Flip-Chip Interposer Layout for Dense Wirebond Assemblies
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Solution Overview
Problem
Existing wirebonded chip-and-wire circuit assemblies face limitations in interconnection density and footprint due to the requirement of locating interconnection points only at the die perimeter, and upgrading to flip-chip dies is costly and incompatible with existing designs.
Innovation Solution
An interposer is used to adapt a flip-chip die for direct wirebond interconnection with surrounding wirebond dies, incorporating a flip-chip interconnection array on an insulating substrate with wirebond pads and SMT pads for increased interconnections and compatibility with existing chip-and-wire assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If wirebonding is used to connect dies, then interconnection points can be located at the die perimeter, but the number of interconnections is limited and footprint is inflated
Solution Approach 1:
The patent introduces an interposer as an intermediary component between the die and the substrate. This interposer contains an array of interconnection points that can be positioned close to the die, enabling a higher density of connections without increasing the die perimeter. The interposer acts as a mediator that decouples the connection density requirement from the die footprint constraint.
2Quantity of substance
If flip-chip dies are used, then interconnection density is increased, but manufacturing cost increases and compatibility with existing wirebonded assemblies is lost
Solution Approach 1:
The interposer is designed to provide multiple functions: it supports flip-chip die attachment with high-density interconnections while also providing wirebond pads for compatibility with existing wirebonded assembly processes. This multi-functionality allows the same interposer structure to accommodate both flip-chip and wirebond technologies, enabling gradual transition and mixed-technology assemblies.
3Ease of manufacture
If interconnection points are located only at the die perimeter, then wirebonding is simplified, but the number of available connection points is limited
Solution Approach 1:
The interposer transitions the interconnection geometry from a one-dimensional perimeter arrangement (on the die edge) to a two-dimensional array (on the interposer surface). This dimensional change allows connection points to be distributed across a larger area while maintaining proximity to the die, thereby increasing the number of available connection points without complicating the wirebonding process.
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 interposer increases interconnection density and high-frequency performance while reducing manufacturing costs by allowing flip-chip dies to be integrated into wirebonded assemblies, minimizing footprint and enabling simultaneous interconnections with both flip-chip and wirebond technologies.
Implementation Method 1
heating the flip-chip and interposer interconnection arrays of solder bump connection pads until they melt and form interconnections with each other
Implementation Method 2
forming a wirebond connection between the wirebond pad of the interposer and the wirebond interconnection point of the wirebond die by welding a first end of a wirebond to the wirebond interconnection point of the wirebond die and welding a second end of a wirebond to the wirebond pad of the interposer
Data Source
AI summary
An interposer that enables implementation of a flip-chip die in a wirebonded chip-and-wire circuit assembly includes an insulating substrate having a solder bump pad array on its upper surface that is compatible with the solder bump array of a flip-chip die. Wirebond pads provided along upper edges of the substrate are interconnected to at least some of the solder bump pads. Bonding the interposer to the circuit assembly housing floor, or through an opening to an underlying motherboard, places the wirebond pads proximate attachment points of adjacent wirebond dies, enabling wirebonding therebetween. Attachment pads on the interposer lower surface, in combination with interconnecting traces and vias, can enable connection directly through the housing opening to the underlying motherboard. Support components can be included within an edge cavity created beneath an overhang of a multi-layer substrate. A heat absorbing plate can be attached to the top of the flip-chip die.