Industrial printing

In the 20th century when science and technology flourished, strictly speaking, there was no boundary in the application of science and technology. The 19th century invented photography, applied to the printing industry, produced photo-engraving; applied to film, film photography. Printing can be used not only for graphic printing of newspapers and magazines, but also for printing of securities. In general, wherever photo transcription is required, there is a place for printing.

The "industrial printing" in this chapter refers to the use of printing and graphic transfer printing technology in the production of certain other industrial products. These industries generally do not belong to the printing industry, and the products they produce are not printed products, but it allows people to see that in the broader field of industrial production, printing has shown its vitality again and again.

Printing > Section 1 Electronic Printing

In electronic products, the production of early printed circuit boards and the production of integrated circuit boards since the 1970s have used photocopying and photo etching techniques in printing. It should be said that this is another contribution of printing to modern civilization.

Printed Circuits > I. Printed Circuits

Early radios and televisions were all components, such as resistors, capacitors, tubes, etc., were first installed on the base or base, and then welded together by wire. This production and processing method not only has low production efficiency, but also has poor product performance and large product volume. In order to improve the reliability of electronic products and reduce the volume, from the 1950s onwards, people used pre-designed circuit diagrams to make original photographs using photolithographic methods, and then used the printing method to print the circuit diagrams to cover. The copper foil on the insulation board is then chemically etched so that the copper foil layer is left where the wire connection is required, and the copper foil layer that does not need to be electrically conductive is etched away to become an insulating layer. After punching, plating, and finishing, it becomes a printed circuit board. In addition to forming a certain conductive line, it also has a certain thickness and strength, and actually plays two roles: one is as a carrier of some related electronic components, and the other is a conductor connecting these components. It is installed in electronic products, it is only one part of the overall electronic product.

Since the manufacturing method of printed circuit boards is basically similar to that of copper-zinc printing in the printing industry, since the 1960s, some printing companies or copper-zinc plate-making plants in cities like Beijing, Tianjin, Shenyang, Shanghai and Guangzhou have excluded The printing industry manufactures copper-zinc plates, and also undertakes the task of processing some printed circuit boards. There are also printed circuit board production workshops in factories that manufacture electronic products. Although the name is called "printed circuit board", it is not printed by printing, but it is made by photolithography. It can also be said that the combination of printing and electronic technology results.

1. Printed circuit substrate

The printed circuit board is mainly composed of two parts: an insulating layer and a conductive layer. The insulating layer is formed by laminating reinforcement materials such as cloth, paper, asbestos, nylon fiber cloth or glass fiber cloth after being immersed in the binder resin solution for drying. The conductive layer is a copper foil pressed on the resin layer.

(1) Reinforcement material. It is the skeleton of the printed circuit board, generally cloth, paper, asbestos, nylon fiber cloth or glass fiber cloth. The cotton used in the initial period. However, due to its high hygroscopicity and low mechanical strength, the cotton cloth was later replaced by other fiber materials. Insulating paper and glass fiber cloth were used more often.

(2) Adhesive materials. After the fiber reinforced material is impregnated with the binder solution, the resin polymer of the binder fills the gap between the fibers, and after drying and pressing, it becomes an insulating plate, which not only enhances the insulation performance of the fiber, but also sticks the fiber layer. The knot becomes a whole. Early adhesive materials generally used phenolic resin. This source of material is convenient, inexpensive, and also has good insulation properties and mechanical strength. Since the 1980s, with the development of electronic technology, people have increasingly improved the performance requirements of printed circuit boards. We have also developed a better epoxy resin as a bonding material. Epoxy resins are superior to phenolic resins in terms of electrical insulation, thermal stability, moisture barrier, etc., but the price is more expensive than the former.

(3) Conductive materials. The conductive material of the printed circuit board is mainly a copper foil produced by an electroplating method. From the conductivity requirements, the purity of the copper foil is, of course, the better, at least not less than 99.5%. The thickness of the copper foil can be selected according to the design requirements of the printed circuit board. The thickness of copper foil used in China is generally 35-50 micrometers, and there are also thinner ones such as 10 micrometers and 18 micrometers; and thicker than 70 micrometers.

(4) Copper clad laminate. The reinforcing fiber material is immersed in the binder resin material solution, laminated after drying, and pressed together with the conductive copper foil under heating conditions for a certain period of time to become a copper clad laminate made into a printed circuit (base) board. Copper clad laminates have single-sided and double-sided copper-clad laminates, which can be selected according to the needs of electronic products.

2. Photographic film

The designer designed the drawings according to the requirements of the electronic circuit. Take the drawings as originals and take pictures on the plate making camera to make photographic negatives. Due to the difference in the nature of the etched photosensitive resist, the photographic negative may be a positive or negative film. If the etched photosensitive resist is negative, like dichromated gelatin, the negative is used as a negative film; if the negative resist is positive, the negative is made by using a positive film. A positive film. Printed circuit design drawings are generally lines, symbols, text and solid blocks, there is no continuous tone change. The negatives produced by the negative film and testo should be black and white, and the edges of the lines are neat and smooth, with sufficient density contrast. This is the key to the quality of printed circuit boards.

3. Production of printed circuit boards

There are many kinds of process methods for making printed circuit boards. There are etching methods and plating methods. The etching method has been used more often since the 1950s. However, since the 1980s, with the increasing perfection of screen printing technology and its wide application in the electronics industry, it has also become common to make printed circuit boards by screen printing insulating layers and then electroplating. The latter is described separately below. This li1 is mainly about corrosion. This is a traditional method of manufacturing printed circuit boards. The process is roughly as follows:

(1) Coat photoresist on the substrate. Early sun-baked printed circuit boards commonly used protein, gelatin, or shellac aggravate chromate formulated into photosensitive adhesives. Since the 1970s, due to the large number of domestic polyvinyl alcohols, the application of polyvinyl dichromate emulsion was improved. First, the surface of the copper foil is polished with charcoal, washed with dilute hydrochloric acid, coated with photo-resist, and dried.

(2) Exposure, development, trimming, and baking. This operation is basically similar to the method of making copper and zinc plates.

(3) Corrosion. The application of printed circuit board manufacturing is chemical etching. Before the 1970s, corrosion was mainly performed with a ferric chloride solution in a special corrosion machine. Due to the difficulty in recovering ferric chloride corrosion solution and polluting the environment, after the 1970s, many factories gradually used acidic copper chloride solution for corrosion. The acidic copper chloride solution is added with hydrochloric acid in the CuClâ—†2 solution. When the etching solution reacts with the copper, the copper is eroded to form cuprous chloride CuCl. When the content of CuCl â—† 2 in the etching solution is reduced to a certain degree, the solution will lose its ability to corrode copper. At this time, Cl?2, a chlorine gas having a strong oxidizing ability, can be introduced into the etching solution to reoxidize a large amount of cuprous chloride accumulated in the etching solution to copper chloride, thereby recovering the corrosion ability of the solution.

The circuit board after the etching is completed is not yet a finished product. The process of printing the printed circuit board using the photolithography method was completed, and it was only after the completion of a series of processing such as mechanical processing and plating processing that it became an official electronic product.

Second, the lithography of integrated circuits

Since the second half of this century, electronic technology has been advancing by leaps and bounds. With the development of electronic technology from the transistor era into the era of integrated circuits, the production of printed circuit boards has become more sophisticated, resulting in the lithography of integrated circuits. It also evolved from photolithography in printing technology. If it is different from the above description of the production of printed circuits, it is the manufacture of integrated circuits that uses lithographic technology to produce electronic components with a smaller size, denser circuit layout, and more sophisticated processing equipment. technology.

Liquid resist

The printing industry and other industrial technologies have infiltrated and interacted with each other through the lithography of the electronics industry. The lithography technology for integrated circuit production is evolved from a photolithographic copper-zinc plate production technology. In the printing technology, the synthetic photosensitive resin applied in photolithography is vigorously developed under the promotion of photolithography technology.

Because the sensitization performance and resolution of dichromate emulsion cannot meet the requirements of lithography, in the early 1960s, a synthetic cinnamate polyvinyl alcohol ester photosensitive resin appeared in the world and was first used in electronics. Industrial lithography technology. In the mid-1960s, the author of this article was working at the Institute of Printing Technology of the People's Bank of China. He had synthesized a cinnamic acid polyvinyl alcohol ester photosensitive resin. After the "Cultural Revolution" turmoil, the institute was dissolved, resulting in no result. It. At the end of the 1960s, the Institute of Chemistry at the Chinese Academy of Sciences finally synthesized this photosensitive resin, which has been used in the manufacture of integrated circuits since the 1970s.

The cinnamic acid polyvinyl alcohol emulsion is a negative photosensitive adhesive, which means that the photosensitive adhesive at the photosensitive site is further cross-linked into a higher-order network-like polymer and loses its water solubility; the photosensitive adhesive in the non-photosensitive area contains polyvinyl alcohol molecules. Can be removed by water development. The film used for exposure is called a mask in the electronics industry. Because the photosensitive resin is negative, a negative mask is used for exposure. After exposure, developing and rinsing, the design of the designed integrated circuit is copied to the semiconductor device.

2. Dry film adhesive

Although the cinnamic acid polyvinyl alcohol photosensitive adhesive is superior to the traditional dichromate photosensitive adhesive in all respects such as its photosensitivity, it is still liquid, and it is inconvenient to store and use it. Since the late 1970s, a more convenient photosensitive material has been used in the electronics industry. This is dry film.

Using a polyester film substrate as a support, a polymer containing a propylene group was coated thereon. This layer of polymer is a negative photosensitive film. After the film is dried, it is covered with a polyethylene film as a protective layer to protect the photosensitive resist from contamination. It is called dry film photoresist because dry film photoresist can be pre-processed and stored for a long period of time. When it is used, the polyethylene film is peeled off and the photosensitive film is faced to the circuit board-based copper foil, heated and pressurized. Under the conditions, the photosensitive layer is attached to the copper foil. The film temperature of domestic G11, G21, G31, G41, SXM dry film is about 90～10