MLCC Conductive Powders: Process Logic for Ni Inner and Cu Outer Electrodes
Time of issue:
2026-09-01
Analyzing practical manufacturing pain points of MLCC. Unpacking oxygen partial pressure control and shrinkage delay in Base Metal Electrode Nickel co-firing, and how bimodal Copper powders increase tap density to block plating bath ingress.
No matter how flawless a conductive powder looks on a datasheet, it reveals its true nature only inside a 1200°C co-firing furnace or a highly acidic plating bath. The technical barrier to MLCC miniaturization is fundamentally a battle of nanoscale thermodynamics and morphology. Setting aside theory, we directly address the practical pain points and powder-level solutions for BME Nickel and Copper termination electrodes.
Nickel (Ni): The PO2 and Shrinkage Mismatch in BME Co-firing
🔹The Pain Point:
When co-firing Barium Titanate dielectric with Nickel paste above 1200°C, a pure reducing atmosphere protects the Nickel but reduces the ceramic, turning it into a semiconductor and causing insulation failure. Worse, standard nano-Nickel powder begins shrinking aggressively at ~400°C, while the ceramic only densifies above 900°C. This shrinkage mismatch triggers internal delamination and micro-cracking.
🔹The Powder Solution:
- Wet Hydrogen Compatibility: Production lines must use a wet hydrogen mixture (N2/H2/H2O) to precisely pin the oxygen partial pressure (PO2). This requires the Ni powder to possess exceptional surface stability and oxidation resistance.
- High Crystallinity & Passivation: During synthesis, we engineer high crystallinity and a nanometer-thick dense oxide passivation layer. This intentionally suppresses the powder's low-temperature sintering activity, delaying severe shrinkage to higher temperatures. This aligns closely with the ceramic’s thermal expansion curve, providing a generous process buffer for co-firing.
Copper (Cu): Termination Densification vs. Acid Seepage
🔹The Pain Point:
After the Copper termination is applied and fired, it undergoes acidic Ni/Sn electroplating for SMT readiness. If the fired Copper layer has high porosity, capillary action will draw the acidic bath into the MLCC, corroding the inner electrodes. Mono-dispersed Copper powder has a physical ceiling for tap density, making high densification difficult.
🔹The Powder Solution:
Implementing a bimodal or trimodal distribution of spherical Copper powder. By utilizing sub-micron particles to precisely fill the interstitial gaps between micron-sized particles, the tap density is significantly elevated. This directly reduces the required organic vehicle volume in the paste, enabling the formation of a highly dense, low-porosity conductive network at standard firing temperatures, effectively blocking acid seepage pathways.
Exceptional conductive metal powders do not chase theoretical extremes on a single metric; they provide a crucial buffer, a wide process tolerance, for formulators and engineers navigating harsh thermal and chemical environments.
Keyword:
MLCC Nickel Powder,Cu Termination Paste,Oxygen Partial Pressure,Tap Density,Ni Shrinkage Rate
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