YesAX V3.1.2 - Software User Manual - 第144页

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General Inspection Methodology 10-49

7. Check the BGA group parameters and make sure the binary threshold works for current

slice. The binary threshold of the BGA group algorithm for 3D slices and 2D images are

not always the same.

8. Switch to slice -15, use copy “IB to current slice” function and create all inspection boxes

for slice -15. For BGA group algorithms, since the ball size is smaller, we normally apply

15% (sometimes 12%) for the ball size check. The binary threshold will also be different

and needs to be re-adjusted. For BGA pin inspection algorithm, it is important to the ball

diameter for slice 0 and slice -15 to different number. After slice -15 is done, do the same

thing for slice 15. Normally ball sizes for slice 15 and -15 will be about the same, which

leads to similar parameter values for these two slices. Remember to update package and

part library at the end. This way a new package for 3D BGA inspection is created.

9. For BGA mounted on bottom side, depends on the board thickness the middle layer is

normally set to a negative number, and the other two slices are set accordingly. For

example, if the board thickness is 60 mil and the BGA package is programmed under 1”

FOV, we may set the middle slice of the BGA to be slice number -60, and the other two

slices to -45 and -75, respectively.

3D X-Ray Inspection Methodology 11-1

11 - 3D X-Ray Inspection Methodology

The X3 AXI system is an automated inline X-Ray inspection system with full 3D capabilities.

The X3 AXI system can not only do a full 2D inspection of a PCB but it can also do a 3D

inspection of the PCB. The X3 can also combine 2D and 3D to optimize between speed and

capability by using 3D only where needed.

A standard 2D X-Ray machine only has one X-Ray view, the top-down view that sees through

an object from top to bottom. For the X3, other than the regular top-down view, it can “look” at

the object from 8 different side angles and then by combining them using Digital Tomosynthesis

Reconstruction algorithms, creates slices parallel to the board surface. These slices can separate

the top side from the bottom side so that each side of the double sided board can be

independently analyzed.

The height offset of the top surface of the board can be measured using a laser device and this

information is used to compensate for board warp. It is possible to setup the parameters and the

position where the laser measurements will have to be made and the range over which the

measurement will be effective.

Although the X3 AXI system is a fully automated 3D x-ray inspection system, it has significant

manual capabilities. You can simply load a board, position the part under x-rays, select the

appropriate power level, add/edit a 3D site and scroll up and down perpendicular to the surface

of the board.

11.1 Key Applications for 3D Inspection

11.1.1 Separate Top and Bottom Side Parts

Because X-ray is able to passing through the circuit board, it produces a density projection of the

field of view. The dense areas such as the solder joints appear as a dark area on the image. For

double sided boards with solder joints on both sides of the board, the dark areas from two sides

could overlap. That causes difficulty for inspecting the quality of the solder joints when they are

obscured by the solder joints from the other side. 3D X-ray imaging solves that problem by

creating slices represent different side. Solder joint from the top side would apparent in a

different slice as the solder joints from the bottom side. The separation allows inspection for

solder quality on both side of the circuit board.