Semiconductor Lead Surface Plating for Solder Bonding Strength
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Solution Overview
Problem
Conventional semiconductor devices experience reduced mounting strength due to stress-induced solder cracking or detachment from circuit boards, particularly in varying usage environments.
Innovation Solution
A semiconductor device design featuring leads with surface plating layers formed through substitutional electroless plating on exposed portions, enhancing solder wettability and bonding strength when mounted on a circuit board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional leads without surface plating are used, then the device structure remains simple, but the solder bonding strength decreases and solder cracking occurs under stress
Solution Approach 1:
The patent applies surface plating layers (such as tin, silver, or copper plating) specifically on the exposed portions of the leads that contact the solder, while leaving other portions of the lead structure unchanged. This local modification enhances solder wettability and bonding strength at the critical bonding interface without unnecessarily complicating the overall lead structure, thereby resolving the contradiction between bonding strength and structural simplicity.
Solution Approach 2:
The patent changes the surface properties of the lead by applying different plating materials and thicknesses to improve solderability. By adjusting plating parameters (material composition, thickness, surface roughness), the bonding strength can be optimized without fundamentally altering the lead's structural design, thus maintaining relative simplicity while achieving enhanced bonding performance.
2Reliability
If stress-resistant solder bonding is achieved through surface plating, then mounting reliability improves, but manufacturing process complexity increases
Solution Approach 1:
The surface plating is applied to the leads during the manufacturing process before the semiconductor device is assembled and mounted. This preliminary preparation of the lead surface ensures that the bonding interface is already optimized for solder attachment, preventing future bonding failures and reducing the need for rework or additional stress-compensation measures during assembly, thereby improving reliability without excessive manufacturing complexity.
Solution Approach 2:
The surface plating layer acts as an intermediary between the lead base material and the solder. This intermediate layer improves interfacial bonding, reduces direct stress transmission to the lead-solder interface, and prevents solder cracking by providing a more compliant and adherent bonding surface, thus enhancing mounting reliability through a controlled intermediate structure.
3Strength
If surface plating is applied to lead exposed portions, then solder wettability and bonding strength improve, but material cost and plating process complexity increase
Solution Approach 1:
The patent applies surface plating only to the exposed portions of the leads that will contact the solder, rather than plating the entire lead structure. This selective local plating minimizes material consumption and reduces plating process complexity while still achieving the desired bonding strength improvement at the critical bonding interface, thereby balancing manufacturing ease with bonding performance.
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 surface plating layers improve the bonding strength between the semiconductor device and the circuit board, reducing the likelihood of solder cracking and detachment, thereby enhancing the overall mounting reliability.
Implementation Method 1
By substitutional electroless plating, a surface plating layer is formed at least on a part of exposed portions of the lead frame that are exposed from the sealing resin
Data Source
AI summary
A semiconductor device includes a predetermined number of leads, a semiconductor element electrically connected to the leads and supported by one of the leads, and a sealing resin that covers the semiconductor element and a part of each lead. Each lead includes some portions exposed from the sealing resin. A surface plating layer is formed on at least one of the exposed portions of the respective leads.