Leadframe Leads With Fully Plated End Faces for AOI
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Solution Overview
Problem
Semiconductor devices with leadless or short lead packages are unsuitable for automated optical inspection (AOI) due to the inability of solder to form a fillet on the end face of the leads, preventing effective inspection of solder wetting between the device and a circuit board.
Innovation Solution
The semiconductor device includes a leadframe with fully plated end faces on its leads, allowing for solder wetting and enabling AOI by ensuring the end faces are not severed during singulation from a leadframe strip, with the leads having unplated sidewalls and plated end faces that extend between the main faces of the leadframe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If leadless or short lead packages are used to reduce device complexity and improve integration, then device complexity is reduced and productivity is improved, but automated optical inspection capability is lost due to inability to form solder fillet
Solution Approach 1:
The lead structure is designed with differentiated plating characteristics: the end face is fully plated to enable solder wetting and fillet formation for AOI inspection, while the sidewalls remain unplated. This local quality differentiation allows the lead to serve dual purposes - maintaining simple package structure while enabling inspection capability at the critical end face location.
Solution Approach 2:
The end face of the lead is pre-plated with solderable material before the soldering process. This preliminary plating action ensures that when solder is applied during assembly, it can properly wet the end face and form a visible fillet, enabling subsequent AOI inspection without requiring complex package structures.
2Productivity
If leads are severed during singulation from leadframe strip to create individual leads, then device integration is improved, but the end face plating is removed preventing solder wetting and AOI
Solution Approach 1:
The singulation process is designed to selectively affect only the sidewalls of the leads, leaving the end faces intact. This localized approach allows the leads to be separated for individual device integration while preserving the critical end face plating needed for reliable solder joints and AOI inspection.
Solution Approach 2:
The lead structure is segmented into two distinct regions with different treatments: the sidewalls are unplated and intended to be severed during singulation, while the end faces are fully plated and preserved. This segmentation allows the singulation process to proceed without compromising the solder joint reliability at the end faces.
3Difficulty of detecting and measuring
If fully plated end faces are implemented on leads, then automated optical inspection capability is enabled through solder fillet formation, but manufacturing complexity increases
Solution Approach 1:
Instead of plating the entire lead structure, the plating is applied only to the end faces where it is critically needed for solder wetting and AOI inspection. This localized plating approach enables inspection capability while minimizing the added manufacturing complexity compared to full lead plating.
Solution Approach 2:
The end faces are pre-plated with solderable material during the lead fabrication process, before the leads are attached to the package body. This preliminary plating action simplifies the overall manufacturing process by ensuring inspection capability is built-in from the start, rather than requiring additional post-assembly steps.
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 design enables the formation of a solder fillet suitable for AOI, allowing for effective inspection of solder wetting between the semiconductor device and a circuit board, enhancing the reliability of the inspection process.
Implementation Method 1
allowing for solder wetting and enabling AOI by ensuring the end faces are not severed during singulation
Data Source
AI summary
A semiconductor device includes a leadframe, a semiconductor die attached to the leadframe, and an encapsulation material encapsulating the semiconductor die and a portion of the leadframe. The leadframe includes a first main face and a second main face opposite to the first main face. The leadframe includes leads wherein each lead includes a fully plated end face extending between an unplated first sidewall and an unplated second sidewall opposite to the first sidewall. The end face and the first and second sidewalls of each lead are perpendicular to the first and second main faces.