Print the circuit board.
The painted circuit board is printed out with transfer paper, pay attention to the slippery side facing yourself, generally print two boards, that is, print two boards on a piece of paper. Select the best printing effect in the production of PCB circuit boards.
Cut the copper-clad plate, make the whole circuit board diagram
Copper clad plate, that is, a circuit board covered with copper film on both sides, cut the copper clad plate into the size of the PCB board, not too large, to save materials.
Pretreatment of copper clad plate
Use fine sandpaper to polish off the oxide layer on the surface of the copper-clad plate to ensure that the carbon powder on the thermal transfer paper can be firmly printed on the copper-clad plate when transferring the circuit board. The standard for polishing is that the surface of the board is bright and there is no obvious stain.
Transfer circuit board
The printed circuit board is cut to the appropriate size, the printed side of the circuit board is attached to the copper clad plate, and the copper clad plate is placed into the heat transfer machine after alignment, and the transfer paper must be ensured that there is no dislocation. Generally speaking, after 2-3 transfers, the circuit board can be firmly transferred to the copper-clad plate. The heat transfer machine has been preheated in advance, the temperature is set at 160-200 degrees Celsius, due to the high temperature, pay attention to safety when operating!
Corrosion circuit board, reflow welding machine
First check whether the circuit board transfer is complete, if there are a few no transfer place can be repaired with black oil pen. Then it can be corroded, and when the exposed copper film on the circuit board is completely corroded away, the circuit board is removed from the corrosive liquid and cleaned, so that a circuit board is corroded well. The corrosive liquid is composed of concentrated hydrochloric acid, concentrated hydrogen peroxide, water, the ratio is 1:2:3, in the preparation of corrosive liquid, first put water, and then add concentrated hydrochloric acid, concentrated hydrogen peroxide, if the operation of concentrated hydrochloric acid, concentrated hydrogen peroxide or corrosive liquid accidentally splashed on the skin or clothing should be cleaned with water in time, because the use of strong corrosive solution, the operation must pay attention to safety!
PCB board drilling
The PCB board is to insert electronic components, so it is necessary to drill the PCB board. Select different drilling needles according to the thickness of the electronic component pin. When using the drilling rig to drill, the circuit board must be stable, and the drilling rig speed cannot be opened too slowly. Please carefully watch the operation of the operator.
PCB circuit board pretreatment
After drilling, polish off the toner covered on the circuit board with fine sandpaper, and clean the PCB board with water. After the water is dried, apply the rosin water on the side with the line, in order to speed up the rosin solidification, we use a hot fan to heat the circuit board, and the rosin can solidify in only 2-3 minutes.
Weld electronic components
After welding the electronic components on the plate, power.
Analyze the design principle of mixed signal PCB board
The operation of analog circuits depends on continuous changes in current and voltage. The operation of a digital circuit depends on the detection of a high or low level at the receiving end according to a pre-defined voltage level or threshold, which is equivalent to determining the “true” or “false” logic state. Between the high and low levels of a digital circuit, there is a “gray” area where the digital circuit sometimes displays analog effects, such as when jumping from a low level to a high level (state), if the digital signal jumps fast enough, there will be overrush and backring reflections.
For modern board design, the concept of mixed-signal PCBS is ambiguous, because even in purely “digital” devices, there are still analog circuits and analog effects. Therefore, in the early stage of the design, simulation of the simulation effect must be carried out in order to reliably achieve strict timing allocation. In fact, in addition to communication products that must have the reliability to work for years without failure, simulation of simulation effects is particularly required in mass-produced low-cost/high-performance consumer products.
Another difficulty of modern mixed-signal PCB design is the increasing number of devices with different digital logic, such as GTL, LVTTL, LVCMOS and LVDS logic, each logic circuit has different logic thresholds and voltage swings, but these different logic thresholds and voltage swings must be designed together on a PCB. Here, you can master the strategies and techniques for success by thoroughly analyzing the layout and routing design of high-density, high-performance, mixed-signal PCBS.