The purpose of the analysis is to find out whether die attachment can be made compliant enough to protect the chip from excessive bowing of the substrate. We showed that in a typical situation, when the substrate (card) has a significantly larger flexural rigidity than the chip, the mechanical behavior of the chip-substrate assembly is governed by a parameter $u=lK/4D14$, where l is half the chip’s length, D1 is its flexural rigidity, and K is the through thickness spring constant of the attachment. We found that in order for a die attachment to have an appreciable effect on chip bowing, this parameter should be considerably smaller than 2.5. In the performed numerical example, for a 2 rail thick die attachment, this value corresponds to Young’s modulus of only 2300 psi. Therefore we conclude that conventional epoxy adhesives cannot provide sufficient buffering effect in this case, and, if such adhesives are used, the curvature of the die will be practically the same as the curvature of the substrate. In this situation, thinner dies will result in lower bending stresses. However, if low modulus die attachment materials, such as silicone gels, are considered, then employment of thicker dies might be advisable.

1.
Chang, F.-V., 1983, “Thermal Contact Stresses of Bi-Metal Strip Thermostat,” J. Appl. Math. Mech., Vol. 4, No. 3.
2.
Chen, W.-T., and Nelson, C. W., 1979, “Thermal Stresses in Bonded Joints,” IBM J. Res. Div., Vol. 23, No. 2.
3.
Goland, M., and Reissner, E., 1994, “The Stresses in Centered Joints,” ASME Journal of Applied Mechanics, Vol. 11.
4.
Grimado, P. B., 1978, “Interlaminar Thermal Stresses in Layered Beams,” J. Thermal Stress, Vol. 1.
5.
Suhir, E., and Lee, Y.-C., 1990, “Thermal, Mechanical, and Environmental Durability Design Methodologies in Electronic Packaging,” Handbook of Electronics Materials, ASM International.
6.
Suhir, E., 1986, “Stresses in Bi-Metal Thermostats,” ASME Journal of Applied Mechanics, Vol. 53, No. 3.
7.
Suhir, E., 1987, “Die Attachment Design and its Influence on the Thermally Induced Stresses in the Die and the Attachment,” Proc. of the 37-th Elect. Comp. Conf., IEEE, Boston, MA.
8.
Suhir, E., 1991, Structural Analysis in Microelectronic and Fiber Optic Systems, Vol. 1, Van-Nostrand Reinhold, New York.
9.
Volkersen
O.
,
1938
, “
Die Nietkraftverteilung in zubeanspruchten Niettverbindungen mit konstanten Lasehonquerschmitten
,”
Lufifahrforschung
, Vol.
15
, p.
41
41
.
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