Lead Frame Wettability Zoning for Power Module Solder Control
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Solution Overview
Problem
In semiconductor devices, the solder joint between the semiconductor chip and metal plates is prone to uneven solder wetting due to the projecting shape of the metal plates, leading to quality and productivity issues.
Innovation Solution
A semiconductor device design featuring a lead frame with a solder surface and a solder resistance surface, where the solder resistance surface is less wettable than the solder surface and surrounds the periphery of the solder surface, allowing controlled solder wetting and joint formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the metal plate has a projecting shape to enhance heat dissipation, then the heat dissipation performance is improved, but the solder wetting becomes uneven and difficult to control
Solution Approach 1:
The lead frame is designed with different surface properties in different regions: the solder surface has high solder wettability while the solder resistance surface has low solder wettability. This local differentiation allows the solder to wet only the intended areas (solder surface) and not the peripheral areas (solder resistance surface), thereby controlling solder wetting precision while maintaining the projecting shape for heat dissipation.
2Temperature
If the metal plate has a projecting shape, then the heat dissipation performance is improved, but the quality and productivity deteriorate due to uneven solder wetting
Solution Approach 1:
By creating distinct zones with different solder wettability characteristics on the lead frame surface, the invention ensures consistent and predictable solder wetting behavior. This eliminates the need for rework or inspection corrections, thereby improving both quality and productivity while maintaining the heat dissipation-enhancing projecting shape.
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 precise control over the solder wetting region, improving the quality and productivity of the solder joint process.
Implementation Method 1
a solder surface that is in contact with the first solder material and a solder resistance surface on which the first solder material is less wettable than on the solder surface
Data Source
AI summary
A power semiconductor module, which is a semiconductor device, includes a semiconductor element 155 and a lead frame 318 that is disposed to face the semiconductor element 155 and connected to the semiconductor element 155 by a solder material 162. The lead frame 318 has the top surface 331 including a surface facing the semiconductor element 155, and the side surface 334 connected to the peripheral edge portion 333 of the top surface 331 at a predetermined angle with respect to the top surface 331. The top surface of the lead frame 318 includes the solder surface 332 that is in contact with the solder material 162 and the solder resistance surface on which the solder material 162 is less wettable than on the solder surface 332. The solder resistance surface is formed to surround the periphery of the solder surface 332. In this manner, when the semiconductor element and the lead frame are solder-joined in the semiconductor device, the region where the solder wet-spreads is appropriately controlled.