JP3543348B2 - Manufacturing method of multilayer wiring board - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for manufacturing a multilayer wiring board.
[0002]
[Prior art]
As a method for manufacturing a multilayer wiring board, basically, one or more inner layer wiring formed bodies having inner layer wiring formed by etching are bonded to a resin material for bonding, and thereafter, if necessary, through holes are formed and plating is performed. There are known various methods of manufacturing by performing a series of outer layer wiring forming processes for performing etching and then performing etching or the like.
If the adhesive strength between the inner wiring and the resin material for adhesion is low, problems such as blistering and peeling during soldering occur. In order to improve the adhesive strength, there is a method using a double-sided roughened copper foil provided with irregularities on both surfaces in advance. Also, using a normal single-sided roughened copper foil, an oxidation treatment called blackening treatment after forming the inner layer wiring with the unroughened surface as an exposed surface, that is, a treatment for improving the adhesion by providing fine copper oxide unevenness. It has been known. Furthermore, there is known a method in which a copper foil subjected to blackening treatment is formed into an uneven surface of metallic copper by a method such as reduction or dissolution while leaving fine unevenness.
[0003]
[Problems to be solved by the invention]
In the case of a method using a double-sided roughened copper foil in which both surfaces are previously provided with irregularities, it is necessary to perform a roughening step on both sides of the copper foil. After the etching resist is formed, unnecessary portions are removed by etching to form wiring. At this time, if there is a foreign substance or dirt on the copper foil surface, poor adhesion of the etching resist may be caused, or conversely, etching may be prevented. Therefore, there is a problem that wiring failure occurs. Therefore, usually, polishing is performed before forming the etching resist. In the case of a double-sided roughened foil, the process from lamination bonding to obtain a substrate with a double-sided roughened foil to the formation of the inner layer wiring is handled in a state where the uneven surface is exposed. Easy to stick. Despite this, irregularities on the roughened surface are flattened, so that normal polishing cannot be performed, and when fine wiring is formed, there is a problem that the yield is reduced due to wiring defects caused by foreign matter and dirt. is there. Further, there is also a problem that unevenness of the exposed roughened surface is easily crushed or damaged due to mutual contact or contact with a processing device.
[0004]
In the case of using a single-sided roughened copper foil and performing a blackening process after forming the inner layer wiring, the copper oxide generated by this process is easily dissolved in an acid. For this reason, it is known that in the manufacturing process of the wiring board performed after the multi-layer lamination, the treatment liquid infiltrates from the wall surface of the through-hole provided for the through-hole and causes a problem called pink ring or haloing.
[0005]
Therefore, further, a method of reducing the blackened copper foil to metal copper only by a method such as reduction while leaving fine irregularities (Japanese Patent Publication No. 64-8479) or removing only the oxide film on the extreme surface, A method of leaving fine uneven surfaces of metallic copper is performed. In the case of these methods, if they can be processed normally, satisfactory characteristics can be obtained.However, it is necessary to appropriately perform blackening treatment, and further, that processing equipment for converting to metallic copper is required, and liquid management is appropriate. In addition, the blackening process is generally performed by immersion because the processing temperature is high and the processing time is long, and it is not always easy to perform a certain amount of processing because the equipment becomes large in size. It was not something.
[0006]
[Means for Solving the Problems]
The method of manufacturing a multilayer wiring board according to the present invention is a method of manufacturing a multilayer wiring board by bonding at least one inner wiring forming body having an inner wiring formed by etching to a resin material for bonding, and thereafter performing outer wiring forming processing. In the manufacturing method of the board, as the metal foil forming the inner layer wiring,
(1) A first copper layer whose surface has a roughness suitable for bonding to a resin, a second copper layer on the opposite surface, a first copper layer and a second copper layer A nickel or nickel-containing alloy layer of 0.05 to 2.0 microns provided in the middle of the layer,
(2) having a roughness suitable for bonding with a resin by selectively removing the second copper layer;
And a bonding step with a resin material after removing at least the second copper layer.
[0007]
There are no particular restrictions on the type of resin used for the resin layer at this time, and thermosetting resins such as epoxy resins, phenol resins, polyimide resins, and BT ranges, and modified resins thereof, as well as fluororesins and polyether sulfones And heat-softening resins having a relatively high heat deformation temperature.
[0008]
The resin layer may contain woven or nonwoven fabric of paper, resin, or glass. Further, organic or inorganic fillers may be included.
When using a prepreg or a film, heat lamination bonding can be used. Alternatively, a method of directly applying a resin material, heat curing, and forming wiring by plating may be employed.
[0009]
When forming a high-current circuit, the thickness of the first copper layer needs to be increased, and when the current is small as in a signal circuit, high-density wiring is often required. In this case, the thinner the better, from the viewpoint of forming fine wiring by etching. From these, the thickness is generally between 5 and 150 microns.
When the inner layer connection is made by a through hole, the thickness is 10 to 150 μm from the viewpoint of the reliability of the inner layer connection.
[0010]
The thickness of the second copper layer is (1) to provide sufficient unevenness to obtain the necessary adhesive strength between the inner layer wiring and the resin, and (2) the production of the copper foil is performed on a roll-to-roll basis. On the roughened surface of the copper layer, nickel, or an alloy layer containing nickel, and then forming the first copper layer sequentially by plating is excellent in productivity, but it is not broken by the tension applied at this time. It is determined from two points, and the thickness is preferably 5 microns or more. Although there is no clear standard, the upper limit is about 60 microns in consideration of handling efficiency, manufacturing cost of the foil, and economical efficiency such as etching cost when the foil is removed later. Further, in consideration of economy, 20 μm or less is more desirable.
[0011]
The target multilayer wiring board is not particularly limited, and is a multilayer wiring board formed by general pressurization and heating lamination, a multilayer wiring board in which wiring is multilayered by successive stacking, a metal core wiring board having a metal core, a metal core wiring board, or the like. This includes a single-sided metal-based multilayer wiring board or the like in which wiring is stacked on one side of a board.
[0012]
As the metal foil for forming the inner layer wiring, (1) a first copper layer whose surface is a circuit having a roughness suitable for bonding to a resin, and a second copper layer present on a surface opposite to the surface having the roughness. A copper layer and a nickel or nickel-containing alloy layer of 0.05 to 2.0 microns provided between the first copper layer and the second copper layer; (2) the second layer First, the first copper layer is bonded by using a metal foil that satisfies both (1) and (2) of having a roughness suitable for bonding with a resin by selectively removing the copper layer. By adhering to the surface as a resin, a metal foil-clad base for forming an inner layer wiring is produced.
[0013]
As a method of forming a roughened surface on the copper layer, a known method can be used, and a method of contacting with a soft etching solution, a method of performing electrolytic plating under specific conditions, and an electroless plating method that adjusts conditions to form an uneven surface In addition to the method of performing displacement plating, vapor deposition, and the like, there is a method of performing mechanical roughening by sandblasting or a belt sander.
From the viewpoint of rust prevention, it is preferable that the metal foil is subjected to rust prevention treatment such as imidazole, chromate, zincate or the like.
[0014]
For forming the inner layer wiring on the metal foil-clad substrate, various methods in which the order of steps and the like are changed can be considered. An example is shown below.
The second copper layer of the metal foil-clad substrate is selectively etched. As an etchant that can be used at this time, an alkaline etchant called Process A (trade name, manufactured by Meltex) can be used.
Next, nickel or an alloy layer containing nickel is selectively etched. Examples of the etchant that can be used at this time include an etchant containing nitric acid and hydrogen peroxide as main components and an etchant containing sodium nitrobenzenesulfonate as a main component.
Thereafter, an etching resist is formed, and an inner wiring is formed by etching.
At this time, the surface of the inner layer wiring has the above-mentioned uneven surface of the second copper layer, and a sufficient adhesive force between the surface and the resin can be obtained. Therefore, the object can be achieved by exposing the second copper layer and performing multi-layer bonding. Thereafter, necessary outer layer wirings are formed.
[0015]
As another example, in the above-described example, when nickel or an alloy layer containing nickel is exposed and a non-selective etchant such as cupric chloride or ferric chloride is used, nickel Alternatively, the alloy layer containing nickel and the first copper layer can be simultaneously etched. Thereafter, the alloy layer containing nickel may be selectively etched, or nickel or an alloy layer containing nickel may be left as long as it does not matter. Thereafter, multi-layer bonding and outer layer wiring formation are performed.
In addition to the foregoing, there are a variety of implementations, and this patent is not limited by example, as noted above.
[0016]
[Action]
In the present invention, the second copper layer protects the first copper layer for forming the wiring, and prevents the first copper layer from being damaged or stained. In addition, dirt and foreign matter on the first copper layer can be removed by a general polishing process used in manufacturing a wiring board. If the second copper layer is removed immediately before forming the wiring, it is possible to prevent the first copper layer from being damaged after the removal of the second copper layer.
This second copper layer has not only the above-mentioned protective effect, but also provides irregularities in advance at the boundary surface with the first copper layer (or nickel or an alloy layer containing nickel), whereby the second copper layer Irregularities are given to the exposed surface of the first copper layer (or nickel or an alloy layer containing nickel) after the removal, and a sufficient adhesive force between the exposed surface and the resin is obtained.
[0017]
【Example】
As an example, an embodiment performed on a wiring board using an epoxy resin impregnated glass cloth will be described.
(Manufacture of metal foil)
The surface of the stainless steel was subjected to electrolytic copper plating with a thickness of 30 μm and an average surface roughness of 7 μm by copper sulfate plating.
Next, nickel plating having a thickness of 1 micron was performed as an intermediate layer. This was subjected to electrolytic copper plating with a particle size of 1 to 2 microns after electrolytic copper plating of 20 microns.
Thus, a metal foil having the configuration shown in FIG. 1 was obtained.
(Manufacture of wiring boards)
The following description is based on FIG.
(A) The metal foil 1 of FIG. 1 was laminated and adhered to both surfaces of a substrate 2 in which a glass cloth was impregnated with an epoxy resin.
(B) The second copper layer 13 of the laminate was etched with an alkaline etchant. Next, the nickel layer 12 was removed by etching with a nitric acid-based etchant.
(C) After laminating the dry film, exposure and development were performed to form a resist pattern for etching. After forming a pattern by etching with a cupric chloride-based etchant, the dry film was peeled off to obtain an inner layer plate.
(D) A prepreg impregnated with an epoxy resin and a copper foil were laminated and bonded to a glass cloth.
(E) A through-hole 5 was formed in a necessary place.
(F) Panel copper plating was performed.
After that, the outer wiring 421 was formed by etching to obtain a multilayer wiring board (FIG. 3).
[0018]
【The invention's effect】
According to the present invention, a multilayer wiring board can be easily manufactured without requiring a special treatment such as a blackening treatment. Similarly, compared to the case where a double-sided roughened foil that can be easily manufactured is used, handling and the like are easier, and the yield becomes higher when fine wiring is formed.
In addition, in the case of this patent, since the time required for etching and removing the second copper layer and removing the nickel or nickel-containing alloy layer is short, a horizontal transfer type device can be used, and the structure of the production line can be simplified. is there.
[Brief description of the drawings]
FIG.
It is sectional drawing of the metal foil for inner layer wiring formation used for one Example of this invention.
FIGS. 2A to 2F are cross-sectional views in respective steps for explaining one embodiment of the present invention.
FIG. 3 is a sectional view of a wiring board showing one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Metal foil 11 ... First copper layer 12 ... Nickel 13 ... Second copper layer 2 ... Resin base material 3 ... Resin base material 41 ... Copper foil 42 ... Plated copper 5 ... Through hole 111 ... Inner wiring 421 ... Outer layer wiring

Claims (4)

An inner layer wiring formed body in which an inner layer wiring is formed by etching and a resin material for bonding are adhered, and thereafter, an outer layer wiring forming process is used to manufacture a multilayer wiring board. A metal foil for forming an inner layer wiring,
(1) Three layers of a first copper layer serving as an inner layer wiring, a nickel layer having a thickness of 0.05 to 2.0 μm, and a second copper layer are laminated in this order;
(2) the surface of the first copper layer has a roughness suitable for bonding the inner layer wiring formed body to the resin base material;
(3) unevenness is provided on a boundary surface between the second copper layer and the nickel layer, and the unevenness is transferred to the back side of the nickel layer and the first copper layer;
(4) The surface of the exposed first copper layer or nickel layer having a roughness suitable for bonding to a resin material by removing the second copper layer or the second copper layer and the nickel layer. Becomes;
A metal foil for forming an inner layer wiring, characterized in that: The metal foil according to claim 1, wherein the second copper layer has a thickness of 5 to 60 microns. 3. The metal foil for forming an inner layer wiring according to claim 1, wherein the thickness of the first copper layer is 5 to 150 microns. A method for manufacturing a multilayer wiring board using the metal foil for forming an inner layer wiring according to claim 1,
(1) laminating a resin base material on the surface of the first copper layer of the inner layer wiring forming metal foil;
(2) removing the second copper layer or the second copper layer and the nickel layer;
(3) forming an inner wiring on the first copper layer to produce an inner wiring forming body;
(4) adhering a resin material to the inner layer wiring forming body;
A method for manufacturing a multilayer wiring board, comprising:

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