Composite Solder Structure With Coating for Thermal Cycling Reliability
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Solution Overview
Problem
Existing semiconductor packages face challenges in maintaining mechanical and electrical reliability due to issues such as void formation and failure during thermal cycling, particularly in high-performance computing and electronic systems.
Innovation Solution
A semiconductor package design featuring a solder structure with alternating high-melting-point and low-melting-point solder materials, such as Tin-Silver-Copper and Tin-Bismuth alloys, and a protective coating layer to enhance thermal and mechanical durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-material solder structure is used, then the manufacturing process is simple, but the reliability during thermal cycling is insufficient
Solution Approach 1:
The patent employs a composite solder structure consisting of a first solder material (e.g., Sn-Ag-Cu alloy with high melting point) and a second solder material (e.g., Sn-Bi alloy with low melting point). The first solder material provides thermal stability and mechanical strength, while the second solder material fills voids and improves wetting characteristics. This composite approach resolves the contradiction by achieving enhanced thermal cycling reliability through material composition rather than structural complexity.
Solution Approach 2:
The patent applies different solder materials to different regions of the solder joint. The first solder material is positioned at the interface with the substrate for thermal stability, while the second solder material is positioned at the interface with the semiconductor chip for improved wetting and void filling. This local differentiation of material properties resolves the contradiction by optimizing each region's function without requiring complex overall structure.
2Reliability
If solder paste is applied directly without additional coating, then the manufacturing process is simple, but void formation occurs during reflow
Solution Approach 1:
The patent applies a low-melting-point solder material coating layer to the external surface of the solder structure before the reflow process. This preliminary coating action ensures that during reflow, the low-melting-point material remains liquid longer, actively filling voids and improving wetting between the solder and substrate. This preliminary protective measure resolves the contradiction by preventing void formation through advance preparation rather than complex manufacturing controls.
3Stability of the object's composition
If high-melting-point solder material is used throughout, then thermal stability is improved, but wetting performance and void filling are insufficient
Solution Approach 1:
The patent positions the low-melting-point solder material specifically at regions requiring improved wetting and void filling, such as the interface with the semiconductor chip and within void spaces. The high-melting-point solder material is positioned at the substrate interface for thermal stability. This local differentiation resolves the contradiction by assigning each material's optimal properties to the regions where they are most needed, achieving both thermal stability and manufacturing precision.
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 design increases solder joint performance, reduces defects like tearing or delamination, and enhances reliability in thermal cycling, making it suitable for integration on substrates like PCBs and ceramic boards for high-performance applications.
Implementation Method 1
A coating layer covers at least a portion of an external surface of the solder structure
Implementation Method 2
The solder structure can be created using a reflow process, wherein connection bumps on the ball pads of the PCB are reflowed along with solder paste applied to the bonding pads of the PCB
Data Source
AI summary
A semiconductor device includes a lower substrate. A first pad is disposed on the lower substrate. An upper substrate is disposed on the lower substrate. A second pad is disposed in a lower portion of the upper substrate. A solder structure is disposed between the first pad and the second pad. A coating layer covers at least a portion of an external surface of the solder structure. The solder structure includes a first portion disposed on a first surface that is in contact with the first pad. The first portion has a first solder pattern and a second solder pattern. The second solder pattern surrounds the first solder pattern.