HOW CD-ROM Discs are Made?
CD-ROM is becoming one of the most important tools of the new Millennium. As the compact disc format for computers grows in, an increasing number of software publishers have found themselves venturing into the brave new world of CD-ROM, taking advantage of its fantastic capacity and options for information delivery.
The world of CD-ROM manufacturing is highly technical and complex, but like other elements of software production, such as printing and packaging, it is a step-by-step process.
The first step in CD-ROM manufacturing, is receipt of the client's software application. MediaAnnex can accept your project as either raw computer files or pre-formatted CD image files on input media ranging from CD-Recordable and Sony HiFD disks. CD-Recordables or "CD-Rs" have become a popular source media because of their ability to provide publishers with a working CD prototype before going to large-scale replication. Supplying a CD-R also means that data is "CD ready" for manufacturing, thus eliminating the need for further formatting.
Premastering top
If raw computer files (those not yet formatted for CD) are submitted, information must go through a pre-production step called premastering.
This process involves converting files into a standardized, logical format required for compact disc manufacturing. This standardization ensures universal readability of any CD-ROM disc, created for a given platform, by all CD-ROM drives. ISO 9660 is the international standard for the CD-ROM logical format in that it can be universally read and interpreted on Mac, PC, UNIX and VAX platforms. Apple HFS (Hierarchial File System) formatting is specifically designed to support the custom features of the Macintosh operating environment on compact disc. Other CD data formats available to you the client are CD-I (Compact Disc Interactive), CD-XA (Compact Disc Extended Architecture -- a mixed mode format where data and audio files are interleaved) and hybrid formatting which allows multiple file systems (such as ISO and HFS) to be placed on a single, shared CD-ROM.
During premastering, a bit for bit verification is usually also performed to insure error-free conversion. Once the logically formatted data is approved, manufacturing can begin. Disc manufacturing involves five steps including mastering, electroforming, replication, printing and packaging.
Mastering top
Since the quality of any CD-ROM disc is only as good as the master used to create it, mastering is considered the most critical step in the manufacturing process. CD pits, created in the mastering process, are among the smallest of all manufactured formations -- each is about the size of a particle of smoke. Which means that even the most microscopic forms of contamination can obscure large amounts of data. A clean room environment, where the size and number of particles in the air are strictly controlled, is therefore, a key requirement in both mastering and manufacturing CD-ROMs.
Although there are several methods currently available for CD mastering, a photoresist system is most commonly used. This method produces a glass master by applying a photoresist (a light sensitive chemical that acts similarly to emulsions used to print black and white photos) to a specially prepared glass substrate.
The photoresist is generally applied in a spin coating process in a thickness equal to approximately 1/8th of a micron; 640 times thinner than a human hair.
Data is recorded in the photoresist layer through a laser encoding process where a computer translates the formatted input media into a series of "on" and "off" pulses of a laser beam recorder.
In a spiral track, the laser beam recorder exposes portions of the photoresist with a blue light, creating the disc contents. If stretched linearly, this spiral track can run as long as three miles from the inner hub to the outer edge of the disc. Much like a photographic process, the glass master is then developed by applying a chemical developing fluid. The exposed areas of the photoresist are etched away resulting in the formation of millions of microscopic pits in the resist surface. After developing, a metal coating, usually silver, is evaporated onto the photoresist surface to provide a conductive surface for electroforming the glass master.
Electroforming top
The ultimate goal of electroforming is to generate metal stampers used to replicate CDs.
In this stage of production the glass master, which is now electrically conductive with its silvered surface, is submerged into a chemical bath containing nickel ions. By running current through an electrical circuit, nickel ions are attracted to the exposed surface of the glass master containing the disc image. As this coating of nickel grows, it conforms to the contours of the pits and lands (the space between pits) etched in the exposed photoresist surface.
The end result is the formation of a thick, durable piece of nickel plating containing a negative impression of the compact disc in its metallic surface.
This initial piece of metalwork is known as a metal master or "father". It is called a father because it is used to generate a family of two additional pieces of metalwork called a mother and a stamper. Mothers and stampers are successively grown in additional electroforming processes; mothers from fathers and stampers from mothers -- each piece an opposite image of the other. The stamper, an exact replicate of the metal master, is the end product of this stage of production and the "metal template" from which plastic CD replicates will be mass produced.
CD Replication top
The first step in replication is to transfer the image of the compact disc from the metal stamper to a plastic substrate.
A high-precision injection molding press injects a molten resin made of optical grade plastic into a mold cavity, containing the stamper on one of its faces. This process, which takes onl a few seconds, results in the formation of a clear plastic disc with the pits impressed on one side. The plastic substrate is then metalized by applying a very thin layer of pure aluminum over the data pits molded into its surface. This metalization process provides reflective surface required for disc playback and gives the CD its distinctive, mirror-like appearance. A typical method of metalizing is through a sputtering process where discs are individually bombarded with aluminum atoms providing a uniform coverage.
A final step in manufacturing is the application of durable lacquer coating on top of the aluminized surface. This coating protects the aluminum from scratches, oxidation and provides a platform for label art printing.
Printing and packaging top
Graphic images are applied to the lacquered disc surface via high speed silk. Silkscreen printing, our most commonly used method, involves transferring artwork to a porous screen through which inks are applied in a process similar to stenciling.
After printing, discs are either automatically or manually packaged. Although there has been growing availability and use of alternative options, the plastic jewel case remains the mostcommonly used packaging choice for CD-ROM.
This trend has emerged due to its durability and universal availability of automated assembly.
Other popular packaging options, which may require manual assembly depending upon the option and replicator, include lightweight alternatives such as paper window and cardboard sleeves, transparent plastic sleeves such as Viewpaks, and environmentally-friendly cardboard versions of jewel cases like DIGIPAKs, and Others (see our "Packaging" pages).
Quality Control top
Disc quality is strictly controlled at every step of production to assure conformity to industry specifications. This ensures that all disc tolerances, which are acceptable ranges of variance, are within the design limits of all CD-ROM drives.
Although all CD-ROM disc manufacturers are governed by the universal quality standards set forth by Sony and Philips in the Yellow Book specifications (the standards document for ROM), each manufacturer typically has their own quality control philosophy.
The best replicators have internal standards which go beyond industry requirements. In mastering and replication critical parameters include signal quality measured by Block Error Rates -- commonly known as BLERs, adherence to electronic standards, material stress and other physical defects that can affect disc playability.
Turnaround time top
Turnaround time, also known as turn time, is the time it takes for our replication facility to complete all the stages of CD-ROM production mentioned above. The faster the turnaround required for finished product, the more expensive the service.
Rush jobs, such as one- and 4 or 5 day turns, are available but at significantly higher costs than standard 10-day to 12-day turns (for standard CD-ROM). Turn time can be a confusing issue for the client, because CD-ROM replicators often vary in their definition.
Some quote strictly on a business day basis, while others quote based on calendar days. Some consider the day data arrives at the plant day zero and do not apply it to days quoted in a turn, and others consider it day one.
The best strategy for you, the client obtaining quotations based on a given turn time, is to clarify each replicator's definition to ensure an apples to apples comparison. It is also important to note that CD-ROM production is a scheduled, multi-faceted manufacturing process which involves more than just pressing discs. A quoted turn time is a promised date based on the assumption that all required parts including data, disc artwork and packaging materials are "workable" and at the factory at the necessary time. Any delay in receipt of workable parts, such as print which arrives late or label art which is out of the manufacturer's specification, will usually add critical days to turnaround time.
While some manufacturers will go to great lengths to meet delivery deadlines under less than perfect conditions, their ability to do so depends upon several critical factors such as the nature of the delay, operating capacity and their own in-house capabilities.
We pride ourselves on our quick, effective turnaround times.
As the CD-ROM software industry grows, so does the demand for superior disc replicators.
Although disc manufacturing is a standardized process, the quality of your total CD-ROM production experience, including flexible scheduling, technical expertise and one-stop-shopping to name a few, can vary greatly from company to company.
Finding the right long term partner to meet your requirements is a task which involves research beyond basic price comparisons.
We believe that we are that partner.
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