Application of High Precision Thick Film Screen Printing Process in Surface Metallization of Ceramic Media Filter

Ceramic dielectric filter is a filter based on ceramic material. As an important part of radio frequency devices in mobile communication, it is responsible for filtering the transmitted and received signals, that is, it can selectively transmit or block signals within a specific frequency range, so as to ensure the accuracy of sending and receiving signals. With the advent of 5G era, ceramic dielectric filter has gradually become the mainstream application because it can meet the development trend of miniaturization and low cost. But its process is not yet fully mature, today we will understand the key link of the ceramic dielectric filter: ceramic metallization process.

1. Production process of ceramic medium filter

   The production process of ceramic medium filter mainly includes powder manufacturing, pressing molding, sintering, grinding, metallization, assembly and debugging, etc., among which the metallization process accounts for 35% of the whole process, which is the key link in the production of ceramic medium filter.

2. Metalallization process of ceramic medium filter

   Ceramic metallization is to make the ceramic insulating material have conductive performance, by coating silver paste on the back of the ceramic substrate, the piezoelectric effect after DC high voltage polarization, so as to conduct electromagnetic wave shielding. The better the electrical conductivity, the better the shielding effect, and the smaller the insertion loss. Therefore, in order to ensure the conductivity, silver paste coating plays a key role in the filter production, directly affects the quality and performance of products, and determines whether the product yield can be guaranteed and achieve mass production. At present, the commonly used metallization process includes silver spray printing, thick film screen printing, etc.

   
   

   (1)Spray silver

   Silver spraying is to spray the ceramic matrix through silver spraying equipment, dry and then continue to spray, and sintering after repeated spraying. After spraying silver, the silver layer surface binding force is very good, but the waste of silver pulp is serious. And need many times spraying drying, complex, labor cost consumption, resulting in the increase of enterprise costs at the same time, but also can not improve the efficiency of mass production.

   (2)Thick film screen printing

   Thick film screen printing is to print the surface of the ceramic matrix by high precision thick film screen printing machine, and complete the metallization after high temperature sintering. Its simple operation, high printing efficiency, uniform coating film thickness, can achieve mass production. The process flow is as follows:

   a.  High-precision, thick-film silk-screen printing press

   Select the precision thick film screen printing machine with high printing accuracy, high film thickness consistency, high printing efficiency, high degree of automation and high easy to operate to ensure the stability and accuracy in the printing process.

   b.  Prepare ceramic matrix

   Ensure that the ceramic matrix surface is smooth and clean.

   c. Prepare the screen plate

   According to the product requirements, select the appropriate mesh number and film thickness, the particle size of the mesh match, good compatibility with the ceramic substrate, strong adhesion, to avoid blocking the mesh and other quality problems.

   d. Prepare the slurry

   Select the silver paste with moderate consistency, uniform particles and stable performance to ensure that no blocking plate and drawing problems occur in the printing process. In addition, the viscosity and other physical parameters of silver pulp should be adjusted and optimized according to the actual production situation.

   e. screen print

   The screen plate is installed on the high precision thick film screen printing machine, and then the silver pulp is poured into the net plate. Under the action of the scraper, the silver pulp is deposited on the ceramic matrix through the upper hole of the web plate to complete the printing.

   f. dry

   After the printing is complete, the ceramic substrate needs to be dried to remove the solvent from the ink. Usually use drying equipment drying or natural air drying method, drying time in 20-30 minutes.

   g. firing

   The sintering temperature of silver paste is generally between 750℃ -850℃, and the sintering time also varies according to the different processes. During the sintering process, the temperature and time stability should be maintained to ensure that the silver slurry is fully cured and obtains good conductive performance.

In general, in the metallization process of ceramic medium filter, although the silver layer adhesion is very good, its many processes and the waste of silver pulp seriously limit its application in mass production. Relatively speaking, the thick film screen printing process has the advantages of simple operation, uniform coating film thickness, and the matching automatic production line can quickly achieve mass production, the perfect process also provides a reliable solution for the metallization of ceramic medium filter. In the future, with the continuous progress of technology and the growing demand, this process is expected to continue to play an important role in the filter industry, and help promote the development of mobile communication and other fields.