Semiconductor Bonding Layer Structure for Thermal-Cycle Adhesion
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Solution Overview
Problem
Conventional semiconductor modules face issues with the adhesive strength of polyimide protective layers due to differences in thermal expansion between metal electrodes and resin, leading to reduced insulation and potential peeling during thermal cycling tests.
Innovation Solution
A semiconductor module design featuring a bonding layer of nickel or copper with a gold anti-oxidation layer and a polyimide or polyamide protective layer, where the protective layer is directly applied to the bonding layer's outer peripheral edge, and the arithmetic average roughness of the bonding layer's surface is between 1 μm and 6 μm, enhancing bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyimide protective layer is applied directly to a gold anti-oxidation layer on metal electrodes, then the electrode is protected from oxidation, but the adhesive strength between the protective layer and electrode is insufficient, causing peeling during thermal cycling
Solution Approach 1:
The patent introduces a nickel or copper bonding layer as an intermediary between the gold anti-oxidation layer and the polyimide protective layer. This bonding layer serves as a mediator that provides both oxidation resistance and strong adhesion to the polyimide, resolving the contradiction between protection and adhesion.
Solution Approach 2:
The patent creates a composite electrode structure consisting of multiple layers (metal electrode, nickel/copper bonding layer, gold anti-oxidation layer) that combines the advantages of each material. The composite structure provides both the oxidation resistance of gold and the adhesion properties of nickel/copper, while maintaining compatibility with polyimide.
2Reliability
If the protective layer is made of polyimide resin, then it provides good insulation and protection, but the difference in thermal expansion between the resin and metal electrode causes stress and peeling during thermal cycling
Solution Approach 1:
The nickel or copper bonding layer acts as a thermal expansion buffer between the metal electrode and the polyimide protective layer. This intermediary layer has thermal expansion properties that are intermediate between metal and resin, reducing the stress concentration at the interface during thermal cycling.
Solution Approach 2:
The patent changes the material parameters of the electrode structure by introducing layers with different thermal expansion coefficients. The nickel/copper bonding layer has thermal expansion characteristics that bridge the gap between metal and polyimide, allowing the structure to withstand thermal cycling without peeling.
3Strength
If an amorphous silicon film is inserted between the polyimide and aluminum electrode to improve adhesion, then bonding strength increases, but the solution is not effective when the electrode material is not aluminum
Solution Approach 1:
The patent uses nickel or copper as a universal bonding layer that can adhere to various metal electrode materials (aluminum, copper, etc.) and also provides strong adhesion to polyimide. This universal bonding layer replaces material-specific solutions like amorphous silicon, making the process applicable to different electrode materials.
Solution Approach 2:
The patent changes the approach from using a material-specific intermediate layer (amorphous silicon for aluminum) to using a universally compatible nickel or copper bonding layer. This parameter change in material selection enables the solution to work with various electrode materials while maintaining strong bonding.
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 solution provides high bonding strength between the protective layer and the electrode, preventing peeling and maintaining insulation integrity during thermal stress, thereby improving the reliability of semiconductor modules.
Implementation Method 1
The protective layer is made of a resin, while the electrodes to which the protective layer adheres are made of metal, and therefore the degree of thermal expansion of both materials is different.
Implementation Method 2
The protective layer is made of a resin, while the electrodes to which the protective layer adheres are made of metal, and therefore the degree of thermal expansion of both materials is different.
Data Source
AI summary
A semiconductor module includes: a semiconductor device; a bonding layer that is arranged on the semiconductor device, and contains nickel or copper, an entire back surface of the bonding layer being electrically connected to and in direct contact with an electrode in the semiconductor device; an anti-oxidation layer disposed on the bonding layer; and a protective layer disposed directly on a top surface of a peripheral portion of the bonding layer on which the anti-oxidation layer is absent, covering an outer peripheral edge of the bonding layer, wherein the protective layer is made of an electrically insulating resin.