Browse Prior Art Database

Non-Destructive Torsional Chip Removal

IP.com Disclosure Number: IPCOM000041638D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 69K

Publishing Venue

IBM

Related People

Formichelli, AR: AUTHOR [+4]

Abstract

This chip removal probe 10 will break the solder ball bonds 12 of the chip 14 to the substrate 16 without damage to the chip substrate or substrate bond points. The probe 10 is a DELRIN* part of conical shape with the exit aperture dimensions of the see-through probe just exceeding those of maximum chip size and a thin wall for resilience. The construction of this probe results in some unique optical and mechanical characteristics. The use of black DELRIN allows it to create a quasi-darkroom condition needed for viewing under a microscope when the exit tip of the probe is brought very closely over a black silicon chip surface. The delicate wall thickness and height of the aperture provide just the right torsional resilience for a non-destructive removal, as will be seen later.

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Non-Destructive Torsional Chip Removal

This chip removal probe 10 will break the solder ball bonds 12 of the chip 14 to the substrate 16 without damage to the chip substrate or substrate bond points. The probe 10 is a DELRIN* part of conical shape with the exit aperture dimensions of the see-through probe just exceeding those of maximum chip size and a thin wall for resilience. The construction of this probe results in some unique optical and mechanical characteristics. The use of black DELRIN allows it to create a quasi-darkroom condition needed for viewing under a microscope when the exit tip of the probe is brought very closely over a black silicon chip surface. The delicate wall thickness and height of the aperture provide just the right torsional resilience for a non-destructive removal, as will be seen later. A pair of fiber-optic illuminator tubes 18 fixed nearly horizontally across the probe tip illuminate the edge of the chip, as shown in Fig. 2, resulting in a dark silhouette with bright edges. Some of the oblique grazing light scatters and hits the inside edges of the probe at exit giving the impression of a black window with illuminated edges. In actual practice the window appears as in Fig. 3, with the reflecting inner walls producing extended lines at corners. The net result is that one sees a black silhouette of the chip with sharp bright edges underneath a congruently shaped black window also with bright edges. All viewing is done normal to the chip surface, through and along the axis of the probe, with a microscope 20 having a long working distance and a good depth-of-field objective lens. When a fine adjustment is made to the substrate-carrying stage 22, through X-Y adjusting micrometer screws, the silhouette moves in relation to the black window. This is done until the edges of the silhouette are uniformly contained within the black window - with the final adjustment showing a uniformly illuminated slit around the chip (silhouette). At this moment, a small vertical movement (downward) of the probe 10 will result in the chip being contained within the probe aperture freely, without contact. Having completed the above alignment procedure, to remove a of discrete chip off a substrate, the probe 10 is moved down to about two-thirds of the height of the chip 14 (Fig. 4) to avoid contact with the periph...