Mold Insert Recess Depth for Gate-Induced Delamination Control
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Solution Overview
Problem
The high temperature and shear stress induced by polymer melt during injection over molding cause delamination of temperature-sensitive layers in wafer substrates near the gate, leading to aesthetically and optically unusable lenses.
Innovation Solution
Increasing the recess depth of the mold insert to 2 mm or greater, adjusting the mold sides to compensate for substrate thickness, and reducing shear stress along the sidewall adjacent to the gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a standard mold apparatus is used for injection over molding, then the molding process can be completed, but shear stress induced by the gate geometry causes delamination of temperature-sensitive layers
Solution Approach 1:
The patent applies local quality by creating a recessed region at the specific location where the substrate contacts the mold insert. This localized geometric modification concentrates the compliance effect precisely where needed - at the interface between the substrate and mold insert near the gate - without altering the entire mold structure. The recess depth is specifically controlled (e.g., 0.5-2 mm) to provide local stress relief exactly where delamination occurs.
Solution Approach 2:
The patent changes the geometric parameter of the mold insert by introducing a recess with specific depth and dimensions. This parameter change transforms the rigid mold insert surface into a compliant interface that can accommodate substrate deformation. The recess depth, width, and shape are optimized parameters that directly control the stress distribution and prevent delamination while maintaining processability.
2Reliability
If the recess depth is increased to reduce shear stress, then delamination is prevented, but the mold apparatus complexity increases
Solution Approach 1:
The patent segments the mold insert surface into two distinct regions: a recessed region that contacts the substrate and provides compliance, and a non-recessed region that maintains the standard mold structure. This segmentation allows the complex compliant function to be localized to only the necessary area, keeping the rest of the mold apparatus simple and easy to manufacture.
Solution Approach 2:
Instead of making the entire mold insert compliant or complex, the patent inverts the approach by creating a recessed void space rather than adding material or complex mechanisms. This negative space approach simplifies manufacturing compared to adding active compliance mechanisms, as the recess can be created through standard machining or molding techniques.
3Stress or pressure
If the cavity surface is adjusted to increase recess depth, then shear stress is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-forming the recessed region into the mold insert during mold manufacturing, before the actual injection molding process. This pre-established geometric feature eliminates the need for complex real-time adjustments during production, as the compliance function is built-in from the start. The recess depth and dimensions are precisely controlled during mold fabrication using standard precision machining techniques.
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
Significantly reduces the occurrence of delamination defects by minimizing shear stress, resulting in defect-free lenses across various base curvatures.
Implementation Method 1
the high melt temperature and shear of the molten polymer resin as it flows past the gate and into the mold cavity can cause a temperature-sensitive functional layer of a multilayer laminate substrate to lose its mechanical and cohesive integrity. This increases the susceptibility of delamination of said layer near the gate
Implementation Method 2
high melt temperature and shear of the molten polymer resin as it flows past the gate and into the mold cavity
Implementation Method 3
shear induced temperature rise and turbulence as it egresses from the gate
Data Source
AI summary
A mold device includes a first mold side configured to receive a substrate in a cavity and to couple with a second mold side, the first mold side including a sidewall and a gate, wherein the substrate is recessed in the first mold side at a substrate recess depth of 2 mm or greater, and wherein the substrate recess depth is a distance along the sidewall between a bottom of the gate and a surface of the substrate in a direction perpendicular to a line between the gate and a middle of the surface of the substrate, and wherein the bottom of the gate and a top of the sidewall are at distinct heights from the surface of the substrate.