JP3376930B2 - Wiring board and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board suitable for mounting an IC chip and a method for manufacturing the wiring board.

[0002]

2. Description of the Related Art A wiring board having a structure shown in FIG. 5 has been proposed as a wiring board intended for chip size packaging of IC chips (see Japanese Patent Publication No. 07-60840, Example 1). This wiring board is provided with a polyimide base material 51 which is an insulating layer, a copper pattern 52 which is a conductive layer formed on the back surface thereof, and a through hole A which is provided in the polyimide base material 51 and reaches the copper pattern 52. Polyimide base material 51
And copper bumps 53 protruding from the surface of the.

Further, this wiring board is manufactured as shown in FIG.

First, a copper foil laminated on the back surface of a polyimide base material 51 is patterned by a conventional method to form a copper pattern 52 (FIG. 6 (a)).

Next, a through hole A reaching the copper pattern 52 is formed by laser processing from the surface side of the polyimide base material 51 (FIG. 6B).

Next, the copper pattern 52 is masked with a masking tape, electrolytic copper plating is performed using the copper pattern 52 as a cathode, and a through hole A formed in the polyimide base material 51.
Is filled with copper to form copper bumps 53 by protruding from the surface of the polyimide base material 51, and then the masking tape is removed to obtain a wiring board (FIG. 6C).

According to this wiring board, it is said that the copper bumps can be introduced at a low cost without the need to excessively increase the alignment accuracy when forming the through holes A.

[0008]

However, when the through hole A is provided in the polyimide base material by laser processing,
The use of the excimer laser has a problem that the processing cost becomes too high. Further, when a normal laser such as a YAG laser whose processing cost is relatively lower than that of the excimer laser is used, the copper pattern 52 at the bottom of the through hole A is
Since the polyimide powder adheres to the exposed surface of, the connection reliability is reduced. Here, there is a problem that in order to remove the polyimide powder, a complicated desmear treatment with an aqueous solution of permanganate is necessary.

When mounting an IC chip on the wiring board of FIG. 5, an anisotropic conductive adhesive film, an anisotropic conductive paste or the like is sandwiched between them for thermocompression bonding. In order to achieve further simplification and cost reduction, it has been required to directly bond the wiring board and the IC chip.

The present invention solves the problems of the prior art, is a wiring board suitable for mounting an IC chip, has a low processing cost, does not require complicated desmear processing, and has connection reliability. It is intended to provide a high-quality wiring board. Another object is to provide a wiring board with a structure capable of directly bonding electronic components such as an IC chip and a wiring board with high connection reliability without using an anisotropic conductive adhesive film or an anisotropic conductive paste. .

[0011]

Means for Solving the Problems When the through holes are provided in the insulating layer, the present inventors form the holes by chemical etching using a photolithographic method instead of laser processing,
Then, by filling the holes with a metal plug by electrolytic plating, bumps can be formed on the surface of the wiring board at a low cost. It was found that an electronic component such as an IC chip and a wiring board can be bonded with high connection reliability via an anisotropic conductive adhesive film or the like due to the anchor effect of the surface and the unevenness of the surface. It came to completion.

Further, the present inventor provides an adhesive layer on the surface of the wiring board on the side of the metal bump formed as described above, and chemically etches back the adhesive layer to accurately form a hole in the insulating layer. It is not necessary to form a hole aligned with the adhesive layer on the adhesive layer, and by providing the adhesive layer on the surface of the wiring board on the metal bump side, high reliability of connection between the electronic component such as an IC chip and the wiring board can be obtained. The inventors have found that they can be directly joined by, and completed the second aspect of the present invention.

That is, according to the first aspect of the present invention, an insulating layer is formed on a conductive layer, and a hole reaching the conductive layer is provided in the insulating layer, and a metal plug is formed in the hole by electrolytic plating. Is formed, the tip of the metal plug constitutes a metal bump protruding from the insulating layer, and the surface of the metal bump is processed to be uneven; and a manufacturing method thereof. Then, the following steps (a), (b) and (m): (a) A step of forming a hole reaching the conductive layer by chemical etching using a photolithography method in the insulating layer on the conductive layer; ) While forming a metal plug in the hole of the insulating layer by the electrolytic plating method using the conductive layer as a cathode, the metal plug is further continuously grown by the electrolytic plating method, and the tip thereof is projected from the surface of the insulating layer. Metal bump process; and (M) to provide a manufacturing method which comprises a step of uneven processing of the surface of the metal bumps that protrude from the surface of the insulating layer.

According to a second aspect of the present invention, an insulating layer and an adhesive layer are formed on the conductive layer, and the adhesive layer and the insulating layer are provided with holes reaching the conductive layer. A metal plug is formed in the hole by electrolytic plating,
A wiring board characterized in that the tip of the metal plug constitutes a metal bump protruding from the adhesive layer, and the surface of the metal bump is processed to be uneven; and a method for manufacturing the wiring board, comprising the steps of: ) To (d) and (m): (a) a step of forming a hole reaching the conductive layer by chemical etching using a photolithography method in the insulating layer on the conductive layer; (b) using the conductive layer as a cathode A step of forming a metal plug in the hole of the insulating layer by electrolytic plating, and further continuously growing the metal plug by electrolytic plating to form a metal bump whose tip projects from the surface of the insulating layer; c) a step of forming an adhesive layer on the surface of the insulating layer on which the metal bump is formed so that the metal bump is buried; (d) exposing the surface of the adhesive layer at a predetermined height. Chemical etch back And (m) between the steps (b) and (c), or after the step (d), the surface of the metal bump protruding from the surface of the insulating layer is processed to have an uneven surface. The present invention also provides a manufacturing method.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

FIG. 1A shows a wiring board 10 of the first invention.
FIG. This wiring board 10 has a structure in which an insulating layer 2 is formed on a conductive layer 1. Here, the insulating layer 2
Has a hole A reaching the conductive layer 1, and a metal plug 4 is formed in the hole A by an electroplating method. The tip of the metal plug 4 protrudes from the insulating layer 2 to form a metal. The bumps 5 are formed. The surface of the metal bump 5 is processed to have an uneven surface.

When the wiring board 10 of FIG. 1 (a) and the IC chip are joined together, the pads of the IC chip and the metal bumps 5 of the wiring board 10 are made to face each other, and an anisotropic conductive adhesive film or an anisotropic conductive film is used. It can be joined by thermocompression bonding with an adhesive paste or the like. Moreover, since the surface of the metal bumps 5 is processed to be uneven, the metal bumps 5 bite well into the pads of the IC chip, and deviations are less likely to occur, so that the connection reliability can be greatly improved.

FIG. 1 (b) is a schematic sectional view of the wiring board 10 of the second present invention. This wiring board 10 has a structure in which an insulating layer 2 is formed on a conductive layer 1 and an adhesive layer 3 is formed thereon. Here, a hole A reaching the conductive layer 1 is provided in the adhesive layer 3 and the insulating layer 2, and a metal plug 4 is formed in the hole A by an electrolytic plating method. The tip projects from the adhesive layer 3 to form a metal bump 5. The surface of the metal bump 5 is processed to have an uneven surface.

When the wiring board 10 of FIG. 1 (b) and the IC chip are joined, when the pads of the IC chip and the metal bumps 5 of the wiring board 10 are opposed to each other and thermocompression bonded, the pads and the metal bumps 5 are deformed. And the adhesive layer 3 is IC
Contact and adhere to the chip surface. Therefore, by using the wiring board 10 of the present invention, it becomes possible to directly bond the IC chip and the wiring board without using an anisotropic conductive adhesive film, an anisotropic conductive paste, or the like. Moreover, since the surface of the metal bumps 5 is processed to be uneven, the metal bumps 5 bite well into the pads of the IC chip, and deviations are less likely to occur, so that the connection reliability can be greatly improved. In this case, an anisotropic conductive adhesive film, an anisotropic conductive paste, or the like may be used for joining.

Copper foil is generally used as the conductive layer 1 in the first and second aspects of the present invention, but it is formed of other metal, gold, silver, aluminum, solder, nickel or the like or alloys thereof. Good.

The thickness of the conductive layer 1 can be appropriately determined according to the purpose of use of the wiring board. Further, the conductive layer 1 may be patterned if necessary.

In the first and second aspects of the present invention, the insulating layer 2 may have the same structure as the insulating layer of a general wiring board, and has insulating characteristics, heat resistance, moisture resistance and withstand voltage characteristics. An excellent polyimide layer is preferable. Among them, a polyimide layer obtained by imidizing a polyamic acid is particularly preferable. This is because it is easy to form holes accurately and easily by chemical etching before imidization.

The thickness of the insulating layer 2 can be appropriately determined according to the purpose of use of the wiring board.

As the adhesive layer 3, it is possible to use an adhesive layer made of an adhesive which is used when a general wiring board is manufactured. Preferably, an insulating thermoplastic polyimide layer having excellent affinity with the insulating layer 2, insulating properties, heat resistance, moisture resistance and withstand voltage properties is used.

The thickness of the adhesive layer 3 can be appropriately determined according to the purpose of use of the wiring board.

The metal plugs 4 filled in the holes A and the metal bumps 5 at the tips protruding from the adhesive layer 3 are:
It is a metal substance formed by an electrolytic plating method, and preferably an electrolytic copper plating plug (electrolytic copper plating bump) can be used.

The diameter and length of the metal plug 4 can be appropriately determined according to the purpose of use of the wiring board.

The diameter and height of the metal bumps 5 can be appropriately determined according to the purpose of use of the wiring board, but generally the diameter is 100 to 300 μm and the height is several tens μm.
Is about 100 μm.

The uneven processing of the surface of the metal bump 5 is performed by forming a smooth plated surface of the metal bump 5 formed by electrolytic plating as an uneven surface, and by the anchor effect of the uneven surface, it becomes an electronic component such as an IC chip. This is a process for joining with a wiring board with high connection reliability. A specific processing method for such a concavo-convex processing can be appropriately selected within a range that does not impair the effects of the present invention. For example, sandblast treatment, buff treatment, plating treatment, chemical polishing treatment, conductive particle adhesion treatment, etc. can be adopted. Of these, chemical polishing treatment is preferable. As a preferable example of the chemical polishing treatment, an etching treatment with an acid solution, particularly a hydrogen peroxide / sulfuric acid mixed solution (specifically, NBS series manufactured by Ebara Densan Co., Ltd., MB-110 manufactured by Japan MacDermid Co., Ltd.) is used. Etc.).

The timing for performing these processes will be described later.

If necessary, a noble metal plating layer such as gold may be appropriately formed on the surface of the metal bump 5 that has been subjected to the concavo-convex processing in order to improve conduction reliability.

The wiring boards of FIGS. 1 (a) and 1 (b) described above are wiring boards which can be electrically connected on both sides. For example, as shown in FIG. 2, as shown in FIG. The back surface of the wiring board may be patterned, if necessary, and then two or more wiring boards may be attached to form a multilayer structure. The multi-layering has an advantage that the manufacturing cost is lower than that of the conventional multi-layering technique using the general additive method.

Next, the method of manufacturing the wiring board according to the first aspect of the present invention will be described step by step.

Step (a) A hole A reaching the conductive layer 1 is formed in the insulating layer 2 on the conductive layer 1 by chemical etching using photolithography (FIG. 3C). More specifically, polyamic acid is applied onto the conductive layer 1 and dried to form the insulating layer precursor layer 6 (FIG. 3A). Then, a photosensitive resist is applied thereon and dried to form a photosensitive resist layer 7, and a protective film 8 is further laminated thereon (FIG. 3 (b)). Then, the photosensitive resist layer 7 is exposed to light through a photomask corresponding to the hole to be opened, developed to pattern the photosensitive resist layer 7, and the insulating layer precursor layer 6 is chemically etched using the patterned photosensitive resist layer 7 as an etching mask. To do. After the etching is completed, it is converted into a polyimide by a conventional method, and the photosensitive resist layer 7 and the protective film 8 are removed to form holes A.
Insulating layer 2 having is formed (FIG. 3C).

The chemical etching conditions are the insulating layer precursor layer 6
It can be appropriately determined according to the material, the size of the hole to be opened, and the like.

Step (b) Next, by electroplating using the conductive layer 1 as a cathode,
While forming the metal plug 4 in the hole A of the insulating layer 2, the metal plug 4 is further continuously grown by the electroplating method to form the metal bump 5 whose tip projects from the surface of the insulating layer 2 ( FIG. 3D). In this case, it is preferable to cover the outer surface 1a of the conductor layer 1 with a masking tape (not shown). Further, it is preferable to remove this masking tape after the step (m).

The electrolytic plating conditions can be appropriately determined according to the type of plated metal, the hole diameter, the plug size to be formed, and the like.

Step (m) Next, the surface of the metal bump 5 protruding from the surface of the insulating layer 2 is processed to have an uneven surface by chemical polishing or the like (FIG. 3).
(E)). The concavo-convex processing condition can be appropriately determined according to the metal type, the diameter, and the like of the metal bump 5. As a result, a wiring board as shown in FIG. 1 (a) is obtained.

Next, the method of manufacturing the wiring board of the second invention will be described step by step.

Step (a) Similar to step (a) in the method for manufacturing a wiring board according to the first aspect of the present invention, the conductive layer 1 is formed on the insulating layer 2 on the conductive layer 1 by chemical etching using photolithography. To form a hole A (FIG. 4C). More specifically, polyamic acid is applied on the conductive layer 1 and dried to form the insulating layer precursor layer 6 (FIG. 4A). Then, a photosensitive resist is applied thereon and dried to form a photosensitive resist layer 7,
Further, a protective film 8 is laminated thereon (FIG. 4).
(B)). Then, the photosensitive resist layer 7 is exposed to light through a photomask corresponding to the hole to be opened, developed to pattern the photosensitive resist layer 7, and the insulating layer precursor layer 6 is chemically etched using the patterned photosensitive resist layer 7 as an etching mask. To do. After the completion of etching, the photosensitive resist layer 7 and the protective film 8 are removed by imidization according to a conventional method to form the insulating layer 2 having the holes A (FIG. 4C).

The chemical etching conditions are the insulating layer precursor layer 6
It can be appropriately determined according to the material, the size of the hole to be opened, and the like.

Step (b) Next, similarly to the step (b) in the method for manufacturing a wiring board according to the first aspect of the present invention, the holes A of the insulating layer 2 are formed by the electrolytic plating method using the conductive layer 1 as a cathode. While forming the metal plug 4, the metal plug 4 is further continuously grown by an electrolytic plating method to form a metal bump 5 having its tip protruding from the surface of the insulating layer 2 (FIG. 4D). In this case, it is preferable to cover the outer surface 1a of the conductor layer 1 with a masking tape (not shown). Further, it is preferable to remove this masking tape after the step (m).

The electrolytic plating conditions can be appropriately determined depending on the type of plated metal, the hole diameter, the plug size to be formed, and the like.

Step (m) Next, similarly to the step (m) in the method for manufacturing a wiring board according to the first aspect of the present invention, the surface of the metal bump 5 protruding from the surface of the insulating layer 2 is roughened by chemical polishing or the like. It is processed (FIG. 4E). The concavo-convex processing condition can be appropriately determined according to the metal type, the diameter, and the like of the metal bump 5.

Step (c) Next, on the surface of the insulating layer 2 on which the metal bumps 5 are formed,
The adhesive layer 3 is formed so that the metal bumps 5 are buried (FIG. 4 (f)).

The adhesive layer 3 can be formed, for example, by applying a thermoplastic polyimide solution with a knife coater and drying it.

Step (d) Next, the surface of the adhesive layer 3 is chemically etched back so that the metal bumps 5 have a predetermined height (FIG. 4 (g)). As a result, a wiring board as shown in FIG. 1 (b) is obtained.

The chemical etchback conditions for the adhesive layer 3 can be appropriately determined according to the material of the adhesive layer 3, the material of the metal bumps 5, the required etchback amount, and the like. For example, when the adhesive layer 3 is a thermoplastic polyimide layer, an alkaline aqueous solution can be used as an etchant.

In the method for manufacturing a wiring board according to the second aspect of the present invention, the step (m) shown in FIG. 4 (e) is performed between the step (b) and the step (c). But process (m)
May be performed after step (d).

[0050]

EXAMPLES The present invention will be specifically described below by taking the case of manufacturing the wiring board of FIG. 1 (b) as an example.

Example 1 1.01 mol of pyromellitic dianhydride and 1.0 mol of 4,4'-diaminodiphenyl ether were placed on one surface of a copper foil having a thickness of 18 μm and N-methyl-2-, which was a solvent. The polyamic acid solution obtained by dissolving it in pyrrolidone is dried to a thickness of 1
It was applied to a thickness of 0 μm and dried.

On this polyamic acid layer, a photosensitive resist (NR-41 (nylon-oligoester-based resist), manufactured by Sony Chemical Co., Ltd.) was applied to a dry thickness of 8 μm and dried, and the thickness was further applied thereon. A 12 μm thick protective film (polyester film, manufactured by Toray Industries, Inc.) was laminated.

The photosensitive resist was exposed from the protective film side by irradiating it with light having a wavelength of 365 nm using a negative film as a photomask, and the photosensitive resist was patterned by developing with water.

Using the patterned photosensitive resist as an etching mask, the polyamic acid layer was chemically etched with an alkaline solution (etching temperature: 25 ° C., etching time: 15 seconds) to form a hole in the polyamic acid layer. Copper foil is exposed at the bottom of the hole, and the diameter of the bottom is 50μ.
The diameter of the pores on the surface of the polyamic acid layer was 80 μm.

Next, the polyamic acid layer in which the holes were formed was imidized to form an insulating layer (imidization heating temperature 350.
C, imidization heating time 10 minutes).

Next, after coating the outer surface of the copper foil with a masking tape, the copper foil is used as a cathode for electrolytic copper plating (copper sulfate plating bath, plating bath temperature 30 ° C., plating current density).
15 A / dm ² , plating time 30 minutes). As a result, it was possible to form a copper bump protruding to a height of 20 μm from the surface of the insulating layer.

Next, 3,4,3 ′, 4′-biphenyltetracarboxylic acid was formed so that a thermoplastic polyimide layer (adhesive layer) having a dry thickness of 20 μm could be formed on the entire surface of the insulating layer on the copper bump side. A knife coater was used to dissolve a polyamic acid solution obtained by dissolving 1.01 mol of dianhydride and 1.0 mol of 1,3-bis (3-aminophenoxy) benzene in N-methyl-2-pyrrolidone as a solvent. Was applied and dried.

Next, after chemically etching back the surface of the adhesive layer with an alkaline aqueous solution so that the exposed height of the copper bumps becomes 10 μm (etchback temperature 25 ° C., etchback time 15 seconds), polyamic acid was used. Was imidized to complete the thermoplastic polyimide layer.

Next, hydrogen peroxide /
Sulfuric acid mixed solution (NBS series, Ebara Densan Co., Ltd.) 3
By spraying for 0 seconds, washing with water, and drying, 0.
Concavities and convexities of 5 to 2 μm were formed. As a result, FIG.
The wiring board 10 shown in was obtained.

An IC chip is flip-chip mounted on this wiring board (bonding temperature 260 ° C., bonding time 10 seconds).
As a result, it was possible to perform bonding with high adhesive strength and high reliability of conduction.

[0061]

According to the wiring board of the present invention, electronic components such as IC chips can be mounted and joined with high connection reliability. Therefore, by using the wiring board of the present invention, a chip size package of IC chips becomes possible.

Also, a multilayer wiring board and a rigid-flexible wiring board can be produced from these wiring boards.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a wiring board of the present invention.

FIG. 2 is a schematic cross-sectional view of a multilayer wiring board using the wiring board of the present invention.

FIG. 3 is a manufacturing process diagram of the wiring board of the present invention.

FIG. 4 is a manufacturing process diagram of the wiring board of the present invention.

FIG. 5 is a schematic sectional view of a conventional wiring board.

FIG. 6 is a manufacturing process diagram of a conventional wiring board.

[Explanation of symbols]

1 conductive layer, 2 insulating layer, 3 adhesive layer, 4 metal plug, 5 metal bump, 10 wiring board

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-269970 (JP, A) JP-A-8-70019 (JP, A) JP-A-9-148380 (JP, A) JP-A-10- 27829 (JP, A) JP 10-321758 (JP, A) JP 2000-22300 (JP, A) Actual development 2-41433 (JP, U) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) H01L 21/60 H01L 21/12

Claims (4)

(57) [Claims] 1. An insulating layer and an adhesive layer are formed on the conductive layer, and a hole reaching the conductive layer is provided in the adhesive layer and the insulating layer, and electrolytic plating is performed in the hole. A metal plug is formed by a method, a tip of the metal plug constitutes a metal bump protruding from the adhesive layer, and the surface of the metal bump is processed to have an uneven surface .
In the manufacturing method, the following steps (a) to (d) and
(M): (a) Photolithographic method is used for the insulating layer on the conductive layer
By chemical etching to form holes reaching the conductive layer.
Extent; (b) insulated by an electrolytic plating method using the conductive layer as the cathode
While continuously forming the metal plug in the layer hole,
The tip of the metal plug is grown by electrolytic plating
Forming a metal bump protruding from the surface of the insulating layer; (c) forming a metal bump on the surface of the insulating layer on which the metal bump is formed.
A step of forming an adhesive layer so that the bumps are buried; (d) exposing the surface of the adhesive layer with the metal bumps at a predetermined height
To chemically etch back with an alkaline aqueous solution.
And; (m) between step (b) and step (c), or
After (d), the metal bumps protruding from the surface of the insulating layer
Characterized in that it includes a step of processing unevenness on the surface
Manufacturing method. 2. A roughened processing method according to claim 1, wherein the chemical polishing process. 3. A step (a), the polyamic acid was coated on the conductive layer, the manufacturing method according to claim 1 or 2, wherein the insulating layer is formed by imidizing after forming the hole by photolithography . 4. A thermoplastic polyimide layer having an insulating adhesive layer.
And the metal plug is an electrolytic copper plated plug.
The manufacturing method according to any one of 1 to 3.