Circular Bond Finger Pads for Dense IC Package Wire Bonding
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Solution Overview
Problem
Conventional integrated circuit (IC) packages face issues with low Cu density in bond finger areas due to loose spacing design rules, leading to increased electrical resistance and difficulty in wire bonding, as well as warpage in printed circuit boards, due to the oblong shape of bond finger pads and their location near the edge of the substrate.
Innovation Solution
The introduction of circular, solder mask-defined (SMD) bond finger pads, which allows for reduced spacing between adjacent pads without the risk of shorts, enabling higher Cu density and shorter wire bonds by locating the pads closer to the memory die, thus reducing electrical resistance and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oblong bond finger pads with loose spacing design rules are used, then the risk of shorts between adjacent pads is reduced, but Cu density in the bond finger area decreases and electrical resistance increases
Solution Approach 1:
The patent applies spheroidality by changing the bond finger pad shape from oblong to circular. This geometric transformation allows pads to be placed closer together while maintaining adequate clearance, thereby increasing Cu density in the bond finger area without proportionally increasing the risk of shorts between adjacent pads.
2Ease of manufacture
If bond finger pads are located near the edge of the substrate for easier plating trace routing, then trace routing is simplified, but wire bond length increases and electrical resistance increases
Solution Approach 1:
The circular shape of the bond finger pads enables more flexible and efficient trace routing patterns. The symmetric geometry allows traces to approach the pads from multiple directions, facilitating optimized routing that can achieve both manufacturing ease and reduced wire bond lengths by positioning pads more centrally on the substrate.
3Quantity of substance
If circular SMD bond finger pads with tighter spacing are used, then Cu density increases and wire bond length decreases, but the risk of shorts between adjacent pads may increase
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the bond finger pads (circular shape, optimized diameter) and their spatial arrangement (spacing, positioning). These parameter optimizations allow tighter spacing that increases Cu density while maintaining adequate clearance to prevent shorts, achieving both higher density and reliability through carefully tuned geometric parameters.
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
The use of circular SMD bond finger pads increases metal density, reduces warpage, and decreases electrical resistance by allowing for shorter wire bonds and tighter spacing, improving the overall efficiency and reliability of IC packages.
Implementation Method 1
the traces are formed from electrolytic plating processes
Data Source
AI summary
Disclosed are examples of integrated circuit (IC) packages. Each IC package may include a flip-chip (FC) die on a substrate, a wire bond die above the FC die, a wire bond connected to the wire bond die, and a mold on the substrate and encapsulating the FC die, the wire bond die, and the wire bond. The substrate may include least a first metallization layer includes a first substrate layer, a trace on the first substrate layer and routed within the first metallization layer to electrically couple with one or more FC interconnects of the FC die, and a bond finger pad formed on the trace. The bond finger pad may be circular. The wire bond may electrically connect to the trace such that the wire bond die is electrically coupled with the FC die through the wire bond, the bond finger pad, and the trace.