Differential Height Lead Structures for QFN Package Integrity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The low market penetration of pad-up quad flat non-leaded (QFN) packages is due to their impracticality for surface mount technology, high manufacturing costs, and issues with wire bonding and lead deflection, which result in defects and reduced package integrity.
Innovation Solution
A non-leaded integrated circuit package system with differential height lead structures, where inner leads are at a paddle height, and an elevated paddle provides mold locks at bending points, allowing for improved manufacturing techniques and cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If punch singulation is used to reduce manufacturing costs, then cost is reduced, but lead deflection increases causing defects and degraded package integrity
Solution Approach 1:
The lead frame is segmented into multiple regions with different lead heights (first height for outer leads, second height for inner leads). This segmentation allows the outer leads to be positioned at a lower height that is less susceptible to deflection during punch singulation, while inner leads can maintain higher positions for proper electrical connection. The segmentation resolves the contradiction by allowing cost-effective punch singulation while maintaining package integrity through strategic height differentiation.
Solution Approach 2:
Different regions of the lead frame are given different local qualities in terms of lead height. Outer leads are positioned at a first height optimized for mechanical stability during singulation, while inner leads are positioned at a second height optimized for electrical connection. This local quality differentiation allows each region to perform its specific function optimally, resolving the contradiction between manufacturing ease and package reliability.
2Adaptability or versatility
If differential height lead structures are used to improve package design, then package functionality is improved, but wire bonding becomes difficult to control due to thermosonic energy transmission
Solution Approach 1:
The lead frame is segmented into outer leads at a first height and inner leads at a second height. This segmentation allows wire bonding to be performed on the inner leads at the optimized second height where thermosonic energy transmission is better controlled, while outer leads at the first height provide mechanical support. The segmentation enables differential height design flexibility while maintaining wire bonding precision at the appropriate location.
Solution Approach 2:
The outer leads at the first height serve as intermediary structures that provide mechanical support and stability during the wire bonding process. By positioning outer leads at a lower first height, they act as stable intermediaries that reduce unwanted vibrations and thermosonic energy transmission to the inner leads where wire bonding occurs, thereby improving wire bonding control while maintaining design flexibility.
3Adaptability or versatility
If hanging leads are used in QFN architecture, then interconnectivity is achieved, but leads bounce during wire bonding reducing manufacturing yield
Solution Approach 1:
The lead frame is segmented into outer leads at a first height and inner leads at a second height. This segmentation allows outer leads to serve as stable anchor points for interconnectivity while inner leads at the elevated second height are optimized for wire bonding. The height differentiation prevents bouncing during wire bonding by providing a stable reference level, thereby maintaining interconnectivity while improving manufacturing yield.
4Manufacturing precision
If saw singulation method is used for QFN manufacturing, then precise cutting is achieved, but manufacturing cost increases due to diamond saw blade costs
Solution Approach 1:
The lead frame is segmented with outer leads at a first height and inner leads at a second height, with the segmentation lines positioned to optimize punch singulation. This segmentation allows the use of cost-effective punch singulation methods while maintaining precise separation of individual packages. The strategic positioning of segmentation lines at different heights enables clean separation without requiring expensive diamond saw blades, thereby reducing manufacturing cost while maintaining adequate cutting precision.
Data Source
AI summary
A non-leaded integrated circuits package system is provided including etching differential height lead structures having inner leads at a paddle height, providing mold locks at the bending points of the differential height lead structures, etching an elevated paddle at a same height as the inner leads, mounting a first integrated circuit on the elevated paddle, and electrically connecting first electrical interconnects between the first integrated circuit and the inner leads.