What is Cut?
Cutting is the process of cutting the original copper-clad board into a board that can be made on the production line.
Generally, the purchased materials come in the following sizes: 36.5 INCH × 48.5 INCH, 40.5INCH X 48.5 INCH, 42.5 INCH X 48.5 INCH, etc. PCB design engineers and PCB production engineers always consider how to maximize the use of PCB raw materials throughout the process.
Inner dry film?
The inner dry film is the process of transferring the inner circuit pattern to the PCB board. In PCB production, we will mention the concept of graphics transfer, because the production of conductive graphics is the foundation of PCB production.
The inner film is a special photosensitive film on the surface of the copper plate. This film will cure when exposed to light, forming a protective film on the board. Exposure development is to expose the board to which the film is attached. The light-transmitting part is cured, and the part that does not transmit light is still a dry film. Then, after development, the uncured dry film is removed, and the board with the cured protective film is etched. After the film removal process, the inner circuit pattern is transferred to the board.
The boards with inner layer wiring must be blackened or browned before they can be laminated.
The purpose of blackening and browning:
1. Remove contaminants such as oil and impurities on the surface;
2. Increase the specific surface of the copper foil, thereby increasing the contact area with the resin, which is conducive to the full diffusion of the resin and the formation of a larger bonding force;
3. Make the non-polar copper surface into the surface with polar CuO and Cu2O, increase the polar bond between the copper foil and the resin;
4. The oxidized surface is not affected by moisture at high temperature, reducing the chance of delamination of copper foil and resin.
Lamination is the process of bonding layers of circuits into a whole by means of B-stage prepreg. This bonding is achieved by the interdiffusion and penetration of large molecules on the interface.
Purpose: Press the discrete multi-layer board together with the adhesive sheet into the multi-layer board with the required number of layers and thickness.
Mechanical drilling is to use a drill to cut at high speed to form a through hole on the PCB.
Decontamination and sinking copper
Purpose: Metallize the through hole.
The substrate of the circuit board is composed of copper foil, glass fiber and epoxy resin. In the manufacturing process, the cross-section of the hole wall after the substrate is drilled is composed of the above three parts.
The metallization of the hole is to solve the problem of covering the cross-section with a uniform, thermal shock-resistant metal copper.
Sink copper and thickened copper
The metallization of holes involves a concept of capability, thickness-to-diameter ratio. Thickness-diameter ratio refers to the ratio of plate thickness to aperture. When the board is getting thicker and the pore size is continuously decreasing, it is more and more difficult for the chemical liquid to enter the depth of the drill hole. Thin coating is still inevitable. At this time, there will be a slight open circuit in the drilled layer.
Dry film & pattern plating
The outer layer graphics transfer is similar in principle to the inner layer graphics transfer. Both use photosensitive dry film and photographic methods to print circuit patterns on the board.
Wet film solder mask
Concept: The solder mask process is to add a layer of solder mask on the surface of the board. This layer of solder mask is called Solder Mask or Solder Mask Ink, commonly known as green oil. Its role is mainly to prevent undue tin on conductor lines, etc., prevent short circuits between lines due to moisture, chemicals, etc., disconnection, insulation caused by bad operations during production and assembly, and resistance to various harsh environments Printed board functions, etc. Coupled with its long production time and many production methods, it is an important process in PCB production.
What is E-TEST?
The electronic test is the electrical performance test of the PCB, which is usually also called the “on” and “off” test of the PCB. Among the electrical test methods used by PCB manufacturers, needle bed test and flying probe test are the most commonly used.