LGA Module RF Pad Design for Impedance Continuity
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Solution Overview
Problem
The compact size of Land Grid Array (LGA) modules limits the space for antennas, leading to challenges in interconnecting them effectively with the motherboard, resulting in impedance discontinuity and poor impedance consistency across various frequency bands due to high parasitic capacitance from large non-radio frequency pads.
Innovation Solution
The solution involves using smaller radio frequency pads on the LGA module's bottom surface connected to corresponding pads on the motherboard, with non-radio frequency pads of larger size to reduce parasitic capacitance and improve impedance continuity, allowing for efficient transmission of radio frequency signals without occupying top surface space, thereby increasing effective layout space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large non-radio frequency pads are used for connection, then mechanical strength and soldering reliability are improved, but parasitic capacitance increases causing impedance discontinuity and poor impedance consistency
Solution Approach 1:
The patent applies different pad size specifications for different functional requirements: radio frequency pads are designed with smaller sizes (0.4mm-1.2mm length, 0.4mm-0.8mm width) to minimize parasitic capacitance and maintain impedance consistency, while non-radio frequency pads use larger sizes for adequate mechanical strength and soldering reliability. This local differentiation of pad qualities resolves the contradiction between mechanical reliability and electrical performance.
2Ease of operation
If SMA connector is disposed on top surface of LGA module, then antenna connection is enabled, but effective layout space is reduced
Solution Approach 1:
The patent moves the radio frequency pad connection interface from the top surface to the bottom surface of the LGA module. The radio frequency pad is disposed on the bottom surface to connect to the motherboard, eliminating the need for an SMA connector on the top surface. This dimensional relocation resolves the contradiction by enabling antenna connection functionality while preserving top surface layout space.
3Power
If radio frequency pad size is increased to improve signal transmission, then signal strength is improved, but parasitic capacitance increases causing impedance discontinuity
Solution Approach 1:
The patent optimizes the radio frequency pad dimensions to specific ranges (length: 0.4mm-1.2mm, width: 0.4mm-0.8mm) that balance signal transmission capability with parasitic capacitance control. By carefully selecting pad size parameters within these ranges, the patent achieves adequate signal strength while maintaining impedance consistency across frequency bands, resolving the contradiction between signal power and parasitic capacitance.
Data Source
AI summary
An electronic apparatus and a land grid array LGA module. The electronic apparatus includes: a first printed circuit board, a lower surface of the first printed circuit board is provided with a first radio frequency pad and a first non-radio frequency pad; a motherboard, including a second printed circuit board, where an upper surface of the second printed circuit board is provided with a second radio frequency pad and a second non-radio frequency pad, the first radio frequency pad is connected to the second radio frequency pad, and the first non-radio frequency pad is connected to the second non-radio frequency pad; an antenna, located on the motherboard and connected to the second radio frequency pad, the first radio frequency pad and the second radio frequency pad are configured to transmit, between the LGA module and the motherboard, a radio frequency signal transmitted by the antenna.