Bottom Package Metal Post Interconnections
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bottom package substrates with solder balls or interconnect bars require large footprints due to interconnect pitch limitations, leading to decreased density and increased costs, especially when supporting fine-pitch dies and their associated interconnections.
Innovation Solution
The use of plated metal posts on a redistribution layer (RDL) for interconnections between the bottom package substrate and a top package, eliminating the need for a keep-out area and reducing the footprint, as these posts are plated directly on a seed layer overlaying the RDL before die attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional solder balls or interconnect bars are used for bottom package interconnections, then electrical connectivity is achieved, but the footprint becomes excessively large due to interconnect pitch limitations and keep-out distance requirements
Solution Approach 1:
The patent transitions from planar interconnect arrangements (solder balls on the periphery) to vertical plated metal posts that extend through the substrate thickness. This dimensional change allows interconnections to be formed in the vertical dimension rather than requiring excessive horizontal space, thereby reducing footprint while maintaining electrical connectivity.
Solution Approach 2:
The patent merges the formation of plated metal posts with the existing substrate manufacturing process by depositing metal layers directly onto the substrate surface during fabrication. This eliminates the need for separate interconnect bar manufacturing and laser drilling processes, reducing both footprint and manufacturing complexity.
2Area of stationary object
If an interposer includes a perimeter for conventional PoP solder ball interconnections, then solder balls can be attached, but the interposer footprint becomes excessive to support both dies and solder balls with required keep-out distance
Solution Approach 1:
The patent replaces peripheral solder ball interconnections with vertical plated metal posts that extend through the interposer substrate. This eliminates the need for perimeter keep-out zones and allows the interposer footprint to be optimized for die placement only, significantly reducing the required area.
Solution Approach 2:
The plated metal posts are formed during the interposer manufacturing process before die attachment, integrating the interconnect structure creation into the substrate fabrication sequence. This preliminary formation eliminates subsequent laser drilling and interconnect bar attachment steps.
3Strength
If solder balls are made relatively large to couple to the upper package, then mechanical strength is improved, but the interconnect pitch must increase, requiring a larger interposer footprint
Solution Approach 1:
The patent transitions from lateral solder ball interconnections to vertical plated metal posts. The mechanical strength is achieved through the vertical extent and cross-sectional area of the plated posts rather than through lateral diameter, allowing smaller pitch while maintaining strength.
Solution Approach 2:
The patent changes the geometric parameters of the interconnect structure by using plated metal posts with controlled cross-sectional dimensions and vertical height. This allows optimization of both mechanical strength and pitch density independently, unlike solder balls where strength and pitch are coupled through diameter.
4Area of stationary object
If laser drilling is used to expose encased solder balls, then interconnections are created, but the heat from the laser requires a keep-out distance that increases footprint
Solution Approach 1:
The plated metal posts are formed during the interposer manufacturing process before die attachment and molding, eliminating the need for subsequent laser drilling to expose interconnections. The interconnect structure is already in place and accessible after molding.
Solution Approach 2:
The patent extracts the harmful thermal process (laser drilling) from the manufacturing sequence by forming interconnections through plating rather than drilling. This eliminates the heat-induced keep-out distance requirement entirely.
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
This approach enhances density and reduces manufacturing costs by eliminating the need for laser drilling and separate interconnect bar manufacturing, allowing for more compact and efficient packaging without compromising electrical connectivity.
Implementation Method 1
The plated metal posts enable a reduced footprint for the bottom package as compared to conventional bottom packages that use solder balls or interconnect bars to form the interconnections to an upper package or additional die. The bottom package includes a bottom package substrate supporting one or more dies.
Implementation Method 2
both the metal posts and the die interconnects are plated onto a seed layer overlaying the RDL
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A bottom package substrate is provided that includes a plurality of metal posts that electrically couple through a die-side redistribution layer to a plurality of die interconnects. The metal posts and the die interconnects are plated onto a seed layer on the bottom package substrate.