Vertical Contact Finger Substrate Layout for Low-Profile Memory Cards
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Solution Overview
Problem
Conventional semiconductor memory devices face issues with semiconductor dies cracking under high compressive forces during encapsulation and require bulky host device sockets due to the need for buckles and socket pins to align contact fingers vertically, which occupies valuable space.
Innovation Solution
A semiconductor device with a flexible substrate featuring vertically oriented contact fingers formed near the edges, allowing the substrate to fold during encapsulation and eliminating the need for bulky socket components by exposing contact fingers on vertical surfaces, enabling a low-profile host device slot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor dies are mounted over recessed contact fingers on the bottom surface of the substrate, then electrical connection is achieved, but the dies and substrate are subject to high compressive forces during encapsulation which can cause the semiconductor dies to crack
Solution Approach 1:
The contact fingers are repositioned from the bottom surface (horizontal plane) to the side surface (vertical plane) of the substrate. This dimensional change allows the contact fingers to be positioned in a different spatial orientation, eliminating the need for dies to be mounted directly over recessed contact fingers and thereby reducing compressive forces on the dies during encapsulation.
Solution Approach 2:
A flexible circuit board is introduced as an intermediary component to connect the semiconductor dies to the contact fingers on the side surface. This flexible circuit board allows for strain relief and reduces the transmission of compressive forces from the encapsulation process to the semiconductor dies, preventing cracking while maintaining electrical connection.
2Reliability
If conventional sockets with buckles and socket pins are used to position the memory card vertically, then proper mating of socket pins with contact fingers is ensured, but valuable space along the vertical axis is occupied, requiring 1.5 to 2 times the thickness of the memory card
Solution Approach 1:
The contact fingers are repositioned from the bottom surface to the side surface of the substrate, changing the contact interface from horizontal to vertical orientation. This allows the memory card to mate with the socket in a different orientation, eliminating the need for vertical buckles and socket pins, and reducing the socket height to approximately the same as the memory card thickness.
Solution Approach 2:
The unnecessary components (buckles and vertical socket pins) are removed from the socket design. By repositioning the contact fingers to the side surface of the memory card, the patent extracts and eliminates the need for these space-consuming positioning components, achieving proper contact alignment without them.
3Reliability
If contact fingers are formed on the bottom surface of the substrate, then electrical connection is achieved, but bulky socket components are required which take up valuable space in the host device
Solution Approach 1:
The contact fingers are repositioned from the bottom surface (horizontal plane) to the side surface (vertical plane) of the substrate. This dimensional change allows for a more compact socket design that does not require bulky components, thereby reducing the volume occupied in the host device while maintaining reliable electrical connection.
Solution Approach 2:
The patent changes the spatial parameters of the contact fingers by repositioning them from the bottom surface to the side surface of the substrate. This parameter change in position and orientation enables a more compact overall design, reducing the volume requirements for the host device while preserving electrical connection functionality.
Data Source
AI summary
A method of forming a semiconductor device includes forming vertical contact fingers in a substrate having side portions that are flexible. Contact fingers are formed near one or more edges of the flexible side portions of the substrate. After semiconductor dies are mounted to and electrically coupled to the substrate, the semiconductor device may be encapsulated by placing the device in a mold chase including upper and lower mold plates. The lower mold plate is sized smaller than the substrate so that the flexible side portions of the substrate including the contact fingers fold vertically upward to fit within the mold.