Printing – Antismut device – Cleaners
Reexamination Certificate
1999-10-15
2001-05-22
Yan, Ren (Department: 2854)
Printing
Antismut device
Cleaners
C101S425000, C134S093000, C134S199000
Reexamination Certificate
active
06234080
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to printing of viscous materials onto a surface through a screen having a plurality of openings therein, and more particularly to method and apparatus for cleaning paste residues from screens used in producing surface mount technology circuit boards suitable for use in high technology products.
2. Description of the Prior Art
Screens used in producing such circuit boards require frequent cleaning because viscous printing material, including solder paste, is caused to remain not only on screen surfaces, but also in openings in the screen during repeated printing. If the printing is further continued, the remaining solder paste as paste residue will cause defective printing such as blot, blur, discontinuity of line, or the like, of a paste pattern printed on the circuit board. On the other hand, to meet the rapid development of the electronics industry, a screen is required to obtain high resolution. That is, the area of opening pattern on the screen and the space between adjacent openings in the screen tend to be reduced. Such a tendency makes it difficult to effectively remove solder paste residues from the screen, particularly the residues that adhere to inner peripheral surfaces of small or reduced openings in the screen.
There are various methods and apparatuses by which solder paste residues that are adhered to the screen can be removed. One approach is to wipe off the residues by applying paper to the screen surfaces. Another approach is to scrape off the residues by scraper means. However, it is impossible for these approaches to remove the residues in the openings in the screen. Another approach is to use an airstream. In this approach, the residues in the openings can be relatively easily removed when the residues are soft. In this approach, however, when the residues adhered to the surfaces of the openings in the screen are solidified or dried, or when the residue is clogged in a small-sized opening in the screen, it is extremely difficult to clean them from the screen.
To overcome drawbacks or disadvantages indicated by these approaches, methods and apparatuses for cleaning screens by using a water-based solvent as a wash liquid have recently been proposed. With this type of method for cleaning a screen, most of the above-mentioned drawbacks or disadvantages can be eliminated. However, the use of a cleaning solvent causes environmental and personal injury resulting from solvent release into the atmosphere, and worker exposure to solvent vapors. Furthermore, solder paste residue contains lead that is removed from the screen during cleaning, and worker exposure to lead is a health concern which must be seriously addressed.
A known apparatus of this type is schematically shown as PRIOR ART
1
in FIG.
11
. As shown therein, the known apparatus is provided with a cleaning reservoir
103
with its upper end opened and has therein two inwardly directed mutually opposed spray nozzles
131
for spraying cleaning solvent against both surfaces of the screen
105
which is vertically held between the nozzles
131
during cleaning. Numeral
132
shown in
FIG. 11
indicates drier nozzles. Another known apparatus of the type mentioned above is also schematically shown as PRIOR ART
2
in FIG.
12
. As shown therein, the apparatus is provided with a box-like housing
200
having an opening at its upper wall through which a screen
205
is vertically inserted into the housing
200
for cleaning. In the housing
200
there are provided two spray nozzles
201
,
202
for spraying the solvent against both surfaces of the screen
205
, which is vertically held between the nozzles
201
,
202
during cleaning. The upper opening of the housing may be closed and opened and is closed in the manner shown in
FIG. 12
during cleaning. Numerals
203
,
204
show drier nozzles for drying the screen
205
after spraying is finished.
A common feature of these known apparatuses is that the screen is held in an erect position during cleaning. Other common features are that the apparatus is installed outside a screen printing machine, that the apparatus becomes bulky as a whole, due to its abovementioned structures, and cannot be incorporated into a screen printing machine, and, accordingly, that it cannot be used for cleaning of the screen during paste printing cycles performed by the machine.
SUMMARY OF THE INVENTION
The present invention is intended to eliminate the drawbacks or disadvantages indicated with the known methods and apparatuses as described above and to provide improved method and apparatus for cleaning the screen used in a screen printing machine.
It is, therefore, one object of the present invention to provide a method and an apparatus for cleaning a screen used in a screen printing machine, which are capable of preventing environmental injury resulting from cleaning solvent release into the atmosphere, and, of protecting workers from being exposed to detrimental substances within solder paste residue, such as lead.
Another object of the invention is to provide a method and an apparatus of the kind described above, which are capable of efficiently removing the paste residue from the screen.
A further object of the invention is to provide an apparatus of the kind stated above which is capable of being incorporated into a screen printing machine, and which permits automated cleaning of the screen during screen printing cycles performed by the machine.
It is another object of the invention to provide an apparatus of the kind described above which includes two easily replaceable cleaning chamber units, which can be replaced with other different sizes of cleaning chamber units, depending on the size of the screen used for screen printing.
It is a further object of the invention to provide an apparatus of the kind stated above which includes a cleaning chamber in which a rotatable mechanical means for creating a turbulence, as well as rotational motion in the wash liquid injected into the chamber, so that cleaning effect as well as cleaning efficiency can be accelerated.
It is another object of the invention to provide an apparatus of the kind stated above which includes a cleaning chamber in which a vibrator means for imparting vibratory movement to the screen that is immersed in the wash liquid that is injected into the chamber so that cleaning effect as well as cleaning efficiency can be accelerated.
It is a further object of the invention to provide an apparatus of the kind stated above which includes a cleaning chamber in which a pneumatic means for creating a turbulence, as well as fluctuation, in the wash liquid that is injected into the chamber, so that cleaning effect as well as cleaning efficiency can be enhanced.
REFERENCES:
patent: 5860361 (1999-01-01), Nanjyo et al.
patent: 5976269 (1999-11-01), Hamasaki et al.
patent: 55-002041 (1980-01-01), None
patent: 58-132562 (1983-08-01), None
patent: 07314653 (1995-12-01), None
patent: 08039786 (1996-02-01), None
Collen Law Associates P.C.
McDermott Robert M.
Tani Denkikogyo Co. Ltd
Yan Ren
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