High Temperature Solder Paste Flux Stability
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Solution Overview
Problem
Legacy solder pastes deteriorate and suffer from flux/powder separation when used on pre-heated substrates during high-temperature SGA processing, especially with finer powder pitches less than 0.3 mm, leading to yield loss and non-uniform bump deposition.
Innovation Solution
A water-soluble solder paste with a non-rosin based flux containing a non-polymer based thixotropic agent, which maintains stability and viscosity at high temperatures, preventing flux/powder separation and ensuring uniform deposition of finer solder bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-heating is applied to flatten substrates for uniform SGA bump deposition, then manufacturing precision is improved, but solder paste reliability deteriorates due to flux/powder separation and cracking
Solution Approach 1:
The patent modifies the chemical composition parameters of the flux by incorporating specific additives including polyethylene glycol (PEG), carboxymethyl cellulose (CMC), and glycerin. These compositional changes enable the flux to maintain its binding properties at elevated temperatures, allowing the solder paste to withstand pre-heating temperatures of 60-100°C without flux/powder separation while still achieving uniform bump deposition
2Manufacturing precision
If finer powder is used for smaller pitch SGA bumps, then manufacturing precision is improved, but solder paste reliability worsens due to increased deterioration and flux/powder separation
Solution Approach 1:
The patent creates a composite flux system combining multiple functional components: PEG provides high-temperature stability, CMC offers binding and suspension properties, and glycerin contributes to viscosity control and wetting. This composite material approach allows the flux to effectively bind and suspend finer powder particles at smaller pitches while maintaining stability during pre-heating, preventing flux/powder separation even with sub-0.3mm pitch requirements
3Ease of manufacture
If legacy flux formulations are used for cost-effective SGA processing, then manufacturing cost is reduced, but manufacturing precision deteriorates due to flux deterioration and non-uniform deposition
Solution Approach 1:
The patent modifies the chemical composition parameters of the flux by incorporating specific additives including polyethylene glycol (PEG), carboxymethyl cellulose (CMC), and glycerin. These compositional changes enable the flux to maintain its binding properties at elevated temperatures, allowing the solder paste to withstand pre-heating temperatures of 60-100°C without flux/powder separation while still achieving uniform bump deposition
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 solder paste sustains high temperatures without degradation, maintaining viscosity and preventing flux/powder separation, allowing for successful formation of uniform solder joints with reduced residue, even on pre-heated substrates, enhancing the reliability and yield of SGA processing.
Implementation Method 1
a non-rosin based flux with a non-polymer based thixotropic agent
Data Source
AI summary
Embodiments herein may relate to a solder paste. The solder paste may include a solder powder and a flux. In embodiments, the flux may be a non-rosin based flux. The flux may further include a thixotropic agent (TA) that may be a non-polymer based TA. Other embodiments may be described and/or claimed.