Silicon Nitride LGA Pad Structure for Lower Insertion Loss
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Solution Overview
Problem
The reduction in size of mobile electronic devices necessitates increased LGA surface mount technology density while minimizing insertion loss, which is hindered by stress buildup and capacitance issues in legacy LGA pads.
Innovation Solution
A layer of silicon nitride is introduced between the LGA pad and the dielectric layer, providing mechanical stability and reducing capacitance by extending beyond the pad's edge, thus alleviating stress and fatigue, and featuring a higher dielectric constant than the surrounding dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the LGA pad footprint is reduced to increase surface mount density, then device size is reduced, but stress buildup and capacitance increase causing insertion loss
Solution Approach 1:
A silicon nitride layer is introduced as an intermediary between the copper pad and the dielectric layer. This intermediate layer serves multiple functions: it provides mechanical support to reduce stress buildup on the reduced footprint pad, and its higher dielectric constant reduces capacitance between the pad and surrounding structures, thereby reducing insertion loss while maintaining the reduced pad size
Solution Approach 2:
The patent changes the dielectric parameter by introducing silicon nitride material with a higher dielectric constant between the pad and dielectric. This parameter change reduces the capacitance formed between the pad and surrounding conductive structures, directly addressing the insertion loss issue that arises from reduced pad footprint
2Productivity
If the LGA pad footprint is reduced, then surface mount density increases, but mechanical stability and stress resistance deteriorate
Solution Approach 1:
The silicon nitride layer is applied locally beneath the copper pad and extends beyond its edges, providing targeted mechanical support exactly where the reduced footprint pad is most vulnerable to stress and fatigue. This localized reinforcement maintains mechanical stability without requiring an overall increase in pad size
3Reliability
If a silicon nitride layer is added between the pad and dielectric, then mechanical stability and insertion loss improve, but device complexity increases
Solution Approach 1:
The silicon nitride layer performs multiple functions simultaneously: it provides mechanical support to prevent stress cracks, reduces capacitance to minimize insertion loss, and can serve as part of the overall dielectric structure. This multi-functionality justifies the added layer by delivering multiple benefits from a single structural addition
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 configuration reduces insertion loss, enhances mechanical stability, and prevents cracking, allowing for a reduced LGA pad footprint without compromising electrical connections.
Implementation Method 1
the layer of silicon nitride may provide a stress relief layer that facilitates additional mechanical stability to prevent cracks or fatiguing from developing at or near the edge of the LGA pad
Implementation Method 2
The layer of silicon nitride may include Si3N4, or other similar stoichiometries, that enables the layer of silicon nitride to have a higher dielectric constant (Dk), as compared to the Dk of a dielectric that may partially surround the layer of silicon nitride
Data Source
AI summary
Embodiments herein relate to systems, apparatuses, or processes directed to forming an LGA pad on a side of a substrate, with a layer of silicon nitride between the LGA pad and a dielectric layer of the substrate. The LGA pad may have a reduced footprint, or a reduced lateral dimension with respect to a plane of the substrate, as compared to legacy LGA pads to reduce insertion loss by reducing the resulting capacitance between the reduced LGA footprint and metal routings within the substrate. The layer of silicon nitride may provide additional mechanical support for the reduced footprint. Other embodiments may be described and/or claimed.