| Multi-layer laminated structure In the lamination structure of PCB boards, there are several important concepts to understand:PP (Prepreg): Prepreg is a semi-cured sheet material made by impregnating resin and curing it to an intermediate stage. It is primarily used as an adhesive and insulating material between the inner-layer conductive patterns of multilayer printed circuit boards. During the lamination process, the semi-cured epoxy resin is extruded, flows, and finally cures, bonding the multilayer circuit boards together to form a reliable insulating layer. In the PCB industry, Prepreg can be likened to “glue,” laminating multiple core boards together to form multilayer boards.Common PP types and thicknesses: 1080 (3.1 mil) 3313 (4.2 mil) 2116 (5.4 mil) 7628 (7.7 mil)Core (Core Board): A core is a rigid substrate with a certain thickness, coated with copper foil on both sides, used to form the basic structure of a PCB.Differences Between Prepreg and Core:Prepreg has a semi-solid texture, similar to cardboard; Core is a rigid material, similar to copper-clad laminate.Prepreg serves as an adhesive and insulator; Core is the foundational structural material of a PCB, with entirely different functions.Prepreg has some flexibility; Core cannot be bent.Prepreg itself is non-conductive; Core, coated with copper on both sides, serves as the conductive medium for printed circuit boards.The lamination materials for multilayer boards mainly include Prepreg and Core.Special Cases and Advanced PCB Requirements (e.g., custom stacking or impedance control as selected in “Custom Services & Advanced Options”): If you require custom stacking or impedance control, we will manufacture according to your requirements. After order confirmation, we will evaluate based on the stacking structure, materials, and impedance requirements to determine feasibility and communicate with you for confirmation. For flexible circuit board (FPC) stacking structures, please refer to the “FPC Stacking Structure” section.To meet customers’ demands for rigid PCBs, Superb has now added a variety of lamination structures (298 new types have been added and are continuously updated), greatly fulfilling the needs of product structure design and impedance control.  Signal Layer:Used for routing signal connections between electronic components.Power Layer: Provides the operating power required by the circuit.Ground Plane: Acts as a reference plane, provides a return path for signals, and offers electromagnetic shielding.Dielectric Layer: Insulating material between conductive layers, including core boards and prepreg.Important Principles for Rational Multilayer PCB Stack-up DesignProximity to Reference Planes: Signal layers should be as close as possible to adjacent ground or power layers to form a complete reference plane, reducing signal distortion and interference.Pairing of Power and Ground Layers: Placing power and ground layers adjacent to each other optimizes power decoupling, reduces impedance, and improves power integrity.Avoid Direct Adjacency of Signal Layers: Avoid direct adjacency between two signal layers whenever possible. If unavoidable, increase interlayer spacing or change signal routing directions (vertical or交叉) to reduce crosstalk.Symmetrical Structure: An ideal stack-up should be symmetrically arranged, typically using an even number of layers, to balance the mechanical and electrical performance of the PCB.Isolation of Digital and Analog Signals: Isolate the signals, power, and ground of digital and analog circuits through layering, using ground strips or isolation bands to reduce mutual interference.Special Considerations for High-Frequency Circuits: High-frequency circuits generate significant interference. It is best to place these signals in the inner signal layers between internal electrical layers, leveraging the shielding effect of the inner layers to reduce external interference.Steps for Multilayer PCB Stack-up DesignDetermine the Number and Types of Layers: Based on circuit complexity, component density, and performance requirements of critical signals, determine the number of signal, power, and ground layers needed.Assign Layer Sequence: Arrange the order of layers according to the principles mentioned above.Select Materials and Thicknesses: Choose appropriate substrate materials, copper foil, and dielectric materials, and determine the thickness of each layer, as this affects impedance and board thickness.Impedance Control and Via Design: Precisely control trace impedance based on high-speed signal requirements and design via structures reasonably.Consider Manufacturing and Cost: Ensure electrical performance is met while also considering the feasibility of manufacturing processes and cost. |
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