Rigid PCB should pay attention to what?
Rigid PCB can be further divided into the following types:
1) Flexible insulating substrate to form a multi-layer PCB, the finished product is defined as flexible: This structure is usually a lot of single-sided or double-sided microstrip flexible PCB on both ends of the end together, but its center And are partially bonded together so as to have a high degree of flexibility. In order to have the desired electrical characteristics, such as characteristic impedance performance and the rigid PCB to which it is interconnected, each line layer of the rigid PCB part must be designed on the ground plane. In order to have a high degree of flexibility, a thin, suitable coating, such as polyimide, may be used on the conductor layer instead of a thicker layer of overcoat. The metallization hole enables the desired interconnection between the z-plane between the flexible circuit layers. This rigid PCB is best suited for applications requiring flexibility, high reliability and high density.
2) on the soft insulating substrate to form a multi-layer PCB, the end of the finished product can be deflected: such rigid PCB is a soft insulating material, such as polyimide film, laminated into a multi-layer board. Lost inherent flexibility after lamination. This type of soft PCB is used when the design requires the maximum use of the insulating properties of the film, such as low dielectric constant, uniform thickness of the medium, lighter weight and continuous processing. For example, a multilayer PCB made of polyimide film insulating material is about one-third lighter than the weight of a rigid glass cloth rigid PCB.
3) A multilayer PCB is formed on a flexible insulating substrate, and its finished product must be shaped, rather than continuously bendable: such Rigid PCB are made of soft insulating material. Although it is made of soft material, it is required to have a thick conductor, or for the desired impedance or capacitance, for the required conductor resistance due to electrical design limitations, requiring thicker between the signal layer and the ground layer Of the insulation isolation, therefore, in the finished product application it has been formed. The term & quot; moldable & quot; is defined as a rigid PCB component that has the ability to make the desired shape and can no longer be flexed in the application. In the avionics unit internal wiring applications. In this case, it is desirable that the conductor resistance of the stripline or three-dimensional space design is low, the capacitance coupling or the circuit noise is extremely small, and can be smoothly bent at 90 ° at the interconnection end. The rigid PCB made of polyimide film material achieves this cabling task. Because polyimide films are resistant to high temperatures, are flexible and have good electrical and mechanical properties. In order to achieve all the interconnections of the cross-section of the part, the traces are further divided into a plurality of multilayer flexible line components and joined together with an adhesive tape to form a printed circuit bundle.
Rigid - Flexible multilayer PCB
This type is usually on one or two Rigid PCB and contains a flexible PCB that is indispensable to form the whole. The flexible PCB layer is laminated in a rigid multilayer PCB, which is intended to have special electrical requirements or to extend beyond the rigid circuit to the DP-Z plane circuit. These products are widely used in electronic equipment that compresses weight and volume as critical and assures high reliability, high density assembly and excellent electrical characteristics.
Rigid - soft multilayer PCB can also be a number of single-sided or double-sided soft PCB end of the adhesive together to become a rigid part, and the middle is not bonded into a soft part of the rigid part of the Z side with metal holes even. The flexible circuit can be laminated to a rigid multilayer board. This type of PCB is increasingly used in applications requiring ultra-high packaging density, excellent electrical characteristics, high reliability and strict limits of the volume of the occasion.
There has been a series of hybrid rigid PCB components designed for use in military avionics, where weight and volume are of paramount importance. In order to meet the specified weight and volume limits, the internal package density must be extremely high. In addition to the high circuit density, in order to minimize crosstalk and noise, all signal transmission lines must be shielded. To use shielded separate wires, it is virtually impossible to economically package into the system. In this way, a mixed multi-layer is used
Soft PCB to achieve its interconnection. This part contains the shielded signal line in the flat ribbon soft PCB, which is a necessary part of the rigid PCB. At a relatively high level of operation, the PCB is formed with a 90 ° S-bend when it is manufactured, providing a z-plane interconnect and, in the presence of x, y and z plane vibrational stresses, To eliminate stress - strain.