Semiconductor Power Module Lead Frame Surface Roughness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor power modules, the connection of lead frames to chips with solder can result in solder shorts and inadequate adhesion, leading to connection failures and chip displacement, while the use of molding resin to enhance adhesion can be compromised by low peeling resistance and increased crack development, which shortens the solder's fatigue life.
Innovation Solution
A semiconductor device design where the second lead frame has a base portion integrally formed with it, with a roughened surface for molding resin contact and a smooth surface for solder connection, preventing solder wetting on side surfaces and enhancing adhesion, thereby reducing connection failures and peeling risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base portion and lead frame are connected with solder, then the solder wettability of the base portion is improved, but the side surfaces of the base portion become wet with solder causing connection failures and chip displacement
Solution Approach 1:
The base portion is designed with different surface roughness for different regions: the main surface has higher roughness to prevent solder wetting and improve reliability, while the connection surface has lower roughness to ensure proper solder connection. This local differentiation of surface properties resolves the contradiction between preventing unwanted solder wetting and ensuring proper solder connection.
2Strength
If molding resin is used to seal components, then adhesion between lead frames and molding resin is improved, but peeling occurs at the interface causing chip break and reduced fatigue life
Solution Approach 1:
The lead frame surface is designed with different roughness characteristics for different regions: the main surface has higher roughness to enhance adhesion strength with molding resin, while the connection surface maintains lower roughness to prevent excessive solder wetting. This local differentiation resolves the contradiction between achieving strong adhesion and ensuring long fatigue life.
3Temperature
If flat lead frames are used for double-side cooling, then heat dissipation is improved, but solder on opposite sides may contact causing short circuits
Solution Approach 1:
The base portion is designed with a protruding structure that extends in the vertical dimension between the two lead frames. This dimensional addition creates physical separation between the solder layers on opposite sides of the chip, preventing short circuits while maintaining the double-side cooling configuration for effective heat dissipation.
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 significantly reduces solder connection failures and chip displacement, while improving the adhesion of molding resin, resulting in a more reliable and longer-lasting semiconductor device with reduced peeling and crack development.
Implementation Method 1
the solder wettability of the base portion 3a is important. If the wettability of the solder connection surface of the base portion 3a is equal to the wettability of the side surfaces of the base portion and the periphery thereof, the side surfaces of the base portion 3a will become wet with the solder 2 during solder connection
Implementation Method 2
the molding resin is required to have a high degree of adhesion. If the degree of adhesion is low and the lead frames thus peel off the molding resin, there is a possibility that the peeling may develop
Data Source
AI summary
The present invention relates to a power module obtained by connecting the opposite sides of a chip with solder, and prevents the side surfaces of a base portion from becoming wet with solder, which would otherwise cause connection failures of the solder or chip displacement, and also prevents peeling of molding resin, which would otherwise break the chip or shorten the life of the solder. The base portion is integrally formed with one of lead frames, and the side surfaces of the base portion and the surface of the main body of the lead frame are roughened so as to have reduced solder wettability. Meanwhile, the solder connection surface of the base portion is not roughened so as to ensure the solder wettability. Accordingly, it is possible to reduce failures that may occur during solder connection and obtain a highly reliable power module (FIG. 5).