The double-sided board is the middle layer of media, and both sides are routing layers. A multilayer board is a multilayer wiring layer, with a dielectric layer between each two layers. The dielectric layer can be made very thin. A multilayer circuit board has at least three conductive layers, two of which are on the outer surface, and the remaining layer is synthesized in an insulating board. The electrical connection between them is usually achieved through plated through holes on the cross section of the circuit board.
The circuit board determines the process difficulty and processing price according to the number of wiring surfaces. Ordinary circuit boards are divided into single-sided wiring and double-sided wiring, commonly known as single-sided and double-sided, but high-end electronic products are restricted by product space design factors. Outside the surface wiring, multiple layers of wiring can be stacked inside. During the production process, after each layer of wiring is made, it is positioned and pressed by optical equipment, so that the multilayer wiring is superimposed on a circuit board. Commonly known as multilayer circuit boards. Any circuit board greater than or equal to 2 layers can be called a multilayer circuit board. Multi-layer circuit boards can be further divided into multi-layer rigid circuit boards, multi-layer soft and hard circuit boards, and multi-layer soft-hard circuit boards.
Multi-substrates are manufactured by stacking two or more layers of circuits on top of each other with reliable, pre-set interconnections. Since drilling and plating were done before all the layers were rolled together, this technique violated the traditional manufacturing process from the beginning. The inner two layers are composed of traditional double-sided panels, while the outer layers are different. They are composed of independent single-sided panels. Before lamination, the inner substrate will be drilled, through-hole plated, pattern transferred, developed, and etched. The outer layer that is drilled is the signal layer, which is plated through in such a way that a uniform copper ring is formed on the inner edge of the via. The layers are then rolled together to form a multi-substrate, which can be interconnected (between components) using wave soldering.