Polycyclic Resin Varnish for Low Thermal Expansion PCBs
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Solution Overview
Problem
Conventional printed wiring boards face issues with warpage and thermal expansion due to differences in thermal expansion coefficients between resin and semiconductor components, leading to stress on solder balls and potential cracking, especially in high-density packaging applications.
Innovation Solution
A varnish is developed through reactions between compounds with amino or phenolic hydroxyl groups and resins with polycyclic structures, improving solubility and storage stability, which is then used to produce prepregs, resin-coated films, metal-foil-clad laminates, and printed wiring boards with reduced thermal expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epoxy resin is used as the main component of the resin composition, then insulating property and heat resistance are improved, but thermal expansion coefficient increases
Solution Approach 1:
The patent uses a composite resin system combining epoxy resin with phenolic resin and polyimide resin. The epoxy resin provides insulating properties and heat resistance, while the phenolic and polyimide resins contribute low thermal expansion coefficients. This composite approach allows the wiring board to achieve both high reliability and low thermal expansion.
Solution Approach 2:
The patent modifies the resin composition by controlling the weight ratios of different resin components. Specifically, it specifies that phenolic resin content is 10-60 wt% and polyimide resin content is 5-40 wt% of the total resin composition. By adjusting these parameters, the patent optimizes the balance between insulating properties, heat resistance, and thermal expansion coefficient.
2Object-affected harmful factors
If inorganic filler is added to reduce thermal expansion coefficient, then thermal expansion is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of adding inorganic fillers, the patent changes the chemical composition parameters of the organic resin system. It specifies precise weight ratios of epoxy resin (30-80 wt%), phenolic resin (10-60 wt%), and polyimide resin (5-40 wt%). This parameter optimization allows achieving low thermal expansion coefficient through molecular structure design rather than physical filler addition, thereby avoiding increased manufacturing complexity.
3Productivity
If high-density wiring is implemented through stacking thin layers, then wiring density is improved, but warpage and stress concentration increase
Solution Approach 1:
The patent employs a composite resin system with phenolic resin and polyimide resin incorporated into the epoxy matrix. These resins have inherently low thermal expansion coefficients that closely match semiconductor devices. This material composition enables the wiring board to maintain dimensional stability and resist warpage even when constructed with multiple thin stacked layers for high-density wiring.
Solution Approach 2:
The patent applies the low thermal expansion resin composition specifically to the insulating films and adhesive layers in the wiring board structure. By localizing this specialized material composition in critical areas where thermal expansion differential causes warpage, the patent effectively controls deformation while maintaining overall high-density wiring capability.
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 varnish exhibits high storage stability and improved workability, resulting in printed wiring boards with reduced warpage and thermal expansion, enhancing the reliability of high-density packaging by preventing cracking and ensuring consistent performance.
Implementation Method 1
A varnish is developed through reactions between compounds with amino or phenolic hydroxyl groups and resins with polycyclic structures
Implementation Method 2
the wiring board expands due to heat; warpage occurs in the wiring board due to the difference in thermal expansion coefficient between the resin forming the wiring board and the electronic component
Data Source
AI summary
The invention provides a varnish produced through reaction between a compound having an amino group and a resin having a functional group capable of reacting with an amino group, and having a polycyclic structure, wherein a portion of a plurality of the functional group of the resin is caused to react with the amino group of the compound in a solvent, and also a varnish produced through reaction between a compound having a phenolic hydroxyl group and a resin having a functional group capable of reacting with a phenolic hydroxyl group, and having a polycyclic structure, wherein a portion of a plurality of the functional group of the resin is caused to react with the phenolic hydroxyl group of the compound in the solvent. The invention also provides a prepreg, a resin-coated film, a metal-foil-clad laminate, and a printed wiring board produced by use of any of the varnishes.