Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2002-06-27
2004-06-01
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S840000, C029S846000, C174S255000
Reexamination Certificate
active
06742250
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a wiring substrate configured such that a conductor layer of a predetermined pattern is formed on a resin dielectric layer, and an upper resin dielectric layer is formed on the resin dielectric layer and on the conductor layer, and more particularly to a method for manufacturing a wiring substrate configured such that a conductor layer is formed through copper plating on a resin dielectric layer whose surface has been roughened to a predetermined roughness and to which palladium adheres.
2. Description of the Related Art
Conventionally, a wiring substrate has been known configured such that a conductor layer of a predetermined pattern is formed on a surface-roughened resin dielectric layer, and an upper resin dielectric layer is formed on the resin dielectric layer and on the conductor layer.
An example of such a wiring substrate is a wiring substrate
101
, which is schematically shown in the partial, enlarged sectional view of FIG.
6
. The wiring substrate
101
includes a surface-roughened resin dielectric layer
103
. A conductor layer
107
of a predetermined pattern, which includes wiring and pads, is formed on the resin dielectric layer
103
through electroless copper plating and copper electroplating. An upper resin dielectric layer
105
is formed on the resin dielectric layer
103
and on the conductor layer
107
.
The wiring substrate
101
is manufactured, for example, in the following manner. A substrate
111
having the resin dielectric layer
103
is prepared. The surface of the resin dielectric layer
103
is roughened to a predetermined roughness by etching (see
FIG. 7
) for the purpose of enhancing bonding strength between the resin dielectric layer
103
, and the conductor layer
107
or the upper resin dielectric layer
105
, which are to be formed on the resin dielectric layer
103
.
Subsequently, as shown in
FIG. 7
, palladium
113
, which serves as a catalytic metal in the course of formation of an electroless copper plating layer, is formed on the roughened surface of the resin dielectric layer
103
.
Next, the substrate
111
to which palladium
113
adheres is subjected to electroless copper plating, thereby forming an electroless copper plating layer
115
, as represented by the thick line in
FIG. 8
, on substantially the entire surface of the resin dielectric layer
103
.
The substrate
111
on which the electroless copper plating layer
115
has been formed is heated at 120° C. for 60 minutes for the purpose of, for example, drying the wet substrate
111
and enhancing bonding strength between the resin dielectric layer
103
and the electroless copper plating layer
115
.
Subsequently, a plating resist layer
117
is formed in a predetermined pattern on the electroless copper plating layer
115
(see FIG.
8
).
Subsequently, the substrate
111
on which a plating resist layer
117
has been formed is subjected to copper electroplating, thereby forming a copper electroplating layer
119
on the electroless copper plating layer
115
exposed through the plating resist layer
117
as shown in FIG.
8
.
Next, the plating resist layer
117
is removed.
Subsequently, the substrate
111
, from which the plating resist layer
117
has been removed, is heated at 150° C. for 120 minutes to enhance bonding between the resin dielectric layer
103
and the electroless copper plating layer
115
and between the electroless copper plating layer
115
and the copper electroplating layer
119
.
Subsequently, as shown in
FIG. 9
, the electroless copper plating layer
115
is etched away, except where the same is overlaid with the copper electroplating layer
119
, thereby forming the conductor layer
107
in a predetermined pattern. In this case, a metallic residue
121
of the palladium
113
and copper may be present on a portion (hereinafter also called “an exposed portion”) of the resin dielectric layer
103
which is exposed through the conductor layer
107
, such as through spaces between conductor lines.
Then, the substrate
111
is cleaned using a permanganic acid solution, thereby completely removing the metallic residue
121
from the exposed portion of the resin dielectric layer
103
.
Subsequently, the upper resin dielectric layer
105
is formed on the resin dielectric layer
103
and on the conductor layer
107
, thereby completing the wiring substrate
101
shown in FIG.
6
.
3. Problems to be Solved by the Invention
However, permanganic acid treatment for removing the metallic residue
121
is adapted to melt the surface of the resin dielectric layer
103
so as to remove the metallic residue
121
together with resin. Therefore, the treatment roughens the surface of the resin dielectric layer
103
(see FIG.
6
), to thereby impair bonding strength between the resin dielectric layer
103
and the upper resin dielectric layer
105
.
If permanganic acid treatment is not performed, the upper resin dielectric layer
105
is formed while the metallic residue
121
of the palladium
113
and copper is present on the exposed portion of the resin dielectric layer
103
, potentially raising a problem such as a short circuit in the wiring substrate
101
or a reduction in insulation resistance.
The present invention has been accomplished in view of the foregoing, and an object of the present invention is to provide a method for manufacturing a wiring substrate, wherein a conductor layer of a predetermined pattern is formed, through copper plating, on a resin dielectric layer having a roughened surface to which palladium adheres, and an upper resin dielectric layer is formed on the resin dielectric layer and the conductor layer. The method can remove residual substances such as palladium from an exposed portion of the resin dielectric layer, and can establish reliable bonding strength between the resin dielectric layer and the upper resin dielectric layer.
The above object of the present invention has been achieved by providing a method for manufacturing a wiring substrate including a resin dielectric layer, a conductor layer of a predetermined pattern formed on the resin dielectric layer, and an upper resin dielectric layer formed on the resin dielectric layer and on the conductor layer, comprising: a conductor layer forming step of forming the conductor layer, through electroless copper plating and copper electroplating, on the resin dielectric layer of the substrate, the resin dielectric layer having a surface which has been surface-roughened to a predetermined roughness and to which palladium adheres; a cyan treatment step of cleaning the substrate, on which the conductor layer has been formed, using a cyanide-containing solution; and an upper resin dielectric layer forming step of forming an upper resin dielectric layer on the resin dielectric layer and the conductor layer of the cyan-treated substrate.
As mentioned previously, if permanganic acid treatment is used to remove an adhering metallic residue of palladium and copper from a portion (hereinafter also called “an exposed portion”) of the resin dielectric layer which is exposed through the conductor layer, such as through spaces between conductor lines, the resin dielectric layer is also roughened. This results in impaired bonding strength between the resin dielectric layer and the upper resin dielectric layer.
By contrast, the present invention employs a cyan treatment in place of permanganic acid treatment; i.e., the substrate is cleaned using a cyanide-containing solution. Cleaning with a cyanide-containing solution can remove a metallic residue of palladium and copper without roughening the resin dielectric layer, thereby preventing a problem such as a short circuit in the wiring substrate or a reduction in insulation resistance, while establishing reliable bonding strength between the resin dielectric layer and the upper resin dielectric layer.
A cyanide-containing solution is an aqueous solution of an inorganic cyanide compound such as potassium cyanide or sodium cyanide, o
Arbes Carl J.
NGK Spark Plug Co. Ltd.
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