Via-on-Pad Interposer for PoP Bridging
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Solution Overview
Problem
Conventional Package-on-Package (PoP) processes face limitations due to large solder balls, which restrict the number and spacing of solder balls, leading to bridging issues and inefficiencies in integrating packages with mismatched thermal expansion coefficients.
Innovation Solution
The proposed solution involves embedding a device die in a through-opening of an interposer with conductive pipes and metal pads, allowing for smaller solder regions and improved routing of Redistribution Lines (RDLs), and using vias that overlap conductive pipes to reduce solder region size and prevent bridging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If large solder balls are used to provide adequate space for device die, then the device die can be accommodated, but the number of solder balls is limited and bridging occurs
Solution Approach 1:
The patent transitions from planar solder ball connections to three-dimensional via-in-pad connections, where vias penetrate through the package substrate to establish vertical electrical connections. This dimensional change allows solder regions to be positioned directly over pad openings, eliminating the need for large lateral spacing between solder elements and enabling higher density interconnections.
Solution Approach 2:
The patent implements a nested structure where vias are formed within pad regions, and solder regions are positioned within via openings. This nesting approach allows multiple functional elements (via, pad, solder region) to occupy the same lateral footprint, maximizing space utilization and enabling smaller pitch configurations without bridging.
2Volume of moving object
If large solder balls are used, then adequate space for device die is provided, but the distance between neighboring solder balls must be increased to prevent bridging
Solution Approach 1:
The patent moves the connection geometry from a lateral arrangement to a vertical arrangement by implementing through-substrate vias. This allows solder regions to connect pads on opposite sides of the substrate without requiring large lateral distances, as the electrical connection is established through the thickness of the substrate rather than across its surface.
Solution Approach 2:
The via structure acts as an intermediary element that bridges the pad on the first side of the substrate to the corresponding pad on the second side. This intermediary via allows compact lateral spacing while maintaining reliable electrical connection, as the via provides a controlled pathway through the substrate material.
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 package integration, reduces thermal warpage, increases assembly yield, and improves reliability in temperature and drop tests by allowing smaller solder pitches without bridging, while efficiently using interposer area for routing.
Implementation Method 1
A solder region bonds the top package to the conductive pipe, wherein the solder region extends into the opening in the conductive pipe
Data Source
AI summary
An interposer includes a core dielectric material, a conductive pipe penetrating through the core dielectric material, and a metal pad underlying the conductive pipe. The metal pad includes a center portion overlapped by a region encircled by the conductive pipe, and an outer portion in contact with the conductive pipe. A dielectric layer is underlying the core dielectric material and the metal pad. A via is in the dielectric layer, wherein the via is in physical contact with the center portion of the metal pad.