JPH0745919A - Circuit board structure - Google Patents

Abstract

PURPOSE:To provide a circuit board structure, wherein heat resistance, mechanical strength, size characteristics and the like are made excellent by holding a circuit pattern with polyimide-based resin layers, and only one base-material layer can be removed locally and efficiently. CONSTITUTION:A circuit board structure A, wherein a circuit pattern 2 is held with polyimide-based resin layers 1 and 3 having the different dissolution speeds for etchant, is obtained. Thus, the excellent heat resistance, mechanical strength, size characteristics and the like of the polyimide-based resins are provided on both surfaces. Furthermore, only the polyimide-based resin layer on one side can be removed selectively and efficiently. The circuit board structure having the excellent opening machining property can be applied into the various kinds of applications such as TAB films and flexible printed boards.

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 board and a protective film, and more particularly to a circuit board in which an opening for exposing a circuit pattern from one surface can be 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 highly integrated technology and high-density packaging technology, and the pitch between the electrodes has also been increased year by year. In addition, the resolution of printers and display devices obtained using this semiconductor device and the wiring density of printed circuit boards have also moved to high levels. The semiconductor device is desired to be thinner and lighter in weight, and the film carrier method is adopted as one of the mounting methods of the semiconductor elements constituting such a semiconductor device. Various methods have been proposed as a method of connecting the semiconductor element and the circuit formed on the carrier in the film carrier method, but connection is performed by using bump-like electrodes formed on the electrode surface of the semiconductor element or the carrier surface. This method can be mounted in a semiconductor element area, is preferable for high-density mounting, and is partially adopted and implemented. Further, even when conducting a continuity test of various wiring circuits such as semiconductor elements, the method of inspecting by conducting with the printed circuit board via the bump-shaped electrodes is compared with the conventional needle-type mechanical probe, This is preferable because it can accommodate high-density wiring in terms of the degree of freedom in wiring formation and the durability as a probe.

In such a film carrier or a printed circuit board, a circuit board structure in which a conductor circuit pattern is laminated on a base layer made of a polyimide resin film having excellent heat resistance, mechanical strength and dimensional stability is generally used. Used for. And, depending on its 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 the alignment at the time of connection, it is often processed 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 material layers sandwiching the circuit pattern, a resin having lower heat resistance and dimensional stability than the polyimide resin is used as the other base material layer. If it is 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 polyimide resins are used for both base material layers, the chemical resistance becomes equal, so that a method of selectively removing each layer by chemical etching or the like cannot be used. Further, the method of etching using plasma or ultraviolet laser has a problem that the processing efficiency with respect to the processed area is low and the running cost is high. In addition, the method of sticking a thermoplastic polyimide resin film processed into a desired shape also has difficulty in alignment accuracy and work efficiency, and is difficult to accept for industrial use.

An object of the present invention is to solve the above-mentioned problems and to sandwich a circuit pattern between polyimide resin layers, thereby providing excellent heat resistance, mechanical strength, dimensional characteristics, etc.
It is to provide a circuit board structure capable of locally and efficiently removing only one base material layer.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a substrate structure in which a circuit pattern is sandwiched by polyimide resins having different dissolution rates in an etching solution is used. The present invention has been completed based on the finding that a chemical etching method can be easily used to remove a predetermined region of a resin layer, and highly efficient and highly accurate opening processing can be performed. That is, in the circuit board structure of the present invention, the circuit pattern is sandwiched by the polyimide resin layers having different dissolution rates in the etching liquid.

[0007]

[Function] Due to the circuit board structure in which the circuit pattern is sandwiched by the polyimide resin layers having different dissolution rates with respect to the etching solution, only one layer is selected in the same etching solution even though both sides are polyimide resin layers. Will be removed.

[0008]

EXAMPLES The present invention will be specifically described below based on examples. Needless to say, the present invention is not limited to this. FIG. 1 is a partially cutaway perspective view schematically showing an 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, etc., except that they have different dissolution rates in the same etching solution, but usually they are the same. In many cases, the layer having the slower dissolution rate is the base layer and the layer having the faster dissolution rate is the protective layer.
The base layer substantially determines various mechanical properties such as strength, elasticity, and flexibility of the circuit board structure A, while the protective layer keeps the surface of the circuit pattern 2 protected and insulative. According to this, the circuit pattern is exposed.
The functions and roles of both may be distributed according to the purpose. For example, even the base layer has an opening for exposing the circuit pattern, and the protective layer also contributes to the mechanical strength. In this embodiment, for convenience, the polyimide resin layer having the slower dissolution rate in the same etching solution is used as the base layer 1, and the layer having the faster dissolution rate is used as the protective layer 3.

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

[0011]

[Chemical 3]

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 a polyimide precursor solution obtained by reacting approximately equimolar amounts of a tetracarboxylic acid component and a diamine component in an organic solvent and then dried to form a coating film. Can be obtained by dehydration ring closure by heating and curing. 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 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, tetramethylurea, 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]

[Chemical 4]

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]

[Chemical 5]

[0017]

[Chemical 6]

[0018]

[Chemical 7]

[0019]

[Chemical 8]

[0020]

[Chemical 9]

[0021]

[Chemical 10]

[0022]

[Chemical 11]

[0023]

[Chemical 12]

[0024]

[Chemical 13]

[0025]

[Chemical 14]

[0026]

[Chemical 15]

However, in the above formula, R ^{3 to} R ³¹ each independently represent a lower alkyl group, a lower alkoxy group or a halogen group, and n ^{3 to} n ³¹ each independently represent 0 or 1 to 4. And an X represents hydrogen or a halogen group. In the above, the lower alkyl group is methyl,
C1-C8 straight or branched alkyl such as ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, heptyl and octyl. A lower alkoxy group is a lower alkoxy group having 1 to 8 carbon atoms such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy and the like. Is 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 obtained by reacting a tetracarboxylic acid component and a diamine component containing Ar ₂ in an equimolar amount in an organic solvent, and applying and drying a polyimide precursor solution. It can be formed into a coating film or can be obtained by further dehydration ring closure by heating and curing, and it is more easily dissolved in an alkaline solution than the polyimide resin used for the base layer 1 before or after curing. It is a thing.

Pyromellitic dianhydride is used as the tetracarboxylic acid component. Further, as a specific diamine component containing Ar ₂ , 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 of 3,3′-diaminodiphenylpropane, 3,3′-diaminodiphenylbenzophenone, and the like, at least one of which is used. Also, p-phenylenediamine and m-phenylenediamine having an aromatic group of 6 carbon atoms may be used as long as the aromatic group has a compounding molar ratio of 1/2 or less with respect to the diamine having 12 or more carbon atoms. .

As the organic solvent, the same one as in the case of 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 is made of gold, silver, copper, etc., as well as platinum, nickel, aluminum, iron, chromium, molybdenum, tungsten, zinc, tin, or alloys thereof. Are exemplified. Further, for example, a multilayer structure made of the above-mentioned good conductor metal may be used, such as gold plating or solder plating on a circuit pattern made of copper foil. As the method of forming the circuit pattern 2, a subtractive method in which one to several conductor layers are laminated on the entire surface of a predetermined region on the base layer by vapor deposition, pressure bonding, etc., and then etching is performed to form a conductor 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 same. Etc. are illustrated.

As a method for laminating and covering the protective layer 3 on the circuit pattern 2, as in the laminating method for the base layer 1 and the circuit pattern 2, the polyimide precursor solution used for forming the protective layer 3 is used as the base layer. Examples thereof include a method of applying the composition on the circuit pattern formed above and curing it, a method of separately forming the protective layer 3 in the form of a film and press-bonding it with 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,
Siding, nickel plating, copper-zinc alloy plating,
Alternatively, the surface may be chemically or mechanically treated with 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, which has a higher dissolution rate in the same etching solution, is the target layer to be subjected to the opening processing. Assuming that is the protective layer 3, the opening processing method will be described below. As a method for locally removing the protective layer 3, if a resist layer is formed on the surface of the protective layer other than the area to be removed and etching is performed by an immersion liquid or a spray method using an etching solution, a desired protective layer can be obtained. 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 peeling development type photoresist is used, or polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylic resin,
Graft polymer such as cellulose resin, chlorinated polyether, copolymer such as EVA, ABS resin, etc. is coated on the polyimide resin layer and patterned by photolithography to expose only the target region of the protective layer. do it.

As the etching solution, a mixed solution of an inorganic alkaline aqueous solution such as sodium hydroxide and potassium hydroxide or an organic alkaline aqueous solution such as hydrazine and an alcohol-based, glycol-based or amide-based solvent is used. Moreover, you may use together 2 or more types of alkaline aqueous solutions or a solvent as needed.

The thickness of each of the base layer 1 and the protective layer 3 is not particularly limited as long as the mechanical strength is sufficient, but through-holes or recesses may be formed with a fine pitch or shape, 5 to 200 if the substrate needs flexibility
The thickness 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 the dissolution rate 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 protective layer and the base layer have the same thickness or less. Well, particularly preferably, by setting the thickness of the protective layer to be 1/10 or less of the thickness of the base layer, damage to the base layer due to the etching step can be substantially eliminated.

[Experimental Example 1] In this experimental example, as shown in FIG. 2, the circuit board structure of the present invention was specifically manufactured, and the protective layer 3 was further etched to expose the circuit pattern 2. While forming the device hole 4 and showing one application example using the circuit board structure of the present invention, it was confirmed that the circuit board structure of the present invention has excellent workability. (1) Preparation of precursor solution 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine are used in N-methyl-2-pyrrolidone to polymerize approximately equimolar amounts of polyimide precursor. A body solution (I) was obtained. In addition, pyromellitic dianhydride and 4,
Approximately equimolar amount of 4'-diaminodiphenyl ether is converted into N,
Polymerization with N′-dimethylacetamide gave a polyimide precursor solution (II). (2) Lamination of Base Layer and Conductor Layer The polyimide precursor solution (I) obtained above was formed to a thickness of 35 μm.
After uniformly casting and coating on a rolled copper foil of m using a comma coater, it is dried at 100 ° C., and further 450 ° C. in an atmosphere in which the oxygen concentration is 1.5% or less by nitrogen gas replacement.
By heating, the dehydration ring-closing imide conversion is performed and the thickness is 25 μm
The base layer and the copper foil layer were laminated. (3) Formation of Circuit Pattern The copper foil was subjected to etching processing by a known subtractive method to form a circuit pattern 2. (4) Protective Layer Formation After the surface of the circuit pattern 2 is nickel-plated, the polyimide precursor solution (II) is applied to the entire surface of the circuit pattern 2 and its base layer in the same manner as in the case of the base layer. Is applied, dried, heated, etc. to form a protective layer having a thickness of 10 μm. The protective layer is composed of a polyimide resin having a faster dissolution rate in an alkali etching solution, and the base layer is made of a polyimide resin having a slower dissolution rate. A circuit board structure of the present invention in which a circuit pattern is sandwiched is obtained. (5) Device hole formation for the protective layer (etching process) A mask was applied to the surface of the protective layer other than the processed region using a photosensitive rubber-based resist, and 50% potassium hydroxide aqueous solution 50 parts, ethanol 50 parts The circuit board structure having the device holes 4 was obtained by immersing in an alkaline etching solution containing 5 parts of water hydrazine and performing an etching treatment at 50 ° C. for 10 minutes.

When the quality of the circuit board structure obtained above was inspected, no noticeable erosion was observed in the base layer even though both sides were layers of polyimide resin, and only the target portion of the protective layer was selectively exposed. It was confirmed that it had a favorable processability.

[Experimental Example 2] In this experimental example, as shown in FIG. 2, an end portion 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 the circuit board structure of the present invention has excellent workability. Was confirmed. (1) Generation 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,
The polyimide precursor solution (II) was obtained by polymerizing approximately equimolar amounts of pyromellitic dianhydride and bis [4- (4-aminophenoxy) phenyl] hexafluoropropane with N, N′-dimethylacetamide. (2) Lamination of Base Layer and Conductor Layer Using the above polyimide precursor solution (I), the rolled copper foil having a thickness of 35 μm and the thickness of 25 were prepared by the same steps as in Experimental Example 1.
A laminate with a μm base layer was obtained. (3) Formation of Circuit Pattern The copper foil was subjected to etching processing by a known subtractive method to form a circuit pattern 2. (4) Protective Layer Formation After nickel plating was applied to the surface of the circuit pattern 2, the polyimide precursor solution (II) was uniformly cast and coated on the entire surface of the circuit pattern 2 and its base layer using a comma coater. After that, it was dried at 150 ° C., and further 450 ° C. in an atmosphere in which the oxygen concentration was reduced to 1.5% or less by nitrogen gas replacement.
Heating to ℃, dehydration ring-closing imide conversion, thickness 10μm
The protective layer was formed to obtain a circuit board structure similar to that of Experimental Example 1. (5) Formation of connection terminals. A mask is applied using a photosensitive rubber-based resist except the processed region at the end of the protective layer, and the mask is dipped in an alkaline etching solution consisting of 80 parts of 50% potassium hydroxide aqueous solution, 20 parts of ethanol, and 10 parts of hydrazine hydrate. Then, etching treatment was performed at 60 ° C. for 5 minutes to obtain a circuit board structure in which the circuit pattern 2 was exposed at the end and served as a connection terminal. (6) Formation of bumps on the surface of the protective layer Excimer laser processing is performed at positions corresponding to the circuit pattern 2 on the surface of the protective layer to form fine openings 6 to expose the circuit pattern 2, and the circuit pattern 2 is used as a cathode. After performing Au plating in the electrolytic solution tank to fill the fine openings 6 with Au, Au plating was further continued to obtain a flexible circuit board having bumps protruding by 10 μm from the surface of the protective layer.

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

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

[0042]

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

[Brief description of drawings]

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

FIG. 2 is a perspective view schematically showing an 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

Claims (3)

[Claims] 1. A circuit board structure in which a circuit pattern is sandwiched by polyimide resin layers having different dissolution rates with respect to an etching solution. 2. A polyimide resin layer having a different dissolution rate with respect to an etching solution is represented by the following general formulas (I) and (II), respectively.
The circuit board structure according to claim 1, which has a structural unit represented by: [Chemical 1] [Chemical 2] (In the above formula, Ar ₁ is a divalent aromatic group having 6 or more carbon atoms, A 1
r ₂ represents a divalent aromatic group having 12 or more carbon atoms. ) 3. The circuit according to claim 1, wherein among polyimide-based resin layers having different dissolution rates with respect to an etching solution, the layer having a higher dissolution rate has a thickness of 10 times or less than the thickness of a layer having a slower dissolution rate. Substrate structure.