Variable-Thickness Lead Recess for Thermal-Stress Solder Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor devices with small terminal parts are prone to solder cracking or separation due to thermal stress, leading to bonding failures when subjected to rapid temperature changes.
Innovation Solution
A semiconductor device design featuring a recess on the first lead exposed from the sealing resin, which increases the bond area with solder, reducing the likelihood of crack formation and separation under thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the terminal part size is reduced to make smaller semiconductor devices, then the device size is reduced, but the bonding surface area becomes smaller making solder more prone to cracking and separation under thermal stress
Solution Approach 1:
The invention transitions from a two-dimensional bonding surface to a three-dimensional bonding structure by forming a recess in the terminal part. This recess allows solder to fill the cavity, creating additional bonding interfaces on multiple surfaces (bottom, side walls) rather than just a flat plane, thereby increasing the effective bonding area without increasing the footprint of the terminal part.
Solution Approach 2:
The recess structure creates a nested configuration where the solder is contained within a cavity formed in the terminal part. This nested arrangement allows the solder to be surrounded by the terminal part structure, providing mechanical support from multiple directions and enhancing the bonding interface through the cavity walls.
2Reliability
If the bonding surface area is increased to prevent solder cracking, then solder bonding reliability is improved, but the terminal part size increases leading to larger semiconductor devices
Solution Approach 1:
The recess structure utilizes the vertical dimension (depth) to increase bonding area without expanding the horizontal footprint. By creating a cavity that extends downward from the terminal part surface, the invention achieves additional bonding surface area on the recess bottom and side walls while maintaining a compact overall device size.
3Strength
If the solder bonding area is increased to reduce crack formation, then resistance to thermal stress is improved, but the device complexity increases
Solution Approach 1:
The recess structure applies local quality enhancement by concentrating the increased bonding area in a specific localized region (the recess cavity) rather than uniformly expanding the entire terminal part. This localized modification provides enhanced thermal stress resistance at the critical bonding interface while keeping the rest of the device structure simple and unchanged.
Data Source
AI summary
A semiconductor device includes a semiconductor element, a first lead electrically connected to the semiconductor element, a sealing resin that covers the semiconductor element and a part of the first lead, and a recess formed in a surface flush with a back surface of the sealing resin. The sealing resin also has a front surface opposite to the back surface in a thickness direction, and a side surface connecting the front surface and the back surface to each other. The recess is formed, in part, by a part of the first lead that is exposed from the back surface of the sealing resin. The recess has an outer edge that forms a closed shape, as viewed in the thickness direction, within a region that includes the back surface of the sealing resin and the first lead.