Differential Height PCB Layout for Higher-Capacity Memory Cards
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Solution Overview
Problem
Conventional memory cards have an inefficient design that limits the space available for memory dies along the height dimension, due to the need for unused mold compound to meet thickness requirements.
Innovation Solution
The use of a differential height substrate with a first section for contact fingers and a thinner second section for mounting semiconductor dies, along with a two-layer mold compound structure, maximizes the space available for memory dies while maintaining the required thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If uniform thickness substrate and mold compound are used to meet standard thickness requirements, then the required thickness at contact fingers is achieved, but the space available for memory dies along the height dimension is reduced
Solution Approach 1:
The substrate is designed with differential thickness: a first region with greater thickness supporting contact fingers and a second region with lesser thickness for mounting memory dies. This local variation in thickness allows each region to be optimized for its specific function, providing required thickness at contact fingers while maximizing space for memory dies in the thinner region.
Solution Approach 2:
The substrate is segmented into two distinct regions with different thicknesses: a first region for contact fingers and a second region for memory dies. This segmentation allows independent optimization of each region's thickness to meet different functional requirements, resolving the contradiction between maintaining standard thickness at contact fingers and maximizing space for memory dies.
2Length of stationary object
If thicker mold compound is applied to meet overall card thickness requirement, then the overall thickness of 2.1mm is achieved, but the space available for memory dies is wasted
Solution Approach 1:
The mold compound is applied with varying thickness across different regions: a first thickness in the region of contact fingers and a second, lesser thickness in the region of memory dies. This local variation ensures the overall card thickness requirement is met while minimizing unnecessary mold compound thickness over memory die space, thereby maximizing usable volume.
Solution Approach 2:
The mold compound application is segmented into two regions with different thicknesses: a first region corresponding to contact fingers and a second region corresponding to memory dies. This segmentation allows the overall thickness requirement to be satisfied while optimizing the volume available for memory dies by reducing excess mold compound in the die region.
Data Source
AI summary
A semiconductor device has a differential height substrate including a first section and a second section thinner than the first section. The first section may include contact fingers for electrically coupling the semiconductor device to a connector in a slot of a host device. The second section may include one or more semiconductor dies and other components. Mold compound may encapsulate the semiconductor dies and other components, leaving the contact fingers in the first section of the substrate exposed. A second layer of mold compound may also be applied to a second, uniformly planar surface of the differential height substrate opposite a surface including the one or more semiconductor dies.