Lead Frame Grooves for Dambar Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Injection molding processes for semiconductor packages often result in the formation of conductive fritters due to unwanted mold compound on leads, leading to reliability issues and electrical shorts.
Innovation Solution
A lead frame design featuring grooves on the leads to accommodate mold compound, preventing its formation on the sides and reducing the risk of fritters during the molding and plating processes, with the grooves extending longitudinally between the die pad and inner dam bars, and a subsequent plating process that covers the leads without reaching the lateral sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If injection molding process is used to encapsulate semiconductor die, then the semiconductor die is protected from environmental conditions, but mold compound may form on leads creating conductive fritters that cause electrical shorts
Solution Approach 1:
The lead surface is segmented into different zones by introducing grooves that divide the lateral surface into upper and lower portions. This segmentation allows the mold compound to be contained in specific grooved regions rather than forming unwanted deposits on the entire lead surface, preventing conductive fritter formation while maintaining protective encapsulation.
Solution Approach 2:
The grooves act as intermediary structures between the mold compound and the lead surface. By providing designated grooved regions, the mold compound is redirected to accumulate in these intermediate zones rather than directly on the lead's lateral surface, eliminating the harmful effect of conductive fritter formation.
2Reliability
If plating process is applied to covers leads, then electrical conductivity is improved, but plating material may reach lateral sides and cause fritter formation during dam bar punching
Solution Approach 1:
The lead surface is segmented into different zones by introducing grooves that divide the lateral surface into upper and lower portions. This segmentation allows the mold compound to be contained in specific grooved regions rather than forming unwanted deposits on the entire lead surface, preventing conductive fritter formation while maintaining protective encapsulation.
Solution Approach 2:
The grooves act as intermediary structures between the mold compound and the lead surface. By providing designated grooved regions, the mold compound is redirected to accumulate in these intermediate zones rather than directly on the lead's lateral surface, eliminating the harmful effect of conductive fritter formation.
3Reliability
If grooves are added to lead surface to channel mold compound, then fritter formation is reduced, but lead frame structure becomes more complex
Solution Approach 1:
Instead of modifying the entire lead frame structure, the grooves are introduced only in specific local regions of the leads where mold compound accumulation occurs. This localized modification maintains the overall simplicity of the lead frame while effectively preventing fritter formation in critical areas.
Solution Approach 2:
The groove geometry parameters (depth, width, spacing) can be optimized to achieve effective mold compound channeling with minimal structural complexity. By carefully controlling these parameters, the solution maintains simplicity while maximizing reliability improvement.
Data Source
AI summary
A lead frame includes a die pad, a first lead extending away from the die pad, a peripheral structure mechanically connected to the first lead and the die pad, and a first groove in an outer surface of the first lead. The first groove extends longitudinally along the first lead away from the die pad.