Lead Frame Silver Oxide Layer Adhesion
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Solution Overview
Problem
Conventional lead frames with silver-plated layers suffer from insufficient adhesive strength between the silver-plated layer and the molding compound, leading to delamination after moisture absorption, and surface roughening to improve this also reduces bonding forces with bonding wires, causing wire disconnection and open circuit failures.
Innovation Solution
A lead frame structure comprising a metal base with a silver-plated layer and a polar silver oxide layer, where the silver oxide layer is between the metal base and the silver-plated layer, with a thickness of 1.3 to 2.5 nanometers, enhancing adhesive strength with the molding compound while maintaining bonding forces with wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a masking layer is formed to create a roughened mounting surface, then adhesive strength to molding compound is improved, but device complexity increases
Solution Approach 1:
The invention merges the masking layer formation with the existing silver plating process. The masking layer is deposited concurrently with the silver plating layer in a single manufacturing step, eliminating the need for separate masking and plating operations. This integration reduces process complexity while achieving the dual functionality of roughened mounting surface and smooth bonding surface.
Solution Approach 2:
The masking layer serves multiple functions simultaneously: it acts as a protective mask during etching, provides a bonding surface for wire attachment, and defines the pattern for the roughened mounting area. This multi-functionality reduces the need for additional components or processes, thereby minimizing device complexity.
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 lead frame achieves improved adhesive strength with the molding compound and maintains bonding forces with wires, reducing delamination and wire disconnection issues, and can pass more severe moisture sensitivity levels.
Implementation Method 1
the adhesive strength between the silver-plated layer and the molding compound is insufficient. Thus, the molding compound is apt to delaminate from the lead frame after moisture absorption occurs.
Implementation Method 2
a die is mounted onto the silver-plated layer of the lead frame and electrically connected with the silver-plated layer by multiple bonding wires
Data Source
AI summary
A lead frame has a metal base, a silver-plated layer, and a silver oxide layer. The silver-plated layer is formed between the metal base and the silver oxide layer. The silver oxide layer has a polar outer surface and a thickness of equal to or more than 1.3 nanometers. The silver oxide layer is beneficial to increase the adhesive strength between the lead frame and the molding compound and avoid delamination of the molding compound from the lead frame, so the lead frame of the present invention can pass a more severe moisture sensitivity level when exposed to the environment.