Silver Particle Bonding Layer for Semiconductor Thermal Resistance
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Solution Overview
Problem
Conventional lead-free solders, such as Sn—Ag and Sn—Sb, face challenges with low thermal resistance and reliability under harsh mounting conditions, including increased reflows and high reflow temperatures, and silver nano-particle bonding materials have inconsistent bonding strength due to film thickness and particle state.
Innovation Solution
A method involving a semiconductor chip with a first metal film, such as a nickel-phosphorus alloy, and a second metal film with silver or gold particles, bonded via a silver particle bonding layer, which is sintered at elevated temperatures to enhance bonding strength and thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lead-free solders (Sn-Ag, Sn-Sb) are used for bonding, then the bonding process is simple, but the thermal resistance is high and reliability is poor under harsh mounting conditions
Solution Approach 1:
The patent uses a composite bonding structure consisting of a solder alloy layer (Sn-Ag-Cu or Sn-Sb-Cu) combined with a silver particle layer. This composite structure leverages the low melting point and good wetting properties of solder alloy while incorporating silver particles to enhance thermal conductivity and reduce thermal resistance, thereby improving both reliability and thermal performance under harsh mounting conditions including reflow temperatures up to 260°C
Solution Approach 2:
The patent modifies the composition parameters of the bonding material by adding copper (0.5-3.0 wt%) to the Sn-Ag or Sn-Sb base alloy, and controls the particle size and concentration of silver particles (0.1-10 μm, 1-50 wt%). These parameter changes optimize the balance between bonding strength, thermal resistance, and reliability, enabling the bonding material to withstand increased reflows and high reflow temperatures while maintaining low thermal resistance
2Temperature
If silver nano-particle bonding materials are used, then thermal conductivity is improved, but bonding strength becomes inconsistent due to film thickness and particle state variations
Solution Approach 1:
The patent establishes specific parameter ranges to control silver particle characteristics: particle size (0.1-10 μm), concentration (1-50 wt%), and film thickness. By precisely controlling these parameters, the patent ensures consistent bonding strength while maintaining high thermal conductivity. The particle size distribution and concentration are optimized to prevent aggregation and ensure uniform film formation, resolving the inconsistency issue
Solution Approach 2:
The patent creates a composite structure where silver particles are embedded in a solder alloy matrix. This composite approach combines the high thermal conductivity of silver particles with the good bonding properties of solder alloy, achieving both high thermal conductivity and consistent bonding strength. The solder alloy matrix provides a continuous phase that ensures uniform distribution of silver particles and consistent bonding characteristics
3Strength
If the second metal film thickness is increased to improve bonding strength, then bonding strength improves, but the film becomes too thick and may cause other issues
Solution Approach 1:
The patent optimizes the thickness of the second metal film (silver or gold layer) to a specific range that provides sufficient bonding strength without excessive thickness. This parameter optimization ensures adequate bonding performance while avoiding potential issues associated with overly thick films such as increased stress, longer processing times, and higher material costs
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 results in electronic components with improved bonding strength, thermal resistance, and heat radiation properties, surpassing the limitations of conventional lead-free solders and silver nano-particle bonding materials.
Implementation Method 1
a silver particle bonding layer, which is sintered at elevated temperatures to enhance bonding strength
Implementation Method 2
a step of bringing the plating receiving material into contact with an electroless metal plating solution from which Au ions have been removed
Data Source
AI summary
Plating pre-processing is carried out before carrying out a plating process on the surface of a conducting section provided on a semiconductor wafer. A first metal film is formed on the surface of the conducting section by NiP alloy plating process. A second metal film is formed on the surface of the first metal film by immersion Ag plating process. The semiconductor wafer is diced and cut into semiconductor chips. A conductive composition containing Ag particles is applied to the surface of the second metal film which is on the front surface of the semiconductor chip. A bonding layer containing Ag particles is formed by sintering the conductive composition through heating. A metal plate is then bonded to the surface of the second metal film via the bonding layer containing Ag particles. The electronic component has high bonding strength, excellent thermal resistance and heat radiation properties.