Issue link: https://iconnect007.uberflip.com/i/304995
26 SMT Magazine • May 2014 ball > 3 as defect) as a start, then look at the measurement data to adjust according to the process. We also share our experience with AXI vendors, and provide feedback to them as well as working together with them for better and improved AXI performance. Table 10 uses two subtypes for this BGA due to two different types of pad on the board: pad diameter is 19 mils for inner balls, and 21 mils for outer balls on BGA. For AXI 1, we have reduced HIP escaped number from 27 to 15 with the same false calls; for AXI 4, we have reduced false call number from four to one with the same defects escaped. This best practice shows good results with the two dif - ferent AXI machines. In order to verify our AXI / 2DX results, we performed 3D CT board-level x-ray inspection (limited angle computer tomography). This is a novel technique permitting areas of a very large board to be examined using 3D CT without cut- ting the board. Figures 9–12 show the CT im- ages and results. Figure 9 demonstrates clearly that pin G32 has a 9-micron crack. This poten- tially critical defect was identified with offline 2D X-Ray (2DX image, Figure 1) and confirmed HEaD-IN-PILLoW X-Ray INSPECTIoN continues feATuRe Figure 8: axi 4 images of detected hip; escaped hip, and false call pin (board #495). Table 8: Test summary with AXI 4. Table 9: Testing summary with AXI 1.