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Accurate, Non-Destructive, Rapid Automatable Method to Measure C4 Volumes and Heights

IP.com Disclosure Number: IPCOM000046216D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Froot, HL: AUTHOR [+3]

Abstract

Rapid detection of chips which have reduced solder volume on one or more pads, high voids, or other chip yield detractors and rapid determination and detection of low chip heights or high chip tilt, or other module yield detractors, are desired.

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Accurate, Non-Destructive, Rapid Automatable Method to Measure C4 Volumes and Heights

Rapid detection of chips which have reduced solder volume on one or more pads, high voids, or other chip yield detractors and rapid determination and detection of low chip heights or high chip tilt, or other module yield detractors, are desired.

An X-ray photograph or fluoroscope provides density data of solder mounds on a C4 pad for flip-chip bonding, and integration of the density over the projected area of the pad is a direct measurement of its volume (Fig. l).

The system here is comprised of a set of preforms (Figs. 2-4) having the same Pb/Sn ratio as the solder pads, and with several precisely known heights (thicknesses). They should be chosen to cover the range of anticipated heights. These standards are placed along with features to be measured under an X-ray fluoroscope. As an option is a high magnification X-ray photo of the standards and features to be measured. This is not as easily automatable, and is limited in accuracy by film resolution, but it is less expensive and may be perfectly adequate for laboratory work.

The fluoroscope screen is then scanned by a plumbicon tube of an image analyzer (such as the Leitz TAS). Density data is sorted into a large number of preset gray levels, each gray level corresponding to a height. This correspondence is determined by the density level of the preform standards, with interpolation (e.g., linear) for intermediate values. The more standards used, the less extrapolation is required. Mul...