Semiconductor Lead Frame with Inclined Portion for Solder Control
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Solution Overview
Problem
Conventional semiconductor devices face challenges in processing thick lead frames connected to small-area terminals, leading to difficulties in preventing conductive bonding materials like solder from protruding from the terminal surface, which affects electrical characteristics and increases costs.
Innovation Solution
A semiconductor device design featuring a lead frame with a reference, intermediate, and inclined portion, where the inclined portion is thinner than the reference, allowing for easier processing and reduced solder protrusion by thinning the periphery of the junction with the terminal and making line contact, facilitating microfabrication and reducing solder area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead frame is made thick to increase allowable current value, then the current carrying capacity is improved, but the processing difficulty increases and solder protrusion cannot be suppressed
Solution Approach 1:
The lead frame is designed with different thicknesses in different regions: the main body maintains sufficient thickness for current carrying, while the joint portion has reduced thickness to enable precise processing and solder control. This local differentiation resolves the contradiction between overall thickness requirements and local processing requirements.
Solution Approach 2:
The lead frame joint portion is divided into multiple segments including a first inclined portion, second inclined portion, and intermediate portion with varying thicknesses. This segmentation allows each segment to serve specific functions: the inclined portions facilitate solder flow control while the intermediate portion maintains structural integrity.
2Reliability
If the gate pad area is reduced to improve electrical characteristics, then the electrical performance is improved, but the solder control becomes more difficult
Solution Approach 1:
The lead frame joint portion features localized thickness variation with inclined surfaces that create a natural barrier for solder flow. This local structural quality control prevents solder from spreading beyond the reduced gate pad area, enabling both small pad size and reliable solder joints.
3Quantity of substance
If the solder particle size is reduced to decrease solder amount, then the cost is reduced, but the solder bridge suppression becomes difficult
Solution Approach 1:
The inclined portions of the lead frame joint act as intermediary structures that control solder flow and positioning. These geometric features serve as physical guides that prevent solder bridges between adjacent electrodes, enabling the use of smaller solder particles without compromising reliability.
4Reliability
If the joint portion is processed to match the terminal shape, then the electrical characteristics are improved, but the solder protrusion cannot be prevented
Solution Approach 1:
The joint portion incorporates localized thickness reduction with inclined surfaces at the solder application region. This creates a physical constraint that prevents solder from protruding beyond the terminal upper surface, while still maintaining good electrical contact through the processed joint geometry.
Solution Approach 2:
The inclined portions are designed in advance to create a barrier against solder protrusion before the soldering process occurs. This preliminary structural design prevents the harmful effect of solder protrusion from occurring in the first place.
Data Source
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AI summary
A semiconductor device includes: a lead frame that has one end in contact with the upper surface of the second terminal of the semiconductor element in the sealing portion, and that has the other end exposed from the sealing portion; and a control conductive bonding material that bonds between the upper surface of the second terminal of the semiconductor element and the one end of the lead frame, and the control conductive bonding material having electric conductivity. The one end portion of the lead frame includes: a reference portion; an intermediate portion connected to the reference portion and located on the tip side of the one end portion of the lead frame relative to the reference portion; and an inclined portion connected to the intermediate portion and located at the tip of the one end portion, and the inclined portion having a shape inclined downward from the intermediate portion. Vertical thickness of the inclined portion and the intermediate portion are thinner than a vertical thickness of the reference portion.