There are two main methods for quick turn PCB fabrication: chemical mode and physical mode. Nowadays, the most popular PCB manufacturing methods in high school are heat transfer printing and physical engraving. The former belongs to the field of chemistry and the latter belongs to the field of physics.
Heat transfer printing.
First of all, ordinary laser printer is used to print PCB images on special heat transfer paper. Then, the PCB image that has been printed on the heat transfer paper is transferred to the copper-clad laminate (CCL) through the heat transfer device. Finally, the high-precision PCB is produced after the subsequent process (including etching and PCB drilling). In the high school laboratory, heat transfer printing can be used to produce high-precision PCB and can be completed in an hour. When dual-sided PCB manufacturing is involved, the outstanding problem is that the misalignment that has not been successfully solved by the current manufacturing method is not used. Therefore, the double-sided PCB manufactured by heat transfer printing method can not achieve the best work on electronic products.
Thermal transfer printing adheres to the following PCB manufacturing process:
1。 The bottom PCB image is printed on a piece of heat transfer paper by an ordinary laser printer.
2。 The image of the top PCB is printed on another sheet of heat transfer paper by a normal laser printer.
3。 Two pieces of heat transfer paper are tightly attached to the cut double-sided CCL. The transparent tape can be used to fix the position of paper and plate to avoid dislocation.
4。 Heat transfer printing is carried out by sticking CCL and heat transfer paper in the heat transfer equipment. Then the CCL with PCB image is obtained after cooling.
5。 Then etching and PCB drilling are performed.
The process can be summarized as follows:
Laboratory quick turn PCB fabrication method
In all stages of heat transfer printing of quick turn PCB fabrication, the application of step 3 can accurately lead to the alignment of two heat transfer sheets. However, when step 4 is involved, misalignment often results in heat transfer equipment. Therefore, it is difficult to successfully manufacture double-sided PCB unless several tests are carried out.
· physical sculpture.
According to the basic principle of physical engraving, physical engraving conforms to the milling principle, milling out extra or unnecessary parts of CCL. Application equipment is actually a small CNC drilling and milling machine, also known as a circuit board engraving machine. In the process of double-sided quick turn PCB fabrication, the board should be turned over to mill on the other side of the board after milling on one side. The overturning process may cause dislocation, which should be corrected by software and hardware to reduce the reject rate of dual-sided PCB.
Comparison of thermal transfer printing and physical engraving.
According to the comparison of the two methods, heat transfer printing is better than physical engraving in the following aspects: 1. CNC drilling and milling machine has a higher cost and takes up more laboratory space. However, compared with NC drilling and milling machine, heat transfer machine has the characteristics of low cost and small space occupation.
2。 When using heat transfer printing, it can complete double-sided PCB in one hour. Although there may be multiple thermal transfer printing dislocations, it is possible to produce dual-sided PCB within 3 hours at most. However, CNC drilling and milling machines take more time, at least four hours. In addition, CNC drilling machines and milling machines can only process one PCB at the same time, while heat transfer printing can produce multiple double-sided PCBs at the same time.
An improved heat transfer printing method.
In order to solve the problem of dislocation in traditional heat transfer printing, this paper will provide an improved quick turn PCB fabrication method, the following steps.
1。 The bottom PCB image and mirror PCB image are printed on the same heat transfer paper, and the holes of the bottom PCB image and the top PCB image are linearly symmetrical.
2。 The heat transfer paper is folded along the symmetry line and covered on the well-cut double-sided CCL.
3。 Then the double-sided CCL with heat transfer paper is put into the heat transfer printing equipment for heat transfer printing. The folding part first enters the heat transfer equipment, and after cooling, the CCL printed with a PCB image can be obtained. Etching and PCB drilling.
By printing the top and bottom PCB images on the same heat transfer paper, the above process can effectively solve the misalignment problem of quick turn PCB fabrication in traditional heat transfer printing. Therefore, reliable double-sided PCB can be manufactured smoothly at one time.
PCB image printing on the same sheet of heat transfer paper can be performed based on any PCB design software with different holding. All in all, this improved PCB manufacturing heat transfer printing method is the most effective for electronic professionals or engineers who can be used in the laboratory to produce dual-sided PCB.