Rigid Flex Circuit Board Thermal Shock Reliability
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Solution Overview
Problem
Rigid flex circuit boards face reliability issues in thermal shock testing due to layering complications and design limitations that prevent copper layers from being stacked facing each other, leading to potential short circuits and increased material costs.
Innovation Solution
A rigid flex circuit board design featuring a flexible circuit board with a core layer, cover layers, bonding layers, insulating layers, and superposition layers, where copper layers are partially covered and laminated with polypropylene insulating material between bonding and cover layers, allowing for improved thermal shock reliability and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bonding sheet is used to laminate the entire sheet surface to achieve the characteristics of the bent region, then the structural strength is improved, but layering occurs between the bonding sheets during high temperature and high pressure lamination process, compromising thermal shock reliability
Solution Approach 1:
The bonding sheet is divided into a first bonding sheet and a second bonding sheet with different material compositions. The first bonding sheet contains a rigid filler for structural strength, while the second bonding sheet contains a flexible filler for flexibility and thermal shock resistance. This segmentation allows each bonding sheet to perform its specific function without compromising the other.
Solution Approach 2:
Different regions of the bonding structure are assigned different material properties. The first bonding sheet provides rigid support where structural strength is needed, while the second bonding sheet provides flexible accommodation where thermal expansion and contraction occur. This local differentiation of material quality resolves the contradiction between strength and thermal shock reliability.
2Quantity of substance
If copper layers are disposed facing each other to reduce material cost, then the cost is reduced, but short circuit may occur
Solution Approach 1:
The second bonding sheet acts as an intermediary layer between facing copper layers. Its flexible material composition provides electrical insulation and prevents short circuits while allowing the copper layers to be positioned facing each other for cost reduction. This intermediary layer resolves the contradiction between material cost and electrical reliability.
3Strength
If a rigid circuit board is used to provide structural strength, then the strength is improved, but the flexibility is poor, limiting application
Solution Approach 1:
The bonding structure uses a composite material system with two distinct bonding sheets having different filler compositions. The first bonding sheet with rigid filler provides structural strength, while the second bonding sheet with flexible filler provides flexibility. This composite approach allows the circuit board to exhibit both strength and flexibility simultaneously, resolving the contradiction between these properties.
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
Enhances the reliability of multi-layer flex sheets in thermal shock testing while overcoming design limitations, reducing material costs by allowing copper layers to be stacked without causing short circuits.
Implementation Method 1
a first insulating layer covering a portion of the first core circuit layer and a portion of the first cover layer, wherein the thickness of the first insulating layer is comparable to the thicknesses of the first cover layer and the first bonding layer. The second insulating layer covers a portion of the second core circuit layer and a portion of the second cover layer
Implementation Method 2
The first bonding layer covers a portion of the first cover layer, and the second bonding layer covers a portion of the second cover layer
Data Source
AI summary
A rigid flex circuit board is provided, including a flexible circuit board, which includes a core layer, first and second cover layers, first and second bonding layers, first and second dielectric layers, and first and second superposition layers. The core layer includes first and second core circuit layers. The first and second cover layers cover a portion of the first and second core circuit layers. The first and second bonding layers cover a portion of the first and second cover layers. The first and second dielectric layers cover a portion of the first and second core circuit layers and the first and second cover layers. The first superposition layer is disposed on the first bonding layer and the first dielectric layer, and the second superposition layer is disposed on the second bonding layer and the second dielectric layer.