Semiconductor Bonding Layer Structure to Prevent Protective Layer Peeling
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Solution Overview
Problem
Conventional semiconductor modules face issues with the adhesive strength between polyimide protective layers and metal electrodes due to differences in thermal expansion, 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 solder portion and a polyimide or polyamide protective layer, where the bonding layer's surface roughness is between 1 μm and 6 μm, and the protective layer is directly applied to the bonding layer's outer peripheral edge, enhancing adhesion and preventing peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyimide protective layer is applied directly on a gold anti-oxidation layer, then the electrode is protected from oxidation, but the adhesive strength between the protective layer and the electrode is insufficient, causing peeling during thermal cycling
Solution Approach 1:
The patent introduces a nickel bonding layer as an intermediary between the gold anti-oxidation layer and the polyimide protective layer. The nickel layer serves as a mediator that provides strong adhesion to both the gold layer below and the polyimide layer above, resolving the adhesion problem while maintaining oxidation protection. The nickel bonding layer has superior bonding characteristics with polyimide compared to gold, eliminating peeling during thermal cycling.
Solution Approach 2:
The electrode structure uses a composite material approach by combining nickel and gold in specific layers. The nickel bonding layer provides adhesion functionality, while the gold anti-oxidation layer provides oxidation resistance. This composite structure leverages the complementary properties of different materials to achieve both strong bonding and corrosion protection.
2Reliability
If the protective layer is made of polyimide for insulation protection, then electrical insulation is provided, but thermal expansion differences between polyimide and metal electrodes cause stress and peeling during thermal cycling
Solution Approach 1:
The nickel bonding layer acts as a stress-absorbing intermediary that accommodates thermal expansion differences between the polyimide protective layer and the metal electrode. This intermediate layer has mechanical properties that bridge the gap between the rigid metal and the polymer, reducing stress concentration and preventing peeling during thermal cycling while maintaining insulation integrity.
3Strength
If an amorphous silicon film or hexamethyldisilane film is interposed between polyimide and aluminum to improve adhesion, then bonding strength is enhanced for aluminum electrodes, but the solution is not effective when the electrode material is other than aluminum
Solution Approach 1:
The nickel bonding layer provides universal adhesion capability with polyimide regardless of the underlying metal electrode material. Unlike aluminum-specific solutions such as amorphous silicon or hexamethyldisilane films, the nickel layer maintains strong bonding characteristics with polyimide across different metal substrates, making it applicable to various electrode materials including copper, aluminum, and other metals.
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, reducing the likelihood of peeling and maintaining insulation integrity during thermal stress, thereby improving the reliability of semiconductor modules.
Implementation Method 1
the bonding layer's surface roughness is between 1 μm and 6 μm, and the protective layer is directly applied to the bonding layer's outer peripheral edge, enhancing adhesion
Implementation Method 2
a protective layer disposed directly on the bonding layer, covering an outer peripheral edge of the bonding layer
Data Source
AI summary
A semiconductor module includes: a semiconductor device; a bonding layer that is arranged on the semiconductor device, contains nickel or copper, and is electrically connected to the semiconductor device; a solder portion containing gold, disposed on the bonding layer; and a protective layer disposed directly on the bonding layer, covering an outer peripheral edge of the bonding layer.