Semiconductor Clip Through-Hole Curvature for Solder Void Escape
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Solution Overview
Problem
Voids formed during the reflow process in soldering semiconductor packages can negatively impact the mechanical and electrical performance of chip-to-clip or chip-to-leadframe connections, necessitating a solution to effectively remove these voids.
Innovation Solution
A clip with a die attach portion featuring a curved transition in its through-holes, which acts as an escape channel for voids, reducing capillary forces and facilitating their removal during the reflow process, is used in conjunction with a method for fabricating semiconductor packages that includes attaching the clip to a semiconductor die using a solder layer and encapsulating it with an encapsulation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional through-hole with sharp edges is used in the clip, then the manufacturing process is simpler, but capillary forces prevent voids from escaping during reflow
Solution Approach 1:
The through-hole is designed with a curved transition zone instead of sharp edges, creating a rounded geometry that reduces capillary forces and enables void escape during reflow soldering. The curved transition has a radius R between 0.05 mm and 0.5 mm, transforming the hole shape from angular to curved to achieve the desired void removal function.
2Strength
If solder material is applied to connect the clip and semiconductor die, then mechanical and electrical connection is established, but voids form during reflow that degrade connection quality
Solution Approach 1:
The curved transition geometry converts the potentially harmful void formation during soldering into a beneficial void escape mechanism. By designing the through-hole with curved transitions, the structure actively guides and expels voids formed during reflow, transforming the harmful effect of void generation into a controlled void removal process that improves connection quality.
3Reliability
If the through-hole has a large radius curved transition, then void escape is facilitated, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a parameter range for the curved transition radius R between 0.05 mm and 0.5 mm, allowing optimization of void escape efficiency while accommodating manufacturing capabilities. This parameter definition balances the need for effective void removal with practical manufacturing constraints, providing a feasible design space for production.
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 curved transition in the clip's through-holes allows voids to escape smoothly, enhancing the mechanical and electrical reliability of the semiconductor package connections by preventing voids from obstructing the solder layer, thus improving the overall performance of the chip-to-clip and chip-to-leadframe connections.
Implementation Method 1
The curved edge allows the voids to more easily and more smoothly move into the through-hole and along an outer contour of the clip. In contrast thereto, sharp edges would act as barriers for the voids due to capillary forces.
Data Source
AI summary
A clip, a semiconductor package, and a method are disclosed. In one example the clip includes a die attach portion having a first main face and a second main face opposite to the first main face, and at least one through-hole extending between the first and second main faces and including a curved transition from an inner wall of the at least one through-hole to the first main face.