Printing – Stenciling – Processes
Reexamination Certificate
1999-10-08
2001-08-14
Eickholt, Eugene (Department: 2854)
Printing
Stenciling
Processes
C101S114000, C101S123000, C101S127000, C101S169000
Reexamination Certificate
active
06272984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a squeegee for use in screen printing, and a screen printing method, and in particular to the art of performing screen printing on a surface of an object that has at least one projection.
2. Related Art Statement
Screen printing is performed using a screen and a squeegee. A screen having a plurality of print holes is placed on an object such as a printed circuit board, a print material such as a creamed solder or an adhesive is placed on the screen, and a squeegee is moved relative to the screen placed on the object, so that the print material is forced through the print holes of the screen onto one or more print spots on a print surface of the object. In the case where the print surface of the object has one or more projections, the screen may be one which has one or more embossed portions capable of accommodating the one or more projections, respectively, and accordingly does not interfere therewith. In the case where the object is a printed circuit board, the one or more projections of the object may be one or more electric components mounted on the circuit board, or one or more projections needed for easier production of the circuit board. In the case where the object has one or more projections and the screen has one or more embossed portions for accommodating the one or more projections, one or more portions of the squeegee that correspond to the one or more embossed portions of the screen climb over the one or more embossed portions, while the remaining portion or portions of the squeegee continue to contact the screen so as to force the print material through the print holes of the screen onto the object. Thus, the print material is printed on the object.
However, when a climb-over portion of the squeegee climbs over an embossed portion of the screen, a space is created between the screen and each of two adjacent portions of the squeegee on both sides of the climb-over portion of the same. More specifically described, when the climb-over portion of the squeegee climbs over the embossed portion of the screen, distant portions of the squeegee that are sufficiently distant from the climb-over portion in a direction perpendicular to the direction in which the squeegee is moved relative to the screen, and parallel to the plane of the screen, can continue to contact an embossment-free portion of the screen that is free of embossment, but the two adjacent portions of the squeegee that are near to the climb-over portion are separated from the screen by being pulled by the climb-over portion climbing over the embossed portion of the screen. Thus, on both lateral sides of the embossed portion of the screen, respective spaces are created whose dimensions increase in respective directions toward the embossed portion. Therefore, if there is a print spot on a lateral side of, and in vicinity of, a projection of the object to be printed, the print material may not be printed on the print spot of the object.
SUMMARY OF THE INVENTION
The present invention provides a squeegee for use in screen printing and a screen printing method that have one or more of the technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (11). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to that technical feature. Thus, two or more of the following technical features may be combined, if appropriate. Each technical feature may be accompanied by a supplemental explanation, as needed. However, the following technical features and the combinations thereof are just examples to which the present invention is by no means limited.
(1) According to a first feature of the present invention, there is provided a squeegee for use in screen printing, comprising a flexible portion; and one separation or two separations extending from a contact edge of the flexible portion for contact with a screen, toward a base portion of the squeegee, thereby at least partly separating the flexible portion, so that the flexible portion includes a first portion between the one separation and a lateral edge of the flexible portion, or between the two separations, and a second portion different from the first portion, and so that the first portion and the second portion are flexible independent of each other. The one separation or each of the two separations may, or may not, extend in a direction perpendicular to the contact edge of the flexible portion that extends in a direction parallel to the plane of the screen. In the case where the flexible portion has just one separation, the one separation may be so inclined that the distance between the one separation and one lateral edge of the flexible portion increases or decreases in a direction from the contact edge toward the base portion of the squeegee. In the case where the flexible portion has two or more separations, a pair of separations out of those separations may be so inclined that the distance between the pair of separations increases or decreases in the same direction. When at least one of the squeegee and the screen is moved relative to the other for printing the print material on an object, both the first and second portions of the flexible portion are moved on the screen, as a unit, i.e., without being separated from each other, over a portion of the screen that is free of embossment in the widthwise direction of the screen that is parallel to the direction in which the squeegee extends. Thus, the print material is forced through the print hole or holes of the screen onto the object. When the squeegee reaches an embossed portion of the screen, the first portion of the flexible portion that corresponds to the embossed portion is flexed by the embossed portion, independent of the second portion, so that only the first portion climbs over the embossed portion. Since the second portion is at least partly isolated from the first portion by the one or two separations, the second portion is not flexed with the first portion but remains in contact with a portion of the screen that is free of embossment. The one or two separations at least partly separates the flexible portion into the first and second portions. The present squeegee is free from the conventionally experienced problem that when a squeegee climbs over an embossed portion of a screen, two spaces are created, between the squeegee and the screen, on both lateral sides of the embossed portion in the widthwise direction of the screen, in such a way that respective dimensions of the two spaces increase in respective directions toward the embossed portion. That is, even if the screen may have a print hole in the vicinity of the embossed portion, the second portion of the flexible portion can force the print material into the print hole of the screen and thereby apply the print material to the object. Generally, the flexible portion is formed of a soft material such as rubber or the like. However, the flexible portion may be formed of a hard material such as hard synthetic resin or metal, if the flexible portion is so formed as to have such a thickness which assures that the flexible portion is flexed with such a force which does not damage the screen.
(2) According to a second feature of the present invention that includes the first feature (1), the one separation or each of the two separations has a length not smaller than one second of a dimension of the flexible portion in a direction in which the one separation or the each of the two separations extends. It is common that the base portion of the squeegee is held by a squeegee holder in such a way that the base portion cannot be flexed, e.g., cannot be elastically deformed. In this case, only a projecting portion of the squeegee that projects from the squeegee holder provides the flexible portion. The one separation or each of the two separations may have a length greater or shorter than the dimension of the flexible portion. M
Kato Seizi
Tsuta Hiroshi
Eickholt Eugene
Fuji Machine Mfg. Co. Ltd.
Oliff & Berridg,e PLC
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