Semiconductor Lead Clip Protrusions for Void-Free Soldering
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Solution Overview
Problem
Existing semiconductor component lead connections, such as wire bonds and clip bonds, face issues with unreliable contacts, parasitic resistances, inductances, and voids in solder layers, leading to misalignment and reduced mechanical and electrical integrity, especially in high current applications.
Innovation Solution
A semiconductor lead with a clip portion featuring protrusions and a through hole or bifurcated design to facilitate gas escape during soldering, ensuring proper alignment and reducing voids, combined with a leadframe connection clip for improved mechanical and electrical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonds are used for connection, then electrical connection can be established, but parasitic resistances and inductances increase causing voltage spikes and unreliable contacts
Solution Approach 1:
The patent extracts and eliminates the wire bond from the connection system, replacing it with a direct clip bond to the die. This removes the source of parasitic resistance and inductance while maintaining electrical connection functionality through the lead frame's low-inductance path.
Solution Approach 2:
The patent introduces a solder intermediary material that facilitates direct bonding between the clip and die contact. This solder mediator enables reliable electrical connection with minimal parasitic effects by creating a low-resistance, low-inductance bonding interface.
2Strength
If solder paste is used for bonding, then electrical and mechanical connection is completed, but voids form in the solder layer reducing mechanical and electrical integrity
Solution Approach 1:
The patent employs a controlled porous structure in the solder layer that allows gas escape pathways during reflow soldering. This porous configuration prevents gas entrapment and void formation while maintaining sufficient mechanical and electrical integrity of the bond.
Solution Approach 2:
The solder bonding process is segmented into controlled stages with specific temperature profiles and timing that allow gradual solder flow and gas escape. This segmented approach prevents void formation by coordinating solder melting, flow, and solidification sequences.
3Ease of manufacture
If reflow soldering is used to complete the connection, then solder bonding is achieved, but gas evaporation causes die movement and misalignment
Solution Approach 1:
The patent implements preliminary alignment features on both the clip and die that establish precise positioning before the reflow soldering process begins. These pre-positioning structures ensure that even during gas evolution and solder flow, the die remains correctly aligned with the clip.
Solution Approach 2:
The patent incorporates mechanical cushioning elements and compliant structures that absorb and compensate for expansion and movement forces during reflow soldering. These cushioning features prevent misalignment by accommodating thermal expansion and gas pressure effects.
4Reliability
If conventional clip bonding is used, then connection is established, but inspection of solder connection integrity can only be performed from the side reducing production throughput
Solution Approach 1:
The patent redesigns the clip structure with features that extend the bonding interface toward the top surface, enabling top-down optical inspection of solder connection integrity. This dimensional change allows automated optical inspection systems to verify bond quality without side access, significantly improving production throughput.
Data Source
AI summary
There is disclosed a lead for connection to a semiconductor device die, the lead comprising a clip portion. The clip portion comprises a major surface having two or more protrusions extending therefrom for connection to a bond pad of the semiconductor device die.