Solder Paste Composition for Long-Term Viscosity Stability
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Solution Overview
Problem
The storage stability of solder paste is compromised due to the reactive nature of the activator in the flux, leading to increased viscosity over time, which affects printing performance on miniaturized electronic components.
Innovation Solution
Incorporating a predetermined amount of zirconium oxide powder into the solder paste to suppress the redox and acid-base reactions that cause viscosity increase, maintaining the oxide film on the solder powder and preventing thickening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a highly active activator is used to remove oxide film and ensure wettability, then wettability is improved, but viscosity increases over time due to reaction with solder particles
Solution Approach 1:
Zirconium oxide powder acts as an intermediary substance that mediates between the highly active activator and solder particles. It suppresses the direct redox reaction between the activator and solder, preventing excessive oxide film removal and subsequent viscosity increase, while still allowing adequate wettability to occur.
Solution Approach 2:
The invention changes the physical-chemical parameters of the solder paste system by introducing zirconium oxide powder with specific properties (particle size 0.1-10 μm, specific surface area 0.1-10 m²/g). This parameter change suppresses the reaction rate between activator and solder particles, stabilizing viscosity over time while maintaining functional performance.
2Reliability
If the oxide film on solder powder is made thin to improve wettability, then wettability is enhanced, but viscosity increases due to generation of organic acid Sn salt
Solution Approach 1:
Zirconium oxide powder serves as a protective intermediary that controls the interaction between activator and solder particles. It prevents excessive thinning of the oxide film by suppressing redox reactions, thereby reducing the generation of organic acid Sn salt that causes viscosity increase.
3Stability of the object's composition
If zirconium oxide powder is added to suppress viscosity increase, then storage stability is improved, but the composition complexity increases
Solution Approach 1:
The invention manages composition complexity by carefully controlling the parameters of zirconium oxide powder addition (0.01-5 wt% content, specific particle size range, specific surface area). This controlled parameter approach achieves viscosity stabilization without excessive complexity in the overall composition.
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 addition of zirconium oxide effectively stabilizes the viscosity of the solder paste over time, ensuring consistent printing performance and extending storage periods without altering the flux composition.
Implementation Method 1
it was found that the SnO 2 film thickness on the surface of the solder powder was reduced by the oxidation-reduction reaction in the solder powder flux
Implementation Method 2
the oxide film becomes thin due to an acid-base reaction with the activator
Implementation Method 3
the addition of zirconium oxide effectively stabilizes the viscosity of the solder paste over time
Data Source
Figure 1~2
AI summary
Provided is a solder paste which uses a conventional flux, and for which long-term preservation is made possible and an easy preservation method can be realized by suppressing changes in the viscosity of the paste over time. This solder paste is provided with a solder powder, a zirconium oxide powder, and a flux, and changes in the viscosity of the paste over time are suppressed.