Browse Prior Art Database

RECESSED IC SUBSTRATE FOR TUNING PAD AND RF SHIELD CONTAINMENT

IP.com Disclosure Number: IPCOM000006223D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-14
Document File: 2 page(s) / 89K

Publishing Venue

Motorola

Related People

Allen D. Hertz: AUTHOR [+2]

Abstract

This paper and the following sketches describe a unique means for shielding RF emissions from the underside of the IC while insulating IC tuning pads. This is accomplished without reflow interference and without an increase in component height.

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MOlYlROlA INC. Technical Developments Volume 13 July 1991

RECESSED IC SUBSTRATE FOR TUNING PAD

AND RF SHIELD CONTAINMENT

by Allen D. Hertz and David A. Tribbey

  This paper and the following sketches describe a unique means for shielding RF emissions from the underside of the IC while insulating IC tuning pads. This is accomplished without reflow interference and without an increase in component height.

  The outputs of various IC's are drifting during the current packaging process. To increase yields, the K's can be tuned subsequent to the packaging pro- cess. To tune these K's, additional pads are. required (Figure 1) on the substrate surface. These "tuning" pads must not contact PC board runners or have. the opportunity to short to the printed wiring board during reflow. The present method of insulating these pads requires a 2-4 mil thick material such as polyimide pressure sensitive tape (Figure 2) on the underside of the IC substrate. The non-planarity from the addi- tional material use to insulate the tuning pads could inhibit proper reflow characteristics.

  It is desirable to maintain a flush reflow surface on the underside of the IC to allow for proper reflow and IC seating. When the area of interest (Figure 3) is recessed approximately 2 mils, this would act as a reservoir for an insulating material. When the recess is made deeper, one could place three layers of materi- als to include an RF emissions shield. When the

thickness of the materials did not exceed the depth of the recess, the additional materials would not interfere with reflow.

  A means to accomplish this would be to...