Flip Chip Controller Mounting for Stacked Die Wirebonding
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Solution Overview
Problem
In semiconductor packages with stacked die, the limited space on the substrate makes it difficult to accommodate all necessary wire bonds for controller die connections, especially when multiple flash memory die are used, as conventional methods like redistribution layers are not always feasible due to the small size of the controller die and add complexity, cost, and time.
Innovation Solution
The controller die is mounted directly to the substrate in a flip chip arrangement, eliminating the need for wire bonds outside its footprint, and a spacer layer is used to create a level surface for mounting flash memory die, allowing for easier wirebonding and efficient use of space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the controller die is mounted at the top of the memory die stack using conventional wire bonding, then electrical connections can be made, but the substrate space becomes insufficient to accommodate all necessary wire bonds and contact pads
Solution Approach 1:
The controller die is moved from the top of the stack to the bottom, bonding directly to the substrate. This dimensional repositioning allows wire bonds to be routed from the bottom edge of the substrate rather than competing for space on the top surface, effectively utilizing the vertical dimension to resolve the substrate space constraint.
Solution Approach 2:
Instead of mounting the controller die at the top of the stack as conventionally done, the invention inverts the mounting order by placing the controller die at the bottom, directly on the substrate. This inversion eliminates the wire bonding space problem while maintaining all necessary electrical connections.
2Quantity of substance
If multiple flash memory die are stacked to increase capacity, then storage capacity increases, but the number of wire bonds and contact pads required increases, making substrate space even more limited
Solution Approach 1:
By positioning the controller die at the bottom of the stack rather than the top, the invention enables wire bonds to extend from the bottom edge of the substrate. This allows multiple memory die to be stacked without proportionally increasing the complexity of wire bonding, as all connections can be routed from the bottom dimension rather than requiring extensive top-surface contact pads.
3Area of stationary object
If a redistribution layer is added to the controller die to reposition bond pads, then wire bonding space can be improved, but fabrication complexity, cost, and time increase
Solution Approach 1:
The invention extracts the controller die from the stack and positions it directly on the substrate at the bottom. This eliminates the need for redistribution layers within the controller die itself, as the bond pads can directly access the substrate edge for wire bonding, thereby reducing fabrication complexity, cost, and time.
Solution Approach 2:
Instead of adding complex redistribution layers to reposition bond pads on the controller die, the invention inverts the approach by repositioning the entire controller die to the bottom of the stack, where standard bond pads can naturally access wire bonding space at the substrate edge, simplifying the fabrication process.
Data Source
AI summary
A semiconductor package including a plurality of stacked semiconductor die, and methods of forming the semiconductor package, are disclosed. In order to ease wirebonding requirements on the controller die, the controller die may be mounted directly to the substrate in a flip chip arrangement requiring no wire bonds or footprint outside of the controller die. Thereafter, a spacer layer may be affixed to the substrate around the controller die to provide a level surface on which to mount one or more flash memory die. The spacer layer may be provided in a variety of different configurations.