Dielectric Carrier Wettability Gradient for Bond Line Control
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Solution Overview
Problem
High power electronic devices face challenges in achieving uniform bond lines due to thin and uneven bondline thicknesses, leading to cracking and debonding from substrates under high power switching and thermal cycling, which compromises dielectric breakdown voltage and thermal conductivity.
Innovation Solution
A bonding system with regions of varying wettability on the substrate, where a first area with lower wettability and a second area with higher wettability guide the adhesive material to form a uniform bond line, using protrusions or etched cavities to control the spread and ensure consistent thickness, enhancing thermal conductivity and dielectric strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a uniform bond line is achieved through conventional bonding methods, then the die can be attached to the substrate, but the bond line becomes thin and uneven leading to cracking and debonding under thermal cycling
Solution Approach 1:
The substrate surface is divided into regions with different wettabilities - a central first region with lower wettability and a surrounding second region with higher wettability. This local quality differentiation controls adhesive flow to achieve uniform bond line thickness while maintaining reliability under thermal cycling.
Solution Approach 2:
The wettability parameter of the substrate surface is changed across different regions to control adhesive material behavior. By modifying surface energy characteristics locally, the system achieves precise control over bond line formation without requiring additional mechanical constraints.
2Manufacturing precision
If protrusions are added to control adhesive flow, then bond line uniformity improves, but device complexity increases
Solution Approach 1:
Protrusions are strategically placed only at the periphery of the substrate in the second region, rather than uniformly across the entire surface. This localized approach provides effective adhesive flow control while minimizing additional structural complexity.
Solution Approach 2:
The substrate surface is segmented into functional zones - a central bonding area and a peripheral control area with protrusions. This segmentation allows the protrusions to serve as flow stops without interfering with the central bond formation process.
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 achieves a 38% reduction in inelastic creep strain and triples the fatigue life of the bond, maintaining high dielectric breakdown voltage and thermal conductivity, while reducing the need for additional wiring and enhancing package reliability and cost-effectiveness.
Implementation Method 1
A second area that at least partially surrounds the first area has a surface with a second wettability that is greater than the first wettability. During bonding, an adhesive material bonding a chip to the substrate spreads among the first area by a downward force placed on the chip. Due to the difference in wettability, the adhesive material then spreads among the second area by a wetting force generated by the greater second wettability of the second area surface causing the chip to be drawn down until reaching a predetermined position.
Data Source
AI summary
A system for bonding a die to a high power dielectric carrier such as a ceramic dielectric core with double-sided conductive layers is described. In the system, the upper conductive layer has a first area whose surface has a first wettability. A second area that at least partially surrounds the first area has a surface with a second wettability that is greater than the first wettability. During bonding, an adhesive material bonding a chip to the substrate spreads among the first area by a downward force placed on the chip. Due to the difference in wettability, the adhesive material then spreads among the second area by a wetting force generated by the greater second wettability of the second area surface causing the chip to be drawn down until reaching a predetermined position. The predetermined position can be determined by substrate protrusions or substrate cavities.