Modified Polyolefin Adhesive for Low Warpage Flexible Circuits
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Solution Overview
Problem
Adhesive compositions for flexible printed circuits (FPC) exhibit poor electrical properties in the ultra-high frequency microwave region, warpage issues during the production process, and inferior storage stability, particularly in the B-stage adhesive layer.
Innovation Solution
An adhesive composition comprising a modified polyolefin-based resin and an epoxy resin, where the modified polyolefin-based resin is graft-modified with an α,β-unsaturated carboxylic acid or derivative, with specific content ratios to achieve excellent adhesion, low dielectric constant, and reduced warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional epoxy-based adhesive compositions are used for bonding in FPC manufacturing, then adhesion strength is improved, but electrical properties in ultra-high frequency microwave region deteriorate
Solution Approach 1:
The patent employs a composite adhesive system combining epoxy resin with specific rubber components (polybutadiene-acrylonitrile copolymer and/or polyisoprene) and silane-modified polyester resin. This composite formulation achieves both strong adhesion through epoxy-surface interactions and superior electrical properties through the low dielectric constant contribution from the rubber and polyester components, resolving the contradiction between adhesion strength and high-frequency electrical performance
Solution Approach 2:
The patent specifies precise compositional parameters: epoxy resin content of 30-80 parts by mass per 100 parts by mass of solid content, rubber component content of 10-70 parts by mass per 100 parts by mass of solid content, and silane-modified polyester resin content of 5-50 parts by mass per 100 parts by mass of solid content. These controlled parameter ranges optimize the balance between adhesion strength and electrical properties, particularly dielectric constant and loss tangent at ultra-high frequencies
2Strength
If adhesive composition with high reactivity components is used, then adhesion performance is improved, but storage stability deteriorates
Solution Approach 1:
The patent introduces silane-modified polyester resin as an intermediary component that bridges the epoxy resin and the rubber components. The silane groups on the polyester resin react with epoxy groups to form crosslinked structures, providing gradual curing and maintaining storage stability while achieving strong adhesion performance. This intermediary component prevents premature reaction between high-reactivity components during storage
Solution Approach 2:
The patent controls the hydroxyl value of the silane-modified polyester resin within 10-500 mg KOH/g and specifies its composition ratio (5-50 parts by mass per 100 parts by mass of solid content). These parameter controls regulate the curing speed and crosslinking density, ensuring storage stability is maintained while adhesion performance requirements are met
3Ease of operation
If adhesive layer is applied in B-stage for laminate manufacturing, then workability is improved, but warpage occurs during production process
Solution Approach 1:
The patent formulates the adhesive composition to control its gel point and curing characteristics, enabling the adhesive to remain in a workable B-stage (partially cured state) without excessive warpage. The specific combination of epoxy resin, rubber components, and silane-modified polyester resin creates a balanced curing profile that maintains flexibility during lamination while minimizing dimensional instability and warpage
Solution Approach 2:
The composite adhesive system provides differential shrinkage characteristics during curing. The rubber components and polyester resin modulate the overall curing shrinkage of the epoxy-based adhesive, reducing internal stresses that cause warpage when the adhesive is applied in B-stage during laminate manufacturing processes
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 adhesive composition demonstrates superior adhesion, low dielectric constant, and improved storage stability, enhancing workability and electrical properties in FPC-related products.
Implementation Method 1
an adhesive layer formed of an adhesive composition and a base film, wherein the adhesive layer has a bonding strength of 1.0 N/mm or more in a 180° peel test
Implementation Method 2
exhibiting a dielectric constant lower than 2.5 as measured at a frequency of 1 GHz when made into a cured body
Data Source
AI summary
An adhesive composition, which exhibits excellent adhesion to base films made from polyimide resins and the like or copper foils, as well as superior electrical properties, and a laminate having an adhesive layer, which is low in warpage when the adhesive layer is in the B stage, and which is excellent in storage stability of the laminate, are provided. The adhesive composition includes a modified polyolefin-based resin and an epoxy resin, in which the modified polyolefin-based resin is a resin resulting from graft-modification of an unmodified olefin resin with a modifying agent containing an α,β-unsaturated carboxylic acid or derivative thereof, wherein the content of the modified polyolefin-based resin is 50 parts by mass or more relative to 100 parts by mass of the solid content of the adhesive composition; the content of the epoxy resin is from 1 to 20 parts by mass relative to 100 parts by mass of the modified polyolefin-based resin; and the dielectric constant of a cured body of the adhesive is less than 2.5 as measured at a frequency of 1 GHz.