CO2 laser drilling process in the hottest PCB indu

2022-09-23
  • Detail

CO2 laser drilling technology in PCB industry

the drilling methods of CO2 laser drilling mainly include direct drilling method and shape mask drilling method. The so-called direct hole forming process is to modulate the diameter of the laser beam through the main control system of the equipment to the same diameter as the hole on the processed printed circuit board, and directly perform hole forming processing on the insulating medium surface without copper foil. The forming mask process method is to coat a special mask on the surface of the printed board, and use the conventional process method to remove the copper foil on the hole surface through the exposure/development/etching process to form a forming assured product window. Then irradiate these holes with a laser beam larger than the aperture, and cut off the exposed dielectric layer resin. Now it is introduced as follows:

(1) copper window opening method:

first, a layer of RCC (resin coated copper foil) is re pressed on the inner plate to make the window by photochemical method, then the resin is etched to expose the resin, and then the substrate material in the window is burned by laser to form micro blind holes

(2) process method of opening a large window:

the diameter of the hole formed by the former process method is the same as that of the opened copper window. If the operation is slightly careless, the position of the opened window will deviate, resulting in the displacement of the position of the blind hole of the hole and the misalignment with the center of the bottom pad. The deviation of the copper window may be caused by the expansion and contraction of the substrate material and the deformation of the negative film used for image transfer. Therefore, the process method of opening a large copper window is to expand the diameter of the copper window to about 0.05mm larger than the bottom pad (usually determined according to the size of the aperture. When the aperture is 0.15mm, the diameter of the bottom pad should be about 0.25mm, and the diameter of the large window is 0.30mm). Then, the exciting drilling is carried out, and the position can be burned out to accurately align the micro blind hole of the bottom pad. Its main feature is that it has a large degree of freedom to choose. When laser drilling, you can choose to press the program of the inner bottom pad to form the hole. This effectively avoids the deviation caused by the same diameter of the copper window and the formed hole, which makes the laser point unable to align the window, so that many incomplete half holes or residual holes will appear on the surface of large batches of large-scale splicing plates

(3) process method of direct pore forming on resin surface

there are several types of process methods of laser drilling:

a. the substrate is to press the resin copper foil on the upper layer of the inner plate, and then etch all the copper foil away, then CO2 laser can be used to directly form holes on the exposed resin surface, and then continue to carry out pore forming treatment according to the plating hole process method

b. the substrate adopts FR-4 semi cured sheet and copper foil to replace the damaged grease copper foil

c. the process of coating photosensitive resin and subsequent lamination of copper foil

d. it is made by using dry film as the dielectric layer and copper foil

e. coating other types of warm film after cutting off the power and copper foil lamination are made during the registration period from February 18 to March 10, respectively

(4) using the direct ablation process of ultra-thin copper foil

after the resin copper foil is pressed and coated on both sides of the inner core plate, the thickness of the copper foil 17m can be reduced to 5 microns by "half etching" after etching, and then black oxidation treatment can be carried out, and CO2 laser can be used to form holes

its basic principle is that the oxidized black surface will strongly absorb light, which will directly form holes on the surface of ultra-thin copper foil and resin on the premise of improving the beam energy of CO2 laser. But the most difficult thing is how to ensure that the "semi etching method" can obtain a copper layer with uniform thickness, so we should pay special attention to it when making it. Of course, copper backed tearing material (UTC) can be used, and the copper foil is quite thin, about 5 microns. (end)

Copyright © 2011 JIN SHI