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Substrate with a Low Coefficient of Thermal Expansion

IP.com Disclosure Number: IPCOM000100647D
Publication Date: 2005-Mar-16
Document File: 2 page(s) / 18K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a substrate that reduces warpage in packages. The substrate contains negative thermal expansion fillers in the dielectric layers; these layers enable the substrate to have a lower coefficient of thermal expansion (CTE) than is currently available. By varying the amount of filler in each dielectric layer, a gradient of CTE can be established in the substrate.

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Substrate with a Low Coefficient of Thermal Expansion

Disclosed is a method for a substrate that reduces warpage in packages. The substrate contains negative thermal expansion fillers in the dielectric layers; these layers enable the substrate to have a lower coefficient of thermal expansion (CTE) than is currently available. By varying the amount of filler in each dielectric layer, a gradient of CTE can be established in the substrate.

Background

Currently, during package assembly and post-assembly, exposure to temperature cycles and moisture can increase package warpage. This substrate warpage causes increased stress in the first-level interconnect, second-level interconnect, the die, and the thermal interface; it can also increase warpage of the HIS, thereby reducing TIM2 performance.

The problem is currently solved by mixing calcium carbonate and talc and/or silica fillers with the polymer bulk resin, which results in a reduction in the CTE of the composite dielectric layer  (see Figure 1).  The thermal expansion of the polymer is reduced by adding these low CTE fillers, and the bulk CTE of the dielectric layer is reduced if the mixtures are created properly. 

General Description

The disclosed method uses substrates that contain negative thermal expansion fillers in the dielectric layers; these layers enable the substrate to have a lower CTE than is currently available. The low CTEs are tailored by controlling the type and amount of filler, to balance the CTE of the s...