Embedded Die Contact Finish Using Indium-Palladium-Gold Barriers
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Solution Overview
Problem
Embedding circuit components within package substrates is challenging due to thickness mismatches leading to tilting or shifting, and existing surface finishes for conductive contacts in integrated circuit packages face issues like copper diffusion, formation of brittle inter-metallic compounds, and oxidation, which affect solder joint reliability and maximum current limits.
Innovation Solution
Implementing surface finishes such as ENEPIG, IGEPIG, or alternative layers like indium or cobalt-iron with palladium and gold to address these issues, ensuring better solder joint reliability and maximum current performance while reducing the formation of brittle inter-metallic compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional surface finishes are used on conductive contacts, then copper diffusion and oxidation are prevented, but brittle inter-metallic compounds form and solder joint reliability decreases
Solution Approach 1:
The patent introduces an intermediary layer of nickel or nickel alloy between the copper conductive contact and the solder joint. This intermediary layer prevents direct interaction between copper and tin that would form brittle Cu6Sn5 inter-metallic compounds, while also preventing copper oxidation. The nickel layer acts as a mediator that improves solder joint reliability without introducing brittleness.
Solution Approach 2:
The patent employs composite surface finish structures consisting of multiple layers with different properties. The nickel or nickel alloy layer combined with selective soldering creates a composite system where the nickel layer provides diffusion barrier and oxidation protection, while the solder layer provides mechanical bonding, together achieving reliable joints without brittle inter-metallic formation.
2Ease of manufacture
If embedded components are attached to package substrate, then integration is achieved, but thickness mismatches cause tilting or shifting
Solution Approach 1:
The patent modifies the surface finish parameters on the conductive contacts, specifically controlling the thickness and composition of nickel and palladium layers. By optimizing these parameters, the surface finish compensates for thickness mismatches between embedded components and package substrate, ensuring proper alignment and preventing tilting or shifting during attachment.
3Reliability
If copper conductive contacts are exposed, then electrical connectivity is achieved, but oxidation and copper diffusion occur
Solution Approach 1:
The patent uses nickel and palladium layers as intermediary barrier layers between the copper conductive contact and the external environment. The nickel layer provides the primary diffusion barrier against copper oxidation and migration, while the palladium layer provides additional protection and solderability. This multi-layer intermediary structure effectively prevents harmful copper diffusion and oxidation while maintaining electrical connectivity.
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 proposed surface finishes provide improved solder joint reliability, reduced formation of brittle inter-metallic compounds, and enhanced wettability, leading to cost-effective and efficient integration of embedded interconnect bridge circuitry dies in integrated circuit packages.
Implementation Method 1
An electrolytic indium-palladium-gold surface finish is formed over the conductive contact
Implementation Method 2
An electrolytic indium-palladium-gold surface finish is formed over the conductive contact to prevent copper diffusion and oxidation
Implementation Method 3
The proposed surface finishes provide improved solder joint reliability, reduced formation of brittle inter-metallic compounds
Data Source
AI summary
In embodiments herein, a surface finish (SF) is formed on conductive contacts of a package substrate for connection to an embedded interconnect bridge circuitry die. In some embodiments, the SF may be electroless nickel-electroless palladium-immersion gold (ENEPIG). In other embodiments, the SF may be immersion gold-electroless palladium-immersion gold (IGEPIG). In other embodiments, the SF may include a layer of electrolytic palladium-gold on a layer of indium or on a layer of cobalt-iron.