Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2000-08-14
2003-07-08
Barlow, John (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
Reexamination Certificate
active
06591219
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a method of mounting an electric component on a printed-wiring board and particularly to the art of correcting, according to a dimensional error and/or a positional error of the printed-wiring board, a mounting position where the electric component is to be mounted.
2. Related Art Statement
A plurality of ideal mounting positions where respective electric components (“ECs”) are to be mounted on an ideal printed-wiring board (“PWB”) having no dimensional errors or no positional errors, are determined in advance and are pre-stored in a memory. However, before ECs are mounted on an actual PWB, the actual PWB may have at least one dimensional error and/or at least one positional error, for example, because the PWB is produced with at least one erroneous dimension, because the PWB is deformed due to heat or external force applied thereto, and/or because the PWB is erroneously positioned relative to an EC mounting device which is for mounting the ECs on the PWB. In this case, the ideal mounting positions should be modified. The actual PWB has an electrically conductive pattern (e.g., land or pad) at a mounting position where each EC is to be mounted. If the actual PWB has a dimensional error and/or a positional error, the conductive pattern thereof should also have a positional error. If each of the ideal mounting positions is not modified or corrected according to the positional error and/or positional error of the PWB, the electrodes of each EC may not correctly placed on the conductive pattern of the PWB. Japanese Patent Publication No. 8-236997 discloses a method of correcting an ideal EC-mount position according to a dimensional error of a PWB. This conventional method includes (a) calculating a first reference straight line which passes through an ideal EC-mount position and divides, in a first division ratio, each of a first pair of opposed sides of an ideal quadrilateral defined by respective ideal position of four reference points, and a second reference straight line which passes through the ideal EC-mount position and divides, in a second division ratio, each of a second pair of opposed sides of the quadrilateral, and (b) determining, based on the first and second division ratios for dividing the four sides of the ideal quadrilateral, and respective detected actual positions of the four reference points on an actual PWB, an actual EC-mount position where an EC is to be mounted on the actual PWB. Thus, the electrodes of the EC are correctly placed on a conductive pattern of the PWB.
However, the calculations needed for determining the two reference straight lines which divide, in the first and second division ratios, the four sides of the ideal quadrilateral are very complex, which leads to increasing a time needed for processing all the ideal EC-mount positions predetermined for each PWB.
SUMMARY OF INVENTION
The present invention provides an actual-mounting-position determining method, an electric-component mounting apparatus, an actual-mounting-position determining apparatus, and a mounting-position-correcting-program recording medium which have one or more of the following technical features that are described in below in respective paragraphs given parenthesized sequential numbers (1) to (9). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter 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 appropriate combinations thereof are just examples to which the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. 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 a method of determining, according to at least one of at least one dimensional error and at least one positional error of an actual printed-wiring board, an actual mounting position where an actual electric component is to be mounted on the actual board, on a two-dimensional coordinate system defined by a first axis and a second axis, the method comprising the steps of obtaining an ideal relative position of an ideal mounting position which corresponds to the actual mounting position and where an ideal electric component which corresponds to the actual electric component is to be mounted on an ideal printed-wiring board which corresponds to the actual printed-wiring board and which has no dimensional error and no positional error, the ideal relative position being defined as a position of the ideal mounting position relative to four ideal reference-point positions as respective ideal positions of four ideal reference points predetermined on the ideal printed-wiring board, and being defined by four division ratios in which four ideal sides of an ideal quadrilateral defined by the four ideal reference-point positions are respectively divided by two first ideal division points where a first ideal reference line which is parallel to the first axis of the two-dimensional coordinate system and passes through the ideal mounting position intersects a first pair of opposed ideal sides of the four ideal sides of the ideal quadrilateral, and two second ideal division points where a second ideal reference line which is parallel to the second axis of the coordinate system and passes through the ideal mounting position intersects a second pair of opposed ideal sides of the four ideal sides of the ideal quadrilateral, detecting four actual reference-point positions as respective actual positions of four actual reference points which correspond to the four ideal reference points, respectively, and which are predetermined on the actual printed-wiring board on which the actual electric component is to be mounted, calculating, based on the four division ratios and the four actual reference-point positions, four actual division-point positions as respective actual positions of four actual division points which respectively divide, in the four division ratios, four actual sides of an actual quadrilateral defined by the four actual reference-point positions, and calculating, as the actual mounting position, a position of an intersecting point where a first actual reference line which passes through two first actual division points of the four actual division points that correspond to the two first ideal division points, intersects a second actual reference line which passes through two second actual division points of the four actual division points that correspond to the two second ideal division points.
In the present method, the two ideal reference lines are employed which are independent of the four ideal reference-point positions, and the four division ratios in which the four sides of the ideal quadrilateral defined by the four ideal reference-point positions are divided by the four intersecting or division points where the two ideal reference lines intersect the four sides of the ideal quadrilateral, are determined. Those calculations are much simpler than those of the above-explained conventional method. In addition, since the two ideal reference lines are parallel to the first and second axes of the coordinate system, at least one of the x and y coordinates of each of the four intersecting points of the two ideal reference lines and the four sides is equal to a corresponding one of the x and y coordinates of the ideal mounting position. Because of this, the other of the x and y coordinates of the each of the four intersecting points can be easily determined. Each of the four ideal or actual division ratios may be an “inside” or “outside” division ratio. For example, irrespective of whe
Fuji Machine Mfg. Co. Ltd.
Lau Tung
Oliff & Berridg,e PLC
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