Bonding Wire Curvature for Thermal-Stress-Resistant Lead Frames
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Solution Overview
Problem
Existing semiconductor devices face reliability degradation due to stress from thermal cycles caused by the expansion and contraction of sealing resin, which is exacerbated by the amount of resin between the wire and the lead frame.
Innovation Solution
The semiconductor device features a wire structure with multiple bent portions that reduce the amount of resin contact, including a first bent portion guiding the wire over the mounting substrate surface and a second bent portion guiding it over the semiconductor chip surface, minimizing resin contact and avoiding direct contact with the chip edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wire is positioned to allow sealing resin between the wire and lead frame, then the device can be properly sealed, but stress from thermal cycle causes reliability degradation
Solution Approach 1:
The wire is formed with a curved path including a first bent portion and a second bent portion, creating an M-shaped configuration. This curvature allows the wire to arc over the sealing resin rather than running straight through it, minimizing the amount of resin the wire holds and reducing thermal stress while maintaining proper device sealing.
2Device complexity
If a simple straight wire connection is used, then the structure is simple, but the wire cannot resist pressurization and thermal stress effectively
Solution Approach 1:
The wire incorporates two bent portions creating an M-shaped curve. The first bent portion arcs over the mounting substrate surface, and the second bent portion arcs over the semiconductor chip surface. This curved configuration provides mechanical strength to resist pressurization while reducing thermal stress from the sealing resin, thereby improving durability without excessive complexity.
3Volume of moving object
If the wire is positioned close to the chip edge for compact design, then space is saved, but the wire may contact the chip edge causing damage
Solution Approach 1:
The second bent portion of the wire arcs upward over the semiconductor chip surface, creating a clearance between the wire and the chip edge. This curved path allows the wire to pass close to the chip for compact design while the upward arc prevents direct contact with the chip edge, eliminating the risk of mechanical damage.
Data Source
AI summary
A semiconductor device includes a mounting substrate having a first surface, a semiconductor chip mounted on the first surface and having a second surface facing a side opposite to the first surface, and a wire extending from a first joint point on the first surface toward a second joint point on the second surface and electrically connecting the mounting substrate and the semiconductor chip to each other by connecting the first joint point and the second joint point to each other. The wire includes a first part, a first bent portion, a second part, a second bent portion, and a third part arranged in order from the first joint point toward the second joint point. The first part is positioned on the first surface side with respect to the second surface when viewed in a first direction along the first surface and the second surface.