Semiconductor Leadframe Layout Using Laser Ablation for Creepage Distance
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Solution Overview
Problem
Existing methods for increasing creepage distance between solder joints in semiconductor devices, such as customizing leadframes and applying insulating materials, are costly and prone to handling issues like scratches.
Innovation Solution
A method involving a standard pre-plated leadframe with selective laser ablation to remove masking layers and subsequent back etching, allowing for customized lead layouts that increase creepage distance without altering the wire bonding pattern or assembly flow significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If customizing leadframe and substrate layout is applied to increase creepage distance, then creepage distance is improved, but manufacturing cost and lead time increase
Solution Approach 1:
The patent applies preliminary action by pre-plating the entire leadframe with a masking layer (e.g., NiPdAu) before assembly. This pre-applied masking layer enables subsequent selective removal through laser ablation, allowing customization of lead layouts without requiring custom leadframe manufacturing. The preliminary plating action facilitates later selective lead removal while maintaining cost efficiency using standard leadframes.
Solution Approach 2:
The patent utilizes parameter changes by employing laser ablation to selectively remove the masking layer from specific leads. This changes the physical state and presence of the masking layer parameter, exposing the underlying metal for etching. The parameter change approach allows dynamic customization of lead configurations post-assembly, resolving the contradiction between maintaining standard leadframes and achieving customized creepage distances.
2Reliability
If insulating material is applied on electrically conductive leads, then creepage distance is improved, but the material is sensitive to scratches during handling
Solution Approach 1:
The patent applies the extraction principle by removing certain electrically conductive leads from the assembly entirely through selective laser ablation of their masking layers followed by etching. Instead of protecting vulnerable insulating materials on all leads, the solution extracts the problematic leads completely, eliminating the need for insulating material application and associated scratch risks. This achieves creepage distance enhancement through physical removal rather than protective coating.
3Reliability
If removing contact leads from full lead layout is applied, then creepage distance is improved, but additional costs and lead-time issues occur
Solution Approach 1:
The patent uses preliminary action by pre-plating all leads with a masking layer in advance. This preliminary step enables rapid selective lead removal later through laser ablation and etching, avoiding the need for custom leadframe manufacturing. The pre-applied masking layer serves as a ready-to-remove template that accelerates the lead removal process, reducing lead time compared to traditional customization approaches.
Solution Approach 2:
The patent replaces mechanical customization processes with laser-based ablation technology. Instead of mechanically removing leads or using complex custom manufacturing, the solution uses laser energy to selectively remove masking layers and enable etching. This substitution of mechanical systems with optical/thermal processes reduces manufacturing complexity and lead time while achieving the same creepage distance enhancement.
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 increases creepage distance, reducing the risk of short circuits while maintaining cost efficiency and minimizing the impact on assembly processes, with visible recesses indicating removed leads for easy inspection.
Implementation Method 1
The masking layer is selectively removed, for example, via laser ablation, from one or more of the electrically conductive leads
Implementation Method 2
Etching is applied to the second surface of the substrate so that the electrically conductive formations such as leads left uncovered by the masking layer are removed
Data Source
AI summary
A semiconductor integrated circuit chip is arranged on a first surface of a substrate that includes electrically conductive lead formations in an array, wherein the electrically conductive lead formations are covered by a masking layer at a second surface opposite the first surface. The semiconductor integrated circuit chip is electrically coupled to electrically conductive lead formations and an insulating encapsulation is molded on the semiconductor integrated circuit chip. The masking layer is then selectively removed, for example, via laser ablation, from one or more of the electrically conductive lead formations. The electrically conductive lead formations that are left uncovered by the masking layer are then removed by an etching process applied to the second surface of the substrate. The selective removal of the unmasked electrically conductive lead formations serves to increase a creepage distance between those conductive lead formations that are left in place.