Semiconductor Lead Frame Arch Bent Structure Stress Relief
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Solution Overview
Problem
Conventional semiconductor devices experience reliability issues with electrical connections due to stress generated at the joint between the lead frame and substrate under thermal stress.
Innovation Solution
A semiconductor device design featuring a lead frame with a protruding arch portion and bent portion, where notches on the bent portion allow for conductive bonding material to be embedded, facilitating stress relief by directing thermal stress to the sealing portion and ensuring secure fixation through solder material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional lead frame structure is used, then the device structure is simple, but stress concentrates at the joint between the lead frame and substrate, reducing electrical connection reliability
Solution Approach 1:
The lead frame structure is segmented into distinct functional portions: a joint portion for bonding to the substrate, an arch portion extending upward, and a bent portion protruding downward. This segmentation allows stress to be distributed across different sections rather than concentrating at the joint, with the bent portion specifically designed to relieve stress through its geometric configuration
Solution Approach 2:
The lead frame incorporates curved geometric features including an arch portion that extends upward in an arched shape and a bent portion that protrudes downward. These curved structures provide stress relief by distributing mechanical stress through the curvature rather than creating sharp stress concentration points at rigid joints
2Reliability
If the lead frame is rigidly bonded to the substrate, then electrical connection is secure, but thermal stress causes stress concentration at the joint portion
Solution Approach 1:
Different portions of the lead frame are designed with different geometric properties to serve specific functions: the joint portion maintains bonding capability, the arch portion provides structural support, and the bent portion is specifically designed with a protruding geometry that creates a stress relief effect. This local differentiation allows the structure to handle thermal stress while maintaining electrical connection
Solution Approach 2:
The bent portion acts as an intermediary element between the rigid substrate and the flexible lead frame extensions. Its protruding geometry creates a transition zone that mediates the stress transfer, allowing thermal expansion and contraction without concentrating stress at the primary bonding joint
3Reliability
If conductive bonding material is applied at the joint, then electrical connection is established, but stress from thermal cycling degrades the joint reliability
Solution Approach 1:
The bent portion is designed in advance to provide stress cushioning before thermal stress can degrade the joint. The protruding geometry of the bent portion creates a predetermined stress relief mechanism that absorbs and distributes thermal stress away from the bonding joint, protecting the joint durability under repeated thermal cycling
Data Source
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AI summary
A semiconductor device includes: a substrate that has a plurality of conductive layers on a upper surface thereof; a semiconductor element that disposed on the upper surface of the substrate, the semiconductor element having a first terminal on a lower surface side of the semiconductor element electrically connected to a first conductive layer provided on the upper surface of the substrate; a sealing portion that seals the substrate and the semiconductor element; a first lead frame that has one end in contact with a upper surface of the first conductive layer at an end extending in the side direction of the upper surface of the substrate in the sealing portion, and has the other end exposed from the sealing portion; a first conductive bonding material that bonds between the upper surface of the first conductive layer and the lower surface side of the one end portion of the first lead frame at the end portion of the substrate, and has electrical conductivity. The one end portion of the first lead frame has : a first arch portion that provided so as to protrude upward along a reference direction, and a first bent portion that is connected to the first arch portion, and is located closer to a distal end side of the one end portion of the first lead frame than the first arch portion, and the first bent portion bent along the reference direction so as to protrude downward.