Semiconductor Substrate Tie-Bar Ablation for Clean Singulation
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Solution Overview
Problem
In semiconductor device manufacturing, the accumulation of metallic material on connecting bars during the plating step leads to filament formation during singulation, causing short circuits and device failure due to the metal flakes bridging neighboring leads.
Innovation Solution
The metallic material accumulated on the back surface of the connecting bars is removed via laser ablation before the singulation step, specifically at tie bars where filament formation is observed, to prevent metal flakes from forming electrical contacts between neighboring leads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If large connecting bars are used during plating to facilitate processing, then plating is improved, but metal accumulation on connecting bars causes filament formation during singulation leading to short circuits
Solution Approach 1:
The patent applies preliminary action by performing a selective removal step (e.g., laser ablation or selective plating reversal) on the connecting bars before the singulation process. This removes or reduces the excess metal accumulation on the connecting bars that would otherwise cause filament formation during cutting, thereby preventing short circuits while maintaining the benefits of large connecting bars during plating
2Productivity
If connecting bars are removed during singulation, then individual devices are separated, but metal flakes from connecting bars bridge neighboring leads causing short circuits
Solution Approach 1:
The patent performs preliminary removal of metal accumulation from connecting bars before singulation through selective laser ablation or controlled dissolution. This preliminary action ensures that when connecting bars are removed during singulation, minimal metal flakes are generated, preventing bridging of neighboring leads and maintaining electrical isolation
Solution Approach 2:
The patent replaces the purely mechanical singulation process with a hybrid approach that includes selective laser ablation or chemical treatment of connecting bars before mechanical cutting. This substitution reduces metal flake generation by pre-removing excess metal through non-mechanical means, thereby preventing short circuits during the mechanical separation process
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 effectively reduces the risk of filament formation and subsequent short circuits, enhancing the reliability of semiconductor devices by ensuring clean separation of connecting bars during singulation without compromising solderability.
Implementation Method 1
metallic material may be removed from the back/bottom surface of the connecting bars via laser ablation
Data Source
AI summary
Semiconductor chips are arranged on a first surface of a common electrically conductive substrate having an opposite second surface. The substrate includes adjacent substrate portions having mutually facing sides with sacrificial connecting bars extending between adjacent mutually facing sides. A solderable metallic layer is present on the second surface extending over the sacrificial connecting bars. The solderable metallic layer is selectively removed (by laser ablation or etching, for example) from at least part of the length the sacrificial connecting bars. The common electrically conductive substrate is then cut along the length of the elongate sacrificial connecting bars to provide singulated individual semiconductor devices. Undesired formation of electrically conductive filaments or flakes bridging parts of the substrate intended to be mutually isolated is countered.