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Method for a stress-reduced flip-chip package by implementing a thin die and a flexible tape

IP.com Disclosure Number: IPCOM000010575D
Publication Date: 2002-Dec-18
Document File: 3 page(s) / 168K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a stress-reduced flip-chip package by implementing a thin die and a flexible tape. Benefits include improved functionality and improved reliability.

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Method for a stress-reduced flip-chip package by implementing a thin die and a flexible tape

Disclosed is a method for a stress-reduced flip-chip package by implementing a thin die and a flexible tape. Benefits include improved functionality and improved reliability.

Background

              Stresses introduced by CTE mismatch significantly impacts package reliability. For a flip-chip package with a heat spreader, the CTE mismatch between Si die and the heat spreader and between the Si die and the package substrate become more severe, especially when the die size and package body increase.

              Conventionally, underfill is used to reduce the stress between the Si die and the package substrate, while a low-modulus die-attach material is used between the Si die and the heat spreader. Because the requirement for power dissipation keeps increasing, solder-type die attach is needed to meet thermal requirements. However, solder results in a more serious CTE mismatch issue than conventional die attach. The stress introduced by the CTE mismatch significantly impacts package reliability.

              In a conventional flip-chip package design, the Si die is ~750–790 mm thick (see Figure 1). The Si die is mounted to the package substrate, which is made of either ceramic or organic with die bumps and underfill. A heat spreader made of copper or composite material is mounted on top of the Si die with die attach between the Si die and the heat spreader. Epoxy sealant is used between the heat spreader edge and the package substrate. The typical CTEs are approximately 25, 4, and 28 for conventional organic substrate, Si die, and Cu heat spreader, respectively.

General description

      The disclosed method is a stress-reduced flip-chip package with a thin die and a flexible tape. Instead of mounting the flip chip directly to the package substrate, a flexible tape interconnects the Si die and the package substrate. The flexible tape can decouple the Si die and the package mechanically so that the stress caused by the CTE mismatch between the die and substrate can be significantly reduc...