Semiconductor Joint Structure for Solder Wetting Control
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Solution Overview
Problem
In semiconductor devices, the multiplex point where different materials meet can experience significant stress due to differences in linear expansion coefficients, leading to potential damage and unsatisfactory stress relaxation when the fillet shape of solder is not adequately controlled, especially if the position of the conductive member or solder deviates.
Innovation Solution
A semiconductor device design featuring a projection portion on the metal thin film surface opposite to the semiconductor element body, where solder is not applied on the outer peripheral side of the projection, preventing wetting and spreading and thus avoiding the formation of stress-prone multiplex points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solder is allowed to wet and spread on the metal film surface, then good electrical connection is achieved, but stress concentration occurs at the multiplex point where solder, protection film, and electrode material meet
Solution Approach 1:
The invention applies local quality by creating a specific region (first area) on the metal film with modified properties (reduced solder wettability) while maintaining normal soldering properties in other areas. This localized modification prevents solder from spreading to the multiplex point, thereby reducing stress concentration at that specific location while preserving good electrical connection in the solder joint areas.
2Manufacturing precision
If areas with reduced solder wettability are provided on the conductive member, then fillet shape on the semiconductor element side can be controlled, but satisfactory stress relaxing effect cannot be obtained when position deviation occurs
Solution Approach 1:
The invention applies preliminary action by pre-forming projection portions on the metal film before soldering. These projection portions serve as physical barriers that proactively prevent solder from reaching the multiplex point, regardless of position deviations during assembly. This advance preparation ensures reliable stress relaxation without requiring precise positioning during the soldering process.
3Shape
If the fillet angle on the semiconductor element side becomes 90 degrees or greater, then complete wetting and spreading of solder occurs, but the multiplex point still remains and stress relaxing effect is insufficient
Solution Approach 1:
The invention applies segmentation by dividing the metal film surface into different functional zones: areas with normal solder wettability for good electrical connection, and a first area with reduced solder wettability to prevent solder spread to the multiplex point. This segmentation allows the fillet to achieve a 90-degree angle or greater for complete wetting while simultaneously preventing solder from reaching the stress-prone multiplex region through the separated low-wettability zone.
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
This design effectively suppresses solder wetting and spreading, preventing stress concentration at the multiplex points and reducing the risk of damage to the semiconductor device, ensuring reliable operation and improved durability.
Implementation Method 1
the solder wettability is reduced on the first area and a third area adjacent to the first area... the fillet shape of solder on the semiconductor element side is controlled
Data Source
AI summary
The semiconductor device includes: a semiconductor element including a body portion formed in a plate shape, a protection film provided at an outer periphery on one surface of the body portion, and a metal thin film provided adjacently to an inner side of the protection film on the one surface of the body portion; a metal member joined to a surface of the metal thin film on a side opposite to the body portion, by solder; and a mold resin sealing the semiconductor element and the metal member, wherein the surface of the metal thin film on the side opposite to the body portion has, on at least a part of an outer periphery thereof, a projection portion projecting from the surface of the metal thin film, and the solder is not provided on an outer peripheral side from a top of the projection portion.