Stepped Package Recessed Circuit Board Signal Integrity
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Solution Overview
Problem
High-frequency input/output signals face signal integrity and electromagnetic compatibility issues due to the use of plated-through-hole vias in circuit boards, which lead to noise reflections and excessive crosstalk, making it difficult to route high-speed signals effectively without consuming the top conductive layer and creating electromagnetic interference problems.
Innovation Solution
A stepped package with multiple conductive contacts and solder balls at varying heights is used, allowing direct connection to internal circuit board layers without plated-through-hole vias, reducing signal path length and eliminating stubs, thereby improving signal integrity and enabling higher speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plated-through-hole vias are used to route high-frequency signals, then signal routing is achieved, but signal integrity deteriorates due to noise reflections and crosstalk
Solution Approach 1:
The package is divided into multiple stepped portions at different heights, with conductive contacts and solder balls arranged at varying elevations. This segmentation allows different signal groups to be routed at different heights, enabling direct connection to internal circuit board layers without requiring plated-through-hole vias, thereby eliminating stubs and reducing noise reflections and crosstalk
Solution Approach 2:
The invention transitions from a traditional planar routing approach to a three-dimensional stepped structure. By adding the height dimension with multiple levels of conductive contacts and solder balls, signals can be routed directly to internal layers without passing through the entire board thickness via plated-through-hole vias, thus reducing signal path length and eliminating harmful reflections
2Speed
If top conductive layer is consumed for signal routing, then high-speed signals can be routed, but electromagnetic compatibility deteriorates due to excessive crosstalk
Solution Approach 1:
The package structure is segmented into multiple stepped portions with conductive contacts and solder balls at different heights. This allows high-speed signals to be routed through internal circuit board layers via direct connections, separating them from the top conductive layer. This segmentation reduces electromagnetic interference and crosstalk by distributing signals across multiple vertical levels rather than concentrating them on a single plane
Solution Approach 2:
The stepped package structure with multiple levels of solder balls acts as an intermediary between the package and the circuit board. This intermediate structure enables direct connection to internal layers, mediating the signal path to avoid using the top conductive layer for high-speed routing, thereby reducing electromagnetic interference
3Reliability
If stepped package structure is implemented, then signal integrity improves by eliminating plated-through-hole vias, but package complexity increases
Solution Approach 1:
The invention merges the package structure with the circuit board mounting structure by integrating multiple stepped portions directly into the package body. The conductive contacts and solder balls are combined into a unified stepped architecture that performs both mechanical support and electrical connection functions, reducing the need for separate plated-through-hole vias and associated complex routing
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
An apparatus comprising a package comprising a first side to interface with at least one chip; and a second side to interface with a circuit board, the second side opposite to the first side, wherein the second side comprises a non-stepped portion comprising a first plurality of conductive contacts; and a stepped portion that protrudes from the non-stepped portion, the stepped portion comprising a second plurality of conductive contacts.