一、What is the purpose of blackening and browning when Shenzhen senyan Circuit Board Factory produces multi-layer PCB boards?
①Remove surface oil, impurities and other pollutants;
②The oxidized surface is not affected by moisture at high temperature, reducing the chance of delamination between copper foil and resin;
③ Make the non-polar copper surface into a polar CuO and Cu20 surface, increasing the polar bond between copper foil and resin;
④ 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 greater bonding force;
⑤The boards with the inner circuit must be blackened or browned before they can be laminated. It is the wiring copper meter for the inner board
oxidation treatment on the surface. Generally, the generated Cu 20 is red and CuO is black, so the Cu20-dominated oxide layer is called browning, and the CuO-dominated one is called blackening.
1. Lamination is the process of bonding each layer of circuits into a whole with the help of B-stage prepreg. This bonding is achieved through interdiffusion and penetration between macromolecules on the interface, and then interweaving. The process of bonding the various layers of circuits into a whole with a prepreg sheet. This bonding is achieved through the mutual diffusion and penetration of macromolecules on the interface, and then interweaving.
2. Purpose: To press the discrete multi-layer PCB board together with the bonding sheet into a multi-layer board with the required number of layers and thickness.
① Lamination process Send the stacked circuit board into the vacuum heat press. The heat energy provided by the machine is used to melt the resin in the resin sheet; to bond the substrate and fill the gap.
② Typesetting: Copper foil bonding sheet (prepreg), inner layer stainless steel, isolation board kraft paper, outer steel plate and other materials are laminated according to the process requirements. If the boards with more than six layers of circuit boards need pre-typesetting.
③ Lamination For designers, the first thing to consider in lamination is symmetry. Because the board will be affected by pressure and temperature during the lamination process, there will still be stress in the board after the lamination is completed. Therefore, if the two sides of the laminated board are uneven, the stress on the two sides will be different, causing the board to bend to one side, which greatly affects the performance of the PCB.
In addition, even if the distribution of copper is not uniform on the same plane, the flow rate of the resin at each point will be different, so that the thickness of the place with less copper will be slightly thinner, and the thickness of the place with more copper will be slightly thicker. In order to avoid these problems, factors such as the uniformity of copper distribution, the symmetry of the stack, the design and layout of blind buried holes, etc. must be carefully considered during the design.
二、Decontamination and copper sinking 1. Purpose: Metallize the through hole.
① The base material of circuit board proofing is composed of copper foil, glass fiber and epoxy resin. In the production process, the section of the hole wall after the substrate is drilled is composed of the above three parts of the material.
② Hole metallization is to solve the problem of covering the section with a uniform layer of metal copper that is resistant to thermal shock. Hole metallization is to solve the problem of covering the section with a uniform layer of metal copper that is resistant to thermal shock.
③The process is divided into three parts: 1. Decontamination process, 2. Electroless copper deposition process, 3. Thickened copper process (full board electroplating copper).
三、Immersion copper and thickened copper
The metallization of holes involves a concept of capacity. Thickness-to-diameter ratio. The aspect ratio refers to the ratio of the plate thickness to the hole diameter. , thickness-to-diameter ratio. The aspect ratio refers to the ratio of the plate thickness to the hole diameter. As the board becomes thicker and the hole diameter decreases, it becomes more and more difficult for the chemical yao water to enter the depth of the hole. Although the electroplating equipment uses vibration, pressure, etc. to allow the yao water to enter the center of the hole, the center caused by the concentration difference Thin coatings are still unavoidable. At this time, there will be a slight open circuit phenomenon in the drilling layer. When the voltage increases and the board is impacted under various harsh conditions, the defects are completely exposed, causing the circuit of the board to be disconnected, and the specified work cannot be completed.
Therefore, designers need to understand the process capabilities of circuit board manufacturers in a timely manner, otherwise the designed PCB circuit boards will be difficult to realize in production. It should be noted that the parameter of thickness-to-diameter ratio must be considered not only in the design of through holes, but also in the design of blind buried holes.
四、Outer layer dry film and graphic plating
The principle of the outer layer graphics transfer is similar to that of the inner layer graphics transfer. They both use photosensitive dry film and photographing methods to print the circuit graphics on the board. The difference between the outer dry film and the inner dry film is:
① If the subtraction method is used, the outer dry film is the same as the inner dry film, and the negative film is used as the board. The part of the cured dry film on the board is the circuit. Remove the uncured film and retreat the film after acid etching, and the circuit pattern remains on the board because it is protected by the film.
② If the normal method is adopted, then the outer dry film is made of a positive film. The cured part of the board is the non-circuit area (substrate area). Pattern electroplating is performed after removing the uncured film. Where there is a film, it cannot be electroplated, but where there is no film, it is first plated with copper and then tin. Alkaline etching is carried out after the film is removed, and finally the tin is removed. The circuit pattern remains on the board because it is protected by tin.
③Wet film (solder mask) The solder mask process is to add a layer of solder mask layer on the surface of the board. This layer of solder mask is called solder mask (Solder Mask) or solder mask ink, commonly known as green oil. Its function is mainly to prevent undesired tinning of conductor lines, prevent short circuits between lines caused by moisture, chemicals, etc., open circuits caused by poor operations in the production and assembly process, insulation and resistance to various harsh environments; ensure Printed board functions, etc. Principle: At present, this layer of ink used by PCB manufacturers basically uses liquid photosensitive ink. Its production principle is partly similar to that of line graphics transfer. It also uses the film to block the exposure and transfer the solder resist pattern to the surface of the PCB. The specific process is as follows:
五、Wet film
①Wet film process: pretreatment->coating->pre-baking->exposure->development->UV curing-related to this process is the soldmask file, which involves process capabilities including solder mask alignment accuracy , the size of the green oil bridge, the method of making the via hole, the thickness of the solder mask and other parameters. At the same time, the quality of the solder resist ink will also have a great impact on the later surface treatment, SMT placement, storage and service life. In addition, the whole process takes a long time to produce and has many production methods, so it is an important process in PCB production.
② Associated with this process is the soldmask file, which involves process capabilities including parameters such as solder mask alignment accuracy, green oil bridge size, via hole manufacturing method, and solder mask thickness. At the same time, the quality of the solder resist ink will also affect the surface treatment in the later stage.
