resin, BT resin, PPE resin, PPO resin, etc., polyimide, aramid, LCP film Materials can be used.

  More preferably, the electrically insulating substrate 1 is provided with a feature of being a compressible porous substrate. That is, it is a material whose dimensions shrink when compression is applied in the thickness direction of the electrically insulating substrate. The degree of shrinkage can be adjusted by controlling the pores formed in the electrically insulating substrate. As a material for such an electrically insulating substrate, a fiber paper such as a woven fabric or a nonwoven fabric impregnated with a resin can be used, and pores are simultaneously formed during the impregnation. If a non-woven paper mainly composed of aramid fibers is used as the paper and a thermosetting resin mainly composed of epoxy is used as the resin, the pores in the electrically insulating substrate can be formed uniformly and efficiently. An insulating base with high compressibility can be obtained.

  Next, as shown in FIG. 1B, protective films 2 are formed on both surfaces of the electrically insulating substrate 1. Using a film mainly composed of PET or PEN as the protective film 2 and laminating it on both surfaces of the electrically insulating substrate 1 is a simple and highly productive manufacturing method.

  Next, as shown in FIG.1 (c), the through-hole 3 which penetrates the protective film 2 and the electrically insulating base material 1 is formed. The through-hole 3 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, a through hole having a diameter of 100 μm can be formed in an electrically insulating substrate having a thickness of 80 μm. Further, when a third harmonic of a YAG laser is used, a 30 μm diameter through-hole can be formed in a 30 μm thick electrically insulating substrate.

  Subsequently, as shown in FIG. 1 (d), the through-hole 3 is filled with a conductive paste 4. The conductive paste 4 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 2 plays a role of protecting the conductive paste 4 from adhering to the surface of the electrically insulating base material 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.

  By peeling off the protective film, the state shown in FIG. The conductive paste 4 has a filling amount secured by the protective film 2. That is, the conductive paste 4 is protruded from the surface of the electrically insulating substrate 1 by the height of the thickness of the protective film 2. Here, when the thickness of the protective film 2 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 2 is peeled can be suppressed.

  After peeling this protective film 2, as shown in FIG.1 (f), the press sheet 6 is laminated | stacked on both surfaces of an electrically insulating base material, and the electrically conductive paste 4 is compressed by heat press with a hot press. When a material having compressibility is used as the electrically insulating substrate, the electrically insulating substrate 1 undergoes dimensional shrinkage in the thickness direction in the heating and pressing step.

  Here, FIGS. 2A to 2E are enlarged views of the vicinity of the through hole in FIGS. 1F to 1J. As shown in FIG. 2A, the conductive paste 4 after filling has a large amount of the resin 10 between the conductive particles 9 in the conductive paste, and sufficient electrical connection is not ensured. On the other hand, as shown in FIG. 1 (g) and FIG. 2 (b), by applying heat and pressure through the press sheet 6, the conductive paste 4 is compressed, and the conductive particles in the conductive paste are removed. It will be in close contact and electrical connection within the conductive paste can be ensured. 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 addition, as described above, a small amount of the conductive paste 4 may adhere on the electrically insulating substrate when the protective film 2 is peeled off or during other manufacturing steps, as shown in FIG. Thus, it exists as the scattering paste 8. After the scattering paste is pressed, it adheres to the surface of the electrically insulating substrate 1 as shown in FIG.

  On the other hand, since the conductive paste 4 protrudes before lamination, when heated and pressed through the press sheet 6 as shown in FIG. The contact interface area of the conductive paste 4 will be expanded.

  Next, when the press sheets 6 on both sides are removed, a state as shown in FIGS. 1 (h) and 2 (c) is obtained. As the press sheet 6, a film obtained by subjecting the surface of the heat-resistant film to mold release treatment can be used. In this case, the press sheet can be mechanically peeled off. Further, as the press sheet, a metal foil made of a material different from the conductive particles in the conductive paste 4 can be used. In this case, only the metal foil can be removed by etching. Here, by selecting a chemical for etching the metal foil, the press sheet can be removed without eroding the conductive particles in the conductive paste. Further, since the mechanical stress is not applied to the conductive paste by chemically removing the press sheet, the conductive state in the conductive paste is not deteriorated during the process. As an example, when the conductive particles 9 are copper powder, the aluminum foil can be selectively removed by using an aluminum foil as a press sheet and using hydrochloric acid or a sodium hydroxide aqueous solution heated to 70 ° C.

  Since the surface shape of the press sheet is transferred to the surface of the electrically insulating substrate and conductive paste, the surface of the electrically insulating substrate and the conductive paste is roughened by this shape transfer. Can be

  Next, as shown in FIGS. 1 (i) and 2 (d), the conductive particles 9 contained in the conductive paste 4 in the through holes 3 are partially removed from the exposed surface. By this removal step, the conductive paste 4 can be formed in a concave shape from the surface of the electrically insulating substrate 1 and the conductive paste 4 spreading near the surface of the electrically insulating substrate can be removed. Can be reduced.

  In addition, by this removing step, the conductive particles 9 in the conductive paste 4 are exposed on the surface of the through hole in a wider area. As this removal step, it can be removed mechanically by a method such as sand blasting or water blasting, but it is easy to remove by immersion or spray etching using a chemical solution in which the conductive particles 9 dissolve, It is more preferable in that no foreign matter such as processing dust is mixed. As an example of a chemical solution for removing the conductive particles 9, when copper powder is used for the conductive particles 9, it is dissolved in iron chloride, copper chloride, sulfuric acid and hydrogen peroxide mixed solution, alkaline etching solution, ammonium persulfate. Can be removed.

  Further, since the resin 10 exists around the conductive particles 9, the step of removing the resin 10 is performed together, and when the steps of removing the conductive particles 9 and the resin 10 are repeated, The depth of the exposed surface of the conductive paste 4 can be controlled. For the removal of the resin 10, a general desmear liquid can be used. As an example, a mixed liquid of potassium permanganate and sodium hydroxide is heated to 60 ° C. and treated by an immersion method. At this time, the surface of the resin 10 is roughened, and at the same time, the surface of the electrically insulating substrate 1 can be roughened. In addition, although the method of roughening the surface of the resin 10 and the electrically insulating base material 1 by the treatment of the chemical solution has been described here, the same roughening can also be performed by a mechanical method such as sand blasting or water blasting. Can do.

  Here, the state of the surface of the through hole after partially removing the conductive particles 9 is schematically shown in FIG. As the through-hole 3, the substantially circular shape that is the through-hole processed shape described above is maintained, and the irregular spreading of the conductive paste 4 can be suppressed. As a result, the variation in the diameter of the through-hole when processing with a large-sized electrically insulating base material is substantially reduced, so that the clearance between the through-hole and the wiring portion covering the through-hole can be reduced. As a result, the wiring board High density can be realized.

  In the state where the press sheet is removed, since the thin film of the resin 10 covers the surface of the conductive paste, the conductive particles 9 are exposed because the press sheet and the conductive particles are in close contact during pressing. Only. However, as shown in FIG. 3, the exposed area can be expanded by the partial removal process of the conductive particles 9.

  Further, in the partial removal step of the conductive particles, it is more preferable to simultaneously remove the scattering paste 8 fixed to the surface of the electrically insulating substrate 1 as shown in FIG. As a result, short-circuit defects between wirings can be suppressed, and finer wiring intervals can be realized.

  In addition, it is more preferable at the point which can use a metal foil as the press sheet 6 and melt | dissolve this metal foil and the electroconductive particle in an electroconductive paste with the same chemical | medical solution with a manufacturing process. As an example, a copper foil can be used as the press sheet 6 and a copper powder can be used as the conductive particles 9. In this case, a copper etchant (iron chloride, copper chloride, sulfuric acid and hydrogen peroxide solution mixture, alkaline etching solution, ammonium persulfate, etc.) can be used as the chemical solution. As another example, when aluminum foil is used as the press sheet 6 and copper powder is used for the conductive particles 9, iron chloride or copper chloride can be used.

  Subsequently, as shown in FIGS. 1 (j) and 2 (e), a plated wiring 7 coupled to the exposed conductive paste 4 is formed. Here, the conductive particles 9 are partially removed, so that the conductive particles are exposed as a removal interface in a wide area on the surface of the conductive paste on the through hole before the plating wiring is formed. At this removal interface, strong metallic bonding with the plated wiring can be realized.

  Electroless plating and electrolytic plating are used for wiring formation by this plating. It is important for the plated wiring 7 shown here to be metallically bonded to the conductive particles 9. As an example, the conductive particles 9 are made of copper powder, subjected to Pd catalyst treatment, and then electroless copper plated as the plated wiring. This combination can be realized by using. The wiring pattern can be formed by forming a wiring material on the entire surface by electroless plating and then patterning it by etching. If the electroplating is used together on the electroless plating base layer instead of the electroless plating process on the entire surface, a thick film can be formed in a short time and the productivity is excellent. In addition, when electrolytic plating is used in combination, the use of a solution prepared with an additive for via fill as the electrolytic plating solution increases the plating deposition rate on the recessed through hole, as shown in FIG. Furthermore, it is possible to make the plated wiring surface flat. Since the surface of the plated wiring on the through hole becomes flat, the connectivity with the solder ball, which is a connection terminal for electronic parts such as BGA and CSP, is improved. As a result, the connection terminal with the solder ball is placed on the through hole. A via-on-pad structure can be realized.

  Also, as shown in FIG. 2 (e), by forming the plated wiring on the through-hole thicker, it is possible to increase the rigidity of the plated wiring, thereby generating an external component generated when an electronic component is mounted. Even when stress is applied, the deformation of the interface between the plated wiring and the conductive paste can be suppressed, and the deterioration of the via connectivity can be suppressed.

  Plating wiring formed to bond with conductive particles in conductive paste in this way has excellent strength at the bonding interface, even when mechanical stress is applied such as mounting electronic parts on the wiring There is a feature that cracks hardly occur at the bonding interface with the conductive paste. That is, by increasing the bond strength between the wiring and the conductive paste rather than the bond strength between the conductive particles in the conductive paste, relaxation when stress is generated can be realized inside the conductive paste. Since the conductive particles are in three-dimensional high density contact inside the conductive paste, even if the position of the conductive particles changes due to stress, the state of electrical connection is not deteriorated. As a result, a wiring board that realizes stable interlayer connection can be provided.

  Further, in the above-described partial removal step of conductive particles, when the conductive particles are dissolved and removed using a chemical solution, if the treatment time with the chemical solution is lengthened, the conductive particles exposed on the surface portion are removed. It will not dissolve completely. Here, when the treatment is continued, the chemical solution comes into contact with adjacent conductive particles that have been in high density contact with the completely removed conductive particles, and partial removal of the conductive particles is continuously performed. That is, local depressions are formed in the depth direction of the conductive paste. When plated wiring is formed on the surface of the conductive paste, the state shown in FIG. 4 is obtained. FIG. 4 shows an enlarged interface portion of the electrically insulating substrate 1, the conductive paste 4, and the plated wiring 7. Since the plated wiring is formed in the above-described local depression formed in the space where the conductive particles are dissolved and removed, a local protrusion is formed on the plated wiring. The local protrusion is formed by infiltration of the chemical solution and has a shape in which the cross section perpendicular to the protrusion direction is not constant, and the area of the cross section may be maximized between the bottom and the tip of the protrusion. it can. As a result, the anchor effect between the conductive paste and the plated wiring can be further enhanced, and a wide contact area can be ensured. As a result, the via connectivity can be improved.

  Further, an example of a connection interface between the plated wiring 7 and the conductive paste 4 is further enlarged and shown in FIG. FIG. 5 shows an example in which partial removal of the conductive particles 9 and removal of the resin 10 are combined. The conductive particles 9 are partially removed at the contact interface with the plating wiring 7 and are bonded to the plating wiring 7 at the removal interface 13. Further, the resin 10 in the conductive paste 4 has a roughened portion 12 formed on the surface by the removal process of the resin 10, and the resin 10 and the plated wiring 7 are firmly adhered. In other words, by roughening the resin surface in the conductive paste that comes into contact with the plated wiring, the adhesion between the plated wiring and the resin is improved. As a result, the stress applied to the interface between the conductive particles and the plated wiring is dispersed, and via connection is achieved. It is possible to improve the performance.

(Embodiment 2)
Next, another embodiment of the method for forming a plated wiring according to the present invention will be described. 6A to 6F show the main manufacturing process of the wiring board according to the present embodiment. Here, FIG. 6A is the same state as FIG. 1I already described, and is formed by the manufacturing method shown in FIGS. 1A to 1H.

  FIG. 6A shows a state where the conductive particles in the conductive paste 4 have been partially removed. After the Pd catalyst treatment is subsequently performed on the surface of the electrically insulating substrate 1, seeding is performed by electroless plating. When the layer 14 is formed, the state shown in FIG. This seed layer is metallically bonded to the conductive particles in the exposed conductive paste.

  Here, the thickness of the electroless plating is preferably 5 μm or less in terms of forming a fine wiring. For example, when forming a fine wiring with a pitch of 40 μm, electroless copper plating with a thickness of 1 μm was performed.

  Next, when the plating resist 15 is formed on the surface of the seed layer 14, the state shown in FIG. This plating resist is preferably an exposure and development type in that a fine pattern is formed, and may be a dry film type or a liquid type. On the other hand, when making the wiring thick, it is more preferable to use a dry film type. As an example, when forming a wiring having a thickness of 12 μm, a dry film resist having a thickness of 15 μm is used.

  Subsequently, when electrolytic plating is performed on the exposed seed layer 14, the state shown in FIG. 6D is obtained. Here, electrolytic copper plating was performed as electrolytic plating, and the thickness was set to 13 μm so as to be equal to or less than the above-described plating resist thickness. Next, as shown in FIG. 6E, when the plating resist 15 is removed and the exposed seed layer 14 is removed, the state shown in FIG. 6F is obtained. For this seed layer removal, a copper etching solution such as copper chloride, iron chloride, ammonium persulfate or the like can be used, but spray spraying is more preferable in that the seed layer between narrower wirings can be removed.

  In the above example, the seed layer 14 is formed by electroless plating, but the same effect can be obtained by using a thin film forming method such as vacuum deposition or sputtering instead of electroless plating.

  In the above manufacturing method, the seed layer is etched on the wiring patterned by electrolytic plating. The etching amount may be the thickness of the thin seed layer, and the thinning of the wiring width patterned by electrolytic plating is the seed. It is suppressed to the thickness of the layer. That is, finer wiring can be formed as compared with the example shown in the first embodiment.

(Embodiment 3)
Next, another embodiment of the method for forming a plated wiring according to the present invention will be described. 7A to 7D show the main manufacturing process of the wiring board according to the present embodiment. Here, FIG. 7A is the same state as FIG. 1I described above, and is formed by the manufacturing method shown in FIGS. 1A to 1H. Note that portions overlapping with those already described in Embodiment 2 will be described in a simplified manner.

  First, FIG. 7A shows a state in which the conductive particles in the conductive paste 4 are partially removed. Subsequently, the surface of the electrically insulating substrate 1 is subjected to Pd catalyst treatment, and the plating resist 15 is removed. When formed, the state shown in FIG. For this plating resist, a material similar to that already shown in the second embodiment can be used.

  Next, as shown in FIG. 7C, the plated wiring 7 is formed in the opening of the plating resist 15 by electroless plating. Here, electroless copper plating was used as electroless plating. Further, the plating wiring 7 is formed so as to be thinner than the plating resist 15 as in the second embodiment. Next, when the plating resist 15 is removed and the Pd catalyst remaining under the plating resist 15 is removed, the state shown in FIG. 7D is obtained. Here, a commercially available chemical solution may be used for removing Pd, and the surface of the electrically insulating substrate 1 is dissolved and removed very thinly with a mixed solution of potassium permanganate and sodium hydroxide, and the Pd together with the resin. May be removed.

  In the above manufacturing method, after pattern plating is performed, it is not necessary to etch the seed layer as in the example shown in the second embodiment, and the pattern plating dimensions are directly used as the wiring width, so that the accuracy is higher. In this way, fine wiring can be formed.

(Embodiment 4)
Although the first to third embodiments have been described using the example of the double-sided board, the number of layers of the wiring board is not limited to this, and the same effect can be obtained for the multilayer board. FIG. 8 shows an example of a multilayer wiring board including the wiring board of the present invention. 8A to 8D show the main manufacturing steps. Note that the same portions as those already described will be described in a simplified manner.

  In FIG. 8A, a wiring board 16, an electrically insulating base material 1 filled with the conductive paste 4 (the same state as in FIG. 1E), and a press sheet 6 are laminated. It is in the state. In this figure, a four-layer board having an all-layer IVH structure is shown as the wiring board 16, but the wiring board is not limited to this, and the number of layers may be different, and a board having through-through holes may be used. A wiring board having another structure such as a structure may be used. Next, when the electrical insulating substrate 1 is cured by heating and pressing in a hot press step, the state shown in FIG. 8B is obtained. Subsequently, when the press sheet 6 on the surface is removed and the conductive particles in the conductive paste are partially removed from the exposed conductive paste 4, the state shown in FIG. 8C is obtained. Next, when the plated wiring 7 is formed on the surface of the electrically insulating base material, the multilayer wiring board shown in FIG. 8D is completed. As a method for forming the plated wiring, the method described in the above embodiment can be arbitrarily used. Moreover, about the structure of a multilayer wiring board, you may make it the structure which repeats the said process in multiple times and includes the wiring board of this invention by multilayer structure. By such a manufacturing method, a multilayer wiring board provided with the fine via and fine wiring of the present invention can be provided.

  The wiring board and the manufacturing method of the wiring board according to the present invention can be further miniaturized vias and wirings by forming plated wirings on conductive paste from which conductive particles have been partially removed. It is possible to provide a wiring board satisfying connectivity and insulating characteristics and a method for manufacturing the wiring board. That is, the present invention is useful for high-density wiring boards.

(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)-(e) Process sectional drawing which expanded and showed the main processes of the manufacturing method of the wiring board in Embodiment 1 of this invention. External view showing a through hole surface after the step of partially removing conductive particles in Embodiment 1 of the present invention Sectional drawing which expanded partially the through-hole surface vicinity of the wiring board in Embodiment 1 of this invention Sectional drawing which expanded and showed the plating wiring and electroconductive paste interface of the wiring board in Embodiment 1 of this invention (A)-(f) Process sectional drawing which showed the manufacturing method of the wiring board in Embodiment 2 of this invention for every main process. (A)-(d) Process sectional drawing which showed the manufacturing method of the wiring board in Embodiment 3 of this invention for every main process. (A)-(d) Process sectional drawing which showed the manufacturing method of the wiring board in Embodiment 4 of this invention for every main process. (A)-(h) Process sectional drawing which showed the manufacturing method of the conventional wiring board for every main process (A)-(c) Process sectional drawing which expanded and showed the main process in the manufacturing method of the conventional wiring board (A)-(i) Process sectional drawing which showed the manufacturing method of the conventional wiring board for every main process

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrically insulating base material 2 Protective film 3 Through-hole 4 Conductive paste 5 Wiring material 6 Press sheet 7 Plating wiring 8 Spattering paste 9 Conductive particle 10 Resin 11 Wiring 12 Roughening part 13 Removal interface 14 Seed layer 15 Plating resist 16 Wiring board

Claims (17)

An electrically insulating substrate, a through hole provided in the electrically insulating substrate, a conductive paste filled in the through hole, and a plated wiring electrically connected to the conductive particles in the conductive paste; And the conductive particles and the plated wiring are connected at a removal interface obtained by partially removing the conductive particles. The wiring board according to claim 1, wherein an interface between the plated wiring and the resin in the conductive paste has a roughened shape. The wiring board according to claim 1, wherein an interface between the plated wiring and the conductive paste is recessed from the surface of the electrically insulating base material. The wiring board according to claim 1, wherein a plurality of protrusions are formed in the plated wiring, and the protrusions are embedded in the conductive paste. The projection part of at least one part of the said plating wiring has a shape where the cross section perpendicular | vertical to a protrusion direction is not constant, The area of the said cross section becomes the maximum between the bottom and front-end | tip of a protrusion part. Wiring board. The wiring board according to claim 3, wherein the plated wiring on the through hole is thicker than the plated wiring formed other than the through hole. The wiring board according to claim 3, wherein the plated wiring on the through hole has a flat surface. A multilayer wiring board comprising at least one wiring board according to claim 1. Forming a through hole in an electrically insulating substrate containing a thermosetting resin;
Filling the through hole with a conductive paste;
A heat pressing step of heating and pressurizing the electrically insulating substrate and the conductive paste to cure the electrically insulating substrate;
Partially removing conductive particles in the conductive paste;
Forming a wiring electrically connected to the conductive paste,
A method of manufacturing a wiring board, wherein in the wiring formation step, a plated wiring that adheres to the conductive particles in the conductive paste while being attached to the electrically insulating substrate is formed on at least one side. The method for manufacturing a wiring board according to claim 9, wherein the conductive particles outside the through hole are removed in the partial removal step of the conductive particles. The method for manufacturing a wiring board according to claim 9, wherein in the step of partially removing the conductive particles, a plurality of stages of conductive particles are removed in a depth direction of the conductive paste. The method for manufacturing a wiring board according to claim 9, wherein in the step of partially removing the conductive particles, the conductive particles are removed by dissolution. The method for manufacturing a wiring board according to claim 9, wherein the wiring forming step includes a step of roughening the resin in the electrically insulating base material and the conductive paste. The wiring forming step includes a step of forming a seed layer over the entire surface of the electrically insulating substrate, a step of forming a plating resist pattern, a step of performing electroplating, a step of removing the plating resist pattern, The method for manufacturing a wiring board according to claim 9, further comprising a step of removing the layer. The wiring formation step includes a step of performing a catalyst treatment on the entire surface of the electrically insulating substrate, a step of forming a plating resist pattern, a step of performing electroless plating, and a step of removing the plating resist pattern. The manufacturing method of the wiring board of Claim 9. In the hot pressing step, a metal foil that can be removed with the same chemical solution as the chemical solution for removing the conductive particles in the conductive paste is laminated on the surface of the electrically insulating substrate on which the plated wiring is formed, and the electric The method for manufacturing a wiring board according to claim 9, wherein the insulating substrate is cured. The wiring board according to claim 9, wherein the electrically conductive paste includes a thermosetting resin, and the electrically insulating base material and the electrically conductive paste are cured while compressing the electrically conductive paste in the hot pressing step. Production method.

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