Selection Principles and Solutions for Dispersants of Electronic-grade Nano Zirconia (3Y/8Y-YSZ, MLCC, Optical Films, Substrates, UV Optical Adhesives)
I、 Electronic grade exclusive hard screening criteria (different from ordinary industrial zirconia)
1. The raw materials for electronic ceramics (such as MLCC and high-frequency substrates) must reach ultra-high purity, and alkali/alkaline earth metal ions such as sodium, potassium, and calcium must be controlled below ppm or even ppb levels. These ions can cause damage to lattice integrity, insulation failure, skyrocketing ceramic dielectric loss, and substrate leakage short circuit due to their potential to cause damage; Therefore, the use of sodium hexametaphosphate and sodium polyacrylate is prohibited.
2. Thermal decomposition reaction can occur at lower temperatures (usually 120 ℃ -250 ℃), with ultra-low residual carbon and reduced sintering activation energy. The core quality indicators in the heat treatment process require complete decomposition and volatilization during high-temperature sintering/curing, leaving no carbonaceous residue, ensuring a dense and pore free film layer, stable electrical insulation performance, and high optical transparency.
3. Ultra fine nano adaptation: Due to the extremely small particle size (10-100nm) but high density, gravity settling and van der Waals agglomeration are extremely strong. Polymer dispersants must be used to firmly adsorb onto the particle surface through multiple chemical anchor points, and extend long and thick solvation chains to form a physical barrier (steric hindrance) to resist settling and agglomeration.
4. The material meets the requirements of environmentally friendly halogen-free, high-purity anti-corrosion (low ion precipitation), and can be adapted to three precision scenarios: MLCC ceramic dielectric sintering, optical anti reflective/high refractive coating, and semiconductor packaging conductive connection.
5. When the environmental pH (6.0-7.0) is neutral (close to the isoelectric point), due to the lack of electrostatic repulsion, van der Waals forces dominate, leading to hard particle aggregation; The system must be adjusted to an alkaline environment (pH 8.5-10.5, adjusted with ammonia/tetramethylammonium hydroxide, NaOH prohibited), where the particle surface carries a large amount of negative charge, generating strong electrostatic repulsion to maintain dispersion stability and prevent agglomeration.
II、 Complete selection of four major systems (water-based, alcohol ester oil-based, UV light curing, electronic inkjet)
（1） Waterborne electronic paste (tape casting MLCC, water-based gel casting, ceramic substrate)
1. Preferred: Sodium free ammonium polyacrylate (industry electronic ceramic standard)
Representative model: RK-4008Y high-purity ammonium salt dispersant
-Principle: A purification/preparation strategy is described for obtaining metal impurity free zirconia by utilizing carboxyl functionalized materials to adsorb zirconium species, preventing agglomeration through electrostatic repulsion under alkaline conditions, and introducing only completely volatile ammonium ions as equilibrium ions, followed by high-temperature calcination.
-Amount added: nano powder: 1.2%~3.0wt%, 3% for 10nm ultrafine powder
-Features: High solid content, low viscosity, easy to apply, can be mixed with PVA or acrylic systems, high-temperature sintering decomposition without residue, and production cost suitable for industrialization.
-Applicable: MLCC yttrium stabilized zirconia dielectric slurry, electronic ceramic casting, high-purity substrate blank
-Taboo: PEI polyethyleneimine (high residual carbon after degreasing, prohibited for high-end electronic insulation components)
2. Nano zirconia water dispersion system with high purity, low ion content, and good optical transparency
High purity food grade citric acid: With a heavy metal impurity content of less than 5ppm, it is suitable for the temporary dispersion process of weak acid systems in ultra-thin optical coating slurries. However, due to its characteristics, it is not suitable for long-term storage with high solid content.
3. Water based inkjet electronic ink (containing ethylene glycol/propylene glycol co solvent)
The problem of nozzle blockage caused by desorption and agglomeration of ordinary ammonium polyacrylate in high alcohol environments is addressed by using sodium free amphoteric polyurethane dispersants (RK-4040AE, RK-4057)
-It has good resistance to binary alcohol and low foam characteristics. After grinding, the particle size D50 is controlled below 120 nm, and it can be kept free of crystallization during long-term recycling use, and alkali metal ion pollution is strictly prohibited.
（2） A solvent based system for the preparation of multilayer ceramic capacitors (MLCC) and optical dispersions in low oxygen environments, mainly using propylene glycol methyl ether acetate (PGMEA), ethanol, and butanone (MEK) as composite solvents.
Core requirements: Good hydrophobic stability, able to effectively block moisture to prevent hydrolysis reactions; At the same time, it maintains ultra-high purity, no metal impurity pollution, and maintains uniform dispersion and no precipitation during long-term storage.
1. Benchmark: Metal free phosphate polymer dispersant
Representative: RK-4012, RK-4013, RK-4013A, RK-4013C (ion free electronic version)
-Stable binding is achieved through the strong coordination between phosphonic acid groups and zirconium hydroxyl groups, as well as the thick layer blocking effect formed by hydrophobic carbon chains. Additionally, due to the absence of alkali metal elements such as sodium and potassium, there are no residual inorganic salts after high-temperature decomposition.
-Addition amount: powder 1.8%~3.2%; Design of PGMEA electronic dispersion system and MLCC oil-based casting process.
2. Laboratory short-term grinding assistance: high-purity PVP (polyvinylpyrrolidone)
Only compound phosphate esters should be used, and should not be used alone as the main dispersant; Although there is no risk of ion contamination, it is prone to delamination and sedimentation during storage.
3. High performance zirconia composite powder with added alumina sintering aid
Ternary polymer dispersants have excellent broad-spectrum compatibility, can stably disperse various oxide powders, and ensure slurry uniformity by eliminating charge induced delamination, making them particularly suitable for co grinding processes of multi-layer electronic ceramics.
（3） An advanced electronic material system based on UV induced polymerization reaction for rapid prototyping and curing, covering ceramic slurries for DLP precision additive manufacturing, optical adhesives with high refractive index characteristics, and high-performance electronic component packaging resins.
Application: Precision molding of electronic ceramics, high refractive index optical films for mobile phones, UV filling materials for LED packaging
1. Industrial mainstream: RK-4035AB (electronic ceramic UV specific)
This material is a 100% active polymer system with high solid content and low viscosity characteristics ranging from 55% to 65%, and extremely low residual carbon rate; It does not interfere with the photo induced process in application and can be well adapted to YSZ nano zirconia.
Addition amount: Powder 2.5%~3.8%
RK-4039AC is a universal dispersant with excellent resistance to yellowing, suitable for water-based, oil-based, and UV curing systems.
Suitable for ultra-thin transparent optical UV coatings, with low color cast and no haze defects.
3. High end optical adhesive specific low acid value dispersant: RK-4061ED, RK-4054
Acid value ≤ 1mgKOH/g, to avoid side reactions with resin and ensure stable light transmittance and refractive index.
（4） Weak solvent electronic digital inkjet (PCB ceramic circuit, optical coating printing)
Oil soluble structured acrylic dispersant: RK-4035AC, RK-4039B
Has good solubility in ester and ketone solvents, no ion precipitation, and avoids corrosion of nozzle metal parts; But it is incompatible with water-based ammonium salts or polyurethane (PU) systems, and mixing will cause flocculation and lead to material scrap.
III、 Segmenting precise matching solutions based on electronic applications
1. A multi-layer ceramic capacitor using 3mol% yttria stabilized zirconia (3Y-YSZ) with extremely high purity as the dielectric.
Water based: ammonium polyacrylate; Oil based PGMEA: RK-4013A phosphate dispersant
2. High refractive index optical film/transparent coating nano zirconia
Waterborne inkjet: amphoteric polyurethane polymer; UV optical adhesive: RK-4061ED; Oil dispersion: RK-4011+PVP compound
3. Electronic ceramic DLP photopolymerization 3D printing precision devices
RK-4061ED (preferred)
4. Semiconductor packaging, insulation zirconia filling resin
RK-4013C oil-based phosphate dispersant to prevent the introduction of oxygen impurities into aqueous systems
5. Low cost laboratory samples and temporary slurry
Water based: high-purity citric acid; Oiliness: PVP assisted compounding
IV、 Key control of electronic grade processes (determining component yield)
1. Strict pH control (water-based)
Considering that the isoelectric point of zirconia is between pH 6-7 and its stable dispersion range is pH 8.5-10.5, ammonia water or tetramethylammonium hydroxide should be used to adjust the alkalinity of the system, and the use of sodium hydroxide is strictly prohibited to avoid contamination of the ceramic medium caused by the introduction of sodium ions.
2. Gradient test for dispersant addition (mandatory for electronics)
-Waterborne ammonium polyacrylate: 1.0%/2.0%/3.0% (powder mass)
-Oil/UV dispersant: 2%/3%/4%
Too low an addition amount can easily cause nano hard agglomeration and microcracks inside the substrate, while too high an addition amount can lead to an increase in residual carbon, an increase in dielectric loss, and a decrease in optical transmittance.
3. Stability acceptance criteria (mandatory in the electronics industry)
1. Laser particle size D90<120nm, uniform particle size distribution, no secondary agglomeration phenomenon (no bimodal);
After being stored at a constant temperature of 50 ℃ for 14 days, the sample did not show any hard precipitation, and the system was uniformly stable after shaking well;
3. According to ICP testing, the total impurity content of sodium, potassium, and calcium in the slurry is less than 10ppm;
4. UV/inkjet: After 48 hours of continuous cycle operation, the ink supply remains stable throughout the process, with zero corrosion of the nozzle and no crystal blockage.
V、 List of Prohibited Additives (Risk of Direct Scrap of Electronic Components)
1. Sodium polyacrylate and sodium hexametaphosphate dissociate to produce high concentrations of sodium ions, resulting in a significant increase in the conductivity of the medium and a complete loss of dielectric insulation properties;
2. Ordinary PEI cationic dispersants have a high residual carbon content at high temperatures, which can easily cause electrical leakage on insulating substrates;
3. Low molecular weight fatty acids and soap substances are prone to aggregation due to ion precipitation during storage, leading to flocculation and precipitation after long-term storage
4. Ordinary industrial grade sodium polycarboxylate dispersants are not suitable for the field of electronic ceramics.
