Electroplated Underfill Barrier for Denser Die Packaging
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Solution Overview
Problem
In the packaging of integrated circuit dies, underfill material tends to flow away from the die site, leading to increased substrate size due to the need for keep out zones (KOZs) to prevent underfill from encroaching on die side components.
Innovation Solution
The implementation of raised metal barriers surrounding die sites serves as an underfill containment barrier, effectively reducing the need for KOZs by keeping the underfill closer to the die sites, and allowing for a reduction in plated copper thickness on edge bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If underfill material is applied as liquid to provide mechanical connection and thermal management, then the mechanical strength and heat dissipation are improved, but the underfill flows away from die site causing increased substrate size due to keep out zones
Solution Approach 1:
A hydrophobic barrier layer is introduced as an intermediary between the underfill material and the substrate surface. This barrier layer has low surface energy that repels the underfill, preventing it from flowing beyond the die site while still allowing the underfill to provide its mechanical and thermal functions within the intended area.
Solution Approach 2:
A thin film barrier layer is applied to the substrate surface in the keep out zone area. This thin film provides a flexible, continuous barrier that contains the underfill material without requiring rigid structural modifications to the substrate, thus maintaining substrate flexibility while preventing underfill migration.
2Reliability
If keep out zones are enlarged to prevent underfill from encroaching on die side components, then component placement reliability is improved, but package space is reduced
Solution Approach 1:
The hydrophobic barrier layer acts as a mediator that allows smaller keep out zones to suffice for reliable component placement. By providing molecular-level underfill repulsion at the barrier interface, components can be placed closer to the die site without risk of underfill encroachment, thus reducing the required keep out zone area while maintaining placement reliability.
3Reliability
If plated copper thickness on edge bumps is increased to ensure electrical connection, then electrical reliability is improved, but copper material usage and manufacturing complexity increase
Solution Approach 1:
The hydrophobic barrier layer serves as a mediator that prevents underfill from reaching and disrupting the plated copper structures on edge bumps. This protection allows the use of thinner, more uniform copper plating without compromising electrical connection reliability, as the barrier shields the copper from underfill-induced stress and corrosion.
Data Source
AI summary
An apparatus is provided which comprises: a substrate, a die site on the substrate to couple with a die, a die side component site on the substrate to couple with a die side component, and a raised barrier on the substrate between the die and die side component sites to contain underfill material disposed at the die site, wherein the raised barrier comprises electroplated metal. Other embodiments are also disclosed and claimed.