Circuit board open circuit is a problem that every PCB manufacturer often encounters. It has been plagued by production and quality management personnel. It causes replenishment due to insufficient shipments, delivery delays, and customer complaints that are more difficult for the industry to solve problem. The circuit board open circuit is actually the two points (point A and point B) that should be connected together, which are not connected together. The following editor will talk about the four common types of circuit board open circuits in detail.
Type of circuit board open circuit:
1.Repetitive open circuit
The characteristic of is that the same open circuit appears in the same place on almost every piece of pcb board, which is repeated multiple times, and the number of the exposed film is the same. The reason is that the exposure film is defective in the same position as the open circuit of the board. In this case, the exposure film must be scrapped, and the AOI inspection of the first and last board during exposure must be strengthened to ensure that the first pcb board is correct. exposure.
2. The gap is open
The characteristic of this kind of open circuit is that there is a gap in a wire, and the remaining line width due to the gap is less than 1/2 of the normal line width or equal to 1/2, usually the position is fixed, and the phenomenon is repeated many times. The reason for its formation is also that there is a defect on the exposed film, so there is a gap in the same position of the PCB board. The method suggested by the editor of Pate pcb is to change the exposure film and strengthen the AOI detection during the exposure process.
3. Vacuum open circuit
In a certain area, there are multiple wires appearing thinner and thinner (tapering), some are open, some are not open, but because the wires are too thin (less than the minimum line width required by the customer), they have to be scrapped . The reason for this defect is that the PCB manufacturer's exposure film and the dry film are not in close contact, and there is air in the middle, that is, the vacuum is not good after the exposure table is closed, and the vacuum does not meet the requirements, which causes the wire to change during exposure Thin or open.
4. Scratch to open the way
Its characteristic is that the traces of the wire scraped by external force can be clearly seen, which also causes an open circuit. The reason is due to improper operation (for example, the wrong method of picking the board during PCB production, etc.) or the machine causes the wire to be scratched to form an open circuit.
Due to the complicated causes of defects in the outer layer, many situations are possible, and I have not listed them here, but most of the defects appear on materials such as copper clad laminates, film sheets, and dry films, or in exposure , Development, etching and other processes are abnormal.