QFN Package Corner Lead Half-Etch Locking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing quad flat no leads (QFN) and dual flat no leads (DFN) packages face challenges in maintaining lead integrity during singulation due to insufficient mechanical locking between leads and mold compound, leading to potential lead drop-off during sawing processes, which restricts package size reduction and robustness.
Innovation Solution
Incorporating a lead frame design with corner leads featuring a half etch on both a first portion that extends internally into the package for mechanical mold compound locking and a second portion located on the edge, ensuring robust attachment and preventing lead drop-off, even at increased saw offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If leads are placed closer to package edges to reduce package size, then package size is reduced, but lead integrity deteriorates due to insufficient mechanical locking
Solution Approach 1:
The lead structure is modified with different features at different locations: a first portion with etching pattern extends into the package body for mechanical locking with mold compound, while a second portion remains on the edge for electrical connection. This local differentiation allows the lead to provide both secure anchoring and edge proximity for compact packaging.
Solution Approach 2:
The lead is pre-configured with a specific geometry during manufacturing, including the first portion extending internally and the second portion on the edge. This preliminary structural preparation ensures that when mold compound is applied, mechanical locking occurs automatically without requiring additional assembly steps, maintaining lead integrity while enabling compact design.
2Productivity
If saw offset is increased to improve manufacturing efficiency, then productivity is improved, but lead drop-off increases due to insufficient mechanical locking
Solution Approach 1:
The lead geometry is changed by extending the first portion internally into the package body and applying etching patterns. This parameter modification increases the mechanical interlocking strength between lead and mold compound, allowing the sawing process to use larger offsets for higher productivity without causing lead drop-off.
3Reliability
If half etch is applied on both first and second portions of the lead, then mechanical locking is enhanced, but manufacturing complexity increases
Solution Approach 1:
The lead is divided into two functional portions: the first portion extending internally into the package body for mechanical locking, and the second portion remaining on the edge for electrical connection. This segmentation allows each portion to be optimized independently - the first portion receives etching for locking while the second portion maintains simple edge geometry, balancing reliability with manufacturability.
Data Source
AI summary
Implementations of semiconductor packages may include: a lead frame having at least one corner lead, the at least one corner lead positioned where two edges of the package meet, and the at least one lead having a half etch on a first portion of the lead and a half etch on a second portion of the lead. The first portion may extend internally into the package to create a mechanical mold compound lock between a mold compound of the package and the lead. The second portion may be located on at least one of the two edges of the package.