PCB proofing ceramic substrate production has those processes

There are many kinds of manufacturing process of ceramic products in circuit board factory. It is said that there are more than 30 kinds of manufacturing processes, such as dry pressing, grouting, extrusion, injection, casting and isostatic pressing. Because the electronic ceramic substrate is a "flat" type, the shape is not complicated, the manufacturing process of dry forming and processing is simple and the cost is low, so most of them use dry pressing forming method. The manufacturing process of dry press PCB electronic ceramics mainly includes blank forming, blank sintering and finishing, forming circuit on the substrate.

1. Green manufacturing of ceramic substrate (forming)

Use high purity alumina (content ≥95% Al2O3) powder (different particle sizes are required depending on the purpose and manufacturing method. For example, from a few illiterates to tens of microns) and additives (mainly adhesives, dispersants, etc.). Form a "paste" or processed material.

(1) Dry pressing of ceramic substrate to produce green parts (or "green").

Dry pressing billet is the use of high purity alumina (electronic ceramics with alumina content greater than 92%, most of the use of 99%) powder (dry pressing particles shall not exceed 60μm, for extrusion, rolling, injection and other powder particles should be controlled within 1μm) add the appropriate amount of plasticizer and binder, mixed evenly after dry pressing billet. At present, the offspring of square or round pieces can reach 0.50mm, or even ≤0.3mm (depending on plate size). Dry-pressed billets can be processed before sintering, such as the processing of contour dimensions and drilling holes, but pay attention to the compensation of dimensional shrinkage caused by sintering (the size of the amplification of shrinkage).

(2) Production of green billet by ceramic substrate spreading method.

Flow glue liquid (aluminum oxide powder + solvent + dispersant + adhesive + plasticizer mixed evenly + screening) manufacturing + flow casting (in the flow casting machine glue on metal or heat-resistant polyester belt) + drying + trimming (can also be other processing) + degreasing + sintering and other processes. It can realize automation and scale production.

2. Sintering and finishing of green billet after sintering. The raw parts of ceramic substrate often need to be "sintered" and finished after sintering.

(1) Sintering of raw ceramic substrate.

Ceramic billet "sintering" refers to the process of "sintering", the billet (volume) in the cavity, air, impurities and organic matter such as dry pressure removal, so that its volatilization, combustion, extrusion, and removal of alumina particles. Achieve close contact or combined growth process, so after sintering of ceramic green billet, there will be weight loss, size shrinkage, shape deformation, compressive strength increase and porosity reduction and other changes.

The sintering methods of ceramic billet are as follows: ① atmospheric sintering, non-pressure sintering will bring large deformation; (2) pressure (hot pressing) sintering, pressure sintering, can get good flat products is the most commonly used method; ③ Hot isostatic sintering is the use of high pressure hot gas sintering. Its characteristic products are finished at the same temperature and pressure. All kinds of performance balance, the cost is relatively high. In the added value of products, or aerospace, national defense and military products in the use of this sintering method, such as the military field of mirrors, nuclear fuel, barrel and other products. The sintering temperature of dry pressed alumina green billets is mostly between 1200℃ and 1600℃ (depending on composition and flux).

(2) Finishing of ceramic substrate after sintering (cooked) blank.

Most sintered ceramic billets require finishing. The purpose is: ① to obtain a flat surface. In the process of high temperature sintering of green billet, due to the imbalance of particle distribution, voids, impurities and organic matter in the green billet, it will cause deformation, unevenness or excessive roughness and difference. These defects can be solved by surface finishing;

② Obtain high finish surface, such as specular reflection, or improve lubricity (wear resistance).

Surface polishing treatment is to use polishing materials (such as silicon carbide, B4C) or diamond sand paste to gradually polish the surface from coarse to fine abrasive. Generally speaking, the use of AlO powder or diamond paste ≤1μm, or laser or ultrasonic processing to achieve.

(3) strong (steel) treatment.

After surface polishing, in order to improve the mechanical strength (such as bending strength, etc.), electronic ray vacuum coating, sputtering vacuum coating, chemical vapor evaporation and other methods can be used to plating a layer of silicon compound film, through 1200℃ ~ 1600℃ heat treatment, can significantly improve the mechanical strength of ceramic parts!

3. Form a conductive pattern (circuit) on the substrate

To process conductive graphics (circuits) on ceramic substrates, it is necessary to manufacture copper-coated ceramic substrates first, and then to manufacture ceramic printed circuit boards according to PCB technology.

(1) Forming a copper-covered ceramic substrate. There are currently two methods of forming copper-coated ceramic substrates.

① Laminating method. It is formed by hot pressing one side of oxidized copper foil and alumina ceramic substrate. That is, the ceramic surface is treated (such as laser, plasma, etc.), get activated or rough surface, and then according to the "copper foil + heat-resistant binder layer + ceramic + heat-resistant binder layer + copper foil" laminate together, after 1020℃ ~ 1060℃ sintering, the formation of double-sided copper coated ceramic laminate.

② Electroplating method. After plasma treatment, the ceramic substrate is "sputtered titanium film + sputtered nickel film + sputtered copper film", and then conventional electroplating copper to the required copper thickness, that is, the formation of double-sided copper-coated ceramic substrate.

(2) Single and double sided ceramic PCB board manufacturing. According to traditional PCB manufacturing techniques, single - and double-sided copper-coated ceramic substrates are used.

(3) ceramic multilayer plate manufacturing.

① In single and double panels repeatedly coated insulation layer (alumina), sintering, wiring, sintering to form PCB multilayer board, or the use of casting manufacturing technology to complete.

② Ceramic multilayer plate is manufactured by casting method. The raw tape is formed on the casting machine, then drilling, plugging (conductive glue, etc.), printing (conductive circuit, etc.), cutting, laminating, isostatic pressing to form ceramic multilayer plate.

Note: Casting molding method - casting liquid (aluminum oxide powder + solvent + dispersant + adhesive + plasticizer, etc. Mixed evenly + sifting) manufacturing + casting (the liquid evenly distributed on the casting machine coated on metal or heat-resistant polyester tape) + drying + dressing + degreasing + sintering and other processes.

In short, ceramic printed board belongs to the category of PCB, but also PCB board factory development and progress of the derivative and extension of the result. In the future, they may form one of the important types in PCB field. Because ceramic printed board has the best thermal insulation medium, high melting point and thermal dimensional stability, ceramic PCB in high temperature and high thermal conductivity application will have broad prospects for development!