JP2003092472A - Manufacturing method of laminated foil for forming multi-layer wiring board and multi-layer wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a laminated foil for forming a multi-layer wiring board with which a wiring board capable of coping with high density can be provided at a lower cost, by forming a wiring board using a laminated foil having a surface layer consisting of metal or an alloy with a low-melting point and using a selective etching technique and a diffusion joining technique, and to provide a manufacturing method of a multi-layer wiring board using the same. SOLUTION: In the laminated foil for forming a multi-layer wiring board, a surface layer made of a metal or an alloy having a melting point not greater than 350 deg.C is formed on both surfaces or one surface of a laminated foil, in which an intermediate layer made of a metal or an alloy having an etching characteristic being different from that of a Cu foil or a Cu alloy foil is arranged so as to be sandwiched by the Cu foil or the Cu alloy foil.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated foil for forming a multilayer wiring board and a method for manufacturing a multilayer wiring board using the same.

[0002]

2. Description of the Related Art In recent years, with the rapid spread of portable information devices such as mobile phones and notebook computers, the weight, size and performance of the devices have been rapidly increasing. On the other hand, high density is required. In response to this, in printed wiring boards and semiconductor package wiring boards, fine wiring patterns and narrower pitches are being promoted, while multilayer wiring boards are becoming the mainstream.

Regarding inter-layer connection of a conventional multilayer wiring board,
For example, as shown schematically in FIG. 6, (a) double-sided Cu-clad resin (2
Using (1), (b) after forming a hole that penetrates the Cu (23) and the resin (22), (c) performs Cu plating (24) inside the hole to obtain conduction between layers, d) A method of forming a desired wiring pattern is used. In this technique, a so-called through hole (25) is formed using a drill or a laser, and through hole plating is performed. Further, for example, as schematically shown in FIG. 7, (e) resin-coated copper foil (27) is provided on both sides of the patterned core substrate (26).
Position, (f) build up, (g) use a laser to make holes stop in the inner wiring layer, and (h) hole surface C
u plating (i) forming a wiring pattern, so-called IVH (28)
(Interstitial Via Hole) is the mainstream.

[0004]

In the wiring board having the through holes, laser drilling is necessary to cope with high density, and in the wiring board having the IVH, laser drilling is indispensable. However, laser drilling has poor positioning accuracy of ± several tens of μm and requires a large pad, which reduces the flexibility of wiring design and increases the cost of laser drilling as the number of holes increases. However, there are many factors that hinder high density. In addition, since the wiring and lands (including the leading wiring) are formed by etching after laser drilling and plating, the wiring thickness increases,
There is also a problem that it is difficult to miniaturize the wiring. An object of the present invention is to form a wiring board using a selective etching technology and a diffusion bonding technology using a laminated foil having a surface layer made of a metal or an alloy having a low melting point, and thus a wiring board that can cope with high density. It is an object of the present invention to provide a laminated foil for forming a multilayer wiring board which can be provided at a lower cost, and a method for manufacturing a multilayer wiring board using the same.

[0005]

Means for Solving the Problems The present inventors have formed a wiring board using a selective etching technique and a diffusion bonding technique using a laminated foil having a surface layer made of a metal or alloy having a low melting point. The present invention has been accomplished by finding that the laser process and the plating process are unnecessary, and the wiring density of the wiring board can be increased and the cost can be reduced.

That is, the present invention provides an intermediate layer made of a metal or alloy having a different etching characteristic from the Cu foil or Cu alloy foil,
For forming a multilayer wiring board in which a surface layer made of a metal or an alloy having a melting point of 350 ° C. or lower is formed on the surface of both or either of the laminated foils arranged so as to be sandwiched by the Cu foil or the Cu alloy foil. It is a laminated foil. Preferably, the surface layer is Sn
Alternatively, it is a laminated foil for forming a multilayer wiring board made of an Sn alloy. More preferably, it is a laminated foil for forming a multilayer wiring board in which the intermediate layer is Sn or a Sn alloy. Further, it may be a laminated foil for forming a multilayer wiring board in which the intermediate layer is made of Ti or a Ti alloy.

Furthermore, the method for producing a multilayer wiring board of the present invention uses one of the above-mentioned laminated foils for forming a multilayer wiring board, wherein one surface layer and the surface layer are formed so that etching stops at the intermediate layer. A Cu foil or Cu alloy foil continuous with the layer is etched to form a bump having a surface layer, and another bump is formed in such a state that the bump having the surface layer penetrates the insulator.
This is a method for manufacturing a multilayer wiring board in which bumps having the above-mentioned surface layer are butted against a Cu foil or Cu alloy foil and heated and pressed to obtain interlayer connection.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. As shown in FIG. 1, an important feature of the present invention is that an intermediate layer (1) made of a metal or an alloy having a different etching property from a Cu foil or a Cu alloy foil, and a Cu foil or a Cu foil arranged so as to sandwich the intermediate layer (1). This is because the surface layer (4) made of a metal or alloy having a low melting point was formed on the surface of the laminated foil (3) made of the Cu alloy foil (2). The greatest advantage of using the laminated foil of the present invention is that it takes advantage of the thermal history of the process, and the surface layer (4) and Cu foil or C
The diffusion phenomenon with the u-alloy foil (2) makes it possible to establish a strong interlayer connection, and a highly reliable via-on-via structure can be realized at low cost, allowing a high degree of freedom in high-density wiring design. In point. Further, since the surface layer is formed before the bump forming step, compared with the case where the surface layer is formed after the bump forming, for example, paste application or plating step is not required, and the step is short and effective.

The method for manufacturing a wiring board using the laminated foil for forming a multilayer wiring board of the present invention will be described below in detail.
For example, as shown in FIG. 2, first, (a) an intermediate layer (1) made of a metal or alloy having a different etching property from the Cu foil or Cu alloy foil (2) is formed by Cu foil or Cu alloy foil (2). A laminated foil for forming a multilayer wiring board is prepared in which a surface layer made of a metal or an alloy having a melting point of 350 ° C. or lower is formed on the surface of a Cu foil or Cu alloy foil (2A) on one side of the laminated foil having a sandwiched structure. The surface layer may be formed on one side as shown in FIG. 2 or may be formed on both sides. The following description will be given with reference to FIG. (b) A photosensitive resist (5) is attached to both sides of the photosensitive resist. As the photosensitive resist, a dry film type may be laminated, or a liquid type may be applied by a method such as dipping or spin coating. A film or glass plate on which a desired pattern is drawn is placed on the attached photosensitive resist, exposed and developed to form an etching mask.

Next, (c) the surface layer (4) and a Cu foil or Cu continuous inside the surface layer (4).
Bumps (6) are formed on the alloy foil (2A) by selective etching. Selective etching in this case, first, the surface layer can be selectively etched, the Cu foil or Cu alloy foil using an etching solution that functions as an etching barrier, patterning the surface layer, then Cu foil or Cu alloy foil It can be selectively etched, and the inner layer can be patterned into a continuous Cu foil or Cu alloy with an etching solution that functions as an etching barrier, or the surface layer and Cu foil or Cu alloy foil can be selectively etched, Etching may be performed in the same step using an etching solution whose intermediate layer functions as an etching barrier. Further, (d) the exposed portion of the intermediate layer (1) is selectively etched. This step may be performed after the wiring patterning described later (FIG. 3H). The selective etching solution may be an etching solution capable of etching the intermediate layer and allowing the Cu foil or Cu alloy foil to function as an etching barrier.

Next, the photosensitive resist formed in (e) and (b) is removed to obtain a bumped Cu foil or Cu alloy foil (7). Then, as shown in FIG. 3, (f) the bumped Cu foil or Cu alloy foil obtained in FIG. 2 (7)
Then, an insulator (8) and Cu foil or Cu alloy foil (2C) are prepared.
Here, the insulator may be attached to the Cu foil with bumps or the Cu alloy foil. Resin and ceramics are good materials. It is preferably a resin and may be thermoplastic or thermosetting. Then, (g) hot pressing is performed so as to pierce the insulator (8) with the bump (6), and the bump and the Cu foil or the Cu alloy foil (2C) are joined via the surface layer (2). (h) The Cu foil or Cu alloy foil (2B, 2C) on the outside is etched to form wirings, lands, and pads to obtain a two-layer wiring board (11).

Further, as shown in FIG. 4, it is possible to obtain a four-layer wiring board (12) by laminating it, or further laminating it to increase the number of layers. Also, as shown in FIG. 5, nickel plating (15) and gold plating are applied to the pad portion of the double-layer wiring board (11).
(16), cover other wiring parts with solder resist (13),
The chip (17) is fixed to the wiring board with the die bond (18), the chip and the wiring board are connected with the gold wire (19), the sealing resin (20) is sealed with the chip and the gold wire, and the other side Solder ball (1
4) can be installed and packaged. The wiring board may have a multilayer structure of two or more layers. The connection between the chip and the wiring board may be flip chip connection.

As described above, by using the laminated foil for a multilayer wiring board and the method for manufacturing a multilayer wiring board according to the present invention, an expensive laser drilling step and Cu plating step can be eliminated, and a highly versatile etching step and hot etching step can be performed. A wiring board that can handle high-density wiring can be obtained at low cost in the pressing process. Moreover,
Since the diffusion phenomenon between Cu or Cu alloy foil and low melting point metal is used for interlayer connection, highly reliable bonding can be obtained.

Here, the structure of the laminated foil for forming a multilayer wiring board of the present invention will be specifically described. When a Cu foil or a Cu alloy foil is used for wiring formation, a pattern is formed by selective etching. Therefore, a thinner thickness is preferable because finer wiring can be formed at a narrow pitch. Also, in the case of forming bumps, it is preferable to be thin in order to realize a narrow pitch. However, if the thickness is too thin to control etching, a uniform pattern cannot be obtained, and wrinkles or the like may occur during transportation during the process or during hot pressing, for example. Therefore, Cu foil or Cu that forms bumps and wiring
The thickness of alloy foil is in the range of 25μm-150μm, 3μm-
It should be in the range of 50 μm. Furthermore, each 35 μm
The thickness is preferably in the range of ˜115 μm and in the range of 9 μm to 35 μm.

On the other hand, the thickness of the intermediate layer must be such that it functions as an etching barrier, and it is preferable that it be as thin as possible so that it can be quickly removed by selective etching. The thickness of the barrier layer varies depending on the material, but is 0.05 μm-5
It is preferably in the range of μm, more preferably 0.1 μm
It is in the range of m to 1 μm. In addition, the thickness of the surface layer is preferably thin because it is patterned by etching, but it is necessary that the surface layer can absorb the surface roughness of the copper foil or the copper alloy foil and sufficiently contribute to diffusion bonding. . Therefore,
The range of 0.1 μm to 5 μm is preferable. More preferably,
It is in the range of 0.5 μm to 2 μm.

Next, the Cu foil or Cu alloy foil may be either rolled or electrolytic. As for the composition, in addition to pure Cu, Cu-Fe alloys used for lead frames, Cu-
Fe-Co alloy, Cu-Ni-Si alloy, Cu-Cr-Ti alloy, Cu-Cr
-Select from Zr-based alloys, Cu-Zr-based alloys, etc. Here, the alloy means an alloy containing the metal as a main component. The Cu or Cu alloy foils on both sides of the intermediate layer may be different materials. Cu is preferable in consideration of electric resistance and availability. Further, when strength is required, Cu alloy is preferable.

As the selective etching solution for the conductor layer, a ferric chloride solution, a cupric chloride solution, an alkaline etchant, a hydrogen peroxide solution-sulfuric acid type etchant and the like which are generally used as an etching solution for copper are preferable. In particular, the ferric chloride solution is inexpensive, is generally used, and is suitable. As the barrier layer, a metal is suitable because it can be selectively etched with respect to Cu foil or Cu alloy foil, and it is necessary to obtain conduction between the layers, and it functions as a barrier against the selective etching liquid for the conductor layer described above. Preferred are Ni, Sn, Ti, Ag metals or alloys. Ni, Sn, Ti, and Ag function as a barrier against the alkaline etchant. Ti and Ag function as barriers to the ferric chloride solution and the cupric chloride solution. Al functions as a barrier against the hydrogen peroxide-sulfuric acid type etchant. Sn is effective because it can be easily formed in the process described below. Also, Ti
Is preferable because it has an etching barrier property with respect to a typical etchant.

The surface layer needs to be a metal or alloy having a melting point of 350 ° C. or lower. Here, for metals or alloys with a melting point above 350 ° C, diffusion is not sufficiently promoted at low temperatures (300 ° C or less) such that the wiring boards are laminated and hot pressed onto Cu foil or Cu alloy foil, and sufficient bonding is achieved. Can't get As the metal having a melting point of 350 ° C. or lower, metals such as Sn, Bi, Cd, In and Pb or alloys containing these as the main components are preferable. Among them, Sn is preferable because it has a high diffusion rate with Cu even at a low temperature and forms a stable and strong intermetallic compound. In particular,
The combination of surface layer / Cu foil or Cu alloy foil / intermediate layer / Cu foil or Cu alloy foil is preferably Sn / Cu / Ti / Cu or Sn / Cu / Sn / Cu.

As a method for producing the laminated foil of the present invention, a method of sequentially laminating by plating, a method of combining a plating method or a dry film forming method and a surface activated bonding method, and the like are preferable. The dry film forming method refers to all dry film forming methods using vapor phase or plasma, such as physical vapor deposition method and chemical vapor deposition method. A method of forming a film by ionizing and accelerating a material that has been heated in a vacuum and evaporating, a method of striking a desired atom by bombarding a gas ion like sputtering, or a special crucible is used. It also includes a molecular beam vapor deposition method in which a material is drawn out in a molecular beam shape and evaporated (above, physical vapor deposition method), and a film forming method in which a certain gas is heated and reacted like a chemical vapor deposition method.

Among them, physical vapor deposition methods such as vacuum vapor deposition method, sputtering method and ion plating method, which have been remarkably accelerated in recent film forming technology, are suitable. The vacuum deposition method has high deposition rate and good productivity. The sputtering method can be applied even when the metal to be the conductor layer is a high melting point metal,
The metal used as the conductor layer has a wide selection range, and a dry film-forming layer formed by any method enables uniform and uniform film formation.

Specifically, for example, a metal or an alloy to be a surface layer and an intermediate layer is formed on both surfaces of a Cu foil or a Cu alloy foil by a plating method or a dry film forming method, and Cu prepared separately from the surface of the intermediate layer. It is advisable to perform ion bombardment with the surface of the foil or Cu alloy foil in an inert atmosphere, and join so that the activated surfaces face each other. Here, the plating method is particularly effective when the surface layer and the intermediate layer are made of the same material, and is efficient because the surface layer and the intermediate layer can be simultaneously formed. Therefore, when Sn is used as the surface layer, it is effective to use Sn for the intermediate layer as well. On the other hand, in the dry film forming method, a material which cannot be obtained by the plating method can be used as the surface layer and the intermediate layer, but the film can be formed only on each side.

As another method, two Cu foils or Cu alloy foils are prepared, and a material to be an intermediate layer is formed on one surface of each by a dry film forming method in a vacuum tank. It is advisable to butt and bond each other to produce a three-layer laminated foil, and form a surface layer on the surfaces of both sides or one side thereof by a plating method or a dry film forming method. Here, when the film is formed by the plating method, it may be more efficient to form the film on both surfaces, and it may be a five-layer laminated foil, but even in the case of a five-layer laminated foil, it is essentially The effect of the present invention is recognized. The laminated foil of the present invention is not limited to the one produced by the above manufacturing method.

By using the laminated foil for forming a multilayer wiring board of the present invention, it is possible to provide a wiring board which can cope with high density without costing laser drilling and Cu plating at a lower cost.

[0024]

According to the present invention, by using a laminated foil having a surface layer made of a metal or an alloy having a low melting point, a wiring board is formed by utilizing a selective etching technique and a diffusion bonding technique, thereby increasing the density. It is possible to provide a multilayer wiring board that can meet the above requirements at a lower cost.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a laminated foil for forming a multilayer wiring board of the present invention.

FIG. 2 is a schematic view showing an example of a method for manufacturing a Cu foil with bumps or a Cu alloy foil using the laminated foil for forming a multilayer wiring board of the present invention.

FIG. 3 is a schematic view showing an example of a method for manufacturing a multilayer wiring board according to the present invention.

FIG. 4 is a schematic view showing an example of a method for manufacturing a multilayer wiring board according to the present invention.

FIG. 5 is a schematic cross-sectional view showing an example of a package using a wiring board manufactured from the laminated foil for forming a multilayer wiring board of the present invention.

FIG. 6 is a schematic view showing an example of a conventional interlayer connection method.

FIG. 7 is a schematic diagram showing an example of a conventional interlayer connection method.

[Explanation of symbols]

1. Intermediate layer, 2, 2A, 2B, 2C. Cu foil or Cu alloy foil, 3. Laminated foil, 4. Surface layer, 5. Photosensitive resist,
6. Bump, 7. Cu foil or Cu alloy foil with bumps, 8.
Insulator, 9. Land, 10. Wiring, 11. Two-layer wiring board,
12. Four-layer wiring board, 13. Solder resist, 14. Solder balls, 15. Nickel plating, 16. Gold plating, 17.
Chip, 18. Die bond, 19. Gold wire, 20. Sealing resin, 21. Double-sided Cu-clad resin, 22. Resin, 23. Cu,
24. Cu plating, 25. Through hole, 26. Core substrate, 27. Cu foil with resin, 28. IVH

Claims (5)

[Claims] 1. A surface of both or one or both of a laminated foil in which an intermediate layer made of a metal or an alloy having a different etching characteristic from a Cu foil or a Cu alloy foil is arranged so as to be sandwiched between the Cu foil or the Cu alloy foil. A laminated foil for forming a multilayer wiring board, characterized in that a surface layer made of a metal or an alloy having a melting point of 350 ° C. or lower is formed on. 2. The laminated foil for forming a multilayer wiring board according to claim 1, wherein the surface layer is made of Sn or Sn alloy. 3. The laminated foil for forming a multilayer wiring board according to claim 1, wherein the intermediate layer is made of Sn or Sn alloy. 4. The laminated foil for forming a multilayer wiring board according to claim 1, wherein the intermediate layer is made of Ti or a Ti alloy. 5. The multilayer foil for forming a multilayer wiring board according to any one of claims 1 to 4, wherein one surface layer and a Cu foil continuous with the one surface layer so that etching is stopped at the intermediate layer, or The Cu alloy foil is etched to form bumps having a surface layer, and the bumps having the surface layer are formed on another Cu foil or Cu alloy foil while the bumps having the surface layer penetrate the insulator. A method for manufacturing a multilayer wiring board, which comprises butting, heating and pressing to obtain interlayer connection.