PCB 多层板制造中如何提高层压品质工
First, the design meets the laminate requirements of the inner core.
Due to the progressive development of laminating machine technology, hot press from the previous non-vacuum hot press to the current vacuum hot press, hot pressing process in a closed system, can not see, touch. Therefore, before laminating the inner plate to be reasonable design, here to provide some reference requirements:
1, according to the total thickness of the multilayer board core board thickness selection, the core thickness of the same, the deviation is small, the same direction of cutting the warp and weft, especially 6 or more plywood, the inner core of the warp and weft direction must be consistent, namely The direction and the direction of overlap, the latitude and the latitude direction of the overlap, to prevent unnecessary bending plate.
2, the core board dimensions and effective spacing between the unit must have a certain distance, that is, the distance between the effective unit to the edge of the plate to be as long as possible without leaving a waste of materials under the premise of leaving a larger space, the general requirements of four-layer board spacing greater than 10mm , Six-layer board spacing greater than 15mm, the higher the number of layers, the greater the spacing.
3, Positioning hole design, in order to reduce the deviation between layers and layers, so in multi-layer positioning hole design should pay attention to: 4-layer holes only need to design more than 3 holes for drilling. More than 6 layers of multi-layer board in addition to the need to design holes with holes outside the design layer and layer overlap positioning rivet holes more than 5 and rivets with tool plate positioning holes more than 5. However, the design of positioning holes, rivet holes, tool holes are generally the higher the number of layers, the corresponding number of holes designed to be more, and the location as the edge. The main purpose is to reduce the alignment deviation between the layers and leave more space for manufacturing. Target design to try to meet the target automatically identify the target-shaped requirements, the general design of a complete circle or concentric circles.
4, the inner core requirements without open, short, open circuit, no oxidation, clean board, no residual film.
Second, to meet the requirements of PCB users, select the appropriate PP, CU foil configuration.
Customer requirements for PP mainly in the dielectric layer thickness, dielectric constant, the characteristic impedance, withstanding voltage, the appearance of the smoothness of the laminate and other aspects of the requirements, so the choice of PP can be selected according to the following aspects:
1, Resin can be filled when printed laminate conductor gap.
2, can fully eliminate lamination in the laminated air and volatiles.
3, can provide the necessary multilayer thickness of the dielectric layer.
4, to ensure bond strength and smooth appearance.
5, CU foil mainly according to PCB user requirements, respectively, the configuration of different models, CU foil quality in line with IPC standards.
Third, the inner core processing technology
Multilayer laminates, the inner core to be processed. The treatment process of the inner plate has a black oxidation treatment process and a browning treatment process. The oxidation treatment process forms a black oxide film on the inner layer copper foil, and the black oxide film has a thickness of 0.25 to 4). 50mg / cm2. Browning process (horizontal browning) is the formation of a layer of organic film on the inner copper foil. Inner plate processing technology role:
1, increase the inner surface of the copper foil in contact with the resin, so that the binding force between the two enhanced.
2, Increase the effective wetting of the copper foil when the flow of the molten resin, so that the flow of the resin has the full ability to stretch into the oxide film, showing strong grip after curing.
3, blocking high temperature liquid resin curing agent dicyandiamide decomposition of a water on the copper surface.
4, so that the multi-layer process in the wet process to improve acid resistance, prevention of pink circle. Fourth, the lamination parameters of organic matching Multilayer laminates control the lamination parameters mainly refers to the laminated "temperature, time, pressure," the three organic match.
(1): Temperature, several temperature parameters in the lamination process is more important. That is, the melting temperature of the resin, the curing temperature of the resin, the setting temperature of the hot plate, the actual temperature of the material and the speed of the temperature rise. The melting temperature begins to melt when the temperature is raised to 70 ° C. It is because of the further increase in temperature that the resin melts further and begins to flow. In the temperature of 70-140 ℃ during this period, the resin is easy to fluid, it is precisely because of the resin flow, to ensure the resin filling, moist. With the gradual increase in temperature, the fluidity of the resin has experienced a small to large, and then to small, and finally when the temperature reaches 160-170 ℃, the fluidity of the resin is 0, when the temperature is called the curing temperature. In order to make the resin better gelatinous and wetting, it is very important to control the heating rate. The heating rate is the actualization of the laminating temperature, that is, when the temperature rises to a high level. The control of heating rate is an important parameter of laminate quality, and the heating rate is generally controlled to 2-4 ℃ / MIN. Heating rate and PP different models, such as the number is closely related. 7628PP heating rate can be a little faster that is 2-4 ℃ / min, 1080,2116PP heating rate control at 1.5-2 ℃ / MIN at the same time the number of PP, the heating rate can not be too fast, because the heating rate too fast, PP Poor wettability, resin flow, time is short, easy to cause skateboarding, affecting the quality of lamination. Hot plate temperature mainly depends on the steel plate, steel, bovine paper and other heat transfer, usually 180-200 ℃.
(2): The time and time parameters are mainly the control of the timing of laminating and pressurizing, the controlling of the timing of warming up, the gelation time and the like. The second lamination and multi-stage lamination, controlling the timing of the main pressure, determining the primary pressure to the main pressure conversion time is the key to controlling the quality of the lamination. If the main pressure is applied too early, it will lead to resin extrusion, too much flow of glue, resulting in laminate lack of plastic, thin plate, and even skateboarding and other undesirable phenomena. If the application of pressure too late, it will result in laminated bonding interface is not strong, empty, or bubbles and other defects.
3: Pressure, laminate pressure is the size of the resin can fill the gap between the layers of exhaust gas and volatiles layer as the basic principle. As the hot press is divided into non-vacuum press and vacuum hot press, so there is a period of pressure from the pressure. Sec pressure and multi-stage pressure several ways. General non-vacuum press with general pressure and Sec pressure. Vacuum machine uses two sections of pressure and multi-stage pressure. For high, fine, multi-layer multi-stage pressure is usually used. Pressure is generally based on pressure P P suppliers to determine the pressure parameters, usually 15-35kg / cm2.