Flexible Substrate Memory Module with Overlapping Package Units
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Solution Overview
Problem
Existing memory modules face limitations in increasing capacity and mounting reliability due to the challenges of miniaturization and solder joint degradation, particularly when trying to integrate a high number of memory cells on limited semiconductor chip sizes and using solder balls for mounting.
Innovation Solution
The solution involves using a memory module configuration where multiple package units with flexible substrates are mounted to a module substrate, allowing partial overlap to increase capacity and improve solder joint reliability by using polyimide-based flexible substrates with circuit patterns and insulation layers, and connecting via solder balls, anisotropic conductive films, or connectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If more memory semiconductor packages are mounted on a limited-size module substrate, then memory module capacity increases, but the available mounting area decreases
Solution Approach 1:
The patent applies nesting by placing package units in an overlapping configuration where multiple packages are stacked vertically to some extent, allowing them to occupy three-dimensional space rather than strictly two-dimensional substrate area. This enables more packages to be mounted on the same substrate footprint.
Solution Approach 2:
The patent transitions from traditional planar mounting to a three-dimensional arrangement using flexible substrates that can be folded or overlapped. Package units are positioned at different vertical levels and angles, utilizing the Z-dimension to increase packaging density without expanding the substrate footprint.
2Ease of manufacture
If solder balls are used to mount packages on a module substrate, then mounting process is simplified, but solder joint reliability degrades
Solution Approach 1:
The flexible substrate acts as an intermediary component between the memory semiconductor packages and the module substrate. It provides alternative mounting methods such as adhesive bonding or mechanical attachment, reducing dependence on solder balls and thereby improving solder joint reliability while maintaining ease of manufacture.
3Quantity of substance
If high integration of memory cells is pursued on semiconductor chips, then memory capacity increases, but manufacturing complexity and development time increase
Solution Approach 1:
Instead of achieving high integration through single large-scale chip fabrication, the patent segments the memory system into multiple smaller memory semiconductor packages. Each package contains a manageable number of memory cells, and the overall capacity is achieved by combining multiple packages. This reduces the complexity of individual chip manufacturing processes.
Data Source
AI summary
A memory module includes a module substrate and a plurality of package units mounted to the module substrate such that they partially overlap each other. Each package unit has at least one memory semiconductor package attached thereto. Each package unit includes a flexible substrate, which has outer terminals provided over a lower surface adjacent to one edge thereof to form electrical connections with the module substrate, and the memory semiconductor package attached to one surface or each of both upper and lower surfaces of the flexible substrate.