Wiring Substrate Integrating Silicon Interposer with Resin
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Solution Overview
Problem
The increasing complexity and cost of build-up wiring boards due to the need for finer pitches in high-performance semiconductor chips, along with the introduction of silicon interposers, lead to increased costs and decreased yields, as well as structural warping issues.
Innovation Solution
A wiring substrate is constructed by stacking unit wiring boards with electrical connections via connection terminals, integrating a silicon interposer with a resin portion that fills gaps, allowing for minimal wiring layers and high reliability, using a mold compound resin with silica fillers to suppress warping and enhance rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a build-up wiring board is used with finer pitch wirings to accommodate high-performance semiconductor chips, then the connection capability is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The wiring board is divided into a core substrate and multiple unit wiring boards that can be independently manufactured and then stacked. This segmentation allows each unit to be produced with standard processes, avoiding the need to manufacture the entire multi-layer structure with fine-pitch wirings in one complex process.
Solution Approach 2:
The patent transitions from planar wiring expansion to three-dimensional stacking. Instead of adding more wiring layers horizontally, the solution stacks unit wiring boards vertically, each with relatively coarse pitch wirings, to achieve the required connection density without increasing manufacturing complexity.
2Reliability
If the number of wiring layers is increased to solve wiring pull-out issues, then the wiring connection reliability is improved, but the manufacturing cost increases due to unnecessary symmetric wiring formation
Solution Approach 1:
The patent employs asymmetric wiring configuration where unit wiring boards are stacked with wirings formed only on necessary surfaces. Unlike traditional symmetric designs that require identical wiring on both sides to prevent warping, this design allows asymmetric wiring placement optimized for functional requirements, reducing unnecessary wiring layers and manufacturing cost.
Solution Approach 2:
Different regions of the wiring board structure have different wiring configurations. Unit wiring boards are designed with wirings only where needed for electrical connection, rather than uniform symmetric wiring throughout. This local optimization reduces the total number of wiring layers while maintaining connection reliability.
3Adaptability or versatility
If a silicon interposer is introduced to enable fine-pitch connections, then the connection capability is improved, but the structural stability deteriorates due to warping
Solution Approach 1:
The patent uses a composite structure combining core substrate, unit wiring boards, and resin portions. This composite design distributes thermal and mechanical stresses across different materials with compatible properties, reducing warping. The resin portions act as stress-absorbing elements that compensate for differential expansion between the silicon interposer and other components.
Solution Approach 2:
Resin portions are introduced as intermediary elements between the silicon interposer and unit wiring boards, and between stacked units. These resin portions serve as buffer layers that accommodate thermal expansion differences and mechanical stress, preventing warping while maintaining the fine-pitch connection capability provided by the silicon interposer.
4Device complexity
If multiple unit wiring boards are stacked to construct the base wiring board, then the wiring layer number is reduced to necessary minimum, but the manufacturing precision requirements increase
Solution Approach 1:
Connection terminals are pre-formed on the unit wiring boards before stacking. These pre-formed terminals serve as alignment guides and mechanical interlocks during the stacking process, ensuring precise positioning without requiring high-precision alignment equipment. The preliminary formation of connection structures simplifies the assembly process.
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 the number of unnecessary wiring layers, lowers manufacturing costs, and improves yield while maintaining high reliability by integrating the silicon interposer and base wiring board with a resin portion that approximates thermal expansion coefficients, preventing warping and supporting the structure with high rigidity.
Implementation Method 1
The thermal expansion coefficient of the resin portion is 7 ppm/° C. to 20 ppm/° C., and the elastic modulus is 15 GPa to 25 GPa. By forming the resin portion from such a resin material, the thermal expansion coefficients between the silicon interposer, the base wiring board and the resin portion can be made to approximate rather that the case of where a general resin material is used. Thus, an occurrence of the warping to the wiring substrate can be suppressed.
Implementation Method 2
a mold compound resin containing a large amount of fillers (epoxy resin containing 85 to 90 percent silica filler as an example) is used as the material of the resin portion
Data Source
AI summary
In a wiring substrate according to the present invention, a base wiring board is constructed by stacking a plurality of unit wiring boards each having wiring patterns which enable an electrical connection between upper and lower sides, in a state that the plurality of unit wiring boards are connected to each other via a connection terminal, and a silicon interposer is stacked on the base wiring board via a connection terminal, and a resin portion is filled in a gap between the plurality of unit wiring boards as well as a gap between the base wiring board and the silicon interposer, and a resin portion serves as a substrate which integrates the base wiring board and the silicon interposer.