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Self Aligning Chip

IP.com Disclosure Number: IPCOM000037975D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Funari, J: AUTHOR [+2]

Abstract

The location of a chip with respect to a substrate is usually done by precisely aligning the chip solder balls to one or more pads on the substrate. Where the diameter of the pads is commensurate with the diameter of the solder balls, the chip will self align during the chip joining because of the high surface tension of the solder when in its liquid state.

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Self Aligning Chip

The location of a chip with respect to a substrate is usually done by precisely aligning the chip solder balls to one or more pads on the substrate. Where the diameter of the pads is commensurate with the diameter of the solder balls, the chip will self align during the chip joining because of the high surface tension of the solder when in its liquid state.

However, when the dimensions of the pads or conductors are of the order of one-half of the diameter of the solder balls, it becomes very difficult and costly to use the reflow method described above.

A solution to the problem is to form a "V" notch on the bottom of the ball, aligned perpendicularly to the chips edge, as shown in FIG. 1, where the ball 1, located on the underside of the chip 3, has a "V" notch 5 which straddles the conductor or line 7, thus centering the ball on the conductor or line.

To form the notches, a plurality of feeler gages of similar and appropriate thickness are ground to a ninety degree angle on one edge. The gages are then stacked as shown in FIG. 2, and are used to form the "V" notches simultaneously for all of the solder balls on the chip. The thickness of the gages determines the pitch of the notches, as is apparent from the drawing.

Disclosed anonymously.

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