Multilayer Ceramic Capacitor Plating for Hydrogen Release
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Solution Overview
Problem
Multilayer ceramic capacitors face issues with decreased insulation resistance characteristics due to occluded hydrogen in Ni-plated layers, which also allows moisture infiltration, compromising their electrical performance and reliability.
Innovation Solution
Incorporating an intermetallic compound, such as NiSn4, within the Sn-plated layer that penetrates through the thickness direction, allowing hydrogen to pass more easily and preventing moisture infiltration, thereby maintaining insulation resistance and board mountability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dense Sn-plated layer is used to improve solderability, then solderability is improved, but hydrogen permeability deteriorates causing hydrogen occlusion
Solution Approach 1:
The Sn-plated layer is designed with a porous structure containing voids and intermetallic compound regions that allow hydrogen to permeate through while maintaining a dense overall appearance for good solderability. The porous structure provides hydrogen escape paths without compromising the protective function of the Sn layer.
Solution Approach 2:
The external electrode is constructed as a composite structure with multiple layers including Ni-plated layer, Sn-plated layer, and intermetallic compound regions. This composite structure combines the benefits of different materials: Ni provides base protection, Sn provides solderability, and the intermetallic compounds provide hydrogen permeability channels.
2Object-generated harmful factors
If an opening is provided in the Sn layer to release hydrogen, then hydrogen occlusion is reduced, but moisture infiltration increases
Solution Approach 1:
Instead of creating large openings that would allow moisture ingress, the Sn layer is designed with a fine porous structure consisting of small voids and intermetallic compound regions. These microscopic pores are sufficient for hydrogen permeation but too small to allow significant moisture infiltration, thus resolving the contradiction between hydrogen release and moisture protection.
3Object-affected harmful factors
If the Sn layer is made dense to prevent moisture infiltration, then moisture resistance is improved, but hydrogen permeability deteriorates
Solution Approach 1:
The Sn layer is designed with a porous structure that appears dense at the macro level (preventing moisture infiltration) but contains microscopic voids and intermetallic compound regions (allowing hydrogen permeability). This multi-scale structure simultaneously achieves both moisture resistance and hydrogen release capability.
Solution Approach 2:
Different regions of the Sn layer have different properties: the overall structure provides moisture barrier function while local regions (voids and intermetallic compound areas) provide hydrogen permeability. This local quality differentiation allows the single layer to perform both contradictory functions.
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 intermetallic compound effectively reduces hydrogen occlusion in Ni-plated layers, preventing insulation resistance degradation and moisture ingress, while ensuring reliable electrical performance and mountability of the capacitors.
Implementation Method 1
the Sn-plated layer includes an intermetallic compound that penetrates through the Sn-plated layer in a thickness direction and allows hydrogen to pass therethrough more easily than Sn
Data Source
AI summary
A multilayer ceramic capacitor includes first and second external electrodes, each including a Ni-plated layer and a Sn-plated layer on the Ni-plated layer. The Sn-plated layer includes an intermetallic compound that penetrates the Sn-plated layer in a thickness direction, and allows hydrogen to pass therethrough more easily than Sn.