Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Treating substrate prior to coating
Reexamination Certificate
1998-04-17
2001-07-17
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Treating substrate prior to coating
C205S137000, C205S148000, C205S920000, C427S096400, C427S304000, C427S346000
Reexamination Certificate
active
06261435
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel plating method which is suitably used to plate a plating target having a micropore, and a novel continuous plating method which uses means for vibrating the plating target at 10 to 60 Hz in addition to vibrational stirring means for a plating bath, aeration and swinging means for swinging the plating target which have been hitherto known. The plating method of the present invention is applicable to any method of an electroplating method, an electroless plating method and a method of using the electroplating method and the electroless plating method in combination.
2. Description of the Related Art
A printed wiring board is used as a board on which various kinds of elements are mounted to mutually wire these elements to one another in all electric equipment from radios, televisions to computers. In such a surface mount type of printed wiring board that parts are attached onto the surface of a board to be connected to one another, a multi-pin structure and a narrow-pitch design have recently propagated, and this technique has been improved more and more in such a situation that a 60-pin/1.0 mm pitch design has been developed and improved through 400-pin/0.3 mm pitch level to 400-pin/0.25 mm-0.3 mm pitch level, and further higher level.
Such an improvement of this technique has promoted a requirement for compact-size and high performance. Accordingly, the diameter of minute through holes required for the wiring between different layers on a laminate type printed wiring board and the diameter of minute holes having a dead end structure (i.e., blind holes) have been increasingly reduced, and at present the diameter is reduced from 0.2 mm or less to 0.05 mm or less, further to 0.03 mm or less.
Air, dust or treatment liquid which is trapped in these microstructured holes cannot be easily removed from the holes, and thus the following disadvantages occur. A first disadvantage resides in that portions at which air or dust exists are hardly plated, so that a conduction failure occurs. A second disadvantage resides in that entrance of plating liquid into a hole is insufficient, and thus the thickness of a plating film outside the hole is different from that inside the hole. A third disadvantage resides in that a non-plated portion occurs in a hole, so that a resistance value is increased even when conduction is established.
On the other hand, a technique disclosed in Japanese Patent Application Publication No. Hei-6-71544 which was previously developed by the inventor of this application contains a technique for vibrating a vibration plate at a vibrational amplitude of 8 to 20 mm and at a vibration frequency of 200 to 600 times per minute in a plating bath to stir the plating bath, thereby performing a plating treatment. Particularly it is proposed that aeration and swing means for a target to be treated are used in combination. The inventor of this application has considered that occurrence of plating-failure portions in the conventional plating method could be avoided if the technique disclosed in the Japanese Patent Application Publication No. Hei-6-71544 is applied to plating of minute holes (micropores) of an article having the minute holes, and has made various attempts. As a result, it has been found out that the fraction defective is surely reduced, however, it does not reach a satisfactory value.
Further, Japanese Patent Application Laid-open No. Sho-62-32690 proposes a method of plating a plating target while swinging and vibrating the plating target. It is merely disclosed that the vibration is generated by supplying air to a vibrator, however, the details such as the type of the vibration, etc. are unclear.
The inventor of this application has repetitively made tests under various combinations and conditions while varying the vibrational stirring condition of the plating bath, the aeration condition and the swinging condition of the plating target, however, satisfactory results cannot be obtained. As final means, the inventor has tried to apply to a plating target such vibrating means that is used to vibrationally stir the solution. As a result, the inventor has found out that the fraction defective can be unexpectedly remarkably reduced, and implemented the present invention.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a plating method and a plating apparatus for surely and uniformly plating minute holes having a diameter of 0.2 mm or less, preferably a diameter less than 0.1 mm, more preferably a diameter of 0.05 mm or less, and still more preferably a diameter of 0.03 mm or less which are indispensable for minute wiring of a printed wiring board, an IC board, etc., thereby reducing the incidence of defective products due to incompleteness of wiring to zero as much as possible.
In order to attain the above object, there is provided a plating method for successively treating a plating target from a pre-treatment step for plating until a plating treatment, characterized in that all the following steps (a) to (d) are simultaneously carried out in a cleaning tank and at least one of an electroless plating tank and an electroplating tank used in the pre-treatment step and the plating step:
(a) a step of vibrationally stirring a treatment bath,
(b) a step of performing an aeration in the treatment bath,
(c) a step of swinging the plating target, and
(d) a step of applying vibration to the plating target.
In the plating method as described above, the treatment bath is vibrationally stirred by vibrating a vibration vane at an amplitude (width of vibration) range from 0.5 to 3.0 mm and at a vibrational frequency of 200 to 800 times per minute; the aeration is performed by using air bubbles generated by a diffuser pipe having a pore opening of 200 to 400 &mgr;m; the plating target is swung at an amplitude (width of swing) of 10 to 100 mm and at a swing frequency of 10 to 30 times per minute; and, the plating target is vibrated at an amplitude of 0.5 to 1.0 mm and at a vibrational frequency of 100 to 300 times per minute.
In order to attain the above object, there is also provided a plating method for successively treating a plating target from a pre-treatment step until a plating treatment, characterized in that (A) a vibrationally stirring apparatus for a treatment bath, (B) an aeration apparatus for the treatment bath, (C) an apparatus for swinging an electrode bar on which the plating target is suspended, and (D) an apparatus for applying vibration to the plating target through the electrode bar in the amplitude range from 0.5 to 1.0 mm by using a vibration motor whose frequency is adjusted to 10 to 60 Hz by an inverter, are operated in a cleaning tank and at least one of an electroless plating tank and/or an electroplating tank used in the pre-treatment step for plating and the plating step.
In the plating method as described above, the vibrationally stirring apparatus for the treatment bath preferably includes vibration generating means containing a vibration motor, vibrationally stirring means for vibrating at an amplitude of 0.5 to 3.0 mm and at a vibrational frequency of 200 to 800 times per minute a vibration vane which is fixed in one stage or in multistage to a vibrating bar which interlocks with the vibration generating means to vibrate in a treatment tank, an inverter for controlling the vibration motor to generate any low-frequency vibration at any frequency in the range from 10 to 500 Hz, preferably from 30 to 60 Hz, and more preferably from 30 to 40 Hz, and vibration stress dispersing means at a connection portion of the vibration generating means and the vibrationally stirring means.
The aeration apparatus for the treatment bath is not limited to a specific one, however, it may be provided with an air diffusing pipe which is designed in such a manner that an area containing the plating target can be sufficiently stirred with air bubbles.
For example, in the case of a diffusing pipe which is obtained by forming many holes each having a pore siz
Nihon Techno Kabushiki Kaisha
Pitney Hardin Kipp & Szuch LLP
Wong Edna
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