Solder Paste Flux Composition to Resist Electromigration Shorts
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Solution Overview
Problem
Solder pastes used in electronic circuit manufacturing tend to exhibit electromigration and dendrite formation, leading to unwanted shorts, particularly as components miniaturize and proximity increases, necessitating a solution to reduce or eliminate these issues.
Innovation Solution
A solder paste with a specially composed flux containing a combination of at least two modified natural resins differing in molecular weight, low-molecular carboxylic acid, and amine, which reduces the tendency for electromigration and dendrite formation, comprising 85-92% tin-based solder and 8-15% flux with specific molecular weight distribution and composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flux compositions are used in solder paste, then good wettability and soldering performance are achieved, but electromigration and dendrite formation occur leading to short circuits
Solution Approach 1:
The patent modifies the chemical composition parameters of the flux by incorporating specific natural resins (rosin and its derivatives) in controlled proportions, along with carboxylic acids and amines. This chemical parameter change transforms the flux properties to reduce electromigration and dendrite formation while maintaining soldering performance
Solution Approach 2:
The invention uses a composite flux system combining multiple components: natural resins (rosin, hydrogenated rosin, modified rosin), carboxylic acids, and amines. This composite material approach creates synergistic effects that simultaneously achieve good wettability and reduced electrical instability, resolving the contradiction between soldering quality and long-term electrical reliability
2Productivity
If component miniaturization is pursued to increase integration density, then productivity and compactness improve, but the proximity of components increases the risk of shorts from electromigration and dendrites
Solution Approach 1:
By changing the chemical parameters of the solder paste flux to include specific ratios of natural resins, carboxylic acids, and amines, the invention reduces electromigration and dendrite formation. This enables safer miniaturization by maintaining electrical insulation even when components are placed in closer proximity, thus supporting higher integration density without sacrificing reliability
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 significantly reduces short circuits in electronic modules by minimizing electromigration and dendrite formation, ensuring stable electrical insulation between components.
Implementation Method 1
the fluxes, which, among other things, serve to dissolve the oxide layer on the surfaces of the solder powder, of the component, and of the substrate
Implementation Method 2
The solder paste is heated to melt the solder in the paste by a reflow process, thereby forming the contact between the electronic component and the substrate
Data Source
AI summary
Solder paste consisting of 85 to 92% by weight of a tin-based solder and 8 to 15% by weight of a flux, wherein the flux comprisesi) 30 to 50% by weight, based on its total weight, of a combination of at least two optionally modified natural resins,ii) 5 to 20% by weight, based on its total weight, of at least one low-molecular carboxylic acid; andiii) 0.4 to 10% by weight, based on its total weight, of at least one amine, andwherein the combination of the optionally modified natural resins has an integral molecular weight distribution of 45 to 70% by area in the molecular weight range of 150 to 550 and of 30 to 55% by area in the molecular weight range of >550 to 10,000 in the combined GPC.