ARTICLES: HOW CD's ARE MADE

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INTRODUCTION

The compact Disc originally was a joint effort of the Sony Corporation and Phillips Electronics, introduced to the market in 1982. The utilization of digital technology meant a vast improvement on sound quality in that, unlike the vinyl record or analogue tape, nothing came in contact with the playing surface on playback. Therefore there is no physical deterioration. A laser beam reads information on the disc surface eliminating background noise common to the other configurations.

Most people have listened to a Compact Disc in their CD player but how many really know what is involved in bringing music to your home?
   
This article will give you a better understanding of what is involved in the CD manufacturing process. Replicated or plant manufactured CDs are better than burned CDs. It is more compatible to most players available and is said to have a longer life.

The recording of an album is usually done in a professional studio. Once equalized a digital source is created, which is used to begin the disc making process.

The making of a "stamper" is a procedure that begins with a process called Glass Mastering.

GLASS MASTERING

The making of glass master, is a highly technical process where the digital information from the source is transferred in "PIT" form onto a polished glass that is covered with a photo resist coating. The term "PIT" refers to a series of microscopic imprints that are formed on the photosensitive layer that coats that glass. As the beam comes in contact with the coated glass, it translates the digital information to the coating on the glass, in the form of pits.

STAMPER

Although the glass master is used once, its by-product is called the "father". In order to make the father it is necessary to make the glass master conductive. The master is coated with a thin layer of nickel using electroforming, AKA matrixing. A glass master is immersed in a nickel electrolyte bath. While in the bath, a controlled low charge is put through the conductive coat on the glass master. This causes the nickel in the bath solution to be extracted and adhere to the conductive coat on the glass master. As the thickness of the nickel increases, so does the electric charge to a maximum of about 100 amps. This process of electroforming takes approximately two hours. Once complete and the nickel is at the desired thickness, it is separated from the photo resist coat on the glass master. The separated portion is the "father", and is cleaned up in an electrolytic high temperature tank to remove any of the photo resist that might remain. The father holds a negative imprint on the glass. The father could be used directly in replication, however, most times, a positive imprint called a "mother" is made. From the mother, four to five negative imprinted "stampers" can be made and delivered to our plant so manufacturing can begin.

REPLICATION

Replication refers to the actual making of the disc utilizing injection molding machines and a metallization process. The machinery is described as a dual line because on each line, there are two injection molding machines feeding into the same metalizing and disc handling system. This enables one line to manufacture two different selections at a time.

INJECTION MOULDING

The mold on the injection-molding unit is divided into two halves. Once opened, a stamper is installed on one half of the mold. This procedure must be carefully carried out because it is easy to damage both the stamper and the face of the mold. The cavity for the stamper is actually the shape of a CD. Once installed, the machine is set to cycle. Extremely dry, polycarbonate granules are drawn into a high temperature extruder just before the mold. The granules are liquefied and the 370-degree liquid polycarbonate is pumped into the mold, filling the mold cavity and pressing the plastic against the stamper. The digital imprint from the stamper is now formed on the plastic and quickly cooled in the mold. An arm then enters the mold and extracts the clear imprinted plastic Disc.

METALLIZATION & SPIN COATING

In order for a CD player to read the Disc the laser in the player needs a reflective surface. The clear Discs just molded are put into a metallization unit in which a thin layer of aluminum is molded onto the pitted side of the Disc. Immediately after, the aluminum coat is protected with a layer of ultraviolet lacquer, which protects the pits, metal coat and also provides a surface in which to print on. The diagram to the right shows a Disc being lowered into the processing cup where the lacquer coat is applied.

The surface of each Disc is viewed by means of three electronic cameras. Discs that contain surface flaws are rejected and the data is collected to give a computerized report on the efficiency level of each mold. The report gives results of the past 100 Discs and also for the entire shift. Information of this type is essential in determining some of the technical adjustments that are necessary. Finished products are stored on spindles of 175 units each and are put onto a cart ready for the next operation.

SCREEN STENCIL PREPARATION

After the replication stage, CDs will be labeled. Each product manufactured at the plant is provided with a series of positive films. Depending on the image required, anywhere from one to five films can be used. For this process, nylon screens are stretched uniformly on a stainless steel frame. With the aid of water and a screen preparation coat, a sheet of emulsion is attached to the screen and is set to dry.

The next step is to inscribe the image from the film, onto the emulsion on the nylon screen. Each film is temporarily attached to the screen emulsion-side in. The screen is then placed in a timed light-exposing unit that shines bright light through the film onto screen emulsion. After the exposing time is complete, the film is removed and the screens are rinsed in warm water (shown left). Any areas exposed to light will harden to the nylon screen. Areas blocked from the light will wash out completely. After the rinsing is complete, the screen is again put in a dryer.

SILK SCREEN PRINTING

When an order is ready to be printed, the proper screens are acquired, filled with ultraviolet ink and installed on a five head silk screen printer. At each head, a squeegee forces ink through the screen stencil image as the Discs passes under the screen. After each layer of ink is applied, it is immediately exposed to an ultraviolet light so the ink will dry and accept another layer of ink. Projects that require a lot of detail usually need a five color process. In these cases the five standard colors used are: WHITE, CYAN, MAGENTA, YELLOW, and BLACK. Alignment of each screen is essential for a properly registered picture.

COLLATION & PACKING

The final stage of manufacturing is packaging. This requires placing the CD in a plastic jewel case along with the paper artwork that has been chosen for each selection.

On the machine, shown right, is a compartment for each part: the jewel case, inlay card, tray, booklet and finally the CD. They are all loaded onto the machine. As the machine cycles, the jewel case advances through the machine while other components are placed inside it. As it finishes, the jewel case is automatically closed. The encased CD then exist the machine, traveling down a conveyer and enters a wrapping machine. The wrapping machine seals the edges of the package and, if required, a sticker is applied, before stacking the CDs into piles of 25 units. The packing clerk then boxes each stack and places them on a skid.

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We also offer disc replication services for CD, CD-ROM, Enhanced-CD, VCD, Audio-VCD, DVD, and DVD-ROM. Please contact us for your inquiries and quotation requests.