Die Backside Metal and Solder TIM Structure for Package Warpage Control
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Solution Overview
Problem
Next-generation chip-scale packages face challenges in thermal and warpage management due to reduced space for integrated heat spreaders and stiffeners as they become smaller and thinner, necessitating an innovative approach for effective thermal and warpage mitigation.
Innovation Solution
A package architecture featuring a die backside metal (DBM) with a high coefficient of thermal expansion, bonded to a die using a solder thermal interface material (STIM) that combines the functions of a heat spreader and stiffener, providing enhanced thermal conductivity and warpage control through intermetallic compounds and filler particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If IC dies are made smaller and thinner to reduce package footprint and thickness, then package dimensions are reduced, but thermal management and warpage control capabilities deteriorate due to reduced space for heat spreaders and stiffeners
Solution Approach 1:
The patent merges the functions of the heat spreader and stiffener into a single integrated component called the integrated heat spreader-stiffener (IHSS). This consolidation allows the package to maintain both thermal management and warpage control capabilities while reducing overall package size, directly resolving the contradiction between miniaturization and functional performance.
Solution Approach 2:
The IHSS component is designed to perform multiple functions simultaneously: it acts as both a thermal management device (heat spreader) and a structural support element (stiffener). This multi-functionality enables the reduced package size to maintain adequate thermal and mechanical performance without requiring separate dedicated components.
2Area of stationary object
If space for integrated heat spreaders and stiffeners is reduced to achieve smaller package size, then package footprint decreases, but thermal conductivity and warpage mitigation effectiveness worsen
Solution Approach 1:
By combining the heat spreader and stiffener into the IHSS, the patent maximizes the thermal management functionality within the available space. The integrated design ensures that the thermal conduction path is optimized while maintaining structural integrity, preventing deterioration of heat dissipation despite reduced footprint.
Solution Approach 2:
The IHSS utilizes composite material structures that provide both high thermal conductivity and high mechanical stiffness. This allows the component to effectively conduct heat away from the die while simultaneously providing warpage mitigation, resolving the contradiction between reduced area and maintained thermal performance.
3Length of moving object
If package components are minimized to achieve chip-scale dimensions, then device size is reduced, but the ability to manage extreme flexure and solder joint integrity deteriorates
Solution Approach 1:
The integration of stiffener functionality into the heat spreader creates a structurally reinforced component that resists extreme flexure. This strengthened structure protects solder joints from mechanical stress and damage, maintaining joint integrity even in the minimized chip-scale package configuration.
Solution Approach 2:
The IHSS is designed with specific material and geometric parameters optimized for mechanical strength and flexure resistance. By carefully controlling thickness, material composition, and structural geometry, the component provides adequate protection against extreme flexure while maintaining the small chip-scale dimensions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively mitigates warpage and thermal management by suppressing curvature reversal, maintaining convex warpage at high temperatures, and reducing thermal resistance, thus ensuring the integrity of solder joints and preventing damage from extreme flexure.
Implementation Method 1
a thermal interface material (TIM) comprising a first metal over the backside, wherein the TIM has a thermal conductivity of not less than 40 W/mK
Implementation Method 2
a die backside material (DBM) comprising a second metal over the TIM, wherein the DBM has a CTE of not less than 18×10−6 m/mK
Implementation Method 3
wherein an interface between the TIM and the DBM comprises at least one intermetallic compound (IMC) of the first metal and the second metal
Data Source
AI summary
An integrated circuit (IC) package comprising a die having a front side and a back side. A solder thermal interface material (STIM) comprising a first metal is over the backside. The TIM has a thermal conductivity of not less than 40 W/mK; and a die backside material (DBM) comprising a second metal over the STIM, wherein the DBM has a CTE of not less than 18×10−6 m/mK, wherein an interface between the STIM and the DBM comprises at least one intermetallic compound (IMC) of the first metal and the second metal.