Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1998-07-13
2001-08-14
Valentine, Donald R. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204SDIG007
Reexamination Certificate
active
06274010
ABSTRACT:
This invention relates to an electroplating apparatus and is, in particular, concerned with such an apparatus with improvements in the uniform distribution of metal on substrates to be electroplated, e.g. printed circuit boards.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,879,007 discloses a floating shield for use in an electrolytic bath. The shield includes an elongated trough in which substrates are loaded for plating. The substrates are held in the trough in a vertical plane, and with the lower edges of the substrates below the plane of the upper edges of the trough. Immersed into the bath are a pair of anodes, each extending parallel to the longitudinal axis of the floating shield. The substrates loaded in the trough are connected to a cathode bus bar by one or more clamps. In operation, electric current passes between the anodes and the cathode bus bar through electrolyte contained in the bath, and thereby to electroplate the substrates.
When a plating factory orders an electroplating apparatus from a manufacturer, it is necessary to specify the “board size” of the substrates intended to be plated by the apparatus. In this connection, “board size” means the vertical length of the substrate when such is held in a vertical plane. It is also a usual practice in the relevant field to so arrange the depth of the floating shield in the bath that the top edge of the substrates is of a fixed distance from the top edge of the bath. The manufacturer will then arrange the dimensions of the bath, the anodes and the depth of the trough in the bath such that there will be a satisfactory and uniform electroplating result. It is found in practice that if substrates of a board size shorter than the intended board size are electroplated in the bath, the lower edges of the substrates will be “over-plated”. This is known as “edging effect” and means that the metal deposited on or around the lower edges of the substrates is thicker than that deposited in the rest of the substrates.
While it is possible to reduce this “edging effect” by changing the anodes used in each electroplating task, as there may be over forty anodes in a single tank, and they are very heavy, it is very difficult and not practical to replace anodes.
It is therefore an object of the present invention to provide an improved electroplating apparatus in which the aforesaid shortcoming is mitigated, or at least to provide a useful alternative to the trade.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an apparatus for electroplating at least one substrate, comprising support means, anode means, at least one container and blocking means, wherein said support means supports said substrate and is in an electrically conductive relationship therewith, wherein said container contains said anode means, said support means and an electrolyte, wherein in operation, an electric field exists in said electrolyte between said support means and said anode means, and wherein said blocking means is movable to vary the amount of electric current passing between said support means and said anode means.
Advantageously, said blocking means may be movable by said support means.
Conveniently, said blocking means may be movable to vary the amount of electric current passing between a bottom part of said support means and said anode means.
Suitably, said blocking means may be made substantially of an electrically insulating material.
Said insulating material may advantageously be poly-tetrafluoroethylene.
Said blocking means may conveniently comprise a plurality of sheet members.
Said sheet members may suitably be movable away from each other.
Advantageously, said blocking means may be elastic.
Conveniently, said blocking means may comprise a plurality of substantially rigid blocking members.
Suitably, said apparatus may comprise at least two plates to each of which at least one blocking member is hingedly engaged.
Said blocking members may advantageously be pivotally movable relative to the plate to which it is hingedly engaged.
Said blocking members may conveniently be made substantially of polypropylene.
REFERENCES:
patent: 4879007 (1989-11-01), Wong
patent: 4964964 (1990-10-01), Murphy
patent: 4988426 (1991-01-01), Metzka
patent: 5391276 (1995-02-01), Astor et al.
patent: 5401370 (1995-03-01), Kauper et al.
patent: 5589051 (1996-12-01), Henington
patent: 5744013 (1998-04-01), Botts et al.
patent: 5776327 (1998-07-01), Botts et al.
patent: 3726571 C1 (1989-03-01), None
patent: 4005209 A1 (1991-08-01), None
patent: 0 666 343 A1 (1995-08-01), None
patent: 712505 (1931-10-01), None
Fung Chun Pan
Henington Paul
Lee Chi Chung
Li Kwok Wah
Process Automation International Limited
Taylor Reese
Valentine Donald R.
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