YesAX V3.1.2 - Software User Manual.pdf - 第187页
A dvance Inspection Features 14 -1 14 - Advance Inspection Features The Yes AX software is design ed for ease- of - use; hiding the underlying computation complexities. However, to get the optimal performance for inspect…
13-8 Part List and Part Libraries
On the Package Lib page it is possible to select multiple packages using a combination of the
mouse and the Shift- Ctrl keys.
The YesAX software ships with one Standard Package Library (StdPkg_AX1.pkg) that contains
all the common packages used in the industry. Having the standard package library speeds up the
setup of solder and lead inspection tremendously.
13.6 Pin Library
A pin is one or a stack of multiple solder inspection boxes on 3D slices. One pin is used to
inspect one solder joint of a BGA ball or a PTH pin. The Pin Library is a library that lists the
different types of pins. A new page is added in the List View to show the Pin Library. From the
pin library you can adjust inspection parameters for the pin.
Advance Inspection Features 14-1
14 - Advance Inspection Features
The YesAX software is designed for ease-of-use; hiding the underlying computation
complexities. However, to get the optimal performance for inspecting complex boards with small
components, a working knowledge of the underlying theory is helpful.
14.1 Mathematics of Fiducial Alignment
By default the YesAX software uses two alignment marks to correct for placement differences
between boards. Alignment marks have fixed XY locations. The software uses the fixed XY
locations as a reference to determine what compensation is needed for a particular board under
inspection. The software compensation works best if the alignment marks (fiducials) are located
on the bottom left and the bottom right corner of the board. It is recommended that the user
select the left alignment mark close to the bottom left corner of the board and the right alignment
mark close to the bottom right corner of the board whenever possible.
There are two kinds of positional compensations; one is translational and the other is rotational.
The software uses the left alignment mark to calculate translational compensation. For example,
the left mark has a defined position of (10, 10), and the software finds it to be at (12, 11). This
means in order to compensate the coordinates system needs to shift 2 units to the right in the X
axis and 1 unit up in the Y axis.
After the software compensates translationally, it proceeds to find the right alignment mark and
calculates the rotational compensation using software theta. Software theta is a technique that
mathematically rotates the user coordinate system to compensate for the mis-alignment of the
PCB. For example, there is a 2 degree offset in theta for the PCB. The user wants to go to (1000,
1000) on the PCB to inspect a component. The software calculates the corresponding camera
coordinates using the following algorithm:
X' = X Cos (A) + Y Sin(A)
Y'=-X Sin (A) + Y Cos(A)
In this case
X' = 1000*Cos(2) + 1000 * Sin(2)
Y'=-1000*Sin(2) + 1000 * Cos(2)
X'=1034.29
Y'=964.49
The software then commands the camera to go to (1034.29, 964.49). This is the same place at
(1000, 1000) on the PCB. The process is completely transparent to the user. The reverse
calculation is performed when displaying coordinates. The Status bar will show (1000, 1000).
The YesAX software uses a multi-layer scheme to handle coordinates. The top layer is the user
coordinates (the board or PCB coordinates). This is how the positions of parts on the board are
defined. This is the only coordinate the user will deal with directly. The bottom layer is the
physical coordinate where positions are defined by motor steps and encoder counts. The middle
layers include scaling, software theta, linear error compensation and error mapping. The layering
scheme allows the YesAX to have transferable Inspection Recipes without requiring the
machines to be built identically.
14-2 Advance Inspection Features
In general the 2 fiducials alignment works well, assuming the locations of the left and right
fiducials do not change relative to the board’s origin. This assumption holds true in most cases,
except when the dimensions of the boards change due to temperature or other factors. For
example, on an 8” by 10” PCB, if a higher temperature makes the board expand by 1/1000 then
the right fiducial would be off by 10 mil. In this case using the 2 fiducials alignment method
some parts on the board would be off by 10 mils. For high precision inspection the software also
provides a 3 fiducial alignment method. In addition to providing translational and rotational
compensation, the three fiducials alignment method compensates for expansion and contraction
of the PCB.
The 2 fiducial alignment technique is the default for board alignment. To use the 3 fiducial
alignment technique, enable it in the System Default dialog. To launch the dialog, select
System>Default Parameters from the main menu.
If you re-define the alignment marks after the feature is enabled, the software will prompt to
train 3 alignment marks.
14.2 Understanding the Video Parameter
Fiducial alignment only ensures that the camera moves to the correct location, which means the
position of the cross hair is where it is supposed to be, as defined in the program. However,
inspections take place in the entire field of view not just where the cross hair is at. The video
parameters ensure all the pixels in the field of view are at their correct locations.