Glass Core PCB Edge Insulation for Crack Prevention
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Solution Overview
Problem
Current package substrates using organic materials as cores face challenges in implementing microcircuits and controlling warpage due to low modulus, and when transitioning to inorganic materials like glass, they are prone to cracks from external impacts or residual stress.
Innovation Solution
A printed circuit board design that uses an inorganic material such as glass as a core, with insulating layers on both sides and insulating materials with a lower coefficient of thermal expansion disposed at the edge portions, to reduce tensile stress caused by thermal contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an inorganic material such as glass is used as a core substrate, then warpage control and microcircuit implementation are improved, but the substrate becomes vulnerable to cracks from external impacts or residual stress
Solution Approach 1:
The patent uses a composite structure combining a glass substrate with insulating materials having different thermal expansion coefficients. The glass substrate provides high modulus for warpage control, while the composite insulating layer structure (with materials having lower thermal expansion coefficients at edge portions) compensates for stress concentration, preventing cracks while maintaining the benefits of the inorganic core material.
Solution Approach 2:
The patent applies different insulating materials with different thermal expansion coefficients to different regions of the substrate. Specifically, insulating materials with lower thermal expansion coefficients are disposed at edge portions where stress concentration occurs, while other regions use insulating layers with higher thermal expansion coefficients. This local differentiation of material properties reduces tensile stress at critical locations and prevents cracks.
2Ease of manufacture
If insulating layers with high coefficient of thermal expansion are disposed on the substrate, then ease of manufacture is improved, but tensile stress increases causing cracks
Solution Approach 1:
The patent differentiates the thermal expansion coefficients of insulating materials based on their location. Insulating layers with higher thermal expansion coefficients can be used in central regions where manufacturing is easier, while insulating materials with lower thermal expansion coefficients are specifically placed at edge portions to reduce tensile stress and prevent cracks during cooling processes.
Solution Approach 2:
The patent changes the thermal expansion coefficient parameter of insulating materials at different locations. By selecting materials with appropriate thermal expansion coefficients for specific regions (lower at edges, higher in center), the patent optimizes both manufacturability and stress resistance, preventing cracks while maintaining ease of fabrication.
3Device complexity
If the substrate edge portions are exposed without insulating material coverage, then device complexity is reduced, but stress concentration occurs leading to cracks
Solution Approach 1:
The patent applies insulating materials with lower thermal expansion coefficients specifically at edge portions of the substrate where stress concentration occurs during thermal cycles. This targeted application at critical locations prevents cracks while maintaining relatively simple overall device structure, as the differentiated material placement is localized rather than universal.
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 design effectively prevents cracks from occurring due to external impacts or residual stress, even when using glass as the core material, while also offering advantages in warpage control and microcircuit implementation.
Implementation Method 1
an insulating material, including a material having a coefficient of thermal expansion relatively lower than that of the substrate, may be disposed at an edge portion of the substrate, thereby reducing tensile stress caused by contraction behavior of an insulating layer having a high coefficient of thermal expansion
Data Source
AI summary
A printed circuit board includes a substrate having first and second external portions opposite to each other in a length direction, a first insulating layer disposed on an upper side of the substrate, a second insulating layer disposed on a lower side of the substrate, a first insulating material covering at least a portion of the first external portion of the substrate, and a second insulating material covering at least a portion of the second external portion of the substrate. The first and second insulating layers respectively have a coefficient of thermal expansion higher than that of the substrate. The first and second insulating materials respectively have a coefficient of thermal expansion lower than that of the substrate.