PCB board short circuit problem

The biggest cause of PCB short circuit is improper pad design. At this time, the circular pad can be changed to an elliptical shape to increase the distance between points, so as to prevent short circuits.

Inappropriate design of PCB board components will also cause short circuit of the circuit board, resulting in inoperability. If the pin of the SOIC is parallel to the tin wave, it is easy to cause a short circuit accident. In this case, the direction of the part can be modified to be perpendicular to the tin wave.

Another reason is that the PCB board is short-circuited, that is, the automatic plug-in unit is bent. As the IPC stipulates that the length of the wire is less than 2mm, when the bending angle is too large, the part is too large and it is easy to cause a short circuit. The solder joint is more than 2mm away from the circuit.

In addition to the above three reasons, there are some reasons that can cause short circuit failures on the PCB board. For example, the substrate hole is too large, the temperature of the tin furnace is too low, the solderability of the board surface is poor, the solder mask is invalid, and the board. Surface contamination etc. are common causes of failure. The engineer can eliminate and check the above causes and errors one by one.

4 ways to improve PCB fixed position short circuit

Short-circuit fixed short-circuit short-circuit improvement PCB is mainly caused by scratches on the film production line or garbage clogging on the coated screen. The coated anti-plating layer is exposed to copper and causes a short circuit in the PCB. The improvements are as follows:

The film on the film must not have problems such as trachoma, scratches, etc. When placed, the surface of the film should face up and should not rub against other objects. When copying the film, the film faces the surface of the film, and the appropriate film is loaded in time. Store in a film bag.

When the film is facing, it faces the PCB surface. When shooting film, pick up the diagonal with both hands. Do not touch other objects to avoid scratching the surface of the film. When the plate reaches a certain number, each film must stop aligning. Check or replace manually. Put it in a suitable film bag and store it.

Operators should not wear any decorations, such as rings, bracelets, etc. Nails should be trimmed and kept in the garden. No debris should be placed on the table top, and the table top should be clean and smooth.

Before making the screen version, it must be strictly checked to ensure that there are no problems. Screen version. When applying a wet film, it is usually necessary to check the paper to check whether there is a paper jam on the screen. If there is no interval printing, you should print an empty screen several times before printing so that the thinner in the ink can fully dissolve the solidified ink to ensure smooth leakage of the screen.

PCB board short circuit inspection method

If it is manual welding, it is necessary to develop good habits. First of all, visually inspect the PCB board before soldering, and use a multimeter to check whether the critical circuits (especially the power supply and ground) are short-circuited. Secondly, solder the chip every time. Use a multimeter to measure whether the power supply and ground are short-circuited. In addition, do not solder the iron when soldering. If solder is soldered to the solder feet of the chip (especially surface mount components), it is not easy to find.

Open the PCB on the computer, illuminate the short-circuit network, and then see if it is closest to it and the easiest to connect. Please pay special attention to the internal short circuit of the IC.

A short circuit was found. Take a board to cut the line (especially single/double board). After slicing, each part of the function block is energized separately, and some parts are not included.

Use short-circuit location analyzer, such as: Singapore PROTEQ CB2000 short-circuit tracker, Hong Kong Ganoderma QT50 short-circuit tracker, British POLAR ToneOhm950 multi-layer board short-circuit detector.

If there is a BGA chip, since all the solder joints are not covered by the chip, and it is a multi-layer board (more than 4 layers), it is best to use magnetic beads or 0 ohm to separate the power of each chip in the design. The resistor is connected so that when the power supply is short-circuited to the ground, the magnetic beads are detected and it is easy to locate a certain chip. Because BGA is difficult to solder, if it is not automatic soldering of the machine, the adjacent power and ground solder balls will be carefully short-circuited.

Be careful when soldering hours-large and small surface mount capacitors, especially power filter capacitors (103 or 104), they can easily cause a short circuit between the power supply and the ground. Of course, sometimes with bad luck, the capacitor itself will short-circuit, so the best way is to check the capacitor before soldering.