Semiconductor Lead Thermal Stress Equalizing Structure
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Solution Overview
Problem
Conventional semiconductor devices face challenges in achieving uniform thermal shrinking stress distribution during bonding, leading to potential chip inclination and non-uniform solder thickness, which complicates the production of reliable semiconductor devices.
Innovation Solution
Incorporating a thermal shrinking stress equalizing structure on the lead's outer periphery, featuring bulging portions or cutouts that balance heat transfer and stress distribution, ensuring equal contact area and heat resistance between the solder and lead, thereby maintaining uniform solder thickness and minimizing chip inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the chip and lead are bonded by heating the substrate, chip and lead, then the chip and lead are electrically connected via solder, but thermal shrinking stress applied to the solder differs depending on portions of the solder, causing chip inclination and non-uniform solder thickness
Solution Approach 1:
The lead structure is designed with asymmetric features: a first electrode connecting portion with larger area than the second electrode connecting portion, and a thermal stress equalizing structure (bulging portion or cutout) positioned asymmetrically on the outer periphery. This asymmetry compensates for the uneven thermal stress distribution that occurs during heating, allowing the solder to solidify uniformly without causing chip inclination while maintaining reliable electrical connection
2Reliability
If the solder spreads by wetting and creeping along the lead surface, then electrical connection is achieved, but the surface area of solder in contact with lead differs between sides, causing unequal thermal shrinking stress
Solution Approach 1:
The lead is designed with non-uniform local properties: the first electrode connecting portion has a larger area than the second electrode connecting portion, and a thermal stress equalizing structure (bulging portion or cutout) is positioned at a specific location on the outer periphery. These local structural variations compensate for the uneven solder spreading and creeping that occurs during bonding, ensuring uniform thermal stress distribution and preventing chip inclination while maintaining reliable electrical connection
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 solution ensures a highly reliable semiconductor device by maintaining uniform solder thickness and consistent heat transfer, reducing the risk of chip inclination and enhancing the overall reliability and performance of the device.
Implementation Method 1
in bonding the chip 920 and the lead 930 to each other by heating the substrate 910, the chip 920 and the lead 930
Implementation Method 2
by heating the substrate 910, the chip 920 and the lead 930
Implementation Method 3
the solder 950 spreads by wetting along a surface of the lead 930 on a chip 920 side
Implementation Method 4
a thermal shrinking stress equalizing structure which is configured to make a thermal shrinking stress applied to the conductive bonding material disposed between the first electrode connecting portion and the surface electrode equal
Data Source
AI summary
A semiconductor device including a substrate; a chip on which a surface electrode is formed; and a lead. The lead includes a first electrode connecting portion disposed on the surface electrode and electrically connected to the surface electrode of the chip via a conductive bonding material; a second electrode connecting portion electrically connected to an electrode portion of a wiring pattern. A lead connected to the first electrode connecting portion and the second electrode connecting portion. The lead further has a thermal shrinking stress equalizing structure on a portion of an outer periphery of the first electrode connecting portion. The lead is configured to make a thermal shrinking stress applied to a conductive bonding material between the first electrode connecting portion and the surface electrode equal.