Semiconductor Clip Positioning With Stud Bumps to Prevent Tilt
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power semiconductor devices face issues with accurate clip positioning and solder thickness control during assembly, leading to potential displacement and excessive tilt of clips during the soldering process, resulting in defective products.
Innovation Solution
The implementation of complementary positioning formations, such as stud bumps on the pad and recesses in the clip, which engage to maintain precise alignment and prevent displacement, along with spacer stud bumps to control solder thickness and prevent clip tilt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If clips are placed using conventional clip attach equipment, then chip placement accuracy is initially adequate, but clips become displaced during handling and curing process
Solution Approach 1:
Positioning formations (cavities in clip, protrusions in leadframe) are created in advance before the soldering process. These pre-formed mechanical features ensure that when the clip is placed, it automatically aligns with the leadframe pad through the engagement of these formations, preventing displacement during subsequent handling and curing operations.
Solution Approach 2:
The positioning formations act as intermediary mechanical features between the clip and leadframe. The cavities and protrusions serve as mediating elements that transfer and maintain precise positional alignment, ensuring the clip remains correctly positioned relative to the pad throughout the assembly process.
2Reliability
If solder paste is used to connect clip to pad and die, then electrical connection is achieved, but excessive clip tilt occurs due to solder thickness and floating tendency
Solution Approach 1:
The positioning formations are prepared in advance to control the solder thickness and prevent clip floating. By having pre-formed cavities and protrusions, the solder paste is constrained to specific areas, maintaining consistent thickness and preventing the clip from tilting during the soldering process.
Solution Approach 2:
The positioning formations serve as intermediaries that mediate between the clip and the solder paste. The mechanical engagement of cavities and protrusions provides a reference framework that limits solder flow and prevents excessive clip tilt, while still allowing adequate solder connection.
3Ease of manufacture
If no positioning formations are provided, then assembly process is simpler, but clip displacement and tilt result in defective products
Solution Approach 1:
The positioning system is segmented into two complementary parts: cavities formed in the clip and protrusions formed in the leadframe pad. This segmentation allows each component to be manufactured independently with its positioning feature, then assembled together with precise alignment through the engagement of these segmented elements.
Solution Approach 2:
The positioning formations enable self-alignment during assembly. When the clip is placed over the pad, the cavities automatically engage with the protrusions, causing the clip to self-position correctly without requiring complex external alignment equipment or procedures.
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 solution ensures accurate clip positioning and controlled solder thickness, effectively preventing undesired movement and tilt, thereby reducing defects in the final product.
Implementation Method 1
a solder paste is used to connect the clip to pad and die. Solder curing in an oven is applied to provide a solid connection of clips to pad and die.
Data Source
Figure 1~3
Figure 4~6
AI summary
A semiconductor device comprises one or more electrically conductive clips (18) arranged in a bridge-like position between a semiconductor chip (142) and an electrically conductive pad (12B). The clip (18) is soldered to the semiconductor chip (142) and to the electrically conductive pad (12B) via soldering material (22) applied at coupling surfaces facing towards the semiconductor chip (142) and the electrically conductive pad (12B). Prior to positioning the clip (18) in a bridge-like position between the semiconductor chip (142) and the electrically conductive pad (12B), one or more pairs of complementary positioning formations (100, 102) are formed comprising a cavity (102) formed in the electrically conductive clip (18) and a protrusion (100) comprised of a stack of stud bumps is formed in the electrically conductive pad (12B). With the electrically conductive clip (18) in a desired bridge-like position, the complementary positioning formations (100, 102) are mutually engaged and retain the conductive clip (18) in such a desired bridge-like position avoiding displacement during soldering.