Maintenance (Micron) workbook Iss07.pdf - 第15页
Issue 6, Nov 14 15 NOTES:
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Objective MO4 Setup synthetic fiducials
Standard synthetic fiducial shapes should be used whenever available. These must align
to corresponding fiducials on the underside of the stencil.
Failure to set up the fiducials correctly could result in print offsets or vision error messages.
Fiducial Location
It is good practice to choose fiducials that are diametrically opposite and as close to the
outer edges as possible. The following diagram is for a machine set to left fiducial
reference:
(0, 0)
Fiducial #1 X
Fiducial #2 X
Fiducial #1 Y
Fiducial #2 Y
Fiducial #1 X
(0, 0)
Fiducial #1 X
Fiducial #2 X
Fiducial #1 Y
Fiducial #2 Y
Fiducial #1 X
Note that Fiducial #1 should be on the right side of the board, to optimise the trajectory of
the camera as it passes from the board stop position to the first fiducial location.
It is possible to program three pairs of fiducials but this is rarely necessary. It may help if
the board is very large, or has many panels and is showing alignment problems.
Using the on-board tutorials as a guide setup two sets of fiducials.
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Issue 6, Nov 14
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16 Issue 6, Nov 14
Objective MO5 Setup Video models
The video model option is useful when there are no synthetic fiducials on the board or
stencil, or when the fiducials are very poor quality. The secret of success is to pick an area
of the image that is unique within the field of view, as shown below.
The image below is using the corner of a component and, of course, it will have a
corresponding set of apertures on the stencil to align to.
Alignment Point
Learned Model
Field of View Sample Window
Alignment Point
Learned Model
Field of View Sample Window
Problems and Limitations
Video models should never be considered as a first choice for alignment as there are
several disadvantages:
Due to the normal practice of using aperture reduction, the alignment point of the
stencil video model is unlikely to match that of the board. Therefore, the need to
program print offsets is common when using video models.
The stencil capture score deteriorates rapidly once the stencil is contaminated with
paste. Therefore, it is necessary to use the under-screen cleaner more often than is
desirable, sometimes after every print!
On a heavily populated board it is often difficult to find an area that contains a unique
image. The software may detect multiple possible targets within the field of view. If
this happens it may help to increase the Accept Score so that only the true video
model will be captured.
Create a new board file based on the one you created in objective 3 giving it the
name ‘Video’ and ID ‘video model practice’. Setup two sets of video models.
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