Recessed Solder Ball Packaging for Low-Standoff Semiconductor Assembly
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Solution Overview
Problem
Conventional semiconductor device packaging faces challenges in reducing height while maintaining reliability, as smaller solder joints are susceptible to mechanical vibrations and thermal shock, leading to reliability issues such as crack formation and connection failure.
Innovation Solution
The introduction of substrates with bond pads located on inner conductive layers, allowing solder balls to be recessed into the substrate, reducing the overall package height and mitigating reliability issues associated with smaller solder joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If solder joint size is reduced to decrease package height, then package height is reduced, but solder joint reliability deteriorates due to susceptibility to mechanical vibrations and thermal shock
Solution Approach 1:
The solder joint is nested within a recess in the substrate, allowing the solder ball to be positioned lower relative to the top surface. This nesting approach reduces the overall package height while maintaining adequate solder joint size for reliability, as the recess provides structural support without requiring the solder joint itself to be smaller.
Solution Approach 2:
Instead of reducing solder joint size in the vertical dimension to achieve lower package height, the invention introduces a horizontal dimension solution by creating a recess into which the solder joint is embedded. This dimensional shift allows the package height to be reduced while the solder joint maintains its structural integrity and reliability.
2Length of stationary object
If bond pads are positioned on outer conductive layers, then electrical connection is simplified, but package height increases due to larger solder joint standoff
Solution Approach 1:
The substrate is segmented into multiple conductive layers with bond pads positioned on inner layers rather than outer layers. This segmentation allows the solder joints to be recessed into the substrate structure, reducing the standoff height and overall package height while distributing the electrical connection functions across different layers.
Solution Approach 2:
The bond pads are relocated from outer surface layers to inner conductive layers, utilizing the vertical dimension more efficiently. This repositioning enables the solder joints to be embedded within the substrate thickness, reducing the external package height while maintaining electrical connectivity through the multi-layer structure.
Data Source
AI summary
A semiconductor device assembly includes a semiconductor die and a substrate coupled to the semiconductor die. The substrate includes a primary conductive layer including a first surface of the substrate and a first solder mask layer coupled to the first surface. The substrate also includes a secondary conductive layer including a second surface of the substrate and a second solder mask layer coupled to the second surface. The substrate further includes an inner conductive layer positioned between the primary layer and the secondary layer, where the inner layer includes a bond pad positioned at the end of an opening that extends from the second solder mask layer through the secondary layer to the bond pad of the inner layer. By attaching a solder ball to the bond pad of the inner layer, standoff height is reduced.