Epoxy Resin for PCBs with Low Thermal Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current epoxy resins used in printed circuit boards exhibit significant changes in heat resistance and thermal expansion properties after thermal history, leading to connection defects due to high thermal contraction and increased reflow temperatures, which are not adequately addressed by existing naphthol novolac type epoxy resins.
Innovation Solution
A curable resin composition comprising an epoxy resin obtained through polyglycidyl etherification of a reaction product from ortho-cresol, β-naphthol, and formaldehyde, containing specific dimer, trifunctional, and tetrafunctional compounds at predetermined ratios, which enhances reactivity and cross-linking density, resulting in a cured product with low thermal expansion and minimal heat resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If naphthol novolac type epoxy resin is used to reduce thermal expansion, then the coefficient of thermal expansion is improved, but the heat resistance changes significantly after thermal history
Solution Approach 1:
The patent modifies the chemical structure parameters of the epoxy resin by introducing specific naphthol compounds with controlled substitution patterns and molecular weights. This changes the resin's thermal properties to achieve both low thermal expansion and stable heat resistance after reflow processing.
Solution Approach 2:
The patent creates a composite epoxy resin system by combining naphthol novolac type epoxy resin with specific curing agents and additives. This composite approach allows optimization of multiple properties simultaneously, achieving low thermal expansion while maintaining heat resistance stability.
2Reliability
If reflow temperature is increased for lead-free soldering, then soldering quality is improved, but the change in heat resistance of insulating material increases
Solution Approach 1:
The patent adjusts the glass transition temperature and cross-linking density parameters of the epoxy resin to withstand higher reflow temperatures. The modified resin maintains its structural stability and electrical properties even after exposure to elevated temperatures required for lead-free soldering processes.
3Productivity
If wiring pitch is reduced to increase density, then device performance is improved, but thermal contraction stress on solder connections increases
Solution Approach 1:
The patent utilizes materials with matched thermal expansion coefficients, specifically designing the epoxy resin to have low thermal expansion that matches the copper traces and solder joints. This reduces differential thermal stress during temperature cycling, preventing connection defects even in high-density configurations with reduced wiring pitch.
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 proposed solution provides a printed circuit board with a small change in heat resistance and excellent low thermal expansion properties, effectively reducing connection defects and improving reliability under thermal stress.
Implementation Method 1
an epoxy resin which is obtained by polyglycidyl etherification of a reaction product formed from ortho-cresol, a β-naphthol compound, and formaldehyde
Implementation Method 2
a large stress is generated in the solder balls connecting the circuit board and a semiconductor device due to thermal contraction of the circuit board
Implementation Method 3
a curable resin composition which comprises as a necessary component, the epoxy resin and a curing agent
Data Source
AI summary
The present invention provides a curable resin composition, a cured product of which has a small change in heat resistance after receiving a thermal history and a low thermal expansion property; a cured product of the curable resin composition; a printed circuit board having a small change in heat resistance; and an epoxy resin which imparts the characteristics described above. The epoxy resin is an epoxy resin which is obtained by polyglycidyl etherification of a reaction product formed from ortho-cresol, a β-naphthol compound, and formaldehyde and which includes as a necessary component, a dimer (x2, formula (1)), a trifunctional compound (x3, formula (2)), and a tetrafunctional compound (x4, formula (3)). The total content of those components is 65% or more in terms of the area rate in GPC measurement.