Electronic Design - Rapid printed circuit board production system

After a long period of exploration and research, a low-cost, easy-to-use small and fast printed circuit board manufacturing system was finally developed. The system consists of a fast microcomputer numerical control thermal transfer plate making machine and a fast corrosion machine. The thermal transfer plate making machine was inspired by the research on laser printers. Our researchers found that the "toner" of laser printers as we know it is not inorganic toner, but black plastic particles containing magnetic substances. . It is attracted by the static electricity of the toner cartridge of the laser printer, and high-precision graphics and text are arranged on the toner cartridge. After the static electricity is eliminated, it is transferred to the printing paper and fixed by high temperature melting and hot pressing to form a laser printer work. Under the manifestation of this discovery, our researchers have developed heat transfer paper with high temperature resistance and non-adhesion characteristics, fast microcomputer numerical control heat transfer plate making machine and fast corrosion machine. Using this system, printed circuit boards can be produced very quickly in small batches. Compared with the previous traditional photo-engraving method, the system has the following significant advantages:

1. High plate accuracy: it can reach the plate-making accuracy of laser printer resolution. In addition to producing fine circuit graphics, it can also produce high-resolution images. It can not only make fine printed circuit boards, but also make exquisite metal signs and metal craft paintings.

2. Low cost of plate making: the cost of making a circuit board is only equivalent to the cost of a piece of thermal transfer paper.

3. Fast plate making speed: the fast thermal transfer plate making machine can quickly transfer the printed circuit pattern printed on the thermal transfer paper by the laser printer to the circuit board to form an anti-corrosion layer to produce a 200mm*300mm printed circuit board, It only takes 10-20 minutes. Very suitable for factories, research institutes, schools, electronic shopping malls to quickly produce circuit board prototypes.

4. Multi-purpose: It can produce double-sided panels and single-sided panels with characters at one time, or double-sided panels with characters in two parts.

5. High degree of automation, extremely simple operation: fast thermal transfer plate making machine, using 89c2051 as the main control chip. The temperature measurement and setting of the rubber roller by the plate making machine; the circuit board enters and exits; the power on, and the motor delay stop function set to avoid overheating of the rubber roller when shutting down are all automatically controlled by the touch switch.

6. The equipment is cost-effective: This heat transfer type rapid plate making system replaces the traditional printed circuit board production process, the equipment is low in price, and the cost performance is extremely high. Generally, the investment and purchase of equipment for the rapid production of printed circuit board production and management in the same month can be used. Recover all investment. The operation and working principle of the plate making machine The printed circuit board graphics made by the computer are printed on the special heat transfer paper that has been specially processed by a laser printer, and then the transfer paper is covered on the copper-clad plate and sent to the plate making machine plate. .

The working principle of the plate making machine mainly adopts the principle of heat transfer, and its structure is similar to that of a laser printer. There are two groups of 4 specially made high-temperature resistant silicone cylindrical rollers to form a transmission mechanism. Two infrared quartz heating tubes are used to evenly heat a group of two silica gel cylindrical rollers to 180.5°C. At the same time, each group of two silica gel cylindrical rollers is also two pressure rollers. Its surface can withstand a maximum temperature of 300 degree Celsius, the two sets of rubber rollers are driven by a synchronous motor through a transmission system, and rotate at a constant speed of two revolutions per minute.

When the thermal transfer paper and the copper-clad board pass through the gap between the silica gel cylindrical rollers with higher temperature and greater pressure, the toner adsorbed on the thermal transfer paper will melt. Since the thermal transfer paper is specially processed, its surface is covered with several layers of special material coatings through polymer technology, so that the thermal transfer paper has the characteristics of high temperature resistance and non-sticking. When the temperature reaches 180.5 degree Celsius, the adsorption force of the thermal transfer paper on the melted toner drops sharply. Under the action of pressure, the melted toner is completely adsorbed on the copper-clad board. After the copper-clad board cools, a tight print is formed. Graphics, complete the entire thermal transfer process. With the same principle, if you need to transfer the PCB component layout on the other side of the printed board, it can also be done at the same time as the plate making, so that the printed board can reach a more professional level.

What needs to be explained here is that the entire heat transfer process has extremely high requirements for temperature, and temperature control is very important. For example: the best melting temperature of toner is generally 180.5 degree Celsius. When the temperature is too high, the excessively melted toner will spread around the original lines, causing blurred graphics, poor accuracy, and even scorching the paper in severe cases. . When the temperature is too low or the temperature is not uniform, the transfer effect will be poor, or even the transfer will not be possible. In actual use, due to factors such as air temperature, humidity, thickness of paper and circuit board, etc., have a certain influence on the transfer effect, so the temperature control is very important for the quality of the transfer effect. For this reason, the temperature control sensors of the thermal transfer plate-making machine all use imported pt-1000 thin-film platinum resistors, so that the temperature control accuracy can reach 0.1 degree Celsius, which meets the higher temperature requirements of plate-making.

When the graphics are transferred to the copper-clad board, that is to say, the toner of the printer forms a graphic protective layer on the copper-clad board. Since the toner of the laser printer is made of polymer material containing resin, it has good corrosion resistance to the corrosive liquid (fecl3 solution), so after being corroded by the fecl3 solution, a beautifully crafted printed circuit board can be formed. In order to make the corrosion of the circuit board faster and more convenient, a corrosion machine is needed to quickly corrode the circuit board to save time, reduce the waste of fecl3 solution, and improve efficiency. The rapid corrosion machine quickly heats the fecl3 solution to above 60°C, and then uses the anti-corrosion small circulating submersible pump to evenly spray the fecl3 solution to the printed board through a special nozzle.

Generally, when heated to 80°C, use a high-concentration fecl3 solution to corrode, and the corrosion can be completed in 5-6 minutes. Due to the rapid corrosion process, side corrosion can be reduced, and the fineness of the printed circuit board is more perfect and reliable. The oxidation-reduction reaction of the fecl3 solution is accelerated by heating, thereby accelerating the oxidation of copper on the surface of the copper-clad board to cu2+; at the same time, the impact of the water flow is used to take away the cu2+ deposited on the surface of the copper-clad board and nearby, so that the chemical reaction proceeds faster and more fully. This machine is especially suitable for the production of large PCB printing plates.

The entire corrosion process is carried out in a semi-closed condition, which has the advantages of cleanliness and reduced corrosion liquid evaporation, so it is very suitable for small batch production of printed circuit boards in laboratories, research institutes, and factories. After the printed circuit board is corroded, use a special drill to drill the circuit board. This special drill is inlaid with a cylinder. It can also grind off the toner near the drilling while completing the high-speed drilling. Very clean pads. The other toners covering the copper foil form a good solder mask.

Using this rapid printed circuit board production system, metal signs and metal craft paintings can also be produced. They are also very exquisite, with particularly clear levels, and extremely low cost. With the advantages of rapid plate making, I believe it will be available in these in the near future. It can be more widely used in the PCB industry. Although the accuracy of the printed circuit boards produced by this system can reach a very high professional level, there are still some defects: due to different laser printers, excessive weather and humidity, local defects in thermal transfer paper, etc., toner will appear. Some phenomena such as poor adhesion on the thermal transfer paper.