Thin Metallization Layer for Thermal Dissipation
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Solution Overview
Problem
Conventional plastic packages for electronic components, such as power transistors, face thermal performance limitations due to thick bonding materials with low thermal conductivity and high void content, which degrade as the lead frame bows during the bonding process, leading to inefficient heat dissipation in high power applications.
Innovation Solution
A thin metallization layer with a thickness of about 5 μm or less and a thermal conductivity of 60 W/m·K or greater, such as AuSn or AuSi, is used to attach the semiconductor die to a lead frame, which also acts as a heat sink, minimizing voids and ensuring a high-performance thermal interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional metallization bonding materials (PbSn or Pb-free solders) are used, then thermal conductivity is improved (30-50 W/m·K), but bond line thickness increases (15-25 μm or thicker) which degrades thermal performance
Solution Approach 1:
The patent changes the material parameters by using eutectic gold-silicon (AuSi) alloy with specific composition (79.3-81.2 wt% Au, 18.8-20.7 wt% Si) that enables both thin film deposition (5 μm or less) and high thermal conductivity (60 W/m·K or greater), resolving the contradiction between thickness and thermal conductivity
Solution Approach 2:
The patent uses a composite metallization layer combining gold and silicon in a eutectic composition, which provides superior thermal conductivity compared to conventional solders while enabling thinner bond lines, thus resolving the contradiction between thermal performance and bond line thickness
2Length of moving object
If epoxy bonding material is used, then bond line thickness can be reduced, but thermal conductivity decreases (20-25 W/m·K) limiting heat dissipation
Solution Approach 1:
The patent changes the material parameters by selecting eutectic AuSi alloy which inherently provides high thermal conductivity (60 W/m·K or greater) even at thin thicknesses (5 μm or less), overcoming the low thermal conductivity limitation of epoxies while maintaining thin bond lines
3Ease of manufacture
If conventional lead frame materials are used, then ease of manufacture is improved, but lead frame bows during bonding process due to pliability at bonding temperatures, degrading thermal interface
Solution Approach 1:
The patent changes the material parameters by using a lead frame with specific composition (5-15% In, 0.5-2.0% Zn, balance Pb) that maintains dimensional stability and flatness during bonding processes, preventing the bowing issue while remaining manufacturable
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 significantly enhances thermal performance by reducing voids and maintaining a flat thermal interface, allowing for effective heat dissipation and improved reliability in high power applications.
Implementation Method 1
The metallization layer has a thickness of about 5 μm or less and a thermal conductivity of about 60 W/m·K or greater
Implementation Method 2
The lead frame and electronic component usually have different CTEs (coefficients of thermal expansion). As such, the lead frame and component expand and contract at different rates during the bonding process
Data Source
AI summary
According to one embodiment, an electronic package includes a semiconductor die, a heat sink and a metallization layer interposed between the semiconductor die and the heat sink. The metallization layer attaches the semiconductor die to the heat sink. The metallization layer has a thickness of about 5 μm or less and a thermal conductivity of about 60 W/m·K or greater.