Semiconductor Lead Structure for Reflow Solder Alignment
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Solution Overview
Problem
Conventional semiconductor devices face displacement issues of the connection lead during the reflow process, leading to improper electrical connections due to inadequate surface contact areas and surface tension distribution.
Innovation Solution
The semiconductor device design includes a connection lead with a lead-connecting-portion second surface area larger than the lead-connecting-portion first surface area, utilizing the surface tension of molten solder to maintain the connection lead's position relative to the second lead, ensuring proper alignment and reducing displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the connection lead is soldered to the second lead using a reflow process, then electrical connection is achieved, but the connection lead may be unduly displaced relative to the semiconductor element and/or the second lead
Solution Approach 1:
The patent applies preliminary action by forming a protrusion on the connection lead before the reflow process, and pre-positioning solder paste in the recess of the second lead. This preliminary preparation ensures that during the reflow process, the molten solder is guided to flow into the protrusion-recess interface, thereby preventing displacement of the connection lead while achieving reliable electrical connection.
2Manufacturing precision
If the connection lead is secured firmly to prevent displacement, then positioning accuracy is improved, but the reflow process may not be effective in achieving proper solder bonding
Solution Approach 1:
The patent introduces an intermediary mechanism where the protrusion on the connection lead and the corresponding recess in the second lead act as guiding structures. These structures mediate between the connection lead and the second lead, ensuring proper alignment and positioning while allowing the solder to flow and bond effectively during the reflow process.
3Reliability
If the surface contact area between the connection lead and solder is increased, then solder bonding is improved, but the surface tension distribution may not be sufficient to prevent displacement
Solution Approach 1:
The patent applies local quality by creating a protrusion at a specific location on the connection lead and a corresponding recess in the second lead. This localized structural modification concentrates the surface tension effect of the molten solder at the protrusion-recess interface, providing sufficient displacement control while maintaining adequate solder bonding through the enhanced local contact area.
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 the displacement of the connection lead, maintaining a predetermined position and ensuring reliable electrical connections by leveraging the surface tension of solder in the reflow process.
Implementation Method 1
the second surface of the connection lead is drawn toward the first recess side surface of the second lead by the surface tension of molten solder in the reflow process
Data Source
AI summary
A semiconductor device includes a semiconductor element, a first lead supporting the semiconductor element, a second lead separated from the first lead, and a connection lead electrically connecting the semiconductor element to the second lead. The connection lead has an end portion soldered to the second lead. This connection-lead end portion has a first surface facing the semiconductor element and a second surface opposite to the first surface. The second lead is formed with a recess that is open toward the semiconductor element. The recess has a side surface facing the second surface of the connection-lead end portion. A solder contact area of the second surface of the connection-lead end portion is larger than a solder contact area of the first surface of the connection-lead end portion.