Laboratory Rapid PCB Fabrication MethodPosted on 2020-07-09
PCB is the basic component of electronic components. PCB fabrication is a basic experimental skill for electronics professionals and electronic engineers. Although PCB manufacturing technology has matured sufficiently, if they just want to prove their design, it is unrealistic and unnecessary to produce circuit boards that conform to professional PCB fabrication processes because it is time-consuming and costly. Therefore, this article will provide a simple method to produce double-sided PCB, so that electronics professionals and engineers can have a better alternative.
Rapid PCB fabrication method
There are two main methods of PCB fabrication: chemical mode and physical mode. Today, the most popular PCB manufacturing methods in high school are thermal transfer and physical engraving. The former belongs to the field of chemistry, the latter belongs to the field of physics.
Thermal transfer printing
For thermal transfer, the first is the use of ordinary laser printers to print PCB images onto special thermal transfer paper. Then, the PCB image that has been printed on the thermal transfer paper is transferred to the copper-clad laminate (CCL) by the thermal transfer device. Finally, high-precision PCBs are produced after subsequent processes (including etching and PCB drilling). In the high school laboratory, thermal transfer printing can be used to produce high-precision PCBs and can be completed within an hour. When it comes to double-sided PCB manufacturing, a prominent problem is that misalignments that have not been successfully resolved using current manufacturing methods are not used. Therefore, the double-sided PCB manufactured by the thermal transfer method cannot achieve the best work on electronic products.
Thermal transfer printing adheres to the following PCB manufacturing process:
- The bottom PCB image is printed on a sheet of thermal transfer paper by an ordinary laser printer.
- The top PCB image is printed on another thermal transfer paper by a common laser printer.
- Two sheets of thermal transfer paper are closely attached to the well-cut double-sided CCL. Scotch tape can be used to fix the position of paper and printing plates to avoid misalignment.
- Thermal transfer printing is performed by sticking CCL and thermal transfer paper in a thermal transfer device. Then, after cooling, the CCL printed with the PCB image is obtained.
- Then etching and PCB drilling are performed.
The process can be summarized as the following figure:
In all stages of thermal transfer printing in PCB manufacturing, the application of step 3 can accurately lead to the alignment of two sheets of thermal transfer paper. However, when step 4 is involved, misalignment often results in heat transfer equipment. Therefore, unless several trials are conducted, double-sided PCBs are difficult to manufacture successfully.
According to the basic principles of physical engraving, physical engraving conforms to the principle of milling. Milling off extra or unnecessary parts of CCL. The 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 PCB manufacturing, after milling on one side, the board should be turned over to mill on the other side of the board. The flipping process may cause misalignment, which should be corrected through software and hardware to reduce the scrap rate of double-sided PCBs.
Comparison of thermal transfer and physical engraving
According to the comparison of the two methods, thermal transfer is superior to physical engraving in the following aspects:
- CNC drilling and milling machines have a higher cost and occupy more laboratory space. However, the thermal transfer machine has the characteristics of lower cost and less space than the CNC drilling and milling machine.
- When using thermal transfer printing, double-sided PCB can be completed within one hour. Although there may be misalignment of multiple thermal transfer printing, a double-sided PCB can be manufactured in up to 3 hours. However, CNC drilling and milling machines require more time, at least 4 hours. In addition, CNC drilling and milling machines can only process one PCB board at the same time. Thermal transfer can produce multiple double-sided PCBs at the same time.
An improved thermal transfer method
In order to solve the problem of misalignment in traditional thermal transfer, an improved PCB manufacturing thermal transfer method will be provided, the following steps:
- The bottom PCB image and the mirror PCB image are printed on the same thermal transfer paper. And the holes of the bottom PCB image and the top PCB image are linearly symmetrical.
- The thermal transfer paper is folded along the line of symmetry and covered on the well-cut double-sided CCL.
- Then put the double-sided CCL with thermal transfer paper into the thermal transfer printing device for thermal transfer. The folded part first enters the thermal transfer device, and after cooling, the CCL printed with the PCB image can be obtained. Etching and PCB drilling.
By printing the top and bottom PCB images on the same thermal transfer paper. The above process can effectively solve the misalignment problem used for PCB manufacturing in traditional thermal transfer printing. Therefore, a reliable double-sided PCB can be smoothly manufactured at one time.
The printing of PCB images on the same thermal transfer paper can be done based on any software that holds different PCB designs. All in all, this improved PCB manufacturing thermal transfer printing method is most effective for electronic professionals or engineers who can be used in the laboratory to produce double-sided PCBs.