QFN Housing Leadframe Layout to Prevent Delamination
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Solution Overview
Problem
Quad-flat no-leads (QFN) housings often suffer from gaps and delamination between metal leadframes and housing plastics during production, particularly in processes like waterjet deflashing and bending, leading to mechanical instability and increased risk of damage.
Innovation Solution
A housing design featuring offset solder control structures on leadframe parts, with a semi-etched circumferential tie bar frame and staggered solder control points, providing mechanical flexibility and reinforcement against bending forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional QFN housings are used with aligned solder control structures, then manufacturing is simpler, but gaps and delamination occur between leadframes and housing plastics during production
Solution Approach 1:
The patent applies asymmetry by offsetting the solder control structures on opposite leadframe parts from each other. Instead of aligning the solder control structures symmetrically, the first solder control structure on the first leadframe part is positioned at a different location than the second solder control structure on the second leadframe part. This asymmetric arrangement prevents gaps and delamination between the leadframes and housing plastics during production processes like waterjet deflashing and bending, while still maintaining manufacturability through standard offset manufacturing techniques.
2Strength
If rigid housing structure is used, then mechanical strength is improved, but vulnerability to bending forces and vibrations increases
Solution Approach 1:
The patent applies dynamics by introducing flexibility into the housing structure through the offset solder control structures. The offset arrangement allows the leadframe parts to move relative to each other in response to bending forces and vibrations, absorbing mechanical stress without causing damage. This dynamic capability enables the housing to withstand production processes like waterjet deflashing and bending while maintaining overall structural integrity, preventing both gaps/delamination and damage from mechanical forces.
Data Source
AI summary
In an embodiment a housing includes a first leadframe part and a second leadframe part and a housing body mechanically connecting the first and second leadframe parts to one another, wherein each first and second leadframe part has a mounting area on an inner side and each has an outer side opposite the inner side, wherein the first leadframe part has at least one solder control point and the second leadframe part has at least two solder control points, wherein each solder control point is formed as a recess at an associated outer side and is accessible from an outer side wall of the housing, and wherein the solder control points of the second leadframe part and the at least one solder control point of the first leadframe part are located on mutually opposite outer side walls of the housing body and are arranged completely offset relative to one another so that the solder control points are free of an overlap in a direction parallel to a main axis.