Browse Prior Art Database

Laser Trimming on Substrate Mounted Chips

IP.com Disclosure Number: IPCOM000050959D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Riggio, SR: AUTHOR

Abstract

In a contemporary integrated-circuit packaging technology, thin film resistors formed on the underside of multichip carriers are adjusted by laser trimming. For this purpose, the chips are individually powered through the contact pins which connect them to the carrier.

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Laser Trimming on Substrate Mounted Chips

In a contemporary integrated-circuit packaging technology, thin film resistors formed on the underside of multichip carriers are adjusted by laser trimming. For this purpose, the chips are individually powered through the contact pins which connect them to the carrier.

A problem in respect to this practice is that traditionally such carriers have many variations of chip-mounting topography and, therefore, require associated variations in the sites for placement of the thin film trimming resistors. Consequently, the fabrication of such carriers is not easily standardized and there may be an associated inventory problem in respect to multiple card numbers.

As indicated in the drawings, this problem can be eliminated by locating the thin film trimming resistors on the chip surface rather than on the carrier surface. The problem in this respect is that the only surface usually available for this purpose is the surface of the chip which faces the carrier, thereby potentially obscuring or hiding the resistors from view by traditional laser trimming machinery.

This problem is overcome presently by providing openings in the carrier at chip-mounting sites. These serve as windows for the laser trimming beam (Fig.
2).

Fabrication of such carrier holes is a relatively simple manufacturing procedure, by comparison to the process for placement of thin film resistors. It does not require a discrete card number personality for each carri...