What is the production process of surface mount capacitors?

The production process of surface mount capacitors (MLCC, multi-layer ceramic surface mount capacitors) integrates precision materials science and micro nano manufacturing technology, and its process complexity is comparable to semiconductor chip manufacturing. The following analyzes the entire manufacturing process of MLCC from six major stages: raw material preparation, extrusion molding, printing and stacking, sintering, end treatment, and testing and sorting, combined with key technical parameters and equipment:
1、 Raw material preparation: laying the foundation for performance
1. Synthesis of ceramic powder
Material selection:
Barium titanate (BaTiO) based powder: Class I ceramic (C0G/NP0) core medium, requiring particle size<0.1 μ m and particle size distribution σ<0.02 μ m.
Zirconium/Titanate Composite Powder: The core medium of Class II ceramics (X7R/X5R) requires the addition of rare earth elements (such as Y ₂ O3) to regulate temperature characteristics.
Synthesis process:
Solid phase method: High temperature calcination (1000 ℃~1300 ℃), low cost but wide particle size distribution.
Liquid phase method (sol gel method): the particle size can be controlled to<0.05 μ m, but the cost is high.
Key equipment: ball mill, spray dryer, high-temperature kiln.
2. Preparation of electrode slurry
Material selection:
Nickel (Ni) slurry: The mainstream choice requires the addition of glass powder (<2 μ m) to enhance adhesion.
Copper (Cu) paste: has the best conductivity, but requires inert atmosphere protection to prevent oxidation.
Process control:
Viscosity: 100~300Pa · s (measured by a rotational viscometer).
Solid content: 60%~70% (affecting printing thickness).
Key equipment: Three roll grinding machine, vacuum defoamer.
2、 Casting Forming: Building Media Substrate
1. Casting process
technological process:
Ceramic slurry is uniformly coated onto PET substrate using a scraper, with a thickness controlled at<10 μ m.
Temperature gradient control in the drying zone (60 ℃ → 80 ℃ → 100 ℃) to avoid cracking.
Key parameters:
Casting speed: 0.5-2m/min (affecting the uniformity of the medium layer).
Drying time: 10-30 minutes (affecting residual solvent content<0.5%).
Key equipment: casting machine, online thickness monitoring instrument (laser interferometry).
2. Punching of dielectric sheet
Purpose: To provide positioning holes for electrode printing.
workmanship
Laser punching: accuracy<± 5 μ m, aperture<0.1mm.
Mechanical punching: Low cost, but accuracy<± 10 μ m.
Key equipment: laser marking machine, precision punching machine.
3、 Printing Stacks: Building Capacitive Structures
1. Screen printed electrodes
workmanship
Using 325 mesh stainless steel wire mesh, printing thickness<2 μ m.
Alignment accuracy<± 10 μ m (corrected by CCD vision system).
Key parameters:
Printing pressure: 0.2~0.5MPa (affecting electrode continuity).
Drying temperature: 150 ℃ (curing electrode slurry).
Key equipment: fully automatic screen printing machine, infrared drying furnace.
2. Laminated molding
workmanship
Stack the dielectric sheets of printed electrodes into hundreds of layers and control the pressure between 100-200MPa.
Temperature gradient control (60 ℃ → 100 ℃ → 150 ℃) promotes interlayer bonding.
Key parameters:
Laminated pressure: 150MPa (affecting interlayer bonding strength).
Pressure holding time: 30 minutes (to reduce interlayer bubbles).
Key equipment: isostatic press, vacuum hot press.
4、 Sintering: densification and performance solidification
1. Glue dispensing and pre firing
Purpose: To remove organic binders (such as PVB) and prevent sintering cracking.
workmanship
Heating rate<1 ℃/min, peak temperature 450 ℃ (nitrogen atmosphere).
The insulation time is 2 hours (to ensure complete decomposition of organic matter).
Key equipment: rubber extrusion furnace, atmosphere control box.
2. High temperature sintering
workmanship
Temperature control: 1200 ℃~1350 ℃ (Class I ceramics), 1100 ℃~1250 ℃ (Class II ceramics).
Atmosphere control: Reduce the atmosphere (H ₂/N ₂ mixture) to prevent electrode oxidation.
Key parameters:
Heating rate: 5 ℃/min (to avoid thermal stress cracking).
Insulation time: 2 hours (promotes grain growth and densification).
Key equipment: tunnel kiln, atmosphere furnace.
5、 End Processing: Connection and Protection
1. End coating
workmanship
Immersion method: Immerse MLCC into tin lead/pure tin/silver paste, with a thickness controlled between 5-20 μ m.
Electroplating method: current density 0.5~2A/dm ², thickness uniformity ± 1 μ m.
Key parameters:
Coating thickness: 10 μ m (balancing weldability and cost).
Combined strength:>5N (tensile test).
Key equipment: electroplating line, laser etching machine (end trimming).
2. End sintering
Purpose: To solidify the coating and enhance adhesion.
workmanship
Temperature control: 200 ℃~300 ℃ (tin lead coating), 150 ℃~200 ℃ (pure tin coating).
Insulation time: 30 minutes (to ensure crystallization of the coating).
Key equipment: reflow soldering furnace, infrared sintering furnace.
6、 Testing and Sorting: Quality Assurance
1. Electrical performance testing
Parameters:
Capacity (C): LCR meter test, accuracy ± 0.1%.
Loss tangent (tan δ):<0.1% (high-frequency type),<2% (power type).
Insulation resistance (IR):>10G Ω (high voltage type),>100M Ω (universal type).
Key equipment: automatic sorting machine, high-voltage tester.
2. Reliability testing
project
Temperature shock: -55 ℃~+125 ℃, 1000 cycles (IEC 60068-2-14).
Moisture resistance: 85 ℃/85% RH, 1000 hours (IEC 60068-2-78).
Mechanical stress resistance: bending test (radius<5mm), vibration test (10-500Hz).
Key equipment: environmental testing chamber, vibration table.
3. Appearance inspection
method:
Automatic Optical Inspection (AOI): resolution<5 μ m, detecting defects such as cracks and missing corners.
Manual re examination: Conduct secondary confirmation for suspected AOI points.
Key equipment: AOI detector, microscope.
7、 Packaging and Shipping: Terminal Protection
1. Tape packaging
workmanship
Insert MLCC into plastic carrier tape with a spacing of 2-4mm and heat seal tape.
Vacuum packaging: moisture-proof, anti-static, humidity<5% RH.
Key parameters:
Carrier width: 8mm/12mm/16mm (compatible with SMT machines).
Electrostatic protection:<100V (ESD test).
Key equipment: strapping machine, vacuum packaging machine.
2. Shipment inspection
project
Label verification: model, batch number, quantity.
Sampling test: Capacity, loss, appearance (according to MIL-STD-105E standard).
Key documents: COC (Certificate of Compliance), MSDS (Material Safety Data Sheet).
8、 Industry Trends and Technological Challenges
miniaturization:
The 008004 package (0.25mm × 0.125mm) has been mass-produced and needs to break through the limits of photolithography technology.
High capacity:
Commercialization of 100 μ F/6.3V (0402 package) relies on ultra-thin dielectric layer (<1 μ m) technology.
High frequency conversion:
The application of 5G is driving the development of C0G dielectric MLCC above 100GHz, and ceramic formulations need to be optimized.
Environmental Protection:
Lead free (pure tin coating) and halogen-free materials have become mainstream, and the problem of tin whisker growth needs to be solved.
Through the above production process, MLCC has achieved precision manufacturing from powder to device, and its technological iteration directly promotes the performance leap of electronic devices. In the future, with continuous breakthroughs in materials science and manufacturing processes, MLCC will play a more critical role in fields such as the Internet of Things, new energy vehicles, and aerospace.