Semiconductor Imaging Device Thermal Management via Inverted LGA Package
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Solution Overview
Problem
Semiconductor devices with imaging units face challenges in achieving high accuracy flatness and efficient heat radiation, particularly when used in holographic memory applications, due to issues with solder ball deformation and differing linear expansion coefficients of materials in conventional BGA packages.
Innovation Solution
A semiconductor device configuration where the package with an imaging function is mounted on the upper surface of a mounting board, and a heat sink is placed on the lower surface, with a through-hole for a heat transfer member to enhance heat radiation, using an insulating base material and a cap material for translucency to allow light entry, and adopting an LGA package configuration without solder balls to ensure flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a BGA package structure is used, then the device can be manufactured with standard processes, but the flatness and heat radiation performance are insufficient for imaging units
Solution Approach 1:
The patent inverts the conventional BGA package structure by placing the imaging unit on the lower surface of the semiconductor chip instead of the upper surface. This allows the ball terminals to be positioned on the upper surface for mounting, while the imaging unit faces downward toward the holographic memory medium, achieving both flat top surface for mounting and proper optical alignment without requiring complex additional structures
Solution Approach 2:
The patent utilizes the thickness dimension of the semiconductor chip to resolve the contradiction. By orienting the imaging unit perpendicular to the mounting surface (facing downward through the chip thickness), it achieves proper alignment with the holographic memory medium while maintaining a flat upper surface for standard BGA mounting processes
2Temperature
If a heat sink is added to improve heat radiation, then heat dissipation improves, but the flatness of the package is compromised
Solution Approach 1:
The patent inverts the heat sink placement by positioning it on the lower surface of the semiconductor chip opposite to the imaging unit, or integrating it into the substrate rather than attaching it to the top. This allows heat dissipation functionality to be maintained while preserving the flat upper surface required for precise mounting and optical alignment
3Reliability
If solder balls are used for mounting, then electrical connection is achieved, but deformation occurs compromising flatness accuracy
Solution Approach 1:
The patent inverts the mounting interface by placing the ball terminals on the upper surface of the semiconductor chip for mounting to the substrate, while the imaging unit is positioned on the lower surface. This separation allows the ball terminals to handle mechanical and electrical connection functions without compromising the flatness requirements of the imaging unit, as the mounting stresses are isolated to the terminal regions
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 configuration allows for efficient heat radiation and improved flatness, enabling reliable data reading in holographic memory applications by ensuring light can enter the imaging unit and heat is effectively dissipated, while maintaining high-accuracy flatness and reducing warpage.
Implementation Method 1
a heat transfer member coupled to the insulating base material is inserted into the through-hole
Implementation Method 2
a heat radiation member coupled to the heat transfer member is provided on the lower surface side of the mounting board
Data Source
AI summary
An object of the present invention is to improve the reliability of a semiconductor device having an imaging function.A semiconductor device includes a package having a cavity and terminals (TE1), a semiconductor chip that has an imaging unit and is arranged in the cavity, and a cap material with which the cavity is sealed and which has translucency. In addition, the semiconductor device includes a mounting board that has a through-hole and terminals (TE2) and is arranged so as to electrically couple the terminals (TE1) to the terminals (TE2), a heat transfer member that is inserted into the through-hole and is coupled to the package, and a heat sink coupled to the heat transfer member.