Browse Prior Art Database

Measurement of Tension in Polyimide Film Chip Carrier Modules

IP.com Disclosure Number: IPCOM000040567D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Desai, KV: AUTHOR [+3]

Abstract

Fig. 1 shows a polyimide film chip carrier comprising a thin polymer film 1 to which a chip 2 is attached, e.g., by soldering. Circuit lines (not shown) are deposited on the polymer film 1 on one or both sides to establish connection with chip 2. As seen in Fig. 1, the film 1 is anchored to a circuit card 3 by solder joints 4. Because the polymer film 1 is thin (typically, a fraction of a mil thick), tension is placed on the film 1 to prevent drooping. This tension subjects module components to high stress and should be known to the designer. The following describes an indentation method which allows measurement of this tension. The tension placed on the polymer film 1 is measured by pressing the film down and measuring its rigidity.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 67% of the total text.

Page 1 of 2

Measurement of Tension in Polyimide Film Chip Carrier Modules

Fig. 1 shows a polyimide film chip carrier comprising a thin polymer film 1 to which a chip 2 is attached, e.g., by soldering.

Circuit lines (not shown) are deposited on the polymer film 1 on one or both sides to establish connection with chip 2. As seen in Fig. 1, the film 1 is anchored to a circuit card 3 by solder joints 4.

Because the polymer film 1 is thin (typically, a fraction of a mil thick), tension is placed on the film 1 to prevent drooping. This tension subjects module components to high stress and should be known to the designer. The following describes an indentation method which allows measurement of this tension. The tension placed on the polymer film 1 is measured by pressing the film down and measuring its rigidity. k = P y where P = force applied to membrane

y = distance membrane deflects

k = stiffness value of membrane and obtaining the tension anywhere in the membrane (T) as a function of k. In a situation where a thin polyimide film membrane is unattached to other components (Fig. 2), then a central indentation yields by the laws of statics the membrane tension:
T = KL____, (lb/in) (2) 16X where k = stiffness value (as derived in Equation (1))

L = length of membrane

X = distance from center of membrane In the situation where a rectangular object, i.e., a chip, is attached to the middle of the membrane (Fig. 3), then depressing it by a force P to a distance y will again yield the s...