Grindable Heat Sink Structure for Thinned Multi-Die Packages
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Solution Overview
Problem
Conventional heat sinks attached to semiconductor devices using thermal interface materials cannot withstand the forces of post-mold grinding, necessitating additional steps and increased costs for customers who need to thin devices like smartphones and laptops.
Innovation Solution
A grindable heat sink is plated on the top die of a semiconductor die stack, allowing simultaneous grinding of the molding and heat sink, eliminating the need for separate thermal interface materials and reducing the number of manufacturing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional heat sinks are attached using thermal interface materials, then heat dissipation is achieved, but the heat sink cannot withstand post-mold grinding forces
Solution Approach 1:
The heat sink is merged with the molding material to form a single integrated component. The heat sink is formed by injecting heat sink material (such as metal powder or conductive polymer) into the molding cavity, creating a monolithic structure where the heat sink and molding are inseparable. This eliminates the attachment interface and allows the heat sink to withstand grinding forces without detaching or damaging the thermal interface material.
Solution Approach 2:
The heat sink is constructed using composite materials that combine the structural properties of the molding material with the thermal conductivity of heat sink materials. By incorporating metal powders, conductive fillers, or other thermally conductive composite materials into the molding matrix, the heat sink achieves both mechanical strength for grinding and thermal performance for heat dissipation.
2Reliability
If separate thermal interface materials are used, then thermal conductivity is improved, but the number of manufacturing steps and costs increase
Solution Approach 1:
The thermal interface material function is merged into the molding process itself. Instead of applying a separate thermal interface layer between the heat sink and substrate, the molding material itself is formulated to provide thermal conductivity. This eliminates the separate thermal interface material step and reduces manufacturing complexity while maintaining thermal performance.
Solution Approach 2:
The molding material serves multiple functions simultaneously: it provides structural support, electrical insulation, mechanical protection, and thermal conduction. By designing the molding compound to exhibit thermal conductivity comparable to or exceeding conventional thermal interface materials, the material becomes multi-functional, eliminating the need for separate thermal management layers.
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
The solution enables efficient thinning of semiconductor packages without damaging the heat sink, maintaining performance and reducing manufacturing complexity and cost.
Implementation Method 1
A grindable heat sink is plated on the top die of a semiconductor die stack
Implementation Method 2
increased power causes devices to generate more heat... The issue of heat is further magnified due to the higher density and reduced surface area of stacked dies
Data Source
AI summary
A semiconductor package can include a semiconductor die stack including a top die and one or more core dies below the top die. The semiconductor package can further include a metal heat sink plated on a top surface of the top die and have a plurality of side surfaces coplanar with corresponding ones of a plurality of sidewalls of the semiconductor die stack. A molding can surround the stack of semiconductor dies and the metal heat sink, the molding including a top surface coplanar with an exposed upper surface of the metal heat sink. The top surface of the molding and the exposed upper surface of the metal heat sink are both mechanically altered. For example, the metal heat sink and the molding can be simultaneously ground with a grinding disc and can show grinding marks as a result.