Design (11) Software Design of the PCB automatic cabling system 1

PCB (Printed Circuit Board)

Auto-Wiring System Software

The type and density of Printed Circuit Board (PCB) components vary greatly depending on the type and density of the components on the receiving board. For printed circuit boards like computer boards, there are many ultra-large scale devices in flat packages like CPUs, as well as a large number of discrete devices such as resistors and capacitors, the design of such printed circuit boards is very cumbersome. It is only necessary to manually arrange the devices (layout) on them and manually participate in interactive wiring design, it is hard to imagine an automatic layout and wiring system to design them. However, this type of PCB, after all, is rare in the world. A lot of things are required to make printed circuit boards for small devices. There is only a clear small-scale integrated circuit on it. Such printed circuit boards can be automatically cabled. I will introduce this type of automatic cabling system for printed circuit boards. They are the same principle as the multi-cell Automatic Cabling System of Integrated Circuits. They are the last step of product (integrated circuit, or printed circuit board) design. Many types of designs have been performed before, including function design, logic design, Circuit design,Circuit(That is, the entire circuit is divided into several printed circuit boards, if the circuit is not big, do not need this step), the layout of components, and finally use Channel Wiring.

Before wiring the application channel software, determine which networks should be deployed in each channel in advance? This work is done by the overall wiring module. The overall wiring work is to allocate all the networks of the logically divided circuits to various channels so that they can be laid short, at the same time, the number of network connections in each channel may only be uniform, especially, not too many. According to this requirement, most of the cabling methods of the network are uniquely identified. For example, the connection lines between devices on both sides of the same channel are always allocated in this channel, and it is impossible to allocate connections to other channels. However, lines between devices in different rows and columns may have many different cabling methods to achieve the shortest goal. For example, the pin on the top of the device is connected to the pin on the top of the device on the fifth row and the second column) there can be four ways to achieve the shortest goal, that is, four ways to select which vertical channel to enter 1st rows from row 2nd. This randomness ensures that the number of network connections in each channel is roughly the same. PCB auto-Wiring SystemThe first thing to do is the overall wiring, and then call the channel wiring software for the internal wiring of the channel and the connection between each channel.

After my PCB auto-cabling system software was completed, except for the pcb I used for testing, only one graduate student actually used it, she made several PCB blocks for the pacemaker Tester (like 4-5 blocks), but the links between the PCB blocks do not need to be transferred through the PCB socket, but are directly connected by the wires. And myThe PCB auto-wiring system is designed for plug-ins with outgoing plug-in pins. to test whether the distribution function between the lead and plug-in pins is correct, I randomly specified more than 10 signal lines to be drawn out on her data of a medium-size PCB. After specifying the signal lines to be pulled out, I used the Automatic wiring system to perform Automatic wiring again, is the result after the Automatic wiring is completed. It can be seen that the distribution is completely correct and there is no error, but the 7th and 8th leads are almost identical. If an automatic detection module can be added for inspection of the line density, it is ideal to automatically segment the lead when detecting that the distance between the leads is too small or even touch each other, this work was not difficult because it was mainly to investigate the cabling near the plug-in, but it was not yet started. The PDP11 machines of DEC had been replaced by VAX/VMS machines, with a new job, we will not do it any more in the future.

Figure 1. PCBA medium-size Printed Circuit Board (Front) made by the automated cabling system for the pacemaker Tester)