JP2010238990A - Compound adhesive film, multi-layer circuit substrate using the same, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound adhesive film which excels in a heat resistance, fillability into between circuit wiring, and insulation reliability and is suitable to manufacture of a multi-layer circuit substrate. <P>SOLUTION: The compound adhesive film 10 has a polyimide resin layer 1 which is 5 to 200 μm in thickness and is 300°C or higher in thermal deformation temperature T1 and liquid crystal polymer layers 2A, 2B, which are 5 to 50 μm in thickness and 200 to 280°C in thermal deformation temperature T2 and has a laminated layer structure, on whose both surfaces of the polyimide resin layer 1 liquid crystal polymer layers 2A, 2B are stuck together. The compound adhesive film 10 is used as an adhesive layer in a multi-layer circuit substrate on which a plurality of wiring substrates are laminated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a composite adhesive film having a polyimide resin layer and a liquid crystal polymer layer, a multilayer circuit board using the same, and a method for producing the same.

  In recent years, with the reduction in size and weight of electrical devices, there has been a demand for higher density circuit wiring. In order to increase the density of circuit wiring, a multilayer circuit board in which a plurality of wiring boards are stacked and integrated has been put into practical use. A common method for producing a multilayer circuit board is to prepare a plurality of wiring boards on which circuit patterns are formed and to bond them together via an adhesive film. Conventionally, as an adhesive film used for such an application, for example, in Patent Document 1, an adhesive using a siloxane-modified polyimide resin is used because of its high heat resistance and excellent filling property between circuit wirings. A film has been proposed. For example, Patent Document 2 proposes to use a liquid crystal polymer film as an adhesive film by paying attention to its good filling property and high-frequency electrical characteristics.

  The siloxane-modified polyimide resin described in Patent Document 1 and the thermoplastic liquid crystal polymer film described in Patent Document 2 have good filling properties between wirings when heated and pressed, but the adhesive film easily deforms. For this reason, when a multilayer circuit board is used, the upper and lower circuit wirings through the adhesive film may come close to or come into contact with each other, and the insulation may be impaired. Such a decrease in insulation is particularly likely to occur when the circuit board is multilayered and densified. Therefore, in order to respond to the recent circuit formation technology that is becoming more and more complicated than ever, it is desirable to provide a technology that improves insulation while ensuring sufficient filling in a multilayer circuit board. It was rare.

  Although not related to a multilayer circuit board, Patent Document 3 proposes an adhesive film in which a thermoplastic polyimide resin layer is provided as an adhesive layer on the surface of a highly heat-resistant polyimide resin layer. However, the adhesive film of Patent Document 3 is used as the base material for the purpose of enhancing the adhesiveness when the conductor layer is laminated on the base material (insulating layer) of the two-layer flexible printed board. Application as an adhesive film on a circuit board is not considered at all. Moreover, when the adhesive film of patent document 3 is applied as an adhesive film between wiring boards in a multilayer circuit board, an adhesive film provided with a thermoplastic polyimide resin layer can be expected to have good heat resistance, but between circuit wirings. There is a concern that the filling property may not be sufficient, and a space is generated between the base material of the wiring board and the adhesive film, which may affect transmission characteristics, insulation reliability, durability, and the like of the multilayer circuit board.

  Patent Document 4 proposes an adhesive laminated film in which an epoxy resin layer is provided as an adhesive layer on the surface of a heat-resistant polyimide resin layer. However, an adhesive film provided with an epoxy resin layer as an adhesive layer is bonded by hardening of the epoxy resin, so it lacks flexibility, and the dielectric property (dielectric constant and dielectric loss tangent) of the epoxy resin is high, so the circuit It has drawbacks such as increased transmission loss of the substrate, and its use range is limited.

  It is also assumed that a thermoplastic resin other than the above is applied as the material of the adhesive layer, but a normal thermoplastic resin is not sufficiently satisfactory in terms of heat resistance.

Japanese Patent No. 3712606 JP-A-8-97565 JP 2006-316232 A JP 2006-116738 A

  An object of the present invention is to provide a composite adhesive film that is excellent in heat resistance, filling between circuit wiring, insulation reliability, and transmission characteristics, and suitable for use as an adhesive layer of a multilayer circuit board, and An object of the present invention is to provide a multilayer circuit board using the composite adhesive film.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problems can be solved by using a composite adhesive film in which a polyimide resin layer and a liquid crystal polymer layer are combined as an adhesive film for multilayer circuit wiring. The present invention has been completed.

That is, the composite adhesive film of the present invention is a composite adhesive film used as an adhesive layer in a multilayer circuit board in which a plurality of wiring boards are laminated,
A polyimide resin layer having a thickness in the range of 5 μm or more and 200 μm or less, and a thermal deformation temperature T1 of 300 ° C. or more;
A liquid crystal polymer layer having a thickness in the range of 5 μm or more and 50 μm or less and a thermal deformation temperature T2 in the range of 200 ° C. to 280 ° C .;
And having a laminated structure in which the liquid crystal polymer layer is bonded to both surfaces of the polyimide resin layer.

  In the composite adhesive film of the present invention, the surface roughness (Rz) of the polyimide resin layer on the side bonded to the liquid crystal polymer layer is preferably in the range of 0.5 to 5.0 μm.

A method for manufacturing a multilayer circuit board according to the present invention is a method for manufacturing a multilayer circuit board in which a plurality of wiring boards are laminated via an adhesive layer,
Preparing two or more wiring boards having a circuit pattern formed on the surface of an insulating base;
A step of arranging the circuit patterns formed on at least two of the wiring boards facing each other, and heating and pressurizing them together with the adhesive layer interposed therebetween; and
With
While using the composite adhesive film as the adhesive layer, the heating temperature T3 in the heating and pressurizing and bonding step is based on the thermal deformation temperature T1 of the polyimide resin layer and the thermal deformation temperature T2 of the liquid crystal polymer.
T2 + 10 ° C. ≦ T3 ≦ T2 + 60 ° C. (However, T3 <T1)
It has the relationship shown by this.

The multilayer circuit board of the present invention is a multilayer circuit board in which at least two wiring boards having a circuit pattern on the surface of an insulating base material are arranged with the surfaces on which the circuit pattern is formed facing each other, and are laminated via an adhesive layer. A circuit board,
The adhesive layer is
A polyimide resin layer having a thickness in the range of 5 μm or more and 200 μm or less, and a thermal deformation temperature T1 of 300 ° C. or more;
A liquid crystal polymer layer having a thickness in the range of 5 μm or more and 50 μm or less and a thermal deformation temperature T2 in the range of 200 ° C. to 280 ° C .;
And the liquid crystal polymer layer is laminated on both sides of the polyimide resin layer.

  The composite adhesive film of the present invention is excellent in heat resistance, has a good filling property between wirings of a wiring board, and is also excellent in insulation between wiring boards laminated via the composite adhesive film. Moreover, according to the composite adhesive film of the present invention, transmission loss in the high frequency region can be reduced. Therefore, high reliability can be imparted to the multilayer circuit board by using the composite adhesive film of the present invention as an adhesive layer.

It is sectional drawing of the composite adhesive film concerning embodiment of this invention. It is sectional drawing which shows the structural example of the polyimide resin layer in a composite adhesive film. It is drawing explaining the thermocompression bonding process at the time of manufacturing a composite adhesive film. It is sectional drawing of the multilayer circuit board concerning embodiment of this invention. It is drawing explaining the thermocompression-bonding process at the time of manufacturing a multilayer circuit board.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a cross-sectional view of a composite adhesive film 10 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of the configuration of the polyimide resin layer 1 in the composite adhesive film 10. Further, FIG. 3 shows a thermocompression bonding process when the composite adhesive film 10 is manufactured. The composite adhesive film 10 is a bonding sheet (bond ply) used as an adhesive layer of a multilayer circuit board. The composite adhesive film 10 includes a polyimide resin layer 1 as a core film and liquid crystal polymer layers 2A and 2B as adhesive films bonded to both surfaces of the polyimide resin layer 1. In the following description, the liquid crystal polymer layers 2A and 2B may be collectively referred to as the liquid crystal polymer layer 2 unless otherwise distinguished.

<Polyimide resin layer>
In the present invention, the resin constituting the polyimide resin layer 1 is a polyimide resin. Examples of the polyimide resin include a heat resistant resin composed of a polymer having an imide group in the structure such as polyimide, polyamideimide, polybenzimidazole, polyimide ester, polyetherimide, polysiloxaneimide and the like.

  The polyimide resin can be formed by imidizing (curing) the precursor polyamic acid.

  The polyamic acid can be produced by reacting a known diamine and an acid anhydride in the presence of a solvent. Examples of the diamine used include 4,4′-diaminodiphenyl ether, 2′-methoxy-4,4′-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, and 1,3-bis (4 -Aminophenoxy) benzene, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4 Examples include '-diaminobiphenyl and 4,4'-diaminobenzanilide.

  Examples of the acid anhydride include pyromellitic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride. Products, 4,4′-oxydiphthalic anhydride and the like.

  Each diamine and acid anhydride may be used alone or in combination of two or more. In addition, a polyimide resin is not limited to what is obtained from the said diamine and an acid anhydride.

  As a typical method for producing a polyimide film 11 (see FIG. 3) which is a material of the polyimide resin layer 1 from a polyamic acid which is a precursor of a polyimide resin, a tenter method and a casting method can be mentioned. The tenter method is a method in which a polyamic acid solution is cast on a rotating drum, peeled off from the rotating drum in the form of a gel film of polyamic acid, and heated and cured (imidized) in a tenter furnace to form a polyimide film 11. The casting method is a method in which a polyamide acid solution is applied to an arbitrary support substrate, dried, and then heat-treated to be cured (imidized) to form a polyimide film 11. The imidization can be performed, for example, by heating for a time within a range of 1 to 60 minutes under a temperature condition within a range of 80 to 400 ° C. The polyimide resin layer 1 can be blended with, for example, a lubricant, an antioxidant, a filler, and the like as long as the characteristics are not impaired.

  When the polyimide resin layer 1 is composed of a single layer of polyimide resin, a non-thermoplastic polyimide resin can be preferably used. It is preferable to apply such a polyimide resin as the polyimide resin layer 1 that is a core film in a multilayer circuit board because sufficient insulation between the stacked wirings can be secured.

As the non-thermoplastic polyimide resin, a polyimide resin having a structural unit represented by the general formula (1) is preferable. In General Formula (1), Ar ₁ represents a tetravalent aromatic group represented by Formula (2) or Formula (3), and Ar ₂ represents a divalent group represented by Formula (4) or Formula (5). R ₁ independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group, and X and Y independently represent a single bond or a divalent hydrocarbon having 1 to 15 carbon atoms. A divalent group selected from a group, O, S, CO, SO, SO ₂ or CONH, n ₁ independently represents an integer of 0 to 4, q represents an abundance ratio of structural units, and 0. A value of 1 to 1.0.

  The structural unit may be present in the homopolymer or may be present as a structural unit of the copolymer. In the case of a copolymer having a plurality of structural units, it may exist as a block copolymer or a random copolymer.

  When the polyimide resin layer 1 is formed of a non-thermoplastic polyimide resin, for example, Kapton EN, Kapton H, Kapton V (all trade names) manufactured by Toray DuPont Co., Ltd. Name) and commercially available polyimide films such as Upilex S (trade name) manufactured by Ube Industries, Ltd. can be used.

  For the polyimide resin layer 1, a thermoplastic polyimide resin can be used in combination with the non-thermoplastic polyimide resin. That is, when the polyimide resin layer 1 has a multilayer structure, the thermoplastic polyimide resin layer can be laminated on the non-thermoplastic polyimide resin layer. FIG. 2 shows an example in which the polyimide resin layer 1 has a three-layer structure. In this case, a non-thermoplastic polyimide resin layer 1A and thermoplastic polyimide resin layers 1B and 1C laminated on both surfaces of the non-thermoplastic polyimide resin layer 1A are provided. In the polyimide resin layer 1 having the configuration shown in FIG. 2, the thermoplastic polyimide resin layers 1B and 1C have excellent adhesiveness, so that the liquid crystal polymer layer 2A is maintained while maintaining the properties as the core film in the composite adhesive film 10. And the adhesiveness with 2B can be improved.

As a precursor used for a thermoplastic polyimide resin, a precursor having a structural unit represented by the general formula (6) is preferable. In General Formula (6), Ar ₃ represents a divalent aromatic group represented by Formula (7), Formula (8), or Formula (9), and Ar ₄ represents Formula (10) or Formula (11). Represents a tetravalent aromatic group, R ₂ independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, and V and W independently represent a single bond or 1 to 15 carbon atoms. A divalent hydrocarbon group, a divalent group selected from O, S, CO, SO ₂ or CONH, m ₁ independently represents an integer of 0 to 4, and p represents a molar ratio of constituent units; The value of 0.1 to 1.0.

  The thickness of the polyimide resin layer 1 is preferably within a range of 5 μm to 200 μm, and more preferably within a range of 10 μm to 50 μm.

  The thermal deformation temperature T1 of the polyimide resin layer 1 is that the wirings are in contact with each other even when bending stress or heat necessary for processing electronic components is applied to a multilayer circuit board in which a plurality of wirings are laminated. In order to prevent and ensure insulation, the temperature is preferably 300 ° C. or higher, and more preferably in the range of 300 ° C. or higher and 450 ° C. or lower. The thermal deformation temperature T1 of the polyimide resin layer 1 is the length of the test piece under the condition of a temperature rising rate of 5 ° C./min while applying a predetermined load using a thermomechanical analyzer as shown in Examples below. The amount of thermal expansion in the vertical direction can be measured and obtained from the temperature at the inflection point.

  In the composite adhesive film 10, the roughness (Rz; maximum height) of the surface S 1 of the polyimide film 11 bonded to the liquid crystal polymer layer 2 is 0 in order to enhance the adhesion between the polyimide resin layer 1 and the liquid crystal polymer layer 2. It is preferably within a range of 5 μm or more and 5.0 μm or less, and more preferably within a range of 0.7 μm or more and 2.0 μm or less. In order to adjust the Rz of the surface S1 of the polyimide film 11 to the above range, for example, embossing roll processing, UV treatment, plasma treatment, and after forming a film on a support substrate having Rz in the above range, the support substrate is formed. A method of peeling is effective. Further, for example, by removing a metal layer of a metal-polyimide laminate such as a commercially available copper-clad laminate (CCL) by etching, the polyimide film 11 having Rz of the surface S1 within the above range can be obtained. In addition, Rz can be measured according to JIS B 0601 as shown in the below-mentioned Example.

<Liquid crystal polymer layer>
The liquid crystal polymer that is the raw material of the liquid crystal polymer layer 2 is defined as a polymer that forms an optically anisotropic melt phase. The liquid crystal polymer is not particularly limited, and examples thereof include known thermotropic liquid crystal polyesters and thermotropic liquid crystal polyester amides derived from the compounds (1) to (4) listed below and derivatives thereof. be able to.
(1) Aromatic or aliphatic dihydroxy compounds (2) Aromatic or aliphatic dicarboxylic acids (3) Aromatic hydroxycarboxylic acids (4) Aromatic diamines, aromatic hydroxyamines or aromatic aminocarboxylic acids

Among the liquid crystal polymers obtained from these raw material compounds, aromatic liquid crystal polymers that do not contain an aliphatic chain in the molecule are preferred. As a typical example of such a liquid crystal polymer, a copolymer having a structural unit represented by the following formula obtained using 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid as raw materials can be given. Incidentally, m ₂ and n ₂ in the formula is a positive number indicating the presence molar ratio of the respective structural units.

  The liquid crystal polymer preferably has a transition temperature to an optically anisotropic melt phase in the range of 200 to 400 ° C., particularly in the range of 250 to 350 ° C. in terms of heat resistance and workability. Further, the liquid crystal polymer layer 2 may be blended with, for example, a lubricant, an antioxidant, a filler, and the like as long as the characteristics are not impaired. The liquid crystal polymer material may be the same or different between the liquid crystal polymer layer 2A and the liquid crystal polymer layer 2B.

  The liquid crystal polymer films 22A and 22B (see FIG. 3) used for forming the liquid crystal polymer layer 2 can be manufactured by an extrusion method represented by, for example, a T-die method, a laminate stretching method, an inflation method, and the like. In the inflation method and the laminate stretching method, stress is applied not only in the mechanical axis direction of the film (MD direction) but also in the direction perpendicular to this (TD direction), so the balance of mechanical properties in the MD and TD directions. A good film is obtained.

  The thickness of the liquid crystal polymer layer 2 is preferably set to be equal to or greater than the thickness of the wiring layer in the multilayer circuit board in order to obtain a good filling property between the wirings. For example, the thickness is preferably in the range of 5 μm to 50 μm. In the range of 7 μm to 35 μm is more preferable. Further, the thickness t2 of the liquid crystal polymer layer 2 is preferably thinner than the thickness t1 of the polyimide resin layer 1 even within the above range. The film thicknesses of the liquid crystal polymer layer 2A and the liquid crystal polymer layer 2B may be the same or different as long as they are within the above range.

  Further, the heat distortion temperature T2 of the liquid crystal polymer layer 2 is 200 ° C. or higher and 280 ° C. or lower in order to ensure heat resistance of the multilayer circuit board and to obtain sufficient filling property between the wirings patterned in the uneven shape. It is preferable to set it within the range of 220 ° C. or higher and 260 ° C. or lower. The thermal deformation temperature T2 of the liquid crystal polymer layer 2 can be measured by the same method as the thermal deformation temperature T1 of the polyimide resin layer 1.

  In the composite adhesive film 10, in order to improve the adhesion between the polyimide resin layer 1 and the liquid crystal polymer layer 2, not only the Rz of the surface S 1 of the polyimide resin layer 1 but also the liquid crystal polymer film on the side to be bonded to the polyimide resin layer 1. The roughness (Rz) of the surface S2 of 22A and 22B is also preferably in the range of 0.5 to 5.0 μm, and more preferably in the range of 0.7 to 2.0 μm. In order to adjust the Rz of the surface S2 of the liquid crystal polymer films 22A and 22B to the above range, for example, embossing roll processing, UV treatment, plasma treatment, and after forming the film on a support substrate having Rz in the above range, the support is performed. It is effective to perform a method of peeling the substrate. In addition, for example, by removing a metal layer of a metal-liquid crystal polymer laminate such as a commercially available copper clad laminate (CCL) by etching, liquid crystal polymer films 22A and 22B having Rz of the surface S2 within the above range are obtained. Can do. In addition, Rz of surface S2 of liquid crystal polymer film 22A, 22B can be measured according to JISB0601 as shown in the postscript Example.

  Commercially available products may be used as the liquid crystal polymer films 22A and 22B for forming the liquid crystal polymer layer 2, for example, Kuraray Co., Ltd. Bexter (registered trademark) may be used.

<Manufacture of composite adhesive film>
As shown in FIG. 3, the composite adhesive film 10 of the present embodiment has the liquid crystal polymer films 22 </ b> A and 22 </ b> B that become the liquid crystal polymer layer 2 disposed on both sides of the polyimide film 11 that becomes the polyimide resin layer 1 and is heated. It can be manufactured by applying pressure in the direction indicated by the arrow in the figure and bonding them together. The heating temperature T when the polyimide film 11 and the liquid crystal polymer films 22A and 22B are thermocompression bonded is based on the thermal deformation temperature T1 of the polyimide film 11 and the thermal deformation temperature T2 of the liquid crystal polymer films 22A and 22B.
T2 + 10 ° C. ≦ T ≦ T2 + 60 ° C. (where T <T1)
It is preferable to set to a temperature range having the relationship represented by. By setting the heating temperature T in the above temperature range, the liquid crystal polymer can be in a sufficiently molten state during thermocompression bonding, and between the polyimide resin layer 1 and the liquid crystal polymer layer 2 in the composite adhesive film 10. High adhesion can be obtained.

  Moreover, as a pressure at the time of bonding the polyimide film 11 and liquid crystal polymer film 22A, 22B, in order to acquire sufficient adhesiveness, the inside of the range of 1 MPa or more and 10 MPa or less is preferable, and the inside of the range of 3 MPa or more and 8 MPa or less is more. preferable.

  When the polyimide film 11 and the liquid crystal polymer films 22A and 22B are subjected to thermocompression bonding, it is preferable to pressurize after preheating for a predetermined time using a hot press apparatus. Sufficient adhesion between the polyimide resin layer 1 and the liquid crystal polymer layer can be obtained by performing pressurization for a predetermined time while the liquid crystal polymer films 22A and 22B are sufficiently softened by the preheating.

  The composite adhesive film 10 having the above configuration can have various shapes such as a cut sheet shape and a roll shape. In order to obtain high productivity, it is efficient to use a roll-like form formed in a long form, and a form that can be continuously produced and used by a roll-to-roll system, for example.

<Multilayer circuit board>
Next, a multilayer circuit board according to an embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view illustrating a configuration example of the multilayer circuit board 100, and FIG. 5 is a diagram illustrating a thermocompression bonding process when the multilayer circuit board 100 is manufactured. The multilayer circuit board 100 is laminated with the composite adhesive film 10 as an adhesive layer interposed therebetween so that the circuit patterns of the first wiring board 30A and the second wiring board 30B face each other. . The first wiring board 30A and the second wiring board 30B have wirings 4A and 4B formed in a predetermined pattern on the base materials 3A and 3B, respectively. For example, a polyimide film can be used as the base materials 3A and 3B. In addition, in the base materials 3A and 3B, a conductor layer or a patterned wiring may be formed on the surface opposite to the surface on which the wirings 4A and 4B are formed. The patterned wirings 4A and 4B are covered so as to be buried in the liquid crystal polymer layers 2A and 2B of the composite adhesive film 10.

  FIG. 4 shows a state in which two layers of wiring boards, the first wiring board 30A and the second wiring board 30B, are stacked, but three or more layers may be stacked. In FIG. 4, the first wiring board 30A and the second wiring board 30B are shown as the same structure that is vertically symmetrical, but wiring boards having different structures may be used.

The multilayer circuit board 100 having the above configuration has the following features by interposing the composite adhesive film 10 between the first wiring board 30A and the second wiring board 30B.
(1) The thermoplastic liquid crystal polymer layer 2 formed on both surfaces of the composite adhesive film 10 ensures sufficient adhesion between the first wiring board 30A and the second wiring board 30B. Further, between the liquid crystal polymer layer 2 and the polyimide resin layer 1, the roughness of the surface S1 of the polyimide film 11 (and preferably the surface S2 of the liquid crystal polymer films 22A and 22B), which is the material of the polyimide resin layer 1, is adjusted. By further preserving, higher adhesiveness can be obtained. Therefore, high adhesiveness is obtained between the first wiring board 30A and the second wiring board 30B laminated via the composite adhesive film 10, and peeling or the like hardly occurs, so that the entire multilayer circuit board 100 is highly integrated. And durability.

(2) Since the polyimide resin layer 1 which is the core film of the composite adhesive film 10 is mainly composed of a non-thermoplastic polyimide resin, it has higher rigidity and less thermal deformation than the liquid crystal polymer layer 2. Therefore, even when a strong stress is applied due to bending or the like, or when heat is applied, the wiring 4A of the first wiring board 30A and the wiring 4B of the second wiring board 30B are always interposed between the wirings. The insulation distance can be sufficiently secured.

(3) Since the liquid crystal polymer constituting the liquid crystal polymer layer 2 is easily deformable and has excellent shape followability, it is between the patterned wirings 4A of the first wiring board 30A and the second wiring board 30B. Are filled in between the patterned wirings 4B, and there is no gap. If there is a gap between adjacent wirings, the insulation between the wirings cannot be sufficiently secured, and there is a risk that the insulation and durability of the multilayer circuit board may be reduced. High reliability can be obtained. In addition, since the liquid crystal polymer having a low dielectric constant and dielectric loss tangent has excellent high frequency electrical characteristics, excellent transmission characteristics can be obtained in the wirings 4A and 4B.

<Manufacture of multilayer circuit boards>
As shown in FIG. 5, in the multilayer circuit board 100 of the present embodiment, the first wiring board 30A and the second wiring board 30B are arranged on both sides of the composite adhesive film 10 so that the wiring 4A and the wiring 4B face each other. It can be manufactured by pressing and bonding in the direction indicated by the arrow in the figure while arranging and heating. As the heating temperature T3 when the first wiring board 30A and the second wiring board 30B are thermocompression bonded to the composite adhesive film 10, the thermal deformation temperature T1 of the polyimide film 11 and the thermal deformation temperature T2 of the liquid crystal polymer films 22A and 22B. Based on
T2 + 10 ° C. ≦ T3 ≦ T2 + 60 ° C. (However, T3 <T1)
It is preferable to set to a temperature range having the relationship represented by. By setting the heating temperature T3 within the above temperature range, the liquid crystal polymer can be in a sufficiently molten state at the time of thermocompression bonding, and the liquid crystal polymer layer 2, the first wiring board 30A and the first wiring board 30A in the multilayer circuit board 100 can be obtained. High adhesiveness can be obtained between the two wiring boards 30B, and the liquid crystal polymer can be filled in a dense state with no gap between the wirings 4A-4A and between the wirings 4B-4B.

  Further, as the pressure when the first wiring board 30A and the second wiring board 30B are thermocompression-bonded to the composite adhesive film 10, the adhesiveness of the entire multilayer circuit board 100 is improved, and the wiring 4A-4A is used as described above. For the purpose of enhancing the filling property of the liquid crystal polymer between the wirings 4B and 4B, for example, it is preferably in the range of 1 MPa to 10 MPa, more preferably in the range of 3 MPa to 8 MPa.

  When the first wiring board 30A and the second wiring board 30B are thermocompression bonded to the composite adhesive film 10, it is preferable to pressurize after preheating for a predetermined time using a hot press apparatus. Sufficient adhesion between the liquid crystal polymer layer 2 and the first wiring substrate 30A and the second wiring substrate 30B by performing pressurization for a predetermined time while the liquid crystal polymer layer 2 is sufficiently softened by the preheating. Performance can be obtained, high integrity and adhesion can be imparted to the entire multilayer circuit board 100, and the liquid crystal polymer can be densely filled between the wirings. For example, the preheating time is preferably performed over the first heating time in the range of 1/5 to 4/5. In this case, the ratio of the pressurizing time to the total heating time can be a time within a range of 1/5 to 4/5. More specifically, for example, when the total heating time is 25 minutes, the preheating time can be in the range of 5 to 20 minutes, and the pressurization time can be in the range of 5 to 20 minutes.

  When manufacturing the multilayer circuit board 100, the first wiring board 30 </ b> A and the second wiring board 30 </ b> B may be simultaneously thermocompression bonded to both surfaces of the composite adhesive film 10. A method in which the first wiring board 30A is thermocompression bonded and then the second wiring board 30B is thermocompression bonded to the other surface of the composite adhesive film 10 may be employed.

  Further, for example, the liquid crystal polymer film 22A, the polyimide film 11 and the liquid crystal polymer film 22B are interposed between the first wiring substrate 30A and the second wiring substrate 30B in a single separated state, and once under the above conditions. It is also possible to manufacture the multilayer circuit board 100 by thermocompression bonding. Further, for example, the liquid crystal polymer film 22A, the polyimide film 11, the liquid crystal polymer film 22B, and the second wiring substrate 30B are sequentially laminated in a single state on the formation surface of the wiring 4A of the first wiring substrate 30A. By doing so, the multilayer circuit board 100 can be manufactured. Further, for example, the liquid crystal polymer film 22A is preliminarily bonded to the formation surface of the wiring 4A of the first wiring substrate 30A, and the liquid crystal polymer film 22B is preliminarily bonded to the formation surface of the wiring 4B of the second wiring substrate 30B. It is also possible to manufacture the multilayer circuit board 100 by arranging the polyimide film 11 between the liquid crystal polymer film surfaces of the wiring board with a polymer film and thermocompression bonding. The wiring formation surface of the wiring board and the liquid crystal polymer layer 2 (liquid crystal polymer films 22A and 22B) are in contact with each other, and the liquid crystal polymer layer 2 (liquid crystal polymer films 22A and 22B) and the polyimide resin layer 1 (polyimide film 11) are in contact with each other. The manufacturing method of the multilayer circuit board 100 is not limited to the method exemplified above as long as it is laminated so as to be in contact.

  The multilayer circuit board 100 can have various shapes such as a cut sheet shape and a roll shape. In order to obtain high productivity, it is efficient to use a roll-like form formed in a long form, and a form that can be continuously produced and used by a roll-to-roll system, for example.

  In the above description, only the characteristic steps of the method of the present invention have been described. That is, when a circuit wiring board is manufactured, processes other than those normally performed, for example, processes such as through-hole processing in the previous process, terminal plating in the subsequent process, and external processing can be performed according to a conventional method.

  The multilayer circuit board 100 obtained as described above can be suitably used for applications such as a flexible printed board, a rigid flex board, and a flexible transmission cable.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. Unless otherwise specified in the examples of the present invention, various measurements and evaluations are as follows.

[Measurement of heat distortion temperature]
Using a thermomechanical analyzer (manufactured by Bruker, 4000SA), heat in the length direction of the test piece under the conditions of a width of 2 mm, a length of 30 mm, a distance between chucks of 15 mm, a load of 2 g, and a heating rate of 5 ° C./min. The amount of expansion is measured, and the inflection point is defined as the heat distortion temperature.

[Measurement of surface roughness]
In accordance with JIS B 0601, Rz was measured under the condition of a measurement width of 200 μm using a stylus type surface roughness measuring device (manufactured by TENCOR, TENCOR P-10).

[Fillability (workability)]
The multilayer circuit board was cut in a direction perpendicular to the linear conductor pattern (wiring), and the cross section was evaluated by observing with a microscope. The case where the resin was densely packed around the conductor pattern without a gap was judged as “good”, and the case where a void partially existed around the conductor pattern was judged as “good”.

[Insulation reliability (dielectric breakdown voltage)]
In accordance with ASTM-D-149, the dielectric breakdown voltage of the adhesive film after the multilayer circuit board was produced (after pressurization and heating) was measured using a dielectric breakdown voltage measuring device (manufactured by KIKUSUI, TOS5051S).

[Transmission characteristics]
Using a cavity resonator (manufactured by Kanto Electronics Development Co., CP431) and a network analyzer (manufactured by Agilent Technologies, E8363B), the dielectric constant and dielectric loss tangent of the adhesive film at 1 GHz are measured by the cavity resonator perturbation method, Used as an alternative indicator of transmission characteristics.

[Productivity (lamination press time)]
For the composite adhesive film and the liquid crystal polymer film of the present invention, based on the results of examining the optimum conditions by changing the temperature, pressure and time, the filling between the wiring, the distance between the upper and lower circuit wiring (melting outflow), The lamination press time under the most preferable conditions was selected by comprehensively evaluating interlayer adhesion and the like. In addition, for the thermoplastic polyimide sheet (ESPANEX (registered trademark) SPB-035A, manufactured by Nippon Steel Chemical Co., Ltd.), the lamination press time under standard recommended conditions was used.

Reference Example 1: Preparation of polyimide film Polyimide copper-clad laminate (ESPANEX (registered trademark) M series, manufactured by Nippon Steel Chemical Co., Ltd.) double-sided copper foil as a commercially available etchant (Adeka Kermica FE-210, manufactured by ADEKA Corporation) Was completely etched to prepare a polyimide film A having a thickness of 25 μm. This polyimide film A had a surface roughness Rz of 1.5 μm and a heat distortion temperature of 330 ° C.

Reference Example 2: Preparation of liquid crystal polymer film Double-sided copper foil of liquid crystal polymer copper clad laminate (ESPANEX (registered trademark) L series, manufactured by Nippon Steel Chemical Co., Ltd.) was used as a commercially available etching solution (Adeka Kermica FE-210, ADEKA Corporation). The liquid crystal polymer film B having a thickness of 25 μm was prepared. The liquid crystal polymer film B had a surface roughness Rz of 1.5 μm and a heat distortion temperature of 250 ° C.

Reference Example 3: Fabrication of Wiring Substrate Forming a plurality of linear conductor patterns on a copper foil on one side of a polyimide copper clad laminate (ESPANEX (registered trademark) M series, manufactured by Nippon Steel Chemical Co., Ltd.) by a subtractive method Thus, a wiring board C was produced. The processing width of the linear conductor pattern was circuit conductor width / space width = 100 μm / 100 μm. For the etching, a commercially available etching solution (Adeka Kermica FE-210, manufactured by ADEKA Corporation) was used.

Example 1 Production of Composite Adhesive Film The liquid crystal polymer film B was laminated on both sides of the polyimide film A, and joined by heating and pressing with a precision flat plate press. The heating and pressurizing conditions were maintained at a temperature of 265 ° C. for about 10 minutes, then a pressure of 6 MPa was applied, and this state was maintained for 10 minutes. The obtained composite adhesive film had a polyimide resin layer and a liquid crystal polymer layer in close contact with each other, and had sufficient practicality as an adhesive film.

Example 2: Production of multilayer circuit board The above-mentioned wiring board C / composite adhesive film / wiring board C were laminated in this order, and joined by heating and pressing with a precision flat plate press to obtain a multilayer circuit board. The heating and pressurizing conditions were maintained at a temperature of 265 ° C. for about 10 minutes, then a pressure of 6 MPa was applied, and this state was maintained for 10 minutes. In this multilayer circuit board, the liquid crystal polymer was sufficiently filled around the conductor pattern, and the distance between the upper and lower conductor patterns was about 60 μm.

Comparative Example 1
In Example 2, instead of using a composite adhesive film, a thermoplastic polyimide sheet containing siloxane-containing polyimide resin (ESPANEX (registered trademark) SPB-035A, manufactured by Nippon Steel Chemical Co., Ltd.) was used, and a precision flat plate press apparatus Was used to maintain a heated and pressurized state at 180 ° C. and 4 MPa for about 60 minutes to produce a multilayer circuit board. When the cross section of the multilayer circuit board was observed with a microscope, a partial gap was confirmed between the conductor pattern and the thermoplastic polyimide resin. From this, compared with the multilayer circuit board of Example 2, there were concerns that the transmission characteristics and durability were inferior and the productivity was low.

Comparative Example 2
In Example 2, instead of using the composite adhesive film, a liquid crystal polymer film having a thickness of 25 μm was used and bonded by heating and pressing with a precision flat plate press apparatus to obtain a multilayer circuit board. The heating and pressurizing conditions were maintained at a temperature of 265 ° C. for about 10 minutes, then a pressure of 6 MPa was applied, and this state was maintained for 10 minutes. When the cross section of this multilayer circuit board was observed with a microscope, the conductor pattern was sufficiently filled with the liquid crystal polymer resin, but the upper and lower conductor patterns were partially in contact with each other due to the melt outflow of the liquid crystal polymer. Observed. From this, it was feared that the insulation reliability was inferior to that of the multilayer circuit board of Example 2.

  The multilayer circuit boards obtained in Example 2, Comparative Example 1 and Comparative Example 2 were evaluated for insulation reliability, transmission characteristics, and productivity. The results are shown in Table 1. In addition, the result about filling property was also described in Table 1.

  As shown in Table 1, in Comparative Example 1 using a single layer of thermoplastic polyimide as the adhesive layer, the lamination press time is as long as 60 minutes, and the productivity is inferior. Although there was, it was not satisfactory in terms of practicality. Moreover, in Comparative Example 2 using a single-layer liquid crystal polymer film as the adhesive layer, the dielectric breakdown voltage was small to a level where it could not be measured, and the insulation reliability was poor, and other evaluation items were good. However, it was not satisfactory in practical use. On the other hand, in Example 2 using the composite adhesive film of the present invention as the adhesive layer, a multilayer circuit board having excellent reliability in all evaluation items and a high reliability was obtained. Thus, by using the composite adhesive film of the present invention, it was possible to provide a multilayer circuit board excellent in interlayer adhesion, insulation reliability, transmission characteristics, durability, workability, and the like.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made.

  The composite adhesive film and the multilayer circuit board of the present invention have high utility value in the manufacture of electronic information equipment that is required to be downsized, reduced in weight, and enhanced in functionality.

  DESCRIPTION OF SYMBOLS 1 ... Polyimide resin layer, 1A ... Non-thermoplastic polyimide resin layer, 1B, 1C ... Thermoplastic polyimide resin layer, 2, 2A, 2B ... Liquid crystal polymer layer, 3A, 3B ... Base material, 4A, 4B ... Wiring, 10 ... Composite adhesive film, 11 ... polyimide film, 22A, 22B ... liquid crystal polymer film, 30A ... first wiring board, 30B ... second wiring board, 100 ... multilayer circuit board, S1, S2 ... surface

Claims (4)

A composite adhesive film used as an adhesive layer in a multilayer circuit board in which a plurality of wiring boards are laminated,
A polyimide resin layer having a thickness in the range of 5 μm or more and 200 μm or less, and a thermal deformation temperature T1 of 300 ° C. or more;
A liquid crystal polymer layer having a thickness in the range of 5 μm or more and 50 μm or less and a thermal deformation temperature T2 in the range of 200 ° C. to 280 ° C .;
And having a laminated structure in which the liquid crystal polymer layer is bonded to both surfaces of the polyimide resin layer.   The composite adhesive film according to claim 1, wherein the surface roughness (Rz) of the polyimide resin layer on the side bonded to the liquid crystal polymer layer is in the range of 0.5 to 5.0 μm. A method for manufacturing a multilayer circuit board in which a plurality of wiring boards are laminated via an adhesive layer,
Preparing two or more wiring boards having a circuit pattern formed on the surface of an insulating base;
Placing the circuit pattern-formed surfaces of the at least two wiring boards facing each other, and heating and pressurizing them together with the adhesive layer interposed therebetween; and
With
The composite adhesive film according to claim 1 or 2 is used as the adhesive layer, and the heating temperature T3 in the heating and pressurizing and bonding step is the heat deformation temperature T1 of the polyimide resin layer and the liquid crystal polymer. With reference to the heat distortion temperature T2,
T2 + 10 ° C. ≦ T3 ≦ T2 + 60 ° C. (However, T3 <T1)
A manufacturing method of a multilayer circuit board characterized by having the relationship shown in FIG. A multilayer circuit board in which at least two wiring boards having a circuit pattern on the surface of an insulating base material are arranged with the surfaces on which the circuit patterns are formed facing each other and stacked via an adhesive layer;
The adhesive layer is
A polyimide resin layer having a thickness in the range of 5 μm or more and 200 μm or less, and a thermal deformation temperature T1 of 300 ° C. or more;
A liquid crystal polymer layer having a thickness in the range of 5 μm or more and 50 μm or less and a thermal deformation temperature T2 in the range of 200 ° C. to 280 ° C .;
And a multilayer structure in which the liquid crystal polymer layer is bonded to both surfaces of the polyimide resin layer.

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