JP2006231640A - Insulating material for printed wiring board and manufacturing method of printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulating material A for a printed wiring board B formed by laminating a cured resin layer 2, an adhesive layer 3 and a protective film layer 4 and to enhance the continuity reliability by preventing a viahole 9 from becoming long and large when the printed wiring board B is manufactured while preventing the lowering of reliability caused by the heat history of the printed wiring board B. <P>SOLUTION: The dimension between the contact surface with the adhesive layer 3 of the cured resin layer 2 and the surface of the glass cloth 1 in the cured resin layer 2 is set to 10 μm or below. A through-hole 5 is bored in the insulating material A for the printed wiring board B so as to pierce the insulating material A in its thickness direction and, after the through-hole 5 is filled with a conductive paste 6, the protective film layer 4 is peeled from the adhesive layer 3 and heating pressure molding is further performed in a state that a conductive layer 7 is laminated and superposed on the adhesive layer 3 to obtain the printed wiring board B characterized in that the length of the viahole 9 is prevented from becoming long, the coefficient of thermal expansion of the whole of an insulating layer 8 is reduced and the difference of the coefficient of thermal expansion between the conductive paste 6 and the insulating layer 8 in the viahole 9 is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an insulating material for a printed wiring board used for manufacturing a printed wiring board used in, for example, an electronic device, an electric device, a computer, a communication device, and the like, and a printed wiring board using the insulating material for a printed wiring board. It is related with the manufacturing method.

  In recent years, electronic components such as semiconductor chips and chip components are becoming lighter and thinner, and accordingly, there is an increasing demand for high-density wiring of printed wiring boards on which these electronic components are mounted. For this reason, a multilayer structure in which interstitial via holes (hereinafter sometimes referred to as IVH) are formed for each layer has a higher wiring density than conventional multilayer substrates having through-holes, and has attracted attention. Yes.

  The usefulness of such a multilayer wiring board having IVH has been recognized for a long time as disclosed in Japanese Patent Publication No. 45-13303, but in recent years, a paste for forming a laser processing technique or IVH has been used. With the progress of printing technology, epoch-making methods such as those disclosed in JP-A-8-255982 and JP-A-9-36551 have been proposed. In particular, in the case of an all-layer IVH substrate by the method disclosed in Japanese Patent Application Laid-Open No. 9-36551, the number of presses for laminate molding has been greatly reduced, and the manufacturing process has been refined.

And in patent document 1, as shown in FIG. 2, the protection layer which consists of the adhesive layer 3 which consists of an epoxy resin composition etc. on both surfaces of the cured resin layer 2 which impregnated and hardened the epoxy resin to the glass cloth 1, and PET film etc. Using the material A ′ in which the film layer 4 is sequentially arranged (FIG. 2A), the through-hole 5 for forming the via hole 9 is formed and filled with the conductive paste 6, and then the PET film is peeled off. A method of manufacturing a printed wiring board B ′ (FIG. 2B) in which a conductor layer 7 such as a copper foil or a conductor wiring 7a is laminated is proposed.
JP 2002-103494 A

  However, when manufacturing an insulating material formed by laminating the cured resin layer 2, the adhesive layer 3, and the protective film as described above, there are the following problems.

  That is, as the cured resin layer 2 including the glass cloth 1, a general single-sided substrate, or a copper foil on the surface of the copper-clad laminate is etched away. In such a cured resin layer 2, Between the surface of the glass cloth 1 and the surface of the insulating layer 8, the thickness (resin thickness W ′) usually exceeds 10 μm in order to cover the rough surface of the copper foil to be removed (processing foot). In the case where a resin is present and the cured resin layer 2 is formed on an unclad substrate not provided with a copper foil, the resin thickness W ′ is similarly set so that the glass cloth 1 is not exposed on the surface. It exceeded 10 μm. When the adhesive layer 3 is formed on the cured resin layer 2 as described above, the overall thickness is further increased. For this reason, when the insulating layer 8 of the printed wiring board B is formed by the cured resin layer 2 and the adhesive layer 3, the thickness of the insulating layer 8 is increased, and a via hole 9 ( The length of IVH) is also increased. When the length of the via hole 9 is increased in this manner, the electrical resistance value of the via hole 9 increases accordingly, leading to a decrease in conduction reliability. In order to maintain this conduction reliability, By increasing the cross-sectional area, it is necessary to maintain the electrical conductivity of the via hole 9, and a situation reverse to the densification of the wiring occurs.

  In addition, the conductive paste 6 in the via hole 9 has a smaller thermal expansion coefficient than the insulating layer 8 composed of the cured resin layer 2 and the adhesive layer 3 as described above. Therefore, the processing steps after the formation of the via hole 9 are performed. When a load due to heat is applied when the printed wiring board B ′ is used, the conductive paste 6 in the via hole 9 and the conductor wiring 7a connected to the via hole 9 due to the difference in thermal expansion There was also a problem that peeling or the like occurred between the layers and the heat resistance reliability was lowered.

  The present invention has been made in view of the above points, and relates to an insulating material for a printed wiring board formed by laminating a cured resin layer, an adhesive layer, and a protective film layer, and a printed wiring board is manufactured using the insulating material. The present invention provides an insulating material for a printed wiring board that can prevent the via hole from becoming long and maintain high conduction reliability in the via hole, and a printed wiring board manufacturing method using the insulating material. It is the purpose.

  Another object of the present invention is to prevent a decrease in reliability due to the thermal history of the printed wiring board B manufactured from the insulating material A for printed wiring boards.

  Insulating material A for printed wiring board of the present invention has an adhesive layer 3 made of a thermosetting resin composition in a B-stage state on both sides of a cured resin layer 2 obtained by impregnating and curing a glass cloth 1 with a thermosetting resin composition. Are provided, the protective film layer 4 is laminated on the outer surface of each adhesive layer 3, and the surface of the cured resin layer 2 in contact with the adhesive layer 3 and the surface of the glass cloth 1 in the cured resin layer 2 The dimension between is 10 μm or less. Using such a printed wiring board insulating material A, a through hole 5 penetrating in the thickness direction is formed in the printed wiring board insulating material A, and the through hole 5 is filled with a conductive paste 6 and then protected. The printed wiring board B having a via hole can be produced by peeling the film layer 4 from the adhesive layer 3 and further performing heat and pressure molding in a state where the conductor layer 7 is laminated and stacked on the adhesive layer 3. . In the printed wiring board B formed in this manner, the insulating layer 8 formed of the cured resin layer 2 and the adhesive layer 3 can be formed thin. For this reason, the via formed in the insulating layer 8 can be formed. An increase in the length of the hole can be prevented. In addition, in the insulating layer 8 composed of the glass cloth 1 and the cured thermosetting resin, since the proportion of the glass cloth 1 is relatively large, the thermal expansion coefficient of the entire insulating layer 8 is reduced, For this reason, the difference in thermal expansion coefficient between the conductive paste 6 and the insulating layer 8 in the via hole 9 is reduced.

  In the insulating material A for printed wiring boards, the glass transition point when the adhesive layer 3 is cured by heating is preferably higher by 10 ° C. than the glass transition point of the cured resin layer 2. In this case, the thermal expansion coefficient of the insulating layer 8 is small, and the temperature range where the difference in the thermal expansion coefficient between the conductive paste 6 and the insulating layer 8 in the via hole 9 is small can be widened.

  Moreover, the method for manufacturing the printed wiring board B of the present invention includes the step of drilling the through hole 5 penetrating in the thickness direction in the insulating material A for printed wiring board as described above, and the conductive paste 6 in the through hole 5. A step of filling, a step of peeling off the protective film layer 4 from the adhesive layer 3, and a step of heat-pressing in a state in which the conductor layer 7 is laminated and stacked on the adhesive layer 3 It is.

  According to the present invention, in a printed wiring board in which a via hole made of an insulating material for a printed wiring board is formed, an increase in the length of the via hole formed in the insulating layer is prevented, and the electrical property of the via hole is prevented. The increase in the resistance value can be suppressed, and the conduction reliability in the via hole can be maintained at a high level. In addition, the difference in thermal expansion coefficient between the conductive paste and the insulating layer in the via hole is also reduced. Even if a heat load is applied when using various processes after forming via holes or using a printed wiring board, peeling between the via holes and the conductor layer is less likely to occur. The heat resistance reliability can be improved.

  The insulating material A for printed wiring boards according to the present invention is configured by sequentially laminating an adhesive layer 3 and a protective film layer 4 on both surfaces of the cured resin layer 2 respectively.

  The cured resin layer 2 has a structure in which a glass cloth 1 is impregnated and cured with a thermosetting resin composition, and the surface of the cured resin layer 2 that is in contact with the adhesive layer 3 and the cured resin layer 2. The dimension between the inner surface of the glass cloth 1 is 10 μm or less.

  The cured resin layer 2 is heated in a state in which a metal foil such as a copper foil is disposed on both surfaces of a prepreg in which a glass cloth 1 is impregnated with a thermosetting resin varnish such as an epoxy resin varnish and then dried by heating. After obtaining a double-sided metal foil-clad laminate by curing, it can be formed by removing the metal foils on both sides by etching or the like. Further, the cured resin layer 2 is formed on an unclad substrate obtained by peeling the release foil after heat-curing in a state where a release film such as a release film or aluminum foil is disposed on both surfaces of the prepreg. You may do it. Thus, when forming the cured resin layer 2, the dimension between the surface of the cured resin layer 2 and the surface of the glass cloth 1 in the cured resin layer 2, that is, the surface of the cured resin layer 2 and the glass cloth 1 The impregnation amount of the thermosetting resin varnish to the glass cloth 1 and the molding thickness at the time of curing molding are adjusted so that the thickness of the resin existing between the surfaces (hereinafter referred to as the resin thickness W) is 10 μm or less. Is. At this time, the difference between the thickness of the glass cloth 1 and the thickness of the cured resin layer 2 is 0.02 mm or less.

  The resin thickness W is preferably as thin as possible. The thickness may be 0 and the glass cloth 1 may be exposed on the surface of the cured resin layer 2, but this thickness is preferably 1 μm or more.

  If the resin thickness W in the cured resin layer 2 is thus reduced, the glass cloth 1 may be exposed on the surface of the cured resin layer 2, and a metal foil such as a copper foil is temporarily provided to the cured resin layer 2. Although there is a possibility that sufficient adhesion strength may not be obtained when the conductive layer 7 of metal film is laminated and formed, the adhesive layer 3 is provided on the cured resin layer 2 so that the glass cloth 1 is exposed. This is covered with the adhesive layer 3, and the adhesive layer 3 can ensure adhesion with a metal foil or a metal film. By reducing the resin thickness W in this way, the thickness of the entire cured resin layer 2 can be reduced, and as a result, the insulating layer 8 of the printed wiring board B composed of the cured resin layer 2 and the adhesive layer 3. The thickness can be reduced.

  The adhesive layer 3 is formed of a thermosetting resin composition in a B stage state. Examples of the thermosetting resin composition for forming the adhesive layer 3 may include appropriate ones. For example, in addition to an epoxy resin composition containing an epoxy resin and a curing agent, a polyimide system, a bismaleimide triazine system Thermosetting resin compositions such as acrylates and phenols can be used. The thickness of the adhesive layer 3 is appropriately adjusted to such an extent that sufficient adhesion with a metal foil or a metal film can be ensured. However, if this thickness is excessive, the thickness of the insulating layer 8 is increased. The thickness is preferably in the range of 50 μm or less.

  Moreover, although the protective film layer 4 can be formed with an appropriate sheet material, for example, it can be formed with a sheet material made of polyethylene terephthalate. Here, since the protrusion dimension from the through-hole 5 of the conductive paste 6 is determined by the thickness of the protective film layer 4 as described later, the thickness of the protective film layer 4 ensures a sufficient amount of protrusion of the conductive paste 6. However, the thickness is preferably adjusted to be in the range of 12 to 50 μm.

  The adhesive layer 3 and the protective film layer 4 can be formed by an appropriate method. For example, a thermosetting resin composition for forming the adhesive layer 3 is formed on both surfaces of the cured resin layer 2 by a roll coater, a curtain coater, or a spray. After coating and drying by means such as coater and screen printing, the sheet material to be the protective film layer 4 is laminated and disposed, and the thermosetting resin composition is semi-cured by heating in this state to be a B stage State. Thereby, the adhesive layer 3 is formed with the thermosetting resin composition in the B-stage state, and the protective film layer 4 is formed with the sheet material. Moreover, after applying the thermosetting resin composition for forming the adhesive layer 3 on one surface of the sheet material to be a protective sheet, this may be laminated on both surfaces of the cured resin layer 2 using a hot roll or the like. In this case as well, the adhesive layer 3 is formed with the thermosetting resin composition in the B-stage state, and the protective film layer 4 is formed with the sheet material.

  In the insulating material A for printed wiring board thus formed, the specific composition of the thermosetting resin composition for constituting the cured resin layer 2 and the adhesive layer 3 is not particularly limited. In order to obtain excellent heat resistance reliability as described later, the glass transition point when the adhesive layer 3 is heated and cured is preferably higher by 10 ° C. or more than the glass transition point of the cured resin layer 2. To be. At this time, each thermosetting resin composition for forming the cured resin layer 2 and the adhesive layer 3 is to determine each composition so that the glass transition point of the cured product satisfies the above-mentioned conditions. A thermosetting resin composition for forming the adhesive layer 3 is used as the thermosetting resin composition for forming the cured resin layer 2 with a glass transition point of the cured product in the range of 120 to 180 ° C. It is preferable that the cured product has a glass transition point in the range of 120 to 200 ° C., and that the difference between the two glass transition points is in the range of 10 to 20 ° C. Specifically, for example, the cured resin layer 2 is formed of an FR-4 grade thermosetting resin composition having a cured product having a glass transition point of 120 ° C., and the adhesive layer 3 is formed of a glass transition point of the cured product. Can be formed with an FR-5 grade thermosetting resin composition having a temperature of 180 ° C.

  Next, the manufacturing method of the printed wiring board B using such insulating material A for printed wiring boards is demonstrated.

  First, the insulating material A for printed wiring board is subjected to drilling, laser processing, or the like, whereby one protective sheet material, one adhesive layer 3, the cured insulating layer 8, the other adhesive layer 3, and the other protective film layer 4 A through hole 5 is sequentially drilled. The opening diameter of the through-hole 5 is not particularly limited, but in order to sufficiently reduce the electrical resistance value of the via hole 9 and prevent a decrease in wiring density due to excessive increase in diameter, the diameter should be in the range of 100 to 500 μm. Is preferred.

  Next, from one protective film layer 4 side, a conductive paste 6 such as a silver paste is filled into the through holes 5 by a printing method or the like, and then the protective film layers 4 on both sides are peeled off. At this time, the conductive paste 6 protrudes from the through hole 5 by the thickness of the protective film layer 4.

  Next, it heat-press-molds in the state which has arrange | positioned the conductor layer 7 which consists of metal foil etc. on the surface of each exposed adhesive layer 3, respectively.

  At the time of this heat and pressure molding, the adhesive layer 3 is once melted by heating and then thermally cured. For this reason, the adhesive layer 3 and the conductor layer 7 (metal foil) are in close contact, and at the same time, the cured resin layer 2 An insulating layer 8 is formed by the adhesive layer 3 on both sides thereof.

  Further, at this time, the portion of the conductive paste 6 protruding from the through hole 5 is in close contact with the conductor layer 7 (metal foil), thereby conducting between the conductor layers 7 (metal foil) on both sides at the position where the through hole 5 is formed. A via hole 9 is formed.

  Next, the conductor wiring 7a is formed by subjecting the conductor layer 7 (metal foil) on both sides of the insulating layer 8 to an additive method, a subtractive method, or the like as necessary. Thereby, the printed wiring board B in which the conductor wiring 7a is formed on both surfaces can be obtained.

  The conductor layer 7 that overlaps one or both of the adhesive layers 3 is not limited to the metal foil as described above. For example, what formed the metal film by which the wiring process was made as the conductor layer 7 on the surface of peeling films, such as a polyethylene terephthalate film, can also be used. In this case, in the state where the release film is arranged so that the conductor layer 7 made of a metal film overlaps each adhesive layer 3 on the surface of each adhesive layer 3 exposed by peeling off the protective film layer 4, heat-press molding To do. At this time, a predetermined position in the conductor layer 7 (metal film) is overlapped with the conductive paste 6 protruding from the through hole 5. Even during the heat and pressure molding, the adhesive layer 3 and the conductor layer 7 (metal film) are in close contact, and the insulating resin layer 8 is formed by the cured resin layer 2 and the adhesive layers 3 on both sides thereof. Via holes 9 are formed to conduct between the conductor layers 7 (metal films) on both sides at the formation position.

  Next, the printed film B is formed by peeling the release film and leaving the conductor layer 7 (metal film) on the insulating layer 8 side. At this time, since the conductor layer 7 (metal film) has already been subjected to wiring processing, the conductor layer 7 (metal film) is formed as the conductor wiring 7a without performing an additive method or a subtractive method.

  Moreover, the conductor wiring 7a formed in another printed wiring board can also be applied as the conductor layer 7 superimposed on one or both of each adhesive layer 3. In this case, another printed wiring board is formed on the surface of the adhesive layer 3 exposed by peeling off the protective film layer 4 in a state where the conductor wiring 7a is arranged so as to overlap the adhesive layer 3 and is heated and pressed. . At this time, a predetermined position in the conductor layer 7 (conductor wiring 7 a) is overlapped with the conductive paste 6 protruding from the through hole 5. Even during the heat and pressure molding, the adhesive layer 3 and the conductor layer 7 (conductor wiring 7a) are in close contact, and the insulating resin layer 8 is formed by the cured resin layer 2 and the adhesive layers 3 on both sides thereof. A via hole 9 is formed which conducts between the conductor layers 7 (conductor wirings 7a) on both sides at the formation position. Thereby, a multilayer printed wiring board B is formed.

  In addition, an insulating layer and a conductor layer can be further laminated and formed on the printed wiring board B formed as described above to obtain a multilayer printed wiring board B.

  In the printed wiring board B formed in this way, the surface of the insulating material A for printed wiring board in contact with the adhesive layer 3 of the cured resin layer 2 and the surface of the glass cloth 1 in the cured resin layer 2 as described above. Since the dimension (resin thickness W) between them is 10 μm or less, the insulating layer 8 formed by the cured resin layer 2 and the adhesive layer 3 can be formed thin, and for this reason, the insulating layer 8 Thus, the increase in the electrical resistance value of the via hole 9 can be suppressed by preventing an increase in the length of the via hole 9 formed in the first hole, and the conduction reliability in the via hole 9 can be maintained high.

  In addition, when the resin thickness W is 10 μm or less as described above, the proportion of the glass cloth 1 in the insulating layer 8 composed of the glass cloth 1 and the cured thermosetting resin is relatively large. The thermal expansion coefficient of the entire insulating layer 8 is reduced. For this reason, the difference in the thermal expansion coefficient between the conductive paste 6 and the insulating layer 8 in the via hole 9 is reduced, and a load caused by heat during various processes after the via hole 9 is formed or when the printed wiring board B is used. Even when applied, peeling between the via hole 9 and the conductor layer 7 is less likely to occur, and heat resistance reliability is improved.

  Moreover, when the glass transition point when the adhesive layer 3 in the insulating material A for printed wiring boards is heated and cured as described above is higher than the glass transition point of the cured resin layer 2 by 10 ° C. or more, the printed wiring The reliability in the case where a load due to heat is applied to the plate B is further improved. That is, although the cured product of the thermosetting resin composition constituting the adhesive layer 3 has a glass transition point or higher, the thermal expansion coefficient increases rapidly and the thermal expansion coefficient of the entire insulating layer 8 also increases. By increasing the glass transition point when the adhesive layer 3 is heat-cured as described above, the temperature range in which the thermal expansion coefficient of the insulating layer 8 is small can be widened. It is possible to further suppress the occurrence of peeling between the via hole 9 and the conductor layer 7 and improve the heat resistance reliability.

Example 1
Glass cloth 1 (WEA product number 106; thickness 0.038 mm) is impregnated with epoxy resin varnish (epoxy resin varnish used for the production of laminate “R1766” manufactured by Matsushita Electric Works Co., Ltd.) and dried. A 70% prepreg was produced.

  An aluminum clad substrate having a thickness of 0.050 mm was removed after heating and pressurizing at 190 ° C. and 4.0 MPa for 180 minutes in a state where aluminum foils were arranged on both sides of the prepreg. The cured resin layer 2 consisting of was obtained. The resin thickness W on both sides of the cured resin layer 2 at this time was 0.006 mm.

  Next, 80% by weight of bisphenol A brominated epoxy resin methyl ethyl ketone solution (“DER514” manufactured by Dow Chemical Company), o-cresol novolac type epoxy resin methyl ethyl ketone solution (“EPICLON-N-690 manufactured by Dainippon Ink and Chemicals, Inc.) ”) 7% by weight, ethane-type solid epoxy resin (“ EOPN1031 ”manufactured by Japan Epoxy Resin Co., Ltd.) 5% by weight, dicyandiamide (Nihon Carbide Industries Co., Ltd., dimethylformamide 10% solution) 8% by weight A resin composition varnish is prepared and applied to one surface of the cured resin layer 2 with a roll coater to a thickness of 10 μm, followed by drying at 50 ° C. for 60 minutes until tackiness disappears, thereby forming an adhesive layer 3 did. Subsequently, the adhesive layer 3 was also formed on the other surface of the cured resin layer 2 in the same manner.

Next, as the protective film layer 4, a film made of polyethylene terephthalate (“T-60” manufactured by Toray Industries, Inc.) is roll laminated under the conditions of 50 ° C. and 0.49 MPa (5 kgf / cm ² ). It stuck on the surface of the layer 3, and the insulating material A for printed wiring boards was obtained.

  The glass transition temperatures of the insulating layer 8 of the printed wiring board insulating material A and the cured adhesive layer 3 were measured by the TMA method, and were 140 ° C. and 178 ° C., respectively.

(Example 2)
As the cured resin layer 2, the same unclad substrate as in Example 1 was formed.

Next, 20 parts by weight of liquid brominated bisphenol A type epoxy resin (“YDF-8170” manufactured by Toto Kasei Co., Ltd.) and 20 parts by weight of brominated bisphenol A type epoxy resin (“YDB-400” manufactured by Toto Kasei Co., Ltd.) Then, it is dissolved in methyl ethyl ketone as a solvent while stirring, and 20 parts by weight of a phenol novolac type curing agent (“MEH-7500” manufactured by Meiwa Kasei Co., Ltd.) is added thereto to prepare a thermosetting resin composition varnish. Was applied to one surface of the cured resin layer 2 to a thickness of 10 μm, and then dried at 50 ° C. for 60 minutes until tackiness disappeared, whereby the adhesive layer 3 was formed. Next, the adhesive layer 3 was also formed on the other surface of the cured resin layer 2 in the same manner. Next, the protective film layer 4 was adhered to the surface of each adhesive layer 3 in the same manner as in Example 1 to insulate the printed wiring board. Material A was obtained.

  The glass transition temperatures of the insulating layer 8 of the printed wiring board insulating material A and the cured adhesive layer 3 were measured by the TMA method, and were 140 ° C. and 178 ° C., respectively.

(Comparative Example 1)
Glass cloth 1 (WEA product number 106; thickness 0.038 mm) is impregnated with epoxy resin varnish (epoxy resin varnish used for the production of laminate “R1766” manufactured by Matsushita Electric Works Co., Ltd.) and dried. A 70% prepreg was produced.

  An aluminum clad substrate having a thickness of 0.064 mm was removed after heating and pressing for 180 minutes under conditions of 190 ° C. and 3.0 MPa under vacuum with aluminum foil disposed on both sides of the prepreg. The cured resin layer 2 consisting of was obtained. The resin thickness W on both sides of the cured resin layer 2 at this time was 0.013 mm.

  Next, in the same manner as in Example 1, after forming the adhesive layer 3 on both surfaces of the cured resin layer 2, the protective film layer 4 was further adhered to the surface of each adhesive layer 3, and the printed wiring board insulating material A Got.

  When the glass transition temperatures of the insulating layer 8 of this printed wiring board insulating material A and the adhesive layer 3 after curing were measured by the TMA method, they were 140 ° C. and 138 ° C., respectively.

(Manufacture of printed wiring board B)
Using the carbon dioxide laser ("ML605" manufactured by Mitsubishi Electric Corporation), a through-hole 5 having a diameter of 150 µm was formed in the insulating material A for printed wiring board obtained in each of the above examples and comparative examples. The conductive paste 6 (silver-coated copper powder) was printed and filled in the through holes 5 by a squeegee printing method.

  Next, the protective films on both sides are peeled off, and the bumps made of the conductive paste 6 are projected and exposed. In this state, a 18 μm thick copper foil is arranged on each side, and under vacuum using a vacuum press, Heat-press molding was performed at 180 ° C. and 3.0 MPa for 120 minutes.

  Next, after cutting the end face of the substrate, the copper foil on both sides was subjected to wiring processing by sequentially forming a dry film, exposing and developing, and etching with cupric chloride.

  In the thus formed conductor layer 7 (conductor wiring 7a), the electrical resistance value of the portion connected to the via hole 9 was measured, and this was converted into the electrical resistance value per via hole 9.

  Further, the substrate was floated in a solder bath at 260 ° C. for 3 times for 20 seconds to give a thermal load, and the electrical resistance value per via hole 9 was similarly derived.

  These results are as shown in Table 1 below, and in Examples 1 and 2 with respect to Comparative Example 1, the electrical resistance value per via hole 9 is kept low, and the rate of change in resistance when a thermal load is applied. The value was also kept small, and in particular, the resistance change rate value was remarkably suppressed in Example 2.

An example of embodiment of this invention is shown and (a) thru | or (b) is sectional drawing. An example of a prior art is shown, (a) And (b) is sectional drawing.

Explanation of symbols

A Insulating material for printed wiring board B Printed wiring board 1 Glass cloth 2 Cured resin layer 3 Adhesive layer 4 Protective film layer 5 Through hole 6 Conductive paste 7 Conductive layer 8 Insulating layer 9 Via hole

Claims (3)

  Adhesive layers made of a thermosetting resin composition in a B-stage state are laminated on both sides of a cured resin layer obtained by impregnating and curing a thermosetting resin composition on a glass cloth, and a protective film is provided on the outer surface of each adhesive layer. An insulating material for a printed wiring board, wherein a layer is laminated, and a dimension between a surface in contact with the adhesive layer in the cured resin layer and a surface of the glass cloth in the cured resin layer is 10 μm or less.   The insulating material for printed wiring boards according to claim 1, wherein a glass transition point when the adhesive layer is heat-cured is higher by 10 ° C or more than a glass transition point of the cured resin layer. A step of forming a through hole penetrating in the thickness direction in the insulating material for a printed wiring board according to claim 1, a step of filling the through hole with a conductive paste, and peeling off the protective film layer from the adhesive layer And a step of performing heat and pressure molding in a state where a conductor layer is laminated and stacked on the adhesive layer.

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