Through-Substrate Via Solder Ball Void
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Solution Overview
Problem
In three-dimensional integration of semiconductor devices, existing methods for connecting substrates through through-substrate vias often require filling the via with conductive material, which can be inefficient in terms of substrate surface area usage and may lead to issues with capillary forces drawing solder into the via, limiting the arrangement of interconnects.
Innovation Solution
A method involving a semiconductor substrate with an annular cavity extending from the front to the rear side, where separate metallizations are applied on the sidewalls of the cavity, and a solder ball is placed above the opening, allowing reflow to form a void-covered through-substrate via without filling, using the substrate pillar for mechanical support and reducing capillary forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the through-substrate via is filled with conductive material, then electrical connection is established, but substrate surface area is wasted and capillary forces draw solder into the via
Solution Approach 1:
Instead of filling the via with conductive material to establish electrical connection, the invention inverts the approach by leaving the via unfilled and using a solder ball that caps the via opening. The solder ball itself provides the electrical connection path, eliminating the need for via filling and preserving substrate surface area.
Solution Approach 2:
The invention extracts the conductive material from the via interior and places it in the form of a solder ball on the via opening. This extraction eliminates capillary forces that would otherwise draw solder into the via, while the solder ball remains positioned to provide electrical connection.
2Reliability
If the via is filled with conductive material, then electrical connection is established, but capillary forces draw solder into the via causing unwanted filling
Solution Approach 1:
The invention converts the potential harm of capillary forces into a benefit by using an unfilled via configuration. Without conductive material in the via, capillary forces cannot draw solder into the via, preventing unwanted filling. The solder ball caps the via opening, allowing controlled electrical connection without the harmful effect of capillary action.
3Ease of manufacture
If traditional via filling is used, then interconnect arrangement is simplified, but substrate area usage is inefficient
Solution Approach 1:
The invention transitions from a two-dimensional via filling approach to a three-dimensional solder ball configuration that caps the via. This dimensional change allows the solder ball to provide electrical connection while occupying minimal substrate area, improving area utilization efficiency compared to traditional via filling methods.
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 approach allows for efficient electrical connection between substrates using a solder ball that caps the via, enabling variable interconnect arrangements while minimizing substrate area usage and preventing filling of the via, thus improving electrical properties and mechanical support.
Implementation Method 1
reducing capillary forces
Data Source
AI summary
A semiconductor substrate is provided with an annular cavity extending from a front side of the substrate to an opposite rear side. A metallization is applied in the annular cavity, thereby forming a through-substrate via and leaving an opening of the annular cavity at the front side. A solder ball is placed above the opening and a reflow of the solder ball is effected, thereby forming a void of the through-substrate via, the void being covered by the solder ball.