Layered Lead-Frame Substrate for CTE Matching and Heat Conduction
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Solution Overview
Problem
Conventional lead-frame substrates experience decreased thermal performance due to mismatched coefficients of thermal expansion (CTE) between semiconductor materials and metal lead frames, leading to mechanical stress and potential failure under temperature variations.
Innovation Solution
A layered lead-frame substrate configuration with alternating layers of materials having different CTEs, connected by vias filled with high thermal conductivity materials, allowing for enhanced thermal and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lead-frame substrate is made of metal to provide electrical conductivity, then electrical performance is improved, but CTE mismatch with semiconductor material increases causing mechanical stress and potential failure
Solution Approach 1:
The lead-frame substrate uses a composite structure with a metal layer (first material) providing electrical conductivity and a polymer layer (second material) providing CTE matching with the semiconductor die. This composite configuration allows the substrate to simultaneously achieve good electrical performance and thermal expansion compatibility, preventing mechanical stress and potential failure during temperature variations.
2Reliability
If a lead-frame substrate is cladded with metal to match CTE of semiconductor material, then CTE matching is improved, but thermal conductivity significantly decreases
Solution Approach 1:
The substrate employs local quality differentiation where the metal layer provides high thermal conductivity in regions requiring heat dissipation, while the polymer layer provides CTE matching in regions requiring dimensional stability. This localized functional assignment allows the substrate to simultaneously achieve good thermal performance and CTE compatibility without compromising either property throughout the entire structure.
3Reliability
If a lead-frame substrate uses a central material cladded with metal, then CTE matching is improved, but device complexity increases
Solution Approach 1:
The invention extracts the CTE matching function from the metal cladding and assigns it to a dedicated polymer layer, while the metal layer focuses solely on providing electrical and thermal conductivity. This functional separation simplifies the overall design by allowing each layer to be optimized independently for its specific purpose, reducing the complexity of achieving multiple properties simultaneously in a single material.
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 configuration maintains CTE matching while significantly improving thermal and electrical performance by facilitating efficient heat conduction through the substrate.
Implementation Method 1
at least one via thermally connecting the first layer with the third layer
Implementation Method 2
their coefficient of thermal expansion, CTE, typically lies lower than that of metal material of which the lead frame is formed. When two materials with different coefficients of thermal expansion are bonded or assembled together, their expansion or contraction rates may not match.
Data Source
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AI summary
A substrate, in particular a lead-frame substrate used in a semiconductor package for mounting a semiconductor die element is proposed, wherein the substrate is composed of a layered configuration comprising at least: a first layer of a first material, comprising a first surface side a second surface side opposite to the first surface side, the first surface side arranged to receive a semiconductor die element; a second layer of a second material having a coefficient of thermal expansion, CTE, lower than the CTE of the first material of the first layer, comprising a first surface side and a second surface side opposite to the first surface side, the first surface side of the second layer arranged to be in contact with the second surface side of the first layer; a third layer of a third material having a CTE higher than the CTE of the second layer, comprising a first surface side and a second surface side opposite to the first surface side, the first surface side of the third layer arranged to be in contact with the second surface side of the second layer; and at least one via thermally connecting the first layer with the third layer.