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edfas.org 23 ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 22 NO. 3 highlighted using dark field because of the strong x-ray scattering within the crack interface. The phase contrast image confirms the location of the defects identified in the dark field image. Another example is shown in Fig. 6. It shows sidewall and lateral delamination of another SIP confirmed by a SEM cross section of a similar batch of failed samples (image on left). The absorption image does not show any abnormalitywhile the phase contrast anddark field radio- graphs confirmwhat the SEM cross section is showing for the batch of failed packages. Thenext example (Fig. 7), illustrates thepower of phase contrast to visualize voids within an organic layer. These results demonstrate the ability of the Talbot system to image voids in an organic layer with phase contrast imaging while lateral delamination is observed from the scattered x-rays that form the dark field image. DARK FIELD AND PHASE CONTRAST IMAGING OF CRACKS, FIBERS, AND DEFECTS WITHIN SOFT MATERIALS IN CFRP This example is chosen to illustrate that organic materials and matrices used in electronics may be easily inspected for defects and fiber orientation. Carbon fiber reinforced polymers are lightweight, tough materials used to manufacture numerous products. Some major applications are in aircraft body, sporting goods, and next generation motor vehicles. The composites are normally thermosetting resins such as epoxy, polyester, or vinyl ester reinforced with carbon fiber. As both fibers and composites are low Z materials, imaging and resolving these structures and theorientation of the fibers is very challengingwith almost every imaging modality, including destructive SEM cross sections. With the Talbot Interferometry system, the use of dark field and phase contrast imaging provides the contrast to resolve these features (Fig. 8). DETECTION OF WATER FILM WITHIN CRACKS AND VOIDS OR DISTINGUISHING BETWEEN DRY VS. WET INTERNAL INTERFACES Often it is difficult to determine the presence or absence of water or liquid filmwithin small cracks, micro voids, or micro capillary matrices or porous materials such as organic or ceramic filters. The following example is a proof of concept to demonstrate possible ways to determine the presence or absence of liquid films non- destructively within components. One example where this can be applied is dye and pry, the traditional FA technique to detect cracks or open circuits or other failure modes in solder joints or frac- tures. Here, failures such as cracks and fractures may be inspected aftermechanical drop/shock, thermal shock, or thermal cycling. The package or PCB is submerged in a dye material andplacedunder vacuumto force the dye to seep into any cracks and defects. The package is then dried in an oven typically overnight and pried open to inspect for the presence of dye. Two experiments involving infusion of water into ceramic porousmedia (Fig. 9) and sandstone (Fig. 10) were used as proofs of concept. CERAMIC POROUS MEDIA BEFORE AND AFTER DIPPING INTO WATER In the results shown in Fig. 9, the dry and wet samples can be qualitatively differentiated by both phase contrast and dark field contrast. On the other hand, one cannot Fig. 8 Radiograph of a carbon fiber reinforced polymer (CFRP). Phase contrast and dark field images exhibit considerably better contrast as compared to the absorption image. Sample courtesy of Dr. Tao Liu, Xi’an Polytechnic University, China.