Circuit Module Resin Layering for Stress Distribution
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Solution Overview
Problem
Flexible circuit boards used in flip chip structures face stress concentration issues when bent or expanded, leading to potential damage due to the steep variation in hardness at the resin-circuit board interface, causing intensive deformation and damage to the board or wiring.
Innovation Solution
A circuit module design featuring a base with a mounting region for electronic components, a lower resin layer, and a surface resin layer of varying hardness, where the hard resin layer is formed outside the mounting region to distribute stress gently and protect components from both flat and concentrated loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer resin coating is used to seal the flip chip, then moisture resistance is improved, but stress concentration occurs at the periphery when the circuit board deforms
Solution Approach 1:
The resin coating is divided into multiple layers with different hardness characteristics. The first resin layer (softer, lower hardness) is applied directly to the flip chip periphery, while the second resin layer (harder, higher hardness) is applied over the first layer. This segmentation allows each layer to perform its specific function: the softer first layer absorbs stress during board deformation, while the harder second layer provides robust moisture sealing.
Solution Approach 2:
Different regions of the resin coating structure are assigned different hardness properties to match local functional requirements. The first resin layer near the chip perimeter uses softer material to accommodate stress concentration zones, while the outer second resin layer uses harder material for enhanced environmental protection. This local quality differentiation resolves the contradiction between moisture sealing and stress distribution.
2Strength
If the resin layer is made hard to protect components, then strength is improved, but the circuit board deforms intensively at the contact portion when bent
Solution Approach 1:
The resin coating structure is designed with dynamic hardness characteristics through layering. The softer first resin layer near the chip allows for dynamic deformation absorption when the board bends, while the harder second resin layer provides static protective strength. This dynamic differentiation enables the coating to adapt to both flexible board operation and component protection requirements.
Solution Approach 2:
The resin coating employs a composite structure with two distinct resin layers having different hardness properties. The first layer uses a softer resin material for flexibility and stress absorption, while the second layer uses a harder resin material for strength and protection. This composite material approach resolves the contradiction between board flexibility and component protection.
3Reliability
If the resin coating covers the entire chip surface, then sealing is improved, but manufacturing complexity increases due to multiple processing steps
Solution Approach 1:
The first resin layer is applied and cured to establish the foundational sealing structure before the second resin layer is applied. This preliminary action creates a prepared substrate that facilitates the subsequent coating process, ensuring proper adhesion and stress distribution while maintaining a systematic, step-by-step manufacturing approach that balances complexity with performance.
Solution Approach 2:
The sealing structure transitions from a single-dimensional (single-layer) approach to a multi-dimensional (multi-layer) configuration. By adding the vertical dimension of layering with different hardness properties, the patent achieves superior sealing and stress distribution without requiring complex lateral structuring, thus managing manufacturing complexity through vertical differentiation rather than horizontal complexity.
Data Source
AI summary
Breakage of a board due to local concentration of stress at the time when a circuit module deforms is reduced. A circuit module includes a base, a lower layer, and a surface layer. The base has a mounting region in which an electronic component is mounted. The lower layer is made of a resin material. The lower layer is formed over from the mounting region to a region other than the mounting region on the base. The surface layer is made of a resin material different in hardness from the resin material of the lower layer. A periphery of the surface layer is located outside the mounting region and inside a region in which the lower layer is formed.