Semiconductor Cavity Mounting for Millimeter Wave Signal Integrity
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Solution Overview
Problem
Existing semiconductor devices with millimeter wave antennas face signal quality deterioration due to long wire lengths and inadequate heat radiation, particularly at high frequencies like 60 GHz, where parasitic inductance and heat accumulation issues are significant.
Innovation Solution
A semiconductor device design featuring a wiring board with a cavity-mounted chip, where the chip is in close contact with a side wall near high-frequency wiring, and a heat-radiating structure is implemented with thermal vias piercing the board to enhance heat dissipation, including a recessed portion to accumulate adhesive and direct heat away from the chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the chip is mounted in a cavity with the back surface adhered to the bottom surface through adhesive, then the wire length can be made as short as possible, but heat radiation from the chip becomes inadequate causing thermal runaway
Solution Approach 1:
The invention transitions from two-dimensional heat dissipation (through the adhesive layer at the bottom) to three-dimensional heat dissipation by forming protrusions that extend upward toward the chip. This vertical dimension allows heat to be conducted from multiple surfaces of the chip (bottom and side walls), significantly improving thermal management while maintaining the compact cavity structure.
Solution Approach 2:
The heat-radiating structure is divided into multiple protrusions distributed across the bottom surface of the cavity. Each protrusion acts as an independent heat conduction path, and their collective effect provides comprehensive thermal management. The segmentation also allows strategic placement near high-frequency wiring regions to address localized heating issues.
2Temperature
If thermal via holes are formed to penetrate the board for heat radiation, then heat dissipation is improved, but the structure complexity increases
Solution Approach 1:
The invention merges the heat-radiating function with the existing cavity structure. The protrusions are formed as integral parts of the cavity bottom surface, combining mechanical support and thermal management functions into a single structure. This eliminates the need for separate thermal via holes penetrating the entire board, reducing structural complexity while achieving effective heat dissipation.
Solution Approach 2:
The cavity structure serves multiple functions: it provides mechanical mounting for the chip, defines the wiring board layout, and through its protrusions, acts as a heat-radiating structure. This multi-functionality reduces the need for additional dedicated heat dissipation components, simplifying the overall device architecture.
3Reliability
If the chip is positioned to minimize wire length, then parasitic inductance is reduced, but heat accumulates near the contact region with the cavity bottom
Solution Approach 1:
The invention applies local quality by concentrating heat-radiating protrusions in specific regions of the cavity bottom, particularly near areas where high-frequency wiring is formed and where heat accumulation is most problematic. This localized approach targets heat dissipation where it is most needed, maintaining signal quality while managing thermal hotspots.
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 minimizes parasitic inductance, improves signal quality for millimeter wave transmission, and effectively manages heat radiation, preventing thermal runaway and maintaining high-frequency transmission characteristics.
Implementation Method 1
the back surface (surface opposite to the surface where the electrode pads are formed) of the chip is adhered to the bottom surface of the cavity through an adhesive
Implementation Method 2
a thermal via (via hole for heat radiation) is formed. This thermal via is formed to penetrate the board in the thickness direction thereof in a manner connecting the bottom surface (which is thermally bonded to the chip with an adhesive interposed therebetween) of the cavity provided in the package to the outside of the board
Data Source
AI summary
A semiconductor device includes a structure in which a semiconductor element (chip) is mounted in a cavity formed in a wiring board with an adhesive interposed between the chip and a bottom surface of the cavity, and electrode terminals of the chip are connected via wires to wiring portions formed on the board around the cavity. The chip is mounted in close contact with a side wall of the cavity, the side wall being near a region where a wiring for higher frequency compared with other wirings within the wiring portion is formed. A recessed portion is provided in a region of the bottom surface of the cavity, and a thermal via extending from the bottom surface of the recessed to the outside of the board is provided, the region being near a portion where the chip is in close contact.