Coating processes – With post-treatment of coating or coating material – Cooling
Reexamination Certificate
2001-06-18
2002-12-17
Barr, Michael (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Cooling
C427S353000, C427S430100, C427S438000, C427S443100
Reexamination Certificate
active
06495211
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a substrate including a plating layer and to a plating apparatus for forming a plating layer of a substrate; and, more particularly, to a process for producing a substrate including a base-metal plating layer and to a plating apparatus for forming a base-metal plating layer.
2. Description of the Related Art
Conventionally, a substrate including a layer plated with a base metal such as Ni has been known. For example, in a wiring substrate on which an IC chip is to be provided, usually, an Ni-plating layer (base-metal plating layer) is formed on a connection terminal formed from Cu, and an Au-plating layer is formed on the Ni-plating layer in order to prevent oxidation of the Ni-plating layer.
Such a plating layer of a wiring substrate is formed as follows. A wiring substrate on which an Ni-plating layer is to be formed is subjected to Pd activation treatment before plating, and then the wiring substrate is washed with water.
After washing with water, the wiring substrate is immersed for a predetermined period of time in an Ni-plating solution contained in an Ni-plating tank, to thereby form on a connection terminal of the wiring substrate an Ni-plating layer of predetermined thickness.
Specifically, as shown in
FIG. 6
, after being washed with water, wiring substrates
101
are transferred horizontally to a position above an Ni-plating tank
111
by means of a transfer mechanism
103
. The transfer mechanism
103
includes a rack
105
for holding a number of the wiring substrates
101
, a vertical transfer mechanism
107
for transferring the rack
105
vertically, and a horizontal transfer mechanism
109
for transferring the rack
105
horizontally.
Subsequently, from the position above the Ni-plating tank
111
, the rack
105
is moved downward by means of the vertical transfer mechanism
107
, and the rack
105
(along with the wiring substrates
101
) is immersed for a predetermined period of time in an Ni-plating solution contained in the Ni-plating tank
111
.
After a n Ni-plating layer is formed on each of the wiring substrates
101
, the rack
105
is removed from the Ni-plating tank
111
by means of the vertical transfer mechanism
107
. Subsequently, the rack
105
is transferred, by means of the horizontal transfer mechanism
109
, to a position above a washing tank
113
containing washing water.
Thereafter, the rack
105
is moved downward by means of the vertical transfer mechanism
107
, and the rack
105
is immersed f or a predetermined period of time in the water contained in the washing tank
113
, to thereby wash the wiring substrates
101
.
After the substrates are washed, the rack
105
is removed from the washing tank, and transferred to a position above an Au-plating tank (not illustrated) containing an Au-plating solution. Subsequently, the rack
105
is immersed for a predetermined period of time in the Au-plating solution contained in the Au-plating tank, to thereby form an Au-plating layer on the Ni-plating layer formed on each of the wiring substrates
101
.
Thereafter, the rack
105
is removed from the Au-plating tank, transferred to the subsequent washing tank (not illustrated) containing washing water, and immersed in the water contained in the washing tank, to thereby wash the wiring substrates
101
. Subsequently, the wiring substrates
101
are dried. Thus, the Ni-plating layer and Au-plating layer are formed on a connection terminal of each of the wiring substrates
101
.
3. Problems to be Solved by the Invention
However, in the aforementioned production process, a certain time elapses from the time the rack
105
(along with the wiring substrates
101
) is removed from the Ni-plating tank
111
until the rack
105
is immersed in the water contained in the washing tank
113
. In addition, when the Ni-plating layer is formed, the wiring substrates
101
are heated, since the Ni-plating solution contained in the Ni-plating tank
111
is heated at about 70-90° C. Therefore, during transfer of the wiring substrate
101
, the Ni-plating layer formed on the wiring substrate
101
is exposed to air, while the temperature of the layer is maintained at a high level.
Consequently, during transfer of the wiring substrate
101
, the Ni-plating solution which remains on the substrate may oxidize, leading to problems such as blackening of the surface of the Ni-plating layer and formation of a thin oxidation film. In such cases, when solder bumps are formed on the connection terminal of the wiring substrate
101
on which the Ni-plating layer has been formed, the bonding strength between the Ni-plating layer and the solder may be lowered, thereby lowering the bonding reliability.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a process for producing a substrate which prevents oxidation of residual Ni-plating solution and accompanying problems, including discoloration of a base-metal plating layer and lowering of bonding strength; and a plating apparatus therefor.
The present invention achieves the above object by providing a process for producing a substrate including a base-metal plating layer, which process comprises an immersion step for immersing a substrate in a plating solution contained in a plating tank, to thereby form a base-metal plating layer on a substrate; a washing step which comprises removing the substrate from the plating tank, transferring the substrate to a washing tank, and washing the substrate; and a cooling step which comprises applying cooling liquid to the substrate during at least a portion of the period during which the substrate is being transferred to the washing tank after completing the immersion step, to thereby cool the substrate.
According to the present invention, while the substrate which has undergone the immersion step is removed from the plating tank and is being transferred to a position where the washing step is carried out, cooling liquid is applied to the substrate, to thereby cool the substrate. When cooling liquid is applied during the substrate transfer step, the period of time during which the heated substrate (as heated in the plating tank) is exposed to air is shortened.
Consequently, during transfer of the substrate, plating solution which remains on the substrate is less likely to oxidize, thereby making the substrate less prone to accompanying problems, including blackening of the surface of the plating layer and formation of a thin oxidation film. Therefore, when solder bumps are formed on the plating layer, the bonding strength between the plating layer and the solder is not lowered, and bonding reliability can be enhanced.
The cooling liquid is not particularly limited, so long as the solution can cool the substrate. For example, the cooling liquid may be water, pure water, a plating solution, or a washing solution. The temperature of the cooling liquid is not particularly limited, so long as the cooling liquid can cool the substrate to a temperature so as to suppress reaction of the plating solution which remains on the substrate. The temperature of the cooling liquid may be ambient temperature. The cooling liquid itself may be cooled. Alternatively, the cooling liquid may be heated to some extent, so long as the temperature of the cooling liquid is lower than that of the plating solution contained in the plating tank.
The cooling step may be carried out continuously over the entire substrate-transfer period during which the substrate is transferred from the plating tank to the subsequent washing tank, or during a portion of the transfer period.
In the cooling step of the aforementioned process for producing a substrate, preferably, the cooling liquid is applied to the substrate while the substrate is being removed from the plating tank, to thereby cool the substrate.
In this case, the substrate is cooled simultaneously with removal from the plating tank, thereby minimizing the time during which the plating layer of the heated subst
Doi Yasuo
Hashimoto Hiroyuki
Iba Masahiro
Sato Kazuhisa
Wakako Hisashi
Barr Michael
NGK Spark Plug Co. Ltd.
Sughrue & Mion, PLLC
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