Beginner-friendly! Basics of temperature measurement in MLCC manufacturing process and key points for reducing defects, Part 2

Raw material blending and sheet molding stage

• Raw material blending

  When preparing a slurry by mixing ceramic powder, binder, solvent, etc., the temperature during mixing can affect viscosity and dispersibility. Preparing a uniform slurry at the appropriate temperature directly impacts the quality of the resulting sheet.

• Green sheet formation

  When forming a green sheet by applying a slurry in a thin film and drying it, the drying temperature and time affect the uniformity and density of the sheet. Improper drying can cause cracking and uneven density in the sheet.

Lamination and pre-sintering stage

• Lamination and crimping

  In process stacking and pressing multiple layers of green sheets together, temperature control is crucial for softening the binder. There are also devices that achieve high accuracy processing by heating water according to the type of binder and applying uniform pressure.

• Binder removal (pre-sintering)

  In the pre-sintering process, which is performed to remove organic binders after lamination and compression, controlling the heating rate and the maximum temperature reached is extremely important. Rapid heating accelerates the thermal decomposition of the binder, causing sheet swelling and cracking due to gas generation. By removing organic matter slowly at low temperatures, these defects can be prevented, and the occurrence of structure defects such as delamination during firing can be significantly reduced. Heat treatment equipment compatible with superheated water vapor is said to contribute to shortening the de-bindering time and enabling low-temperature processing.

Electrode formation and firing stage

• Electrode burning

  After applying the external electrodes, proper temperature control is also necessary during the baking process. Precise temperature control is required to ensure proper adhesion and conductivity of the electrode material.

• Firing

  Of all process involved in MLCC manufacturing, the firing process is the one that requires the most precise temperature control. By firing the ceramic at high temperatures ranging from several hundred to over a thousand degrees Celsius, the dielectric and internal electrodes are integrated.

  • Heating rate

    Rapid temperature increases can cause cracks due to thermal stress. Especially in high-end MLCCs where thinning is progressing, high-speed heating furnaces with rates of 100°C/second or more have been development to increase the coverage of the internal electrodes.

  • Maximum firing temperature and holding time

    The degree of sintering, grain size, and dielectric characteristic of ceramic materials depend heavily on these conditions. Inappropriate temperatures can lead to variations in dielectric constant, insulation failure, or a decrease in mechanical strength.

  • Atmosphere control

    The atmosphere inside the furnace, including oxygen partial pressure, hydrogen concentration, and dew point, also affects the oxidation-reduction state of the electrode material and characteristic of the ceramic. high accuracy control of these factors leads to the production of high-quality, high-yield MLCCs.

Terminal attachment and inspection process

• Terminal attachment

  When soldering lead wires to a completed chip, improper soldering temperature can lead to solder cracks or cracks in the chip due to thermal shock.

• Inspection

  When evaluating the electrical characteristic and reliability of the final product, temperature cycling tests using a constant temperature chamber and high-temperature load tests are performed. This is essential to guarantee the performance of MLCCs under the actual operating environment.

Thus, temperature measurement plays a crucial role in maintaining quality and reducing defects at each process of MLCC manufacturing.