JP2015201635A - Multilayer wiring board manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer wiring board which can maintain electrical continuity between wiring layers well by an interlayer connection body to achieve excellent reliability.SOLUTION: A multilayer wiring board manufacturing method comprises the steps of: applying a conductive paste on a first metal foil to form a bump composed of the conductive paste; subsequently depressing a second metal foil to the first metal foil via an insulation resin layer without containing fibrous filler at a first temperature to fluidize the insulation resin layer to remove the insulation resin layer remaining on an upper end of the bump; subsequently depressing the second metal foil to the first metal foil via the insulation resin layer at a second temperature higher than the first temperature to cure the insulation resin layer and the bump and laminate the second metal foil on the insulation resin layer.

Description

  The present invention relates to a method for manufacturing a multilayer wiring board.

  In recent years, electronic devices are required to have higher density and higher functionality in the trend of higher performance and smaller size. From this point of view, even modules with circuit components are required to support high density and high functionality. In order to meet such demands, multilayer wiring boards are now being actively performed.

  In such a multilayer wiring board, a plurality of wiring layers are arranged so as to be substantially parallel to each other, an insulating member is disposed between the wiring layers, and an interlayer connection body (via) that penetrates between the insulating members in the thickness direction. And a plurality of wiring layers are electrically connected to each other.

  The multilayer wiring board as described above can be formed by the following method. For example, a conductive paste containing a metal such as Ag is applied to the first metal foil by a method such as screen printing to form bumps, and after drying the bumps, a device such as a roll laminator or a vacuum laminator is installed. The insulating resin layer is press-formed on the metal foil so that the bumps penetrate in the thickness direction. Next, a second metal foil is further laminated on the insulating resin layer, and the second metal foil is bonded to the upper end portion of the bump penetrating the insulating resin layer by applying pressure under heating with a press device ( Laminating press).

  Thus, the first metal foil and the second metal foil constitute a wiring layer, the insulating resin layer constitutes an insulating member interposed between these wiring layers, and the bump constitutes an interlayer connection (via). Thus, a multilayer wiring board can be obtained (see Patent Document 1, etc.).

  Further multilayering can be realized by repeating the above-described steps and sequentially forming bumps, an insulating resin layer (insulating member) and a metal foil on the second metal foil.

  However, the insulating member constituting the multilayer wiring board, that is, the insulating resin layer generally contains glass cloth or the like. Therefore, when the first laminated press as described above is performed, the bump does not completely penetrate the insulating resin layer in the thickness direction, and the upper end portion thereof is covered with a part of the insulating resin layer. There is. As a result, in the second lamination press, the insulating resin layer remains between the upper end of the bump and the second metal foil, and between the upper end of the interlayer connection body of the completed multilayer wiring board and the wiring layer. Some insulating members may remain.

  As a result, it becomes difficult to hold the wiring layers separated by the insulating member in an electrically conductive state by the interlayer connector, and the electrical characteristics of the multilayer wiring board deteriorate and the reliability thereof decreases. There was a problem.

Japanese Patent No. 5182421

  It is an object of the present invention to provide a multilayer wiring board that can sufficiently maintain electrical continuity between wiring layers by an interlayer connection body and has excellent reliability.

In order to achieve the above object, the present invention provides:
Applying a conductive paste on the first metal foil and forming a bump made of the conductive paste;
The second metal foil is pressed against the first metal foil through an insulating resin layer that does not contain a fibrous filler at a first temperature to fluidize the insulating resin layer, and the upper end of the bump Removing the insulating resin layer remaining in the part, exposing the upper end of the bump from the insulating resin layer;
The second metal foil is pressed against the first metal foil via the insulating resin layer at a second temperature higher than the first temperature, and the insulating resin layer and the bump are Curing, and laminating the second metal foil on the insulating resin layer;
It is related with the manufacturing method of a multilayer wiring board characterized by comprising.

  According to the present invention, after the bump made of the conductive paste is formed on the first metal foil, the second metal foil is passed through the insulating resin layer not containing the fibrous filler with respect to the first metal foil. The pressing is performed at the first temperature. At this time, since the viscosity of the insulating resin layer decreases and fluidizes as the temperature rises, the insulating resin layer remaining on the upper end portion of the bump during pressing is eliminated, and the upper end portion is insulated with the insulating resin layer. Be exposed from the layer.

  Therefore, when the second metal foil is pressed against the first metal foil again at a second temperature higher than the first temperature and the lamination press is performed later, the second metal foil is separated from the insulating resin layer. As a result, the first metal foil and the second metal foil, which later become wiring layers, are electrically connected with high reliability. Get connected. As a result, the electrical connection between the wiring layers can be sufficiently retained by the interlayer connector (via), and a multilayer wiring board having excellent reliability can be provided.

  In the present invention, the insulating member that constitutes the multilayer wiring board is formed of an insulating resin layer that does not contain a fibrous filler, and is heated and fluidized at the first temperature to remain at the upper end of the bump. The insulating resin layer is excluded, and the upper end portion is exposed from the insulating resin layer. Therefore, unlike the conventional case, when the insulating resin layer is press-formed on the first metal foil, a step of penetrating the bumps with respect to the insulating resin layer can be omitted.

  Moreover, in this invention, since the insulating member which comprises a multilayer wiring board is comprised from the insulating resin layer which does not contain a fibrous filler, the thickness of an insulating member can be reduced. Therefore, miniaturization and high density of the multilayer wiring board can be achieved.

  In the present invention, the “upper end portion of the bump” refers to a part of the bump region that is coupled to the second metal foil, that is, the wiring layer.

  The insulating resin layer is required not to contain a fibrous filler, and for example, a particulate or powdery filler may be included.

  In an example of the present invention, the conductive paste constituting the bump can be a conductive paste containing at least Sn, Bi, Cu, and Ag. In this case, after forming a bump made of a conductive paste and drying it as appropriate, an insulating resin layer not containing a fibrous filler is disposed on the first metal foil and heated, and the upper end of the bump is insulated resin. After being exposed from the layer, when the second metal foil is pressed under heat through the insulating resin layer, among the metals constituting the bump, Sn Bi and Cu function as a sintering aid. For example, a liquid phase is formed by the heating, and the bump becomes a metal sintered body of at least Sn, Bi, Cu, and Ag containing a binder component such as a resin.

  As a result, as compared with the case where particles such as silver are contained in the bumps (heat-cured vias) constituting the multilayer wiring board as in the prior art, the bumps (vias) due to the reduction in the interface between the particles are reduced. Since the surface area is reduced, it is possible to suppress the problem that the conductor loss due to the skin effect is reduced during high-speed transmission and signal delay occurs.

  In one example of the present invention, the bump can be conical. In this case, when the insulating resin layer is heated and fluidized at the first temperature, the insulating resin layer more easily flows from the upper end portion of the bump. Therefore, the insulating resin layer remaining on the upper end portion is more effective. Can be eliminated and removed.

  As described above, according to the present invention, the electrical connection between the wiring layers can be sufficiently maintained by the interlayer connector, and a multilayer wiring board having excellent reliability can be provided.

It is sectional drawing for demonstrating the manufacturing method of the multilayer wiring board of 1st Embodiment. It is sectional drawing for demonstrating the manufacturing method of the multilayer wiring board of 1st Embodiment. It is sectional drawing for demonstrating the manufacturing method of the multilayer wiring board of 1st Embodiment. It is sectional drawing for demonstrating the manufacturing method of the multilayer wiring board of 1st Embodiment. It is sectional drawing for demonstrating the manufacturing method of the multilayer wiring board of 1st Embodiment. It is sectional drawing for demonstrating the manufacturing method of the multilayer wiring board of 2nd Embodiment. It is sectional drawing for demonstrating the manufacturing method of the multilayer wiring board of 2nd Embodiment.

  Hereinafter, specific features of the present invention will be described based on embodiments for carrying out the invention.

(First embodiment)
1 to 5 are cross-sectional views for explaining a method for manufacturing a multilayer wiring board according to the present embodiment. In order to clarify the features of the present embodiment, an area near one bump is enlarged and shown. ing.

  First, as shown in FIG. 1, a conductive paste is applied on the first metal foil 11 by an arbitrary method such as a screen printing method, a dispensing method, or an ink jet method, and bumps 12 made of the conductive paste are applied. Form.

  Since the first metal foil 11 will later constitute the wiring layer of the multilayer wiring board, it is made of a good electrical conductor such as copper (Cu), gold (Au), silver (Ag), or aluminum (Al). The thickness t1 of the first metal foil 11 is, for example, 1.5 μm to 40 μm.

  The conductive paste constituting the bumps 12 is, for example, conductive powder such as silver, gold, copper, tin, bismuth and Ag solder powder, alloy powder or composite (mixed) metal powder, and epoxy resin, phenol resin, A conductive composition prepared by mixing a binder component such as polyimide resin, polysulfone resin, polyester resin, or polycarbonate resin is used.

  When the conductive paste contains copper, tin, or bismuth, as described below, a bump made of the conductive paste is formed, dried appropriately, and then contains a fibrous filler with respect to the first metal foil. When the second metal foil is pressed under heat through the insulating resin layer after the upper insulating resin layer is exposed and heated, and the upper end of the bump is exposed from the insulating resin layer, the bump is configured. Among metals, copper, tin, or bismuth comes to function as a sintering aid. For example, the above-described heating becomes a liquid phase, and the bump becomes a metal sintered body containing a binder component such as a resin.

  As a result, as compared with the case where particles such as silver are contained in the bumps (heat-cured vias) constituting the multilayer wiring board as in the prior art, the bumps (vias) due to the reduction in the interface between the particles are reduced. Since the surface area is reduced, it is possible to suppress the problem that the conductor loss due to the skin effect is reduced during high-speed transmission and signal delay occurs.

  In the present embodiment, the bump 12 has a truncated cone shape, and its height h can be set in the range of 15 μm to 200 μm, for example, and the lower surface diameter R can be set in the range of 10 μm to 200 μm.

  Next, as shown in FIG. 2, a second metal foil 14 is disposed on the first metal foil 11 via an insulating resin layer 13 that does not contain a fibrous filler, and as shown in FIG. Using the device 17, the second metal foil 14 is pressed against the first metal foil 11 through the insulating resin layer 13 at the first temperature.

  The insulating resin layer 13 has a thickness t2 in the range of 10 μm to 40 μm, for example, and is fluidized by heating at the first temperature, and the insulating resin layer 13 remaining on the upper end portion 12A of the bump 12 is indicated by an arrow in the figure. As shown, the insulating resin layer 13 that flows from the upper end portion 12A of the bump 12 toward the side surface 12B needs to be removed (removed) from the upper end portion 12A of the bump 12 (see FIG. 4).

For this purpose, the upper limit of the melt viscosity at the first temperature of the insulating resin layer 13 is preferably 1 × 10 ⁵ Pa · s, and more preferably 1 × 10 ⁴ Pa · s. When the melt viscosity becomes larger than the above value, the insulating resin layer 13 cannot flow sufficiently, a relatively large amount of resin residue is present on the upper end portion 12A of the bump 12, and then pressed at the second temperature, When the resin is cured and the bump is sintered, the resin layer remains at the interface between the second metal foil 14 and the upper end portion 12A of the bump 12, and connection reliability may be impaired.

The lower limit of the melt viscosity at the first temperature of the insulating resin layer 13 is preferably 1 × 10 ¹ Pa · s, and more preferably 1 × 10 ² Pa · s. If the melt viscosity is smaller than the above value, it may be difficult to control the thickness of the insulating resin layer 13.

  In addition, the said melt viscosity is a value calculated | required from the minimum melt viscosity by performing a rheometer measurement by TA instrument company make (model number ARES-G2) using the test piece of 300 mm-500 mm □ and thickness 300 micrometers.

  In particular, when the size of the bump 12 is defined by the height h and the diameter R described above, and the thickness of the insulating resin layer 13 is defined by t2 described above, the remaining insulating resin layer 13 is removed from the bump 12. It can be surely excluded (removed) from the upper end 12A.

  In the present embodiment, the “upper end portion 12A of the bump 12” refers to a part of the second metal foil 14, that is, a bump region to be coupled to the wiring layer, and “the side surface 12B of the bump 12”. In the surface exposed on the surface of the bump 12, the region excluding the upper end portion 12A is indicated.

  Further, the insulating resin layer 13 is required not to contain a fibrous filler, and for example, a particulate or powdery filler such as silica or alumina may be included.

  Examples of the insulating resin constituting the insulating resin layer 13 include an epoxy resin, a phenol resin, a polyimide resin, a polysulfone resin, a polyester resin, and a polycarbonate resin.

  Moreover, when the insulating resin layer 13 is comprised from the above insulating resins, the said 1st temperature can be set to the range of 120 to 160 degreeC, for example.

  The second metal foil 14 is also composed of a good electrical conductor such as copper (Cu), gold (Au), silver (Ag) or aluminum (Al) because it will later constitute the wiring layer of the multilayer wiring board. Further, the thickness t3 of the second metal foil 14 is, for example, 1.5 μm to 40 μm.

  Next, as shown in FIG. 5, the second metal foil 14 is further applied to the first metal foil 11 by the press device 17 via the insulating resin layer 13, which is higher than the first temperature. The insulating resin layer 13 and the bumps 11 are cured at a temperature of 2 mm, and the second metal foil 14 is laminated on the insulating resin layer 13 (lamination press). Accordingly, the first metal foil 11 and the second metal foil 14 constitute a wiring layer, the insulating resin layer 13 constitutes an insulating member interposed between the wiring layers, and the bump 11 penetrates the insulating member, and the wiring layer A multilayer wiring board can be formed by constituting an interlayer connector (via) that electrically connects the two.

  The second temperature is higher than the first temperature and is a temperature at which the insulating resin layer 13 and the bumps 11 are cured, and can be set to a temperature range of 160 ° C. to 230 ° C., for example.

  In addition, the multilayer wiring board obtained as described above is a multilayer wiring board having two wiring layers. To increase the number of wiring layers, the above-described steps may be repeated.

  Specifically, as shown in FIG. 1, a conductive paste is applied by an arbitrary method such as a screen printing method, a dispensing method, or an ink jet method, with the wiring layer located at the uppermost layer as the first metal foil 11. After forming the bumps 12 made of the conductive paste, as shown in FIG. 2, the second metal foil 14 is arranged on the first metal foil 11 via the insulating resin layer 13 not containing a fibrous filler. As shown in FIG. 3, the second metal foil 14 is attached to the first metal foil 11 via the insulating resin layer 13 using the press device 17 such as a roll laminator or a vacuum laminator. As shown in FIG. 4, the insulating resin layer 13 is caused to flow from the upper end portion 12 </ b> A of the bump 12 toward the side surface 12 </ b> B, and the remaining insulating resin layer 13 is excluded (removed) from the upper end portion 12 </ b> A of the bump 12. To do.

  Next, as shown in FIG. 5, the second metal foil 14 is further pressed against the first metal foil 11 through the insulating resin layer 13 at a second temperature higher than the first temperature. The insulating resin layer 13 and the bumps 11 are cured, and the second metal foil 14 is laminated on the insulating resin layer 13 (lamination press).

  As described above, according to the manufacturing method of the present embodiment, as described above, after forming the bumps 12 made of the conductive paste on the first metal foil 11, the fibrous filler is applied to the first metal foil 11. The second metal foil 14 is pressed at the first temperature through the insulating resin layer 13 not included. At this time, since the viscosity of the insulating resin layer 13 decreases and fluidizes as the temperature rises, the insulating resin layer 13 remaining on the upper end portion 12A of the bump 12 is eliminated during pressing, and the upper end of the insulating resin layer 13 is removed. The part 12 </ b> A is exposed from the insulating resin layer 13.

  Therefore, when the second metal foil 14 is pressed against the first metal foil 11 again at a second temperature higher than the first temperature and the lamination press is performed later, the second metal foil 14 is insulated. The hardened bumps (vias) 12 exposed from the resin layer 13 are securely bonded to the upper end portions 12A of the bumps (vias) 12, whereby the first metal foil 11 and the second metal foil 14 that later become wiring layers are high. It becomes electrically connected with reliability. As a result, the electrical connection between the wiring layers can be sufficiently retained by the interlayer connector (via), and a multilayer wiring board having excellent reliability can be provided.

  Further, in this embodiment, the insulating member constituting the multilayer wiring board is constituted by the insulating resin layer 13 that does not contain the fibrous filler, and is heated and fluidized at the first temperature to form the upper end portion 12A of the bump 12. The remaining insulating resin layer 13 is excluded, and the upper end portion 12 </ b> A is exposed from the insulating resin layer 13. Therefore, unlike the prior art, when the insulating resin layer 13 is press-formed on the first metal foil 11, the step of penetrating the bumps 12 into the insulating resin layer 13 can be omitted.

  Moreover, in this embodiment, since the insulating member which comprises a multilayer wiring board is comprised from the insulating resin layer 13 which does not contain a fibrous filler, the thickness of an insulating member can be narrowed. Therefore, miniaturization and high density of the multilayer wiring board can be achieved.

(Second Embodiment)
6 and 7 are process diagrams for explaining the method of manufacturing the multilayer wiring board according to the present embodiment, and correspond to the process shown in FIG. 1 in the first embodiment.

  In the first embodiment, the bumps 12 are formed in a truncated cone shape on the first metal foil 11, but the present embodiment is different in that the bumps 22 are formed in a cone shape. Accordingly, in the steps shown in FIGS. 2 to 4 in the first embodiment, when the insulating resin layer 13 is heated and fluidized at the first temperature, the insulating resin is transferred from the upper end portion 22A of the bump 22 to the side surface 22B. Since the layer 13 becomes easier to flow, the insulating resin layer 13 remaining on the upper end 22A can be more effectively removed and removed.

  As a result, when the second metal foil 14 is pressed against the first metal foil 11 again at a second temperature higher than the first temperature later to perform the lamination press, the second metal foil 14 is The hardened bumps (vias) 12 exposed from the insulating resin layer 13 are more securely bonded to the upper end portions 12A of the bumps (vias) 12, and thereby, the first metal foil 11 and the second metal foil 14 that later become wiring layers. Are electrically connected with higher reliability. For this reason, the electrical connection between the wiring layers can be more sufficiently maintained by the interlayer connection body (via), and a multilayer wiring board with higher reliability can be provided.

  The height of the bump 22 and the diameter of the bottom surface can be defined in the same manner as the height h and the diameter R of the bump 11 in the first embodiment.

  Since other features and advantages are the same as those in the first embodiment, description thereof will be omitted.

  The present invention has been described in detail based on the above specific examples. However, the present invention is not limited to the above specific examples, and various modifications and changes can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, a case where a multilayer wiring board is manufactured by forming bumps or the like on a metal foil has been described. However, a core board (both sides or multilayer) is prepared in advance, and the above-described core board is described above. A multilayer wiring board can also be laminated | stacked according to a process. In this case, the wiring layer located at the uppermost layer is regarded as the first metal foil 11 and, for example, a process as described in the first embodiment is performed.

DESCRIPTION OF SYMBOLS 11 1st metal foil 12, 22 Bump 12A, 22A Bump upper end part 12B, 22B Bump side surface 13 Insulating resin layer 14 2nd metal foil 17 Vacuum press apparatus

Claims (5)

Applying a conductive paste on the first metal foil and forming a bump made of the conductive paste;
The second metal foil is pressed against the first metal foil through an insulating resin layer that does not contain a fibrous filler at a first temperature to fluidize the insulating resin layer, and the upper end of the bump Removing the insulating resin layer remaining in the part;
The second metal foil is pressed against the first metal foil via the insulating resin layer at a second temperature higher than the first temperature, and the insulating resin layer and the bump are Curing, and laminating the second metal foil on the insulating resin layer;
A method for manufacturing a multilayer wiring board, comprising: 2. The method for manufacturing a multilayer wiring board according to claim 1, wherein a melt viscosity of the insulating resin layer at the first temperature is 1 × 10 ⁵ Pa · s or less. The method for producing a multilayer wiring board according to claim 2, wherein the insulating resin layer has a melt viscosity of 1 × 10 ¹ Pa · s or more at the first temperature.   The method for manufacturing a multilayer wiring board according to claim 1, wherein the bump is made of a conductive paste containing at least Sn, Bi, Cu, and Ag.   The method for manufacturing a multilayer wiring board according to claim 1, wherein the bump has a conical shape.

Images