Semiconductor Lead Concave Slope for Burr Removal and Solder Wettability
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Solution Overview
Problem
Semiconductor devices face issues with metal burrs causing short circuits and poor solder wettability leading to limited mounting strength, making it difficult to visually check solder connections and assemble effectively on mounting boards.
Innovation Solution
A semiconductor device manufacturing method involving forming a concave portion on the outer side of leads with a forward-tapered slope surface, followed by isotropic etching to remove metal burrs and improve solder wettability, allowing for easier visual inspection and enhanced board mounting properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lead is cut along with the sealing resin by dicing, then the semiconductor device can be separated into individual pieces, but metal burr is formed on the sealing resin causing short circuits
Solution Approach 1:
The lead end surface is ground flat before the dicing process to remove potential metal burrs that would form during cutting. This preliminary action prevents the formation of harmful metal burrs on the sealing resin surface during subsequent dicing operations, eliminating the short circuit risk while maintaining efficient device separation
2Ease of operation
If the lead side surfaces are used for mounting, then the semiconductor device can be assembled on mounting board, but the solder wettability is poor limiting mounting strength
Solution Approach 1:
The lead end surface (not the side surface) is ground flat to create a localized area with improved solder wettability. This selective surface treatment enhances the mounting strength at the critical bonding interface without requiring changes to the overall lead geometry or mounting process
Solution Approach 2:
The surface roughness and crystallographic orientation of the lead end surface are modified through grinding to improve solder wettability. This parameter change in surface properties enables better solder adhesion and stronger mounting connections
3Reliability
If the lead top surface is in contact with resin, then the lead is protected and sealed, but the solder connection cannot be made on the top surface limiting mounting options
Solution Approach 1:
The mounting connection interface is shifted from the horizontal top surface to the vertical end surface of the lead. By utilizing the end surface (a different dimensional orientation) for solder connection while keeping the top surface sealed by resin, the invention provides both protection and mounting versatility
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 method prevents short circuits, improves solder connection strength, and allows for easier visual inspection of solder connections, resulting in improved board mounting properties and reduced risk of short circuits during assembly.
Implementation Method 1
first etching isotropically a part of the each of the plurality of leads that is exposed in the first cut area
Data Source
AI summary
In a semiconductor device (4), a semiconductor chip (10) is mounted on a die pad (6) which has a die pad overhang portion (6a) and leads (9) are arranged around and apart from the die pad (6). The leads (9) and the semiconductor chip (10) are electrically connected and are covered with a sealing resin (8). A concave portion (7e) is formed on the outer side of each lead (9), i.e., the far side from the die pad. A lead concave surface (7d) facing the concave portion (7e) includes a forward-tapered lead slope surface (7h). Side surface of the sealing resin (8) has a step of a staircase shape formed from the first and the second resin side surfaces (8a and 8b). A tip of the lead (9) protrudes past the first resin side surface (8a).