JP5893596B2 - Adhesive thermoplastic liquid crystal polymer film, multilayer circuit board, and manufacturing method thereof - Google Patents

Description

  The present invention is a multilayer formed from a thermoplastic liquid crystal polymer film (hereinafter sometimes referred to as a thermoplastic liquid crystal polymer film) that forms an optically anisotropic melt phase, and can be formed by thermal bonding without using an adhesive. The present invention relates to a circuit board and a manufacturing method thereof.

  While miniaturization and high functionality of electronic devices are demanded, the demand for multilayer circuit boards in which circuit boards are multilayered is increasing in order to satisfy these demands.

  2. Description of the Related Art Conventionally, a multilayer circuit board is known which is formed by laminating a substrate in which a conductor circuit is formed on a polyimide film and a coverlay film composed of a polyimide film and an adhesive layer.

  However, since such a multilayer circuit board uses an adhesive, it may be inferior in heat resistance, particularly solder resistance. In addition, in such a multilayer circuit board, a solvent derived from the adhesive may remain, and such a residual solvent causes a problem in the circuit board after the multilayering and reduces the reliability of the circuit board. There is a risk that. Therefore, there is a demand for a technique for forming a multilayer circuit board without using an adhesive.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2006-179609) discloses a unit substrate in which a conductive layer is provided on at least one surface of a thermoplastic liquid crystal polymer layer in order to form a multilayer circuit substrate without using an adhesive. In the method of manufacturing a laminated wiring board by stacking, a chemical liquid roughening treatment or a plasma roughening treatment with an alkali mixed solution is performed on at least one surface of each of the thermoplastic liquid crystal polymer layers. A method of manufacturing a laminated wiring board is disclosed in which a laminated board having two or more layers is formed by superimposing the prepared surface on the surface of another unit substrate, and the laminated board is heated and pressurized.

  According to Patent Document 1, according to this manufacturing method, a dense roughened surface is formed on the surface of the liquid crystal polymer layer without affecting the circuit formed on the surface layer of each unit substrate constituting the wiring substrate. It is described that a wiring board having excellent adhesion between liquid crystal polymer layers can be obtained.

JP 2006-179609 A (Claims 1 and 10, paragraph number [0012])

  However, in the wiring board described in Patent Document 1, there is a trade-off relationship between improving the adhesiveness and protecting the conductive layer, and chemical roughening or plasma roughening for improving the adhesiveness. If the treatment is performed, the conductive layer may be destroyed.

  Furthermore, in the chemical treatment with an alkali mixed solution, a process of cleaning the chemical-treated substrate is essential, and the process becomes complicated. In addition to this, facilities that take into account the safety with respect to chemicals are required, and further facilities for treating the waste liquid discharged during the manufacture are further required, resulting in a large cost burden.

  On the other hand, in the plasma roughening treatment, problems such as waste liquid treatment do not occur, but a large facility burden is required to perform the plasma treatment.

Accordingly, an object of the present invention is to provide a multilayer circuit board that can be formed by thermal bonding without using an adhesive and that can improve the integrity without destroying the conductive layer (or conductor circuit).
Another object of the present invention is to provide a multilayer circuit board which is excellent in dimensional stability as well as solder resistance.

  Still another object of the present invention is to provide a method capable of producing a multilayer circuit board without using facilities for making the waste liquid pollution-free or expensive equipment for plasma processing.

The inventors of the present invention have intensively studied to solve such problems,
(I) Conventionally, in the case of forming an adhesive surface, it has been a usual method to form an uneven shape on the adhesive surface and improve the adhesive property by the anchor effect. Since a hard skin layer is generated on the surface at the time of molding, it is important to adjust the hardness of the film surface in order to improve the adhesion by thermocompression,
(Ii) Measuring the macro hardness (for example, Vickers hardness) of the entire molded product is not appropriate for grasping the hardness of only the surface layer in a thin film such as a film, that is, the skin layer. Hardness can be accurately grasped for the first time by the nanoindentation method. (Iii) Physical polishing or ultraviolet irradiation is effective for softening a thermoplastic liquid crystal polymer film to a specific hardness. In this softening treatment method, the present inventors have found that not only the equipment for making the waste liquid pollution-free is unnecessary, but also the cost burden such as plasma treatment can be reduced.

That is, the present invention is a method of manufacturing a multilayer circuit board, the manufacturing method,
A film forming step of forming a thermoplastic liquid crystal polymer film by extruding a thermoplastic liquid crystal polymer that forms an optically anisotropic melt phase;
By subjecting at least one surface of the thermoplastic liquid crystal polymer film to physical polishing or ultraviolet irradiation, the film surface has a hardness of 0.01 to 0.1 GPa measured by a nanoindentation method. Softening step to form an adhesive surface,
The adhesive surface is opposed to the circuit forming surface of the substrate on which the conductor circuit is formed on at least one surface of the thermoplastic liquid crystal polymer film forming the optically anisotropic molten phase, and the whole is bonded by thermocompression bonding. Crimping process;
including.

  In the manufacturing method, in the softening step, a thickness of 0.01 to 1 μm may be removed from the film surface by physical polishing to form an adhesive surface, and adhesion is performed by simultaneously irradiating ultraviolet rays having wavelengths of 185 nm and 254 nm. A surface may be formed.

Further, in the method for producing a multilayer circuit board, the adhesiveness can be improved even if the melting point of the adhesive polymer layer is high. Therefore, the thermocompression bonding temperature is the melting point of the thermoplastic liquid crystal polymer forming the adhesive polymer layer ( Ta: ° C.) is selected from the range of 15 ° C. or higher and 15 ° C. higher than the melting point, and the thermocompression bonding temperature is the melting point of the thermoplastic liquid crystal polymer forming the substrate layer ( Tb: ° C.) may be satisfied within a range of 20 ° C. lower than the temperature and 10 ° C. higher than the melting point.
The multilayer circuit board of the present invention comprises a substrate layer having a conductor circuit formed on at least one surface of a thermoplastic liquid crystal polymer film forming an optically anisotropic molten phase;
An adhesive film layer that is thermocompression-bonded with the adhesive surface facing the circuit forming surface of the substrate layer;
A multilayer circuit board comprising at least
The adhesive film layer is a thermoplastic liquid crystal polymer film forming an optically anisotropic melt phase, and the adhesive surface of the adhesive film layer has a hardness of 0.01 to 0 measured by a nanoindentation method. .1 GPa.

  In the multilayer circuit board, the adhesive surface of the adhesive film layer may be formed by physical polishing or ultraviolet irradiation. Moreover, about 10-100 micrometers may be sufficient as the thickness of an adhesive film layer. Such an adhesive film layer can be effectively used as a coverlay film and / or a bonding film.

  Since the adhesive surface of the adhesive film layer is softened, the intermixability of the adhesive film layer and the substrate layer is increased. For example, the melting point (Ta: ° C) of the thermoplastic liquid crystal polymer forming the adhesive film layer, The melting point (Tb: ° C.) of the thermoplastic liquid crystal polymer forming the substrate layer may satisfy, for example, Ta ≦ Tb + 5.

  In this specification, the hardness by the nanoindentation method on the adhesive surface of the adhesive film layer means the hardness exhibited by the surface of the adhesive film layer before performing thermocompression bonding for forming a circuit board. Yes.

  According to the present invention, a thermoplastic liquid crystal polymer film is used as a base material, and an adhesive film layer having a specific surface hardness and a substrate layer on which a conductor circuit is formed can be combined with each other without using an adhesive. In addition to being integrated by crimping, the integrity of the multilayer substrate circuit can be improved without destroying the conductor circuit.

  In addition, by using an adhesive film layer having a specific surface hardness, it becomes possible to increase the melting point of the thermoplastic liquid crystal polymer film used as the adhesive film layer, forming a substrate layer and an adhesive film layer. It becomes possible to bring the melting points of the respective thermoplastic liquid crystal polymers close to each other. As a result, the integrity and thermal management of the multilayer circuit board can be improved.

  Furthermore, in the method for producing a multilayer circuit board according to the present invention, the surface of the adhesive film can be softened by physical polishing or ultraviolet irradiation. Therefore, the cost required for the waste liquid treatment and the plasma roughening treatment can be reduced.

  Hereinafter, a preferred embodiment of a multilayer wiring circuit board according to the present invention will be described with reference to the accompanying drawings. Note that the drawings are not necessarily shown to scale, and are exaggerated for illustrating the principles of the present invention. In the accompanying drawings, the same part number in the plurality of drawings indicates the same part.

An example of the manufacturing process of the multilayer circuit board concerning a 1st embodiment of the present invention is shown. (A) shows the state before manufacturing a multilayer circuit board by thermocompression bonding, and (b) shows the multilayer circuit board after thermocompression bonding. An example of the manufacturing process of the multilayer circuit board concerning a 2nd embodiment of the present invention is shown. (A) shows the state before manufacturing a multilayer circuit board by thermocompression bonding, and (b) shows the multilayer circuit board after thermocompression bonding. An example of the manufacturing process of the multilayer circuit board concerning a 3rd embodiment of the present invention is shown. (A) shows the state before manufacturing a multilayer circuit board by thermocompression bonding, and (b) shows the multilayer circuit board after thermocompression bonding.

  FIG. 1 shows an example of a manufacturing process of a multilayer circuit board according to the first embodiment of the present invention. FIG. 1A shows a state before the multilayer circuit board 10 is manufactured by thermocompression bonding. In this figure, a conductor circuit is formed on both sides of a thermoplastic liquid crystal polymer film (hereinafter sometimes referred to as a thermoplastic liquid crystal polymer film) that forms an optically anisotropic melt phase between the adhesive film layers 13 and 13. A substrate layer 11 on which 12 and 12 are formed is interposed. The adhesive film layers 13 and 13 respectively have adhesive surfaces 13a and 13a that face the formation surface of the conductor circuit, and these adhesive surfaces 13a and 13a are previously subjected to softening treatment so as to exhibit a predetermined hardness. It is attached. The multilayer circuit board 10 shown in FIG. 1B can be obtained by thermocompression bonding of the laminated substrate layer 11 and the adhesive film layers 13 and 13.

  In the multilayer circuit board 10 shown in FIG. 1 (b), the adhesive surfaces 13a, 13a of the adhesive film layers 13, 13 are melted by thermocompression bonding so that the conductor circuit is embedded in the adhesive film, The adhesive film layers 13 and 13 are integrated. Here, in the adhesive film layer 13, since only the adhesive surface 13a is softened, a highly oriented surface skin layer is still formed on the other surface 13b that has not been softened. For this reason, in the adhesive film layers 13 and 13, the adhesive surface 13 a is made easily adhesive by thermocompression bonding, while the other non-adhesive surface 13 b can maintain difficult adhesiveness. Is useful as a coverlay film for multilayer circuit boards.

  FIG. 2 shows an example of a manufacturing process of a multilayer circuit board according to the second embodiment of the present invention. FIG. 2A shows a state before the multilayer circuit board 20 is manufactured by thermocompression bonding. In this figure, a substrate layer 21 having conductor circuits 22 and 22 formed on both sides of a thermoplastic liquid crystal polymer film and a substrate layer 23 having conductor circuits 24 and 24 formed on both sides of a thermoplastic liquid crystal polymer film. The first adhesive film layer 25 is interposed, and the substrate layer 21, the first adhesive film layer 25, and the substrate layer 23 are arranged in this order between the second adhesive film layers 26, 26. Is intervening.

  Both surfaces of the first adhesive film layer 25 are adhesive surfaces 25a and 25b, and these adhesive surfaces 25a and 25b are connected to the conductor circuits 22 and 24 formed on the substrate layer 21 and the substrate layer 23, respectively. Opposite. The adhesive film layers 26 and 26 each have adhesive surfaces 26a and 26a on one side, and these adhesive surfaces 26a and 26a are conductors formed on the substrate layer 21 and the substrate layer 23, respectively. Opposing to the circuits 22 and 24. The adhesive surfaces formed on the first and second adhesive film layers 25 and 26, that is, the adhesive surfaces 25a and 25b and the adhesive surfaces 26a and 26a, have been subjected to a softening process in advance so as to exhibit a predetermined hardness. . The multilayer circuit board 20 shown in FIG. 2B can be obtained by thermocompression bonding of the laminated substrate layer 21, the substrate layer 23, and the first and second adhesive film layers 25 and 26. it can.

  In the multilayer circuit board 20 shown in FIG. 2B, the adhesive surfaces 25a and 25b of the first adhesive film layer 25 and the adhesive surfaces 26a and 26a of the second adhesive film layers 26 and 26 are melted by thermocompression bonding. In each bonding surface, the conductor circuit is integrated with the substrate layers 21 and 23 so as to be embedded in the adhesive film.

Since the first adhesive film layer 25 is subjected to softening treatment on both surfaces 25a and 25b, the liquid crystal polymer film forming the first adhesive film layer has a highly oriented surface skin layer. The adhesive film layer 25 is not formed and is useful as a bonding film for a multilayer circuit board.
Moreover, the 2nd adhesive film layer 26 is useful as a coverlay film of a multilayer circuit board similarly to the adhesive film layer 13 described in 1st Embodiment.

  As still another embodiment, FIG. 3 shows an example of the manufacturing process of the multilayer circuit board according to the third embodiment of the present invention in which the conductor circuit is provided on the non-adhesive surface of the adhesive film layer. FIG. 3A shows a state before the multilayer circuit board 30 is manufactured by thermocompression bonding. In this figure, a substrate layer 31 having a conductor circuit 32 formed on one surface of a thermoplastic liquid crystal polymer film, an adhesive surface 33a formed on one surface, and a conductor circuit 34 formed on the other non-adhesive surface. The third adhesive film layer 33 and the fourth adhesive film layer 35 that has an adhesive surface 35a on one side and the other non-adhesive surface 35b is not subjected to surface modification or conductor circuit formation. They are stacked in this order.

  The adhesive surface 33 a of the third adhesive film layer 33 faces the conductor circuit 32 formed on the substrate layer 31. Further, the adhesive surface 35 a of the fourth adhesive film layer 35 faces the conductor circuit 34 formed on the third adhesive film layer 33. The adhesive surfaces formed on the third and fourth adhesive film layers 33, 35, that is, the adhesive surfaces 33a, 35a, have been subjected to a softening process in advance so as to exhibit a predetermined hardness. The multilayer circuit board 30 shown in FIG. 3B can be obtained by thermocompression bonding of the laminated substrate layer 31 and the third and fourth adhesive film layers 33 and 35.

  In the multilayer circuit board 30 shown in FIG. 3B, the adhesive surface 33a of the third adhesive film layer 33 and the adhesive surface 35a of the fourth adhesive film layer 35 are melted by thermocompression bonding. The conductor circuit is integrated so as to be embedded in the adhesive film.

  In other words, the substrate layer and the adhesive film layer in the multilayer circuit board may be in various lamination states depending on the formation surface of the conductor circuit, and the lamination of the substrate layer (base) and the adhesive film layer (contact). The states are (group) / (contact) / (group), (group) / (contact) / (group) / (contact) / (group), (group) / (contact) / (contact), (group) / (Contact) / (contact) / (contact) may be used.

  Although not shown in FIGS. 1 to 3, in these multilayer circuit boards, through-holes penetrating the entire circuit board by methods such as laser processing, drilling, and chemical etching as necessary after thermocompression bonding. May be formed to ensure electrical connection across all layers.

Hereafter, each component of the multilayer circuit board of this invention is explained in full detail.
(Substrate layer)
The substrate layer is formed of a thermoplastic liquid crystal polymer film that forms an optically anisotropic melt phase, and a conductor circuit is formed on at least one surface of the film.
The thermoplastic liquid crystal polymer film that forms the optically anisotropic melt phase is formed from the liquid crystal polymer that can be melt-molded as described below. Although there is no particular limitation, for example, a thermotropic liquid crystal polyester or a thermotropic liquid crystal polyester amide having an amide bond introduced therein may be used.
The molten liquid crystal polymer may be a polymer in which an aromatic polyester or an aromatic polyester amide is further introduced with an isocyanate-derived bond such as an imide bond, a carbonate bond, a carbodiimide bond or an isocyanurate bond.

  Specific examples of the molten liquid crystal polymer used in the present invention include known thermotropic liquid crystal polyesters and thermotropic liquid crystal polyester amides derived from the compounds classified as (1) to (4) and derivatives thereof exemplified below. be able to. However, it goes without saying that there are suitable ranges for combinations of various raw material compounds in order to form a polymer liquid crystal.

(1) Aromatic or aliphatic dihydroxy compounds (see Table 1 for typical examples)

(2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for typical examples)

（４）芳香族ジアミン、芳香族ヒドロキシアミンまたは芳香族アミノカルボン酸（代表例は表４参照） (3) Aromatic or aliphatic hydroxycarboxylic acids (see Table 3 for typical examples)

(4) Aromatic diamine, aromatic hydroxyamine or aromatic aminocarboxylic acid (see Table 4 for typical examples)

  Representative examples of the liquid crystal polymer obtained from these raw material compounds include copolymers having the structural units shown in Tables 5 and 6.

  Of these copolymers, a polymer containing at least p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as a repeating unit is preferable, and in particular, (i) p-hydroxybenzoic acid and 6-hydroxyoxy- A polymer containing a repeating unit with 2-naphthoic acid, (ii) 6-hydroxy-2-naphthoic acid, at least one aromatic diol selected from the group consisting of 4,4′-dihydroxybiphenyl and hydroquinone, and terephthalate A polymer containing a repeating unit with at least one aromatic dicarboxylic acid selected from the group consisting of acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid is the most preferred embodiment.

  For example, when the molten liquid crystal polymer contains at least repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the repeating unit (A) of p-hydroxybenzoic acid and the repeating unit (B) of 6 -The molar ratio (A) / (B) with hydroxy-2-naphthoic acid is desirably (A) / (B) = about 10/90 to 90/10 in the liquid crystal polymer, more preferably, (A) / (B) = about 50 / 50-85 / 15 may be sufficient, More preferably, (A) / (B) = about 60 / 40-80 / 20 may be sufficient.

Further, the molten liquid crystal polymer is 6-hydroxy-2-naphthoic acid, at least one aromatic diol selected from the group consisting of 4,4′-dihydroxybiphenyl and hydroquinone, terephthalic acid, isophthalic acid, and 2,6- When a repeating unit with at least one aromatic dicarboxylic acid selected from the group consisting of naphthalenedicarboxylic acid is included, the molar ratio of each repeating unit in the liquid crystal polymer is a repeating unit (C) of 6-hydroxy-2-naphthoic acid: The aromatic diol (D): the aromatic dicarboxylic acid (E) may be about 30 to 80:35 to 10:35 to 10, more preferably (C) :( D) :( E). = 35 to 75: 32.5 to 12.5: 32.5 to 12.5, more preferably (C) :( D) :( E ) = About 40-70: 30-15: 30-15.
Moreover, it is preferable that the molar ratio of the repeating structural unit derived from aromatic dicarboxylic acid and the repeating structural unit derived from aromatic diol is (D) / (E) = 95 / 100-100 / 95. Outside this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

  The optical anisotropy at the time of melting referred to in the present invention can be recognized by, for example, placing a sample on a hot stage, heating and heating in a nitrogen atmosphere, and observing the transmitted light of the sample.

  Preferred as the molten liquid crystal polymer is one having a melting point (hereinafter referred to as Mp) in the range of 260 to 360 ° C, more preferably Mp of 270 to 350 ° C. In addition, Mp is calculated | required by measuring the temperature where a main endothermic peak appears with a differential scanning calorimeter (Mettler DSC).

  The molten liquid crystal polymer is added with a thermoplastic polymer such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyester ether ketone, and fluororesin within a range not impairing the effects of the present invention. May be.

  The thermoplastic liquid crystal polymer film used in the present invention is obtained by extrusion molding of a thermoplastic liquid crystal polymer. Any extrusion method can be used for this purpose, but the well-known T-die method, inflation method, etc. are industrially advantageous. In particular, in the inflation method, stress is applied not only in the mechanical axis direction of the film (hereinafter abbreviated as MD direction) but also in the direction orthogonal to this (hereinafter abbreviated as TD direction). Since a film having a balance between mechanical properties and thermal properties can be obtained, it is more preferable. In addition, it is desirable that the thermoplastic liquid crystal polymer film has an isotropic property in which the mechanical and thermal properties between the MD direction and the TD direction are substantially uniform, thereby obtaining a multilayer circuit board having almost no warpage. It is done.

Moreover, a thermoplastic liquid crystal polymer film may control a thermal expansion coefficient to a predetermined | prescribed range by heating, after laminating | stacking once with metal foil as needed.
For example, the thermal expansion coefficient of the thermoplastic liquid crystal polymer film forming the substrate layer may be about 15 to 25 (× 10 ⁻⁶ cm / cm / ° C.), or 16 to 24 (× 10 ⁻⁶ cm / cm). / ° C.).

  Although there is no restriction | limiting in particular in the thickness of a thermoplastic liquid crystal polymer film, When using as a film which comprises a board | substrate layer, it is preferable that it is 5 mm or less in a printed wiring board use, and it exists in the range of 0.1-3 mm. More preferably. Moreover, in a flexible printed wiring board use, 500 micrometers or less are preferable and it is more preferable that it exists in the range of 10-250 micrometers.

  The thermoplastic liquid crystal polymer film thus obtained has a conductor circuit formed on at least one surface. The conductor circuit can be formed according to a known method. Specifically, (a) a method of forming a conductor circuit by laminating a thermoplastic liquid crystal polymer film and a metal sheet by thermocompression bonding and then performing an etching process, etc., (b) the surface of the thermoplastic liquid crystal polymer film And a method of forming a conductor layer by a vapor phase method such as a sputtering method, an ion plating method, a vacuum deposition method or a wet plating method to form a conductor circuit. As the material of the metal sheet that can be used for forming the conductor circuit by the method (a), a metal that is used for electrical connection is suitable, and examples thereof include copper, gold, silver, nickel, and aluminum. Of these, copper is preferred. The thickness of the metal sheet is preferably in the range of 1 to 50 μm, and more preferably in the range of 5 to 20 μm.

Moreover, when forming the conductor circuit by the method (b), examples of the material constituting the conductor layer include the metals described above, and among these, copper is preferable. The thickness of the conductor layer is not particularly limited, but is preferably in the range of 1 to 50 μm, and more preferably in the range of 5 to 20 μm.
The thickness of the conductor circuit formed on the thermoplastic liquid crystal polymer film corresponds to the thickness of the metal sheet or conductor layer described above and is preferably in the range of 1 to 50 μm, preferably in the range of 5 to 20 μm. It is more preferable that

(Adhesive film layer)
The adhesive film layer is formed from a thermoplastic liquid crystal polymer film that forms an optically anisotropic melt phase, and at least one surface of the film serves as an adhesive surface and adheres to the circuit forming surface of the substrate layer. And this adhesion surface shows the predetermined | prescribed hardness measured by the nanoindentation method. The hardness measurement method is described in detail in the following examples.

  The hardness of the adhesive surface needs to be 0.01 to 0.1 GPa, preferably about 0.015 to 0.095 GPa, more preferably, in order to adhere the substrate layer and the adhesive film layer well. It may be about 0.02 to 0.09 GPa.

  For the adhesive film layer, first, a thermoplastic liquid crystal polymer film is obtained in the same manner as described in the section of the substrate layer. In this case, as the thermoplastic liquid crystal polymer film, a film whose thermal expansion coefficient is controlled within a predetermined range may be used by heating after laminating with a metal foil, if necessary.

For example, the thermal expansion coefficient of the thermoplastic liquid crystal polymer film forming the adhesive film layer may be about 15 to 25 (× 10 ⁻⁶ cm / cm / ° C.), or 16 to 24 (× 10 ⁻⁶ cm). / Cm / ° C.). Further, the thermal expansion coefficient (α _b ) of the thermoplastic liquid crystal polymer film forming the substrate layer and the thermal expansion coefficient (α _a ) of the thermoplastic liquid crystal polymer film forming the adhesive polymer layer are approximately the same. -5 ≦ α _b −α _a ≦ 5 (× 10 ⁻⁶ cm / cm / ° C.), preferably −3 ≦ α _b −α _a ≦ 3 (× 10 ⁻⁶ cm / cm) / ° C).

  Further, the surface modification of the liquid crystal polymer film is performed so that the adhesive surface of the obtained thermoplastic liquid crystal polymer film exhibits a predetermined hardness. The surface modification method is not particularly limited as long as the adhesion surface of the liquid crystal polymer film can have a predetermined hardness, but is usually modified by physical polishing or ultraviolet irradiation. In the present invention, surface modification can be performed without using solution treatment or plasma treatment.

  Examples of physical polishing methods include brush polishing, blast polishing, belt polishing, barrel polishing, and the like, and the surface layer of the liquid crystal polymer film is removed by these polishings.

More specifically, in brush polishing, the surface of a liquid crystal polymer can be polished by rotating a brush of a wire rod such as a brass wire, nylon wire, or steel wire containing an abrasive at high speed and rubbing the processed surface of the liquid crystal polymer film. .
In blast polishing, the surface of the liquid crystal polymer can be polished by spraying a solid metal, mineral or vegetable abrasive on the processed surface of the liquid crystal polymer film at high speed together with compressed air.
In belt polishing, the surface of the liquid crystal polymer can be polished by rubbing a belt with an abrasive (endless belt sandpaper) against the processed surface of the liquid crystal polymer film.
In barrel polishing, the target object, abrasive and water are mixed and filled in the polishing tank, and the polishing tank is moved (rotated and vibrated). Can be polished.

By this polishing method, the hard skin layer (especially the surface skin layer) present on the surface of the liquid crystal polymer film can be removed, and the relatively soft core layer inside the liquid crystal polymer film can be exposed. Can be improved.
In physical polishing, it is preferable to remove a thickness of about 0.01 to 1 μm from the film surface, and more preferably, a surface layer may be removed with a thickness of about 0.1 to 0.9 μm.

  On the other hand, since the skin layer existing in the liquid crystal polymer film can be broken and the hardness of the film surface can be softened even by ultraviolet irradiation, the adhesiveness by thermocompression bonding can be improved. The ultraviolet irradiation is not particularly limited as long as a predetermined hardness can be imparted to the liquid crystal polymer film surface, but it is preferable to simultaneously irradiate ultraviolet rays having wavelengths of 185 nm and 254 nm.

  Further, from the viewpoint of promptly destroying only the surface layer, it is preferable to reduce the distance between the irradiation surface and the light source and to irradiate with high irradiation energy for a short time. For example, the distance between the irradiation surface and the light source may be about 0.3 cm to 5 cm, preferably about 0.4 to 2 cm. Moreover, although processing time can be suitably set according to the distance of an irradiation surface and a light source, it may be about 20 seconds-5 minutes, for example, Preferably it may be about 30 seconds-3 minutes.

  Moreover, since the surface of the adhesive film layer used in the present invention is softened so as to have a specific hardness, it is not necessary that the adhesive surface is roughened precisely, and the surface roughness of the adhesive surface ( Ra) may be, for example, less than 0.1 μm or may exceed 0.35 μm. Specifically, the surface roughness (Ra) of the adhesive surface may be, for example, 0.01 μm or more and less than 0.1 μm, preferably 0.03 μm or more and less than 0.08 μm. Further, the surface roughness (Ra) of the bonding surface is more than 0.35 μm and 1.0 μm or less, preferably more than 0.4 μm and 0.9 μm or less, more preferably 0.41 or more and 0.9 μm or less. May be.

  The thickness of the adhesive film layer can be appropriately set according to the lamination position used in the multilayer circuit board, but may be, for example, about 10 to 100 μm, preferably about 15 to 90 μm, and more preferably 20 It may be about ˜80 μm.

Moreover, when one side of the adhesive film layer adheres to the circuit board (for example, when used as a coverlay film or the like), the thickness of the adhesive film layer is about 1.5 to 5 times the thickness of the conductor circuit. It may be, and preferably about 2 to 4 times the thickness of the conductor circuit.
Further, when both surfaces of the adhesive film layer adhere to the circuit board (for example, when used as a bonding film), the thickness of the adhesive film layer is about 2.5 to 5 times the thickness of the conductor circuit. Preferably, it may be about 3 to 4 times the thickness of the conductor circuit.

  Moreover, in this invention, since the adhesive surface of the adhesive film layer is softened, the adhesiveness by thermocompression-bonding has improved. Therefore, even if the melting point of the adhesive film layer is increased, it is possible to adhere well to the substrate layer.

For example, in the multilayer circuit board, the melting point (Ta: ° C.) of the thermoplastic liquid crystal polymer forming the adhesive film layer and the melting point (Tb: ° C.) of the thermoplastic liquid crystal polymer forming the substrate layer are:
Ta ≦ Tb + 5 (for example, Tb−50 ≦ Ta ≦ Tb + 5) may be satisfied, preferably Ta ≦ Tb (for example, Tb−15 ≦ Ta ≦ Tb + 3), and more preferably Tb−10 ≦ Ta. ≦ Tb + 1 may be satisfied.

  When the thermoplastic liquid crystal polymer that forms the adhesive film layer and the thermoplastic liquid crystal polymer that forms the substrate layer have a specific melting point as described above, not only can the integrity as a multilayer circuit board be improved, but also the multilayer circuit Even when the substrate is exposed to a high temperature, thermal deformation of the low melting point polymer film can be prevented.

  Furthermore, the temperature for thermocompression bonding can be appropriately set according to the melting point of the adhesive polymer layer. For example, the temperature for thermocompression bonding is the melting point (Ta of the thermoplastic liquid crystal polymer forming the adhesive polymer layer). The temperature may be selected from the range of 15 ° C. lower than the temperature and 15 ° C. higher than the melting point.

  In addition, in the present invention, the surface layer of the adhesive polymer layer is softened to improve the adhesiveness. Therefore, even if the melting point between the thermoplastic liquid crystal polymers forming the adhesive polymer layer and the substrate layer is close, both are heated. It can be integrated by pressure bonding. For example, in such a case, the temperature of the thermocompression bonding is not less than 15 ° C. lower than the melting point (Ta: ° C.) of the thermoplastic liquid crystal polymer forming the adhesive polymer layer and not more than 15 ° C. higher than this melting point. Further, the temperature of the thermocompression bonding is selected from the range, and the temperature is 20 ° C. or more lower than the melting point (Tb: ° C.) of the thermoplastic liquid crystal polymer forming the substrate layer, and 10 ° C. or higher. May be satisfied.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this Example. In the following examples and comparative examples, various physical properties were measured by the following methods.

(Coefficient of thermal expansion)
The thermal expansion coefficient α is a coefficient obtained by dividing the expansion coefficient when heated at a constant heating rate from room temperature to near the heat distortion temperature of the film by the temperature difference, and is calculated as follows.
First, using a known thermomechanical analyzer, one end of a strip cut film is fixed, a tensile load is applied to the other end, and the amount of expansion when heated at a constant temperature increase rate is measured. Thermal expansion, assuming that the length L ₀ (mm) of the film in the load direction of the film is L ₁ (mm), the temperature is T ₂ (° C.), and the room temperature is T ₁ (° C.). The coefficient α can be calculated by the following formula.
α = [(L ₁ −L ₀ ) / (T ₂ −T ₁ ) / L ₀ (× 10 ⁻⁶ cm / cm / ° C.)
In the present invention, L ₀ = 20 mm, T ₂ = 150 ° C., T ₁ = 25 ° C., and the tensile load is 1 g.

(Melting point)
The film was obtained by observing the thermal behavior of the film using a differential scanning calorimeter. That is, after the thermoplastic liquid crystal polymer film is heated at a rate of 10 ° C./min to be completely melted, the melt is rapidly cooled to 50 ° C. at a rate of 10 ° C./min, and again at a rate of 10 ° C./min. The position of the endothermic peak that appears when the temperature was raised was recorded as the melting point.

(Hardness by nanoindentation method)
Sample fragments (1 cm in length × 1 cm in width) were collected from a thermoplastic liquid crystal polymer film that had undergone a softening step used as an adhesive film layer in Examples described later, and the hardness was measured using a nanoindentation method. The nanoindentation method is a method of obtaining a load-displacement curve by pushing a diamond indenter of an atomic microscope directly onto a sample surface, measuring an indentation depth with nanometer accuracy. Using JSPM 4200 manufactured by JEOL as an atomic force microscope, TriboScope manufactured by Hystron as a nanoindentation device, and a regular triangular pyramid (Birkovic type) indenter manufactured by Hystron as a diamond indenter (142.3 °), the maximum set load is set. A load speed of 80 μN / s and a load displacement curve were measured at 400 μN. The hardness [GPa] is obtained by dividing the maximum load by the contact projected area of the depression pushed in by the indenter. A sample was randomly measured 18 times, and the average value was used as the hardness of the film surface.

(thickness)
For the thermoplastic liquid crystal polymer film forming the adhesive polymer layer, the thickness of the film before and after being subjected to the softening process was measured using a Digimatic indicator manufactured by Mitutoyo Corporation. Measurement was performed by collecting sample pieces (length 50 cm × width 50 cm) from the film before and after being subjected to the softening process, measuring 100 points at random for each sample, and using the average value as the film thickness. .

(Measurement of surface roughness (Ra) of adhesive surface)
The roughness Ra of the liquid crystal polymer surface after the softening step (average value of absolute value deviation from the average line) was measured five times with Surf Test SJ-400 (manufactured by Mitutoyo Corporation), and the average value was used for adhesion. The surface roughness.

(Interlayer adhesion)
The wiring board was punched into a 10 mm strip and used as a test piece. After the adhesion interface of this test piece was brought out, it was peeled off at a speed of 5 cm / min in the 90 ° direction at room temperature, and the peeling load was measured using a digital force gauge manufactured by Nidec Sympo Co., Ltd. The average value of the load at the time of peeling was taken. However, the blurring of the measured values at the start and end of the measurement was not used when calculating the average value.

(Solder resistance)
The wiring board was cut into 30 × 30 mm to obtain a test piece. This test piece was immersed in a solder bath at 260 ° C. for 1 minute, and the deformation, foaming, and blistering of the test piece were visually observed.

(Dimensional change rate)
It was measured according to IPC-TM-650 2.2.4.

(Reference Example 1)
A thermoplastic liquid crystal polymer having a melting point of 280 ° C. is melt-extruded with a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 73/27). A film having a film thickness of 50 μm and a melting point of 280 ° C. was obtained by an inflation film forming method while controlling. A laminate of a metal foil / film / metal foil combination is applied to this film using a 18 μm thick copper foil (1/2 ounce copper foil by electrolysis) as a metal foil and thermocompression bonding at 290 ° C. 20 bodies were obtained at the same time.

A film obtained by removing the copper foil from the laminate with a ferric chloride solution is referred to as film A. As a result of measuring the thermal expansion coefficient, it was 18 × 10 ⁻⁶ cm / cm / ° C. Moreover, about the said laminated body, what exposed 100 lines of 100 micrometers width circuits and 200 micrometers pitch, removed copper foil other than an exposed part in a ferric chloride solution, and formed the wiring pattern is used as the circuit board B. .

(Reference Example 2)
A thermoplastic liquid crystal polymer having a melting point of 325 ° C., which is a copolymer of 6-hydroxy-2-naphthoic acid, hydroquinone, and 2,6-naphthalenedicarboxylic acid (molar ratio: 60/20/20) is melt extruded. A film having a film thickness of 50 μm and a melting point of 325 ° C. was obtained by an inflation film molding method while controlling the horizontal stretching ratio. A laminate of a metal foil / film / metal foil combination is applied to this film using a 18 μm-thick copper foil (1/2 ounce copper foil by electrolysis) as a metal foil by thermocompression bonding at 330 ° C. 20 bodies were obtained at the same time.

A film obtained by removing the copper foil from the laminate with a ferric chloride solution is referred to as film C. As a result of measuring the thermal expansion coefficient, it was 18 × 10 ⁻⁶ cm / cm / ° C. Moreover, about the said laminated body, what exposed 100 lines of 100 micrometers circuits and 200 micrometers pitch, removed copper foil other than an exposed part in a ferric chloride solution, and formed the wiring pattern is used as the circuit board D. .

Example 1
The film A was subjected to high-speed rotational polishing on one surface at a rotational speed of 2000 rpm and a film conveyance speed of 1 m / min, using 1000 mesh buffalo in which silicon carbide abrasive material was adhered to nylon fibers. The surface of film A, which had a film thickness of 49.7 μm before polishing, was removed, and the film thickness of the film after polishing was 49.2 μm. Further, the hardness of the polished film surface by a nanoindentation method was 0.08 Gpa.
Using two polished films, each polished surface is brought into contact with the conductor circuit of the circuit board B, and laminated in the order of polishing film / circuit board B / polishing film. A multilayer wiring board was obtained by pressing at a pressure of 0.0 MPa. Table 7 shows the interlayer adhesion, solder resistance and dimensional stability of the obtained multilayer wiring board.

(Example 2)
The film A was subjected to high-speed rotary polishing under the same baffle and polishing conditions as in Example 1. The surface of the film A having a film thickness of 50.1 μm was removed, and the film thickness became 49.5 μm. Moreover, it was 0.06 Gpa when the hardness of the film surface was measured.
Using two polished films, each polished surface is brought into contact with the conductor circuit of the circuit board D and laminated in the order of polishing film / circuit board D / polishing film. A multilayer wiring board was obtained by pressing at a pressure of 0.0 MPa. Table 7 shows the interlayer adhesion, solder resistance and dimensional stability of the obtained multilayer wiring board.

(Example 3)
The film C was subjected to high-speed rotary polishing under the same baffle and polishing conditions as in Example 1. The surface of the film C having a film thickness of 49.8 μm was removed, and the film thickness became 49.0 μm. Moreover, it was 0.09 Gpa when the hardness of the film surface was measured.
Using two polished films, each polished surface is brought into contact with the conductor circuit of the circuit board D and laminated in the order of polishing film / circuit board D / polishing film, and 315 ° C., 4.0 MPa by precision press. A multilayer wiring board was obtained by pressing at a pressure of Table 7 shows the interlayer adhesion, solder resistance and dimensional stability of the obtained multilayer wiring board.

( Reference Example 4)
Film A was irradiated for 1 minute at a distance of 1 cm between the light source and the irradiated surface from a synthetic quartz lamp that irradiates ultraviolet rays of 185 nm and 254 nm using Sen Engineering Co., Ltd. optical surface treatment apparatus. The surface hardness of the irradiated film was 0.05 Gpa.
Using two irradiated films, each irradiated surface is brought into contact with the conductor circuit of the circuit board B and laminated in the order of irradiated film / circuit board B / irradiated film. A multilayer wiring board was obtained by pressing at a pressure of 0.0 MPa. Table 7 shows the interlayer adhesion, solder resistance and dimensional stability of the obtained multilayer wiring board.

(Comparative Example 1)
The film A was subjected to high-speed rotational polishing using a 2500 mesh buffalo with silicon carbide abrasive adhered to nylon fibers at a rotation speed of 1000 rpm and a film conveyance speed of 1 m / min. When the surface of film A having a film thickness of 49.8 μm was observed with an optical microscope, polishing marks were observed, but the film thickness was not changed from 49.8 μm. Moreover, it was 0.53 Gpa when the hardness of the film surface which grind | polished was measured.
Using two polished films, each polished surface is brought into contact with the conductor circuit of the circuit board B, and laminated in the order of polishing film / circuit board B / polishing film. A multilayer wiring board was obtained by pressing at a pressure of 0.0 MPa. Table 7 shows the interlayer adhesion, solder resistance and dimensional stability of the obtained multilayer wiring board.

(Comparative Example 2)
Using the film A as it is, the circuit board B was laminated between two films A, and the whole was pressed with a precision press at 270 ° C. and a pressure of 4.0 MPa to obtain a multilayer wiring board. In addition, when the hardness of the surface before the press of the film A was measured, it was 0.60 Gpa. Table 7 shows the interlayer adhesion, solder resistance and dimensional stability of the obtained multilayer wiring board.

(Comparative Example 3)
A circuit board D was laminated between two films C, and pressed with a precision press at 315 ° C. and a pressure of 4.0 MPa to obtain a multilayer wiring board. Moreover, it was 0.46 Gpa when the hardness of the surface before the press of the film C was measured. Table 7 shows the interlayer adhesion, solder resistance and dimensional stability of the obtained multilayer wiring board.

As shown in Table 7, in Examples 1 to 3, since the film surface was removed by physical polishing, the hardness of the film surface was softened. In Reference Example 4, the film surface was softened by ultraviolet irradiation. As a result, in Examples 1 to 3 and Reference Example 4, not only the interlayer adhesion in the multilayer circuit board showed a high value, but also the solder resistance could be improved by bonding by thermocompression bonding. Furthermore, these multilayer circuit boards were also excellent in dimensional stability. In particular, in Examples 1 and 3 and Reference Example 4, although the films forming the adhesive film layer and the substrate layer have the same melting point, they exhibit high interlayer adhesion, solder resistance and dimensional stability. The property was also excellent. In Examples 1 to 3 and Reference Example 4, the adhesive surface of the film did not necessarily have dense irregularities, but the interlayer adhesion in the multilayer circuit board was high.

  On the other hand, in Comparative Example 1, since the physical polishing was performed only slightly, the film surface could not be softened. Moreover, also in Comparative Examples 2 and 3 using the film as it was, the hardness of the film surface showed a high value. The obtained multilayer circuit board is not only inferior in interlayer adhesion in the multilayer circuit board, but also has insufficient solder resistance and dimensional stability.

  As described above, the preferred embodiments of the present invention have been described with reference to the drawings. However, various additions, modifications, or deletions can be made without departing from the spirit of the present invention, and these are also included in the present invention. It is included in the range.

10, 20, 30 ... multilayer circuit boards 11, 21, 23 ... substrate layers 12, 22, 24, 32, 34 ... conductor circuit 13 ... adhesive film layers 13a25a, 25b, 26a, 33a, 35a ... adhesive surfaces 25 ... first 1 adhesive film layer (or bonding film)
26 ... Second adhesive film layer (or coverlay film)
33 ... third adhesive film layer 35 ... fourth adhesive film layer 35b ... non-adhesive surface

Claims (9)

  The surface of the thermoplastic liquid crystal polymer film was softened by removing a thickness of 0.01 to 1 μm from the film surface to form an adhesive surface of the thermoplastic liquid crystal polymer film, and measured by a nanoindentation method. An adhesive thermoplastic liquid crystal polymer film having a surface hardness in the range of 0.01 to 0.1 GPa.   2. The adhesive thermoplastic liquid crystal polymer film according to claim 1, wherein the surface roughness Ra of the film adhesion surface after the softening treatment is more than 0.35 μm and not more than 0.9 μm.   3. The adhesive thermoplastic liquid crystal polymer film according to claim 2, wherein the surface layer of the thermoplastic liquid crystal polymer film is removed by brush polishing or belt polishing. A substrate layer having a conductor circuit formed on at least one surface of a thermoplastic liquid crystal polymer film forming an optically anisotropic molten phase;
An adhesive film layer that is thermocompression-bonded with the adhesive surface facing the circuit forming surface of the substrate layer;
A multilayer circuit board comprising at least
The multilayer circuit board whose said adhesive film layer is the adhesive thermoplastic liquid crystal polymer film as described in any one of Claims 1-3 . 5. The multilayer circuit board according to claim 4 , wherein the thickness of the adhesive film layer is 2 to 5 times the thickness of the conductor circuit. It is a manufacturing method of a multilayer circuit board, Comprising: The adhesive surface of the adhesive film as described in any one of Claims 1-3 WHEREIN: The thermoplastic liquid crystal polymer film which forms an optically anisotropic melt phase at least A method for manufacturing a multilayer circuit board, comprising: a thermocompression bonding process in which a circuit having a conductor circuit formed on one surface is opposed to a circuit formation surface and the whole is bonded by thermocompression bonding. 7. The method for producing a multilayer circuit board according to claim 6 , wherein the thermoplastic liquid crystal polymer forming the adhesive film layer has a melting point (Ta: ° C.) and the thermoplastic liquid crystal polymer forming the substrate layer has a melting point (Tb: ° C.). Ta ≦ Tb + 5
The manufacturing method of the multilayer circuit board which satisfy | fills. The method of manufacturing a multilayer circuit board according to claim 6 or 7, the adhesive film layer, the cover lay film and a manufacturing method of the multilayer circuit board is at least one selected from the group consisting of bonding film. A multilayer circuit board obtained by the manufacturing method according to any one of claims 6 to 8 .

Images