Maintenance (Micron) workbook Iss07.pdf - 第16页

16 Issue 6, Nov 14 Objective MO5 Setup Video models The video model option is useful when ther e are no synthetic fiducials on the board or stencil, or when the fiducials ar e very poor quality. The secret of success is …

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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Issue 6, Nov 14

Objective MO6: Identify print cycle sequence

Observe the machine as it carries out a print cycle.

Number these actions in the correct sequence:

__Camera Moves to Board Stop

position

__Tooling clearance check

__Fiducial positions are captured

__Board travels to Board Stop position

__Press RUN

_ Board is clamped in rails

__Camera homes

__Board lifts to stencil

__Board exits machine

__Board Stop is lowered

__Board separates from stencil

__Stencil alignment completed

__Board is unclamped

__Board stop is raised

__Print stroke carried out

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