JP2010161168A - Printed board and method for manufacturing printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed board and a method for manufacturing the printed board which stabilizes the operation of a packaging component when the packaging component is packaged. <P>SOLUTION: This flexible printed board 10 includes an insulating substrate 11, an hBN layer 12, and a pattern 13. The hBN layer 12 is formed on the insulating substrate 11, and has a surface 12a. The pattern 13 is formed on the surface 12a of the hBN layer 12, and is conductive. The hBN layer 12 has orientation having a c axis parallel to a normal of the surface 12a of the hBN layer 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printed circuit board and a printed circuit board manufacturing method, and more particularly to a printed circuit board used as a wiring material and a printed circuit board manufacturing method.

  Printed circuit boards such as flexible printed circuit boards (FPCs) are widely used for their flexibility. Such a flexible printed circuit board is disclosed in, for example, JP-A-6-296073 (Patent Document 1). The flexible printed circuit board disclosed in Patent Document 1 is a flexible substrate formed of a resin, a printed circuit of a copper (Cu) conductor formed on the substrate, and laser reflection on one upper surface and one upper surface of the printed circuit. And metal plating with a rate of 75% or less.

JP-A-6-296073

  There is a technique for mounting electronic components on a printed circuit of a flexible printed circuit board disclosed in Patent Document 1. However, recent advances in mounting technology have significantly increased the amount of heat generated by electronic components mounted on a flexible printed circuit board. For this reason, in the flexible printed circuit board of the said patent document 1, it is difficult to escape the heat which arose from the electronic component. Therefore, the electronic component cannot be stably operated.

  In addition, a technique is considered in which a heat radiating sheet is bonded so as to contact an electronic component that generates heat, and heat is released into the sheet surface. However, there are restrictions on the arrangement of the heat dissipation sheet and the heat dissipation is not sufficient. For this reason, it was not sufficient to operate the electronic component stably.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-described problems, and provides a printed circuit board and a printed circuit board manufacturing method that stabilize the operation of the mounted component when the mounted component is mounted. It is to be.

  The printed circuit board of the present invention includes an insulating substrate, a hexagonal boron nitride (BN) layer (hBN layer), and a pattern. The hBN layer is formed on an insulating substrate and has a surface. The pattern is formed on the surface of the hBN layer and is conductive. The hBN layer is oriented with a c-axis parallel to the normal to the surface of the hBN layer.

  According to the printed board of the present invention, the orientation hBN layer having the c-axis parallel to the surface normal is provided between the insulating substrate and the pattern. Since the hBN layer is insulative, it does not hinder non-energization between the insulative substrate and the pattern.

  In addition, since oriented hBN has a crystal structure in which six-membered rings composed of B and N are regularly arranged in the ab plane, the thermal conductivity in the ab plane direction is high in the oriented hBN layer. Since the hBN layer has a c-axis parallel to the surface normal, the direction parallel to the surface of the hBN layer is the ab plane direction. For this reason, in the hBN layer, the thermal conductivity in the direction parallel to the surface can be increased. Therefore, when the mounting component is mounted on the pattern, the heat generated from the mounting component in the direction parallel to the surface of the hBN layer can be released. Therefore, when the mounting component is mounted, the operation of the mounting component can be stabilized.

  Preferably, in the printed board, the insulating substrate is a resin and the pattern is copper (Cu). Thereby, a printed circuit board with good characteristics can be realized.

  In the printed circuit board, preferably, the hBN layer has a thickness of 3 μm or more and 10 μm or less.

  In the case of 3 μm or more, the heat dissipation effect of the hBN layer can be further enhanced. In the case of 10 μm or less, peeling between the hBN layer and the pattern can be suppressed.

  Preferably, the printed circuit board further includes an amorphous BN layer formed between the hBN layer and the pattern.

  Since the crystals of the amorphous BN layer are not oriented in a specific direction, the thermal expansion coefficient of the amorphous BN layer is larger than the thermal expansion coefficient of the hBN layer. When the thermal expansion coefficient of the pattern is larger than that of the hBN layer, the difference in the thermal expansion coefficient between the hBN layer and the pattern can be reduced by the amorphous BN layer. For this reason, since the thermal stress produced by the difference of the thermal expansion coefficient of a pattern and an hBN layer can be reduced, it can suppress that a pattern and an hBN layer peel.

  In the printed circuit board, preferably, the amorphous BN layer has a thickness of 3 μm to 15 μm.

  In the case of 3 μm or more, peeling between the hBN layer and the pattern can be effectively suppressed. In the case of 15 μm or less, it is possible to suppress a decrease in heat dissipation effect due to the amorphous BN layer.

  The printed circuit board manufacturing method according to one aspect of the present invention includes the following steps. A conductive substrate to be a pattern is prepared. An amorphous BN layer having a surface is formed over a conductive substrate. By bringing the surface of the amorphous BN layer into contact with gallium (Ga) gas, an oriented hBN layer having a c-axis parallel to the surface normal is formed. The hBN layer and the insulating substrate are bonded together.

  The inventor of the present invention rearranges the B element and the N element in the amorphous BN layer by bringing Ga gas into contact with the amorphous BN layer, and regularly aligns the six-membered ring of the B element and the N element. Has been found to form a functional hBN layer. For this reason, according to the printed circuit board manufacturing method in one aspect of the present invention, since the amorphous BN layer is brought into contact with the Ga gas, the surface is formed between the insulating substrate and the conductive substrate to be patterned. An oriented hBN layer having a c-axis parallel to the normal line can be formed. As described above, the hBN layer achieves both insulation and heat dissipation. Therefore, when the mounting component is mounted on the pattern, the heat generated from the mounting component in the direction parallel to the surface of the hBN layer can be released. Therefore, when the mounting component is mounted, the operation of the mounting component can be stabilized.

  A printed circuit board manufacturing method according to another aspect of the present invention includes the following steps. A conductive substrate to be a pattern is prepared. By supplying a gas containing B element, a gas containing N element, and Ga gas onto a conductive substrate, oriented hBN having a c-axis parallel to the surface normal is formed. The hBN layer insulating substrate is bonded together.

  The present inventor forms an amorphous BN layer when a gas containing N element and a gas containing B element are not supplied together with Ga gas, but the gas containing N element and the gas containing B element are It has been found that an oriented hBN layer can be formed when supplied with Ga gas. For this reason, according to the method for manufacturing a printed circuit board in another aspect of the present invention, an orientation having a c-axis parallel to the surface normal line between the insulating substrate and the conductive substrate to be a pattern. An hBN layer can be formed. As described above, the hBN layer achieves both insulation and heat dissipation. Therefore, when the mounting component is mounted on the pattern, the heat generated from the mounting component in the direction parallel to the surface of the hBN layer can be released. Therefore, when the mounting component is mounted, the operation of the mounting component can be stabilized.

In the method for manufacturing a printed circuit board according to the other aspect described above, preferably, in the step of forming the hBN layer, at least one of nitrogen gas (N ₂ ) and ammonia gas (NH ₃ ) is used as the gas containing N element. Thereby, an oriented hBN layer can be easily formed.

  Preferably, in the printed circuit board manufacturing method according to the other aspect described above, by supplying a gas containing B element and a gas containing N element onto the conductive substrate, the hBN layer and the conductive substrate are interposed. The method further includes the step of forming an amorphous BN layer.

  Thereby, when the difference between the thermal expansion coefficient of the conductive substrate used as a pattern and the thermal expansion coefficient of the hBN layer is large, the difference in the thermal expansion coefficient can be reduced by the amorphous BN layer. For this reason, peeling due to thermal stress between the conductive substrate and the hBN layer can be suppressed.

  Preferably, in the method for manufacturing a printed circuit board according to the above and the other aspects, in the step of preparing the conductive substrate, a Cu substrate is used as the conductive substrate, and in the step of bonding the insulating substrate, the insulating substrate is used. A resin sheet is used. Thereby, a printed circuit board with good characteristics can be manufactured.

  Preferably, in the method for manufacturing a printed circuit board according to the above and other aspects, the step of forming the hBN layer is performed at a temperature of 600 ° C. or higher and 800 ° C. or lower.

  Thereby, since Ga gas can be supplied easily, an oriented hBN layer can be easily formed.

  Preferably, in the method for manufacturing a printed circuit board according to the one and other aspects, plasma is applied in the step of forming the hBN layer. Thereby, the temperature for generating Ga gas can be lowered. For this reason, the temperature range for cooling the conductive substrate and the hBN layer can be narrowed after the step of forming the hBN layer. For this reason, peeling due to thermal stress due to a difference in thermal expansion coefficient between the hBN layer and the conductive substrate can be suppressed.

  Preferably, in the method for manufacturing a printed circuit board according to the first and other aspects, the step of preparing the conductive substrate includes a step of forming a recess on the surface of the conductive substrate.

  Thereby, the hBN layer or the amorphous BN layer formed in the recess serves as an anchor, and the adhesion between the hBN layer and the conductive substrate can be improved. For this reason, peeling with a pattern and an hBN layer can be suppressed more.

  According to the printed circuit board and the printed circuit board manufacturing method of the present invention, the orientation hBN layer that achieves both insulation and heat dissipation is formed, so that the operation of the mounted component is stable when the mounted component is mounted. It can be made.

It is a perspective view which shows schematically the flexible printed circuit board in Embodiment 1 of this invention. It is a flowchart which shows the manufacturing method of the flexible printed circuit board in Embodiment 1 of this invention. It is a perspective view which shows roughly the electroconductive board | substrate used as the pattern in Embodiment 1 of this invention. It is a perspective view which shows roughly the state in which the amorphous BN layer in Embodiment 1 of this invention was formed. It is a figure which shows typically the crystal structure of the amorphous BN layer in Embodiment 1 of this invention. It is sectional drawing which shows schematically the state in which the hBN layer in Embodiment 1 of this invention was formed. It is a figure which shows typically the crystal structure of the hBN layer in Embodiment 1 of this invention. It is a perspective view which shows roughly the insulating board | substrate in Embodiment 1 of this invention. It is a perspective view which shows roughly the state which bonded the insulating board | substrate in Embodiment 1 of this invention. It is sectional drawing for demonstrating the heat flow of the flexible printed circuit board in Embodiment 1 of this invention. It is sectional drawing which shows the conventional flexible printed circuit board roughly. It is a perspective view which shows schematically the flexible printed circuit board in Embodiment 3 of this invention. It is a perspective view which shows roughly the state in which the amorphous BN layer in Embodiment 3 of this invention was formed. It is a perspective view which shows roughly the state which bonded the board | substrate in Embodiment 3 of this invention. FIG. 3 is a cross-sectional view schematically showing a generation apparatus for forming an hBN layer in Example 1. It is a side view which shows roughly the sample for measuring the thermal conductivity of the flexible printed circuit board of the example 1 and 2 of this invention. It is a side view which shows roughly the sample for measuring the heat conductivity of the flexible printed circuit board of the comparative example 1. 1 is a measuring device for measuring thermal conductivity in Example 1. FIG. 6 is a cross-sectional view schematically showing a generation apparatus for forming an hBN layer in Example 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a perspective view schematically showing a flexible printed circuit board according to an embodiment of the present invention. With reference to FIG. 1, the flexible printed circuit board 10 which is an example of the printed circuit board in this Embodiment is demonstrated.

  The flexible printed circuit board 10 includes an insulating substrate 11, an hBN layer 12, a pattern 13, a mounting component 14, and a wire 15. The hBN layer 12 is formed on the substrate 11 and has a surface 12a. The pattern 13 is formed on the surface 12 a of the hBN layer 12. The mounting component 14 is formed on the pattern 13. The wire 15 electrically connects the pattern 13 and the mounting component 14.

  The substrate 11 is not particularly limited as long as it is insulating. For example, a resin such as polyimide can be used.

  The hBN layer 12 is insulative and has an orientation having a c-axis parallel to the normal line of the surface 12a. In the hBN layer 12, a six-membered ring formed by covalent bonding with B atoms and N atoms alternately arranged in an ab plane (a plane parallel to the surface 12a) is regularly arranged. The hBN layer 12 has a plate-like structure in which six-membered rings are two-dimensionally connected and a layered structure in which the plate-like structures are stacked by VanderWaals (van der Waals) bonding. For this reason, the thermal conductivity in the direction parallel to the surface 12a of the hBN layer 12 is as high as 600 W / mK or more and 700 W / mK or less.

  The hBN layer 12 preferably has a thickness of 3 μm or more and 10 μm or less. In the case of 3 μm or more, the heat dissipation effect of the hBN layer 12 can be further enhanced. In the case of 10 μm or less, peeling between the hBN layer 12 and the pattern 13 can be suppressed.

  The hBN layer 12 may be formed so as to cover the entire surface of the substrate 11 as shown in FIG. 1 or may be formed only under the pattern 13.

  The pattern 13 is conductive, and for example, a metal thin film such as Cu can be used.

  The mounting component 14 is an electronic component such as a semiconductor. The mounting component 14 is not particularly limited, and a desired number of arbitrary components are arranged in a desired portion. The wire 15 is a conductive member. The mounting component 14 and the wire 15 may be omitted.

  FIG. 2 is a flowchart showing a method for manufacturing a flexible printed board in the present embodiment. Then, with reference to FIG. 2, the manufacturing method of the flexible printed circuit board in this Embodiment is demonstrated.

  FIG. 3 is a perspective view schematically showing a conductive substrate serving as a pattern in the present embodiment. As shown in FIGS. 2 and 3, first, a conductive substrate 16 to be a pattern is prepared (step S1). The substrate 16 has a surface 16a. For example, a Cu substrate is prepared as the substrate 16.

  In this step S <b> 1, it is preferable to form a recess in the surface 16 a of the conductive substrate 16. The surface 16a is a surface on which the amorphous BN layer 17 is formed in step S2 described later. The method for forming the concave portion is not particularly limited, and for example, the concave portion can be formed by a method of pressing a mold having fine protrusions on the surface, such as nanoimprint.

  FIG. 4 is a perspective view schematically showing a state in which an amorphous BN layer is formed in the present embodiment. Next, as shown in FIGS. 2 and 4, an amorphous BN layer 17 having a surface 17a is formed on the surface 16a of the conductive substrate 16 (step S2). The surface 17a is a surface opposite to the surface in contact with the substrate 16.

  The method for forming the amorphous BN layer 17 is not particularly limited, and a CVD (Chemical Vapor Deposition) method, a PVD (Physical Vapor Deposition) method, or the like can be employed. When a BN layer is formed on a substrate 16 having a low melting point such as Cu by a vapor phase method such as a normal CVD method or a PVD method, it becomes amorphous.

  FIG. 5 is a diagram schematically showing the crystal structure of the amorphous BN layer 17 in the present embodiment. As shown in FIG. 5, the crystal structure of the amorphous BN layer 17 is not oriented in a specific direction.

  When a recess is formed in the surface 16a of the substrate 16 in step S1, the amorphous BN layer 17 is also formed in the recess.

  FIG. 6 is a cross-sectional view schematically showing a state in which the hBN layer is formed in the present embodiment. FIG. 7 is a diagram schematically showing the crystal structure of the hBN layer 17 in the present embodiment. Next, as shown in FIGS. 2, 6 and 7, the surface 17 a of the amorphous BN layer 17 is brought into contact with Ga gas (Ga vapor), whereby the orientation having a c-axis parallel to the normal of the surface 12 a is achieved. The hBN layer 12 is formed (step S3).

  By reacting the amorphous BN layer 17 with Ga gas in this step S3, the B atoms and N atoms in the amorphous BN layer 17 begin to rearrange, and as shown in FIG. It converts into oriented hBN in which the member rings are regularly arranged. Therefore, the hBN layer 12 is generated from the front surface 17a to the back surface of the amorphous BN layer 17. In the present embodiment, the surface 17a of the amorphous BN layer 17 is generated on the back surface 12b of the hBN layer 12, and the back surface of the amorphous BN layer is generated on the surface 12a of the hBN layer 12.

  In this step S3, Ga gas is preferably supplied at a temperature of 600 ° C. or higher and 800 ° C. or lower. The amorphous BN layer 17 can be converted to the hBN layer 12 by Ga gas in this temperature range. Further, it is preferable to apply plasma. In this case, the amorphous BN layer 17 can be converted to the hBN layer 12 by Ga gas at about 400 ° C. For this reason, the hBN layer 12 can be formed at a low temperature. In this case, after forming the hBN layer 12, the temperature range for cooling the substrate 16 and the hBN layer 12 can be narrowed. For this reason, peeling due to thermal stress due to the difference in thermal expansion coefficient between the hBN layer 12 and the substrate 16 can be suppressed.

  Here, a Ga gas supply method will be described. For example, the liquid Ga and the amorphous BN layer 17 formed on the substrate 16 are placed in a vacuum furnace and heated in this state, whereby the liquid Ga is vaporized and Ga gas can be generated. The reason why the vacuum is maintained is to activate the generation of Ga gas from the liquid Ga at a low temperature. However, the supply method of Ga gas is not particularly limited, and the interior of the furnace does not have to be kept in a vacuum when heated to a high temperature or when Ga gas is separately introduced.

  Moreover, in this step S3, it is preferable to form the hBN layer 12 having a thickness of 3 μm or more and 10 μm or less. In the case of 3 μm or more, the heat dissipation effect of the hBN layer 12 can be further enhanced. When the thickness is 10 μm or less, peeling between the hBN layer 12 and the substrate 16 can be suppressed.

  Further, when a recess is formed in the surface 16a of the substrate 16 in step S1, an amorphous BN layer 17 formed in the recess is generated in the hBN layer 12. In this case, the adhesion effect of the hBN layer 12 to the substrate 16 increases due to the anchor effect, and it becomes difficult to peel off.

  FIG. 8 is a perspective view schematically showing an insulating substrate in the present embodiment. Next, as shown in FIG. 8, an insulating substrate 11 is prepared. Although the board | substrate 11 will not be specifically limited if it is insulating, For example, a resin sheet etc. can be used.

  FIG. 9 is a perspective view schematically showing a state in which an insulating substrate in the present embodiment is bonded. Next, as shown in FIGS. 2 and 9, the hBN layer 12 and the insulating substrate 11 are bonded together (step S4). In the present embodiment, the back surface 12b of the hBN layer 12 and the substrate 11 are bonded together. The method of bonding is not particularly limited, and a generally known method such as using an adhesive can be employed.

  Next, a part of the substrate 16 is removed to form the pattern 13 (step S5). Etching or the like is performed so that the pattern 13 becomes a desired circuit pattern. In step S3, only the substrate 16 may be etched, or the substrate 16 and the hBN layer 12 may be etched.

  The flexible printed circuit board 10 shown in FIG. 1 can be manufactured by performing the above steps S1 to S5.

  Note that the mounting component 14 is mounted on the pattern 13 using an adhesive such as solder as necessary. Moreover, the pattern 13 and the mounting component 14 are connected using the wire 15 as needed.

  Moreover, although the flexible printed circuit board 10 of this Embodiment is made into the single-sided board which has the pattern 13 only on one surface of the insulating board | substrate 11, it is not limited to this in particular. The flexible printed circuit board 10 of the present invention may be, for example, a double-sided board having a pattern 13 on the front and back surfaces of an insulating substrate 11. Further, it may be a multilayer board in which an insulating substrate 11, an hBN layer 12, and a pattern 13 are stacked. In this case, the hBN layer 12 may be formed in at least one layer between the insulating substrate 11 and the pattern 13, but the hBN layer 12 is formed between the insulating substrate 11 and the pattern 13. And it is preferable because the heat dissipation can be greatly improved.

  In addition, a single-sided board means what has a pattern (circuit) only in one side of a flexible printed circuit board. A double-sided board means what has a pattern (circuit) on both surfaces of a flexible printed circuit board. A multilayer board means what laminated | stacked the insulator and the pattern (circuit) on the wafer form.

  Then, the effect of the flexible printed circuit board 10 in this Embodiment is demonstrated.

  FIG. 10 is a cross-sectional view for explaining the heat flow of the flexible printed circuit board in the present embodiment. The heat generated from the mounting component 14 in the flexible printed board 10 in the present embodiment is diffused along the direction parallel to the pattern 13 and the surface 12a of the hBN layer 12 as shown by the arrows in FIG. Since the hBN layer 12 has a structure in which six-membered rings composed of B and N are regularly arranged in the ab plane, the hBN layer 12 has a high thermal conductivity in the ab plane direction. Since the hBN layer 12 has a c-axis parallel to the normal of the surface 12a, the direction parallel to the surface 12a of the hBN layer 12 is the ab direction. For this reason, the thermal conductivity in the direction parallel to the surface 12a of the hBN layer 12 can be increased. Therefore, the heat generated from the mounting component 14 can be quickly diffused. That is, the flexible printed circuit board 10 in this Embodiment has high heat dissipation. Therefore, when the mounting component 14 is mounted on the pattern 13, the operation of the mounting component 14 can be stabilized.

  FIG. 11 is a cross-sectional view schematically showing a conventional flexible printed circuit board. As shown in FIG. 11, the conventional flexible printed circuit board 50 does not include the hBN layer 12. That is, the flexible printed circuit board 50 includes the substrate 11, the pattern 13 formed on the substrate 11, the mounting component 14 formed on the pattern 13, and the wire 15 that electrically connects the pattern 13 and the mounting component 14. And. The heat generated from the mounting component 14 passes through the substrate 11. When the substrate 11 is polyimide, the thermal conductivity of polyimide is about 0.2 W / mK. For this reason, since the heat dissipation path passes through polyimide having low thermal conductivity, the heat dissipation of the flexible printed circuit board 50 is very low.

(Embodiment 2)
The flexible printed circuit board 10 in the present embodiment is the same as the flexible printed circuit board 10 shown in FIG. 1 in the first embodiment, but the manufacturing method is different. The method for manufacturing flexible printed circuit board 10 in the present embodiment is basically the same as that in the first embodiment, but differs in that step S2 for forming the amorphous BN layer shown in FIG. 4 is not provided.

  Specifically, first, as shown in FIGS. 2 and 3, a conductive substrate 16 to be a pattern 13 is prepared as in the first embodiment (step S1).

  Next, as shown in FIG. 2 and FIG. 6, a hBN layer 12 is formed by supplying a gas containing B element, a gas containing N element, and a Ga gas onto a conductive substrate 16 ( Step S3). By supplying a gas containing B element and a gas containing N element together with Ga gas, instead of amorphous BN, as shown in FIG. 7, a six-membered ring of B atoms and N atoms is regularly arranged. The oriented hBN can be formed.

Here, a method for supplying a gas containing B element, a gas containing N element, and Ga gas will be described. For example, the substrate 16 is placed in a furnace held in a vacuum, and a gas containing B element, a gas containing N element, and a Ga gas are supplied to the furnace. As the gas containing B element, for example, B ₂ H ₆ (diborane) can be used. As the gas containing N element, at least one of N ₂ gas and NH ₃ gas can be used. However, the supply method of the gas containing B element, the gas containing N element, and Ga gas is not specifically limited. For example, heating may be performed in a state where liquid Ga is disposed in the furnace to generate Ga gas in the furnace, and a gas containing B element and a gas containing N element may be supplied into the furnace.

  In this step S3, it is preferable to supply Ga gas at a temperature of 600 ° C. or higher and 800 ° C. or lower as in the first embodiment. Further, as in Embodiment Mode 1, it is preferable to apply plasma.

  Next, as in the first embodiment, as shown in FIG. 9, the hBN layer 12 and the insulating substrate 11 are bonded together (step S4). Next, as in the first embodiment, a part of the conductive substrate 16 is removed to form the pattern 13 (step S5).

  The flexible printed circuit board 10 shown in FIG. 1 can be manufactured by performing the above steps S1 and S3 to S5.

  As described above, according to the method for manufacturing flexible printed circuit board 10 in the present embodiment, a gas containing B element, a gas containing N element, and Ga gas are supplied onto conductive substrate 16. Thus, the hBN layer 12 is formed. By supplying a gas containing B element and a gas containing N element together with Ga gas, instead of amorphous BN, as shown in FIG. 7, a six-membered ring of B atoms and N atoms is regularly arranged. The present inventor has found that hBN with the same orientation can be formed. For this reason, the hBN layer 12 having high thermal conductivity in the direction parallel to the surface 12a can be formed. Therefore, the heat generated from the mounting component 14 can be quickly diffused. Therefore, when the mounting component 14 is mounted on the pattern 13, the operation of the mounting component 14 can be stabilized.

  In particular, the hBN layer 12 having a large area and a large thickness can be formed by mixing and supplying a source gas containing a Ga element, a B element, and an N element. For this reason, the manufacturing method of the present embodiment is advantageous when the hBN layer 12 having a large area and / or thickness is formed.

(Embodiment 3)
FIG. 12 is a perspective view schematically showing a flexible printed board in the present embodiment. As shown in FIG. 12, the flexible printed circuit board 20 in the present embodiment basically has the same configuration as that of the flexible printed circuit board 10 in the first embodiment, but includes the hBN layer 12 and the pattern 13. The difference is that it further includes an amorphous BN layer 17 formed therebetween.

  The amorphous BN layer 17 preferably has a thickness of 3 μm or more and 15 μm or less. In the case of 3 μm or more, peeling between the hBN layer 12 and the pattern 13 can be effectively suppressed. In the case of 15 μm or less, it is possible to suppress a decrease in the heat dissipation effect due to the Amophus BN layer 17 having a thermal conductivity lower than that of the hBN layer 12.

  The manufacturing method of the flexible printed circuit board 20 in the present embodiment is basically the same as the manufacturing method of the flexible printed circuit board 10 in the first embodiment, but in step S3 for forming the hBN layer 12, the amorphous BN layer 17 is formed. However, it is different in that the amorphous BN layer 17 is maintained without sufficiently contacting the Ga gas.

  Specifically, first, as shown in FIGS. 2 to 4, a conductive substrate 16 is prepared in the same manner as in the first embodiment (step S1), and an amorphous BN layer 17 is formed (step S2).

  From the viewpoint of securing the thickness of the amorphous BN layer 17 and the hBN layer 12, in the present embodiment, it is preferable to form the amorphous BN layer 17 so as to have a thickness of 6 μm to 25 μm in step S2. Thereby, the amorphous BN layer 17 having a thickness of 3 μm or more and 15 μm or less and the hBN layer 12 having a thickness of 3 μm or more and 10 μm or less can be formed.

  FIG. 13 is a perspective view schematically showing a state where an amorphous BN layer is formed in the present embodiment. Next, as shown in FIG. 13, the surface 17a of the amorphous BN layer 17 is brought into contact with Ga gas, and the back surface of the amorphous BN layer 17 is not brought into contact with Ga gas (step S3). Thereby, the amorphous BN layer 17 in the vicinity of the surface 17a is generated in the hBN layer 12, and the amorphous BN layer 17 in contact with the substrate 16 is not generated in the hBN layer 12.

  FIG. 14 is a perspective view schematically showing a state in which the substrates in the present embodiment are bonded together. Next, as shown in FIG. 14, the hBN layer 12 and the insulating substrate 11 are bonded together (step S4).

  Next, as in the first embodiment, a part of the conductive substrate 16 is removed to form the pattern 13 (step S5).

  The flexible printed circuit board 20 shown in FIG. 12 can be manufactured by performing the above steps S1 to S5.

  As described above, in the flexible printed circuit board 20 and the manufacturing method thereof in the present embodiment, the amorphous BN layer 17 is formed between the hBN layer 12 and the pattern 13.

The thermal expansion coefficient in the ab plane of hBN is as extremely small as 1 × 10 ⁻⁶ / K. When the substrate 16 constituting the pattern 13 is Cu, the thermal expansion coefficient of the substrate 16 is 16 × 10 ⁻⁶ / K. When the hBN layer 12 is directly formed on the substrate 16, thermal stress is generated at the interface between the hBN layer 12 and the substrate 16 during the cooling process after the hBN layer 12 is formed, and the hBN layer 12 tends to be peeled off. This tendency is remarkable when the thickness of the hBN layer 12 is large.

  However, in this embodiment, an amorphous BN layer 17 is formed between the hBN layer 12 and the pattern 13. Since the crystals of the amorphous BN layer 17 are not oriented in a specific direction, the thermal expansion coefficient of the amorphous BN layer 17 is larger than the thermal expansion coefficient of the hBN layer 12. When the thermal expansion coefficient of the pattern 13 is larger than the thermal expansion coefficient of the hBN layer 12, the difference in the thermal expansion coefficient between the hBN layer 12 and the pattern 13 can be reduced by providing the amorphous BN layer 17. For this reason, since the thermal stress produced by the difference of the thermal expansion coefficient of the pattern 13 and the hBN layer 12 can be reduced, it can suppress that the pattern 13 and the hBN layer 12 peel.

(Embodiment 4)
The flexible printed circuit board 20 in the present embodiment is the same as the flexible printed circuit board 20 shown in FIG. 12 in the third embodiment, but the manufacturing method is different. The manufacturing method of the flexible printed circuit board 20 in the present embodiment is basically the same as that in the third embodiment, but differs in that the hBN layer 12 is not formed from the amorphous BN layer 17 shown in FIG.

  First, specifically, as shown in FIGS. 2 to 4, a conductive substrate 16 is prepared in the same manner as in the first embodiment (step S1), and an amorphous BN layer 17 is formed (step S2).

  Next, as shown in FIGS. 2 and 13, a hBN layer 12 is formed by supplying a gas containing B element, a gas containing N element, and Ga gas onto a conductive substrate 16 ( Step S3). In the present embodiment, the hBN layer 12 is formed on the amorphous BN layer 17.

  Next, as in the third embodiment, as shown in FIG. 14, the hBN layer 12 and the insulating substrate 11 are bonded together (step S4).

  Next, as in the first embodiment, a part of the conductive substrate 16 is removed to form the pattern 13 (step S5).

  The flexible printed circuit board 20 shown in FIG. 12 can be manufactured by performing the above steps S1 and S3 to S5.

  As described above, the method for manufacturing the flexible printed circuit board 20 according to the present embodiment supplies a gas containing B element, a gas containing N element, and Ga gas onto the conductive substrate 16. The hBN layer 12 is formed.

  As a result, the amorphous BN layer 17 and the hBN layer 12 can be formed with improved controllability. For this reason, the flexible printed circuit board 20 which has the effect of the peeling suppression by the amorphous BN layer 17 and the heat dissipation effect by the hBN layer 12 can be manufactured.

  Here, in the first to fourth embodiments, the flexible printed circuit board 10 is described as an example of the printed circuit board. However, the printed circuit board of the present invention is not limited to the flexible printed circuit board and includes a rigid circuit board.

  In this example, the effect of forming the hBN layer was examined by bringing the surface of the amorphous BN layer into contact with Ga gas.

(Invention Examples 1 and 2)
In Invention Examples 1 and 2, the flexible printed circuit board 10 shown in FIG.

  Specifically, first, a Cu foil having a thickness of 25 μm was prepared as the conductive substrate 16 constituting the pattern 13 (step S1).

  Next, an amorphous BN layer 17 having a surface 17a was formed on the conductive substrate 16 by pulsed laser deposition (PLD) (step S2).

  Next, the hBN layer 12 was formed by bringing the surface 17a of the amorphous BN layer 17 into contact with Ga gas (step S4). FIG. 15 is a cross-sectional view schematically showing a generating apparatus for forming the hBN layer in this example. Here, the generation apparatus used in the present embodiment will be described with reference to FIG.

  As shown in FIG. 15, the generation apparatus 100 mainly includes a container 104, a reaction tube 106, and a heater 107. The reaction tube 106 is a quartz tube having a length of 1 m and a diameter of 25 mm. A container 104 is disposed inside the reaction tube 106. The container 104 is an alumina container having a diameter of 1 cm. The container 104 is filled with liquid Ga. The heater 107 is disposed outside the reaction tube 106 and heats the inside of the reaction tube 106.

  The generation apparatus 100 may include various elements other than those described above, but illustration and description of these elements are omitted for convenience of description.

In this step S4, first, the substrate 16 and the substrate to be processed of the amorphous BN layer 17 formed on the substrate 16 are horizontally placed so that the amorphous BN layer 17 is exposed in the vicinity of the container 104 inside the reaction tube 106. Arranged. After that, the evacuation system 108 was evacuated by a turbo pump, and the background was evacuated to 10 ⁻⁶ Torr or less. Next, the temperature of the Ga vapor 105 was raised to the temperature shown in Table 1 by the heater 107, and the substrate to be processed was brought into contact with the Ga vapor 105 for the time shown in Table 1. Thereafter, it was gradually cooled to room temperature. As a result, the amorphous BN layer 17 was converted into the hBN layer 12.

  Next, the hBN layer 12 and the insulating substrate 11 were bonded together with an adhesive (step S4). A polyimide film was used as the insulating substrate 11.

  Through the above steps S1 to S4, the flexible printed circuit board of Examples 1 and 2 of the present invention was manufactured.

(Comparative Example 1)
The flexible printed circuit board of Comparative Example 1 was basically manufactured in the same manner as in Invention Examples 1 and 2, but differed in that an amorphous BN layer was not formed. That is, the flexible printed board of Comparative Example 1 was composed of a polyimide film and a Cu foil formed on the polyimide film.

(Comparative Example 2)
The flexible printed circuit board of Comparative Example 2 was basically manufactured in the same manner as Examples 1 and 2 of the present invention. However, the hBN layer 12 was formed by bringing the surface 17a of the amorphous BN layer 17 into contact with Ga gas, step S3. It was different only in that it was not implemented. That is, the flexible printed board of Comparative Example 2 was composed of a polyimide film, an amorphous BN layer formed on the polyimide film, and a Cu foil formed on the amorphous BN layer.

(Measuring method)
The flexible printed boards of Invention Examples 1 and 2 and Comparative Examples 1 and 2 were observed using a transmission electron microscope. In addition, the cross section of the flexible printed circuit board of this invention example 1 and 2 and the comparative examples 1 and 2 was formed, and thickness was determined by scanning electron microscope observation. In Table 1 below, the thickness of the BN layer indicates the thickness of the hBN layer 12 in Invention Examples 1 and 2, and the thickness of the amorphous BN layer in Comparative Example 2.

  Moreover, about the flexible printed circuit board of this invention example 1 and 2 and comparative examples 1 and 2, thermal resistance was measured with the following method.

  FIG. 16 is a side view schematically showing a sample for measuring the thermal conductivity of the flexible printed circuit board of Examples 1 and 2 of the present invention. FIG. 17 is a side view schematically showing a sample for measuring the thermal conductivity of the flexible printed circuit board of Comparative Example 1. As shown in FIGS. 16 and 17, a part of the conductive substrate 16 of Examples 1 and 2 of the present invention and Comparative Examples 1 and 2 was chemically etched to form a protrusion having a diameter of 3 mm. The external shape of Comparative Example 2 was the same as that of Invention Examples 1 and 2. Thus, a sample S (see FIG. 18) for measuring the thermal conductivity was produced.

  FIG. 18 shows a measuring apparatus 200 for measuring the thermal conductivity in this embodiment. The measuring apparatus 200 includes heat insulating materials 202 and 203, a prism 204, a Cu holder 205, a thermocouple hole 206, a thermocouple 207, and an AlN heater 208. The upper Cu holder 205 has a cylindrical shape made of Cu having a diameter of 3 mm, and was embedded in a 10 mm square Teflon (registered trademark) prism 204.

As shown in FIG. 18, each sample S was sandwiched between Cu holders 205, and the sample S was pressed with a pressure of 3 kg / cm ² . Thereafter, the upper Cu holder 205 was heated with an AlN heater 208. The upper Cu holder 205 has five thermocouple holes 206, and the temperature at the center is measured, and the temperature T0 (see FIGS. 16 and 17) of the upper surface of the sample S is extrapolated from the temperature gradient.

  On the other hand, the back surface of the sample S is in contact with the upper surface of the lower Cu holder 205. On the lower surface of the sample S, the substrate 11 and the hBN layer 12 in the first and second examples of the present invention, the substrate 11 in the first comparative example, the substrate 11 in the first comparative example, and the position of 6.3 mm diagonally from the center of the sample S. Through holes were provided in the substrate 1 and the amorphous BN layer. Then, a thermocouple 207 is attached so that the temperature of the hBN layer in the present invention examples 1 and 2 can be measured, the substrate 11 in the comparative example 1 and the amorphous BN layer in the comparative example 2 can be measured. The temperatures T1 and T2 (see FIGS. 16 and 17) on the upper surface of the layer located at δ were directly measured.

  As described above, the heat of the AlN heater 208 is transmitted only to the vicinity of the center of the upper surface of the sample S. The test conditions were a measurement time of 10 minutes and a calorific value of 12W.

The thermal resistance was calculated from the following formula.
Measurement of thermal resistance (° C./W)=(sample top surface temperature T0−sample bottom surface temperature T1) / applied power temperature difference ΔT = T1-T2
These results are shown in Table 1 below.

(Measurement result)
As a result of observing the flexible printed boards of Examples 1 and 2 and Comparative Examples 1 and 2 using a transmission electron microscope, in Examples 1 and 2 of the present invention, the orientation of the c-axis parallel to the surface normal is shown. It was found that it was formed in the hBN layer. At this time, the surface of the substrate was not particularly uneven in color and rough, and was in an extremely smooth mirror state.

  Moreover, it was found from the sheet resistance measurement that the hBN layer and the amorphous BN layer all have insulating properties.

  Further, it was found that Inventive Examples 1 and 2 in which the amorphous BN layer was brought into contact with Ga gas had a small ΔT and high heat dissipation performance. In Comparative Example 2 in which the amorphous BN layer was not brought into contact with Ga gas, the heat dissipation performance was lower than those of Examples 1 and 2 of the present invention. This is because the amorphous BN layer is not oriented. In Comparative Example 2 in which the BN layer was not formed, the heat dissipation performance was much lower than those of Invention Examples 1 and 2.

  As described above, according to this example, it was confirmed that an oriented hBN layer having a c-axis parallel to the surface normal can be formed by bringing the surface of the amorphous BN layer into contact with Ga gas. . It was also confirmed that the hBN layer was insulating. Further, it was confirmed that the heat dissipation characteristics can be improved by forming the hBN layer 12 between the substrate 11 and the pattern 13.

  In this example, the effect of forming the hBN layer was examined by supplying a gas containing B element, a gas containing N element, and Ga gas onto a conductive substrate.

(Invention Examples 3 to 6)
Inventive Examples 3 to 6 basically manufactured flexible printed circuit board 10 shown in FIG. 1 according to the second embodiment.

  Specifically, first, a Cu foil having the same thickness of 25 μm as Example 1 of the present invention was prepared as the conductive substrate 16 constituting the pattern 13 (step S1).

  Next, an oriented hBN layer having a c-axis parallel to the surface normal is formed by supplying a gas containing B element, a gas containing N element, and Ga gas onto a conductive substrate. (Step S3). FIG. 19 is a cross-sectional view schematically showing a generating apparatus for forming the hBN layer in this example. Here, with reference to FIG. 19, the production | generation apparatus 300 used by the present Example is demonstrated. The generating apparatus 300 is an external heat type thermal CVD furnace.

  As shown in FIG. 19, the generation apparatus 300 mainly includes a reaction tube 301, a carbon plate 302, and a heater 303. The reaction tube 301 is a carbon furnace core tube having an inner diameter of 200 mm. A carbon plate 302 is disposed inside the reaction tube 301, and a gap is formed in the carbon plate 302. A SiC substrate 310 is disposed on the carbon plate 302. The heater 303 is disposed outside the reaction tube 301 and heats the inside of the reaction tube 301.

  The generation apparatus 300 may include various elements other than those described above, but illustration and description of these elements are omitted for convenience of description.

In step S3, first, the substrate 16 was placed in close contact with the SiC substrate 310.
Thereafter, Ga gas and B ₂ H ₆ gas as G1 and NH ₃ gas as G2 were introduced, heated, and then naturally cooled. Thereby, the hBN layer 12 was formed on the conductive substrate 16.

  Next, as in Invention Examples 1 and 2, the hBN layer 12 and the insulating substrate 11 were bonded together with an adhesive (step S4). Through the above steps S1, S3, and S4, flexible printed circuit boards according to Invention Examples 3 to 6 were manufactured.

(Invention Example 7)
Invention Example 7 was basically produced in the same manner as Invention Example 1, but differed in that a recess was formed on the surface of the conductive substrate 16.

(Invention Examples 8 and 9)
Inventive Examples 8 and 9 were basically manufactured in the same manner as Inventive Example 1, but by supplying a gas containing B element and a gas containing N element onto the conductive substrate 16, The difference was that an amorphous BN layer was formed between the crystal BN layer 12 and the conductive substrate 16 (step S2).

Specifically, in Inventive Examples 8 and 9, B ₂ H ₆ gas and NH ₃ gas were introduced and heated without introducing a gas containing Ga element, and then naturally cooled. Thereby, an amorphous BN layer was formed.

(Measuring method)
About the flexible printed circuit board of the invention examples 3-9, it observed using the transmission electron microscope and the scanning electron microscope similarly to Example 1. FIG.

  Moreover, about the flexible printed circuit board of the invention examples 3-9, the sample S was produced similarly to Example 1, and the thermal resistance was measured. The results are shown in Table 2 below.

(Measurement result)
As a result of observing the flexible printed boards of Invention Examples 3 to 9 using a transmission electron microscope, it was found that the flexible printed circuit board was formed in an oriented hBN layer having a c-axis parallel to the surface normal. In addition, it was found that amorphous BN layers were formed in Invention Examples 8 and 9.

  Moreover, it was found from the sheet resistance measurement that the hBN layer and the amorphous BN layer all have insulating properties.

  Further, as shown in Table 2, it was found that the thicker the hBN layer 12, the smaller ΔT and the better the heat dissipation performance. However, the greater the thickness of the hBN layer 12, the higher the thermal resistance. This is because the compressive stress in the hBN layer increases as the thickness of the hBN layer 12 increases, and minute peeling or the like occurs between the conductive substrate 16 and the like. .

  Furthermore, in Example 7 of the present invention in which fine irregularities were provided on the surface of the conductive substrate 16, the adhesion strength between the hBN layer 12 and the conductive substrate 16 was higher, so that the thermal resistance was higher than that of Example 6 of the same conditions. The ΔT was also low.

  Furthermore, Invention Example 8 in which an amorphous BN layer was formed had low thermal resistance and ΔT. This is probably because the thermal stress can be alleviated, so that fine cracks are hardly generated. However, as shown in Invention Example 9, it was found that the thermal resistance increases as the amorphous BN layer becomes thicker.

  As described above, according to the present embodiment, by supplying a gas containing B element, a gas containing N element, and Ga gas onto a conductive substrate, it has a c-axis parallel to the surface normal. It was confirmed that an oriented hBN layer could be formed. It was also confirmed that the hBN layer was insulating. Further, it was confirmed that the heat dissipation characteristics can be improved by forming the hBN layer 12 between the substrate 11 and the pattern 13.

  Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning to appropriately combine the features of the embodiments and examples. The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

  10, 20 Flexible printed circuit board, 11, 16 circuit board, 12 hBN layer, 12a, 16a, 17a front surface, 12b back surface, 13 patterns, 14 mounting parts, 15 wires, 17 amorphous BN layer, 100, 300 generator, 104 container, 105 Ga vapor, 106,301 reaction tube, 107,208,303 heater, 108 vacuum exhaust system, 200 measuring device, 202 heat insulating material, 204 prism, 205 holder, 206 thermocouple hole, 207 thermocouple, 302 carbon plate, 310 SiC substrate.

Claims (13)

An insulating substrate;
A hexagonal boron nitride layer formed on the insulating substrate and having a surface;
A conductive pattern formed on the surface of the hexagonal boron nitride layer,
The printed circuit board, wherein the hexagonal boron nitride layer has an orientation having a c-axis parallel to a normal to the surface of the hexagonal boron nitride layer. The insulating substrate is a resin;
The printed circuit board according to claim 1, wherein the pattern is copper.   The printed circuit board according to claim 1, wherein the hexagonal boron nitride layer has a thickness of 3 μm to 10 μm.   The printed circuit board according to claim 1, further comprising an amorphous boron nitride layer formed between the hexagonal boron nitride layer and the pattern.   The printed circuit board according to claim 4, wherein the amorphous boron nitride layer has a thickness of 3 μm to 15 μm. Preparing a conductive substrate to be a pattern;
Forming an amorphous boron nitride layer having a surface on the conductive substrate;
Forming an oriented hexagonal boron nitride layer having a c-axis parallel to the normal of the surface by contacting the surface of the amorphous boron nitride layer with gallium gas;
A method for manufacturing a printed circuit board, comprising: bonding the hexagonal boron nitride layer and an insulating substrate. Preparing a conductive substrate to be a pattern;
An oriented hexagonal boron nitride layer having a c-axis parallel to the surface normal is formed by supplying a gas containing boron element, a gas containing nitrogen element, and gallium gas onto a conductive substrate. And a process of
A method for manufacturing a printed circuit board, comprising: bonding the hexagonal boron nitride layer and an insulating substrate.   The method for manufacturing a printed circuit board according to claim 7, wherein in the step of forming the hexagonal boron nitride layer, at least one of nitrogen gas and ammonia gas is used as the gas containing the nitrogen element.   A step of forming an amorphous boron nitride layer between the hexagonal boron nitride layer and the conductive substrate by supplying a gas containing boron element and a gas containing nitrogen element onto the conductive substrate. The printed circuit board manufacturing method according to claim 7, further comprising: In the step of preparing the conductive substrate, a copper substrate is used as the conductive substrate,
The method for manufacturing a printed circuit board according to any one of claims 6 to 9, wherein a resin sheet is used as the insulating substrate in the step of bonding the insulating substrate.   The method for manufacturing a printed circuit board according to any one of claims 6 to 10, wherein the step of forming the hexagonal boron nitride layer is performed at a temperature of 600 ° C or higher and 800 ° C or lower.   The method for manufacturing a printed circuit board according to claim 6, wherein plasma is applied in the step of forming the hexagonal boron nitride layer.   The method of manufacturing a printed circuit board according to any one of claims 6 to 12, wherein the step of preparing the conductive substrate includes a step of forming a recess on a surface of the conductive substrate.

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