Multilayer Capacitor Electrode Structure for High-Temperature Bonding
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Solution Overview
Problem
Multilayer capacitors face reliability issues at high temperatures due to cracking problems with tin-based solder and reduced bonding strength when using conductive adhesives with tin-plated external electrodes, which affects their mounting and performance.
Innovation Solution
The design incorporates a multilayer capacitor structure with specific external electrode layers containing copper, silver, and palladium, and a connection region without internal electrodes, enhancing high-temperature reliability by using a conductive adhesive with silver filler for substrate mounting, which improves bonding strength and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tin-based solder is used for mounting, then bonding is achieved, but cracking occurs at high temperatures (150°C or higher)
Solution Approach 1:
The patent changes the material composition of the external electrode plating layer from conventional tin-based materials to a specific copper-containing composition (6-13 wt% Cu, 85-90 wt% Pd, 1-4 wt% Ag). This parameter change in material composition enables the external electrode to maintain bonding strength with conductive adhesive at high temperatures (150°C or higher) without the cracking issues that plague tin-based solder, thereby resolving the contradiction between reliability and strength.
Solution Approach 2:
The patent employs a composite plating layer structure consisting of multiple metal elements (Cu, Pd, Ag) in specific proportions. This composite material approach combines the advantages of each element: copper provides bonding affinity with conductive adhesive, palladium provides corrosion resistance and high-temperature stability, and silver enhances conductivity. The composite structure enables simultaneous achievement of strong bonding and high-temperature reliability.
2Ease of manufacture
If conductive adhesive is used as bonding material, then mounting is achieved, but bonding strength decreases when plating layer contains tin
Solution Approach 1:
The patent modifies the plating layer composition parameters by eliminating tin and introducing copper in specific amounts (6-13 wt%). This parameter change fundamentally alters the chemical interaction between the plating layer and conductive adhesive, transforming the bonding mechanism from weak (with tin) to strong (with copper), while maintaining ease of manufacture through standard conductive adhesive application processes.
3Reliability
If external electrode plating layer contains tin, then conductivity is achieved, but bonding strength with conductive adhesive is reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the plating layer by replacing tin with copper (6-13 wt%) while maintaining appropriate levels of palladium (85-90 wt%) and silver (1-4 wt%). This parameter change improves bonding strength with conductive adhesive because copper forms stronger chemical bonds with the adhesive matrix compared to tin, while the high palladium content maintains corrosion resistance and electrical conductivity.
Solution Approach 2:
The patent creates a multi-element composite plating layer (Cu-Pd-Ag system) that combines the beneficial properties of each element. Copper provides strong bonding with conductive adhesive, palladium provides corrosion resistance and maintains conductivity, and silver enhances electrical conductivity. This composite material approach resolves the contradiction by achieving simultaneous improvement in bonding strength and mounting reliability.
Data Source
AI summary
A multilayer capacitor includes a capacitor body in which a first capacitor portion and a second capacitor portion are disposed to face each other with a connection region disposed therebetween, the connection portion having a predetermined thickness in which an internal electrode is not formed. The first capacitor portion comprises first and second internal electrodes that are alternately disposed with a dielectric layer interposed therebetween, and the second capacitor portion comprises third and fourth internal electrodes that are alternately disposed with a dielectric layer interposed therebetween. First and second external electrodes connected to the internal electrodes respectively comprise first and second internal layers containing copper (Cu), and first and second external layers containing silver (Ag) or nickel (Ni), and palladium (Pd).