PCB News - Waste gas treatment method of pcb electronics factory-low temperature plasma technology

Waste gas treatment method of PCB electronics factory-low temperature plasma technology

Before the presentation of the PCB, the circuit was a PCB circuit board formed by point-to-point wiring consumption. The reliability of that method is very low, because with the aging of the circuit, the split of the circuit will lead to the open circuit or short circuit of the circuit node. Winding technology is a serious advancement in circuit technology. That method improves the durability and changeability of the circuit by winding small-diameter wires on the poles at the adjoining points.

When the electronics industry develops from real ATCs and relays to silicon semiconductors and integrated circuits, the size and price of electronic components are also reduced PCB circuit board consumption. Electronic products appear more and more frequently in the consumer category, prompting manufacturers to look for smaller and more cost-effective plans. Thus, PCB was born.

PCB manufacturing is very complicated. Taking the four-layer printed board as an example, the manufacturing process mainly includes PCB planning, core board manufacturing, inner PCB planning transfer, core board /////punching and checking., Lamination, drilling, copper chemical precipitation on the hole wall, outer PCB planning transfer, outer PCB etching and other steps to adjust the PCB circuit board consumption.

1. PCB planning

The first step in PCB manufacturing is to sort out and check PCB layout (Layout) PCB circuit board consumption. The PCB manufacturing workshop receives the CAD files from PCB Design Company. Because each CAD software has its own unique file format, the PCB workshop will be transformed into the same format-Extended Gerber RS-274X or Gerber X2. Then the engineers in the workshop will check whether the PCB planning fits the manufacturing process and whether there are any defects.

2. Manufacturing of core board

Cleaning the copper clad laminate, if there is dust, may cause the initial circuit short circuit or open circuit PCB circuit board consumption.

The following figure is an example of an 8-layer PCB. In reality, it is a PCB circuit board that consists of 3 copper clad laminates (core boards) plus 2 copper films, and then glued together with prepregs. The sequence of making is to start with the middle core board (4th and 5th layer lines), inexhaustibly superimpose it all the way, and then fix it. The fabrication of 4-layer PCB is similar, except that only one core board and two copper films are used.

3. The transfer of inner-layer PCB planning must first produce the two-layer circuit PCB circuit board consumption of the middle core board (Core). The copper clad laminate will be covered with a photosensitive film after cleaning. That kind of film will solidify when exposed to light, forming a protective film on the copper foil of the copper clad laminate.

The two-layer PCB planning film and the double-layer copper clad laminate are initially inserted into the upper PCB planning film to ensure that the upper and lower PCB planning films are stacked in a precise position for PCB circuit board consumption.

The photosensitive machine uses a UV lamp to stop irradiating the photosensitive film on the copper foil. Under the light-transmitting film, the photosensitive film is cured, and the uncured photosensitive film PCB circuit board is still consumed under the opaque film. The copper foil covered under the cured photosensitive film is the required PCB planning circuit, which is equivalent to the influence of the laser printer ink of the manual PCB.

Then use lye to clean the uncured photosensitive film, and the required copper foil circuit will be covered by the cured photosensitive film for consumption on the PCB circuit board.

Then use a strong alkali, such as NaOH to etch the unnecessary copper foil away from the PCB circuit board consumption.

Tear off the cured photosensitive film to expose the required PCB planning circuit copper foil PCB circuit board consumption.

4. Core board punching and inspection

The core board has been made into the successful PCB circuit board consumption. Then punch alignment holes on the core board to facilitate alignment with other materials. Once the core board is pressed along with the other layers of the PCB, it cannot be modified, so it is very important to check. The machine will take the initiative to stop the comparison with the PCB planning drawings to check for errors.

5. Laminating

There needs a new raw material called prepreg, which is the adhesive between the core board and the core board (PCB layers>4), as well as the core board and the outer copper foil, and it also serves as an insulating effect for the production of PCB circuit boards.

The lower copper foil and the two layers of prepreg have been fixed in position through the alignment hole and the lower iron plate in advance, and then the finished core board is also placed in the alignment hole. Initially, the two layers of prepreg and a layer of copper foil And a layer of pressure-bearing aluminum cage cover to the core board PCB circuit board consumption.

The PCB boards clamped by the iron plates are placed on the rack, and then sent to the solid air heat press to stop the consumption of laminated PCB circuit boards. The high temperature in the solid-air hot press can melt the epoxy resin in the prepreg and fix the core boards and copper foils together under pressure.

PCB board manufacturing process explanation, moving pictures to reveal the PCB board production process-No. 12

After the lamination is completed, the upper iron plate PCB circuit board of the pressed PCB is removed for consumption. Then remove the pressure-bearing aluminum plate. The aluminum plate also has the responsibility of isolating the difference PCB and ensuring the smoothness of the outer copper foil of the PCB. The cities on both sides of the PCB taken out at that time were covered by a layer of smooth copper foil.

6. Drilling

To connect the 4 layers of non-contact copper foil in the PCB together, first drill through the through holes to pass through the PCB, and then metalize the hole walls to conduct the PCB circuit board consumption.

Use an X-ray drilling machine to stop the positioning of the inner core board. The machine will actively find and locate the holes on the core board, and then punch positioning holes on the PCB to ensure that the next drilling is from the center of the hole. Through PCB circuit board consumption.

Put a layer of aluminum plate on the punching machine machine tool, and then put the PCB on the PCB circuit board for consumption. In order to improve efficiency, according to the number of PCB layers, 1 to 3 PCB boards will be stacked together to stop perforation. At first, a layer of aluminum was covered on the uppermost PCB. The upper and lower layers of aluminum were used to prevent the copper foil on the PCB from tearing when the drill bit drilled in and out.

In the previous lamination process, the melted epoxy resin was squeezed out of the PCB, so it is necessary to stop cutting off the PCB circuit board consumption. The profiling milling machine stops cutting its periphery according to the accurate XY coordinates of the PCB.

7. Copper chemical precipitation on the hole wall

Because almost all PCB designs use perforations to stop the wiring of different layers of the connection, a good connection requires a 25-micron copper film to be consumed on the PCB circuit board on the hole wall. The thickness of the copper film needs to be achieved by electroplating, but the hole wall is made of non-conductive epoxy resin and glass fiber board.

Therefore, the first step is to deposit a layer of conductive material on the hole wall, and use the chemical accumulation method to form a 1-micron copper film PCB circuit board on the entire PCB surface. The entire process is like chemical treatment and cleaning, etc., which are all controlled by machines.

Fixed PCB

Cleaning the PCB

8. Outer PCB planning transfer

Next, the PCB plan of the outer layer will be transferred to the copper foil. The process is similar to the previous transfer principle of the inner core board PCB plan. They are all used to transfer the PCB plan to the copper foil by using the photocopying film and photosensitive film. The difference is that positive films will be used for PCB circuit board consumption.

The internal PCB planning transfer adopts the subtractive method, and the negative film is adopted as the PCB circuit board consumption. The circuit is covered by the cured photosensitive film on the PCB, and the uncured photosensitive film is cleaned. After the exposed copper foil is etched, the PCB planning circuit is protected by the cured photosensitive film.

The outer PCB planning transfer adopts the general method, and the positive film is used as the PCB circuit board consumption. The non-circuit area is covered by the cured photosensitive film on the PCB. After cleaning the uncured photosensitive film, stop the electroplating. Where there is a film, it cannot be electroplated, and where there is no film, copper is plated first and then tin is plated. After the film is removed, the alkaline etching is stopped, and the tin is removed initially. The circuit pattern remains on the board because it is sheltered by tin.

Clamp the PCB with clips, and electroplate the copper to the PCB circuit board for consumption. As mentioned earlier, in order to ensure that the holes have sufficient conductivity, the copper film plated on the hole walls must have a thickness of 25 microns, so the entire system will be actively controlled by the computer to ensure its accuracy.

9. Outer PCB etching

Follow the source of a complete automated assembly line to complete the etching process PCB circuit board consumption. First, clean the cured photosensitive film on the PCB board. Then use strong alkali to clean the unnecessary copper foil covered by its cage. Then use the tin stripping solution to strip the tin plating on the PCB planning copper foil. After cleaning, the 4-layer PCB planning is completed.