Semiconductor Interposer CTE Matching for Thermal Stress Reduction
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Solution Overview
Problem
Semiconductor packages experience high failure rates due to thermal expansion discrepancies between plastic or ceramic materials and semiconductor materials, leading to solder joint cracks and delamination, especially under temperature and humidity variations.
Innovation Solution
Using semiconductor interposers instead of plastic or ceramic materials, with conductive lines and non-reflow metal studs, and employing flip-chip assembly to minimize thermal stresses and electrical resistances, while allowing for active electronic devices and integrated circuits on the interposer surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plastic or ceramic materials are used for interposers, then manufacturing is easier and cost is lower, but thermal expansion discrepancy causes solder joint cracks and delamination
Solution Approach 1:
The patent changes the material parameter (coefficient of thermal expansion) by selecting interposer materials whose CTE matches that of the semiconductor chip (e.g., silicon interposer with CTE ~2.6 ppm/°C matching silicon chip, versus plastic with CTE 70-100 ppm/°C). This parameter matching eliminates thermal stress during temperature cycling, preventing solder joint cracks and delamination while maintaining manufacturing feasibility through established semiconductor fabrication processes.
Solution Approach 2:
The patent employs composite material structures where the interposer is made of semiconductor material (silicon) rather than traditional plastic or ceramic. This composite approach integrates the interposer with the chip material system, creating a thermally compatible assembly that resists delamination and solder joint failure under thermal and humidity stress.
2Area of stationary object
If vertically stacked chips are assembled to reduce board area, then device footprint is reduced, but reliability failure rates increase due to thermal stresses
Solution Approach 1:
The patent applies CTE-matching material selection in the vertical stacking configuration, where each interposer layer is made of material compatible with its adjacent chips. This parameter control ensures that thermally-induced stresses are minimized across all interfaces in the stacked assembly, maintaining high reliability while achieving compact board-area reduction through vertical integration.
3Ease of manufacture
If wire bonding techniques are used for chip assembly, then manufacturing is simpler, but electrical resistance and inductance increase reducing speed and power capabilities
Solution Approach 1:
The patent replaces the mechanical wire bonding process with a direct flip-chip soldering method. Instead of using flexible wires to connect chip pads to substrate, the chip is flipped and soldered directly to the interposer, creating rigid, short-distance electrical connections. This substitution eliminates the mechanical wire structure, reducing both inductance and resistance, thereby improving signal speed and power delivery while maintaining manufacturing capability through automated pick-and-place and reflow soldering processes.
4Reliability
If semiconductor interposers are used instead of plastic materials, then thermal expansion matching improves reliability, but manufacturing complexity increases
Solution Approach 1:
The patent makes the interposer multi-functional by using semiconductor material that serves both as a mechanical support structure and as an electrical interconnection medium. The interposer incorporates conductive traces, vias, and contact pads integrated into the semiconductor substrate, eliminating the need for separate wiring layers and simplifying the overall structure. This universal approach reduces manufacturing complexity despite the advanced material, as it consolidates multiple functions into a single component fabricated using standard semiconductor processes.
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 thermo-mechanical stresses, enhances reliability, and enables smaller device dimensions with improved speed and power capabilities by matching the thermal expansion coefficients of semiconductor materials, thereby minimizing solder joint failures and delamination.
Implementation Method 1
the material characteristics, especially the wide variation of the coefficients of thermal expansion (CTE) between plastic or ceramic materials and semiconductor materials
Data Source
AI summary
A semiconductor system (200) of one or more semiconductor interposers (201) with a certain dimension (210), conductive vias (212) extending from the first to the second surface, with terminals and attached non-reflow metal studs (215) at the ends of the vias. A semiconducting interposer surface may include discrete electronic components or an integrated circuit. One or more semiconductor chips (202, 203) have a dimension (220, 230) narrower than the interposer dimension, and an active surface with terminals and non-reflow metal studs (224, 234). One chip is flip-attached to the first interposer surface, and another chip to the second interposer surface, so that the interposer dimension projects over the chip dimension. An insulating substrate (204) has terminals and reflow bodies (242) to connect to the studs of the projecting interposer.