Lead Frame Connector Structure for Reliable Solder Wetting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Copper connectors with poor solder wettability during the reflow process lead to defective solder joints in semiconductor devices, resulting in unreliable products.
Innovation Solution
The semiconductor device design includes a conductive member with a cut face separated from the bonding face, where the conductive member is bonded using lead solder, and a bending portion that gradually bends the connection portion away from the bonding face, ensuring high wettability and preventing defective joints by utilizing the surface tension and capillary action of the solder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper connector is used for mechanical and electrical connection, then conductivity and mechanical strength are improved, but solder wettability deteriorates causing defective joints
Solution Approach 1:
The patent applies local quality by creating a specific surface structure on the copper connector through controlled oxidation. The connector surface has different regions: an oxidized outer surface layer that improves solder wettability, and an underlying pure copper structure that maintains electrical conductivity and mechanical strength. This local differentiation of surface properties resolves the contradiction between solderability and conductivity.
Solution Approach 2:
The patent changes the physical and chemical parameters of the copper connector surface by controlling oxidation conditions (temperature, time, atmosphere). By adjusting these parameters, the surface forms a specific oxide layer thickness and structure that enhances solder wettability while preserving the bulk copper's electrical properties. This parameter control transforms the surface characteristics without altering the fundamental material properties.
2Strength
If lead solder is used for bonding, then mechanical strength is improved, but misalignment and cracking occur due to poor wettability
Solution Approach 1:
The oxidized surface layer creates local quality changes that enhance solder flow and distribution. The oxide acts as a flux-like substance that promotes uniform solder spreading across the bonding surface, ensuring complete coverage and proper alignment. This local surface modification enables the lead solder to self-align properly during the bonding process.
Solution Approach 2:
The controlled oxidation of the copper connector surface is performed as a preliminary action before the soldering process. This pre-treatment prepares the surface by creating the oxide layer that will facilitate subsequent solder flow and wetting. By performing this surface preparation in advance, the patent ensures optimal bonding conditions are established before the actual joining operation.
3Productivity
If a copper connector with poor solder wettability is used, then manufacturing cost is reduced, but defective joints increase resulting in product rejection
Solution Approach 1:
The patent modifies the surface parameters of the copper connector through controlled oxidation, transforming it from a poor solderable state to an optimized solderable state. This parameter change is achieved through low-cost thermal or chemical oxidation processes that can be integrated into existing manufacturing lines, thereby improving joint reliability without significantly increasing production costs.
Solution Approach 2:
The patent employs oxidation (either thermal oxidation in air or chemical oxidation using mild oxidizing agents) to rapidly create the surface oxide layer on the copper connector. This accelerated oxidation process efficiently transforms the surface properties to enhance solder wettability, resolving the reliability issue while maintaining manufacturing efficiency.
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 enhances the reliability of solder joints by improving wettability and suppressing misalignment and cracking, ensuring a firm bond without altering the manufacturing process.
Implementation Method 1
Mechanical and electrical connection is made by conductive adhesives, such as solder, between the electrode and the connector, and between the lead frame and the connector
Implementation Method 2
ensuring high wettability and preventing defective joints by utilizing the surface tension and capillary action of the solder
Implementation Method 3
utilizing the surface tension and capillary action of the solder
Data Source
AI summary
A semiconductor device of an embodiment includes a first lead frame, a second lead frame located apart from the first lead frame, a semiconductor chip mounted on the first lead frame, and a conductive member. The conductive member electrically connects an electrode of the semiconductor chip to the second lead frame through a conductive adhesive. The conductive member includes a cut face located apart from a bonding face of the electrode, on which the conductive member is bonded.