JP2010283390A - Circuit base material of multilayer circuit substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit base material suitable for manufacture of a multilayer circuit board including, as a cable part, a build-up layer by connection using a conductive projection. <P>SOLUTION: The circuit base material is composed of a metal foil having a plurality of conductive projections of ≥10 μm in height erected on at least one surface and an insulating resin layer having a multilayer structure laminated on the one surface of the metal foil and fixed in a state wherein the conductive projections penetrate it. The insulating resin layer of the circuit base has a low-thermal-expansion polyimide layer (a) of ≤30×10<SP>-6</SP>[1/K] in linear expansion coefficient of at least one layer, and an adhesive layer (b) positioned at an outermost layer from the metal foil and having a peel strength of ≥0.7 kN/m in peel strength when thermally applied to a copper foil having no conductive projection, and the linear expansion coefficient of the whole insulating resin layer is ≤35×10<SP>-6</SP>[1/K]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a circuit board of a multilayer circuit board, and more particularly to a circuit board of a multilayer circuit board in which layers are connected by conductive protrusions, and in particular, a multilayer circuit board having a flexible cable portion.

  In recent years, downsizing and higher functionality of electronic devices have been promoted more and more, and therefore, there is an increasing demand for higher density of circuit boards. In view of this, the circuit board is made to be a multi-layer circuit board from one side to both sides or three or more layers to increase the density of the circuit board.

  As a part of this, multilayer circuit boards such as a separate flexible board that constitutes the flexible cable part connecting the multilayer circuit boards, a multilayer flex rigid board integrated with a flexible flat cable, or a multilayer flexible board, Widely used mainly in small electronic devices such as mobile phones. A typical structure of this multilayer circuit board is a structure in which about 2 to 6 layers of multilayer core circuit boards having through-hole connections in the inner layer have 1 to 2 layers of build-up layers connected to via holes on both sides or one side. The cable portion by the flexible substrate is provided on the multilayer core circuit substrate or the build-up layer.

  Conventionally, a method of performing a plating process after opening by laser, NC drill, plasma etching, chemical etching, or the like has been adopted for interlayer connection of a multilayer core circuit board or buildup layer. However, it has the disadvantage that the yield of the plating process itself is poor and the process for conducting the insulating resin layer is complicated.

  This build-up layer is a component mounting part. For the purpose of improving the mounting density and wiring density, the electrical connection of the build-up layer is changed from a via hole connection by a conventional plating method, so-called printing bumps or plating by a conductive paste or plating. A method of replacing the connection with conductive protrusions such as metal bumps by etching has been developed.

  Patent Document 1 discloses a circuit substrate in which a plurality of conductive bumps (conductive protrusions) having a mountain-like longitudinal cross-sectional shape are formed on the surface of a metal plate, and an insulating sheet is provided on the metal plate. Yes.

  3 and 4 are process diagrams showing a method of manufacturing a multilayer circuit board using a build-up layer formed by connection using conductive protrusions as a cable portion according to a conventional method. When the multilayer circuit board is manufactured, as shown in FIG. 3A, the conductive protrusion 1 is formed on the copper foil 2 by a technique such as printing, etching, or plating.

  Next, as shown in FIG. 3 (2), a polyimide film 19 having thermoplastic polyimide on both sides is attached to the surface on which the conductive protrusions are erected by a press, a laminator or the like. Thereafter, as shown in FIG. 3 (3), polishing or the like is performed to expose the top of the conductive protrusion 1 from the polyimide film 19.

  At this time, there is no adhesive property of the thermoplastic polyimide, and the conductive protrusion 1 is stuck into the polyimide film 19. The base material 20 in which the conductive protrusion 1 penetrates the polyimide film 19 is obtained through the steps so far.

  3 (4) to 4 (2) show a method for manufacturing a multilayer core circuit board. A double-sided copper-clad laminate 7 as shown in FIG.

  Next, as shown in FIG. 3 (5), a conduction hole 8 is formed by a technique such as an NC drill or a mold. Thereafter, as shown in FIG. 3 (6), after conducting a treatment such as a conductive treatment or electroless plating, the electroplating 9 establishes conduction between both surfaces through the conduction hole 8.

  Next, as shown in FIG. 4A, a double-sided circuit 11 is formed by a conventional method. Subsequently, as shown in FIG. 4B, unnecessary portions of the substrate are punched out with a mold or the like. The multilayer core circuit board 13 is manufactured through the steps so far. Even when the number of layers constituting the substrate is increased, the substrate is basically manufactured by the same process.

  Next, as shown in FIG. 4 (3), base materials 21 and 22 in which conductive protrusions penetrate the polyimide film are laminated on the multilayer core circuit board 13. If necessary, the base material through which the conductive protrusion has penetrated the polyimide film is previously framed with a mold or the like and then laminated.

Thereafter, as shown in FIG. 4 (4), circuit patterns 23 and 24 are formed on the copper foil of the base material laminated by a conventional method. Further, the multilayer circuit board 18 is obtained by forming a cover film and a solder resist layer, electroless nickel, gold plating and the like by a conventional method.
JP-A-6-350258 JP 2002-141629 A JP-A-8-46321 JP-A-2-234494

  As described above, the build-up layer interlayer insulating material by connection using conductive protrusions is formed of a flexible polyimide film having an adhesive resin such as thermoplastic polyimide on both sides, and the build-up layer is formed. There is a structure to be a cable part.

  This structure is manufactured as a multilayer circuit board by laminating and pressing a base material having a structure in which conductive protrusions on a copper foil penetrate polyimide on a multilayer core circuit board prepared in advance.

  However, this multilayer circuit board has a problem that polyimide in a portion corresponding to a cable portion is not cut by a lamination press and adhesion between the polyimide and the copper foil may not be obtained. Furthermore, since the polyimide film cannot be directly penetrated by the connection using the conductive protrusions, as described in Patent Document 2, it is troublesome to perform a process such as polishing for exposing the top of the conductive protrusions. There is also a problem that is large.

  Further, Patent Document 3 describes a manufacturing method in which a polyimide film is punched in advance and a conductive protrusion is passed through only an adhesive layer.

  However, the drilling process is complicated and there are problems of alignment between the holes and the conductive protrusions, and the above problems have not been solved.

  In addition, in the case where the interlayer insulating material corresponding to the cable portion is formed of only a flexible thermoplastic resin, for example, thermoplastic polyimide, in addition to the above problem, the resin described in Patent Document 3 There is also a problem of running out.

  After all, penetration by conductive protrusions, adhesion to metal foil, heat resistance to high temperature bonding, dimensional stability for high density connection and high density mounting, and flexibility and flex resistance as a flexible substrate There is a problem that there is no appropriate insulating resin that satisfies the bending characteristics such as the above.

  From such a background, it is difficult for the conventional construction method to inexpensively and stably manufacture a multilayer circuit board having a circuit layer formed by connection using conductive protrusions as a cable portion.

  The present invention has been made in consideration of the above-described points, and an object thereof is to provide a circuit base material for a multilayer circuit board having a cable portion as a build-up layer or a core circuit layer by connection using conductive protrusions. To do.

  In order to achieve the above object, the present invention provides the following inventions.

According to the present invention, a metal foil in which a plurality of conductive protrusions having a height of 10 μm or more are erected on at least one surface and a metal foil laminated on the one surface of the metal foil and fixed in a state where the conductive protrusion penetrates. A circuit base material comprising an insulating resin layer having a layer structure, wherein the insulating resin layer has a low thermal expansion polyimide resin layer (a) having a linear expansion coefficient of at least one layer of 30 × 10 ⁻⁶ [1 / K] or less. And an adhesive layer (b) which is located on the outermost layer from the metal foil and does not have conductive protrusions, and an adhesive layer (b) which gives a peel strength of 0.7 kN / m or more when thermocompression bonded. The linear expansion coefficient of the entire layer is 35 × 10 ⁻⁶ [1 / K] or less.

  Due to these features, the present invention has the following effects.

  According to the present invention, since the polyimide resin having a low linear expansion coefficient is used for the insulating resin layer of the circuit substrate, a circuit substrate having no warpage and excellent dimensional stability can be obtained. In addition, since the outermost layer of the insulating resin layer is excellent in adhesion to metal, it can be used as a circuit base material that does not peel off from the metal, and is mainly used for a flexible cable portion of a multilayer circuit board. It is suitably used as a material.

  As a result, according to the present invention, a multilayer circuit board having a flexible cable portion in a buildup layer, which has been difficult with the conventional manufacturing method, can be stably provided at a low cost.

  First, an insulating resin layer having a multilayer structure used for the multilayer circuit board according to the present invention, that is, a core resin layer made of a polyimide resin having a compression elastic modulus of 15 GPa or more at a temperature of 250 ° C., and the conductive protrusion are brought into contact with each other. An insulating resin layer having a multilayer structure having an adhesive layer applied to the surface to be adhered will be described.

  Here, the core resin layer is a layer composed of a polyimide resin having a compressive elastic modulus at a temperature of 250 ° C. of 15 Gpa or more, and preferably has a linear expansion coefficient of 30 × 10 −6 [1 / K] or less. Say things. When the layer other than the adhesive layer is composed of two or more layers, the core resin layer is the thickest layer other than the adhesive layer.

The insulating resin layer is formed of two or more resin layers, at least one of which is a low thermal expansion polyimide resin layer (a) having a linear expansion coefficient of 30 × 10 ⁻⁶ [1 / K] or less, The outermost resin layer farthest from the metal foil having conductive protrusions is an adhesive layer (b) having a peel strength of 0.7 KN / m or more measured by thermocompression bonding with a copper foil having no conductive protrusions. ). Moreover, the measuring method of peel strength is based on the Example mentioned later.

  Therefore, the insulating resin layer of the base material in which the conductive protrusion for the multilayer circuit board of the present invention penetrates the insulating resin layer has at least two different types of resin layers. Preferably, all of the insulating resin layer is a polyimide resin layer, so that the insulating resin layer has high heat resistance and excellent dimensional stability without causing deterioration in characteristics when other resins are used as an adhesive layer. Can be formed.

  Here, the polyimide resin layer in the present invention refers to a resin layer containing a polymer having an imide bond in the molecule, and preferably means that the main component is composed of polyimide or polyamideimide. Examples of this type of polyimide resin include those described in Japanese Patent No. 2746555 and Japanese Patent No. 3034838.

  In the following description, the metal foil is a metal foil having conductive protrusions, and the a layer is a core resin layer made of a polyimide resin having a compressive elastic modulus of 15 Gpa or more, or has a linear expansion coefficient of 30 × 10 −6 [1. / K] represents a low thermal expansion polyimide resin layer (a) or less, and b layer represents an adhesive layer (b) having a peel strength of 0.7 KN / m or more. The α layer is an arbitrary insulating resin layer that is not limited.

  And when the structural example which added metal foil to the insulating resin layer used for this invention is shown, it is as following (i)-(iv).

(I) Metal foil / a layer / b layer (ii) Metal foil / α layer / a layer / b layer (iii) Metal foil / a layer / α layer / b layer (iv) Metal foil / α layer / a layer / Α layer / b layer FIG. 5 is a cross-sectional view of the circuit substrate according to (iv).

In the base material in which the conductive protrusion for the multilayer circuit board according to the present invention penetrates the insulating resin layer, the thickness of the low thermal expansion polyimide resin layer (a) is 40 with respect to the total thickness of the insulating resin layer. It is preferable to make it into the range of -80%. Further, the thickness of the adhesive layer _{(b t)} and the thickness of the low thermal expansion polyimide resin layer _{(a t)} and the thickness ratio of _{(b t / a t) b} t / a t is 0.05 Is preferably in the range of .7.

By setting the thickness in this way, the low thermal expansion property of the entire insulating resin layer can be maintained, and the balance with the adhesive properties is improved. The low thermal expansion polyimide resin layer (a) of the insulating resin layer needs to have a linear expansion coefficient of 30 × 10 ⁻⁶ [1 / K] or less because of problems such as warpage of the multilayer circuit board and handling in the process. And As such a polyimide resin exhibiting low thermal expansion, those containing 80 mol% or more of a polyimide structural unit represented by the following general formula (1) are preferable.

Here, R ₁ in the formula is a group represented by the following formula (2) or (3), and R ₂ is represented by the following formula (4), (5), (6) or (7). It is at least one group selected from the group. In the following formula (2), X represents SO ₂ , CO, or a direct bond.

  The adhesive layer (b) of the insulating resin layer exhibits a peel strength of 0.7 KN / m or more, and particularly preferably has a softening temperature in the range of 100 to 350 ° C. In the present invention, an adhesive layer having a peel strength of 0.7 KN / m or more is positioned on the outermost layer from the metal layer, so that the adhesiveness with the material in contact with the adhesive layer can be developed later. The adhesive layer (b) preferably has a polyimide structure represented by the above general formula (1), which is a resin material exhibiting good adhesion to metals exemplified in copper foil.

Here, R ₁ in the formula is at least one group selected from the groups represented by the above formulas (2) and (3), and R ₂ is the above formula (5), (7) or (8 And at least one group selected from the groups represented by:

  As the adhesive layer (b) of the insulating resin layer, a siloxane-modified polyimide resin having a silicone unit may be used.

The polyimide resin which has this silicone unit can be illustrated as what has a structural unit of the following general formula (9) and (10).

In the general formula (9), R ₃ represents a tetravalent aromatic group, R ₄ and R ₉ represent a divalent hydrocarbon group, and R _{5 to} R ₈ represent a hydrocarbon group having 1 to 6 carbon atoms. N represents an integer of 1-20.

In the general formula (10), R ₁₀ represents a tetravalent aromatic group, R ₁₁ represents a divalent aromatic group or a trivalent or tetravalent aromatic group represented by the following general formula (11). ing. X represents a hydroxyl group, an amino group, or a carboxyl group, and m is 1 or 2.

  The adhesive layer (b) may be formed of only the siloxane-modified polyimide resin, but is preferably obtained by blending 1 to 40% by weight of an epoxy resin with the siloxane-modified polyimide. In the case where the structural unit of the siloxane-modified polyimide does not have the site of the above formula (11), a preferable embodiment is obtained by adding 1 to 40% by weight of an epoxy resin curing agent.

  In the present invention, the thickness ratio between the low thermal expansion polyimide resin layer (a) and the adhesive layer (b) in the insulating resin layer is such that the dimensional stability and adhesiveness of the base material through which the conductive protrusion penetrates the insulating resin layer Therefore, there is a preferable range for the thickness range of each layer. The thickness ratio of the low thermal expansion polyimide resin layer (a) in the insulating resin layer is preferably 40 to 80%.

If this ratio is less than 40%, the dimensional stability of the substrate is likely to deteriorate. On the other hand, if it exceeds 80%, the thickness of the adhesive layer cannot be ensured, so that the adhesiveness to the member that comes into contact with the adhesive layer later is insufficient. There is a risk that The thickness ratio of the thickness of the adhesive layer and _{(b t)} and the thickness of the low thermal expansion polyimide resin layer _{(a t) (b t /} a t) _{from b t / a t = 0.05 1} . A range of 7 is preferable.

  If the thickness ratio is out of this range, it becomes difficult to achieve both dimensional stability and adhesiveness. In addition to the low thermal expansion polyimide resin layer (a) and the adhesive layer (b), the insulating resin layer may have other insulating resin layers.

However, when the linear expansion coefficient of the entire insulating resin layer exceeds 35 × 10 ⁻⁶ [1 / K], the dimensional stability as a multilayer circuit board is lowered or the difference from the linear expansion coefficient of the metal foil is increased. As a result, the entire substrate is easily warped. Therefore, the linear expansion coefficient of the entire insulating resin layer needs to be 35 × 10 ⁻⁶ [1 / K] or less.

  The conductive protrusion needs to have a height of 10 μm or more. This height means the height from the flat part of the metal foil. If this height is less than 10 μm, after pressure welding, it becomes the same height as the roughened surface of the metal foil and shorts between the circuit layers. On the other hand, if the height exceeds 200 μm, the pitch between the conductive protrusions becomes large and fine wiring becomes impossible.

  The method for forming the conductive protrusions present on the metal foil is not particularly limited, such as printing, plating, etching, etc. For example, a metal mask suitable for the size of the conductive protrusions to be formed on the surface of the metal plate Is prepared, a conductive paste is printed on the metal mask, and dried to form a metal foil having conductive protrusions.

  Examples of the material of the metal foil having conductive protrusions include copper, aluminum, and gold. The material of the flat portion of the metal foil and the conductive protrusion may be the same or different. Preferably both parts are made of copper.

  Further, the thickness of the metal foil, that is, the thickness other than the portion having the conductive protrusion is substantially constant, and is generally in the thickness range of 5 to 75 μm, and in the range of 5 to 35 μm. Is preferred.

  Hereinafter, although an example is described concretely, the present invention is not limited to these examples. In addition, evaluation of the linear expansion coefficient in this invention, adhesive force, and a compression elastic modulus is based on the following evaluation.

[Linear expansion coefficient]
For the linear expansion coefficient, a sample in which the imidization reaction was sufficiently completed was used, and the temperature was raised to 250 ° C. using a thermomechanical analyzer (TMA100) manufactured by Seiko Denshi Kogyo Co., Ltd., and then cooled at a temperature of 10 ° C./min. The average linear expansion coefficient in the range of 240 ° C. to 100 ° C. is obtained.

[Peel strength (adhesive strength)]
A laminate obtained by providing an insulating resin layer on a copper foil having no protrusions was used as a sample, and an electrolytic copper foil having a thickness of 35 μm (3EC-III foil manufactured by Mitsui Mining & Mining, Rz = 6.0 μm) The roughened surfaces were stacked and thermocompression bonded at a glass transition temperature or a softening point temperature at a pressure of 3 MPa for 1 hour. Using a tensile tester (Tensilon tester manufactured by Toyo Seiki Co., Ltd.), the resin side of a 10 mm wide copper foil with resin (no conductive protrusion) is fixed to the aluminum plate with double-sided tape, and copper is 5 mm / min in the 180 ° direction. It peeled and calculated | required.

[Compressive modulus]
The compression modulus was raised to 250 ° C using a Shimadzu Corporation micro hardness tester (DUH-W201) and then loaded to a test force of 196 mN at 13.24 mN / s with a micro indenter having a flat surface with a diameter of 20 µm. And held for 2 seconds, and then calculated based on the stress and strain in the unloading elastic deformation region when unloading at 13.24 mN / s.

(Abbreviations of raw materials used in Examples)
1,3-BAB: 1,3-bis (4-aminophenoxy) benzene BAPP: 2,2′-bis [4- (4-aminophenoxy) phenyl] propane DADMB: 4,4′-diamino-2,2 '-Dimethylbiphenyl PMDA: pyromellitic anhydride BPDA: 3,3', 4,4'-biphenyltetracarboxylic dianhydride PSX-X: diaminosiloxane having an average molecular weight of 740 DMAc: N, N-dimethylacetamide DSDA: 3 , 3 ', 4,4'-Diphenylsulfonetetracarboxylic dianhydride
HAB: 4,4′-Diamino-3,3′-hydroxy-biphenyl Next, Synthesis Examples 1 to 3 of the resin used in the examples of the present invention will be described using the abbreviations of the raw materials described above.

Synthesis of core resin layer (Synthesis Example 1)
In 308 g of DMAc, 20.32 g (0.096 mol) of DADMB and 3.11 g (0.011 mol) of 1,3-BAB were dissolved. Next, 6.20 g (0.021 mol) of BPDA and 18.37 g (0.084 mol) of PMDA were added. Thereafter, stirring was continued at room temperature for about 4 hours to carry out a polymerization reaction, thereby obtaining a polyimide precursor resin liquid a to be a 250 poise (25 ° C.) core resin layer.

  Further, the obtained polyimide precursor solution a was uniformly applied to a copper foil with a thickness of 200 μm using a simple applicator, and subjected to a heat treatment for about 4 hours from room temperature to 330 ° C. to a thickness of 20 μm on the copper foil. A polyimide layer was formed to obtain a copper foil-polyimide layer laminate.

Subsequently, using the ferric chloride aqueous solution, the copper foil of the obtained laminate was removed by etching to obtain a polyimide film. The compression modulus of the obtained polyimide was 20 GPa, and the linear thermal expansion coefficient was 22 × 10 ⁻⁶ [1 / K].

Adhesive layer synthesis (2 examples)
(Synthesis Example 2)
In 294 g of DMAc, 29.13 g (0.071 mol) of BAPP was dissolved. Next, 3.225 g (0.011 mol) of BPDA and 13.55 g (0.062 mol) of PMDA were added. Thereafter, stirring was continued at room temperature for about 3 hours to carry out a polymerization reaction, thereby obtaining a 35 poise (25 ° C.) adhesive polyimide precursor resin liquid b. When the linear expansion coefficient was measured after imidation, it was 60 × 10 ⁻⁶ [1 / K].

(Synthesis Example 3)
To 200 g of N-methyl-2-pyrrolidone, 39.41 g (0.110 mol) of DSDA and 10 g of xylene were added and nitrogen gas was allowed to flow, and the system was thoroughly mixed at room temperature. Next, 10.74 g (0.015 mol) of PSX-X (BY16-853X manufactured by Toray Dow Corning Co., Ltd.) was added dropwise, the reaction solution was ice-cooled with stirring, and 36.95 g (0.090 mol) of BAPP and HAB0.87g (0.004mol) was added, and it stirred at room temperature for 2 hours, and obtained the polyamic acid.

  The polyamic acid was heated to 190 ° C. and stirred while heating for 14 hours to remove water generated during heating out of the system. When heated for 14 hours, the system was cooled to obtain a polyimide solution having a logarithmic viscosity of 0.60 dl / g.

  Next, 25% by weight of novolak type epoxy resin (B-CNB) and 0.5% by weight of 3-mercaptopropyltrimethoxysilane as a silane coupling agent were mixed with 100% by weight of the solid content of the obtained polyimide solution. The polyimide resin solution c for adhesion was prepared by stirring for 3 hours.

When the linear expansion coefficient was measured, it was 60 × 10 ⁻⁶ [1 / K].

Preparation of copper foil A conductive paste made of silver powder having an average particle diameter of 1 μm and a polysulfone resin is printed on a copper foil having a thickness of 12 μm using a 180-mesh stainless screen, and has a conductive protrusion having a height of 80 or 100 μm. Copper foil was prepared. Each protrusion has a mountain shape in cross section, and the portion without the protrusion has a flat shape with a thickness of 12 μm.

Substrate and Substrate Manufacturing Method Next, in a manufacturing process of a multilayer circuit board using the polyimide precursor solution, a manufacturing method of a base material with conductive protrusions penetrating an insulating resin layer, and the substrate as a multilayer core circuit board A method for manufacturing a multilayer circuit board laminated on the substrate will be described.

  FIGS. 1 (1) to (6) and FIGS. 2 (1) to (4) show the manufacture of a multilayer circuit board having a build-up layer as a cable portion by connection using conductive protrusions according to an embodiment of the present invention. It is process drawing which shows a method.

  As shown in FIG. 1 (1), the conductive protrusion 1 is formed on the copper foil 2 by a technique such as printing, etching, or plating when the multilayer circuit board is manufactured. Next, through the formation of the insulating resin layer shown in FIG. 1 (2), the base 6 having a structure in which the conductive protrusions 4 on the copper foil 2 as shown in FIG. 1 (3) penetrate the insulating resin layer 5 is formed. To manufacture.

Formation of Insulating Resin Layer Formation of the insulating resin layer 3 shown in FIG. 1 (2) is as follows. The insulating resin layer 3 includes a core resin layer 3a and an adhesive layer 3b. A polyimide precursor solution 3 is applied onto a copper foil 2 as a metal foil, and then an imidization is performed to form an insulating resin layer 3, and a film-formed polyimide precursor is laminated, and then an imidization is performed to obtain an insulating resin layer. And a laminating method of 3. Here, the thickness of the adhesive layer of the insulating resin layer 3 is preferably 50 to 200% of the circuit thickness of another circuit member with which the conductive protrusions 1 are in contact, or 1 to 5 μm in the case of a solid metal foil.

  First, an example of the casting method will be described.

(Example 1 of casting method)
On the surface of the conductive protrusion 1 (height 100 μm) of the copper foil 2, the polyimide precursor resin liquid a to be the core resin layer 3 a prepared in Synthesis Example 1 is uniformly applied with a thickness of 200 μm and heated at 130 ° C. The solvent is removed by drying to form the core resin layer 3a. Thereafter, the core resin layer 3a is imidized by performing a heat treatment from room temperature to 330 ° C. for about 4 hours, and a laminate in which a polyimide resin layer having a thickness of about 20 μm is formed on the copper foil 2 having the conductive protrusions 1 is obtained. Get.

  Next, the adhesive polyimide resin solution c prepared in Synthesis Example 3 above is uniformly applied to a thickness of 100 μm on the polyimide surface of the core resin layer 3a, and the solvent is removed by heating and drying at 120 ° C. to remove the solvent. Form. Thus, the insulating resin layer 3 having a total thickness of about 50 μm composed of the polyimide resin layer having a two-layer structure constituted by the core resin layer 3 a and the adhesive layer 3 b is formed on the copper foil 2 having the conductive protrusions 1. A circuit substrate was obtained (see FIG. 1 (2)).

  Next, an example of a laminating method is shown.

(Example 1 of laminating method)
Although the base material (support base material) to which the resin solution is applied is not particularly limited, a PET film that has been subjected to a release treatment in order to make the surface easy to peel off is preferable. The thickness of a preferable base material is 100 μm or less.

  First, using a knife coater, the adhesive polyimide precursor resin solution b prepared in Synthesis Example 2 above was uniformly applied to a release PET film (50 μm) with a thickness of 15 μm, and then heated and dried at 130 ° C. The solvent is removed to form the adhesive layer 3b.

  Then, the polyimide precursor resin liquid a to be the core resin layer 3a prepared in Synthesis Example 1 is uniformly applied with a thickness of 180 μm so as to be laminated thereon, and then heated and dried at 130 ° C. to remove the solvent. Then, a two-layer film of a polyimide precursor constituted by the adhesive layer 3b and the core resin layer 3a is formed.

  Thereafter, the two-layer film of the polyimide precursor is peeled off from the base material, and the surface of the copper foil 2 having the conductive protrusion 1 (height 100 μm) is brought into contact with the surface of the polyamic acid resin layer serving as the adhesive layer 3b. After the placement, lamination is performed using a vacuum laminator at a vacuum degree of 4 hPa, a temperature of 150 ° C., and a pressure of 0.9 MPa to obtain a laminate in which the insulating resin layer 3 is formed on the copper foil 2 having the conductive protrusions 1. (See FIG. 1 (2)).

  Next, heat treatment is performed from room temperature to 330 ° C. for about 4 hours to imidize, and an insulating resin layer 3 having a total thickness of about 20 μm composed of two polyimide resin layers is formed on the copper foil 2 having the conductive protrusions 1. A laminated body is obtained (see FIG. 1 (2)).

  Next, using a knife coater, on the release PET film (50 μm), the adhesive polyimide precursor resin solution c prepared in Synthesis Example 3 was uniformly applied with a thickness of 100 μm, and then heated at 120 ° C. The solvent is removed by drying, and a polyimide film for adhesion having a thickness of 30 μm is obtained. This polyimide film forms a third layer for bonding, which is disposed on the opposite side of the core resin layer 3a from the bonding layer 3b.

  Subsequently, the polyimide film for forming the third layer is peeled off from the base material, placed in contact with the polyimide resin surface of the laminate shown in FIG. 1 (2), and the degree of vacuum using a vacuum laminator. Lamination is performed at 4 hPa, a temperature of 150 ° C., and a pressure of 0.9 MPa (lamination time 5 minutes). As a result, a circuit base material is obtained in which the insulating resin layer 3 composed of three polyimide resin layers and having a total thickness of about 50 μm is formed on the copper foil 2 having the conductive protrusions 1.

  As described above, the two-layered insulating resin layer by the casting method or the three-layered insulating resin layer by the laminate method is formed in a state of being bonded onto the copper foil 2.

Polishing Step As shown in FIG. 1 (3), the top of the conductive protrusion 1 is exposed from the insulating resin layer 3 in a step such as polishing. The exposed conductive protrusions 4 are used for connection to other circuit members (not shown) as will be described later.

  Here, as shown in FIG. 1 (2), since the insulating resin layer 3 is formed only on the upper surface of the copper foil 2 and the top of the conductive protrusion 1, the polishing process is compared in both the casting method and the laminating method. Can be done easily.

Manufacturing Process of Multilayer Circuit Board FIGS. 1 (4) to 2 (2) show a manufacturing method of the multilayer core circuit board. First, as shown in FIG. 1 (4), a double-sided copper-clad laminate 7 is prepared. Next, as shown in FIG. 1 (5), a conduction hole 8 is formed by a technique such as an NC drill or a mold. Thereafter, as shown in FIG. 1 (6), after conducting a treatment such as a conductive treatment or electroless plating, both surfaces are electrically connected by the through holes 9 by electrolytic plating.

  Subsequently, as shown in FIG. 2A, a double-sided circuit 11 is formed by a conventional method. Thereafter, as shown in FIG. 2 (2), unnecessary portions of the substrate are punched with a mold or the like. The multilayer core circuit board 13 is manufactured through the steps so far. Even when the number of layers increases, it can be basically manufactured in the same process.

Next, as shown in FIG. 2 (3), the above-described circuit base materials 14 and 15 are laminated on the multilayer core circuit board 13. If necessary, the circuit base materials 14 and 15 are laminated in advance by removing a frame with a mold or the like.
Thereafter, as shown in FIG. 2 (4), a circuit pattern is formed on the copper foils of the base materials 14 and 15 laminated by a conventional method. Further, the multilayer circuit board 16 is obtained by forming a cover film and a solder resist layer, electroless nickel, gold plating and the like by a conventional method.

Moreover, the copper foil of the circuit base materials 14 and 15 of the multilayer circuit board 16 was removed by etching to obtain a polyimide film alone. The linear thermal expansion coefficient of the obtained polyimide was 30 × 10 ⁻⁶ [1 / K].

  Although not shown, the insulating resin layer 3 is formed on the conductive protrusions 1 of the copper foil 2, the tops of the conductive protrusions 1 are exposed to form the conductive protrusions 4, and then laminated and pressed with the copper foil 2. In addition, a flexible double-sided circuit board can be manufactured by forming a circuit pattern by a conventional method.

Other examples of casting method and laminating method (Example 2 of casting method)
On the upper surface of the conductive protrusion 1 (height 100 μm) of the copper foil 2, the polyimide precursor resin liquid a to be the core resin layer prepared in Synthesis Example 1 is uniformly applied with a thickness of 180 μm, and dried by heating at 130 ° C. The solvent was removed. Then, the polyimide precursor resin liquid b for adhesion prepared in Synthesis Example 2 above is uniformly applied to a thickness of 15 μm on the polyimide precursor layer as a core made of the resin liquid a, and is dried by heating at 130 ° C. Was removed.

Then, it is imidized by applying a heat treatment from room temperature to 330 ° C. for about 4 hours, and an insulating resin layer having a total thickness of about 20 μm composed of two polyimide resin layers is formed on the copper foil 2 having the conductive protrusions 1. A formed laminate was obtained. Moreover, the linear thermal expansion coefficient of the polyimide film obtained by etching away copper foil using ferric chloride aqueous solution was 22 * 10 < ^-6 > [1 / K].

(Example 2 of laminating method)
Using a knife coater, the adhesive polyimide precursor resin solution b prepared in Synthesis Example 2 above was uniformly applied to a release PET film (50 μm) with a thickness of 15 μm, and then dried by heating at 130 ° C. Remove. Subsequently, the polyimide precursor resin liquid a to be the core resin layer prepared in Synthesis Example 1 is uniformly applied with a thickness of 170 μm so as to be laminated thereon, and dried by heating at 130 ° C. to remove the solvent. .

  And on the polyimide precursor layer as a core by the polyimide precursor resin liquid a, the polyimide precursor resin liquid b for adhesion prepared in the synthesis example 2 is uniformly applied with a thickness of 15 μm, and is dried by heating at 130 ° C. Then, a three-layer polyimide precursor film was prepared by removing the solvent.

  Thereafter, the three-layer polyimide precursor film is peeled off from the base material and placed in contact with the surface of the copper foil 2 having the conductive protrusions 1 (height 100 μm), and then the degree of vacuum is 4 hPa and the temperature is 150 using a vacuum laminator. Lamination was performed at 0 ° C. and a pressure of 0.9 MPa (lamination time 5 minutes) to obtain a laminate in which the insulating resin layer was formed on the copper foil 2 having the conductive protrusions 1 (see FIG. 1 (2)).

Next, heat treatment is performed from room temperature to 330 ° C. for about 4 hours to imidize, and an insulating resin layer having a total thickness of about 20 μm composed of three polyimide resin layers is formed on the copper foil 2 having the conductive protrusions 1. Thus obtained circuit base material 6 was obtained. Moreover, the copper foil 2 was removed by etching using a ferric chloride aqueous solution to obtain a polyimide film. The compression modulus of the obtained polyimide was 20 GPa, and the linear thermal expansion coefficient was 22 × 10 ⁻⁶ [1 / K].

(Example 3 of casting method)
The polyimide precursor resin liquid b prepared in Synthesis Example 2 was uniformly applied to the top surface of the conductive protrusion 1 (height 80 μm) of the copper foil 2 with a thickness of 15 μm, and then dried by heating at 130 ° C. to remove the solvent. . Next, the polyimide precursor resin liquid a prepared in Synthesis Example 1 was applied uniformly at a thickness of 170 μm so as to be laminated thereon, and dried by heating at 130 ° C. to remove the solvent. Furthermore, the polyimide precursor resin liquid b prepared in Synthesis Example 2 was uniformly applied on the polyimide precursor a layer with a thickness of 15 μm, and dried by heating at 130 ° C. to remove the solvent.

  Thereafter, heat treatment is performed from room temperature to 330 ° C. for about 4 hours to imidize, and an insulating resin layer having a total thickness of about 20 μm composed of three polyimide resin layers is formed on the copper foil having conductive protrusions. A laminated body 1 was obtained.

  Moreover, the insulating resin layer of the same layer structure as the said laminated body 1 was formed on the predetermined electrolytic copper foil which does not have an electroconductive protrusion part for a peel strength measurement. The obtained copper laminate is faced with an electrolytic copper foil (Mitsui Metal Mining 3EC-III foil, Rz = 6.0 μm) roughened surface facing the resin layer, and thermocompression bonded at a temperature of 320 ° C. and a pressure of 3 MPa for 1 hour. did. When this was measured according to the above-described peel strength measurement method, the peel strength was 1.2 kN / m.

(Example 4 of casting method)
After uniformly applying the polyimide precursor resin liquid b prepared in Synthesis Example 2 to a thickness of 15 μm on the upper surface of the conductive protrusion 1 (height 80 μm) of the copper foil 2, the solvent is removed by heating and drying at 130 ° C. did. Next, the polyimide precursor resin liquid a prepared in Synthesis Example 1 was uniformly applied to a thickness of 180 μm so as to be laminated thereon, and dried by heating at 130 ° C. to remove the solvent.

Thereafter, heat treatment is performed from room temperature to 330 ° C. for about 4 hours to imidize, and an insulating resin layer having a total thickness of about 20 μm composed of two polyimide resin layers is formed on the copper foil having conductive protrusions. A laminate was obtained. Moreover, this copper foil was etched away using the ferric chloride aqueous solution, and the polyimide film was obtained. The linear thermal expansion coefficient of the obtained polyimide was 22 × 10 ⁻⁶ [1 / K].

Next, the polyimide resin liquid c prepared in Synthesis Example 3 is uniformly applied to a thickness of 100 μm on the polyimide surface of the laminate, and the solvent is removed by heating and drying at 120 ° C. to form four polyimide resin layers. A laminate 2 was obtained in which an insulating resin layer having a total thickness of about 50 μm was formed on a copper foil having conductive protrusions. Moreover, after heat-processing this laminated body 2 at 180 degreeC for 1 hour, the copper foil was etched away using the ferric chloride aqueous solution, and the polyimide film was obtained. The linear thermal expansion coefficient of the obtained polyimide was 30 × 10 ⁻⁶ [1 / K].

  Moreover, the insulating resin layer of the same layer structure as the laminated body 1 was formed on the predetermined electrolytic copper foil which does not have an electroconductive protrusion part for peel strength measurement. The roughened surface of the electrolytic copper foil (Mitsui Metal Mining 3EC-III foil, Rz = 6.0 μm) is faced to the resin layer side of the obtained laminate, and thermocompression bonding is performed at a temperature of 180 ° C., a pressure of 3 MPa, and an hour. did. When this was measured according to the above-described peel strength measurement method, the peel strength was 1.5 kN / m.

(Example 5 of casting method)
The polyimide precursor resin liquid b prepared in Synthesis Example 2 was uniformly applied to the top surface of the conductive protrusion 1 (height 80 μm) of the copper foil 2 with a thickness of 15 μm, and then dried by heating at 130 ° C. to remove the solvent. . Next, the polyimide precursor resin liquid a prepared in Synthesis Example 1 was applied uniformly at a thickness of 170 μm so as to be laminated thereon, and dried by heating at 130 ° C. to remove the solvent. Furthermore, the polyimide precursor resin liquid b prepared in Synthesis Example 2 was uniformly applied on the polyimide precursor a layer with a thickness of 15 μm, and dried by heating at 130 ° C. to remove the solvent.

Thereafter, heat treatment is performed from room temperature to 330 ° C. for about 4 hours to imidize, and an insulating resin layer having a total thickness of about 20 μm composed of three polyimide resin layers is formed on the copper foil having conductive protrusions. A laminate was obtained. Moreover, this copper foil was etched away using the ferric chloride aqueous solution, and the polyimide film was obtained. The linear thermal expansion coefficient of the obtained polyimide was 22 × 10 ⁻⁶ [1 / K].

Next, the polyimide resin liquid c prepared in Synthesis Example 3 is uniformly applied to a thickness of 100 μm on the polyimide surface of the laminate, and the solvent is removed by heating and drying at 120 ° C. to form four polyimide resin layers. A laminate 3 was obtained in which an insulating resin layer having a total thickness of about 50 μm (thickness accuracy ± 10%, the same as in the following examples) was formed on a copper foil having conductive protrusions. . Moreover, after heat-processing this laminated body 3 at 180 degreeC for 1 hour, the copper foil was etched away using the ferric chloride aqueous solution, and the polyimide film was obtained. The linear thermal expansion coefficient of the obtained polyimide was 33 × 10 ⁻⁶ [1 / K].

  Moreover, the insulating resin layer of the same layer structure as the said laminated body 1 was formed on the predetermined electrolytic copper foil which does not have an electroconductive protrusion part for a peel strength measurement. The roughened surface of the electrolytic copper foil (Mitsui Metal Mining 3EC-III foil, Rz = 6.0 μm) is faced to the resin layer side of the obtained laminate, and thermocompression bonding is performed at a temperature of 180 ° C., a pressure of 3 MPa, and an hour. did. When this was measured according to the above-described peel strength measurement method, the peel strength was 1.5 kN / m.

(Comparative Example 1)
On the upper surface of the conductive protrusion 1 (height 80 μm) of the copper foil 2, the polyimide resin liquid c prepared in Synthesis Example 3 is uniformly applied with a thickness of 200 μm, dried by heating at 120 ° C. to remove the solvent, and the laminate. 4 was obtained. The thickness of the resin applied on the copper foil was about 60 μm.

After heat-treating the above laminate for 1 hour at 180 ° C., the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film. The linear thermal expansion coefficient of the obtained polyimide was 60 × 10 ⁻⁶ [1 / K].

  Moreover, the insulating resin layer of the same layer structure as the laminated body 1 was formed on the predetermined electrolytic copper foil which does not have an electroconductive protrusion part for peel strength measurement. The roughened surface of the electrolytic copper foil (Mitsui Metal Mining 3EC-III foil, Rz = 6.0 μm) is faced to the resin layer side of the obtained laminate, and thermocompression bonding is performed at a temperature of 180 ° C., a pressure of 3 MPa, and an hour. did. When this was measured according to the above-described peel strength measurement method, the peel strength was 1.5 kN / m.

(Comparative Example 2)
The polyimide precursor resin liquid b prepared in Synthesis Example 2 was uniformly applied with a thickness of 200 μm on the upper surface of the conductive protrusion 1 (height 80 μm) of the copper foil 2 and then dried by heating at 130 ° C. to remove the solvent. . Then, it heat-processed over about 4 hours from room temperature to 330 degreeC, and imidized, and obtained the laminated body in which the insulating resin layer about 20 micrometers thick was formed on the copper foil which has an electroconductive protrusion part. Moreover, this copper foil was removed by etching using a ferric chloride aqueous solution to obtain a polyimide film. The linear thermal expansion coefficient of the obtained polyimide was 60 × 10 ⁻⁶ [1 / K].

  On top of that, the polyimide resin liquid c prepared in Synthesis Example 3 was uniformly applied with a thickness of 100 μm, and dried by heating at 120 ° C. to remove the solvent, thereby obtaining a laminate 5. The thickness of the resin applied on the copper foil was about 50 μm from the copper foil side.

The laminate was heat treated at 180 ° C. for 1 hour, and then the copper foil was etched away using a ferric chloride aqueous solution to obtain a polyimide film. The linear thermal expansion coefficient of the obtained polyimide was 60 × 10 ⁻⁶ [1 / K].

  Moreover, the insulating resin layer of the same layer structure as the said laminated body 1 was formed on the predetermined electrolytic copper foil which does not have an electroconductive protrusion part for a peel strength measurement. The roughened surface of the electrolytic copper foil (Mitsui Metal Mining 3EC-III foil, Rz = 6.0 μm) is faced to the resin layer side of the obtained laminate, and thermocompression bonding is performed at a temperature of 180 ° C., a pressure of 3 MPa, and an hour. did. When this was measured according to the above-described peel strength measurement method, the peel strength was 1.5 kN / m.

Table 1 shows the obtained laminate and the evaluation results. It turns out that Examples 3-5 satisfy both the properties of adhesiveness and low linear expansion (dimensional stability).

The process drawing of the manufacturing method of the multilayer circuit board which uses the buildup layer in one Example of this invention as a cable part. The process drawing in the present invention following the process of FIG. Process drawing of the manufacturing method of the multilayer circuit board which uses the buildup layer by a conventional construction method as a cable part. FIG. 4 is a process diagram following the process of FIG. 3. The conceptual cross-sectional block diagram of the circuit base material in one Example of this invention.

DESCRIPTION OF SYMBOLS 1 Conductive protrusion 2 Copper foil 3 Insulating resin layer 3a Core resin layer 3b Adhesion layer 4 Polished conductive protrusion 5 Polished insulating resin layer 6 Base material with conductive protrusion penetrating the insulating resin layer 7 Double-sided copper-clad laminate Plate 8 Conduction hole 9 Through hole 10 Electrolytically plated double-sided copper-clad laminate 11 Double-sided copper-clad laminate 12 formed with a circuit after electrolytic plating Double-sided copper-clad laminate 13 with a frame removed to form a circuit Multilayer core circuit board 14 Substrate 15 with Conductive Protrusion Passing Through Insulating Resin Layer Laminated, and Substrate 16 Layered with Conductive Protrusion Passing Through Insulating Resin Layer After Multi-layer Circuit Board 19 Polyimide Film Having Thermoplastic Polyimide on Both Sides 20 Substrate 21 with conductive protrusion penetrating through polyimide film 21 Substrate 22 with conductive protrusion penetrating through polyimide film After removing the frame, the conductive protrusion is laminated Substrate 23 penetrated through imide film Substrate 24 formed with circuit and conductive protrusion penetrated polyimide film Substrate formed with circuit and conductive protrusion after punching through polyimide film

Claims (4)

A metal foil having a plurality of conductive protrusions having a height of 10 μm or more standing on at least one surface, and an insulating resin having a multilayer structure that is laminated on the one surface of the metal foil and fixed in a state where the conductive protrusions penetrate A circuit substrate comprising a layer,
The insulating resin layer is located on the outermost layer from the low thermal expansion polyimide resin layer (a) having a linear expansion coefficient of 30 × 10 ⁻⁶ [1 / K] or less and the metal foil, and has conductive protrusions. An adhesive layer (b) that gives a peel strength of 0.7 kN / m or more when thermally bonded with a copper foil that does not have a linear expansion coefficient of 35 × 10 ⁻⁶ [1 / K A circuit substrate characterized by the following. The circuit substrate according to claim 1, wherein
The thickness of the low thermal expansion polyimide resin layer (a) is 40 to 80% of the total thickness of the insulating resin layer, and the thickness of the adhesive layer (b) and the thickness of the low thermal expansion polyimide resin layer (a) A circuit base material having a thickness ratio (b / a) in the range of 0.05 to 1.7. The circuit substrate according to claim 1 or 2,
A circuit substrate in which all of the insulating resin layer is a polyimide resin. In the circuit base material in any one of Claims 1 thru | or 3,
A circuit substrate in which the adhesive layer (b) is a polyimide resin layer obtained by blending 1 to 40% by weight of an epoxy resin with a siloxane-modified polyimide having a silicone unit.

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