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Talking about the source of multilayer circuit board

Ώρα: 2015-08-05

The increased concentration of integrated circuit packages leads to a high concentration of interconnects, which need the use of multilayer boards.

Unpredictable design issues such as noise, stray capacitance, crosstalk, etc. occur in the layout of printed circuit boards. Therefore, printed circuit board design must focus on minimizing signal line length and avoiding parallel paths. Obviously, in single-sided pcb boards, even in double-sided boards, these requirements cannot be satisfactorily answered due to the limited number of cross-overs that can be achieved. In the case of a large number of interconnections and cross-over requirements, in order to achieve a satisfactory performance of the board, it is necessary to expand the board layer to more than two layers, and thus a multilayer circuit board has appeared.

The original intent of fabricating multilayer boards is therefore to provide more freedom in selecting suitable routing paths for complex and/or noise sensitive electronic circuits. The multilayer wiring board has at least three conductive layers, two of which are on the outer surface, and the remaining one is synthesized in the insulating board. The electrical connection between them is usually achieved by plated through holes in the cross section of the board. Unless otherwise stated, a multilayer printed circuit board, like a double panel, is typically a plated through hole plate.

A multi-substrate is fabricated by stacking two or more circuits on each other with reliable pre-set interconnections. Since drilling and plating have been completed before all the layers have been rolled together, this technique has violated the traditional manufacturing process from the beginning. The innermost two layers are made up of traditional double panels, while the outer layers are different, they are made up of separate single panels. Prior to rolling, the inner substrate will be drilled, through-hole plated, patterned transferred, developed, and etched. The outer layer to be drilled is a signal layer that is plated in such a way as to form a balanced copper ring at the inner edge of the through hole. The layers are then laminated together to form a multi-substrate that can be interconnected using wave soldering (between components).

Rolling may be done in a hydraulic press or in an overpressure chamber (autoclave). In the hydraulic press, the prepared material (for pressure stacking) is placed under cold or preheated pressure (high glass transition temperature material is placed at a temperature of 170-180 °C). The glass transition temperature is the amorphous region of the amorphous polymer (resin) or a portion of the crystalline polymer that changes from a rigid, relatively brittle state to a viscous, rubbery temperature.

Multi-layer boards are put into use in professional electronic equipment (computers, military equipment), especially in the case of weight and volume overload. However, this can only be achieved by increasing the cost of the multilayer circuit board in exchange for space increase and weight reduction. Multi-layer boards are also very useful in high-speed circuits, which provide designers of printed circuit boards with more than two layers of boards to route wires and provide large ground and power areas.

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