Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2001-08-31
2003-04-29
Lam, Cathy (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C174S261000, C174S265000, C205S183000, C205S184000, C430S016000
Reexamination Certificate
active
06555209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multilayer wiring board having two or more wiring layers and a manufacturing method thereof. More specifically, this invention relates to the multilayer wiring board and the manufacturing method thereof having the step of forming an upper wiring layer, a part thereof being electrically connected with a pillar-like metallic body, after the pillar-like metallic body is formed on a lower wiring layer.
2. Description of the Related Art
In recent years, as electronic equipiments and the like are miniaturized and light-weighted, electronic parts are miniaturized and wiring boards onto which the electronic parts are mounted are required to be higher density, In order to heighten the density of the wiring boards, a method of heightening line density of wiring layers or a method of obtaining a multilayer structure by laminating a plurality of wiring layers are adopted.
The method of manufacturing a multilayer wiring board includes a joining method of forming wiring layers respectively on a plurality of substrates and joining the substrates in a state that insulating sheets intervene between the substrates, and a build-up method of forming insulating layers on a substrate on which a wiring pattern is formed and forming the wiring pattern on the insulating layer, namely, of forming a laminated structure by repeating formation of the insulating layers and wiring patterns. However, since the latter build-up method is advantageous to the heightening of the density of the wiring boards, this method is becoming the mainstream.
Meanwhile, in the multilayer wiring board, conductive connection between the wiring layers should be carried out according to a circuit design. Such conductive connection have adopted an conductive connecting structure that au opening portion of an insulating layer which is called as a via hole is plated cylindrically. However, as for the via hole, when the opening portion is formed and plated, there arises problems that fine processing is difficult and air becomes contaminant. For this reason, in the case where reliability of the wiring board is maintained, the size of the via hole is limited. Moreover, when multilayer are laminated, it is difficult to form a via hole just above a via hole, and the design of the laminated structure is restricted. For this reason, the heightening of the density of the multilayer wiring boards is limited.
On the contrary, in the method of the wiring layers are electrically connected by a pillar-like solid conductor, there does not arise such a problem. For this reason, this method can further heighten the density of the multilayer wiring boards in comparison with the case where a via hole is formed Therefore, it is estimated in this field that the conductive connection between the wiring layers by means of the pillar-like conductor will become the mainstream in the future, and a lot of methods of forming pillar-like conductors are suggested.
For example, Japanese Patent Application Laid-Open No. 9-23065 discloses a method of forming an opening portion on an insulating layer provided on a lower wiring layer by means of laser processing or the like and carrying out electroless plating on the opening portion and filling a pillar-like conductor into the opening portion. Moreover, Japanese Patent Application Laid-Open No. 6-314878 discloses a method of wholly conducting a lower wiring layer and forming a resist pattern having an opening portion and depositing metal on a concave section of the resist pattern by means of electrolytic plating to form the pillar-like conductor.
However, both the above methods have a problem that a height of the pillar-like conductor is easily non-uniform. The former method has a problem that it takes a long time to form the pillar-like conductor because the electroless plating is carried out. The latter method has a problem that current density cannot be heightened and similarly the formation of the pillar-like conductor takes a long time because the electrolytic plating is carried out. Further, the formation of a resist pattern requires a large-scale apparatus for emitting a laser, and thus these methods are disadvantageous from the viewpoint of costs. Further, since it is difficult to securely remove a resist on a bottom portion of the opening portion, reliability of conducting of the pillar-like conductor is lowered.
Therefore, it is an object of the present invention to provide a multilayer wiring board and a manufacturing method thereof which are capable of manufacturing a multilayer wiring board with a combination of simple facility and conventional process and thinning lines of the wiring layer and which have high reliability of the wiring board.
SUMMARY OF THE INVENTION
The above object can be achieved by the following invention. Namely, a multilayer wiring board manufacturing method of the present invention having the step of forming a pillar-like metallic body on a lower wiring layer, and then forming an upper wiring layer, a part thereof being electrically connected with the pillar-like metallic body, is characterized in that the pillar-like metallic body forming step includes: the step of forming a plating layer of metal constituting the pillar-like metallic body; the step of forming a mask layer on a surface portion of the plating layer where the pillar-like metallic body is formed; and the step of etching the plating layer.
According to the manufacturing method of the present invention, since the plating layer is formed not in the opening but on the whole surface and the pillar-like metallic body is formed by etching, laser emission or the like is not particularly required, and a diameter of the pillar-like metallic body can be reduced. Further, since the opening section from which the resist is removed is not plated, the reliability of conductivity between the lower wiring layer and the pillar-like metallic body is heightened. As a result, manufacturing can be carried out by simple facility and combination of conventional steps, and the multilayer wiring board, wherein the wiring layer can be thinned and the reliability of the wiring board is high, can be manufactured.
The manufacturing method of the present invention includes the following first through fourth embodiments.
In the first embodiment, the pillar-like metallic body forming step includes the steps of:
(1a) coating an approximately whole surface of said lower wiring layer including a non-patterned portion with another metal showing resistance at the time of etching the metal constituting said pillar-like metallic body to form a protective metallic layer,
(1b) forming a plating layer of the metal constituting said pillar-like metallic body on an approximately whole surface of said protective metallic layer by means of electrolytic plating;
(1c) forming a mask layer on a surface portion of said plating layer where said pillar-like metallic body is formed;
(1d) etching said plating layer; and
(1e) etching under condition wherein at least said protective metallic layer can be corroded to remove at least said protective metallic layer covering the non-patterned portion
According to the manufacturing method of the first embodiment, since the protective metallic layer is provided, the lower wiring layer is not corroded at the time of etching the plating layer, and the desired pillar-like metallic body can be formed in the position where the mask layer is formed. Further, after the step (1d), the protective metallic layer remaining on the non-patterned portion can be removed securely by the step (1e), and the protective metallic layer under the pillar-like metallic body is hardly corroded at the step (1e). For this reason, short circuit between pattern portions hardly occurs, the reliability of the wiring board is heightened, and thinning is possible. Further, since the protective metallic layer is formed on the whole surface, the plating layer can be formed by electrolytic plating. Moreover, since the plating layer is formed in the hole but on the whole su
Higuchi Toshiro
Yoshimura Eiji
Daiwa Co., Ltd.
Knobbe Martens Olson & Bear LLP
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