PCB Land Pattern for Ball Grid Array Mounting
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Solution Overview
Problem
Current printed circuit board structures, including dog bones, limit the dense mounting of surface mount devices and hinder their placement in inaccessible locations due to parasitic inductance, resistance, or capacitance issues.
Innovation Solution
A printed circuit board structure featuring adjacent, opposed lands with solder pads directly contacting annular pads of vias, allowing for tighter spacing and diagonal mounting of surface mount devices, reducing parasitic effects by eliminating the characteristic distance between devices and vias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional dog bone structures are used for connecting vias to components, then the PCB structure is simple and easy to manufacture, but the mounting density of surface mount devices is limited and parasitic effects increase
Solution Approach 1:
The patent merges the via pad and the land into a single integrated structure. The annular pad of the via is directly formed as part of the land, eliminating the need for separate dog bone structures. This integration allows surface mount devices to be mounted directly on the via pads, significantly increasing mounting density while reducing the number of discrete structural elements.
Solution Approach 2:
The patent utilizes the vertical dimension by allowing surface mount devices to be mounted on both sides of the PCB. The through-hole via structure enables electrical connection between top and bottom layers, while the land pattern allows component mounting on either face, effectively using the third dimension to increase overall mounting capacity.
2Productivity
If surface mount devices are placed closer to vias to improve density, then mounting density increases, but parasitic inductance, resistance, or capacitance increases
Solution Approach 1:
The patent applies different geometric characteristics to different parts of the land structure. The annular via pad provides a large surface area for low-inductance connection to the via, while the extended land portion provides adequate soldering area. This local optimization of geometry reduces parasitic effects in critical areas while maintaining functionality in other areas.
Solution Approach 2:
The patent changes the geometric parameters of the land structure, specifically using an annular shape for the via pad portion and extending it to form a larger land area. This parameter optimization reduces the inductance of the connection path while providing sufficient area for soldering, thereby reducing parasitic effects even at close spacing.
3Object-affected harmful factors
If inaccessible locations on the PCB are used for mounting surface mount devices, then proximity to other components improves and parasitic effects reduce, but the complexity of land patterns increases
Solution Approach 1:
The patent creates a universal land structure that can be used in any location on the PCB, whether accessible or inaccessible. The integrated annular pad and land design works the same way regardless of position, allowing standardization of the structure across the entire board while enabling placement in previously inaccessible areas for improved performance.
Data Source
AI summary
A printed circuit board for a surface mount device (SMD) is provided. The printed circuit board includes adjacent, opposed first and second lands on a face of the printed circuit board, the first land comprising a first solder pad contacting or merged with a first annular pad of a first via, the second land comprising a second solder pad contacting or merged with a second annular pad of a second via, arranged for solder mounting a surface mount device to the first and second solder pads.