Page 137 - Building A Succesful Board-Test Strategy
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Inspection as Test 123
Figure 3-24 Some industry experts recommend staggering components on top and
bottom of double-sided boards. (Test & Measurement World, June, 2000, p. 16, Used by
permission.)
X-Ray(B) X-Ray(A) X-Ray(B) X-Ray (A)
\
s
\
V.
Detector Detector Detector Detector
(A) (B) (A) (B)
Top Side in Focus Bottom Side in Focus
Figure 3-25 Keeping each plane of the board in focus. (Courtesy Agilent
Technologies.)
Three-dimensional x-ray techniques, also known as x-ray laminography,
tomography, and digital tomosynthesis, permit looking separately at two sides of
the board by focusing on one surface while the other surface blurs into the back-
ground, as in Figure 3-25. It can even be used to examine inner layers of a multi-
layer board. Figure 3-26 shows a two-sided single inline memory module (SIMM),
its transmission x-ray image, and its 3-D image.
