JP2005123400A - Circuit board and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board which does not require any plated metal for covering a through hole filled up with an insulating resin and on which a minute circuit can be formed, and to provide a method of manufacturing the circuit board. <P>SOLUTION: The circuit board comprises an internal board provided with a plated through hole having an inside diameter of ΦI, an internal conductor layer provided in the opening of the through hole of the internal board and having a diameter of ΦL, and an insulating resin layer formed on the surface of the internal conductor layer. The circuit board also comprises a non-through hole which is formed in the insulating resin layer to reach the internal conductor layer immediately above the through hole formed in the internal board and has an opened diameter of ΦO. This circuit board has one or more connecting hole structures in which the through hole having the inside diameter of ΦI, the internal conductor layer having the diameter of ΦL, and the non-through hole having the opened diameter of ΦO are formed by adjusting a relation among the diameters ΦI, ΦL, and ΦO to ΦI<ΦO<ΦL. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a circuit board and a method for manufacturing the circuit board.

  With the recent progress in downsizing and high functionality of electronic devices, development of build-up circuit boards corresponding to thinning and high density wiring is required. Since the build-up circuit board can be connected only with the circuit layer that requires interlayer connection with a non-through hole, only the through hole of the inner layer plate and the hole that penetrates the entire circuit board are not necessarily required. It is suitable for thinning and miniaturization of substrates, and has been developed in recent years.

In the build-up circuit board, when the build-up layer is formed on the inner layer plate having the through hole, the non-through hole is often formed immediately above the through hole from the viewpoint of increasing the efficiency of wiring and increasing the density. It has become. In a build-up circuit board having three or more conductor layers, when the non-through hole of the outer layer is formed immediately above the through hole of the inner layer board, the through hole of the inner layer board subjected to electroless or electrolytic metal plating is made of a conductive material. After filling the through hole with a conductive material or insulating resin, it is necessary to perform metal plating so as to cover the through hole (for example, see Patent Document 1).
JP 2003-133727 A

  When filling the through hole of the inner layer plate of the build-up circuit board with the conductive material 9, it is not always necessary to perform metal plating so as to cover the through hole (see FIG. 2B). However, since the conductive material contains conductive particles, it has a very high viscosity in a paste state as compared with the insulating resin, and it is difficult to fill a small diameter through hole or a high aspect ratio through hole. In addition, even when the through hole can be filled with a conductive material, the conductive material is in a cured state and the hardness is larger than that of the insulating resin. It is difficult to completely remove the copper layer on the surface of the inner layer plate because it may be deeply scraped off. In addition, when there is a polishing residue, it may cause defective circuit formation.

  When the non-through hole is formed immediately above the through hole, when the through hole of the inner layer plate of the build-up circuit board is filled with the insulating resin 8, metal plating is performed so as to cover the through hole, ensuring connection reliability. It is necessary from the point of. In particular, it is essential when the diameter of the through hole is larger than the diameter of the non-through hole formed immediately above (see FIG. 2A). In general, the thickness of the inner conductor layer is disadvantageous for forming a fine circuit because the base copper layer, the copper plating of the through hole, and the copper plating covering the through hole overlap.

  The present invention provides a circuit board that eliminates the need for metal plating that covers a through-hole filled with an insulating resin and enables formation of a fine circuit, and a method for manufacturing the circuit board.

The present invention is characterized by the following.
(1) A plated inner wall plate having a through hole with an inner wall diameter of ΦI, an inner layer conductor layer with a diameter of ΦL provided in an opening of the through hole of the inner layer plate, and insulation formed on the surface of the inner layer conductor layer In a circuit board having a resin layer and a non-through hole reaching an inner layer conductor layer having an opening diameter ΦO located immediately above the through hole formed in the insulating resin layer, a through hole having an inner wall diameter ΦI and an inner layer having a diameter ΦL A circuit board having at least one connection hole structure in which a conductor layer and a non-through hole having an opening diameter of ΦO have a relationship of ΦI <ΦO <ΦL.
(2) The circuit board according to (1), wherein the plated inner wall diameter ΦI is Φ0.001 to 0.09 mm.
(3) The circuit board according to (1) or (2), wherein the inner conductor layer has a thickness of 1 μm to 20 μm.
(4) preparing a plated inner wall plate having a through hole with an inner wall diameter ΦI, forming a conductor layer with a diameter ΦL larger than the diameter ΦI at the opening of the through hole of the inner layer plate, a conductor layer with ΦL Forming an insulating resin layer on the surface of the conductor layer containing at least one non-through hole in the insulating resin layer that reaches the inner conductor layer having an opening diameter ΦO larger than the diameter ΦI and smaller than the diameter ΦL immediately above the through hole. A method of manufacturing a circuit board including the steps of forming as described above.
(5) The method for manufacturing a circuit board according to (4), wherein the step of forming the insulating resin layer on the surface of the conductor layer including the conductor layer of ΦL includes a step of filling the through hole with the insulating resin.

  According to the present invention, it is possible to provide a circuit board corresponding to fine circuit formation and a manufacturing method thereof. Since the non-through hole with the opening diameter ΦO has a relationship of ΦI <ΦO <ΦL, even if the non-through hole is formed immediately above the through hole, the through hole filled with the insulating resin is covered. Metal plating is not required, whereby the thickness of the inner conductor layer can be reduced to 20 μm or less, and therefore, fine wiring with a line / space = 40/40 μm level or less can be efficiently formed in the inner conductor layer.

  In the circuit board shown in the present invention, the through-hole 2 having the inner wall diameter ΦI5 formed in the inner layer plate 18, the inner-layer conductor layer 1 having the diameter ΦL6, and the non-through hole 14 having the opening diameter ΦO4 formed in the insulating resin layer 7 are provided. Have one or more connection hole structures having a relationship of ΦI <ΦO <ΦL (see FIG. 1A). The through hole 2 having an inner wall diameter ΦI 5 of the present invention is provided in the inner layer plate 18, and the through hole 2 is normally filled with an insulating resin 7. Since the non-through hole 14 having the opening diameter ΦO4 has a relationship of ΦI <ΦO <ΦL, even if the non-through hole 14 is formed immediately above the through hole 2, the through hole filled with the insulating resin 7 is used. No metal plating covering 2 is required. If the non-through hole 14 having the opening diameter ΦO4 is smaller than the through hole 2 having the inner wall diameter ΦI5, in order to form the non-through hole immediately above the through hole 2, the through hole necessarily filled with the insulating resin 7 is used. Metal plating covering the metal layer is required, the inner conductor layer becomes thick, and the formation of fine wiring is disadvantageous. Further, since the inner conductor layer 1 having the diameter ΦL6 is larger than the non-through hole 14 having the opening diameter ΦO4, it is possible to secure a sufficient connection area. On the other hand, when the inner conductor layer 1 having the diameter ΦL6 is smaller than the non-through hole 14 having the opening diameter ΦO4, a sufficient connection area cannot be secured, and a position shift occurs when the non-through hole 14 is drilled. In some cases, connection failure may occur.

  The diameters of the through hole, the inner layer conductor layer, and the non-through hole only have to have a relationship of ΦI <ΦO <ΦL, and as long as the relationship is maintained, the through hole and the inner layer conductor The range of each diameter of the layer and the non-through hole is not particularly limited. However, from the viewpoint of alignment at the time of circuit formation or non-through hole formation, thinning of the circuit board and high density of wiring, the opening diameter ΦO of the non-through hole is larger than the inner wall diameter ΦI of the through hole, It is preferable that the diameter ΦL of the inner conductor layer is larger by Φ0.05-0.20 mm than the opening diameter ΦO of the non-through hole. Thereby, a sufficient connection area can be ensured between the inner conductor layer and the non-through hole, and a circuit board with high connection reliability can be obtained.

  In the circuit board shown in the present invention, the inner wall diameter ΦI of the plated through hole is preferably Φ0.001 to 0.09 mm, more preferably Φ0.01 to 0.04 mm. When the diameter is less than 0.001 mm, it is difficult to make a through hole, and it is difficult to perform plating because the inside of the through hole is not sufficiently immersed in the plating solution. Further, in order to make the inner wall diameter of the through hole less than Φ0.001 mm, it is necessary to apply a thick plating, and it becomes difficult to form fine wiring of the inner conductor layer. If it exceeds Φ0.09 mm, the diameter of the inner conductor layer and the opening diameter of the non-through hole are inevitably increased, which is disadvantageous in reducing the thickness of the circuit board and high-density wiring. The thickness of the substrate having the inner conductor layer formed with plated through holes is preferably 0.01 to 0.30 mm, more preferably 0.03 to 0.1 mm, from the viewpoint of through hole drilling and plating. preferable.

  The diameter ΦL of the inner conductor layer provided in the opening of the through hole is preferably Φ0.11 mm to 0.65 mm, more preferably Φ0.2 mm to 0.50 mm, and further preferably Φ0.25 mm to 0.35 mm. If the through hole having a diameter of 0.09 mm is formed with a diameter of less than Φ0.11 mm, the tolerance is less than 0.01 mm on one side, and alignment during circuit formation is difficult. This is disadvantageous in making the substrate thinner and performing high-density wiring.

  The opening diameter ΦO of the non-through hole located immediately above the through hole is preferably Φ0.08 to 0.25 mm, and particularly preferably Φ0.08 to 0.15 mm, from the viewpoint of insulating resin removability. If it exceeds Φ0.25 mm, it is disadvantageous in reducing the thickness of the circuit board and performing high-density wiring. Note that the non-through hole may be formed across a plurality of insulating resin layers (see FIG. 1B).

  In the circuit board shown in the present invention, the thickness of the inner conductor layer is preferably 1 to 20 μm, more preferably 5 to 15 μm. When the inner layer conductor layer is formed by the subtractive method when the thickness exceeds 20 μm, it becomes difficult to form fine wiring by side etching, and when the inner layer conductor layer is formed by the additive method or the like, a part of the plating resist is covered. Since plating is deposited, it is still difficult to form fine wiring.

  In the method of manufacturing a circuit board shown in the present invention, in the step of preparing a plated inner wall plate having a through hole having an inner wall diameter ΦI, the drilling of the through hole is performed by drilling, carbon dioxide laser, UV laser, excimer laser. However, drilling is preferred. Further, examples of the plating after drilling include copper, tin, solder, nickel, gold and the like. From the viewpoint of economy and workability, copper plating is preferable, and electrolytic copper plating is more preferable. The thickness of the inner layer plate is preferably from 0.01 to 0.30 mm, more preferably from 0.03 to 0.1 mm, from the viewpoint of through-hole drilling and plating.

  In the step of forming an inner layer conductor layer having a diameter ΦL larger than the inner wall diameter ΦI at the opening of the through hole of the inner layer plate, the inner layer conductor layer having a diameter ΦL is formed simultaneously with other conductor layers of the inner layer plate. The conductor layer may be formed using a subtractive method or an additive method. Further, the thickness of the formed conductor layer is preferably 20 μm or less, and more preferably 15 μm or less. In order to form a conductor layer having a thickness of 20 μm or less, it is preferable to use a base copper foil having a thickness of 5 μm or less for the inner layer plate and further perform copper plating of 15 μm or less.

  In the step of forming the insulating resin layer on the surface of the conductor layer of the inner layer plate, the insulating resin is preferably a thermosetting resin or thermoplastic. Examples of the thermosetting resin include, but are not limited to, a phenol resin, an epoxy resin, a polyimide resin, a cyanate resin, a maleimide resin, an isocyanate resin, a benzocyclobutene resin, and a vinyl resin. One type of thermosetting resin may be used alone, or two or more types may be mixed and used. Examples of the thermoplastic resin include fluorine resin, polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polycarbonate, polyether imide, polyether ether ketone, polyarylate, polyamide, polyamide imide, polybutadiene, and polyimide. It is not limited. One type of thermoplastic resin may be used alone, or two or more types may be mixed and used. Moreover, the inorganic filler may be included.

  When forming an insulating resin layer, a commercially available prepreg, resin varnish, resin film, or the like can be used. Examples of commercially available prepregs include GEA-679FZPE (trade name, manufactured by Hitachi Chemical Co., Ltd.). When forming an insulating resin layer on the surface of the conductor layer of the inner layer plate by pressing or the like through a prepreg between the copper foil and the inner layer plate, the plated through holes are filled simultaneously with an insulating resin such as a prepreg. It is preferable to do. In addition to the press, a resin varnish may be applied to the inner layer plate, similarly, an insulating resin layer may be formed on the surface of the conductor layer, and the through holes may be filled with the insulating resin.

  In addition, the plated through holes may be filled with insulating resin for filling holes in advance. Commercially available products can be used as the insulating resin for filling holes. In this case, before forming the conductor layer on the inner layer plate, after plating the through holes, the inner layer plate is filled with an insulating resin for filling holes. Thereafter, a circuit conductor layer is formed, and an insulating resin layer is formed on the surface.

  The inside of the through hole of the inner layer plate plated in the present invention is preferably filled with 50% or more of the volume of the through hole by the insulating resin, more preferably 80% or more of the volume of the hole, It is particularly preferred that 100% of the pore volume is filled.

  In the method for manufacturing a circuit board according to the present invention, in the step of forming at least one non-through hole having an opening diameter ΦO larger than the inner wall diameter ΦI and smaller than the diameter ΦL directly above the through hole in the insulating resin layer, The non-through holes formed in the insulating resin layer can be formed by a carbon dioxide laser, UV laser, excimer laser, or the like, but a carbon dioxide laser is preferable. When copper foil exists on the surface of the insulating resin layer, a conformal mask may be formed on the copper foil and laser drilling may be performed. Further, if the existing copper foil is 5 μm or less in thickness, laser drilling can be performed directly without forming a conformal mask. Even if the insulating resin filled in the through hole becomes slightly concave from the surface of the inner conductor layer due to laser drilling or the remaining removal process of the drilling resin, there is a particular problem such as connection reliability of the circuit board. There is no.

  In the present invention, the non-through hole with the opening diameter ΦO located immediately above the through hole of the inner layer plate only needs to have a relationship of ΦI <ΦO <ΦL, and as long as the relationship is maintained, the non-through hole The range of the diameter is not particularly limited. Further, it may be formed over a plurality of insulating resin layers (see FIG. 1B). In addition, from the viewpoint of thinning the circuit board and high-density wiring, the inner wall diameter ΦI of the plated through hole is preferably Φ0.001 to 0.09 mm, and more preferably Φ0.01 to 0.04 mm. Further, the opening diameter ΦO of the non-through hole is preferably Φ0.08 to 0.25 mm, and particularly preferably Φ0.08 to 0.15 mm.

  Hereinafter, the present invention will be described with reference to examples (see FIG. 3). The present invention is not limited to the following examples.

  Insulating resin layer laminated with 3 μm thick copper foil Glass cloth base epoxy resin copper clad laminate MCL-E-679F (trade name, manufactured by Hitachi Chemical Co., Ltd.) with nominal thickness of 0.06 mm A through hole of Φ0.05 mm was formed, and 10 μm electrolytic copper plating was applied to form a plated conductor layer, thereby forming a 0.03 mm through hole 2 having an inner wall diameter ΦI5. Furthermore, dry film NIT215 (product name, manufactured by Nichigo-Morton Co., Ltd.) for etching resist is temporarily pressure-bonded with a laminator, a negative mask is laminated, exposed to ultraviolet rays, the circuit is printed on both sides, and developed with a 1% aqueous sodium carbonate solution. Then, the etching resist is formed, the copper portion without the etching resist is removed with a ferric chloride aqueous solution, and the etching resist is peeled and removed with a 3% aqueous sodium hydroxide solution, and lines / spaces = 40/40 μm wiring on both sides. (Conductive layer) was formed to form the first circuit board 10 to be the inner layer plate 18. At that time, a 0.30 mm land (inner conductor layer) 1 of ΦL6 was formed in the through hole 2 (FIG. 3A).

The conductor layer of the first circuit board 10 is roughened, and a prepreg GEA-679FZPE (Hitachi Chemical Industry Co., Ltd.) having a nominal thickness of 0.04 mm in which both surfaces of the first circuit board 10 are impregnated with a glass cloth with an epoxy resin. (Trade name) manufactured by Co., Ltd., and 3 μm copper foil MT35S3 (trade name, manufactured by Mitsui Mining & Smelting Co., Ltd.) with 35 μm carrier copper foil is vacuum-pressed at 24.5 × 10 ⁵ Pa (25 kgf / cm ² ). The insulating resin layer 7 was formed by laminating under the conditions of a temperature of 175 ° C. and a holding time of 1.5 hours. At that time, the through hole 2 was filled with a resin resin 7 of prepreg GEA-679FZPE. Further, the carrier copper foil was peeled off to leave the 3 μm copper foil 17 to form the second circuit board 11 (FIG. 3B).

  A dry film NIT225 (trade name, manufactured by Nichigo Morton Co., Ltd.) is temporarily bonded to both surfaces of the second circuit board 11 with a laminator, a negative mask is laminated, exposed to ultraviolet rays, and the circuit is printed on both surfaces by baking with 1% carbonic acid. An etching resist is formed by developing with a sodium aqueous solution, a copper portion without the etching resist is removed with a ferric chloride aqueous solution, and the etching resist is peeled and removed with a 3% sodium hydroxide aqueous solution. A conformal mask 12 having a diameter of 0.15 mm to be a laser irradiation mask and a laser position recognition pattern are formed at a non-through hole installation location on the through hole 2 to form a third circuit board 13 (FIG. 3C). ).

  On both surfaces of the third circuit board 13, a carbon dioxide laser processing machine LC-1C / 21 (trade name, manufactured by Hitachi Via Mechanics Co., Ltd.) is used. Beam irradiation diameter Φ0.3 mm, frequency 500 Hz, pulse width 20 μs, 4-shot conditions Then, a 0.15 mm non-through hole 14 of ΦO4 was formed on the through hole 2 of the third circuit board 13 to form a fourth circuit board 15 (FIG. 3D).

  Electrolytic copper plating is applied to the fourth circuit board 15 to form a surface conductor layer, and then a dry film for etching resist NIT215 (product name, manufactured by Nichigo Morton Co., Ltd.) is temporarily bonded with a laminator, and a negative mask is laminated. After exposure to ultraviolet light, the circuit is baked on both sides, developed with 1% aqueous sodium carbonate solution to form an etching resist, and the copper part without the etching resist is removed with aqueous ferric chloride solution, and with 3% aqueous sodium hydroxide solution. The etching resist was peeled and removed to form a wiring (conductor layer) 3 to obtain a fifth circuit board 16 (FIG. 3E).

  As a result of evaluating the formability of the line / space = 40/40 μm of the first circuit board 10 which is the produced inner layer board, there was no defect such as disconnection or short circuit, and the line width was within 40 ± 5 μm. It was. Further, the cross section of the circuit board was observed, and the filling property of the insulating resin in the through hole was examined. As a result, it was confirmed that the entire number was filled.

(Comparative Example 1)
Insulating resin layer laminated with 3 μm thick copper foil Glass cloth base epoxy resin copper clad laminate MCL-E-679F (trade name, manufactured by Hitachi Chemical Co., Ltd.) with nominal thickness of 0.06 mm A through hole having a diameter of 0.25 mm was formed, electrolytic copper plating of 10 μm was applied to form a plated conductor layer, and a through hole having a diameter of 0.23 mm was formed. The through hole was filled with hole-filling ink SER-490BNH (trade name, manufactured by Yamaei Chemical Co., Ltd.), and further subjected to electrolytic copper plating of 10 μm to further form a plated conductor layer. Furthermore, dry film NIT215 (product name, manufactured by Nichigo-Morton Co., Ltd.) for etching resist is temporarily pressure-bonded with a laminator, a negative mask is laminated, exposed to ultraviolet rays, the circuit is printed on both sides, and developed with a 1% aqueous sodium carbonate solution. Then, the etching resist is formed, the copper portion without the etching resist is removed with a ferric chloride aqueous solution, and the etching resist is peeled and removed with a 3% aqueous sodium hydroxide solution, and lines / spaces = 40/40 μm wiring on both sides. To form a first circuit board. At that time, a land (conductor layer) of Φ0.40 mm was formed in the through hole.

  Thereafter, a circuit board was produced in the same manner as in Example 1. As a result of evaluating the formability of the line / space = 40/40 μm of the first circuit board as the produced inner layer board, some defects such as disconnection and short circuit occurred, and the line width was within 40 ± 10 μm Met.

  As described above, as shown in Example 1, the through-hole is also as small as Φ0.09 mm or less, and the non-through-hole is larger than this so as not to impair the high density of the circuit board. Therefore, the conductor layer of the inner layer plate is thin, and fine wiring can be formed. Further, the filling of the through hole with the insulating resin is performed simultaneously with the formation of the insulating resin layer on the surface of the conductor layer of the inner layer plate, the filling property is good, and the circuit board can be efficiently manufactured. On the other hand, Comparative Example 1 had a large through hole and required plating after filling the through hole with an insulating resin, so that the conductor layer of the inner layer plate was thick and it was difficult to form fine wiring.

It is sectional drawing of the connection hole structure of the circuit board of this invention. It is sectional drawing of the conventional circuit board. It is sectional drawing of the circuit board in the manufacturing process of the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner layer conductor layer 2 ... Through-hole 3 ... Conductor layer 4 ... Opening diameter (PHI) O of a non-through-hole
5 ... Inner wall diameter ΦI of the through hole
6 ... Diameter of inner conductor layer ΦL
7 ... Insulating resin (insulating resin layer)
8 ... Insulating resin for hole filling 9 ... Conductive material 10 ... First circuit board 11 ... Second circuit board 12 ... Conformal mask 13 ... Third circuit board 14 ..Non-through hole 15 ... fourth circuit board 16 ... fifth circuit board 17 ... copper foil 18 ... inner layer board

Claims (5)

  An inner layer plate having a plated through hole with an inner wall diameter of ΦI, an inner layer conductor layer with a diameter of ΦL provided in an opening of the through hole of the inner layer plate, an insulating resin layer formed on the surface of the inner layer conductor layer, A circuit board having a non-through hole reaching the inner conductor layer having an opening diameter ΦO located immediately above the through hole formed in the insulating resin layer, and a through hole having an inner wall diameter ΦI and an inner layer conductor layer having a diameter ΦL; A circuit board having at least one connection hole structure in which a non-through hole having an opening diameter of ΦO has a relationship of ΦI <ΦO <ΦL.   The circuit board according to claim 1, wherein the plated inner wall diameter ΦI is Φ0.001 to 0.09 mm.   The circuit board according to claim 1, wherein the inner conductor layer has a thickness of 1 μm to 20 μm.   A step of preparing an inner layer plate having a plated through hole with an inner wall diameter ΦI, a step of forming a conductor layer including an inner layer conductor layer having a diameter ΦL larger than the diameter ΦI at the opening of the through hole of the inner layer plate, A step of forming an insulating resin layer on the surface of the conductor layer including the inner layer conductor layer, a non-through hole reaching the inner layer conductor layer having an opening diameter ΦO larger than the diameter ΦI and smaller than the diameter ΦL immediately above the through hole in the insulating resin layer; A method for manufacturing a circuit board, comprising a step of forming at least one or more.   The method of manufacturing a circuit board according to claim 4, wherein the step of forming the insulating resin layer on the surface of the conductor layer including the conductor layer of ΦL includes a step of filling the through hole with the insulating resin.

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