Resin Composition for Adhesive Sheets in Printed Wiring Boards
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Solution Overview
Problem
Conventional adhesives for printed wiring boards face challenges with adhesiveness to various plastic films and metals at high temperatures and humidity, sheet life stability, and processing suitability, particularly in high-temperature and high-humidity environments, and exhibit insufficient solder resistance and flexibility.
Innovation Solution
A resin composition comprising a polyurethane resin with specific molecular weight and acid value, a polyester resin with a low glass transition temperature, an epoxy resin containing a nitrogen atom, and an epoxy resin with a dicyclopentadiene skeleton, blended in specific ratios to enhance adhesiveness, heat resistance, and processing suitability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the glass transition temperature of the polyurethane resin is raised to improve adhesiveness and sheet life at high temperature, then adhesiveness at high temperature is improved, but flexibility of the adhesive layer is reduced, causing cracking or exfoliation during processing
Solution Approach 1:
The invention optimizes the glass transition temperature parameter of the polyurethane resin to fall within a specific range (−50°C to 100°C), rather than raising it indefinitely. This parameter optimization balances high-temperature adhesiveness with processing flexibility, preventing cracking and exfoliation during cutting and peeling operations.
Solution Approach 2:
The invention uses a composite adhesive system comprising polyurethane resin combined with polyester resin and epoxy resin. This composite formulation achieves high-temperature adhesiveness through the synergistic effects of multiple resins, allowing the polyurethane component to maintain lower glass transition temperature for flexibility while still providing excellent high-temperature bonding performance.
2Reliability
If conventional epoxy/acrylic butadiene-based adhesive or epoxy/polyvinyl butyral-based adhesive is used, then basic adhesiveness is provided, but adhesiveness at high temperature and high humidity is insufficient
Solution Approach 1:
The invention employs a composite adhesive system combining polyurethane resin, polyester resin, and epoxy resin. This multi-resin composition provides broad adhesiveness to various materials including plastic films, metals, and glass epoxy, while the specific combination ensures superior performance at high temperature and high humidity conditions that conventional single-resin adhesives cannot achieve.
Solution Approach 2:
The invention modifies the chemical composition parameters by incorporating polyurethane resin with specific glass transition temperature range and acid value, combined with polyester resin and epoxy resin in optimized ratios. These parameter changes enable the adhesive to maintain stability and adhesiveness across diverse materials and harsh environmental conditions.
3Ease of operation
If polyester resin is blended to improve processing suitability at room temperature, then flexibility is improved, but cohesive force is reduced, leading to increased outflow amount during pressing and base material contamination
Solution Approach 1:
The invention optimizes the glass transition temperature of the polyester resin component to be lower than 0°C, and controls its molecular weight within a specific range (5,000 to 100,000). These parameter optimizations ensure adequate flexibility for processing while maintaining sufficient cohesive force to minimize outflow during pressing operations.
Solution Approach 2:
The invention applies the polyester resin component specifically to provide low-temperature flexibility and processing suitability, while the polyurethane and epoxy resin components provide the cohesive strength and high-temperature performance. This functional differentiation allows each resin to contribute its strengths without compromising overall performance.
4Strength
If reaction between carboxyl group and epoxy group in polyurethane resin progresses at ordinary temperatures, then crosslinking is enhanced, but sheet life is shortened
Solution Approach 1:
The invention controls the acid value of the polyurethane resin within a specific range (50 to 500 equivalent/10^6 g) and optimizes the molecular weight and glass transition temperature parameters. These parameter controls regulate the reactivity between carboxyl and epoxy groups, enabling sufficient crosslinking for strength while preventing premature reaction that would shorten sheet life.
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 resin composition provides excellent adhesiveness to plastic films, metals, and glass epoxy, maintains adhesiveness at high temperatures and humidity, and extends sheet life, while ensuring processing suitability and improved solder resistance.
Implementation Method 1
a resin composition for an adhesive, wherein a polyurethane resin (a-1) containing a carboxyl group, a polyester resin (a-2), an epoxy resin (b) containing a nitrogen atom, and an epoxy resin (c) having a dicyclopentadiene skeleton are used
Data Source
AI summary
Provided is a resin composition for an adhesive comprising a polyurethane resin containing a carboxyl group, having specific range of an acid value having specific range of a number average molecular weight and having specific range of a glass transition temperature a polyester resin having specific range of a number average molecular weight and having specific range of a glass transition temperature; an epoxy resin containing a nitrogen atom; and an epoxy resin having a dicyclopentadiene skeleton, in which a content rate of the polyurethane resin to a sum of the polyurethane resin and the polyester resin is 70 to 95 percent by mass, a content rate of the total epoxy resin contained in the resin composition to the sum of the polyurethane resin and the polyester resin is 5 to 30 percent by mass.