The whole process of DPC ceramic board and the introduction of required equipment

List of main process flow and production equipment of DPC ceramic substrate

DPC ceramic substrate has the characteristics of high line accuracy, high surface flatness, high insulation and high thermal conductivity, and has rapidly occupied an important market position in the field of semiconductor power device packaging, and is widely used in high-power LED, semiconductor laser, VCSEL and other fields.

Direct Plating Copper (DPC) is a ceramic circuit processing technology developed on the basis of ceramic thin film processing. The process first uses vacuum coating to sputter on the ceramic substrate and combines it with the copper-metal composite layer, then uses the photoresist of yellow light lithography to be re-exposed, developed, etched and film-removed to complete the circuit fabrication, and finally uses electroplating/chemical plating to increase the thickness of the circuit, and completes the metallization circuit fabrication after the photoresist is removed.

DPC ceramic substrates are small in size, precise in structure, high in reliability, complex in process and fine in production process, which are technology-intensive industries and have high technical barriers. Its production process mainly involves punching, magnetron sputtering, chemical copper deposition, copper plating, solder resist printing, chemical silver/chemical gold deposition and other major processes.

The main production equipment of DPC process includes: laser punching machine, drying equipment, laser coding machine, magnetron sputtering equipment, cleaning equipment, electroplating equipment, grinder, etching machine, annealing machine, belt sanding machine, plate grinding machine, high-speed flying needle testing machine, sand blasting machine, screen printing machine, plate grinding machine, laminating machine, exposure machine, developing machine, annealing furnace, laser scribing machine, thickness gauge, AOI automatic optical vacuum testing machine, scanning microscope, ultrasonic, etc.Among them, Shenzhen feishida mechanical equipment co., ltd. provides cleaning equipment, electroplating equipment, grinding machine, sandblasting machine, developing machine, etching machine, polishing machine, copper reduction machine and abrasive belt machine..

　　1. Laser drilling

Before laser drilling, a layer of water-soluble food-grade substrate pigment is first applied to the ceramic substrate by a brush to reduce the reflectivity of the laser on the substrate and enhance the laser drilling effect. Put it in a drying box for drying, and then use a laser drilling machine to open up the upper and lower substrates as a path connecting the upper and lower substrates.

• Laser drilling machine drilling for different ceramic materials will use infrared, green, ultraviolet, CO2 and other different wave band laser beam irradiation material surface, each laser pulse has a part of the material is burned off.

　　2. Laser coding

Laser coding is to use a laser coding machine to engrave the product two-dimensional code onto the substrate.

　　3. Ultrasonic cleaning

Cleaning removes the red glue attached to the substrate after laser drilling and laser coding and the trace particles generated by coding to ensure the cleanliness of the surface of the substrate. The burrs generated by drilling are removed by coarse scraping, bubbling and fine scraping, and the particles attached to the surface of the substrate are washed with water after scraping. The substrate after slag removal needs to be micro-etched to roughen the surface, improve the effect of magnetron sputtering in the later process, and then dry to remove the moisture on the surface of the substrate.

　　4. Magnetron sputtering

The basic principle of magnetron sputtering is to inject a little argon gas into a high vacuum closed high voltage electric field container to ionize the argon gas and generate argon ion flow, bombard the target cathode in the container, the target material atoms are squeezed out one by one, and the molecular precipitation accumulates and adheres to the ceramic substrate to form a thin film.

Figure Magnetron Sputtering Principle

In order to achieve good results before sputtering, it must be pretreated by dust removal, oil removal, slow pulling, etc.

　　5. Chemical copper sinking

The main purpose of chemical copper deposition is to thicken the copper layer, increase the conductivity of the through hole, and at the same time ensure a better connection with the sputtered copper layer. Chemical copper deposition is a catalytic oxidation-reduction reaction, because the mechanical properties of chemical copper deposition copper layer is poor, easy to produce fracture when subjected to impact, so chemical copper deposition should adopt thin copper plating process.

Chemical copper deposition must go through pre-treatment processes including degreasing, micro-etching, pre-immersion, activation, and promotion.

　　6. Full plate electroplating

Full plate plating, that is, pre-plating copper mainly increases the thickness of the copper layer, mainly including degreasing, micro-etching, pickling, copper plating, de-plating (hanging) process. Copper plating uses copper balls as anodes, CuSO4 and H2SO4 as electrolytes, and the main chemical reactions of copper plating are represented by the following cathode chemical reactions: Cu2 2e- → Cu. After the pre-copper plating is completed, the excess copper layer on the fixture needs to be stripped.

　　7. Grinding plate-film pressing-exposure-development

After the full plate electroplating copper layer, it is necessary to engrave the circuit on the copper surface of the substrate to prepare for the next process to thicken the copper layer of the circuit. The process mainly includes pickling, plate grinding, film pressing, exposure, development and other processes.

1) Pickling: The surface of the substrate is cleaned with a 3-5% sulfuric acid solution to remove the oxide film that may exist on the surface of the substrate.

2) Grinding plate: use the grinding wheel of the grinding plate machine to roughening the surface of the substrate, and at the same time clean and brighten the surface of the substrate to remove the fingerprints, grease, etc. attached to the surface of the substrate;

3) Pressing film: the photosensitive liquid is coated on the polyester substrate in advance, dried to make a photosensitive layer, and then covered with a layer of polyethylene film. This photosensitive resist material with a three-layer structure is called dry film resist, referred to as dry film;

4) Exposure: The film is placed on the dry film pressed on the substrate, and the exposure machine generates ultraviolet light by using the imaging principle of the negative film, so that the film on the chromium plate is polymerized to generate an insoluble weak alkali resist film layer. The unnecessary part is covered by the film with the recorded pattern, and no photopolymerization reaction occurs.

5) Development: the active group of the unexposed part reacts with the alkaline solution to generate a soluble substance and dissolves, leaving the part that has been photosensitive cross-linked and cured.

　　8. Graphic plating (copper plating)

After exposure and development, the lines that need to thicken the copper layer appear, and the copper plating process is used to thicken the copper layer of the lines.

　　9, etching to bottom

Remove the excess copper layer and dry film on the line, and etch and remove the copper layer and titanium layer attached to the surface of the substrate in the previous process magnetron sputtering, chemical copper deposition, pre-electroplating copper and other sections outside the line, which mainly include rough grinding, stripping film, copper etching, titanium etching and other main sections.

　　10. Annealing

The annealing furnace is used to bake the ceramic plate at high temperature to release the concentrated stress during electroplating, increase the ductility and toughness of the copper layer, and make the copper particles more compact.

　　11. Abrasive belt grinding

After annealing, a layer of oxide is attached to the surface of the substrate, and the surface is relatively rough, in order to prevent the subsequent gold silver product quality is not up to standard, need to be polished to remove. After polishing, the surface becomes smooth and flat.

　　12. Flying Needle

A high-speed flying needle tester is used to test the through-hole short circuit.

　　13. Sand blasting before welding resistance

Before welding resistance, it is necessary to carry out sandblasting pretreatment on the substrate circuit to roughen, clean the surface, remove the surface oxide and dirt, etc. The specific processes include pickling, sandblasting, micro-etching and other major treatment sections.

　　14. Solder resist printing

The purpose of solder resist printing is to cover the permanent interlayer material on the part of the conductor that does not need to be soldered on the surface of the circuit board, which is called solder mask. When it is assembled and welded downstream, its surface treatment or welding is limited to the designated area, which protects the board surface from contamination during the subsequent surface or welding and cleaning process, and protects the circuit from oxidation and welding short circuit.

After the solder resist ink is coated on the board surface by screen printing, it is sent to an ultraviolet exposure machine for exposure. The ink generates a polymerization reaction after the light-transmitting area of the negative is irradiated by ultraviolet rays, and the non-illuminated area on the coating film is developed and removed by sodium carbonate aqueous solution.

　　15. Sandblasting after assembly and welding

After the substrate is printed by solder resist, exposed and developed, the part to be welded is exposed. In order to achieve good effect by surface modification of gold/silver in the next process, the exposed part needs to be sandblasted to roughen the surface and remove the oxide attached to the copper surface.

　　16. Surface treatment

After the solder resist is completed, the position of the circuit board pad is plated with different metals such as gold and silver by electroplating or electroless plating to ensure that the exposed terminal part has good solderability and oxidation resistance.

　　17, Laser cutting

Laser cutting equipment is used to cut the product.

　　18. Testing

The use of thickness gauge, AOI automatic optical inspection machine, ultrasonic scanning microscope and other testing equipment to detect the performance of the product appearance.

　　19. Marking

The product identification code is printed onto the ceramic substrate using a marking machine.

　　20. Packaging and Shipping

The use of vacuum packaging machine will be shipped after packaging products.