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Method for heat spreader designs for multi-die packages

IP.com Disclosure Number: IPCOM000008752D
Publication Date: 2002-Jul-09
Document File: 7 page(s) / 165K

Publishing Venue

The IP.com Prior Art Database

Abstract

Method for heat spreader designs for multi-die packages. Benefits include improved functionality, improved thermal performance, and improved reliability.

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Method for heat spreader designs for multi-die packages

Method for heat spreader designs for multi-die packages. Benefits include improved functionality, improved thermal performance, and improved reliability.

Background

              Utilizing current packaging integrated heat spreader (IHS) assembly technology several challenges have been encountered when building large packages with an off center die and large 38.5-mm heat spreader (see Figure 1). The substrate with the die attached is bowed with the substrate edged deflected below the die.  The IHS is attached and the substrate bow turns into a “W”, causing the die - to bow upward at the center.  The heat spreader has a slight defection due to the substrate warpage.  The substrate has a tendency to flatten out post bake.  This causes the die to flatten and the TIM BLT to increase requiring the polymeric TIM to elongate. Typically the greatest BLT changes post reliability are observed in the corners or center. The increased warpage has led to increased post reliability corner thermal degradation.  

              The stress is greater for large and/or off center die due to increased substrate deflection. The increased warpage has increased shear stress concentration at the sealant to substrate and sealant to IHS interface leading to an increase in sealant delamination and decreased yield.

              Products designed with two or more die that are not centered can undergo greater stress than measured on single die flip-chip products. Constraining the heat spreader and substrate and minimizing the strain improves reliability.  By attaching the heat spreader closer to the substrate the warpage is reduced, as well as the stress at the TIM interface.

      No conventional solution exists for multiple die.

      Conventional lip designs have only 50% material utilization for large heat spreaders (see Figure 2).

General description

              The disclosed method is a design with heat spreaders that facilitate additional bonding between heat spreaders and substrates on packages w...