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Elastic Thermal Compensation of Chip Carriers

IP.com Disclosure Number: IPCOM000118613D
Original Publication Date: 1997-Apr-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Jimarez, MA: AUTHOR [+3]

Abstract

Significantly improved reliability of the Flip Chip Attach (FCA) joints in Organic Chip Carriers can be achieved by incorporating a semi-elastic dielectric layer, with a Young's Modulus E in the range of 50,000 psi > E > 20,000 psi, between the Controlled Collapse Chip Connection (C4)-underfill and the carrier laminate.

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This is the abbreviated version, containing approximately 71% of the total text.

Elastic Thermal Compensation of Chip Carriers

      Significantly improved reliability of the Flip Chip Attach
(FCA) joints in Organic Chip Carriers can be achieved by
incorporating a semi-elastic dielectric layer, with a Young's Modulus
E in the range  of 50,000 psi > E > 20,000 psi, between the
Controlled Collapse Chip Connection (C4)-underfill and the carrier
laminate.

      In Fig. 1, a semi-elastic dielectric layer (2) is incorporated
between the C4-underfill (4) and the laminate (3).  During a thermal
cycle, the low-modulus layer (2) conforms to the movement of the
C4-underfill (4) on one side and to the organic laminate (3) on the
other side, decoupling the silicon chip (1) from the associated
carrier.  Such compliance reduces the module warpage and the bending
stresses.  Model analysis and experimental data indicate that the
optimal thickness of the decoupling layer is in the range of 1/4 to
1/2 of the C4-underfill gap.  Fig. 2 shows experimental warpage data
obtained by using Moire' interferometry for a conventional laminate
chip carrier and a carrier with the dielectric, low modulus layer.
The decoupling, compensation layer was made using a photo-imageable
Interpenetrating Polymer Network (IPN) material.  It is seen that the
relative bending of the module with the semi-elastic compensation
layer is smaller than that of the conventional laminate at all
temperatures and approaches zero at about 110 degrees C.  At this
temperature, the IPN material be...