Coined Lid Air-Cavity Package for GaN Top-Side Cooling
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Solution Overview
Problem
High-power radio frequency (RF) devices based on gallium nitride (GaN) technology face challenges in effectively managing heat dissipation due to limited bottom-side cooling through package substrates, leading to thermal resistance and reduced device reliability.
Innovation Solution
An air-cavity package design with a coined lid that incorporates heat spreaders and a sealed air cavity for top-side cooling, utilizing engineered nano copper paste for thermal expansion matching and a lid sealing component to encapsulate flip-chip dies, enhancing thermal conductivity and electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bottom-side cooling through package substrate is used, then device mounting is simplified, but heat dissipation efficiency is insufficient leading to high thermal resistance
Solution Approach 1:
The cooling solution is segmented into two independent paths: bottom-side cooling through the package substrate and top-side cooling through the coined lid with heat spreaders. This allows each cooling path to be optimized separately and work together to solve the thermal management problem.
Solution Approach 2:
The invention transitions from single-direction (bottom-side) cooling to multi-directional cooling by adding top-side cooling capability through the coined lid structure with heat spreaders, effectively utilizing both vertical dimensions for heat dissipation.
2Power
If gate spacing of GaN devices is reduced to increase power output, then breakdown voltage and maximum output power are enhanced, but concentrated heat flux increases leading to thermal management challenges
Solution Approach 1:
The invention extracts heat from the concentrated heat flux regions by positioning heat spreaders directly over the active regions of the GaN devices. This removes the thermal problem from the device structure and handles it separately through dedicated heat spreading components.
Solution Approach 2:
The coined lid structure provides localized cooling solutions with heat spreaders positioned specifically over the high heat flux active regions of the GaN devices, rather than using a uniform cooling approach across the entire package.
3Reliability
If air-cavity configuration is used, then dielectric losses are reduced and electrical performance is improved, but thermal management complexity increases
Solution Approach 1:
The coined lid structure serves multiple functions simultaneously: it provides the air-cavity configuration for reduced dielectric losses, implements top-side cooling through heat spreaders, and offers mechanical protection for the devices. This multi-functionality reduces overall system complexity despite the advanced features.
Solution Approach 2:
The coined lid is constructed from composite materials that provide both the required electrical properties for air-cavity operation and the thermal conductivity necessary for effective heat spreading, combining multiple material functions in a single component.
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 design provides efficient top-side cooling and improved thermo-mechanical reliability, reducing thermal resistance and enhancing electrical performance at high frequencies by dissipating heat through a sealed air cavity and heat spreaders.
Implementation Method 1
The at least one heat spreader is positioned over, aligned with, and thermally coupled to the at least one flip-chip die
Implementation Method 2
the at least one heat spreader is formed from an engineered nano copper paste, which is capable of being customized in a coefficient of thermal expansion (CTE), in a range of 5-16 ppm
Data Source
AI summary
The present disclosure relates to an air-cavity package including a base assembly with a package substrate and a flip-chip die attached to the package substrate, and a coined lid over the base assembly and including a lid body and a heat spreader. The lid body includes a lid base and a lid wall protruding from a periphery of the lid base towards the package substrate. The heat spreader extends through the lid base, protrudes from the lid base towards the package substrate, and is positioned over, aligned with, and thermally coupled to the flip-chip die. A lid sealing component seals the lid wall to the package substrate. Herein, a recess, which is defined underneath the lid base, surrounding the heat spreader, and surrounded by the lid wall, and a gap surrounding the flip-chip die combine to form a sealed air cavity. The flip-chip die is encapsulated within the air cavity.