SiC Semiconductor Package Adhesion Layer for Moisture Resistance
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Solution Overview
Problem
Silicon Carbide (SiC) power devices face challenges in combining high voltage ruggedness and moisture resistivity due to the difficulty in finding suitable material combinations for encapsulating mold compounds that meet adhesion and hermeticity requirements across various material spectra used in SiC product architecture, often failing to achieve MSL level 1 certification for moisture resistivity.
Innovation Solution
A semiconductor device comprising a lead frame, a semiconductor chip, and a mold with strategically applied adhesion promoters, such as silane-based, metal oxide dendrite, brown/black oxide, or PI-based adhesion promoters, to enhance adhesion between the mold and the lead frame or chip surfaces, and between different chip layers, ensuring proper adhesion and hermeticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard encapsulating mold compounds are used for SiC power devices, then the device structure is simple and manufacturing is easy, but adhesion and moisture resistivity are insufficient, failing to achieve MSL level 1 certification
Solution Approach 1:
An adhesion promoter layer is introduced as an intermediary between the mold compound and the underlying materials (lead frame, semiconductor chip, passivation layers). This intermediate layer specifically addresses the adhesion problem without requiring complete redesign of the entire material system, enabling MSL level 1 certification while maintaining reasonable manufacturing complexity
Solution Approach 2:
The solution employs composite material structures by combining the mold compound with an adhesion promoter layer that contains organic compounds and nanoscale ceramic grains. This composite approach leverages the moisture resistance of the mold compound and the adhesion properties of the promoter layer to achieve both reliability requirements
2Adaptability or versatility
If multiple different materials are used for lead frame, die attach, passivation, and power metal stack, then each material can be optimized for its specific function, but adhesion between different materials becomes difficult to ensure due to different thermal expansion and surface properties
Solution Approach 1:
The adhesion promoter layer serves as a universal intermediary that interfaces with multiple different materials (lead frame, semiconductor chip, polyimide passivation). It contains multiple organic compounds that can bond to different material types, and nanoscale ceramic grains that provide mechanical interlocking, thereby ensuring adhesion across diverse material interfaces
Solution Approach 2:
The adhesion promoter is applied selectively at specific interfaces where adhesion is critical (between mold compound and lead frame, between mold compound and chip, between passivation and polyimide). This localized application optimizes adhesion at critical interfaces without requiring modification of the entire material system
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 effectively improves adhesion and moisture resistance, enhancing the reliability and longevity of SiC semiconductor devices by optimizing adhesion at multiple interfaces, suitable for high voltage applications like traction inverter circuits in battery electric vehicles or switch mode power supplies.
Implementation Method 1
at least one adhesion promoter, wherein the at least one adhesion promoter is on the uncovered surface part of the second frame surface of the lead frame and/or on the second chip surface of the semiconductor chip
Data Source
AI summary
A semiconductor device is provided, including: a lead frame, a semiconductor chip, a mold, and an adhesion promoter. The lead frame includes a first surface and a second frame surface opposite the first surface, and the chip includes a first and a second surface opposite the first surface, the first frame surface is an outer surface of the device, with the second frame surface attached to the first chip surface so that the second frame surface is partially covered by the first chip surface. An uncovered surface part of the second frame surface and the second chip side are in contact with the mold by the adhesion promoter, that is on the uncovered surface part of the second frame surface and/or on the second chip surface. The adhesion promoter enhances adhesion between the mold, and either the second frame surface or the second chip surface of the chip.