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Ultrasonic Microdeletion for Engineering Change and Defect Repair

IP.com Disclosure Number: IPCOM000046111D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Hammer, R: AUTHOR [+2]

Abstract

This article describes a technique for microdeletion of thin film lines with an ultrasonically driven tool.

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Ultrasonic Microdeletion for Engineering Change and Defect Repair

This article describes a technique for microdeletion of thin film lines with an ultrasonically driven tool.

In packaging chips, the fan-out lines from C4 solder ball pads to EC (engineering change) pads, chips, as well as X-Y signal wiring planes can be fabricated on thin layers of polyimide or glass. The lines may be between 6 to 25 microns wide and 4 to 5 microns thick, of Cr-Cu-Cr or Cr-Cu Ni metallurgy. The dielectric layers separating the different layers of metallization may be typically 8 microns thick.

In such a package, localized line deletion will be needed for engineering changes and defect repair. For engineering change, fan-out lines from EC pads to signal planes are deleted to isolate the internal connection. For defect repair, the signal lines in the X or Y planes may be shorted to adjacent lines. The lines are repaired by deleting the shorts between the lines.

Laser deletion is suitable for both of the above, i.e., engineering change and defect repair, when the metallurgy is directly over the ceramic with no additional insulator between the metallurgy and ceramic. This technique is directed at a scheme which requires polyimide.

Experimental Technique

Line deletion is done by ultrasonically vibrating the section of line to be deleted. This is accomplished by bringing an ultrasonically driven tool in contact with the line. The ultrasonic vibration induced in the segment of line in physical contact with the tool weakens the adhesion between the metal and the substrate and causes a local delamination. The tool touches only the metal line and not the substrate. The deletion technique depends on the adhesion failure between the metal and the substrate at the interfacial region caused by intense ultrasonic oscillatory motion of the tool. The amplitude of this oscillatory motion is of the order of 1 to 2 microns and is much less than the width of the line to be deleted. The size and shape of the deletion section is determined by the geometry of the tool tip and can be made as small as 6 microns by commercially available diamond-tipped tools.

The experimental set up is shown in Fig. 1. A diamond-ti...