JP2010028028A - Multilayer printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer printed wiring board in which a conductor pattern layer is connected surely, a connecting part is low in electrical resistance and the surface of the connecting part is formed flat, and to provide its manufacturing method. <P>SOLUTION: The multilayer printed wiring board is provided with a plurality of conductor pattern layers 24 made of copper foil or the like with an insulating base material 22 made of a resin therebetween, and an interlayer connection part 38 such as a via hole or the like for conducting the conductor pattern layers 24 with each other. A counterbored part 30 made small in thickness is formed at the connecting part 26 of copper foil or the like of the conductor pattern layer 24 connected to the interlayer connecting part 38. The counterbored part 30 is filled with a conductor such as a metallic filler or the like, which is put into the interlayer connecting part 38. The counterbored part 30 is formed by half etching. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a multilayer printed wiring board provided with a plurality of conductor pattern layers including a double-sided printed wiring board, and includes a multilayer printed wiring board provided with an interlayer connection structure such as a via hole for conducting between the conductive pattern layers. It relates to the manufacturing method.

  Conventionally, as a structure for conducting conduction between each conductive pattern layer of a multilayer printed wiring board, via holes are formed in the base material of the insulating layer by a drill or a laser, and copper plating is applied to the inner surface thereof to achieve conduction between the respective layers. It was.

  In recent years, in order to conduct electricity between a plurality of conductive pattern layers of a multilayer printed wiring board including a double-sided printed wiring board, there is one in which a via hole is filled with a conductive paste. Such a method for manufacturing a multilayer printed wiring board is manufactured, for example, by steps shown in steps S1 to S8 in the flowchart of FIG. First, a through hole is provided in a prepreg constituting an insulating base material such as an aramid epoxy sheet for forming an insulating layer by a hole forming means such as drilling or laser processing (S1). A protective film is affixed to both sides of the prepreg, and through holes are formed together with the protective film. Then, a masking film is stuck on the B surface which is the back surface of the prepreg of the substrate (S2), and smears such as wrinkles in the through holes are removed (S3). Then, the conductive paste is filled into the through hole from the surface side by a filling means such as a squeegee operation through the through hole (S4). The conductive paste is obtained by dispersing metal particles such as Ag and Cu in a thermosetting resin such as an epoxy resin. Next, the protective film and the masking film are peeled off (S5), and copper foil is laminated on both sides of the prepreg, and is hot-pressed and fixed (S6). Then, patterning of the copper foil is performed with a predetermined mask to form a circuit (S7), and the process proceeds to the next multilayering process (S8).

  By this manufacturing process, a multilayer printed wiring board is formed in which conduction between the conductive patterns of the respective layers is achieved via a conductive paste.

  In addition, as shown in Patent Document 1 and FIG. 5, there is a type in which a multilayer printed wiring board is formed by filling a via hole with a thermosetting resin using a double-sided copper-clad board. In this multilayer printed wiring board manufacturing method, first, as shown in FIG. 5 (b), a drill is applied to an insulating base material 1 having copper foils 2 attached on both sides as shown in FIG. 5 (a). The through hole 4 is provided by hole forming means such as processing or laser processing. Next, as shown in FIG. 5C, a metal or resin mask 6 having a through hole 3 corresponding to the through hole 4 is brought into close contact with the base material 1, and as shown in FIG. Then, the conductive paste 5 is filled into the through hole 4 by filling means such as a squeegee operation through the through hole 3 of the mask 6. The hole diameter of the surface of the through hole 3 of the mask 6 in contact with the base material 1 is set slightly smaller than the hole diameter of the through hole 4 of the base material 1. At this time, the thickness of the mask 6 and the filling condition of the conductive paste 5 are set so that the amount of the conductive paste 5 is larger than the volume of the through hole 4.

Next, as shown in FIG. 5E, the mask 6 is removed. Thereafter, as shown in FIG. 5 (f), heating (not shown) is performed in a state where the heat-resistant film 7 having elasticity such as polyimide, polyphenylene sulfide, or polyether ether ketone is placed on the upper and lower surfaces of the base material 1. Using a press device or the like, heating and pressurization is performed at 160 to 200 ° C. under a condition of 20 to 60 kg / cm ² for 30 to 180 minutes. Thereby, the conductive paste 5 is pressed into the through-hole 4 and cured, and the copper foil 2 provided on both surfaces of the substrate 1 and the conductive paste 5 are reliably electrically connected. At this time, the conductive paste 5 corresponding to the thickness of the mask 6 is excessively filled, so that the conductive paste 5 is reliably filled into the through-holes 4 by the heating press, and the resistance value is stabilized. . Thereafter, the heat resistant film 7 is removed, and the outer layer copper foil 2 is formed on the predetermined conductor pattern 8 by etching or the like. Then, as shown in FIG. 5G, a double-sided printed wiring board 10 in which the conductive patterns 8 on both sides are electrically connected by via holes 9 is formed.

In addition, as a conductive material filled in the via hole, a material having a lower electrical resistance and a metal conductor present in the via hole by metal bonding has been proposed. The manufacturing method of the multilayer printed wiring board using such an electrically conductive paste is manufactured by the process as shown to step S1-S8 of the flowchart of FIG. First, using a double-sided copper-clad plate, a masking film is affixed to surface A, which is the surface (S1), and a through hole is formed at a predetermined position of the insulating base material by laser processing, drilling, or the like (S2). . Thereafter, smear due to processing is removed (S3), and the conductive paste is filled into the through-holes via the masking film (S4). The conductive paste to be filled here is one in which metal particles such as a low melting point metal are mixed in a thermoplastic resin as disclosed in Patent Document 2 and alloyed in the through-hole by a subsequent heat treatment. is there. Thereafter, the masking film is peeled off (S5), heated in a vacuum to a temperature of about 180 to 300 ° C., and pressed to alloy and harden the conductive paste in the through hole (S6). Thereafter, predetermined patterning is performed on the copper foil on the surface of the base material of the insulating layer to form a circuit pattern (S7), and the process proceeds to the next multilayering process (S8).
Japanese Patent Laid-Open No. 9-232059 JP 2006-165508 A

  However, the interlayer connection structure in which the inner surface of the via hole is plated is difficult to manage the plating solution for stabilizing the quality. In addition, the apparatus has become large in size and cannot cope with the details, and costs have been increased.

  In the case of a multilayer printed wiring board having an interlayer connection structure using a conductive paste using a thermosetting resin as shown in FIGS. 4 and 5 and Patent Document 1, the cost of the conductive paste containing Ag and Cu fine particles is high. Moreover, since each metal particle is only in physical contact and conduction, the electrical resistance of the via hole is relatively large.

  Furthermore, the structure of the via hole formed by the manufacturing method shown in FIG. 6 is such that, as shown in FIG. 7, a double-sided copper-clad plate in which copper foil 2 is attached to both sides of an insulating base material 1 is interposed via a mask 16. Since the through-hole 14 is filled with the conductive paste 15, the volume of the conductive paste 15 is larger than the volume of the through-hole 14 of the substrate 1 by the space of the mask hole 16 a. In this state, when heated and pressed, the excess conductive paste 15a spreads around the connection portion 2a of the copper foil 2 and rises above the surface of the connection portion 2a. This impairs the flatness of the multilayer printed wiring board and hinders the increase in the number of layers.

  The present invention has been made in view of the above-mentioned background art, and is a multilayer printed wiring board in which the connection with the conductor pattern layer is reliable, the electric resistance of the connection portion is small, and the surface of the connection portion is formed flat. An object is to provide a manufacturing method.

  The present invention includes a conductive pattern layer such as a plurality of layers of copper foil provided between resin-made insulating bases, and an interlayer connection portion such as a via hole for conducting between the conductive pattern layers. A multilayer printed wiring board in which a countersink portion with a reduced thickness is formed in a connection part such as a copper foil of the conductor pattern layer connected to the connection part, and a conductor of the interlayer connection part is in contact with the countersink part is there.

  The counterbored portion is filled with a conductor such as a metal filler filled in the interlayer connection portion.

  Further, according to the present invention, a conductive pattern layer such as a plurality of layers of copper foil is formed with a resin insulating base material sandwiched therebetween, and through holes connecting between the conductive pattern layers are formed in the base material. A method of manufacturing a multilayer printed wiring board in which a conductor connecting portion is formed by filling a metal filler or the like for connecting the conductor pattern layer, wherein the thickness of the connecting portion of each conductor pattern layer is partially reduced It is a manufacturing method of the multilayer printed wiring board which forms the conductor connection part connected to the said countersink part after forming a repeat part.

  The counterbored portion is formed by half etching in which the thickness of the connecting portion is partially reduced by chemical etching with an etching solution or physical etching with plasma or laser.

  The conductor connection portion is formed by filling the through hole with a conductive paste larger than the volume of the through hole, pressurizing the conductive paste, and storing the conductive paste in the countersunk portion. To do.

  The conductive paste contains metal particles in a thermoplastic resin binder, melts by pressurizing and heating the conductive paste, and after cooling, the through hole is filled with a filler of a metal material. Thus, a conductor connecting portion is formed.

  According to the multilayer printed wiring board and the manufacturing method thereof of the present invention, the connection between the conductor pattern layer and the conductor connection portion is reliable, the electrical resistance of the connection portion is small, and the surface of the conductor connection portion is the same as that of the conductor pattern layer. It is formed on a flat surface. Furthermore, the connection strength between the conductor pattern layer and the conductor connection portion is high, and a highly reliable multilayer printed wiring board can be formed.

  Hereinafter, an embodiment of a multilayer printed wiring board according to the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 3, the multilayer printed wiring board 20 of this embodiment has a plurality of conductor pattern layers 24 sandwiched between insulating base materials 22, and between the conductor pattern layers 24. A through hole 23 is formed, and an interlayer connection 38 made of a metal filler or the like is provided.

  The base material 22 of the insulating layer is made of an insulating base material that constitutes a printed wiring board made of glass epoxy, polyimide, paper phenol, or the like, and has a copper foil 25 attached to both surfaces. In addition, the base material 22 may be a thermoplastic resin having heat resistance in a soldering process or the like and sufficient mechanical strength. For example, a liquid crystal polymer of a wholly aromatic polyester resin can be used.

  The copper foil 25 is provided with a conductor pattern layer 24 formed in a predetermined circuit pattern, and the conductor pattern layer 24 includes a circuit pattern and a connecting portion 26 subsequent thereto. The through hole 23 penetrating the base material 22 is not penetrated into the connection portion 26 of the conductor pattern layer 24 on the back surface, and is connected to the copper foil 25 of the connection portion 26 on the back surface side. Moreover, the connection part 26 is formed also in the conductor pattern layer 24 of the surface side, and conduction | electrical_connection between the conductor pattern layers 24 of the front and back of the base material 22 is aimed at.

  In the connection part 26 of the conductor pattern layer 24 on the surface side, a countersink part 30 is formed in communication with the through hole 23 by removing up to about half of the thickness of the copper foil 25 by chemical etching or the like.

  Next, the manufacturing method of the multilayer printed wiring board of this embodiment is demonstrated based on process drawing of FIG. 1, and step S1-S9 of the flowchart of FIG.

  First, as shown in FIG. 1A, using a double-sided copper-clad plate 21, a dry film 32 of an etching resist is pasted on both sides (S1). The dry film 32 is exposed to a predetermined pattern, and is provided so that an opening 32a is formed at a location where the counterbore 30 formed by half etching is formed. In this state, as shown in FIG. 1 (b), a predetermined position of the copper foil 25 on the surface side of the double-sided copper-clad plate 21 is etched, and at the place where the opening 32a of the dry film 32 is formed, A portion where the counterbore 30 is formed is half-etched (S2). In the half etching, the etching time with an etching solution such as sulfuric acid / hydrogen peroxide is adjusted so that the countersink portion 30 is formed concentrically inside the portion where the connection portion 26 of the conductor pattern layer 24 is formed, and the copper foil 25 Etching is stopped in a state where about 1/2 of the thickness of the film is dissolved. Further, the countersunk portion 30 may be formed by plasma irradiation or physical etching with a laser.

  Next, as shown in FIG.1 (c), the masking film 34 is stuck on the A surface which is the surface side of the double-sided copper-clad board 21 (S3). And the through-hole 23 as shown in FIG.1 (d) is formed by laser processing using a carbon dioxide laser, a YAG laser, an excimer laser, etc. (S4). Thereafter, the smear due to the processing is removed, and the conductive paste 36 is filled into the through hole 23 through the masking film 34 by filling means such as a squeegee operation (S5). The countersink part 30 in which the thickness of the copper foil 25 is formed is filled with a conductive paste 36 filled in the through-hole 23 partially in a bowl shape on the side by pressure.

  The conductive paste filled here is, for example, disclosed in Patent Document 2, in which metal particles of a high melting point metal and a low melting point metal are mixed in a thermoplastic resin and alloyed by a subsequent heat treatment. is there. For example, the refractory metal includes at least copper, and is a particle of copper alone or an alloy particle including copper and one or more metals of gold, silver, zinc, and nickel. The surfaces of these metal particles may be coated with gold, silver, zinc, nickel, or an alloy thereof by plating or the like. The average particle diameter of these metal particles is 6 to 10 μm, for example 8 μm. The low melting point metal is Sn or an alloy (for example, solder) particles containing Sn. As the solder, Sn-Cu solder, Sn-Ag solder, Sn-Ag-Cu solder, any one or more of In, Zn, and Bi may be added to these solders, and further mixed as appropriate. . The binder resin of the conductive paste 36 is a thermoplastic resin. For example, thermoplastic resins such as polyester, polyolefin, polyacryl, polyamide, polyamideimide, polyetherimide, polyphenylene ether, polyphenylene sulfide, and polyvinyl butyral can be used.

After filling with the conductive paste 36, as shown in FIG. 1E, the dry film 32 and the masking film 34 are removed (S6). Then, the conductive paste 36 is sandwiched between metal plates through a heat-resistant film such as polyimide, polyphenylene sulfide or polyether ether ketone (not shown), and heated in a vacuum of about 180 to 300 ° C., for example. It heats and pressurizes for 30 to 180 minutes under the condition of 20 to 60 kg / cm ² to alloy and harden the conductive paste in the through hole 23 (S7). The heating temperature is, for example, not less than the melting point of the low melting point metal in the conductive paste, and not less than the temperature at which the base material 22 does not change and the binder resin melts.

  In this state, as shown in FIG. 1F, the conductive paste 36 becomes a columnar interlayer connection portion 38 made of a filler made of a metal material. At this time, the conductive paste 36 in excess of the volume of the through hole 23 is deformed by the pressure by the press and is pushed to the side, and spreads in the space of the countersink 30. Then, the conductive paste 36 is formed on the same plane as the surface of the connection portion 26. Thereafter, predetermined patterning is performed on the copper foil on the surface of the base material of the insulating layer to form a circuit pattern (S8), and the process proceeds to the next multilayering process (S9).

  According to the multilayer printed wiring board of this embodiment, the surface of the interlayer connection portion 38 formed in the through hole 23 is formed on a flat surface, and there is no swell due to the metal filler of the excess conductive paste 36. Even in this case, the flatness of the multilayer printed wiring board 20 can be maintained. Further, the connection with the connection portion 26 is a stepped portion of the countersunk portion 30, the contact area with the conductive paste 36 is increased, and the electrical connection between the conductive paste 36 and the connection portion 26 is ensured. Therefore, the resistance value is low and the electrical reliability can be high. Furthermore, since the counterbore 30 is formed, the formation of the through hole 23 is facilitated, and the processing time and output of a laser or the like can be suppressed.

  The multilayer printed wiring board and the manufacturing method thereof according to the present invention are not limited to the above embodiment, and may be a printed wiring board other than the double-sided printed wiring board, and may be a multilayer printed circuit having three or more conductive pattern layers. A wiring board may be used. The metal material in the conductive paste can be selected as appropriate, and the metal material may be provided with metal particles in a thermosetting resin, and Sn-Ag or other low melting point metal is plated on the non-metallic fine particles. A thing provided in a thermoplastic resin may be used.

It is a schematic longitudinal cross-sectional view which shows the manufacturing process of the multilayer printed wiring board of one Embodiment of this invention. It is a flowchart which shows the manufacturing process of the multilayer printed wiring board of one Embodiment of this invention. It is a longitudinal cross-sectional view of the interlayer connection part of the multilayer printed wiring board of one Embodiment of this invention. It is a flowchart which shows the manufacturing process of the conventional multilayer printed wiring board. It is a longitudinal cross-sectional view which shows the manufacturing process of the conventional multilayer printed wiring board. It is a flowchart which shows the manufacturing process of the conventional multilayer printed wiring board. It is a longitudinal cross-sectional view which shows the interlayer connection part of the conventional multilayer printed wiring board.

Explanation of symbols

20 multilayer printed wiring board 21 double-sided copper-clad board 22 base material 24 conductor pattern layer 23 through-hole 25 copper foil 26 connection part 30 countersink part 36 conductive paste 38 interlayer connection part

Claims (6)

  Provided with a plurality of conductor pattern layers provided across an insulating base material, and an interlayer connection portion for conducting electrical conduction between the respective conductor pattern layers, the connection portion of the conductor pattern layer connected to the interlayer connection portion The multilayer printed wiring board is characterized in that a countersink portion having a reduced thickness is formed, and a conductor of the interlayer connection portion is in contact with the countersink portion.   2. The multilayer printed wiring board according to claim 1, wherein the counterbored portion is filled with a conductor filled in the interlayer connection portion.   A plurality of conductive pattern layers are formed with an insulating base material interposed therebetween, and through holes connecting between the conductive pattern layers are formed in the base material, and a conductor connection portion for connecting the conductive pattern layers to the through holes is provided. In the manufacturing method of the multilayer printed wiring board to be formed, after forming the countersunk part in which the thickness of the connection part of each conductor pattern layer is partially reduced, forming the conductor connection part connected to the countersink part A method for producing a multilayer printed wiring board, which is characterized.   4. The method of manufacturing a multilayer printed wiring board according to claim 3, wherein the countersink portion is formed by half etching.   The conductive connection portion is formed by filling the through hole with a conductive paste larger than the volume of the through hole, pressurizing the conductive paste, and storing the conductive paste in the countersink portion. The method for producing a multilayer printed wiring board according to claim 3. The conductive paste contains metal particles in a thermoplastic resin binder, melts by pressurizing and heating the conductive paste, and after cooling, the through hole is filled with a filler of a metal material. 4. The method of manufacturing a multilayer printed wiring board according to claim 3, wherein a conductor connecting portion is formed.

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