In PCBA assembly bolt defects found in the process of PCB, the common mainly has the following several forms.
Residual liquid corrosion caused by hole open features: the majority of the hole on the inner wall of the hole, black at the same time, the side of the wall was also corrosion without copper, most occurred in the process of assembly or in the process of long-term preservation.
Caused by interlayer strip hole features: open with the PCB substrate layer stripping and appear within the hole is open.
Defiled in blind holes open features: the blind hole between the coating and the blind hole connection plate resin or other debris and lead to poor contact and open circuit.
Solder corrosion caused by open circuit characteristics: PCB copper layer is very thin, when hot air leveling process or wave soldering copper wires are corrosion and open circuit.
Electrostatic damage suspected breakers characteristics: triangular scar is deeper, the part of the front end connects the slightly off form open.
Second, the formation mechanism of 1.
Residual liquid corrosion caused by hole open circuit in the process of PCB manufacturing residual liquid corrosion has not been cleared, enclosed within the hole, long-term corrosion hole wall, causing hole is open.
Interlayer strip hole caused by open circuit (
PCB base material moisture absorption.
HASL process temperature too high or too long.
PCBA assembly reflow welding when peak temperature too high or under the peak temperature soaking time is too long.
Defiled in blind holes open made a multilayer laminating process, the incomplete in laser drilling, clear, make the resin residues in blind holes of connection plate, resulting in blind holes open circuit.
Solder open this phenomenon caused by corrosion usually occurs in HASL process or wave soldering process.
Because the thickness of copper wires of the substrate design is too thin or wire width is too thin, under the high temperature of welding, the molten solder effect on corrosion of Cu will make copper conductor is thinner and more slender, once used in PCBA process is subjected to stress will open fracture.
Electrostatic damage suspected break formation reasons: figure 6 is a characteristic of the electrostatic damage triangular scar, tip slightly connection, once subjected to a stress will disconnect, that cause circuit.
Third, solution 1.
Residual liquid corrosion caused by the hole is open.
Feedback to suppliers, to strengthen the quality control in the process of PCB manufacture.
Caused by interlayer strip hole is open.
(1) to strengthen in the process of PCB substrate manufacturing moisture-proof measures, strict monitoring of process parameters (HASL
Temperature and time)
(2) pay attention to in the process of assembling PCB moisture-proof, and select suitable reflow welding peak temperature and under the peak temperature of immersion time, avoid high temperature or time is too long.
Defiled in blind holes.
PCB manufacturers should strengthen the process of PCB manufacturing process and the quality of supervision and control.
Solder corrosion caused by open circuit.
1) wiring design should avoid using, superfine copper wire is too thin.
(2) performing HASL and wave soldering process, should strengthen the control of operating temperature and time, avoid by all means high operating temperature and operating time is too long.
Electrostatic damage suspected breakers.
In PCB manufacture, storage, transportation and assembly process strict electrostatic protective measures must be enforced, fight electrostatic damage.
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