Trimmed BGA Solder Pads for Differential Trace Routing
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Solution Overview
Problem
Existing ball grid array (BGA) packages face challenges in accommodating high-speed differential signaling traces due to inherent discrepancies in trace lengths and geometries, leading to signal noise and electromagnetic interference, which are exacerbated as signal speeds increase.
Innovation Solution
The solution involves trimming the perimeters of conductive pads in a BGA to create wider gaps between adjacent pads, allowing for improved spacing and flexibility in trace routing, enabling connections to internal pads and accommodating wider traces, thus minimizing trace discrepancies and reducing signal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conductive pads are arranged in a standard grid pattern with uniform spacing, then manufacturing is simplified, but trace routing flexibility is limited and trace length discrepancies increase
Solution Approach 1:
The patent applies asymmetry by modifying the perimeter of specific conductive pads from the standard grid pattern. Certain pads have non-uniform spacing and asymmetric shapes to create wider gaps in specific locations, enabling improved trace routing flexibility while maintaining overall grid structure for manufacturing simplicity
Solution Approach 2:
The patent implements local quality by applying perimeter modifications only to specific conductive pads where trace routing is needed, rather than changing the entire pad array. This allows localized optimization of trace paths and gap widths while preserving the standard grid pattern in other areas
2Ease of manufacture
If trace routing is constrained by uniform pad spacing, then manufacturing is easier, but trace length discrepancies and signal noise increase
Solution Approach 1:
The asymmetric perimeter modifications create non-uniform gap widths that allow differential trace pairs to be routed more equidistantly from their reference planes, reducing trace length discrepancies and signal noise while maintaining manufacturability
3Reliability
If conductive pads maintain full perimeter, then electrical connection area is maximized, but gap width between pads is reduced limiting wire routing
Solution Approach 1:
The patent selectively trims the perimeter of specific conductive pads where wire routing is required, while maintaining full perimeters on pads that do not require adjacent wire passage. This localized modification creates wider gaps for wire routing without compromising electrical connection area on critical pads
Solution Approach 2:
The conductive pad perimeter is segmented into retained portions and trimmed portions, allowing differential treatment of different pad regions to simultaneously satisfy electrical connection requirements and wire routing requirements
Data Source
AI summary
A passive circuit element is disclosed. The passive circuit element includes an array of conductive pads arranged on a substrate such that a gap is formed between each of the conductive pads. The passive circuit element further includes a first wire electrically connected to a first conductive pad of the array of conductive pads such that the first wire passes through a first gap formed between a second conductive pad and a third conductive pad. The passive circuit element further includes a second wire electrically connected to a fourth conductive pad of the array of conductive pads such that the second wire passes through the first gap. At least one of the second and third conductive pads has a substantially planar side facing toward the first gap.