Notched RDL Capture Pads for IC Die Connector Density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wafer chip scale package (WCSP) designs face limitations in increasing the number of bonding connectors on IC dies without enlarging the die size or requiring changes to die pad or I/O layouts, which can lead to issues like shorting and leakage between different nets.
Innovation Solution
The solution involves altering RDL designs by notching RDL capture pads near adjacent die pads, allowing metal bonding connectors to overhang and increase spacing, while sloping the edges of notched RDL capture pads and adjusting via positions to maintain reliability and avoid design rule violations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of bonding connectors is increased on the WCSP die, then the I/O connection capacity is improved, but the die size must be enlarged to accommodate additional connectors while maintaining clearance design rules
Solution Approach 1:
The RDL capture pad is segmented by introducing a notch that divides it into distinct regions. This segmentation allows the bonding connector to be positioned such that part of it overhangs the notched RDL capture pad, effectively reducing the space required per connector and enabling higher connector density without increasing die size.
Solution Approach 2:
The invention utilizes the vertical dimension by allowing the bonding connector to overhang the RDL capture pad in the lateral direction. This dimensional approach violates conventional ball-to-pad clearance rules by using the overhang configuration, thereby maximizing the use of available die area for accommodating more connectors.
2Quantity of substance
If the RDL capture pad is notched to allow bonding connector overhang, then the spacing between connectors can be reduced, but the reliability may be compromised due to potential shorting or leakage between different nets
Solution Approach 1:
The notch is strategically positioned to extract or remove the problematic overlapping region between the RDL capture pad and the adjacent die pad. This extraction creates sufficient lateral spacing that prevents electrical shorting or leakage between different nets, while still allowing the bonding connector to overhang and reduce overall die size.
Solution Approach 2:
The notched RDL capture pad acts as an intermediary structure that mediates between the bonding connector and the adjacent die pad. By creating the notch, it provides a transition zone that maintains proper electrical isolation while enabling the compact overhang configuration.
3Reliability
If conventional clearance design rules are maintained, then electrical isolation between nets is ensured, but the number of bonding connectors that can be fitted on the die is limited
Solution Approach 1:
Instead of maintaining conventional clearance rules that prevent overhang, the invention inverts the approach by deliberately designing the RDL capture pad with a notch that enables and controls the overhang configuration. This inversion of the traditional clearance concept allows bonding connectors to extend beyond the RDL capture pad boundary while maintaining electrical isolation through the notched geometry.
Data Source
AI summary
An IC die includes active circuitry and I/O nodes tied together in first net and at least a second net. A first die pad and a second die pad adjacent thereto are coupled to the first and second net, respectively. A redirect layer (RDL) coupled to the die pads over a first dielectric vias includes a first RDL trace lateral coupling the first die pad and first RDL pad and a second RDL trace coupling the second die pad and second RDL pad. The first RDL pad includes an RDL notch facing the second RDL trace. Under bump metallization (UBM) pads on a second dielectric include a first UBM pad coupled to the first RDL pad over a second dielectric via. A first metal bonding connector is on the first UBM pad. The first UBM pad or first metal bonding connector overhangs the first RDL pad over the notch.