JP2006261388A - Method of manufacturing printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for efficiently manufacturing a high-quality printed wiring board without deteriorating productivity by reducing variation in temperature in a thermal press in a thermal press process. <P>SOLUTION: An anisotropic thermal conductive sheet 5 (substance having thermal conductivity different in a thickness direction and a surface direction) is arranged between a thermal plate 4 and an SUS plate 3 of the thermal press apparatus. With this configuration, the variation in temperature in the surface of the thermal plate 4 is relieved within the sheet 5 before being transmitted to a laminate 6 to be heated, and the variation in temperature of the laminate 6 is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a printed wiring board used in various electronic devices such as a personal computer, a mobile communication telephone, and a video camera.

  In recent years, as electronic devices have higher performance and higher density, electronic components are increasingly becoming smaller, more integrated, and faster.

  For this reason, the form of printed wiring boards is becoming increasingly denser, multilayered, higher quality, and larger in order to improve productivity.

  A conventional method for hot pressing a printed wiring board will be described below.

  A printed wiring board has a structure in which a conductive metal, generally copper foil, is sandwiched between both ends of an insulating prepreg.

  In order to form this structure, a semi-cured prepreg and copper foil are laminated, and the prepreg is cured by pressurizing and heating, thereby integrating the prepreg and copper foil.

  First, as shown in FIG. 5, a laminate 20 is prepared in the order of copper foil 21, semi-cured prepreg 22, and copper foil 21.

  Next, the SUS board 23 is installed between the laminated bodies 20 in order to make pressurization uniform as shown in FIG. The SUS plate 23, the laminated body 20, and the SUS plate 23 are stacked in a plurality of stages, and this is installed on the hot plate 24 of the hot press apparatus.

  Next, pressurization and heating are performed by the hot platen 24. As a result, a laminated substrate in which the prepreg and the copper foil are integrated is completed.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2003-124603 A

  However, the conventional method for hot pressing a printed wiring board has the following problems.

  Usually, heating to the laminated body in the hot press apparatus is performed by transferring heat from the uppermost and lowermost hot plates 24 to the laminated body.

  Moreover, the heating conditions for the laminate in the hot press apparatus are performed by a program in which the temperature rises to a predetermined rise temperature and is held for a certain period of time at the softening temperature and the curing temperature of the prepreg.

  In particular, since the physical and mechanical characteristics and appearance of the laminated substrate are formed by holding the temperature for a certain period of time, it is important to hold the set temperature.

  However, since the surface area of the hot plate 24 is relatively large, variations in temperature occur in the plane in contact with the SUS plate 23. This temperature variation is transmitted to the SUS plate 23 as it is without being relaxed, and further to the laminated body.

  Therefore, it becomes difficult to maintain the softening temperature, the curing temperature, and the like of the prepreg for a certain period of time. As a result, the physical / mechanical characteristics and appearance of the multilayer substrate are affected, and the maintenance of quality may become unstable.

  In recent years, large-sized laminated substrates have been promoted in order to improve productivity. For this reason, a large-sized hot press apparatus is employed, and accordingly, a hot plate of the hot press apparatus is increased in size and multistage. As a result, the in-plane temperature variation of the hot plate becomes larger and it may become difficult to maintain the quality of the laminated substrate.

  As a measure to solve this, the conventionally adopted method is to install a substance with low thermal conductivity between the hot plate and the SUS plate, and when the heat is transferred from the hot plate to the SUS plate, the in-plane temperature variation It is intended to mitigate.

  However, in the above-described conventional method, although the in-plane temperature variation is slightly relaxed, the speed at which heat is transferred from the hot plate to the SUS plate is reduced, so it is necessary to lengthen the time for heating the laminate. , Productivity decreases.

  The present invention solves the above-mentioned conventional problems, and by installing an anisotropic heat conductive sheet between the hot plate and the SUS plate, the in-plane temperature variation is reduced, and the high quality without reducing the productivity. An object of the present invention is to provide a manufacturing method for efficiently producing a printed wiring board.

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

  According to the first aspect of the present invention, there is provided a step of preparing a laminate composed of at least copper foil and a semi-cured prepreg, and a laminated structure in which the laminate is sandwiched between SUS plates. And a step of pressurizing and heating the laminated body sandwiched between SUS plates by a hot plate of the hot press device, and a difference between the hot plate of the hot press device and the SUS plate. This is a printed wiring board manufacturing method characterized in that an isotropic heat conductive sheet is arranged, and when the substrate is heated by the hot plate in the hot press, the temperature variation in the surface of the hot plate is reduced. Therefore, an anisotropic heat conductive sheet is disposed between the hot plate and the substrate. That is, by interposing an anisotropic heat conductive sheet having different characteristics in the thickness direction and the plane direction and having a greatly different thermal conductivity in the thickness direction and the plane direction between the hot plate of the hot press device and the SUS plate, It has the effect that the temperature variation in the surface of the hot plate is relaxed in the anisotropic heat conductive sheet before it is transmitted to the laminate to be heated. Thereby, the board | substrate as a laminated body is heated uniformly, and it has the effect that it becomes possible to produce the printed wiring board of the stable quality efficiently.

  The invention according to claim 2 of the present invention includes a step of preparing a laminate composed of at least a copper foil and a semi-cured prepreg, and a multilayer structure in which the laminate is sandwiched between SUS plates. And placing the laminate in a hot press device, and pressing and heating the laminate sandwiched between SUS plates by the hot plate of the hot press device, the hot plate of the hot press device and the SUS It is a method for manufacturing a printed wiring board characterized in that an anisotropic heat conductive sheet is arranged between the boards and between the laminated structures, and when heating the substrate with the hot plate in the hot press, In order to reduce temperature variation in the surface of the hot plate, an anisotropic heat conductive sheet is arranged between the hot plate and the substrate and between the laminated structures stacked in a plurality of stages. That is, an anisotropic heat conductive sheet having different characteristics in the thickness direction and in the plane direction and having greatly different thermal conductivity in the thickness direction and in the plane direction is used between the hot plate of the hot press apparatus and the SUS plate and between the laminated structures. By interposing, in the surface of the hot plate, the temperature variation is relaxed in the anisotropic heat conductive sheet before being transmitted to the laminate to be heated. This makes it possible to uniformly heat the substrate as a laminate that is a component of a multi-layered laminated structure that accompanies an increase in the size of a hot press device, and to achieve stable and high-quality printed wiring boards with high productivity. It has the effect that it becomes possible to manufacture while maintaining.

  According to a third aspect of the present invention, in the laminated structure, the laminated body and the SUS plate are alternately stacked in a plurality of stages and are sandwiched between the SUS plates. This is a manufacturing method of printed wiring boards, and the temperature variation in the surface of the hot plate is subject to heating while improving the productivity by heating and pressing a large number of multi-layered laminates in one hot press process. It has the effect | action that it is relieve | moderated in an anisotropic heat conductive sheet before transmitting to the laminated body which becomes.

  This makes it possible to uniformly heat the substrate as a laminate that is a component of a multi-layered laminated structure that accompanies an increase in the size of a hot press device, and to achieve stable and high-quality printed wiring boards with high productivity. It has the effect that it becomes possible to manufacture while maintaining.

  Invention of Claim 4 of this invention is a manufacturing method of the printed wiring board of Claim 1 or 2 characterized by the above-mentioned. At least 2 sets of laminated bodies are clamped by the SUS board, Anisotropy heat conduction before temperature variation in the surface of the hot plate is transmitted to the laminate to be heated, while improving productivity by heating and pressurizing two sets of laminates per stage in a single hot press process It has the effect of relaxing in the sheet.

  As a result, it is possible to uniformly heat the substrate as a laminate that is a component of a laminated structure in which the effective area of the hot press is expanded with the increase in the size of the hot press device, and a stable quality printed wiring board can be obtained. It has the effect that it becomes possible to manufacture while maintaining high productivity efficiently.

  According to a fifth aspect of the present invention, the laminate includes a core substrate having a circuit between prepregs in a semi-cured state. The method for producing a printed wiring board according to the first or second aspect, Thus, heating to the multilayer structure having a multilayer structure is made uniform, interlayer adhesion of the multilayer substrate is stabilized, and a multilayer printed wiring board having excellent quality can be produced.

  According to a sixth aspect of the present invention, in the printed wiring board according to the first aspect, the anisotropic thermal conductive sheet has a property that the thermal conductivity is different between the thickness direction and the plane direction. Due to this characteristic, the temperature variation in the plane of the hot plate is relaxed in the anisotropic heat conductive sheet before being transmitted to the substrate to be heated, and the laminate can be heated uniformly. it can.

  The invention according to claim 7 of the present invention is the printed wiring board according to claim 1, wherein the anisotropic heat conductive sheet is a graphite sheet having high orientation obtained from a carbon-based material. In the manufacturing method, the temperature variation in the surface of the hot plate is relaxed in the anisotropic heat conductive sheet before it is transmitted to the substrate to be heated, and the laminate can be heated uniformly.

  In addition, since it is composed of carbon-based materials, it has excellent heat resistance and stable anisotropic heat conductive sheet even at the highest temperature (200-300 ° C) reached in the hot press process. Can be used repeatedly.

  The invention according to claim 8 of the present invention is characterized in that the thermal conductivity in the plane direction of the anisotropic thermal conductive sheet is larger than the thermal conductivity in the thickness direction. Due to this characteristic, the temperature variation in the plane of the hot plate is relaxed in the anisotropic heat conductive sheet before being transmitted to the substrate to be heated, and the laminate can be heated uniformly. it can. Further, since the thermal conductivity in the plane direction is larger than the thermal conductivity in the thickness direction, it is possible to efficiently produce a printed wiring board with stable quality.

  The invention according to claim 9 of the present invention is characterized in that the thermal conductivity in the plane direction of the anisotropic thermal conductive sheet is 100 times or more the thermal conductivity in the thickness direction. This is a method of manufacturing a wiring board, and due to this characteristic, temperature variations in the surface of the hot plate are alleviated in the anisotropic heat conductive sheet before being transmitted to the substrate to be heated, and the laminate is heated uniformly. be able to. Furthermore, since the thermal conductivity in the plane direction is more than 100 times the thermal conductivity in the thickness direction, stable quality printed wiring boards can be efficiently produced without reducing temperature variations in the plane direction and reducing productivity. It becomes possible to produce.

  In the invention according to claim 10 of the present invention, the thermal conductivity in the thickness direction of the anisotropic thermal conductive sheet is in the range of 1 to 10 W / m · K, and the thermal conductivity in the plane direction is 500 to 1000 W / m. The printed wiring board manufacturing method according to claim 9, wherein the printed wiring board manufacturing method according to claim 9, wherein an anisotropic heat conductive sheet having a thermal conductivity in the above range is employed, and the surface direction Accordingly, it is possible to efficiently produce a printed wiring board having a stable quality without reducing the temperature variation and reducing the productivity.

  Invention of Claim 11 of this invention is a manufacturing method of the printed wiring board of Claim 1 characterized by the anisotropic heat conductive sheet being provided with flexibility, Thereby, In the pressurization performed simultaneously with the heating, local pressure concentration can be prevented, and a stable quality printed wiring board can be efficiently produced.

  Invention of Claim 12 of this invention is the manufacturing method of the printed wiring board of Claim 1 characterized by the heat-resistant temperature of an anisotropic heat conductive sheet being 400 degreeC or more, By this, An anisotropic heat conductive sheet can be used even at the maximum temperature (200 to 300 ° C.) reached in the hot press step.

  The invention according to claim 13 of the present invention is the method for producing a printed wiring board according to claim 1, characterized in that the appearance, dimensions, and characteristics of the anisotropic heat conductive sheet do not change from room temperature to 1000 ° C. However, the number of times of repeated use can be increased by selecting a material whose appearance, dimensions, and characteristics do not change up to 1000 ° C. As a result, the production cost can be reduced.

  According to the fourteenth aspect of the present invention, the anisotropic heat conductive sheet is made of iron (Fe), aluminum (Al), calcium (Ca), magnesium (Mg), potassium (K), or sodium (Na). The method for producing a printed wiring board according to claim 1, wherein the content is 1 ppm or less, thereby minimizing the adhesion of impurities to the substrate in the hot press process, Stable quality printed wiring boards can be efficiently produced.

  The invention according to claim 15 of the present invention is the production of a printed wiring board according to claim 1, wherein the anisotropic heat conductive sheet has a chlorine (Cl) content of 0.1 ppm or less. In this method, it is possible to prevent the copper foil of the substrate and the corrosion of the equipment due to chlorine (Cl), and to efficiently produce a printed wiring board having a stable quality.

  According to the present invention, the temperature variation in the surface of the hot plate in the hot press is alleviated before being transmitted to the substrate to be heated.

  Further, it is possible to prevent deterioration of the substrate characteristics due to impurities without reducing productivity. As a result, it is possible to efficiently produce a printed wiring board with stable quality.

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

  FIG. 1 is a schematic view showing a method for manufacturing a printed wiring board according to Embodiment 1 of the present invention. In FIG. 1, 1 is copper foil (515 mm × 345 mm, thickness 18 μm), 2 is a semi-cured prepreg (510 mm × 340 mm, thickness 80 μm), 3 is a SUS plate (550 mm × 770 mm, thickness 1 mm), 4 is heat The hot plate 5 of the pressing device is an anisotropic heat conductive sheet (550 mm × 770 mm, thickness 100 μm).

  Examples of the material of the anisotropic heat conductive sheet 5 include a graphite sheet (graphite sheet) having high orientation obtained by high-temperature treatment of a polyimide film.

  The anisotropic thermal conductive material constituting the anisotropic thermal conductive sheet 5 has a property that the thermal conductivity is different between the thickness direction and the plane direction shown in FIG.

  In particular, it is preferable that the thermal conductivity of the anisotropic thermal conductive sheet 5 is greatly different between the thickness direction and the plane direction, and the plane direction thermal conductivity is significantly larger than the thermal conductivity in the thickness direction. That is, the thermal conductivity in the plane direction is desirably in the range of 50 to 1000 times the thermal conductivity in the thickness direction. The specific range of thermal conductivity is more preferably 1 to 10 W / m · K in the thickness direction and 500 to 1000 W / m · K in the plane direction from the viewpoint of productivity.

  In addition, by setting the thermal conductivity in the thickness direction to an appropriate range of 1 to 10 W / m · K, it is easy to realize a uniform temperature distribution without reducing productivity.

  When it is 1 W / m · K or less, the productivity is low, and when it is 10 W / m · K or more, it is easily affected by temperature variations of the hot plate of the hot press apparatus.

  With the above configuration, the temperature variation in the surface of the hot plate of the hot press apparatus is alleviated by having a uniform temperature distribution in the surface direction of the anisotropic heat conductive sheet 5 before being transmitted to the substrate to be heated. This causes the substrate to be heated uniformly throughout. Further, this configuration makes it possible to efficiently produce a stable quality printed wiring board.

  The anisotropic thermal conductive sheet 5 in the present embodiment is a sheet having a thermal conductivity in the thickness direction of 5 W / m · K and a thermal conductivity in the plane direction of 700 W / m · K.

  Moreover, it is desirable that the anisotropic heat conductive sheet 5 has flexibility and flexibility. Thereby, local pressure concentration can be prevented in pressurization performed simultaneously with heating.

  The anisotropic heat conductive sheet 5 preferably has a heat resistant temperature of 400 ° C. or higher. Thereby, even at the maximum temperature (200 to 300 ° C.) reached in the hot press step, the anisotropic substance maintains a stable appearance, dimensions, and characteristics, and can be used repeatedly.

  In particular, the anisotropic thermal conductive sheet 5 is used repeatedly by adopting a polyimide film obtained by high-temperature treatment at 1000 ° C. or higher, so that its appearance, dimensions, and characteristics do not change up to 1000 ° C. be able to.

  These characteristics / performances can be realized by selecting from anisotropic carbon sheet materials composed mainly of carbon.

  By using the anisotropic heat conductive sheet having the above configuration for the production of a printed wiring board, it is possible to efficiently produce a printed wiring board having a stable quality, and to reduce the production cost.

  The anisotropic heat conductive material constituting the anisotropic heat conductive sheet 5 includes iron (Fe), aluminum (Al), calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na). It is desirable that it is 1 ppm or less. With this configuration, it is possible to minimize the adhesion of impurities to the substrate in the hot press process.

  Furthermore, it is desirable that chlorine (Cl) in the anisotropic thermal conductive material is 0.1 ppm or less. Chlorine (Cl) has a large corrosive action on metals. For this reason, the copper foil on the substrate and the corrosion of the hot press apparatus can be prevented.

  A method for manufacturing a printed wiring board using the anisotropic heat conductive sheet 5 having the above configuration will be described below.

  First, the laminated body 6 is prepared in the order of copper foil 1, semi-cured prepreg 2, and copper foil 1. In addition, the laminated body 6 can also be made into a multilayer laminated body by inserting the core board | substrate which has a circuit between the prepregs of a semi-hardened state, and pressurizing and heating.

  Next, as shown in FIG. 1, a laminated structure 7 having a form in which the outermost layer is sandwiched between the SUS plates 3 in a plurality of stages in the order of the SUS plate 3, the laminated body 6, and the SUS plate 3 is prepared. It mounts on the anisotropic heat conductive sheet 5 mounted on the hot platen 4 of a press apparatus. Unlike the procedure for preparing the laminated structure 7 outside the hot press apparatus as described above, the SUS plate 3 is placed on the anisotropic heat conductive sheet 5 and the order of the laminated body 6 and the SUS plate 3 is set. Thus, it is also possible to form a stacked structure 7 that is directly stacked in a plurality of stages in the hot press apparatus.

  Next, the anisotropic heat conductive sheet 5 is also arranged between the uppermost SUS plate 3 and the hot plate 4 stacked in a plurality of stages, and this is heated and pressed by a hot press device.

The heating conditions are an intermediate holding temperature of 100 ° C. and a holding time of 60 minutes in a vacuum, a maximum temperature of 250 ° C. and a holding time of 60 minutes, a heating rate of 0.5 to 3.0 ° C./min, and a pressing condition of 20 Performed at ˜40 kg / cm ² .

  In the conventional manufacturing method, the temperature variation of the laminate during heating was 10 to 15 ° C., but in the manufacturing method according to the present invention, the temperature variation in the substrate during heating was reduced to 3 ° C. or less.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is a schematic diagram showing a method for manufacturing a printed wiring board according to Embodiment 2 of the present invention. For the reference numerals in the figure, copper foil 1, semi-cured prepreg 2, SUS plate 3, hot plate 4 of hot press apparatus, anisotropic heat conductive sheets 5, 5a, and laminate 6 are shown, and the dimensions and configuration are shown. Is the same as in the first embodiment.

  As shown in FIG. 3, two sets of the SUS plate 3 and the laminated body 6 are stacked in a plurality of stages in the order of the SUS plate 3, and laminated structures 7 a and 7 b in a form in which the outermost layer is sandwiched between the SUS plates 3 are prepared.

  The laminated structure 7a is placed on the anisotropic heat conductive sheet 5 placed on the hot plate 4 of the hot press device, and the anisotropic heat conductive sheet 5a is placed on the laminated structure 7a. The laminated structure 7b is piled up on it.

  In this manner, the anisotropic heat conductive sheet 5 is also disposed between the uppermost SUS plate 3 and the heat plate 4 of the laminated structure stacked in a plurality of stages.

  In the present embodiment, the anisotropic heat conductive sheet 5a is also arranged between the laminated structures 7a and 7b. Even if the laminated structure has a multi-stage structure accompanying an increase in the size of the heat press apparatus, the laminated body is used. 6 is intended to reduce the temperature variation heated.

The above laminated structure is heated and pressurized with a hot press apparatus. The heating conditions are an intermediate holding temperature of 100 ° C. and a holding time of 60 minutes in a vacuum, a maximum temperature of 250 ° C. and a holding time of 60 minutes, a heating rate of 0.5 to 3.0 ° C./min, and a pressing condition of 20 Performed at ˜40 kg / cm ² .

  In the case where two sets of the laminates 6 are installed side by side in the conventional manufacturing method, the temperature variation in the substrate during heating was 15 to 20 ° C., but in the manufacturing method according to the present invention, the temperature variation in the substrate during heating is The temperature was reduced to 5 ° C. or lower.

  In addition, in this Embodiment, although the example which installed two sets of laminated bodies 6 side by side was shown, the laminated body 6 is made into 1 set as shown in FIG. It is also possible to adopt a configuration in which It was confirmed that the temperature variation of the laminate during heating in this case was better than the effect in the first embodiment of the present invention.

  As mentioned above, this invention provides the manufacturing method characterized by installing an anisotropic heat conductive sheet in the hot press process of the manufacturing process of a printed wiring board.

  With this configuration, the in-plane temperature variation of the substrate in the hot press can be reduced, and a printed wiring board can be produced without reducing productivity.

  As a conclusion, the present invention can provide a method for producing a printed wiring board capable of efficiently producing a printed wiring board having stable quality, and can be said to have great industrial applicability.

Schematic which shows the manufacturing method of the printed wiring board in Embodiment 1 of this invention. Schematic which shows the anisotropic heat conductive sheet in Embodiment 1 of this invention. Schematic which shows the manufacturing method of the printed wiring board in Embodiment 2 of this invention. Schematic which shows the manufacturing method of the printed wiring board in Embodiment 2 of this invention. Schematic showing a conventional printed wiring board manufacturing method Schematic showing a conventional printed wiring board manufacturing method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copper foil 2 Semi-hardened prepreg 3 SUS board 4 Hot plate of a hot press apparatus 5, 5a Anisotropic heat conductive sheet 6 Laminated body 7, 7a, 7b Laminated structure

Claims (15)

Preparing a laminate composed of at least copper foil and a semi-cured prepreg;
Placing the laminated structure in which the laminate is sandwiched between SUS plates in a hot press apparatus;
A step of pressing and heating the laminate sandwiched between SUS plates by a hot plate of the hot press device,
A method for manufacturing a printed wiring board, wherein an anisotropic heat conductive sheet is disposed between a hot plate of the hot press device and the SUS plate. Preparing a laminate composed of at least copper foil and a semi-cured prepreg;
A step of stacking a plurality of laminated structures sandwiching the laminated body with SUS plates and placing them in a hot press apparatus;
A step of pressing and heating the laminate sandwiched between SUS plates by a hot plate of the hot press device,
A method for producing a printed wiring board, wherein an anisotropic heat conductive sheet is disposed between a hot plate of the hot press device and the SUS plate and between the laminated structures. The method for producing a printed wiring board according to claim 1 or 2, wherein the laminated structure is formed by alternately stacking laminated bodies and SUS boards in a plurality of stages and sandwiching them by SUS boards. The method for manufacturing a printed wiring board according to claim 1, wherein at least two sets of laminates are sandwiched between SUS boards. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein the laminate includes a core substrate having a circuit between prepregs in a semi-cured state. The method for producing a printed wiring board according to claim 1, wherein the anisotropic heat conductive sheet has a property that the thermal conductivity is different between the thickness direction and the surface direction. The method for producing a printed wiring board according to claim 1, wherein the anisotropic heat conductive sheet is a graphite sheet having high orientation obtained from a carbon-based material. The method for manufacturing a printed wiring board according to claim 6, wherein the thermal conductivity in the plane direction of the anisotropic thermal conductive sheet is larger than the thermal conductivity in the thickness direction. The method for producing a printed wiring board according to claim 8, wherein the thermal conductivity in the plane direction of the anisotropic thermal conductive sheet is 100 times or more the thermal conductivity in the thickness direction. The thickness direction thermal conductivity of the anisotropic thermal conductive sheet is in the range of 1 to 10 W / m · K, and the planar thermal conductivity is in the range of 500 to 1000 W / m · K. Item 10. A method for producing a printed wiring board according to Item 9. The method for manufacturing a printed wiring board according to claim 1, wherein the anisotropic heat conductive sheet has flexibility. The method for producing a printed wiring board according to claim 1, wherein the heat resistant temperature of the anisotropic heat conductive sheet is 400 ° C. or higher. The method for producing a printed wiring board according to claim 1, wherein the anisotropic heat conductive sheet does not change in appearance, size, and characteristics from room temperature to 1000 ° C. The anisotropic heat conductive sheet is characterized in that the content of iron (Fe), aluminum (Al), calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) is 1 ppm or less. The manufacturing method of the printed wiring board of Claim 1. The method for manufacturing a printed wiring board according to claim 1, wherein the anisotropic heat conductive sheet has a chlorine (Cl) content of 0.1 ppm or less.

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