Work holders – With fluid means – Vacuum-type holding means
Reexamination Certificate
2001-06-28
2003-12-02
Wilson, Lee D. (Department: 3723)
Work holders
With fluid means
Vacuum-type holding means
C269S2890MR
Reexamination Certificate
active
06655671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printed-wiring-board holding apparatus and particularly to such an apparatus which applies suction or negative pressure to a printed wiring board (PWB) and thereby holds the PWB. A PWB on which electric components (e.g., electronic components) have been mounted should be called as a printed circuit board (PCB) but, in the present specification, a PCB is also referred to as a PWB, for avoiding complexity.
2. Discussion of Related Art
Generally, a PWB includes a thin substrate formed of an electrically insulating material such as a synthetic resin, and a circuit pattern formed of an electrically conductive material on the thin substrate. Thus, the PWB has flexibility. Therefore, when electric components (ECs) are mounted on the PWB, or when an adhesive or a creamed solder is applied to the PWB for mounting of ECs, the PWB cannot maintain an accurately flat posture, if a back surface of the PWB is not supported at a considerably large number of points.
To solve this problem, Japanese Patent Document No. 7-15189 teaches applying a negative pressure to a PWB and thereby holding the same. More specifically described, the document discloses a PWB holding apparatus including a base plate and a plurality of backup pins. The base plate has a plurality of negative-pressure supply holes each of which opens in an upper surface thereof and is connected via a passage formed therein to a negative-pressure supply source. Each of the backup pins includes an elongate pin portion and a container-like seat portion, and the pin portion has a passage which is formed therethrough in an axial direction thereof and is communicated with an inner space of the seat portion. Each backup pin is attached to the upper surface of the base plate, such that a lower-end surface of the seat portion thereof is held in close contact with a portion of the upper surface that surrounds the opening of a negative-pressure supply hole. In this state, the inner passage of the pin portion of the pin is communicated with the negative-pressure supply hole via the inner space of the seat portion, so that negative pressure is supplied to the inner passage to suck a PWB and thereby support the back or lower surface thereof.
The backup pins support the back surface of the PWB that is opposite to the front surface for which an operation, such as mounting of ECs, is performed. However, the backup pins must not engage uneven portions of the back surface of the PWB itself or the ECs mounted on the back surface. Therefore, the backup pins must be engaged with only limited portions of the back surface of the PWB and, depending upon those limited portions of the back surface, the backup pins must be attached to only limited portions of the upper surface of the base plate. Thus, the backup pins are attached to selected ones of the negative-pressure supply holes of the base plate, and the remaining supply holes to which the backup pins are not attached are covered with respective caps to avoid any leakage of the negative pressure.
However, it is cumbersome to attach the caps to the negative-pressure supply holes free of the backup pins, and accordingly it is time-consuming to attach the backup pins and the caps to the base plate and thereby set the PWB holding apparatus so that the apparatus can apply the negative pressure to a PWB and thereby hold the same.
SUMMARY OF THE INVENTION
The present invention provides a printed-wiring-board holding apparatus that has each feature described below. The following features are described, like claims, in respective paragraphs that are given respective sequential numbers. Any feature that includes another feature shall do so by referring to the number given to the latter feature. However, the following features and the appropriate combinations thereof are just examples to which the technical features, and the combinations thereof, described in the specification are by no means limited. In addition, in the case where one feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed in the one feature. That is, it is possible to select and employ only a portion (one, two, . . . , but not all) of those items.
(1) According to a first feature of the present invention, there is provided an apparatus for holding a printed wiring board, comprising a holding table which has a flat upper surface and a plurality of negative-pressure-supply holes each of which has an opening in the upper surface; at least one holding member which is attachable to the upper surface of the holding table such that a lower end surface of the holding member is held in close contact with a portion of the upper surface that surrounds the opening of at least one of the negative-pressure-supply holes, the holding member having a negative-pressure passage which is formed therethrough to connect between the lower end surface thereof and an upper end surface thereof, the holding member supporting, at the upper end surface thereof, the printed wiring board, and applying a negative pressure supplied from the at least one negative-pressure-supply hole via the negative-pressure passage thereof, to the board and thereby holding the board; and a plurality of opening and closing valves which are associated with the plurality of negative-pressure-supply holes, respectively, each of the opening and closing valves closing a corresponding one of the negative-pressure-supply holes in a state in which the holding member is not attached to the portion of the upper surface of the holding table that surrounds the opening of the corresponding one negative-pressure-supply hole, and opening the corresponding one hole, in a state in which the holding member is attached to the portion of the upper surface, so that the corresponding one hole is communicated with the negative-pressure passage of the holding member.
One holding member may be held in close contact with a portion of the upper surface of the holding table that surrounds the opening of one negative-pressure-supply hole, or the respective openings of two or more negative-pressure-supply holes. One or more holding members are attached to the holding table, at only one or more positions corresponding to one or more negative-pressure-supply holes selected from all the negative-pressure-supply holes of the holding table. The holding member or members attached to the holding table opens or open the opening and closing valve or valves, so that the selected negative-pressure-supply hole or holes is or are communicated with the negative-pressure passage or passages of the holding member or members and the negative pressure (i.e., vacuum or suction) is supplied from the negative-pressure-supply hole or holes to the negative-pressure passage or passages. Since the holding member supports, at its upper-end surface, the lower surface of the printed wiring board (PWB), the PWB does not sag; and since the holding member applies the negative pressure to the PWB and thereby holds the PWB, the PWB does not warp upward. That is, the holding member can hold a desired portion of the PWB such that the PWB does not warp in directions toward, and away from, the holding table. Regarding a negative-pressure-supply hole to which a holding member is not attached, the opening and closing valve associated with the hole remains closed to prevent leakage of the negative pressure. Thus, no plug or cap is needed to close the negative-pressure-supply hole to which no holding member is attached, unlike in a conventional PWB-holding device. That is, the present PWB holding apparatus can be easily set in a short time so that the holding apparatus can hold a desired portion of a PWB at a desired distance from the holding table.
(2) According to a second feature of the present invention that includes the first feature (1), the each opening and closing valve comprises a valve hole which is provided at an end portion of the corresponding one negative-pressure-supply hole on a side of the opening
Fuji Machine Mfg. Co. Ltd.
Wilson Lee D.
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