Glass-Core Packaging Substrate to Suppress RDL Thermal Stress
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Solution Overview
Problem
Existing semiconductor packaging technologies face challenges in effectively integrating high-performance high-frequency semiconductor elements due to limitations in reducing wiring pitch and thermal stress issues with ceramic or resin substrates, leading to suboptimal electrical performance.
Innovation Solution
A packaging substrate comprising a glass core with a controlled thickness and an insulating layer having specific heat-resistant elasticity and mechanical properties, including a heat-resistant elasticity index (HEI) and heat-resistant mechanical property index (HMI), is used to mitigate thermal stress and enhance electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic substrate is used for packaging, then high resistance and dielectric constant are achieved, but mounting of high-performance high-frequency semiconductor elements becomes difficult
Solution Approach 1:
The patent employs a composite substrate structure combining glass core layer with resin-based insulating layers. The glass core provides dimensional stability and low dielectric loss, while the resin layers provide flexibility for mounting high-frequency elements. This composite approach resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
Different regions of the substrate have different material compositions optimized for specific functions. The glass core layer provides stable electrical properties in critical signal paths, while resin-based insulating layers provide adaptability for element mounting. This local differentiation allows simultaneous achievement of insulation performance and mounting capability.
2Adaptability or versatility
If resin substrate is used for packaging, then mounting of high-performance high-frequency semiconductor elements is enabled, but wiring pitch reduction is limited
Solution Approach 1:
The multi-layer composite structure allows combining materials with different properties. The glass core enables precise wiring formation due to its dimensional stability, while outer resin layers provide flexibility for fine-pitch wiring. This resolves the contradiction between mounting capability and wiring pitch reduction.
Solution Approach 2:
The patent uses multiple layers stacked in the vertical dimension to achieve fine wiring pitch in the horizontal dimension. By distributing wiring across multiple layers, the effective pitch is reduced without requiring excessively fine single-layer features, thus enabling both high-frequency element mounting and fine wiring.
3Reliability
If through holes are formed in silicon or glass substrate, then wiring length is shortened and electrical characteristics improve, but thermal stress and insulating layer peeling occur
Solution Approach 1:
The multi-material layered structure distributes thermal stress across layers with different thermal expansion coefficients. The glass core and resin layers are designed with compatible CTE values to minimize stress concentration around through-holes, preventing peeling while maintaining electrical performance.
Solution Approach 2:
The patent carefully controls the thickness and material composition parameters of each layer to optimize thermal stress distribution. By adjusting the CTE match between layers and controlling layer thickness ratios, the structure accommodates thermal expansion differences without causing delamination, thus maintaining both electrical characteristics and structural integrity.
4Reliability
If insulating layer is applied on glass core, then electrical insulation is provided, but thermal stress causes peeling of the insulating layer
Solution Approach 1:
The patent optimizes the CTE match between the glass core and insulating layer by selecting specific glass compositions and resin formulations. The glass core has CTE of 65-75 ppm/°C, while the insulating layer is formulated to have compatible CTE values, minimizing differential thermal expansion and preventing peeling while maintaining electrical insulation.
Solution Approach 2:
The use of a glass core with specific compositional characteristics provides a stable base that reduces thermal stress. The combination of glass core with carefully formulated resin insulating layers creates a composite structure where thermal expansion is harmonized, preventing delamination while providing effective electrical insulation.
Data Source
AI summary
A packaging substrate according to the present disclosure includes a glass core and an insulating layer disposed on the glass core. The glass core has a thickness of 100 μm or more. The insulating layer has an HEI value, which is the heat-resistant elasticity index of Equation 1 below, of 1.2 or more.HEI=TgE×CTE[Equation 1]in Equation 1,Tg is the glass transition temperature (unit: ° C.), E is the elastic modulus (unit: GPa) measured at 23° C., and CTE is the coefficient of thermal expansion (ppm/° C.).In this case, damage to the glass core during a process of forming a redistribution layer can be effectively suppressed.