Chip Package Ground Pad Interposed Between Signal Pads
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Solution Overview
Problem
As integrated circuits shrink and clock frequencies increase, cross-talk between signals becomes a significant issue due to the close proximity of pads and bonding wires, making it difficult to maintain sufficient separation distances and ensuring high performance while preventing signal interference.
Innovation Solution
The introduction of a chip package design that includes a ground pad interposed between different signal-transmitting pads to reduce cross-talk, along with a substrate with a ground layer and bonding wires, connectors, and via holes to electrically connect the pads and reduce signal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pads and bonding wires are placed close together to increase integration density, then the degree of integration is improved, but cross-talk between signals increases
Solution Approach 1:
A ground pad is introduced as an intermediary element between signal pads to reduce cross-talk. The ground pad acts as a mediator that shields adjacent signal pads from electromagnetic interference, allowing high integration density while maintaining signal integrity through the shielding effect of the ground reference.
Solution Approach 2:
The pad structure is designed with alternating signal and ground pads, creating local variations in pad function. This local quality differentiation allows specific regions to provide shielding while other regions transmit signals, resolving the contradiction between density and cross-talk reduction.
2Object-affected harmful factors
If separation distance between pads and bonding wires is increased to reduce cross-talk, then signal interference is reduced, but chip size increases
Solution Approach 1:
The ground pad serves as a shielding intermediary that reduces signal interference without requiring increased separation distances. By placing ground pads between signal pads, electromagnetic interference is blocked, maintaining signal integrity while preserving compact chip dimensions.
Solution Approach 2:
The solution transitions from solving the interference problem in the horizontal separation dimension to solving it in the vertical stacking dimension. Multiple pad layers are arranged in three-dimensional space, allowing signals to be routed through different vertical levels with ground shielding, thereby reducing interference without increasing horizontal chip area.
Data Source
AI summary
An image forming apparatus including an engine unit to perform an image forming operation, and a board unit to control the engine unit. The board unit includes at least one chip package that includes a chip. The chip includes first pads to transmit a first type of signal, a second pad to transmit a second type of signal, and a third pad interposed between the first and second pads, to reduce cross-talk between the first and second types of signals.