How to improve the quality of multi-layer board lamination?
B. To meet the requirements of PCB users, select the appropriate PP and CU foil configuration.
Customers’ requirements for PP are mainly expressed in terms of dielectric layer thickness, dielectric constant, characteristic impedance, withstand voltage, and smoothness of the laminate surface. Therefore, when choosing PP, you can choose according to the following aspects:
1. Resin can fill the gaps of the printed wires during lamination.
2. It can fully eliminate the air and volatile matter between the laminations during lamination.
3. It can provide the necessary dielectric layer thickness for the multilayer board.
4. It can ensure bonding strength and smooth appearance.
Based on many years of production experience, I think that PP can be configured with 7628, 7630 or 7628+1080, 7628+2116 when 4-layer laminates are laminated. The choice of PP for multi-layer boards with more than 6 layers is mainly 1080 or 2116, and 7628 is mainly used as PP to increase the thickness of the dielectric layer. At the same time, PP requires symmetrical placement to ensure mirror effect and prevent plate bending.
5. CU foil is mainly configured with different models according to the requirements of PCB users, and the quality of CU foil conforms to IPC standards.
C. Inner core board processing technology:
When multi-layer boards are laminated, the inner core board needs to be processed. The treatment process of the inner layer board includes black oxidation treatment and browning treatment. The oxidation treatment process is to form a black oxide film on the inner copper foil, and the thickness of the black oxide film is 0.25-4). 50mg/cm2. The browning process (horizontal browning) is to form an organic film on the inner copper foil. The functions of the inner layer board treatment process are:
1. Increase the contact surface of the inner copper foil and the resin to enhance the bonding force between the two.
2. Increase the effective wettability of the molten resin to the copper foil when the molten resin flows, so that the flowing resin has sufficient capacity to stretch into the oxide film, and show a strong grip after curing.
3. Prevent the decomposition of the curing agent dicyandiamide in the liquid resin at high temperatures—the effect of moisture on the copper surface.
4. Improve the acid resistance of the multilayer board during the wet process and prevent pink circles.
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