JP2903814B2 - Manufacturing method of wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wiring board.

[0002]

2. Description of the Related Art Conventionally, copper foils having a thickness of 18 to 35 .mu.m have been generally used in the production of wiring boards from the viewpoint of wiring formability and ease of handling of copper foils. However, in response to recent high densification, five wires are also provided between component holes with a pitch of 2.54 mm, and ultra-thin copper foil with a thickness of 5 to 12 μm, which is advantageous for forming fine wires, is being studied. Is being started to be published in the magazine “Electronic Technology” published by Nikkan Kogyo Shimbun 1991
-June, 33, 8, p.
Particularly, it is described in P101 of the magazine and Table 1 that ultra-thin copper foil having a thickness of 5 to 9 μm is generally provided with an aluminum carrier from the viewpoint of handleability.

[0003]

When a copper foil with an aluminum carrier is used as a copper foil at the time of lamination to form fine wiring, it is necessary to completely remove aluminum on the surface. As a method therefor, there are a method of mechanically peeling off and a method of dissolving and removing. When it is mechanically peeled off, it is difficult to completely remove it, and when it is dissolved and removed with an acid or an alkali, a large amount of hydrogen is generated, which is dangerous. In addition, in the case of copper foil with an aluminum carrier, since the size of the irregularities on the surface in contact with the base material is limited by the thickness of the copper foil portion, the thinner the copper foil thickness, the stronger the peeling strength of the copper foil. However, there was a problem that was reduced. Further, when copper is used for the wiring, in a wiring board on which fine wiring is formed, there is a problem that copper ions start to melt from the wiring, thereby lowering insulation reliability. The present invention provides a method for manufacturing a wiring board that does not generate a large amount of hydrogen, has good peeling strength of a copper foil, and has high insulation reliability. It is intended to provide a method for manufacturing a wiring board including the same.

[0004]

According to the manufacturing method of the present invention, a metal foil composed of four layers of two kinds of metal layers having different etching conditions, a copper layer, and an anti-corrosion metal layer is laminated on a substrate. A step of preparing a substrate, a step of dissolving and removing two kinds of metal layers having different etching conditions by selective etching, a step of drilling a substrate, a step of plating at least a part of a hole wall of the substrate and a surface of the substrate, The method includes a step of etching and removing unnecessary metal portions on the substrate surface.

The present invention will be described in detail with reference to the embodiment shown in FIG. Selectable etching 2 as metal foil
A metal foil 1 composed of a metal layer (11, 12 in the figure), a copper layer 13, and an anti-corrosion metal layer 14 is prepared. The metal layer 11 that can be selectively etched has a role of a support of the metal foil and a role of having an uneven shape for improving the adhesive strength of the copper foil at the time of lamination, and the lower limit of the thickness is 5 μm or more. , More preferably 10 μm or more. The upper limit of the thickness is 70 μm or less, more preferably 35 μm or less, from an economic viewpoint. The selectively etchable metal layer 12 must serve as a stop layer when the selectively etchable metal layer 11 is etched, and must be capable of being dissolved and removed while leaving the copper layer 13 next. Economically, the smaller the thickness, the better. The minimum value is determined by the presence or absence of a defect such as a pinhole. Desirable thickness is 0.1-5 μm, more preferably 0.3-2 μm. After removing the metal layers 11 and 12 that can be selectively etched, the copper layer 13 has a role of a base for forming a wiring layer thereafter and a role of protecting the base material when drilling a substrate. The thinner the copper layer 13 is, the better the fine wiring is formed, and the thicker the copper layer 13 is. Desirable thicknesses satisfying both are 1 to 10
μm, and more preferably 3 to 5 μm. The corrosion-resistant metal layer 14 is a metal layer in which ions are less likely to move into the base material than copper, and plays a role in improving insulation reliability. As for this thickness, a thickness of 0.1 to 1 μm is sufficient, and a further thickness is unnecessary. The material that can be used for the selectively etchable metal layers 11 and 12 and the corrosion-resistant metal layer 14 is not limited as long as it is a combination of metals that can play the role described above. Combinations of metals that can be formed sequentially by electroplating are particularly suitable. In view of the compatibility of the conventional copper foil manufacturing method and the wiring board manufacturing method, the selectively etchable metal layer 1
Copper and nickel are suitable for 1 and 12 in this order, and nickel is suitable for the corrosion-resistant metal layer 14.

The above-mentioned metal foil 1 and substrate 2 are laminated (FIG. 1, (b)). The substrate 2 is not particularly limited as long as it is a general resin-based material, and particularly, an epoxy resin with a glass cloth and a polyimide resin with a glass cloth are suitable. When forming a multilayer wiring, inner wiring layers that have been processed in advance are laminated together.

Dissolution and removal of the selectively etchable metal layers 11 and 12 of the resulting laminate (FIG. 1)
(C), (d)) and drilling (FIG. 1 (e)). Although FIG. 1 shows an example in which holes are formed after dissolving and removing, holes may be formed first, or holes may be formed after dissolving and removing the selectively etchable metal layer 11.

Thereafter, FIG. 1 shows a method of performing pattern plating. After a pattern is formed with an organic resist 4, a copper plating 5 and a metal etching resist 6 are plated (FIG. 1 (g)). . As the metal-based etching resist, solder, nickel, tin, or gold can be used.

Thereafter, the organic resist 4 is removed, and the copper layer in the unnecessary portions and the corrosion-resistant layer are removed (FIG. 1).
(J)). The metal etching resist may be removed as needed.

FIG. 1 (f) shows a method in which pattern plating is carried out directly below. However, after performing panel plating on the entire substrate including the hole walls, unnecessary portions may be removed by etching. Panel plating and pattern plating may be used in combination.

In order to further improve the electrolytic corrosion resistance, it is preferable to apply nickel plating before the copper plating on the hole wall, and the thickness is required to be 0.1 μm or more, and 1 μm or less. Is enough.

[0012]

In order to form a wiring in a thin wiring, it is necessary to reduce the final etching thickness. In the case of the present invention, the etching thickness is at most 40 μm when the copper layer is 10 μm even when the panel plating including the hole walls is performed at a thickness of 30 μm. In the case of the pattern plating as shown in FIG. The thickness is only the thickness of the copper layer 13 and is 10 μm or less. According to the above-mentioned document, an etching thickness of 45 μm or less is required to form a wiring of 80 μm. However, it is understood that the present invention satisfies this requirement and that fine wiring can be easily formed. In addition, since the metal layer having electric corrosion resistance is provided, migration due to ionization of the metal used in the wiring is less likely to occur even at a fine wiring interval, and a wiring board with high insulation reliability can be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An explanation will be given based on FIG. Copper 30 μm, thickness, and nickel (containing phosphorus) 0.5 μm thickness were formed by electroplating as metal layers 11 and 12 which can be selectively etched. Thereafter, copper was plated as a copper layer 13 to a thickness of 5 μm, and nickel (containing phosphorus) was plated to a thickness of 0.5 μm as an anticorrosion metal layer. In addition, 8 is 1 to 11
A well-known process was performed so that the unevenness of 0 μm and the unevenness of 13 to 1 to 3 μm were formed. This metal foil and epoxy containing glass cloth were laminated and bonded (FIG. 1B). Copper and nickel of 11 of this laminate were dissolved and removed with a known alkaline etchant and Top Lip AZ (nickel stripping solution, manufactured by Okuno Pharmaceutical Co., Ltd., respectively) (FIG. 1 (d)). After drilling this product, Photek, HF4
After pattern formation with 50 (dry film, manufactured by Hitachi Chemical Co., Ltd., trade name) (FIG. 1 (f)), copper plating was
A thickness of 8 μm and solder plating were respectively electroplated to a thickness of 8 μm (FIG. 1 (f)). After peeling off the Photek HF450, unnecessary copper is removed with an alkaline etchant (Fig. 1).
(I)) In the top lip AZ, unnecessary portions of nickel were removed (FIG. 1 (j)). As a result of forming the wiring in this manner, a wiring having a width of 60 μm was formed. In addition, as a result of measuring the peel strength of the copper foil, 1.4 kgf / c was obtained.
m.

[0014]

According to the present invention, for two types of metal layers having different etching conditions, a combination of metal layers can be selected so as to optimize the cost in manufacturing the metal foil and the productivity in removing the etching. In addition, at the time of lamination, the thickness of the metal foil is large, handling is easy, and a laminate with an ultra-thin copper foil can be easily obtained. Also, if formed by electroplating, the production of metal foil becomes easy, and in order to increase the adhesive strength with the resin layer, it is easy to apply the unevenness imparting treatment currently performed in copper foil production. Become. further,
By using a copper layer and a nickel layer, a general copper foil production line can be easily applied, productivity is improved, and compatibility with the production line at the time of wiring processing is good. According to the present invention, the insulation reliability of the wiring board is improved with respect to the metal layer having corrosion resistance. In addition, by using the nickel layer, it is possible to manufacture easily at a relatively low cost, and it is possible to obtain a sufficient anti-corrosion effect. Further, by covering the hole walls with nickel, it is possible to obtain further insulation reliability of the wiring board.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of each step of a method for manufacturing a wiring board according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal foil 11 Metal foil which can be selectively etched 12 Metal layer which can be selectively etched 13 Copper layer 14 Metal layer of electric corrosion resistance 2 Base material 3 Hole 4 Organic plating resist 5 Copper plating 6 Metal etching resist

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Shoji Nakaso 1500 Ogawa, Oji, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Shimodate Research Laboratory (56) References JP-A-1-2511691 (JP, A) JP-A-2-239687 (JP, A) JP-A-1-255295 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 3/00-3/42 H05K 1/09

Claims (5)

(57) [Claims] 1. Two kinds of metal layers having different etching conditions,
A step of forming a substrate by laminating a metal foil composed of four layers of a copper layer and a corrosion-resistant metal layer with a substrate, a step of dissolving and removing two types of metal layers having different etching conditions by selective etching, Forming a hole in a substrate, plating at least a part of a hole wall of the substrate and at least a part of the surface of the substrate, and etching and removing an unnecessary metal portion on the surface of the substrate. 2. A metal layer formed by sequentially electroplating two types of metal layers having different etching conditions, a copper layer, and a corrosion-resistant metal layer. 3. The method for producing a wiring board according to item 1. 3. The wiring according to claim 1, wherein the two types of metal layers having different etching conditions are a copper layer and a nickel layer in order from the surface of the laminated substrate. The method of manufacturing the board. 4. The method for manufacturing a wiring board according to claim 1, wherein said metal layer having electrical corrosion resistance is a nickel layer. 5. The plating method according to claim 1, wherein the plating performed on at least a part of the hole wall of the substrate and the surface of the substrate is a multi-layer plating of nickel plating and copper plating. Manufacturing method of wiring board.