JP3248786B2 - Circuit board structure and circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board using a polyimide resin as a substrate and a protective film, and more particularly to a circuit board in which an opening for exposing a circuit pattern from one surface is easily formed.

[0002]

2. Description of the Related Art In recent years, the number of electrodes of a semiconductor device has increased with the progress of semiconductor integration technology and high-density packaging technology, and the pitch between the electrodes has been increasing year by year. In addition, the resolution of printers and display devices and the wiring density of printed circuit boards obtained by using this semiconductor device are also shifting to high levels. It is desired that the semiconductor device be formed thinner and lighter, and a film carrier method is adopted as one of the mounting methods of a semiconductor element included in such a semiconductor device. Various methods have been proposed as a method of connecting a semiconductor element and a circuit formed on a carrier in the above film carrier method, but connection is made using a bump-shaped electrode formed on an electrode surface of the semiconductor element or a carrier surface. This method can be mounted in a semiconductor element area, is preferable for high-density mounting, and is partially adopted and executed. Also, when conducting continuity tests of various wiring circuits such as semiconductor elements, the method of inspecting by taking continuity with a printed circuit board via bump-shaped electrodes is compared to a conventional needle-type mechanical probe. It is preferable because it can cope with high-density wiring from the viewpoint of freedom of wiring formation and durability as a probe.

Such a film carrier or printed circuit board generally has a circuit board structure in which a conductive circuit pattern is laminated on a base layer made of a polyimide resin film having excellent heat resistance, mechanical strength, dimensional stability, and the like. It is commonly used. And depending on the application and conduction type,
It is necessary to laminate an insulating resin on the circuit surface for insulation protection, or to locally remove the base layer and the insulation protection layer to expose the circuit terminals for connection. further,
In order to easily perform alignment at the time of connection, processing is often performed into a shape that allows visual confirmation, and guide holes and guide grooves are often provided in the base layer and the insulating protective layer.

[0004]

However, when a polyimide resin film is used as one of the base layers sandwiching the circuit pattern, a resin having lower heat resistance and dimensional stability than the polyimide resin is used as the other base layer. When used as a material layer, there is a problem that the excellent characteristics of the polyimide resin film cannot be sufficiently exhibited. On the contrary,
If a polyimide resin is used for both base layers, the chemical resistance becomes equal, so that a method of selectively removing each layer by chemical etching or the like cannot be used. In addition, the method of etching using a plasma or an ultraviolet laser has a problem that the processing efficiency with respect to the area to be processed is low and the running cost is high. In addition, the method of attaching a thermoplastic polyimide-based resin film processed into a desired shape also has difficulty in positioning accuracy and work efficiency, and has been unacceptable for industrial use.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a circuit pattern sandwiched between polyimide resin layers, thereby achieving excellent heat resistance, mechanical strength, dimensional characteristics, and the like.
An object of the present invention is to provide a circuit board structure capable of locally and efficiently removing only one base material layer.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have obtained a substrate structure in which a circuit pattern is sandwiched between polyimide resins having different dissolution rates in an etching solution. The present inventors have found that a chemical etching method can be easily used for removing a predetermined region of a resin layer, and that highly efficient and highly accurate opening processing can be performed. That is, the circuit board structure of the present invention has a circuit pattern sandwiched by polyimide resin layers having different dissolution rates in an etchant.
And a polymer having a different dissolution rate with respect to the etching solution.
The imide-based resin layer is represented by the following general formulas (I) and (II), respectively.
It is made of a polyimide resin having the structural unit shown . Further, the method for manufacturing a circuit board of the present invention includes the steps of:
For polyimide resin layers with different dissolution rates for
Therefore, a circuit board structure with a circuit pattern interposed
Removal of the surface of the faster polyimide resin layer
Form a resist layer in areas other than the areas to be etched, and perform the same etching
In the liquid, the polyimide resin having the higher dissolution rate is used.
The feature is to selectively remove only the area of the grease layer to be removed.
It is a sign.

[0007]

[Function] Due to the circuit board structure sandwiching a circuit pattern using polyimide resin layers having different dissolution rates in an etchant, only one layer can be selected in the same etchant while both sides are polyimide resin layers. Removed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. It goes without saying that the present invention is not limited to this. FIG. 1 is a partially cutaway perspective view schematically showing one embodiment of the circuit board structure of the present invention. In the figure, A is a circuit board structure of the present invention, in which a circuit pattern 2 is sandwiched between polyimide resin layers 1 and 3 having different dissolution rates in the same etching solution.

The polyimide resin layers 1 and 3 sandwiching the circuit pattern 2 may be similar in shape, mechanical properties, and the like, except that they have different dissolution rates in the same etching solution. In many cases, the lower dissolution rate layer is used as the base layer, and the higher dissolution rate layer is used as the protective layer.
The base layer substantially determines mechanical properties such as strength, elasticity, and flexibility of the circuit board structure A. On the other hand, the protective layer keeps the surface of the circuit pattern 2 protected and insulated. The circuit pattern is exposed accordingly.
The functions and roles of both may be allocated according to the purpose. For example, even a base layer has an opening for exposing a circuit pattern, and a protective layer also plays a role in mechanical strength. In this embodiment, for convenience, the polyimide resin layer having a lower dissolution rate with respect to the same etching solution is referred to as a base layer 1, and the layer having a higher dissolution rate is referred to as a protective layer 3.

The polyimide resin used as the base layer 1 has a structural unit represented by the following general formula (I).

[0011]

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However, in the above general formula (I), Ar
₁ is a divalent aromatic group having 6 or more carbon atoms. The polyimide resin used as the base layer 1 is prepared by applying and drying a polyimide precursor solution obtained by reacting approximately equimolar amounts of a tetracarboxylic acid component and a diamine component in an organic solvent, or further forming a coating film. Can be obtained by dehydration ring closure and curing by heating. As the tetracarboxylic acid component, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is used. In addition, the above Ar
Examples of the diamine component containing ₁ include, for example, p-phenylenediamine, 4,4′-diaminodiphenyl ether,
m-phenylenediamine, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether,
At least one of 4,4'-diaminobiphenyl and the like is used. As the organic solvent, N-methyl-
N, N'-dimethylacetamide in 2-pyrrolidone,
N, N'-dimethylformamide, 1,3-dimethyl-
Imidazolidinone, dimethyl sulfoxide, dimethyl sulfide, dimethyl sulfone, pyridine, tetramethyl urea, diglyme, triglyme and the like are used.

The polyimide resin used as the protective layer 3 has a structural unit represented by the following general formula (II).

[0014]

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However, in the above general formula (II), Ar
₂ is a divalent aromatic group having 12 or more carbon atoms, and examples thereof include those represented by the following formula.

[0016]

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[0017]

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[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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In the above formula, R ^{3 to} R ³¹ independently represent a lower alkyl group, a lower alkoxy group or a halogen group, and n ^{3 to} n ³¹ independently represent 0 or 1-4. And X represents hydrogen or a halogen group. In the above, the lower alkyl group is methyl,
Linear or branched alkyl having 1 to 8 carbon atoms such as ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, heptyl, octyl, etc. A lower alkoxy group means 1 to 8 carbon atoms such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, etc. Refers to a linear or branched alkoxy group, and the halogen group is fluorine, chlorine,
Refers to bromine or iodine.

The polyimide resin used for the protective layer 3 is prepared by applying a polyimide precursor solution obtained by reacting a tetracarboxylic acid component with the diamine component containing Ar ₂ in an approximately equimolar amount in an organic solvent, followed by drying. It can be obtained by heating and then dehydrating and ring-closing and curing it by heating, and before or after curing, it dissolves more easily in an alkali solution than the polyimide resin used for the base layer 1. Things.

Pyromellitic dianhydride is used as the tetracarboxylic acid component. Specific examples of the diamine component containing Ar ₂ include, for example, 4,4′-
Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminobiphenyl, bis [4- (3-
Aminophenoxy) phenyl] sulfone, bis [4-
(4-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 4,4 ′
-Diaminodiphenyl sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-
Aminophenoxy) phenyl] ether, bis [4-
(3-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] propane,
Examples include 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenylbenzophenone, and at least one of these is used. Further, p-phenylenediamine having an aromatic group of 6 carbon atoms and m-phenylenediamine may also be used as long as the aromatic group is 配合 or less in molar ratio to a diamine having 12 or more carbon atoms. .

As the organic solvent, the same organic solvent as that used for obtaining the polyimide precursor in the base layer 1 is used.

The circuit pattern 2 is a wiring circuit made of a good conductor metal, and may be made of a material such as gold, silver, copper, platinum, nickel, aluminum, iron, chromium, molybdenum, tungsten, zinc, tin, or an alloy thereof. And the like. Further, for example, a multilayer structure made of the above-mentioned good conductor metal may be used, for example, by applying gold plating or solder plating to a circuit pattern made of copper foil. Examples of a method of forming the circuit pattern 2 include a subtractive method in which one to several conductive layers are stacked on the entire surface of a predetermined region on the base layer by vapor deposition, pressure bonding, and the like, and then etched to form a conductive circuit, thereby forming a conductive circuit. In addition to a known pattern forming method such as an additive method of forming only a circuit pattern on a base substrate by plating, vapor deposition, or the like, a method of applying the polyimide precursor solution used for forming the base layer 1 to a good conductor layer and curing the solution. Etc. are exemplified.

As a method for laminating and covering the protective layer 3 on the circuit pattern 2, the polyimide precursor solution used for forming the protective layer 3 is coated on the base layer in the same manner as the method for laminating the base layer 1 and the circuit pattern 2. Examples include a method of applying and curing the circuit pattern formed thereon, and a method of separately forming the protective layer 3 in a film shape and compressing the film by heat or the like. In order to enhance the adhesion between the protective layer and the base layer and the metal layer of the circuit pattern, with respect to the metal surface serving as an interface,
Siding, nickel plating, copper-zinc alloy plating,
Alternatively, a chemical or mechanical surface treatment may be performed using an aluminum alcoholate, an aluminum chelate, a silane coupling agent, or the like.

In the circuit board structure of the present invention, the layer using the polyimide resin having a higher dissolution rate in the same etching liquid is the target layer to be subjected to the opening processing. Is assumed to be the protective layer 3, and the opening processing method will be described below. As a method of locally removing the protective layer 3, a resist layer is formed on a region other than a region to be removed on the surface of the protective layer, and the resist layer is etched by an immersion method, a spray method, or the like using an etchant. Only the area can be easily removed.

The resist layer is not particularly limited as long as it has alkali resistance, and a commercially available solvent-type photoresist or peel-development-type photoresist may be used, or polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylic resin,
Coating a graft polymer such as a copolymer such as cellulose resin, chlorinated polyether, EVA, or ABS resin on the polyimide resin layer, and patterning by photolithography or the like so that only the target area of the protective layer is exposed. do it.

As the etchant, a mixed solution of an aqueous solution of an inorganic alkali such as sodium hydroxide or potassium hydroxide or an aqueous solution of an organic alkali such as hydrazine and an alcohol, glycol or amide solvent is used. If necessary, two or more kinds of alkaline aqueous solutions or solvents may be used in combination.

The thickness of each layer of the base layer 1 and the protective layer 3 is not particularly limited as long as the mechanical strength is sufficient. If the substrate needs to be flexible, 5-200
It is preferably about μm, particularly preferably about 10 to 100 μm. In addition, since the dissolution rate of the protective layer is 10 times or more that of the base layer in the same etching solution,
In order to suppress damage to the base layer due to the etching step, the thickness of the protective layer is preferably 10 times or less the thickness of the base layer, and more preferably the thickness of the protective layer and the base layer is the same or less. It is preferable, particularly preferably, that the thickness of the protective layer be 1/10 or less of the thickness of the base layer, thereby substantially eliminating damage to the base layer due to the etching step.

[Experimental Example 1] In this experimental example, as shown in FIG. 2, a circuit board structure of the present invention was specifically manufactured, and the protective layer 3 was etched to expose the circuit pattern 2. An application example using the circuit board structure of the present invention in which the device hole 4 was formed was shown, and it was confirmed that the circuit board structure of the present invention had excellent workability. (1) Formation of Precursor Solution Approximately equimolar amounts of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine are polymerized in N-methyl-2-pyrrolidone to prepare a polyimide precursor. A body solution (I) was obtained. Also, pyromellitic dianhydride and 4,
Approximately equimolar amounts of 4'-diaminodiphenyl ether are converted to N,
Polymerization was performed with N′-dimethylacetamide to obtain a polyimide precursor solution (II). (2) Lamination of Base Layer and Conductive Layer The polyimide precursor solution (I) obtained above was applied to a layer having a thickness of 35 μm.
m, and then uniformly cast on a rolled copper foil using a comma coater, dried at 100 ° C., and further heated to 450 ° C. in an atmosphere in which the oxygen concentration was reduced to 1.5% or less by nitrogen gas replacement.
To give a dehydrated ring-closed imide conversion, and a thickness of 25 μm
Was laminated with a copper foil layer. (3) Formation of Circuit Pattern The copper foil was etched by a known subtractive method to form a circuit pattern 2. (4) Formation of Protective Layer After nickel plating is applied to the surface of the circuit pattern 2, the polyimide precursor solution (II) is applied to the circuit pattern 2 and the entire surface of the base layer in the same manner as in the case of the base layer. Is applied, dried and heated to form a protective layer having a thickness of 10 μm. The protective layer is made of a polyimide resin having a higher dissolution rate with respect to an alkali etching solution, and the base layer of the polyimide resin having a lower dissolution rate. Thus, a circuit board structure of the present invention having a circuit pattern interposed was obtained. (5) Forming Device Holes in Protective Layer (Etching Process) A mask is applied to a region other than the processed region on the surface of the protective layer using a photosensitive rubber-based resist. The substrate was immersed in an alkaline etching solution composed of 5 parts of water hydrazine and subjected to etching at 50 ° C. for 10 minutes to obtain a circuit board structure having device holes 4.

When the quality of the circuit board structure obtained above was inspected, no significant erosion was observed in the base layer even though both sides were made of a polyimide resin layer, and only the target portion of the protective layer was selectively formed. , And was confirmed to have favorable processability.

[Experimental Example 2] In this experimental example, as shown in FIG. 2, the edge of the protective layer 3 of the circuit board structure A according to the present invention is etched to expose the circuit pattern 2 and connect terminals. In addition, bumps 5 that are electrically connected to the circuit pattern 2 are formed on the surface of the protective layer to show another application example of the circuit board structure of the present invention, and that the circuit board structure of the present invention has excellent workability. Was confirmed. (1) Formation of Precursor Solution 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride of p-phenylenediamine, and 4,4′-diaminodiphenyl ether,
Polymerization was performed in N-methyl-2-pyrrolidone at a molar ratio of 10: 5: 5 to obtain a polyimide precursor solution (I). Also,
Approximately equimolar amounts of pyromellitic dianhydride and bis [4- (4-aminophenoxy) phenyl] hexafluoropropane were polymerized with N, N'-dimethylacetamide to obtain a polyimide precursor solution (II). (2) Lamination of Base Layer and Conductive Layer Using the above polyimide precursor solution (I), a rolled copper foil having a thickness of 35 μm and a thickness of 25
A laminate with a μm base layer was obtained. (3) Formation of Circuit Pattern The copper foil was etched by a known subtractive method to form a circuit pattern 2. (4) Formation of Protective Layer After nickel plating was applied to the surface of the circuit pattern 2, the polyimide precursor solution (II) was uniformly cast over the entire surface of the circuit pattern 2 and its base layer using a comma coater. Thereafter, the substrate was dried at 150 ° C., and further dried under an atmosphere in which the oxygen concentration was reduced to 1.5% or less by nitrogen gas replacement.
℃, dehydrated ring-closing imide conversion to a thickness of 10 μm
Was formed, and a circuit board structure similar to that of Experimental Example 1 was obtained. (5) Forming connection terminals. A mask is applied to the area other than the processing area at the end of the protective layer using a photosensitive rubber-based resist. An etching process was performed at 60 ° C. for 5 minutes to obtain a circuit board structure in which the circuit pattern 2 was exposed at the ends and used as connection terminals. (6) Formation of bumps on the surface of the protective layer Excimer laser processing is performed at positions corresponding to the circuit patterns 2 on the surface of the protective layer to form fine openings 6, exposing the circuit patterns 2, and using the circuit patterns 2 as cathodes. Au plating was performed in the electrolytic solution tank, and after filling the fine openings 6 with Au, further Au plating was continued to obtain a flexible circuit board having a bump projecting 10 μm from the surface of the protective layer.

When the quality of the flexible circuit board obtained as described above was inspected, it was confirmed that the quality was favorable as in Experimental Example 1.

The circuit board structure of the present invention is suitably used as the outermost layer structure of a multilayer circuit board in addition to the above-mentioned flexible circuit board.

[0042]

As described in detail above, the circuit board structure of the present invention has excellent heat resistance, mechanical strength,
A circuit board that has dimensional characteristics and the like on both sides, and it is possible to selectively and efficiently remove only one side of the polyimide resin layer by one etching step, and it is excellent in opening processability. As a structure, it can be applied to various uses such as a TAB film and a flexible printed board.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing one embodiment of a circuit board structure of the present invention.

FIG. 2 is a perspective view schematically showing one application example using the circuit board structure of the present invention.

FIG. 3 is a perspective view schematically showing another application example using the circuit board structure of the present invention.

[Explanation of symbols]

 A Circuit board structure 1 Base layer 2 Circuit pattern 3 Protective layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-48493 (JP, A) JP-A-62-113494 (JP, A) JP-A-2-18986 (JP, A) JP-A-4- 3492 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 1/03 H05K 3/28

Claims (5)

(57) [Claims] A circuit pattern is sandwiched between polyimide resin layers having different dissolution rates in an etching solution.
And a polymer having a different dissolution rate with respect to the etching solution.
The imide resin layers are represented by the following general formulas (I) and (II), respectively.
Consisting of polyimide resin having structural unit
Is a circuit board structure. Embedded image Embedded image (In the above formula, Ar ₁ is a divalent aromatic group having 6 or more carbon atoms, A
r ₂ represents a divalent aromatic group having 12 or more carbon atoms. ) 2. In the structural unit represented by the general formula (II), Ar ₂ is Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image Or (Wherein, R ^{3 to} R ³¹ independently represent a lower alkyl group, a lower alkoxy group or a halogen group;
n ^{3 to} n ³¹ each independently represent 0 or an integer of 1 to 4, and X represents hydrogen or a halogen group. ) Is a group represented by the circuit board structure of claim 1, wherein. 3. The circuit according to claim 1, wherein, of the polyimide resin layers having different dissolution rates with respect to the etching solution, the layer having the higher dissolution rate has a thickness of 10 times or less the thickness of the layer having the lower dissolution rate. Substrate structure. 4. A polyimide resin layer having a different dissolution rate with respect to an etching solution, wherein the higher dissolution rate of the polyimide resin layer has a dissolution rate which is 10 times or more the dissolution rate of the slower dissolution rate layer. 3. The circuit board structure according to any one of 3 . 5. A method in which the dissolution rate of an etching solution is different.
The circuit is sandwiched between the circuit patterns by the polyimide resin layer.
Polyimide resin layer with faster dissolution rate with substrate structure
A resist layer on the surface of the surface other than the area to be removed
In the same etching solution, the dissolution rate is high.
Select only the area of the polyimide resin layer to be removed
And a method of manufacturing a circuit board.