Browse Prior Art Database

Method for a flip-chip package IHS with a stiffener

IP.com Disclosure Number: IPCOM000101595D
Publication Date: 2005-Mar-16
Document File: 2 page(s) / 85K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a flip-chip package integrated heatsink (IHS) with a stiffener. Benefits include improved functionality and improved performance.

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Method for a flip-chip package IHS with a stiffener

Disclosed is a method for a flip-chip package integrated heatsink (IHS) with a stiffener. Benefits include improved functionality and improved performance.

Background

      Direct socket loading (DSL) provides superior thermal performance using a thermal interface material (TIM) layer between the IHS and the heat spreader (HS). However, the flip-chip land grid array IHS can warp after direct socket loading (DSL). No conventional solution is available to improve flatness (see Figure 1).

      A conventional heatsink attachment can be modeled using an assembled DSL socket. The substrate thickness corresponds to an 8-layer package. When the DSL load is generated at 85 lb, the warpage of the IHS top surface is ~107 µm. After a heatsink load of 20 lb is imposed in addition to the DSL load, the warpage is reduce by only ~14 µm. Most of the HS load goes towards bending the board rather than flattening the IHS. Stiffening the board does not necessarily lessen the warpage because the HS load flattens the compliant contact springs.

General description

      The disclosed method is the addition of an integrated stiffener to the IHS underside. Supporting ribs decrease warpage post-DSL by ~25-30%. Increasing the thickness of the IHS above the die by ~0.5 mm decreases warpage by ~10%. Decreasing the die cavity (thickening the IHS sidewalls) provides improved IHS stiffness (see Figure 2).

Advantages

              The disclos...