Semiconductor Package Clip Standoff for Uniform Solder Bond Lines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor packages with clip connections face issues of uneven bond line thickness (BLT) of solder, leading to clip and die tilting, reliability problems, and degraded electrical performance due to solder cracking during heat cycling.
Innovation Solution
Incorporating protruding standoffs on the surface of vertical semiconductor dies to maintain uniform solder thickness between the die and clip, formed during wafer fabrication to control BLT and prevent tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional clip packages are used without standoffs, then the structure is simpler and manufacturing is easier, but the bond line thickness of solder becomes uneven causing clip and die tilting
Solution Approach 1:
The standoff structures are formed on the die surface during wafer fabrication before packaging, preliminarily establishing the height reference that will control solder thickness. This preliminary action ensures uniform bond line thickness is built into the structure before the soldering process occurs.
Solution Approach 2:
The standoff acts as an intermediary element between the die and the clip, providing a physical height reference that mediates the solder deposition process. This intermediary structure ensures uniform solder thickness by preventing direct contact between the die and clip during reflow.
2Reliability
If solder reflow process is performed without standoffs, then the assembly process is simpler, but the solder moves the clip and die in z direction causing tilt and non-uniformity
Solution Approach 1:
The standoff structures are formed on the die surface during wafer fabrication before packaging, preliminarily establishing the height reference that will control solder thickness. This preliminary action ensures uniform bond line thickness is built into the structure before the soldering process occurs.
Solution Approach 2:
The standoff provides preliminary counter-action to the z-direction movement forces during solder reflow. By providing a physical barrier at a specific height, the standoff prevents the solder from pushing the die and clip together, thereby counteracting the tilting force before it can cause damage.
3Reliability
If uneven bond line thickness occurs, then manufacturing is easier without additional structures, but solder cracking occurs during heat cycling leading to reliability problems
Solution Approach 1:
The standoff structures are formed on the die surface during wafer fabrication before packaging, preliminarily establishing the height reference that will control solder thickness. This preliminary action ensures uniform bond line thickness is built into the structure before the soldering process occurs.
Solution Approach 2:
The standoff acts as an intermediary element between the die and the clip, providing a physical height reference that mediates the solder deposition process. This intermediary structure ensures uniform solder thickness by preventing direct contact between the die and clip during reflow.
4Reliability
If clips and die tilt during assembly, then the assembly process remains simple, but thin solder regions form causing electrical performance degradation
Solution Approach 1:
The standoff structures are formed on the die surface during wafer fabrication before packaging, preliminarily establishing the height reference that will control solder thickness. This preliminary action ensures uniform bond line thickness is built into the structure before the soldering process occurs.
Solution Approach 2:
The standoff acts as an intermediary element between the die and the clip, providing a physical height reference that mediates the solder deposition process. This intermediary structure ensures uniform solder thickness by preventing direct contact between the die and clip during reflow.
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 ensures consistent solder thickness, enhancing the reliability and electrical performance of semiconductor packages by preventing solder cracking and improving thermal management, thus reducing electrical parasitic switching and conduction losses.
Implementation Method 1
During a solder reflow process the solder reflow tends to move the clip and the vertical die in z (height) direction causing tilt
Implementation Method 2
create a protruding standoff(s) on the surface of the vertical die that will maintain the BLT through the solder interface between the vertical die(s) and the clip
Implementation Method 3
A first clip is on the first vertical device that is solder connected to a terminal of the first vertical device on a second side opposite to the first side providing a first solder bonded interface
Implementation Method 4
A vertical semiconductor device is attached on a first side by a die attach material to the die pad
Data Source
AI summary
A semiconductor package includes a leadframe including a die pad and a plurality of lead terminals. A vertical semiconductor device is attached on a first side by a die attach material to the die pad. A first clip is on the first vertical device that is solder connected to a terminal of the first vertical device on a second side opposite to the first side providing a first solder bonded interface, wherein the first clip is connected to at least a first of the lead terminals. The first solder bonded interface includes a first protruding surface standoff therein that extends from a surface on the second side of the first vertical device to physically contact the first clip.