Flip Chip Pad Layout for Signal Routing and Parasitic Reduction
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Solution Overview
Problem
Conventional flip chip packaging is costly due to the high number of metal layers required for signal and power/ground routing, which introduces electrical parasitics and limits package performance.
Innovation Solution
The signal pads are arranged near the perimeter of the die, with power and ground pads located inboard, allowing for higher signal trace escape routing density and reducing the need for multiple metal layers and vias, thereby minimizing electrical parasitics and lowering production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional distributed pad layout is used, then signal routing flexibility is maintained, but substrate cost and manufacturing complexity increase due to multiple metal layers
Solution Approach 1:
The pad layout is segmented into two distinct functional zones: signal pads positioned at the die perimeter for direct edge routing, and power/ground pads positioned inboard for vertical via routing. This segmentation eliminates the need for complex multi-layer fan-out routing, reducing substrate complexity and cost.
Solution Approach 2:
The invention transitions from planar 2D routing to 3D routing by utilizing vias to route power and ground signals vertically beneath the die footprint. This dimensional change allows compact routing without requiring multiple lateral metal layers, simplifying substrate construction.
2Reliability
If multiple metal layers are used for fan-out routing, then signal escape routing is achieved, but electrical parasitics increase and performance deteriorates
Solution Approach 1:
The signal routing function is extracted from the multi-layer metal structure and implemented directly at the substrate edge through perimeter pad placement. This removes signal traces from the parasitic-prone multi-layer environment, eliminating unwanted inductance and capacitance while maintaining routing functionality.
Solution Approach 2:
Instead of routing signals from the die center outward through multiple layers (conventional approach), the invention inverts the approach by placing signal pads at the perimeter and routing directly to edges. This reversal eliminates the need for intermediate vias and layer transitions, reducing parasitic accumulation.
3Productivity
If signal pads are distributed throughout the die array, then functional integration is maintained, but routing density and escape routing efficiency decrease
Solution Approach 1:
Different regions of the die are assigned different pad types based on local routing requirements: perimeter regions accommodate signal pads for high-density edge routing, while inboard regions accommodate power and ground pads for vertical via routing. This localized optimization maximizes overall routing efficiency.
Data Source
AI summary
A flip chip interconnect pad layout has the die signal pads are arranged on the die surface near the perimeter of the die, and the die power and ground pads arranged on the die surface inboard from the signal pads; and has the signal pads on the corresponding package substrate arranged in a manner complementary to the die pad layout and the signal lines routed from the signal pads beneath the die edge away from the die footprint, and has the power and ground lines routed to vias beneath the die footprint. Also, a flip chip semiconductor package in which the flip chip interconnect pad layouts have the die signal pads situated in the marginal part of the die and the die power and ground pads arranged on the die surface inboard from the signal pads, and the corresponding package substrates have signal pads arranged in a manner complementary to the die pad layout and signal lines routed from the signal pads beneath the die edge away from the die footprint.