JP2006313932A - Multilayer circuit board and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer circuit board wherein the connection resistance of a conductive through-hole is stable. <P>SOLUTION: The multilayer circuit board is constructed of an inner-layer circuit board obtained by forming a protruded circuit pattern having a certain thickness over a base material, a prepreg sheet, and a circuit pattern formed by laminating metal foil in the outermost layer. A smooth layer is formed over the regions of the base material of the inner-layer circuit board where the protruded circuit pattern is not formed, and the uniformity of heating and pressurization is thereby enhanced. As a result, conductive paste can be evenly compressed, and a multilayer circuit board with statable connection resistance is obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer circuit board formed by connecting at least two circuit patterns and a method for manufacturing the same.

  In recent years, with the miniaturization and high density of electronic devices, there has been a strong demand for multilayer circuit boards not only for industrial use but also for consumer use.

  In such a circuit board, it is indispensable to newly develop a connection method for connecting inner via holes between circuit patterns of a plurality of layers and a structure having high reliability. A high-density circuit board manufacturing method (JP-A-6-268345) has been proposed. A method for manufacturing this circuit board will be described below.

  Hereinafter, a method for manufacturing a conventional multilayer circuit board, here, a four-layer board will be described.

  First, a method of manufacturing a double-sided circuit board that is the base of a multilayer circuit board will be described.

  4 (a) to 4 (g) are process sectional views of a conventional method for manufacturing a double-sided circuit board for an inner layer. Reference numeral 21 denotes a prepreg sheet having a 250 mm square and a thickness of about 150 μm (t1). For example, a base material made of a composite material in which a non-woven aromatic polyamide fiber is impregnated with a thermosetting epoxy resin is used. 22a and 22b are release films having a thickness of about 16 μm each having a Si-type release agent applied on one side, and for example, polyethylene terephthalate is used.

  The prepreg sheet 21 and the release films 22a and 22b are bonded together by a method in which the resin components of the prepreg sheet 21 are melted using a laminating apparatus and the release films 22a and 22b are continuously bonded (Japanese Patent Laid-Open No. 7-106760). ) Has been proposed.

  Reference numeral 23 denotes a through hole, which is filled with a conductive paste 24 electrically connected to metal foils 25a and 25b such as copper having a thickness of 18 μm to be attached to both surfaces of the prepreg sheet 21.

  First, as shown in FIG. 4 (b), through-holes 23 are formed at predetermined locations on the prepreg sheet 21 (FIG. 4 (a)) having the release films 22a and 22b bonded on both sides, as shown in FIG. 4 (b). It is formed.

  Next, as shown in FIG. 4C, the conductive paste 24 is filled in the through holes 23. As a method of filling the conductive paste 24, the prepreg sheet 21 having the through holes 23 is placed on a table of a printing machine (not shown), and the conductive paste 24 is printed directly from the release film 22a. . At this time, the release films 22 a and 22 b play a role of a printing mask and a role of preventing contamination of the prepreg sheet 21.

  Next, as shown in FIG. 4 (d), the release films 22 a and 22 b are peeled from both surfaces of the prepreg sheet 21.

  And as shown in FIG.4 (e), metal foil 25a, 25b is piled up on both surfaces of the prepreg sheet | seat 21. FIG. Then, by heating and pressurizing in vacuum at a temperature of about 200 ° C. and a pressure of about 4 MPa for 1 hour, the thickness of the prepreg sheet 21 is compressed (t2 = about 100 μm) as shown in FIG. And metal foils 25a and 25b are bonded to each other, and the metal foils 25a and 25b on both sides are electrically connected by a conductive paste 24 filled in a through hole 23 provided at a predetermined position.

  Then, the metal patterns 25a and 25b on both sides are selectively etched to form circuit patterns 31a and 31b to obtain a circuit board on both sides.

  5A to 5D are process cross-sectional views showing a conventional method for manufacturing a multilayer circuit board, and show a four-layer board as an example.

  First, as shown in FIG. 5 (a), a double-sided circuit board 40 having circuit patterns 31a and 31b manufactured according to FIGS. 4 (a) to 4 (g) and a through-hole manufactured according to FIGS. 4 (a) to (d). Prepreg sheets 21a and 21b in which the holes 23 are filled with the conductive paste 24 are prepared.

  Next, as shown in FIG. 5B, the metal foil 25b, the prepreg sheet 21b, the double-sided circuit board 40 for the inner layer, the prepreg sheet 21a, and the metal foil 25a are positioned and stacked in this order.

Next, the thickness of the prepreg sheets 21a and 21b is increased as shown in FIG. 5C by curing the prepreg sheets 21a and 21b by heating and pressing at a pressure of about 4 MPa for 1 hour in a vacuum. The double-sided circuit board 40 is bonded to the metal foils 25a and 25b by being compressed (t2 = about 100 μm), and the circuit patterns 31a and 31b of the double-sided circuit board 40 are bonded to the metal foils 25a and 25b by the conductive paste 24 Inna via hole connected. And as shown in FIG.5 (d), a 4-layer board | substrate is obtained by selectively etching the metal foils 25a and 25b of both surfaces, and forming the circuit patterns 32a and 32b.
JP-A-6-268345 JP-A-7-106760

  In the above conventional multilayer circuit board manufacturing method, the strength and rigidity of the double-sided circuit boards used for the inner layer decrease as the plate thickness decreases.

  That is, as shown in FIG. 6, the circuit pattern 31a is formed on the surface where the circuit pattern 31b is not formed on the back surface of the double-sided circuit board 40, and the conductive paste 24 of the prepreg sheet 21a is compressed to connect the circuit pattern 32 to the outermost layer. When the connection is made, the double-sided circuit board 40 is deformed by the thickness corresponding to the circuit pattern 31b on the back surface due to the pressure applied to the conductive paste 24, and comes into contact with the prepreg sheet 21b.

  For this reason, compared with the conductive paste 24 of the symbol A, the conductive paste 24 of the symbol B is insufficiently compressed and the connection resistance may not be stable.

  In order to solve the above problems, a multilayer circuit board and a manufacturing method thereof according to the present invention include an inner layer circuit board in which a convex circuit pattern having a certain thickness is formed on a base material, a prepreg sheet, and a metal in an outermost layer. In a multilayer circuit board in which foil is laminated and a circuit pattern is formed, by forming a smooth layer on a base material on which the convex circuit pattern of the circuit board for the inner layer is not formed, The uniformity can be improved, which makes it possible to uniformly compress the conductive paste, and a multilayer circuit board with stable connection resistance can be obtained.

  As described above, the method for manufacturing a circuit board according to the present invention allows the double-sided circuit board to be deformed during heating and pressurization by forming a smooth layer on the double-sided circuit board for the inner layer having at least two circuit patterns. Thus, a multilayer circuit board with stable connection resistance can be obtained.

  The present invention provides a circuit board for an inner layer in which a convex circuit pattern having a constant thickness is formed on a base material, a prepreg sheet, and a multilayer circuit board in which a metal foil is laminated on the outermost layer to form a circuit pattern. A multilayer circuit board characterized in that a smoothing layer is formed on a base material on which the convex circuit pattern of the inner layer circuit board is not formed, whereby the convex circuit pattern of the circuit board and the The level | step difference by the unevenness | corrugation with the base material in which no is formed can be eliminated.

  Also, by making the thickness of the smooth layer equal to the thickness of the convex circuit pattern, the unevenness disappears even if the thickness of the circuit pattern of the circuit board is changed, and the conductive paste is uniformly compressed and has a stable connection resistance. can get.

  In the present invention, the circuit board for the inner layer has a double-sided connection structure through a through conduction hole filled with a conductive paste, and the prepreg sheet has a through conduction hole filled with a conductive paste, It is also possible to adopt a configuration having an outermost layer circuit pattern and an interlayer connection structure, and alternately and alternately position a plurality of compressible inner circuit boards and a plurality of compressible prepreg sheets. It is also possible to form a highly multilayer circuit board by sandwiching and laminating.

  Even in the above configuration, when the entire surface is heated and pressed to cure the prepreg sheet and the metal foil is bonded to the circuit board and electrically connected between the layers, the circuit board is not deformed, so the conductive paste is uniform. And a stable connection resistance can be obtained.

  In the present invention, interlayer adhesiveness can be improved and heat resistance and physical strength can be improved by making the material of the smooth layer the same as the curable resin constituting the prepreg sheet or the base material.

  The prepreg sheet or inner layer circuit board is made of a composite material of woven or non-woven fabric and thermosetting epoxy resin, which is mainly made of aromatic polyamide. It is possible to realize a multilayer circuit board having a high wiring capacity.

  Furthermore, the circuit board for the prepreg sheet or inner layer is made of a composite material of woven fabric or nonwoven fabric made of glass fiber and thermosetting epoxy resin, realizing a multilayer circuit substrate with high physical strength, high environmental characteristics and heat resistance. It can be done.

  In the present invention, the step of forming the smooth layer can also improve interlayer adhesion in multilayer formation by applying a curable resin to a semi-cured state. On the other hand, after applying and curing the curable resin, the surface By polishing the surface, the strength and rigidity of the circuit board for the inner layer are increased, so that the alignment at the time of stacking high multilayers is facilitated, and the positional shift due to the resin flow is prevented.

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

(Embodiment 1)
A first embodiment of a method for manufacturing a multilayer circuit board according to the present invention will be described.

  1 (a) to 1 (h) are process cross-sectional views of a method for producing an inner layer double-sided circuit board according to the present invention. 2A to 2D are process cross-sectional views illustrating a method for manufacturing a multilayer circuit board according to the present invention, and show a four-layer board as an example.

  First, a method for manufacturing an inner-layer double-sided circuit board serving as a base of a multilayer circuit board will be described.

  In FIG. 1, reference numeral 1 denotes a prepreg sheet having a 250 mm square and a thickness of about 130 μm (t1). For example, a base material made of a composite material in which a non-woven aromatic polyamide fiber is impregnated with a thermosetting epoxy resin is used. Reference numerals 2a and 2b denote release films having a thickness of about 16 μm each having a Si-type release agent applied on one side, and here, polyethylene terephthalate is used.

  The prepreg sheet 1 and the release films 2a and 2b are bonded together by melting and bonding the resin components of the prepreg sheet 1 using a laminating apparatus. 3 is a through hole, and 4 is a conductive paste. The used conductive paste 4 uses copper powder having an average particle diameter of 2 μm as a conductive filler, a thermosetting epoxy resin (solvent-free type) as a resin, and an acid anhydride type curing agent as a curing agent, respectively. Thoroughly kneaded with three rolls so as to be 1 wt%, 12.5 wt%, and 2.5 wt%. 5a and 5b are 300 mm square and 18 μm thick metal foil such as copper, and 7 is a smooth layer formed of a semi-cured epoxy resin.

  First, as shown in FIG. 1B, through-holes 3 are formed at predetermined positions of the prepreg sheet 1 (FIG. 1A) having the release films 2a and 2b bonded on both sides, as shown in FIG. 1B. Form.

  Next, as shown in FIG.1 (c), the through-hole 3 is filled with the electrically conductive paste 4, and a through-conduction hole is formed.

  As a method for filling the conductive paste 4, the prepreg sheet 1 having the through holes 3 is placed on a table of a printing machine (not shown), and the conductive paste 4 is directly filled from the release film 2 a. At this time, the release films 2 a and 2 b play a role of a printing mask and a prevention of contamination of the prepreg sheet 1.

  Next, as shown in FIG. 1 (d), the release films 2 a and 2 b are peeled from both surfaces of the prepreg sheet 1.

  And as shown in FIG.1 (e), metal foil 5a, 5b is piled up on both surfaces of the prepreg sheet 1. FIG.

  Then, by heating and pressurizing in vacuum at a temperature of about 200 ° C. and a pressure of about 4 MPa for 1 hour, the thickness of the prepreg sheet 1 is compressed (t2 = about 90 μm) as shown in FIG. And metal foils 5a and 5b are bonded to each other, and the metal foils 5a and 5b on both sides are electrically connected by a conductive paste 4 filled in a through hole 3 provided at a predetermined position.

  Next, as shown in FIG. 1G, the metal foils 5a and 5b on both sides are selectively etched to form convex circuit patterns 6a and 6b.

  And as shown in FIG.1 (h), both surfaces for inner layers which have the smooth layer 7 by providing the smooth layer 7 on the prepreg sheet | seat 1 as a base material used as the recessed part in which the circuit patterns 6a and 6b are not formed. A circuit board 20 is obtained.

  The smooth layer 7 is formed by applying a thermosetting epoxy resin diluted with a solvent such as methyl ethyl ketone to a level equivalent to the thickness of the circuit patterns 6a and 6b using a squeezing method, and heating at a temperature of about 150 ° C. for 2 minutes. As a result, the solvent component was volatilized to obtain a B-stage state.

  The thickness of the smooth layer 7 formed on both sides of the double-sided circuit board 20 was made substantially equal to the thickness of the circuit patterns 6a and 6b.

  Although the smooth layer 7 in the B stage state is used here, the epoxy resin is applied thicker than the circuit patterns 6a and 6b, heated to cure the epoxy resin, and then polished to expose the circuit patterns 6a and 6b. The smooth layer 7 may be formed.

  2A to 2D are process cross-sectional views illustrating the first method for manufacturing a multilayer circuit board according to the present invention, and show a four-layer board as an example.

  First, as shown in FIG. 2 (a), a smooth layer 7 is formed in the recesses on the substrate excluding the convex circuit patterns 6a and 6b, which are manufactured as shown in FIGS. A double-sided circuit board 20 in which the circuit patterns 6a and 6b on both sides are electrically connected with the paste 4 is prepared.

  Further, prepreg sheets 10a and 10b each having a through-conduction hole in which the through-hole 3 manufactured in FIGS. 1 (a) to 1 (d) is filled with the conductive paste 4 and a metal foil 8a such as copper having a 300 mm square and a thickness of 18 μm. , 8b are prepared.

  Next, as shown in FIG. 2B, the metal foil 8b, the prepreg sheet 10b having a through-conduction hole, the double-sided circuit board 20, the prepreg sheet 10a having a through-conduction hole, and the metal foil 8a are positioned in this order. And repeat.

  Then, the thickness of the prepreg sheets 10a and 10b is compressed (t2) as shown in FIG. 2C by curing the prepreg sheets 10a and 10b by heating and pressurizing in vacuum at a temperature of about 200 ° C. and a pressure of about 4 MPa for 1 hour. The double-sided circuit board 20 and the metal foils 8a and 8b are bonded together, and the circuit patterns 6a and 6b are connected to the metal foils 8a and 8b by the conductive paste 4 and the inner via holes.

  Then, as shown in FIG. 2D, a four-layer substrate is obtained by selectively etching the metal foils 8a and 8b on both sides to form circuit patterns 9a and 9b. In order to obtain a multilayer substrate having four or more layers, a multilayer circuit substrate manufactured by the above-described manufacturing method may be used instead of the double-sided circuit substrate, and the same process may be repeated.

  The multilayer circuit board produced by the manufacturing method of the present invention is provided with a smooth layer in the concave portion of the circuit pattern of the double-sided circuit board, so that the double-sided circuit board can be There was no deformation, the conductive paste was uniformly pressed, and the connection resistance was stabilized. Further, since the smooth layer was formed in advance in the concave portion of the circuit pattern, it was confirmed that the connection resistance was stable regardless of the thickness of the circuit pattern of the double-sided circuit board.

(Embodiment 2)
A second embodiment of the method for manufacturing a multilayer circuit board according to the present invention will be described.

  3A to 3C are process cross-sectional views illustrating a method for manufacturing a second multilayer circuit board according to the present invention, taking a six-layer board as an example.

  In FIG. 3, reference numerals 20a and 20b denote inner-layer double-sided circuit boards manufactured according to FIGS. 1A to 1H according to the first embodiment, and the smooth layer 7 is formed in the recesses of the circuit patterns 6a, 6b, 6c and 6d. The circuit patterns 6a and 6b and 6c and 6d on both sides are electrically connected by the conductive paste 4. 8a and 8b are metal foils such as copper having a 300 mm square and a thickness of 18 μm.

  Reference numerals 10a, 10b, and 10c denote prepreg sheets having a through-conduction hole with a thickness of 130 μm (t1) manufactured according to FIGS. 1A to 1D of the first embodiment. The through-hole 3 is filled with the conductive paste 4 is doing.

  First, the double-sided circuit boards 20a, 20b, the prepreg sheets 10a, 10b, 10c and the metal foils 8a, 8b are prepared.

  As shown in FIG. 3A, the metal foil 8b, the prepreg sheet 10c, the double-sided circuit board 20b, the prepreg sheet 10b, the double-sided circuit board 20a, the prepreg sheet 10a, and the metal foil 8a are positioned and stacked in this order.

  Next, the prepreg sheets 10a, 10b, and 10c are cured by heating and pressurizing in a vacuum at a temperature of about 200 ° C. and a pressure of about 4 MPa for 1 hour, as shown in FIG. Is compressed (t2 = about 90 μm), the double-sided circuit boards 20a and 20b are bonded to the metal foils 8a and 8b, and the circuit patterns 6a, 6b, 6c and 6d are made of metal foil by the conductive paste 4. 8a and 8b are connected to the inner via hole.

  Then, as shown in FIG. 3C, by selectively etching the metal foils 8a and 8b on both sides to form circuit patterns 9a and 9b, a six-layer multilayer circuit board can be obtained.

  It was confirmed that the multilayer circuit board manufactured by the second manufacturing method of the present invention can obtain the same effect as the multilayer circuit board manufactured by the manufacturing method of the first embodiment.

  In Embodiments 1 and 2, after a composite material in which a non-woven aromatic polyamide fiber is impregnated with a thermosetting epoxy resin is sandwiched between metal foils and heated and pressed to be cured, Although it explained using what removed metal foil by etching, after sandwiching a composite material impregnated with a thermosetting epoxy resin into a glass cloth with metal foil and curing by heating and pressing, The same effect has been confirmed even when the metal foil removed by etching is used.

  In the first and second embodiments, the double-sided circuit board manufactured by the manufacturing method of the present invention is used. However, a double-sided circuit board connected with metal deposited by electroplating after drilling holes between layers is used. However, it can be implemented by smoothing the recesses on the surface of the circuit board.

Process sectional drawing which shows the manufacturing method of the double-sided circuit board for inner layers of this invention Process sectional drawing which shows the manufacturing method of the 1st multilayer circuit board of this invention Sectional drawing which shows the manufacturing method of the 2nd multilayer circuit board of this invention Process sectional drawing which shows the manufacturing method of the double-sided circuit board for inner layers of a prior art example Cross-sectional process diagram illustrating a conventional method for manufacturing a multilayer circuit board Sectional drawing for demonstrating the subject in the multilayer circuit board in a prior art example

Explanation of symbols

1, 21a, 21b Prepreg sheet 2a, 2b, 22a, 22b Release film 3, 23 Through hole 4, 24 Conductive paste 5a, 5b, 8a, 8b, 25a, 25b Metal foil 6a, 6b, 6c, 6d, 9a, 9b Circuit pattern 7 Smooth layer 10 Pre-preg sheet having through-conduction holes 20, 40 Double-sided circuit board 31a, 31b, 32a, 32b Circuit pattern

Claims (7)

A double-sided circuit board having a plurality of convex circuit patterns formed on both the front and back sides of the substrate;
A layer obtained by laminating and curing a prepreg sheet on the surface of the circuit pattern;
The outermost layer circuit pattern formed on the surface of the layer on which the prepreg sheet is laminated and cured,
The prepreg sheet has a through conduction hole,
The convex circuit pattern has an outermost layer circuit pattern and an interlayer connection structure through the through conduction hole,
The double-sided circuit board has a smooth layer formed with a thickness equivalent to the convex circuit pattern in a concave portion on a base material on which no convex circuit pattern is formed,
The layer obtained by laminating and curing the prepreg sheet is laminated on the smooth circuit layer and the convex circuit pattern of the double-sided circuit board,
The plurality of convex circuit patterns of the double-sided circuit board having the through-conduction hole and the interlayer connection structure are configured with a circuit pattern on the opposite surface of the position where each circuit pattern is formed and a circuit pattern without the circuit pattern. A multilayer circuit board characterized by being made. The multilayer circuit board according to claim 1, wherein the material of the smooth layer is the same as the curable resin constituting the prepreg sheet or the base material. 2. The multilayer circuit board according to claim 1, wherein the prepreg sheet or the double-sided circuit board is a composite material of a woven or non-woven fabric mainly composed of an aromatic polyamide and a thermosetting epoxy resin. 2. The multilayer circuit board according to claim 1, wherein the prepreg sheet or the double-sided circuit board is a composite material of a woven or nonwoven fabric made of glass fiber and a thermosetting epoxy resin. 2. The multilayer circuit board according to claim 1, wherein the double-sided circuit board includes a through-conduction hole filled with a conductive paste, and the circuit patterns on both the front and back surfaces have a double-sided connection structure through the through-conduction hole. . The multilayer circuit board according to claim 1, wherein the prepreg sheet has compressibility. Preparing a double-sided circuit board having a convex circuit pattern having a constant thickness on both sides of the base material; and
Forming a smooth layer in a semi-cured state in a concave portion on a double-sided circuit board except on the convex circuit pattern;
Preparing a prepreg sheet having compressibility with a plurality of through-conduction holes filled with a conductive paste;
Laminating the prepreg sheet on the surface of the smooth layer and the convex circuit pattern on the circuit board for the inner layer, and further laminating metal foil on the outermost layer;
Heating and pressing the laminated double-sided circuit board, the prepreg sheet, and the metal foil, and electrically connecting the metal foil and the convex circuit pattern via the conductive paste; and
Processing the outermost metal foil to form a circuit pattern,
The plurality of convex circuit patterns of the double-sided circuit board connected to the through-conduction holes are configured with a circuit pattern on the opposite side of the position where each circuit pattern is formed and a circuit pattern without the circuit pattern. A method for manufacturing a multilayer circuit board.

Images