Underfill Containment Barrier for Smaller Package Keep-Out Zones
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Solution Overview
Problem
The existing methods for attaching an integrated circuit die to a package substrate result in the underfill material flowing away from the die site, necessitating larger keep out zones (KOZs) to prevent stress on solder joints, which increases substrate size and is inefficient in space usage.
Innovation Solution
The implementation of raised metal barriers around die sites to contain the underfill material closer to the die, reducing the need for larger KOZs and allowing for uniform copper thickness in bump fields, achieved through electroplating and surface routing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underfill material is applied to distribute thermal expansion mismatch, then solder joint reliability is improved, but underfill flows away from die site requiring larger keep out zones which increases substrate size
Solution Approach 1:
The substrate surface is segmented into distinct regions: die sites where underfill is contained, keep out zones with reduced dimensions, and die side component sites. This segmentation allows underfill to be confined to specific areas while enabling component placement in other areas, resolving the conflict between solder joint protection and substrate size reduction
Solution Approach 2:
A barrier structure is introduced as an intermediary element between the underfill material and the substrate surface. This barrier contains the underfill within die sites, preventing it from flowing into keep out zones and die side component sites, thereby eliminating the need for large keep out zones while maintaining solder joint reliability
2Reliability
If larger keep out zones are created to contain underfill, then underfill containment is improved, but available space for die side components is reduced
Solution Approach 1:
The substrate surface is divided into functional zones: die sites for underfill containment, reduced keep out zones for electrical isolation, and die side component sites for component placement. This segmentation enables effective underfill containment while maximizing the space available for die side components
Solution Approach 2:
The barrier structure serves as an intermediary that contains underfill within die sites, preventing it from encroaching on keep out zones and die side component sites. This allows keep out zones to be reduced in size while maintaining effective underfill containment
3Ease of manufacture
If non-uniform copper thickness is present in bump fields, then manufacturing complexity is reduced, but electrical performance and signal integrity are degraded
Solution Approach 1:
The barrier structure creates localized regions with different copper plating characteristics. By controlling the barrier geometry and plating parameters, uniform copper thickness is achieved in critical bump field areas while allowing flexibility in other regions, thereby improving electrical performance without significantly increasing manufacturing complexity
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 solution effectively conserves package space by containing the underfill material, reducing the size of KOZs and enabling more efficient integration of die side components, while maintaining the mechanical and thermal integrity of the solder joints.
Implementation Method 1
a barrier means on the substrate between the die and die side component sites to contain underfill material
Implementation Method 2
achieved through electroplating and surface routing techniques
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.