Flip-Chip Bonding Structure Using Silicon Substrate and Si-Bumps
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Solution Overview
Problem
Current flip-chip technologies face challenges in mm-wave applications due to mismatches in thermal expansion coefficients, thermal conductivity, dielectric constants, and parasitic mode suppression between MCM-D substrates and active components, leading to reliability issues and poor heat dissipation.
Innovation Solution
A flip-chip bonding structure using a silicon substrate with Si-bumps matching the thermal expansion coefficient of active components, combined with a dielectric layer and transmission lines to enhance thermal conductivity and reduce parasitic modes, thereby improving reliability and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alumina substrate is used as flip-chip substrate, then CTE matching with active components is achieved, but dielectric constant is high causing proximity effects and thermal conductivity is low causing poor heat dissipation
Solution Approach 1:
The patent uses a silicon substrate instead of alumina, combining the advantages of low dielectric constant (reducing proximity effects) with high thermal conductivity (improving heat dissipation). The silicon substrate maintains CTE compatibility with active components while providing superior thermal and electrical properties compared to alumina.
2Loss of energy
If silicon substrate is used as flip-chip substrate, then thermal conductivity is high improving heat dissipation, but dielectric constant is low causing poor transmission line characteristics
Solution Approach 1:
The patent applies different dielectric materials to different regions: a first dielectric material with low dielectric constant is used in the transmission line formation region to ensure good signal transmission, while a second dielectric material is used in other regions. This local differentiation allows the silicon substrate to provide high thermal conductivity overall while maintaining good transmission characteristics where needed.
3Reliability
If BCB dielectric layer is coated on silicon substrate to improve transmission characteristics, then dielectric constant is low reducing proximity effects, but CTE mismatch with active components causes bonding bump cracks
Solution Approach 1:
The patent uses a first dielectric material with low dielectric constant specifically in the transmission line formation region to reduce proximity effects, while using a second dielectric material in other regions that provides better CTE matching with active components. This spatial differentiation of material properties resolves the contradiction between transmission characteristics and bonding reliability.
4Manufacturing precision
If MCM-D substrate is used, then high resolution patterns are achieved for mm-wave frequency, but parasitic mode suppression is poor and thermal management is insufficient
Solution Approach 1:
The patent employs a silicon substrate with specific dielectric materials to suppress parasitic modes while maintaining the high resolution pattern capabilities of MCM-D technology. The silicon substrate's inherent properties, combined with appropriate dielectric layer selection, provide both the manufacturing precision needed for mm-wave applications and the parasitic mode suppression required for reliable operation.
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
The solution provides improved thermo-mechanical reliability and efficient heat dissipation by matching thermal expansion coefficients and utilizing silicon's higher thermal conductivity, reducing stress and enhancing overall performance of the flip-chip bonding structure.
Implementation Method 1
the relatively low thermal conductivity of the alumina substrate, 30 W/(m·K), in a poor dissipation of the heat generated by the active components
Implementation Method 2
the CTE of the MCM-D substrate has to be similar to that of the active components mounted on the MCM-D substrate to improve the thermo-mechanical reliability of the flip-chip structure
Data Source
AI summary
Flip-chip bonding structures using an MCM-D substrate are disclosed. A flip-chip bonding structure using an MCM-D substrate includes: a silicon substrate, a Si-bump disposed at a predetermined position of the silicon substrate, wherein a material of the Si-bump is the same as the silicon substrate, a dielectric layer disposed on the silicon substrate and a transmission line formed on the Si-bump to connect to a circuit formed on the dielectric layer.