Lead Frame Assembly With Oxide Films for Solder Wetting Control
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Solution Overview
Problem
In electronic component apparatuses using lead frames, the wetting and spreading of solder during reflow cannot be effectively controlled, leading to potential contact between adjacent solder bumps and reduced adhesiveness between the lead frame and insulating resin.
Innovation Solution
The apparatus includes a configuration with two lead frames and an insulating resin, where oxide films are formed on the surfaces of the lead frames to control solder wetting and spreading, and solder balls are used to connect the lead frames while being thicker than the electronic components, ensuring proper spacing and embedding of the components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder bumps are used for flip-chip mounting on lead frame, then electrical connection is achieved, but solder wetting and spreading cannot be controlled causing adjacent solder bumps to contact each other
Solution Approach 1:
The patent introduces an intermediary layer (oxide film or organic substance) between the solder bumps and the lead frame surface. This intermediary layer acts as a barrier that prevents solder wetting and spreading, thereby maintaining the spacing between adjacent solder bumps while still allowing electrical connection through the controlled interface.
Solution Approach 2:
The patent changes the surface properties of the lead frame by forming an oxide film or applying an organic substance coating. This parameter change in surface chemistry and energy reduces the wetting characteristics of the solder, preventing unwanted spreading and maintaining precise bump spacing during the reflow process.
2Device complexity
If conventional lead frame structure is used, then assembly is simplified, but adhesiveness between lead frame and insulating resin is reduced
Solution Approach 1:
The patent creates a composite structure by forming an oxide film or applying an organic substance coating on the lead frame surface. This composite interface between the metal lead frame and the coating layer enhances the chemical and mechanical adhesion to the insulating resin, while the overall assembly structure remains relatively simple.
3Reliability
If solder balls are used to connect lead frames, then electrical connection is established, but solder wetting and spreading causes loss of solder material and potential defects
Solution Approach 1:
The intermediary layer (oxide film or organic substance) on the lead frame surface acts as a controlled barrier that limits solder wetting and spreading. This prevents excess solder material from migrating to unwanted areas while still allowing sufficient solder to form reliable electrical connections at the intended contact points.
Solution Approach 2:
By changing the surface energy parameters of the lead frame through oxide formation or organic coating, the patent controls the wetting behavior of solder balls. This parameter modification ensures that solder material is retained at the connection points without excessive spreading, reducing material loss and preventing defects.
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 configuration suppresses solder wetting and spreading, prevents adjacent solder balls from contacting each other, and improves the accuracy and reliability of the assembly process by maintaining the separation distance between lead frames, thus enhancing the structural integrity and assembly precision.
Implementation Method 1
the wetting and spreading of solder cannot be controlled during reflow
Data Source
AI summary
An electronic component includes: a first lead frame; a second lead frame that is provided on the first lead frame; a first electronic component that is provided between the first lead frame and the second lead frame; a connection member that is provided between the first lead frame and the second lead frame; and an insulating resin that is filled between the first lead frame and the second lead frame so as to cover the first electronic component and the connection member. A first oxide film is provided on a surface of the first lead frame. A second oxide film is provided on a surface of the second lead frame. The first lead frame and the second lead frame are electrically connected to each other by the connection member.