Chips-First Multichip Module for Compact RF Systems
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Solution Overview
Problem
Conventional electronic packaging methods face challenges in providing high performance, compact size, and mechanical rigidity for multichip modules, particularly in cell phone systems, due to issues like cross-talk between RF and digital components, heat management, and the cost of repairing defective modules.
Innovation Solution
The development of a chips-first multichip module structure with a chip layer surrounded by structural material, featuring conductive structures, interconnect and redistribution layers, and input/output contacts, which allows for direct chip-to-chip connections and the integration of heat management and shielding within a compact package.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional packaging methods with individual IC chips are used, then ease of manufacture is maintained, but module size increases and interconnect density decreases
Solution Approach 1:
The module is segmented into multiple functional layers: chip layer, structural material layer, conductive structures layer, interconnect layer, and redistribution layer. Each layer performs a specific function, allowing for compact integration while maintaining manufacturing feasibility through standardized layer-by-layer fabrication processes
Solution Approach 2:
Multiple functional elements are nested within the module structure: chips are embedded in structural material, conductive structures extend through the material, interconnect layers are disposed over chip surfaces, and redistribution layers connect to input/output contacts. This nesting achieves high interconnect density in a compact volume
2Speed
If long pins and large conductor runs are used in packages, then ease of manufacture is improved, but speed performance deteriorates due to loading capacitance and inductance
Solution Approach 1:
The interconnect structure transitions from two-dimensional planar traces to three-dimensional vertical conductive structures extending through the structural material. This dimensional change reduces conductor run lengths and enables direct chip-to-chip connections, improving speed while managing complexity through vertical integration
Solution Approach 2:
Conductive structures act as intermediary elements that extend through the structural material to provide electrical connections between chips. These intermediaries reduce the effective length of signal paths and minimize loading capacitance and inductance compared to conventional long pin connections
3Length of stationary object
If chips-first technology is used to minimize size and provide high performance interconnect, then module thickness is reduced, but mechanical rigidity and protection are insufficient for automated assembly
Solution Approach 1:
The structural material serves multiple functions simultaneously: it provides mechanical support and rigidity to the thin module, protects embedded chips from damage, enables automated assembly handling, and facilitates heat dissipation. This multi-functionality allows thickness reduction without sacrificing strength
Solution Approach 2:
The module employs composite construction with chips embedded in structural material, followed by additional protective and functional layers. This composite structure achieves the required mechanical rigidity and protection in a thin profile suitable for automated assembly
4Temperature
If heat sink is added to manage heat from power amplifier, then heat dissipation is improved, but package thickness increases unacceptably
Solution Approach 1:
The heat dissipation function is extracted from the conventional bottom-mounted heat sink and integrated directly into the module structure through thermally conductive structural material and dedicated thermal pathways. This extraction eliminates the need for a separate thick heat sink component
Solution Approach 2:
Heat dissipation transitions from a three-dimensional external heat sink structure to integrated thermal pathways within the module's planar layers. Thermal conduction occurs through the structural material and conductive structures in the same horizontal plane, avoiding vertical thickness increase
5Object-affected harmful factors
If individual shield shells are placed around cross-talking components in circuit board versions, then cross-talk is reduced, but device complexity and size increase
Solution Approach 1:
Individual shield shells around components are merged into a unified shielding architecture where the structural material and conductive structures provide integrated electromagnetic shielding for the entire module. This consolidation reduces cross-talk between RF and digital components while simplifying the shielding structure
Solution Approach 2:
The structural material and conductive structures serve dual functions: providing mechanical support and electrical interconnection while simultaneously providing electromagnetic shielding. This multi-functionality reduces cross-talk without adding separate shielding components
Data Source
AI summary
Circuit structures and methods of fabrication are provided for facilitating implementing a complete electronic system in a compact package. The circuit structure includes, in one embodiment, a chips-first multichip base layer with conductive structures extending therethrough. An interconnect layer is disposed over the front surface of the multichip layer and includes interconnect metallization electrically connected to contact pads of the chips and to conductive structures extending through the structural material. A redistribution layer, disposed over the back surface of the multichip layer, includes a redistribution metallization also electrically connected to conductive structures extending through the structural material. Input/output contacts are arrayed over the redistribution layer, including over the lower surfaces of at least some integrated circuit chips within the multichip layer, and are electrically connected through the redistribution metallization, conductive structures, and interconnect metallization to contact pads of the integrated circuit chips of the multichip layer.