PCB Technical - Analysis of abnormal PCB circuit board processing

In the process of PCB processing, it is inevitable that several defective products will be encountered, which may be caused by machine errors or human causes. For example, sometimes there will be an abnormal situation called a broken state. The cause depends on specific circumstances. detailed analysis.

If the rupture state is a point-like distribution rather than a whole circle of open circuit, it is called a point-shaped hole rupture, and some people call it a "wedge-shaped hole rupture". The common cause is the poor handling of the slag removal process. When PCB circuit boards are processed, the slag removal process will first be treated with a leavening agent, and then the strong oxidant "permanganate" will be corroded. This process will remove the slag and produce a microporous structure. The oxidant remaining after the removal process is removed by the reducing agent, and the typical formula is treated with an acidic liquid.

After the glue residue is processed, the problem of residual glue residue will no longer be seen, and everyone often neglects the monitoring of the reducing acid solution, which may allow the oxidant to remain on the wall of the hole.

After the circuit board enters the chemical copper process, the circuit board will undergo micro-etching treatment after the pore forming agent is processed. At this time, the residual oxidant is again soaked in acid to peel off the resin in the residual oxidant area, which is equivalent to destroying the pore forming agent.

The damaged pore walls will not react in the subsequent palladium colloid and chemical copper treatment, and these areas will show no copper precipitation phenomenon. If the foundation is not established, of course, the electroplated copper will not be able to cover it completely and cause dot-shaped holes to break. This kind of problem has occurred in many circuit board factories when they are processing circuit boards. Paying more attention to the monitoring of the potion in the reduction step of the de-smear process should be able to improve.

Every link in the PCB circuit board processing process requires us to strictly control, because sometimes chemical reactions will occur slowly in the corners that we do not pay attention to, thereby destroying the entire circuit. Everyone should be vigilant in this state of puncture.

The bare board (no parts on it) is also often referred to as "Printed Wiring Board (PWB)". The base plate of the board itself is made of materials that are insulated and heat-insulated, and not easy to bend. The small circuit material that can be seen on the surface is copper foil. The copper foil was originally covered on the entire board, but part of it was etched away during the manufacturing process, and the remaining part became a net-like small circuit. . These lines are called conductor patterns or wiring, and are used to provide circuit connections for parts on the PCB.

Usually the color of the PCB board is green or brown, which is the color of the solder mask. It is an insulating protective layer that can protect the copper wire, prevent short circuits caused by wave soldering, and save the amount of solder. A silk screen is also printed on the solder mask. Usually words and symbols (mostly white) are printed on this to mark the position of each part on the board. The screen printing surface is also called the legend surface.

When the final PCB product is made, integrated circuits, transistors, diodes, passive components (such as resistors, capacitors, connectors, etc.) and various other electronic parts will be mounted on it. Through the wire connection, the electronic signal connection can be formed and the application function can be formed.