Heat Curable Resin Composition Void Removal
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Solution Overview
Problem
Conventional surface mount techniques for electronic components on circuit boards face issues such as insufficient flux washing, void formation due to trapped air, and reduced reliability due to narrow solder gaps and high reflow temperatures, which hinder effective removal of voids by vacuum operation.
Innovation Solution
A heat curable resin composition with a controlled reaction ratio of epoxy groups at 40% or less after reflow soldering, comprising a liquid epoxy resin, hemiacetal ester, curing agents like cyanoguanidine and melamine, and spherical fillers, allowing void removal through heating and vacuum operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the underfill material is completely cured after reflow due to high reflow temperature, then the curing is complete, but a large number of voids are produced by water generated during removal of oxide films
Solution Approach 1:
The patent applies preliminary action by performing vacuum operation and heating at temperatures below the curing temperature immediately after reflow soldering, before the resin is completely cured. This preliminary defoaming removes water and air bubbles generated during oxide film removal, preventing void formation while the resin is still in a semi-cured state that allows void removal.
2Reliability
If the underfill material is applied in advance and cured with air being trapped, then the material is cured, but a large number of voids are produced
Solution Approach 1:
The patent performs preliminary action by conducting vacuum operation and heating at temperatures below the curing temperature before final curing. This preliminary step removes air bubbles and water that become trapped during the curing process, allowing the resin to be cured in a void-free state.
3Ease of operation
If the heat curable resin composition is heated at a temperature lower than the curing temperature after reflow soldering, then the resin should be softened for void removal, but the resin is hardly softened making void removal difficult
Solution Approach 1:
The patent applies parameter changes by carefully controlling the heating temperature to be below the curing temperature but sufficient to soften the resin for void removal. The specific temperature range and heating duration are optimized to achieve the right balance between resin softness for void removal and prevention of complete curing that would trap voids.
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 composition effectively removes voids by controlling the epoxy reaction ratio, improving the reliability of electronic connections and mechanical joints between the circuit board and electronic components.
Implementation Method 1
a hemiacetal ester synthesized from monocarboxylic acid and polyvinyl ether
Implementation Method 2
heat curing the applied resin
Implementation Method 3
heat curable resin composition
Implementation Method 4
vacuum operation
Data Source
AI summary
A heat curable resin composition which allows voids to be removed by heating and vacuum operation after reflow soldering, and a circuit board with an electronic component mounted thereon are provided. The heat curable resin composition of the present embodiment includes a liquid epoxy resin, a hemiacetal ester derived from monocarboxylic acid and polyvinyl ether, a curing agent, and a filler.