Characterization of Alpha Sources in Packages
Original Publication Date: 1980-May-01
Included in the Prior Art Database: 2005-Feb-13
Each alpha-particle hit on a charge-coupled device (CCD) gives rise to one or more errors. The distribution of errors per hit can be determined and plotted as shown for AM /241/ in Fig. 1 and a 50/50 mixture of U/TH in Fig. 2. Using a series of ratios of U/TH, in a standard part, set to approximate the geometry of the CCD package sources, one can obtain characteristic curves for the various ratios--e.g., 80/20, 60/40, etc. The standard can be machined to slip over the well in place of the original lid, to simulate ceramic edges as seen by a face up chip, or to simulate the various geometries seen by CCD devices as well as the composition. The relative composition of U/TH can then be obtained by a comparison of the profile obtained with a standard to that seen in the sealed package.