CD Duplication
Plant Tour of How Compact Discs Are Made
by Cinram

Glass Prep and Mastering: The first part of mastering involves the preparation of a glass substrate. The glass substrate is a round disk of polished glass. After cleaning and polishing a liquid layer of material called photo resist is spin coated evenly onto the glass. The glass substrate with photo resist is then baked for about ½ hour. The glass substrate with the dried photo resist is called a glass master. The glass master is then to a laser beam recorder that is connected to a computer. The data image source is loaded into the computer. The data image is then read from the computer and recorded to the photo resist on the glass master using a laser. The data is recorded from the center of glass master in a spiral track that goes towards the outside of the glass master. After recording, the glass master is developed by spinning a Sodium Hydroxide solution over the glass master. Where ever the laser touched during recording the photresist washes away leaving a tiny pit of information. The developed glass master is then placed into a vacuum chamber and a small amount of silver is deposited (only molecules thick) onto the surface of the photo resist. The developed glass master coated with silver is called the metalized glass master. The metalized glass master is then sent onto Electroforming.

Electroforming: The metalized glass master is placed into a tank of Nickel Sulphamate solution for about two hours. During this time a layer of Nickel is grown onto the silver surface of the metalized glass master. When finished the metalized glass master is removed from the tank and the Nickel is separated from the Silver. This sheet of Nickel is called the father. The father is a reverse image of the data and could be used to stamp discs. However the father is not usually used to stamp discs since if it was damaged the whole process to create it would have to begin again. Therefore, the father put back into the electroforming tank for about two hours and another layer of Nickel is grown. The electroformed father is removed from the tank and the new layer of Nickel is removed from the father. This new layer is called the mother. The mother is then returned to the electroforming tank for about two hours and another layer of Nickel is grown. This layer of Nickel is removed from the mother and is called the stamper. The stamper is a reverse image of the data like the father and therefore can be used to create discs. Several stampers can be grown from a mother.

Stamper Finishing: The stamper is finished by punching out the center hole and outer edge and polishing its back side to be perfectly smooth. The stamper is now ready to be loaded into an injection molding machine to make disks.

Injection Molding: The stamper is placed into an injection molding machine. The injection molding machine is connected to a continuous supply of polycarbonate. Polycarbonate is heated to a molten state and shot into a mold that contains the stamper. The plastic is compressed against the mold under several tons of pressure. The plastic is then cooled using chilled water and the clear disc with the information stamped into it is removed. The whole process to stamp a disc takes between 5 and 10 seconds depending on the speed of the molding machine used.

After being stamped a thin layer of Aluminum is sputtered onto the side of the disc that contains the pits or information. This thin layer of Aluminum is the reflective surface that the playback laser reflects off of to read the information. This process of putting Aluminum onto the disc is called metalization. After metalization a thin layer of sealant or lacquer is spin coated onto the Aluminum. This sealant or lacquer is called protective coating. The protective coating is dried or cured using ultraviolet light. The disc is now sealed and ready to be printed. Most compact discs are screen printed with anywhere from 1 up to 5 different colors. Each separate color requires its own screen and it is printed one at a time. The screen allows ink to pass through in the shape of the desired image. Ink is pressed through the screen by a squeegee and cured using ultraviolet light. This process is repeated until all of the colors have been printed.

Some repicators (like DMI) offer offset printing on compact discs. Offset printing is usually only used if the customer requires ultra high quality printing and images. Offset printing is done with a metal plate and is a process type printing and images. Offset printing is done with a metal plate and is a process type printing. Process printing uses three primary colors and black produce to all known colors. Offset printing costs more than screen printing.

Packaging: After printing the discs are ready to be packaged. Several different types of packaging can be used for compact discs. One of the most common is the jewel box. Jewel box packaging can be done automatically where most other types of specialized packaging is done manually.

Quality Assurance: Throughout the above manufacturing process several different quality assurance tests are performed. The basic tests include a DVS test and a signal verification tests. The DVS test is a bit-for-bit comparison between the customer’s original image ready data and a replicated disc. This test insures that the replicated disc are identical to the original image. Signal verification tests insure that the discs playback parameters are within specification. Several other tests are performed during manufacturing to insure that replicated discs perform flawlessly.

Conclusion: As you may now conclude, the basic Compact Disc format developed by Philips and Sony allows for tremendous variation, thus creating opportunity to use this durable and versatile medium for innumerable formats and platforms. Whatever your Compact Disc application, there are format choices currently available and more are being developed. As the industry evolves, some formats will become dominant in the market while others may have only limited value.