Package-on-Package Interposer with Moldable Underfill for Bridging Prevention
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving high integration density and efficient vertical interconnections in package-on-package structures, particularly in reducing interconnection pitch and preventing bridging between conductive pillars, while maintaining reliable electrical connectivity.
Innovation Solution
The use of conductive pillars with a specific pitch and shape between a lower substrate and an interposer, along with an interposer having a different pitch for mounting additional packages, allows for closer pillar spacing and direct alignment over dies, reducing bridging and increasing connection density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conductive pillars with smaller pitch are used to increase connection density, then the number of connections increases, but the risk of solder bridging between pillars increases
Solution Approach 1:
The invention divides the interconnection function into two separate components: conductive pillars for electrical connection and moldable underfill for spacing and support. This segmentation allows the pillars to be placed closer together (reducing pitch) while the underfill material physically separates them to prevent solder bridging, thus resolving the contradiction between increasing connection density and preventing solder defects
Solution Approach 2:
The moldable underfill acts as an intermediary material between adjacent conductive pillars. It provides mechanical support and maintains precise spacing between pillars during the soldering process, enabling closer pillar placement without increasing the risk of solder bridging. This intermediary element allows the system to achieve both high connection density and reliable solder joint formation
2Quantity of substance
If interconnection pitch is reduced to increase integration density, then more connections fit in given area, but manufacturing precision requirements increase
Solution Approach 1:
The moldable underfill material provides self-aligning and self-spacing functionality during the packaging process. As the underfill is molded around the conductive pillars, it automatically maintains consistent spacing between them, reducing the need for highly precise external positioning equipment and processes. This self-service mechanism enables reduced pitch while maintaining manufacturing feasibility
Solution Approach 2:
The conductive pillars are pre-positioned and secured with moldable underfill before the final soldering process. This preliminary action establishes precise pillar spacing and alignment in advance, ensuring that subsequent soldering operations can proceed with relaxed precision requirements. The underfill acts as a pre-formed template that guides the entire manufacturing process
Data Source
AI summary
A device comprises a substrate having a die mounted on the first side of the substrate and a moldable underfill (MUF) disposed on the first side of the substrate and around the die. An interposer is mounted on the first side of the substrate, with the interposer having lands disposed on a first side of the interposer. The interposer mounted to the substrate by connectors bonded to a second side of the interposer, the connectors providing electrical connectivity between the interposer and the substrate. A package is mounted on the first side of the interposer and is electrically connected to the lands. At least one of the lands is aligned directly over the die and wherein a pitch of the connectors is different than a pitch of the lands.