Lead Frame Tin-Block Structure for Full-Surface Pin Soldering
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Solution Overview
Problem
Traditional semiconductor packaging methods result in insufficient solder around pins due to uneven tin distribution, failing to meet automotive product and AOI detection standards.
Innovation Solution
A manufacturing method involving the formation of through holes in lead frames with tin blocks, where the tin blocks are partially exposed on the cutting surface, allowing for all-position soldering when the semiconductor packaging member is assembled, ensuring even tin distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electroplating is used to form tin-plated layer on base island and pin back surface, then the mounting surface has sufficient tin, but the cutting surface has almost no tin resulting in insufficient solder around pin
Solution Approach 1:
The pin is segmented into two distinct tin supply zones: a tin-plated layer on the back surface for mounting, and a tin block embedded in a through-hole for the cutting surface. This segmentation allows independent optimization of tin distribution at different locations, ensuring sufficient solder material is available at both the mounting surface and cutting surface without compromising manufacturing precision.
Solution Approach 2:
The tin block is pre-installed in the through-hole of the pin before the cutting process. This preliminary action ensures that when the pin is cut, the exposed cutting surface already has adequate tin material available, eliminating the need for post-cutting tin application and ensuring consistent solder reliability from the outset.
2Reliability
If tin-plated layer is formed only on back surface, then mounting surface has tin, but cutting surface without tinning fails to satisfy AOI detection standards
Solution Approach 1:
The tin block is nested within the through-hole of the pin, with the through-hole acting as a cavity that accommodates the tin block. This nested structure allows the tin block to be integrated into the pin body without significantly increasing external dimensions or structural complexity, while still providing the necessary tin exposure on the cutting surface for AOI detection compliance.
Solution Approach 2:
The tin block serves as a localized copy of the tin-plating function, providing the necessary solder material and reflectivity properties on the cutting surface without requiring a complete tin-plating process across the entire pin surface, thus maintaining structural simplicity while meeting detection standards.
3Reliability
If through hole with tin block is formed in outer pin, then all-position soldering is achieved, but manufacturing process steps increase
Solution Approach 1:
The tin block is pre-installed in the through-hole during the lead frame assembly process, before the actual soldering operation. This preliminary preparation ensures that when soldering occurs, the tin block is already in position to provide molten tin for all-position soldering, eliminating the need for multiple soldering passes or additional tin application steps, thereby maintaining manufacturing efficiency while achieving complete soldering coverage.
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
Enhances solder reliability and stability, improving AOI detection pass rates and reducing power consumption by ensuring comprehensive soldering across the pin surfaces.
Implementation Method 1
a tin block disposed in the through hole, wherein a side of the tin block away from the inner pin is at least partially exposed... part of the melted tin block on a side of the outer pin away from an inner pin is connected to a tin-plated layer on a back surface of the outer pin
Implementation Method 2
soldering the semiconductor packaging member on a circuit board, wherein a tin block on an outer pin is melted during soldering
Data Source
AI summary
The present invention provides a manufacturing method of a semiconductor packaging member, a semiconductor packaging member and a mounting method thereof. The manufacturing method of the semiconductor packaging member includes the following steps of: forming a through hole running through vertically in an outer pin of a lead frame, and disposing a tin block in the through hole; and cutting the lead frame to at least partially expose a side of the tin block located on a cutting surface. Subsequently, when the semiconductor packaging member is soldered on a circuit board, the tin block is melted to realize all-position soldering from a front surface to side surfaces and a back surface, and even the interior of the outer pin, thereby improving the reliability of a circuit, and effectively improving the stability and the pass rate in AOI detection.