Direct Leadframe Attachment With Buffer Legs for Die Crack Prevention
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Solution Overview
Problem
Current semiconductor device packages face mechanical stress issues due to tolerance variations and dimension tolerances, leading to quality and reliability problems such as die cracking and substrate cracking, and struggle with controlling conductive adhesive thickness to prevent electrical shorts and thermal-mechanical stresses, while being costly due to expensive materials like molybdenum copper for conductive spacers.
Innovation Solution
The solution involves a semiconductor device package with a leadframe having indentations directly coupled to the semiconductor die via a conductive adhesive, where buffer legs on the leadframe act as mechanical stops to control the adhesive thickness and prevent shorts, eliminating the need for conductive spacers and reducing material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive adhesive layer thickness is increased to reduce thermal-mechanical stresses, then die cracking is reduced, but solder overflow occurs causing electrical shorts and die tilting
Solution Approach 1:
The leadframe is segmented into multiple functional portions: buffer legs that contact the substrate to control adhesive thickness, a body portion that holds the semiconductor die, and indentations that receive the die. This segmentation allows different portions to perform specialized functions, with buffer legs specifically controlling solder thickness to prevent overflow while maintaining sufficient thickness to reduce thermal-mechanical stresses.
Solution Approach 2:
The buffer legs act as an intermediary element between the substrate and the leadframe body. They mechanically interact with the substrate to control the thickness of the conductive adhesive layer, serving as a mediator that translates substrate contact into precise adhesive thickness control, thereby preventing solder overflow while maintaining reliability.
2Reliability
If conductive spacers made of expensive materials like molybdenum copper are used, then die cracking during reliability stress testing is reduced, but package cost increases
Solution Approach 1:
The invention extracts and eliminates the conductive spacer component from the package structure. By using direct leadframe-to-die attachment with buffer legs for mechanical support and thickness control, the expensive molybdenum copper spacers are completely removed, reducing material cost while maintaining die cracking resistance through the buffer leg mechanism.
Solution Approach 2:
The leadframe buffer legs replace expensive conductive spacers with a more cost-effective solution. The buffer legs are integrated into the leadframe structure and perform the mechanical support function that previously required expensive separate spacer components, achieving the same reliability protection at lower material cost.
3Ease of manufacture
If tolerance variations and dimension tolerances of assembly process jigs are present, then manufacturing flexibility is maintained, but mechanical stress on package elements increases causing quality issues
Solution Approach 1:
The buffer legs provide a dynamic mechanical interface between the leadframe and substrate. Rather than rigid fixed positioning, the buffer legs can flex and accommodate tolerance variations in the assembly process jigs and package elements, absorbing dimensional variations while maintaining reliable electrical and mechanical connections, thus reducing mechanical stress on sensitive components.
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 reduces mechanical stresses, prevents die and substrate cracking, and controls adhesive thickness to prevent electrical shorts, enhancing the reliability and cost-effectiveness of semiconductor device packages by eliminating the need for expensive conductive spacers.
Implementation Method 1
coupling a semiconductor die with a substrate, and directly coupling an indentation formed in a body of a leadframe with the semiconductor die via a solder material
Data Source
AI summary
In general aspect, a semiconductor device package can include a substrate and a semiconductor die disposed on and coupled with the substrate. The semiconductor device package can further include a leadframe having an indentation defined therein, at least a portion of the indentation being disposed on and coupled with the semiconductor die via a conductive adhesive.