PCB Technical - PCB proofing and PCB processing etching process

Make sure that the signal line is as short as possible for PCB proofing.
When the length of the signal wire is greater than 300mm, a ground wire must be laid in parallel.
Ensure that the loop area between the signal line and the corresponding loop is as small as possible. For long signal lines, the position of the signal line and the ground line must be exchanged every few centimeters to reduce the loop area.
Drive signals from the center of the network into multiple receiving circuits.
Ensure that the loop area between the power supply and the ground is as small as possible, and place a high-frequency capacitor close to each power supply pin of the integrated circuit chip.
Place a high-frequency bypass capacitor within 80mm of each connector.
Where possible, fill the unused area with land, and connect the filling grounds of all layers at intervals of 60mm.
Ensure that the two opposite end positions of an arbitrarily large ground filling area (approximately greater than 25mm*6mm) are connected to the ground.
When the length of the opening on the power supply or ground plane exceeds 8mm, use a narrow line to connect the two sides of the opening.
The reset line, interrupt signal line or edge trigger signal line cannot be arranged close to the edge of the PCB.
Connect the mounting holes to the circuit common ground, or isolate them.
(1) When the metal bracket must be used with a metal shielding device or a chassis, a zero-ohm resistance should be used to realize the connection.
(2) Determine the size of the mounting hole to achieve reliable installation of metal or plastic brackets. Use large pads on the top and bottom layers of the mounting holes, and no solder resist can be used on the bottom pads, and ensure that the bottom pads do not use wave soldering technology. welding.
The protected signal line and the unprotected signal line cannot be arranged in parallel.
PCB proofing should pay special attention to the wiring of reset, interrupt and control signal lines.
(1) High frequency filtering should be used.
(2) Keep away from input and output circuits.
(3) Keep away from the edge of the PCB board.

The PCB proofing should be inserted into the case, not installed in the opening position or internal seam.
Pay attention to the wiring under the magnetic beads, between the pads and the signal lines that may be in contact with the magnetic beads. Some magnetic beads have very good conductivity and may produce unexpected conductive paths.
If there are several PCB boards in a chassis or motherboard, the PCB board most sensitive to static electricity should be placed in the middle.
PCB etching regarding the upper and lower board surfaces, the etching state of the leading edge and the trailing edge are different
A lot of problems related to etching quality are concentrated on the etched part of the upper plate surface. It is very important to understand this. These problems come from the influence of the glue-like clumps produced by the etchant on the upper surface of the printed circuit board. The accumulation of colloidal slabstock on the copper surface affects the spraying force on the one hand, and on the other hand prevents the replenishment of fresh etching solution, resulting in a decrease in the etching speed. It is precisely because of the formation and accumulation of colloidal slabs that the degree of etching of the upper and lower patterns of the board is different. This also makes the first part of the board in the etching machine easy to be etched completely or to cause over-corrosion, because the accumulation has not yet formed at that time, and the etching speed is faster. On the contrary, the part that enters behind the board has already formed when it enters, and slows down its etching speed.
Maintenance of PCB etching equipment
The most critical factor in the maintenance of etching equipment is to ensure that the nozzle is clean and free of obstructions to make the jet unobstructed. Clogging or slagging will impact the layout under the action of jet pressure. If the nozzle is not clean, it will cause uneven etching and scrap the entire PCB.
Obviously, the maintenance of the equipment is the replacement of broken and worn parts, including replacement of nozzles. The nozzles also have the problem of wear. In addition, the more critical issue is to keep the etching machine free of slagging. In many cases, there will be slagging accumulation. Too much slagging accumulation may even affect the chemical balance of the etching solution. Similarly, if there is excessive chemical imbalance in the etching solution, slagging will become more serious. The problem of slag accumulation cannot be overemphasized. Once a large amount of slagging occurs suddenly in the etching solution, it is usually a signal that there is a problem with the balance of the solution. This should be done with strong hydrochloric acid for proper cleaning or supplementation of the solution.