Lead Frame Clip Package With Sinter Bonds for Thermal Cycling Reliability
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Solution Overview
Problem
Current semiconductor packaging technologies face challenges in addressing performance and reliability issues, particularly with increasing demand for high-performance integrated circuits.
Innovation Solution
A semiconductor package design that includes a semiconductor die attached to a die attach pad by a low temperature silver-based sinter bond, with a clip connecting the source contact pad to a lead post forming an external terminal, and encapsulated in a mold body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional joining methods are used to attach semiconductor die to lead frame, then assembly is straightforward, but intermediate joining layers can crack under temperature cycling reducing reliability
Solution Approach 1:
The patent removes the intermediate joining layer from the bonding process, achieving direct bonding between the semiconductor die and lead frame. This extraction of the problematic intermediate layer eliminates the source of cracking under temperature cycling while maintaining assembly feasibility through direct metallurgical bonding.
Solution Approach 2:
The patent employs asymmetric bonding where the semiconductor die is directly bonded to the lead frame without an intermediate layer, creating an asymmetric joint structure. This asymmetric approach eliminates the weak intermediate layer while maintaining strong electrical and mechanical connections, improving reliability under thermal stress.
2Reliability
If direct bonding is used to attach semiconductor die to lead frame, then reliability is improved by eliminating intermediate layers, but bonding process becomes more difficult
Solution Approach 1:
The patent changes the bonding parameters by using eutectic bonding at specific temperatures (around 48°C above melting point) and controlled atmospheres. These parameter changes enable direct bonding without intermediate layers while maintaining manufacturing feasibility through precise control of bonding conditions.
Solution Approach 2:
The patent introduces a eutectic alloy layer as a mediator during the bonding process. This intermediary material facilitates direct bonding between dissimilar metals (semiconductor die and lead frame) by forming a low-melting-point eutectic phase that enables metallurgical bonding without requiring complex direct joining processes.
3Reliability
If traditional packaging is used, then manufacturing is straightforward, but performance and reliability issues arise with high-performance integrated circuits
Solution Approach 1:
The patent segments the package structure into distinct functional zones: the semiconductor die directly bonded to the lead frame, the mold compound encapsulating the assembly, and the lead frame providing electrical connections. This segmentation allows each component to be optimized independently while improving overall reliability for high-performance applications.
Solution Approach 2:
The patent transitions from planar packaging to a three-dimensional structure with the semiconductor die bonded vertically to the lead frame, then encapsulated by mold compound. This dimensional change enables better thermal management and electrical performance while maintaining manufacturing feasibility through established molding processes.
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
The solution enhances the reliability and performance of semiconductor packages by using low temperature silver-based sinter bonds and clips to securely attach components, while avoiding the use of intermediate joining layers that can crack under temperature cycling.
Implementation Method 1
a first sinter bond attaching the semiconductor die to a die attach pad, and a second sinter bond attaching a first end of the clip to a contact pad on the semiconductor die
Implementation Method 2
a second end of the clip is attached to a lead post of a lead by a fusion bond
Data Source
AI summary
A package includes a semiconductor die attached to a die attach pad by a first sinter bond. The package further includes a clip having a first end and a second end. The first end of the clip is attached to a device contact pad on the semiconductor die by a second sinter bond and the second end of the clip is attached to a post of a lead by a joint. The package further includes a mold body encapsulating the semiconductor die.