JP4033114B2 - Manufacturing method of multilayer printed wiring board - Google Patents

Description

  The present invention relates to a multilayer printed wiring board widely used in various electronic devices such as a mobile phone, a personal computer, and a video camera.

  In particular, electronic devices such as mobile phones and video cameras are becoming smaller and lighter, and printed wiring boards used for such electronic devices are required to have functions that have higher density and flexibility.

  The manufacturing method in the conventional multilayer printed wiring board will be described below.

  8A to 8C are cross-sectional views showing a conventional method for manufacturing a multilayer printed wiring board. In FIG. 8, 22 is an adhesive sheet for interlayer conduction having a conduction hole filled with a conductive paste and cut into a predetermined shape, and 23 is an inner layer material.

  First, as shown in FIG. 8A, after laminating copper foils on both surfaces of the interlayer conductive adhesive sheet 22, an inner layer material 23 in which a conductor pattern 24 is formed is obtained.

  Next, as shown in FIG. 8B, the interlayer conductive adhesive sheet 22 and the copper foil 21 cut into a predetermined shape using a laser beam are overlapped with an inner layer material 23 and sandwiched between a stainless steel plate and the like in a hot press machine. After setting and heating and pressurizing, a multilayer copper clad laminate as shown in FIG. 8C is obtained.

  A circuit board is formed on the surface layer, the conductor pattern 24 is provided inside, and each layer is electrically connected by a conductive paste or the like. Further, a multilayer printed wiring board having a part of a film and having flexibility obtain.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
Japanese Patent Laid-Open No. 10-200258

  However, in the above-described conventional multilayer printed wiring board configuration, when a flexible portion of the printed wiring board is bent multiple times at a high speed, interlayer adhesion is caused by the laminated portion in the vicinity of the flexible portion due to the impact. There is a possibility that delamination may occur in the multilayer laminated portion in the vicinity of the flexible portion.

  The present invention solves the above-mentioned conventional problems, can be easily folded, and has excellent conduction reliability between the circuit of the circuit board for the inner layer and the conductive paste of the adhesive sheet for interlayer conduction, and is repeatedly bent. However, it is possible to provide a method for producing a multilayer printed wiring board that can realize an excellent multilayer printed wiring board in which conductors are not cut and delamination does not occur in the multilayer laminated portion.

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

The present invention includes a step of preparing a flexible insulating sheet having a circuit formed on the surface layer, and a conductive paste in a through-hole provided in a semi-hard prepreg sheet in which a base material is impregnated with a thermosetting resin. A step of preparing a filled interlayer conductive adhesive sheet, a step of preparing a circuit board having a circuit formed on a surface layer, and laminating an interlayer conductive adhesive sheet and a circuit board on both sides of the flexible insulating sheet; comprising the step of crimping, the circuit formed on the flexible insulating sheet is also of a, characterized in that the surface has been roughened, using double-sided roughened copper foil on a flexible insulating sheet, or a circuit surface It is possible to bend easily by roughening the surface, and it is excellent in conduction reliability between the circuit of the inner layer circuit board and the conductive paste of the adhesive sheet for interlayer conduction. Multilayer Excellent multilayer printed wiring board causing no delamination in the branching can be realized.

The present invention is flexible insulating sheet in the circuit formed, it is than also characterized being roughened surface by using a double-sided Arakado foil, oxidation treatment such as blackening Regardless of the roughening due to, the electrical connection between the conductive paste of the adhesive sheet for interlayer conduction and the conductor of the inner layer material has the effect of improving the adhesive force so that it is not hindered by the oxide film.

The present invention is flexible insulating sheet in the circuit formed is also of a, characterized in that is roughened surface by subjecting a reduction treatment After oxidized, electrically conductive adhesive sheet interlayer conductive This has the effect of improving the adhesion so that the electrical connection between the conductive paste and the conductor of the inner layer material is not hindered by the oxide film.

The present invention is flexible insulating sheet is also of a characterized in that it is a polyimide film having an adhesive layer on both sides, since it is excellent in heat resistance at high temperatures such as soldering, heat in the multi-layer laminate portion Heating and pressing with a press becomes possible, and a high multi-layer can be realized. Furthermore, since it has an adhesive layer, it has an effect of stabilizing the adhesion of the flexible portion of the copper foil and the multilayer laminated portion to the circuit board and preventing delamination.

Further, according to the present invention , the flexible insulating sheet is divided into a flexible portion and a laminated portion, the flexible portion has only a circuit formed on the surface layer, and the laminated portion has a conduction hole and a circuit formed thereon. and than also characterized by forming a through hole and a circuit in the stacking portion, wiring capacity is high and can be realized a multilayer printed wiring board having flexibility.

The present invention is flexible insulating sheet is divided into the flexible portion and the laminated portion, the adhesive sheet and the circuit board interlayer conductive is also of a, characterized in that it is laminated only in the stacking section, stack By multilayering the portion, a multilayer printed wiring board having high wiring accommodation and flexibility can be realized.

The present invention is divided into the flexible portion and the laminated portion, the circuit of the flexible portion is than also characterized in that it is covered by a cover lay film, coating the flexible circuit portions Thus, the function as a solder resist and circuit protection can be achieved, and a flexible multilayer printed wiring board can be realized.

The present invention, the surface in contact with the circuit of the coverlay film adhesive layer is formed, the opposite surface is than also characterized in that the releasing treatment is applied, the flexible insulating sheet and circuit Adhesion can be improved. In addition, by performing a release treatment on the opposite surface, after the step of laminating the interlayer conductive adhesive sheet and the circuit board and thermocompression bonding, the portion corresponding to the flexible portion is easily removed when cut and removed. It has the effect of being able to.

Further, according to the present invention , the flexible insulating sheet is divided into a flexible part and a laminated part, and after laminating a release film only on the flexible part, an adhesive sheet for interlayer conduction and a circuit board are laminated and thermocompression bonded. it is than also characterized that, after the step of thermocompression bonding and laminating an adhesive sheet and the circuit board interlayer conductive, when cutting removes a portion corresponding to the flexible portion, can be removed with the release film And has the effect of improving workability.

In the present invention , the adhesive sheet for interlayer conduction and the circuit board are laminated on both sides of the flexible insulating sheet and thermocompression bonded, and then the adhesive sheet for interlayer conduction or the portion corresponding to the flexible part of the circuit board is cut and removed. it is than also characterized that, it is possible to form the After crimping laminated through hole portion of the adhesive sheet for a circuit board and interlayer conductive heat, a step of preparing an adhesive sheet for circuit boards and interlayer conductive It becomes easy.

The present invention, the portion corresponding to the flexible portion of the circuit board, in the step of preparing a circuit board, and than also characterized in that it is pre-cut removed, if the circuit board of the hard plate, previously By forming the through-hole portion by cutting and removing, it is possible to use a punching die or the like, and the productivity can be improved.

Further, the present invention is characterized in that after a predetermined portion of the interlayer conductive adhesive sheet or circuit board is cut and removed, the interlayer conductive adhesive sheet and circuit board are laminated on both sides of the flexible insulating sheet and thermocompression bonded. that is also of a, after the step of thermocompression bonding and laminating an adhesive sheet and the circuit board interlayer conductive, partially cut removed and the release film corresponding to the flexible portion becomes unnecessary, productivity can be improved It has the action.

The present invention, the adhesive sheet for interlayer conduction, after cutting and removing a predetermined portion is also of a characterized by curing a cut surface of the semi-cured state during the lamination and thermocompression bonding by curing a cut surface It has the effect of preventing protrusion due to fluidization of the resin and improving the reliability of the flexible portion.

Further, according to the present invention , the flexible insulating sheet is divided into a flexible part and a laminated part, and the predetermined part to be cut and removed of the interlayer conductive adhesive sheet or the circuit board is obtained by laminating the interlayer conductive adhesive sheet and the circuit board. wherein it flexible portion and the same position, characterized in are also of the perforated holes of the adhesive sheet or the circuit board for interlayer conduction are the same position as the flexible portion of the flexible insulating sheet Thus, in the adhesive part for interlayer conduction or the flexible part of the circuit board, it is not necessary to laminate them and cut and remove them after the thermocompression bonding, so that the productivity can be improved.

The present invention is also of a characterized by cutting and removing a predetermined portion by a laser, a half during lamination and thermocompression bonding by curing by performing the laser thermal cut surface simultaneously with laser cutting of a predetermined portion It has the effect of preventing protrusion due to fluidization of the cured resin and improving the reliability and productivity of the flexible portion.

The present invention, the adhesive layer, and also to, and the impregnated nonwoven or woven fabric of the prepreg sheet semi-cured epoxy resin, characterized in that one formed by semi-curing the epoxy resin, Since both adhesive layers on both sides of the flexible insulating sheet are epoxy resins, the adhesion and peelability of the epoxy resin with the PET film in a semi-cured state can be made substantially the same. The conditions for laminating and peeling can be unified, and conductive holes can be formed in the prepreg sheet and the flexible insulating sheet using the same production line, so that productivity can be improved.

In the present invention , the step of preparing a flexible insulating sheet having a circuit formed on the surface layer includes a step of laminating a copper foil on a flexible insulating sheet having an adhesive layer and thermocompression bonding, and a through hole. A step of performing copper plating on the copper foil surface and through-holes, a step of selectively removing the copper foil to form a circuit, and a step of roughening the surface of the circuit. also than the through hole with copper plating lamination portion, by forming a circuit, wiring capacity is high and can be easily realized a multilayer printed wiring board having flexibility.

In the present invention , the step of preparing a flexible insulating sheet having a circuit formed on the surface layer includes a step of laminating a PET film on the flexible insulating sheet having an adhesive layer, and forming a through hole by laser processing. A step, a step of filling the through-hole with a conductive paste, a step of peeling the PET film, a step of laminating and thermocompression-bonding copper foil, a step of selectively removing the copper foil and forming a circuit , and than also being a step of roughening the surface of the circuit, and a small-diameter through hole with a conductive paste laminated portion, it is possible to form a circuit of fine line, is significantly higher wiring capacity In addition, a flexible multilayer printed wiring board can be easily realized.

Further, in the present invention , the step of preparing an interlayer conductive adhesive sheet includes a step of laminating a PET film on a prepreg sheet, a step of forming a through hole by laser processing, and a step of filling the through hole with a conductive paste. , and than also being a step of peeling off the PET film, it is possible to form a small diameter of the introducing hole by conductive paste adhesive sheet interlayer conductive, high wiring capacity, and flexibility A multilayer printed wiring board having the above can be realized.

Further, in the present invention , the step of preparing an interlayer conductive adhesive sheet includes a step of laminating a PET film on a prepreg sheet, a step of forming a through hole by laser processing, and a step of filling the through hole with a conductive paste. a step of peeling off the PET film, it is than also characterized a step of cutting and removing a predetermined portion by a laser, it can be formed small-diameter through hole with a conductive paste on the adhesive sheet interlayer conductive Thus, a multilayer printed wiring board having high wiring accommodation and flexibility can be realized. In addition, after the step of laminating the adhesive sheet for interlayer conduction and the circuit board and thermocompression bonding, the part corresponding to the flexible part is cut off and the release film becomes unnecessary, so that the productivity can be improved, and further the cutting Curing the surface with the heat of a laser has the effect of preventing protrusion due to fluidization of a semi-cured resin during lamination and thermocompression bonding and improving the reliability and productivity of the flexible part.

Further, in the present invention , the step of preparing the circuit board includes the step of laminating copper foil on both surfaces of the interlayer conductive adhesive sheet, thermocompression bonding, the step of forming a circuit on the surface layer and preparing the inner layer circuit board, laminating by thermal compression bonding the copper foil on the outermost layer of and a conduction adhesive sheet on the circuit board and the alternate, also of being characterized by comprising the step of forming a circuit on its surface, wiring capacity of the circuit board In addition, it is possible to achieve a multilayer printed wiring board having high flexibility and high flexibility, and having flexibility.

In the present invention , the step of laminating the interlayer conductive adhesive sheet and the circuit board on both sides of the flexible insulating sheet and thermocompression bonding is performed by alternately laminating the interlayer conductive adhesive sheet with the circuit board and laminating copper foil on the outermost layer. and also of the characterized in that it comprises a step of thermocompression bonding, it is possible to achieve a higher wiring capacity and high multilayered, and can be realized a multilayer printed wiring board having flexibility.

  The present invention can be easily folded by using a double-sided roughened copper foil for the flexible insulating sheet or roughening the circuit surface, and can be bonded to the circuit of the circuit board for the inner layer and the interlayer conduction. The sheet has excellent conduction reliability with the conductive paste, and has the effect of realizing an excellent multilayer printed wiring board that does not cause conductor cutting or delamination at the multilayer laminated portion even when it is repeatedly bent.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to the drawings.

  1A to 1E are cross-sectional views illustrating a method for manufacturing a multilayer printed wiring board according to Embodiment 1 of the present invention. 1A is a step of preparing a flexible insulating sheet having a circuit formed on its surface, FIG. 1B is a step of preparing an adhesive sheet for interlayer conduction, and FIG. 1C is a circuit board. Step, FIG. 1 (d) shows a step of laminating an adhesive sheet for interlayer conduction and a circuit board on both sides of the flexible insulating sheet and thermocompression bonding.

  First, the configuration of the flexible insulating sheet 1 having a circuit formed on the surface layer shown in FIG.

  The surface of the circuit 4 formed on the flexible insulating sheet 1 is roughened. The roughening of the surface can be realized by using a double-sided roughened copper foil or by performing a reduction treatment after oxidation treatment.

  The flexible insulating sheet 1 is a polyimide film having adhesive layers on both sides. The adhesive layer is formed by semi-curing an epoxy resin (advantageous for PET peeling).

  The flexible insulating sheet 1 is divided into a flexible portion F and a laminated portion R, and the circuit 4 of the flexible portion F is covered with a cover lay film 5 and is in contact with the circuit 4 of the cover lay film 5. An adhesive layer is formed on the surface, and a release treatment is performed on the opposite surface.

  The manufacturing process of the circuit 4 of the flexible insulating sheet 1 is performed by laminating a copper foil on a polyimide film having an adhesive layer on both sides and thermocompression bonding, and then selectively removing the copper foil to form a circuit. The surface is roughened (however, it is not necessary when double-sided roughened copper foil is used).

  By using the double-sided roughened copper foil or roughening treatment, a sufficient adhesive force can be obtained while ensuring the electrical connection reliability of the conductive paste of the interlayer conductive adhesive sheet 2 described later.

  Next, the configuration of the interlayer conductive adhesive sheet 2 shown in FIG.

  The interlayer conductive adhesive sheet 2 has a configuration in which a conductive paste 10 is filled in a through hole provided in a semi-hard prepreg sheet 2a in which a base material is impregnated with a thermosetting resin.

  The prepreg sheet 2a is obtained by impregnating an aramid nonwoven fabric or woven fabric, or a glass nonwoven fabric or woven fabric with an epoxy resin and semi-curing it. The manufacturing process is shown in FIG.

  First, as shown in FIGS. 2 (a) and 2 (b), a prepreg sheet 2a is laminated with a PET film 8, and a through-hole 9 is formed thereon by laser processing. Next, FIGS. As shown in FIG. 2, the through-hole 9 is filled with the conductive paste 10, and the PET film 8 is peeled off to obtain the interlayer conductive adhesive sheet 2.

  Next, the configuration of the circuit board 3 on which the circuit 4 is formed on the surface layer shown in FIG.

  The circuit board 3 is manufactured by laminating a copper foil 11 having both surfaces roughened on both surfaces of the interlayer conductive adhesive sheet 2 to form a circuit on the surface layer, and then forming the flexible insulating sheet 1 on the surface. A portion corresponding to the flexible portion F is cut and removed in advance using laser processing or a punching die to form a through hole 7.

  The flexible insulating sheet 1, the interlayer conductive adhesive sheet 2, and the circuit board 3 are prepared by the above process.

  Next, as shown in FIG. 1 (d), the release film 6 is laminated only on the flexible portion F of the flexible insulating sheet 1 divided into the flexible portion F and the laminated portion R, and then the interlayer The conductive adhesive sheet 2 and the circuit board 3 are laminated by sandwiching them with a stainless steel plate or the like in a hot press machine. As shown in FIG. 1 (e), after thermocompression bonding, the portion corresponding to the flexible portion F of the interlayer conductive adhesive sheet 2 is cut with a laser, removed together with the release film 6, 7 is formed.

  It is possible to cut and remove a predetermined portion corresponding to the flexible portion of the circuit board 3 after laminating the flexible insulating sheet 1, the interlayer conductive adhesive sheet 2, and the circuit board 3 and thermocompression bonding. In view of productivity and quality, as shown in FIG. 1C of the present embodiment, the portion corresponding to the flexible portion F of the circuit board 3 is previously cut and removed to form the through holes 7. Is also desirable.

In addition to the embodiments described above, the following embodiments may be employed.
(1) It is also possible to adopt a configuration in which the flexible insulating sheet 1, the flexible portion F shown in FIG. 3 (f) is the circuit 4, and the laminated portion R is formed with the conduction hole 10 and the circuit 4. is there. Thereby, the density of the circuit can be increased.

  A method for manufacturing the flexible insulating sheet 1 shown in FIG. 3 will be described.

  First, as shown in FIGS. 3A and 3B, a PET film 8 is laminated on a flexible insulating sheet 1a having an adhesive layer, and through holes 9 are formed by laser processing.

  Next, after filling the through hole 9 with the conductive paste 10 and peeling off the PET film 8, the roughened copper foil 11 having both surfaces roughened is laminated and thermocompression bonded to electrically connect both surface layers through the conductive hole 10. Are connected {FIG. 3 (c) to (e)}.

Next, as shown in FIG. 3 (f), the copper foil 11 is selectively removed to form the circuit 4, the flexible portion F includes only the circuit 4, and the laminated portion R includes the conduction hole 10 and the circuit 4. The formed flexible insulating sheet 1 is obtained.
(2) The flexible insulating sheet 1 may employ a configuration having the through hole 13 shown in FIG.

As shown in FIGS. 4A to 4D, the manufacturing process is performed by laminating a copper foil 11 having both surfaces roughened on a flexible insulating sheet 1a having an adhesive layer, thermocompression bonding, and drilling. After forming the through hole 9 and applying the copper plating 12 to the surface of the copper foil 11 and in the through hole 9, the copper foil 11 is selectively removed to form the circuit 4, and the flexible insulation having the plated through hole 13 Sheet 1 is obtained.
(3) The circuit board 3 may employ a multilayer circuit board having a four-layer structure shown in FIG. As a result, high density can be realized.

  FIG. 5 shows a method for manufacturing a multilayer circuit board having a four-layer structure.

  First, as shown in FIG. 5A, after laminating the interlayer conductive adhesive sheet 2 and the copper foil 11 on both sides of the inner circuit board 3a, and thermocompression bonding, as shown in FIG. 5B, A circuit 4 is formed on the surface layer to obtain a circuit board 3 having a four-layer structure.

It is also possible to obtain a circuit board having four or more layers after alternately laminating the plurality of inner layer circuit boards 3 and the plurality of interlayer conductive adhesive sheets 2 and laminating the copper foils 11 on the outermost layer. .
(4) The flexible insulating sheet 1, the interlayer conductive adhesive sheet 2, and the circuit board 3 shown in FIG. 1 (d) are laminated, and the thermocompression bonding step is performed by alternately interposing the interlayer conductive adhesive sheet 2 with the circuit board 3. It is also possible to laminate the copper foil 11 on the outermost layer and perform thermocompression bonding. As a result, higher density and higher layers can be realized.

  In addition, the lamination and thermocompression bonding process of FIG. 1 (d) includes the flexible insulating sheet 1 {FIG. 6 (a)} divided into the flexible portion F and the laminated portion R, and the interlayer conductive adhesive sheet 2 {FIG. 6 (b)} and the circuit board 3 {FIG. 6 (c)} may be laminated and thermocompression bonded to only the left and right laminated portions R as shown in FIG. 6 (d). Thus, after thermocompression bonding in FIG. 1 (e), the step corresponding to the flexible portion F of the interlayer conductive adhesive sheet 2 is cut with a laser to form the through holes 7 and the release film 6. Is no longer necessary.

(Embodiment 2)
Embodiment 2 of the present invention will be described below with reference to the drawings.

  In the present embodiment, the same parts as those in the first embodiment will be described using the drawings and reference numerals used in the first embodiment, and only different forms will be described.

  7A to 7E are cross-sectional views illustrating a method for manufacturing a multilayer printed wiring board according to Embodiment 2 of the present invention.

  FIG. 7A is a step of preparing a flexible insulating sheet 1 having a circuit formed on the surface layer, and FIG. 7C is a step of preparing a circuit board, and FIG. 1A and FIG. This is the same as (c), and the description is omitted.

  First, the interlayer conductive adhesive sheet 2 shown in FIG. 7B is formed by cutting and removing a predetermined portion by laser processing after the steps of FIGS. obtain. By using laser processing, the cut surface of the through hole 7 can be cured. Thereby, since the cut surface is melt-cured by the heat at the time of laser processing, resin flow at the time of lamination can be prevented, and a highly accurate flexible portion can be formed simultaneously with cutting.

  Further, the through hole 7 of the interlayer conductive adhesive sheet 2 and the circuit board 3 is flexible when the flexible insulating sheet 1, the interlayer conductive adhesive sheet 2 and the circuit board 3 of FIG. It is provided to be at the same position as the portion F.

  Thereafter, as shown in FIG. 7E, thermocompression bonding is performed to obtain a multilayer printed wiring board.

  When the characteristics of the multilayer printed wiring board using the manufacturing method of the present invention and the conventional multilayer copper clad laminate are compared, when the printed wiring board is bent at a right angle in the conventional method, the interlayer adhesion of the laminated portion is low, There was a possibility that delamination occurred in the laminated portion, but no delamination occurred in the present invention.

  Moreover, even if bending was repeated 10,000 times, an excellent effect was obtained in that no cutting of the conductor pattern or cracks in the laminated plate occurred.

  As described above, according to the present invention, it is possible to provide a multilayer printed wiring board that is partially flexible and can be bent.

  As described above, the present invention can be easily bent by using a double-sided roughened copper foil for the flexible insulating sheet or by roughening the circuit surface. A method for producing a multilayer printed wiring board that is excellent in conduction reliability with the conductive paste of the adhesive sheet for interlayer conduction, and that can realize an excellent multilayer printed wiring board that does not cause conductor cutting or delamination in the multilayer laminated portion even when repeatedly bent. The industrial applicability is great.

Sectional drawing which shows the manufacturing method of the multilayer printed wiring board in Embodiment 1 of this invention Sectional drawing which shows the manufacturing method of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing method of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing method of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing method of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing method of the multilayer printed wiring board in the embodiment Sectional drawing which shows the manufacturing method of the multilayer printed wiring board in Embodiment 2 of this invention Sectional drawing which shows the manufacturing method of the conventional multilayer printed wiring board

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Flexible insulating sheet 2 Interlayer conduction adhesive sheet 3 Circuit board 4 Circuit 5 Coverlay film 6 Release film 7 Through hole 8 PET film 9 Through hole 10 Conductive paste 11 Copper foil 12 Copper plating 13 Plating through hole

Claims (2)

Preparing a flexible insulating sheet with a circuit formed on the surface layer;
A step of preparing an adhesive sheet for interlayer conduction in which a through-hole provided in a prepreg sheet in a semi-hard state in which a base material is impregnated with a thermosetting resin is filled with a conductive paste;
Preparing a circuit board having a circuit formed on a surface layer;
A step of laminating the interlayer conductive adhesive sheet and the circuit board on both sides of the flexible insulating sheet and thermocompression bonding,
The surface of the circuit formed on the flexible insulating sheet is roughened,
The flexible insulating sheet is divided into a flexible part and a laminated part,
Before the step of thermocompression bonding, the circuit of the flexible portion has an adhesive layer formed on one surface in advance, and the opposite surface is covered with a cover lay film that has been subjected to a release treatment. Coated to contact the circuit of the flexible part,
A portion corresponding to the flexible portion of the circuit board is removed in advance before the thermocompression bonding step,
The method of manufacturing a multilayer printed wiring board, wherein a portion corresponding to the flexible portion of the interlayer conductive adhesive sheet is cut and removed after the thermocompression bonding step. Preparing a flexible insulating sheet with a circuit formed on the surface layer;
A step of preparing an adhesive sheet for interlayer conduction in which a through-hole provided in a prepreg sheet in a semi-hard state in which a base material is impregnated with a thermosetting resin is filled with a conductive paste;
Preparing a circuit board having a circuit formed on a surface layer;
A step of laminating the interlayer conductive adhesive sheet and the circuit board on both sides of the flexible insulating sheet and thermocompression bonding,
The surface of the circuit formed on the flexible insulating sheet is roughened,
The flexible insulating sheet is divided into a flexible part and a laminated part,
A release film is laminated on the flexible portion of the flexible insulating sheet before the thermocompression bonding step,
A portion corresponding to the flexible portion of the circuit board is removed in advance before the thermocompression bonding step,
The method of manufacturing a multilayer printed wiring board, wherein a portion corresponding to the flexible portion of the interlayer conductive adhesive sheet is cut and removed after the thermocompression bonding step.

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