Patterned Leadframe Finishing for Encapsulation Adhesion
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Solution Overview
Problem
Current manufacturing processes of semiconductor devices face issues with delamination of the encapsulation from the leadframe due to reduced adhesion caused by silver finishing layers, leading to potential wire breakage and cracking of the die attach material.
Innovation Solution
A patterned finishing layer is applied to cover selected regions of the substrate where electrical components are attached, and the finishing layer is removed from uncovered regions via laser ablation to prevent contact between the encapsulation and the finishing layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silver finishing layer is provided on the mounting surface of the leadframe to improve die attachment and wire bonding reliability, then the reliability of die attachment and wire bonding is improved, but the adhesion between the leadframe and the encapsulation is reduced
Solution Approach 1:
The patent applies a silver finishing layer selectively only in specific regions where die attachment and wire bonding are required, rather than providing a complete coating on the entire leadframe surface. This localized application ensures that the silver layer enhances bonding reliability at critical interfaces while leaving other areas free of the silver layer to maintain proper adhesion with the encapsulation material.
Solution Approach 2:
The leadframe surface is divided into multiple functional zones: regions requiring silver finishing for electrical bonding and regions requiring direct encapsulation contact for mechanical adhesion. The silver finishing layer is applied segmentally to specific mounting surfaces and lead regions, creating distinct functional areas that resolve the contradiction between bonding reliability and encapsulation adhesion.
2Ease of manufacture
If a complete silver finishing layer is applied on the leadframe surface, then die attachment and wire bonding are facilitated, but delamination of the encapsulation occurs
Solution Approach 1:
Instead of applying a uniform silver finishing layer across the entire leadframe surface, the patent implements selective regional coating only where electrical bonding is required. This local quality approach allows die attachment and wire bonding to be facilitated on coated surfaces while preventing encapsulation delamination on uncoated surfaces.
Solution Approach 2:
The harmful effect of the silver finishing layer (reduced encapsulation adhesion) is eliminated by extracting or removing the coating from regions where it is not needed for electrical bonding. The silver layer is taken out from areas that will be in contact with the encapsulation, leaving only the necessary functional areas coated.
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 approach reduces the risk of delamination, maintaining the integrity of the encapsulation and ensuring reliable electrical connections by eliminating contact between the encapsulation and the finishing layer.
Implementation Method 1
the finishing layer may be removed from regions of the surface of the leadframe that are not covered by the electrical components previously attached via laser ablation
Data Source
AI summary
Surface finishing material is provided in a layer at a surface of an electrically conductive substrate. The surface includes complementary adjacent first and second surface regions. A semiconductor die is arranged at the first surface region. The surface finishing material is selectively applied at the first surface region or is selectively removed from at least a portion of the second surface region. An electrically insulating encapsulation is molded onto the electrically conductive substrate and semiconductor die arranged at the first surface region. The electrically insulating encapsulation encapsulates the semiconductor die and contacts the surface of the electrically conductive substrate at the portion of the second surface region of the electrically conductive substrate where the surface finishing material is not present.