Notched Inner Lead Frame for Semiconductor Package Moisture Protection
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Solution Overview
Problem
The delamination of semiconductor die packages due to hydrogen gas emissions during the plating process reduces the structural integrity and rigidity of leads, allowing moisture to corrode bond wires, which is a challenge in maintaining the mechanical and environmental protection of semiconductor dies.
Innovation Solution
The lead frame design includes inner lead lengths with notched regions that extend from the die flag to the mold compound edge, providing increased effective lengths and acting as moisture barriers, while the outer lead lengths are bent to form mounting feet for enhanced structural integrity and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leads are plated with tin during the plating process, then the outer lead ends are protected and prepared for connection, but hydrogen gas emissions cause delamination of the encapsulated regions from the mold compound, reducing structural integrity
Solution Approach 1:
The lead frame is divided into inner leads and outer leads with a distinct boundary at the mold compound interface. The inner leads remain unplated and embedded in the mold compound, while only the outer leads receive tin plating. This segmentation prevents hydrogen gas generated during plating from reaching and delaminating the mold compound interface.
Solution Approach 2:
The harmful plating process is extracted and applied only to the outer leads that extend beyond the mold compound, while the inner leads embedded in the mold compound are excluded from the plating process. This selective application eliminates the source of hydrogen gas emissions at the critical interface.
2Length of moving object
If the inner leads are made longer to improve electrical connection, then the bond wire reach is increased, but the structural rigidity and resistance to moisture corrosion are reduced
Solution Approach 1:
The mold compound acts as an intermediary protective barrier between the inner leads and the external environment. By embedding the inner leads in the mold compound without plating them, the mold compound provides both mechanical support for rigidity and environmental protection against moisture corrosion.
Solution Approach 2:
Different parts of the lead frame receive different treatments: inner leads are left unplated and embedded in the mold compound for protection, while outer leads are plated for electrical connection. This local differentiation allows each part to have the properties needed for its specific function.
Data Source
AI summary
A semiconductor device is assembled from a lead frame. The device has a semiconductor die mounted on a flag of the lead frame. A mold compound forms a housing that covers the die. Lead fingers surround the die. Each lead finger has an inner lead length that is covered by the housing and an outer lead length that protrudes from the housing. The inner lead length extends from an edge of the housing towards the die. The inner lead length has an intermediate region that has been bent to form a notch. Bond wires electrically connect electrodes of the die to respective inner lead lengths.