Wafer Level Package Metal Cover Thermal Management
Solution Overview
Problem
Conventional semiconductor packaging technologies face challenges in providing adequate thermal conductivity and mechanical protection for high-density, small-sized semiconductor devices, particularly during reliability testing, and they often require complex processes that increase costs and manufacturing time.
Innovation Solution
A wafer level package structure is developed with a metal cover made of alloy 42 (Ni 42% and Fe 58%) and a protective film on the backside of the silicon wafer, which enhances thermal conductivity and mechanical protection, while also simplifying the packaging process by omitting lead frames and substrates, and using Under Ball Metallurgy (UBM) for improved electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional packaging is used, then the die is protected from moisture and mechanical damage, but the thermal conductivity is insufficient and the package size is large
Solution Approach 1:
The patent merges the protective cover and the heat dissipation function into a single metal cover component. The metal cover directly contacts the silicon wafer backside, combining mechanical protection with thermal conduction pathways, eliminating the need for separate thermal management components and reducing overall package volume.
Solution Approach 2:
The patent employs a composite structure consisting of a metal cover (providing thermal conductivity and mechanical strength) combined with a silicon wafer (providing electrical isolation and structural support). This composite approach allows the package to achieve both high thermal conductivity and compact size by leveraging the complementary properties of different materials.
2Productivity
If wafer level packaging is used, then the production cycle time is reduced and cost is lowered, but the thermal conductivity and mechanical protection are insufficient
Solution Approach 1:
The patent changes the material parameter of the cover from conventional plastic or ceramic to metal, which fundamentally alters the thermal conductivity parameter. This material substitution enables wafer-level packaging to achieve the thermal management performance previously only available in more complex, time-consuming packaging processes.
Solution Approach 2:
The patent applies local quality enhancement by concentrating thermal management functionality at the critical interface between the silicon wafer and the metal cover. The metal cover is designed with specific contact areas and thickness to optimize heat dissipation pathways locally, providing enhanced thermal conductivity where it is most needed without increasing overall package complexity.
3Length of moving object
If the package is made thinner, then the package size is reduced, but the mechanical protection and thermal conductivity are compromised
Solution Approach 1:
The patent uses a composite structure where the metal cover provides both mechanical strength and thermal conductivity in a thin profile. The combination of metal (for strength and thermal conduction) and silicon wafer (for structural support and electrical isolation) enables the package to maintain high mechanical protection and thermal performance while achieving a reduced overall thickness.
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 better thermal conductivity, mechanical protection, and reduced manufacturing complexity, leading to improved packaging performance and reliability during testing, with a thinner package design that is more efficient and cost-effective.
Implementation Method 1
a metal layer attached on the wafer by an adhesive material
Implementation Method 2
a metal layer attached on the wafer by an adhesive material
Data Source
AI summary
A wafer level package comprises a wafer having a plurality of dice formed thereon; a thinner metal cover with a cavity formed therein attached on the wafer by an adhesive material to improve thermal conductivity of the package. A protection film is formed on back side of the metal cover and filled into the cavity, thereby facilitating for laser marking and obtaining a better sawing quality of the package.