The Replication Process Explained
The process of manufacturing CD, DVD and Blu-ray discs in mass quantities is called replication. Replication is used for producing large quantities of discs ranging from one thousand to one million copies. These thousands of identical copies are produced from a single original known as a "glass master" disc.
The primary factor in quality replication is to keep the conditions surrounding the production of the glass master immaculate and sterile through the use of a clean-room. If any particles or pollutants are in the air, it compromises the quality and integrity of every replicated disc.
The glass master is a substrate that is made larger than a CD, DVD or Blu-ray with an approximate 24 centimeter diameter and a 6 millimeter thickness. Throughout the replication process, this substrate simply acts as a medium to carry the layers of metal and bonding agents that make the creation of data and subsequent copies possible.
Once prepped with a cleaning solution and solvent, the glass master is bathed with a UV-sensitive, photo resist coating. Once this coating has been applied, it is baked for a brief interval of time. The photo resist layer allows the glass master to carry the source data written by a laser.
The Laser Beam Recorder (LBR) is intrinsic equipment to the replication process that's controlled by a formatter that translates source data to be used by the laser beam. With high-powered gas, the blue, violet or UV beam (depending on the type of disc being created) etches the data pits into the photo resist layer. The photo resistor is developed through a chemical process on the glass master. Once development is complete, the master with the data pits is layered with a nickel or metal alloy.
The next step in the replication process is the electroforming of the glass master. Electroforming is responsible for setting the multiple copies of discs into motion; these replicas are referred to as fathers, mothers and sons (or stampers). Electroforming uses a nickel bath to layer metal on the master's pitted data surface. The master remains in the solution until enough metal has accumulated on the surface that it can be peeled off in one piece from the substrate. The result is a negative master, or father.
Electroforming is repeated, this time with the father in the nickel solution. The pitted metal layer now has a positive data impression, producing the mother, which is also plated with metal through electroforming. With the mother electroplated into one to two dozen metal impressions, sons are created. Sons share the exact negative impression of the father.
Now the father becomes a stamper mold along with the sons. The mother is the only metal impression needed to create more stampers (sons). The electroforming of the mother is carried out to the desired disc volume.
The stampers are checked, shaped and center hole-punched to the adherence of disc standards. Next, they are injected with liquid polycarbonate and cooled. An automated robotic arm with vacuum-like grip technology picks up and transfers the partly finished disc to the equipment's chamber that applies alloyed metallic layers to the data side of the disc. Since this layer rests closely to the data pits, a protective UV coating is applied to shield the layer from the elements.
CD, DVD and Blu-ray replication will differ, as their general composition will show discrepancies. The laser beam will have a smaller diameter in creating data pits for DVDs when compared with CDs, and the laser is even thinner for Blu-ray. DVDs have two polycarbonate substrates bonded together with heat in comparison to one for CDs.
For Blu-ray, using additional mastering server drives or a separate LBR may be required. Configurations of how the stampers are shaped will vary to compensate for the format being manufactured. Content authoring and encryption processes will also differ among types of discs.
You can also watch the following video for a detailed explanation of the replication process.