Z-Shaped IC Lead Design for Thermal Cycling Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Surface mounted integrated circuit packages with conventional 'gull wing' leads suffer from poor board level reliability due to non-compliance with bending, leading to adverse effects on drop test and thermal cycling performance, particularly in automotive designs where higher circuit board reliability is required.
Innovation Solution
The integration of leads with a Z-shape design, featuring upper and lower bends, which absorb deformation mismatch between the package and circuit board during thermal cycling, enhancing solder joint reliability by distributing stress more effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional 'gull wing' leads are used in surface mounted integrated circuit packages, then the package structure is simple and easy to manufacture, but the board level reliability is poor due to non-compliance with bending during thermal cycling and drop tests
Solution Approach 1:
The patent applies curvature by transforming the conventional straight lead structure into a Z-shaped configuration with multiple bends. This curvature allows the lead to absorb thermal expansion mismatches and mechanical stresses during thermal cycling and drop tests, significantly improving board level reliability while maintaining manufacturing feasibility through standard lead formation processes
2Reliability
If leads are made rigid to maintain structural stability, then the package maintains its shape, but the solder joint reliability deteriorates due to inability to absorb deformation mismatch during thermal cycling
Solution Approach 1:
The patent changes the geometric parameters of the lead by introducing Z-shaped bends with specific angles and lengths. This parameter modification transforms the lead from a rigid straight structure to a flexible configuration that can absorb deformation mismatches during thermal cycling, thereby improving solder joint reliability without compromising overall structural integrity
3Reliability
If the lead structure is simplified for ease of manufacture, then production cost is reduced, but the thermal cycling performance and drop test results are adversely affected
Solution Approach 1:
The patent segments the lead into multiple straight sections connected by bends, forming a Z-shaped configuration. This segmentation allows each section to be optimized for specific functions (attachment, flexibility, solder joint) while maintaining compatibility with standard automated lead formation processes, thus achieving improved thermal cycling performance without significantly increasing manufacturing complexity
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
The Z-shape lead design reduces maximum solder stress by over 30% compared to conventional designs, improving board level reliability and absorbing thermal and stress-related mismatches, thus enhancing the reliability of solder joints.
Implementation Method 1
The Z-shape provides a more flexible lead that connects the device to the board could absorb the deformation mismatch between the device and circuit board during thermal cycling
Data Source
AI summary
An integrated circuit (IC) device includes an IC and encapsulating material surrounding the IC. Leads are coupled to the IC and extend outwardly from sides of the encapsulating material, with each lead having three contiguous exposed segments with upper and lower bends defining a Z-shape. In another example, the leads include an upper horizontal segment, lower horizontal segment, and intermediate curved segment extending upwardly from the upper horizontal segment and downwardly to the lower horizontal segment.