Multi-Material Resin Outer Case for Circuit Board Protection
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Solution Overview
Problem
The existing methods for forming electronic circuit units with integrated circuit boards and outer cases using mold resin often result in deformation and damage of the circuit board due to pressure from the resin during injection molding, particularly for components intolerant of pressure, leading to increased costs and component count.
Innovation Solution
The implementation of a multi-material molding process using resins with different fluidities, where the rear surface of the mold exclusion part is covered by a resin with higher fluidity than the rest of the outer case, and the inclusion of strength increasing features like reinforcement conductor patterns or thickness increases in the circuit board's inner layer to mitigate pressure-induced deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the outer case is molded by injection molding using thermoplastic resin, then the number of components can be reduced and assembling work can be eliminated, but the circuit board may be deformed due to pressure of the resin acting on the rear surface side of the exposed portion
Solution Approach 1:
The outer case is divided into two distinct parts: a hard case portion made from resin with low fluidity and a soft case portion made from resin with high fluidity. This segmentation allows each portion to serve different functions - the hard case provides structural support while the soft case conforms to the circuit board shape without causing deformation, thus resolving the contradiction between component integration and manufacturing precision.
Solution Approach 2:
Different regions of the outer case are assigned different material properties. The hard case portion uses resin with low fluidity for structural rigidity, while the soft case portion uses resin with high fluidity to adapt to the circuit board's contour. This local differentiation of material properties enables both component reduction and prevention of circuit board deformation.
2Reliability
If electronic components intolerant of resin pressure are collectively arranged at a particular portion and the circuit board is set exposing that portion, then pressure damage to components can be avoided, but the circuit board may still be deformed due to pressure acting on the rear surface side
Solution Approach 1:
The soft case portion is specifically designed to cover the rear surface of the exposed portion of the circuit board. This localized application of high-fluidity resin creates a cushioning effect precisely where needed, protecting both the pressure-sensitive components from front surface pressure and the circuit board from rear surface pressure-induced deformation.
Solution Approach 2:
The soft case portion acts as a pre-established cushioning layer between the injection molding resin and the circuit board's rear surface. This prior cushioning prevents direct transmission of molding pressure to the circuit board, thereby preventing deformation before it can occur during the molding process.
3Strength
If a hard case made of resin is molded separately and the circuit board is incorporated into it, then structural support is provided, but the number of components and assembling cost increase
Solution Approach 1:
The hard case and soft case are merged into a single integrated outer case molded in one injection molding process. The hard case portion provides the necessary structural support while the soft case portion adds conformal protection, eliminating the need for separate components and assembly steps while maintaining or enhancing overall structural integrity.
Solution Approach 2:
The outer case utilizes a composite structure combining two types of resin materials with different fluidity characteristics. This composite approach allows the single component to simultaneously provide structural support (from the low-fluidity resin) and adaptive conformal protection (from the high-fluidity resin), replacing what would otherwise require multiple separate components.
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
This approach reduces deformation and damage to the circuit board and electronic components during injection molding, while also reducing overall costs by utilizing specific resin properties and eliminating the need for separate hard cases and independent connector assembly.
Implementation Method 1
The outer case is multi-material molded using plural kinds of resin having different fluidities. A rear wall of the outer case located on the rear surface side of the mold exclusion part is made of one of the plural kinds of the resin having a fluidity higher than a fluidity of another one of the plural kinds of the resin constituting the other portion of the outer case.
Data Source
AI summary
An electronic circuit unit in which a mold exclusion part, having a rear surface side covered by mold resin and a front surface side exposed from an outer case, is provided at a part of a plate surface of a circuit board which is mounted with electronic components and is covered by the outer case formed by the mold resin. The outer case is multi-material molded using plural kinds of resin having different fluidities. A rear wall of the outer case located on the rear surface side of the mold exclusion part is made of one of the plural kinds of the resin having a fluidity higher than a fluidity of another one of the plural kinds of the resin constituting the other portion of the outer case.