X-ray systems use a nondestructive semiconductor failure analysis technique that is used to see the interior details of the package. An X-ray system works using the principle of dissimilar transmission of X-rays through different materials. Dissimilar transmission is utilized to create an image of various contrasts. X-ray imaging may be accomplished through a number of mediums: film, fluoroscopy, or image intensifying video systems are all appropriate methods.
Modern X-ray inspection equipment has a filament that creates an electron beam and uses it to excite a target, causing it to produce an X-ray. Once that has been done, the X-ray emissions are directed to and transmitted through the specimen, allowing the transmitted X-rays to be collected by a detector. The detector then translates the X-rays into electric signals, amplifies them, and then transforms them into an X-ray image.
The varying densities of the various materials that make up the specimen create a grayscale on the X-ray image. This is because a higher density material may block X-rays and can keep an image from being produced. The quality of the X-ray image is dependant upon not merely the proper use of the X-ray system, but also on the composition of the specimen, or what it consists of.
X-ray systems are used mainly to inspect for wiresweeping and other problems relating to wires. Die attach voids, package voids, and cracks are all problems that can be detected through this system. X-ray technology is also perfect for determining leadframe outlines. This method, however, produces low-resolution images, which limits its usefulness. This is because traditional X-ray systems use photosensitive films in order to record the image. This makes it hard to focus, and thus cannot be used for very detailed images.
Some materials used in semiconductor manufacturing cannot be X-rayed. Aluminum wires, for instance, do not show up on an X-ray image, as they are transparent to X-ray.