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FOLYSKY（WuHan） LTD.
Double-layer alumina ceramic substrate refers to the copper on both sides, and there are metallized holes, that is, there is copper on both sides, and there is copper in the hole, for both sides of the ceramic substrate, there is copper in the hole is particularly important, because the earliest and most difficult thing is there is copper in the hole (how to have copper on the hole wall without copper), this is the most important basis for distinguishing between two sides and one side. But the fake double panel, only there is copper on both sides, but there is no copper in the hole, so there is no copper in the hole, but the ceramic substrate with holes on both sides is called the fake double panel, which looks like a double panel, and there is a difference between the actual and double sides! The two sides of this circuit board have wiring, but to use the wires on both sides, there must be an appropriate circuit connection between the two sides. This "bridge" between circuits is called a pilot hole. A pilot hole is a small hole filled with or coated with metal on the pcb, which can be connected with wires on both sides. Because the area of the double panel is twice as large as that of the single panel, the double panel solves the difficulty of the wiring interleaving in the single panel (it can be channeled through the hole to the other side), and it is more suitable for use in more complex circuits than the single panel.
Advantages (compared with single-layer board): easy wiring, simple, less wiring labor intensity, shorter line length.
The use of automatic wiring to design ceramic substrates is attractive. In most cases, automatic routing will not be a problem for purely digital circuits (especially low-frequency signals and low-density circuits). However, when you try to use the automatic routing tool provided by the routing software to route analog, mixed-signal or high-speed circuits, some problems may occur and may cause very serious circuit performance problems.
There are many things to consider about wiring, but the more troubling problem is the grounding method. If the grounding path starts at the upper level, the grounding of each device is connected to the ground wire by a cable at that level. For each device in the lower layer, it is connected to the upper layer by the perforation hole on the right side of the circuit board to form a ground loop. The immediate red flag that users see when checking the wiring indicates the presence of multiple ground loops. In addition, the lower ground loop is a horizontal place. The effect of digital switching δi/δt on the analog circuit can be reduced. However, it should be noted that these two double-layer boards have a ground floor at the lower level of the circuit board. This is designed so that engineers can quickly see the wiring when troubleshooting, which is often found on the demonstration and evaluation board of the device manufacturer. But a more typical approach is to lay ground on the upper layer of the circuit board to reduce electromagnetic interference.
Double alumina ceramic substrate - Design and wiring principles:
The ground wire of the double-layer alumina ceramic substrate is designed to form a grid-like enclosure frame, that is, there are more parallel ground wires on one side of the ceramic substrate, and the other side is the vertical ground wire of the copy plate, and then the metallized holes are connected at the place where they cross (the resistance of the holes is small).
In order to take into account that each IC chip should be equipped with a ground wire, often every 1 ~ 115cm cloth a ground wire, such a dense ground wire makes the area of the signal loop smaller, is conducive to reducing radiation. The design method of the ground network should be distributed before the signal line, otherwise it is difficult to achieve.
Double-layer alumina ceramic substrate signal cable wiring principles:
After the rational layout of the components of the double-layer alumina ceramic substrate is determined, the power cord of the ground grid copying board is designed first, and then the important lines are distributed -- sensitive lines and high-frequency lines, and the general lines are distributed -- low-frequency lines. The key lead is best to have an independent power supply, ground circuit, and the lead is very short, so sometimes a ground wire is placed on the side of the key line close to the signal line, so that it forms a minimum working loop.
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