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Method for a TIM/underfill hybrid material and a one-step assembly process

IP.com Disclosure Number: IPCOM000019049D
Publication Date: 2003-Aug-27
Document File: 3 page(s) / 183K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a thermal interface material/underfill hybrid material and a one-step assembly process. Benefits include improved process simplification, improved yield, improved performance.

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Method for a TIM/underfill hybrid material and a one-step assembly process

Disclosed is a method for a thermal interface material/underfill hybrid material and a one-step assembly process. Benefits include improved process simplification, improved yield, improved performance.

Background

         A requirement exists to reduce the cost of device production by reducing through-put time (TPT) and simplify the assembly process for yield improvement.

Conventionally, underfill and thermal interface material (TIM) are applied at different assembly modules, which take about 6 hours total.

TIM/underfill hybrid material is a polymer material that performs the functions of both of TIM and underfill.

A one-step assembly process is a curing process for the hybrid material that replaces individual curing steps for underfill and TIM materials.

Conventional TIM for flip-chip (FC) packages is comprised of filler and polymer, such as silicone-oil, hardener etc. Metal filler is used primarily because of its high thermal-conductivity, 2.39 ~ 4.19 x 10^2 (W/.m.K). However, its low electric-resistivity, 1.60 ~ 2.69 x 10^(-8) (Ohm.m), leads to concerns of electrical-short failure for the hybrid material.

In contrast, Silica (SiO2) is conventionally used as a filler for underfill of FC packages. The Silica is an insulator, greater than 10^10 (Ohm.m). With this material, electrical shortage between each solder bump is not a concern. However, its thermal conductivity is quite low, 1.38 (W/.m.K).

General description

The disclosed method is a hybrid material that is a TIM for an integrated heat spreader (IHS) and an underfill for FC packages.

         The key elements of the method include:

•         Hybrid material composed of filler with high thermal-conductivity and high electric-resistivity

•         One-step TIM/underfill process for FC packages

Advantages

         The disclosed method provides advantages, including:

•         Improved process simplification due to dispensing and curing the hybrid material in one step

•         Improved yield due to reducing process steps

•         Improved performance due to high thermal conductivity and high electric resistivity

Detailed description

         The disclosed method is a TIM/underfill hybrid material with high thermal conductivity and high electric resistivity. The viscosity and coefficient of thermal expansion (CTE) of the hybrid material are also important. Viscosity affects dispensability of the material. A material with lower viscosity is preferable because it flows underneath the die through capillary action. The CTE must be also lower to match that of the bumps connecting the die...