RF Module Layout With Dual Heat Paths and Shorter Signal Lines
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Solution Overview
Problem
Existing radio-frequency modules face challenges in achieving high power output and reducing signal transfer loss, especially at high operating frequencies, due to heat management issues and inefficient heat dissipation in semiconductor devices like HBTs, leading to thermal runaway and increased signal loss.
Innovation Solution
The radio-frequency module design incorporates a semiconductor device with a first member made of an elemental semiconductor and a second member made of a compound semiconductor, featuring conductive protrusions for enhanced heat transfer and a configuration where the semiconductor device is in close proximity to the output matching circuit and band selection switch, forming multiple heat transfer paths and reducing signal transfer lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the semiconductor device is positioned closer to the output matching circuit and band selection switch, then signal transfer loss is reduced, but heat dissipation becomes more difficult
Solution Approach 1:
The patent utilizes the vertical stacking dimension to resolve the contradiction. The semiconductor device is positioned in the third dimension (vertical stacking) rather than being constrained to planar proximity, allowing signal paths to be shortened through vertical connections while heat can be dissipated through the substrate in the vertical direction. This dimensional transition enables both low signal loss and effective thermal management.
Solution Approach 2:
The module substrate serves as an intermediary that facilitates both electrical connection and thermal management. The substrate provides conductive pathways for RF signals while simultaneously acting as a heat sink with thermal vias and ground planes that conduct heat away from the semiconductor device, decoupling the signal integrity function from the thermal management function.
2Reliability
If high power output is achieved through improved heat release characteristics, then thermal runaway is avoided, but device complexity increases
Solution Approach 1:
The module substrate performs multiple functions simultaneously: it provides mechanical support, electrical grounding, RF signal routing, and thermal management through integrated ground planes and thermal vias. This multi-functionality reduces the need for separate dedicated heat sinking components, thereby limiting device complexity while achieving reliable thermal runaway prevention.
Solution Approach 2:
The patent combines the heat transfer path with the existing RF signal path and grounding structure. Thermal vias are integrated into the same substrate layers that carry RF signals and ground connections, merging the thermal management function with the electrical function. This integration avoids adding separate complex heat transfer mechanisms while achieving effective thermal runaway prevention.
3Temperature
If the semiconductor device is stacked on the module substrate with conductive protrusions, then heat transfer efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The conductive protrusions (thermal vias) are pre-formed in the module substrate during substrate fabrication before the semiconductor device is mounted. This preliminary action ensures that the thermal pathways are already in place and precisely positioned, eliminating the need for post-assembly alignment operations and reducing manufacturing precision requirements during the device mounting process.
Solution Approach 2:
The conductive protrusions are nested within the substrate structure itself, with thermal vias formed through the substrate layers. This nesting approach integrates the heat transfer path into the substrate's internal structure rather than requiring external alignment features, thereby reducing manufacturing complexity and precision requirements while maintaining effective thermal coupling.
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 design improves heat dissipation from semiconductor devices, reduces signal transfer loss, and enables more efficient performance by shortening transfer lines and utilizing multiple heat transfer paths, thereby addressing thermal runaway and signal loss issues.
Implementation Method 1
Two heat transfer paths are formed; one is a heat transfer path from the semiconductor element included in the radio-frequency amplifier circuit of the second member to the first member; and the other is a heat transfer path from the semiconductor element to the module substrate via the conductive protrusion
Data Source
AI summary
A semiconductor device including a radio-frequency amplifier circuit and a band selection switch are mounted on or in a module substrate. An output matching circuit includes at least one passive element disposed on or in the module substrate. The output matching circuit is coupled between the radio-frequency amplifier circuit and the band selection switch. The semiconductor device includes a first member having a semiconductor portion made of an elemental semiconductor and a second member joined to the first member in surface contact with the first member. The radio-frequency amplifier circuit including a semiconductor element made of a compound semiconductor is formed at the second member. The semiconductor device is disposed in close proximity to the output matching circuit in plan view. The output matching circuit is disposed in close proximity to the band selection switch.