A lot of SMT processing manufacturers, in the electronic products printed circuit board of solder joints besides the fixed components, but also can be stable, reliable through a certain size of current.The quality of welding has a direct impact on the quality of electronic products, so what are the environment-related welding defects?
1, air bubble, SMT processing in the process of welding, welding components will be lead into the jack on the printed circuit board, after welding, being the root of the lead has a spitfire solder uplift, the center has a small hole, the hole may hide under the big hole, the welding defect called a bubble.
The reason for the hole is that the heat capacity of the copper foil on the printed circuit board is very large, although the welding is finished, but its back.
The surface is not yet cooled.Due to thermal inertia, the temperature is still rising, and the outside of the solder is solidified, and the gas inside the solder is generated.
Out of the hole.In addition, the stain on the welding disc, the oxidation treatment of the component leads is poor, the welding disc is too large, the element lead is too fine, the solder is too small, and the amount of rosin is too much, which can also cause this phenomenon.
2. Insufficient filler metal.When soldering with soldering iron, when the solder is too little, it will cause dampness. The solder can't form a smooth surface, and the welding defect is not enough.
One of the reasons for this defect is that the welding wire is premature.Second, the effective area of contact between electric soldering iron and solder is small, and the temperature is too high or the welding time is too long.The solder is not sufficient for this welding defect due to environmental deterioration which leads to poor conduction of the circuit.The hazard of this welding defect is that the mechanical strength of the solder joints is insufficient and can be resoldered by welding wire.
3. Overheating.This welding defect is characterized by white, non-metallic luster and rough surface.
The main reason of overheating is that the power of the soldering iron is too high, the soldering iron head is too hot, and the heating time is too long.Danger of overheating
The damage is easy to flake off and easy to reduce the mechanical strength between the solder joints.
4. Cold welding.In SMT processing and welding process, the solder is not fully solidified, moving conductor or wire welding components, the solder joint appearance gray lacklustre, the structure is loose, a tiny cracks, etc, this kind of welding defects called cold welding.
The reason for the cold welding is that the wires or wires of the welded components are removed too early, the welding components jitter, and the electric soldering iron power is not.
Enough.The hazard of cold welding is that the connection strength between solder joints is low and the conductivity is not good.Precautions against cold welding are avoided during welding.
The jitter of the wire or lead wire of the welded component.If there is doubt, it can be resoldered if necessary.
5. The copper foil is tilted up, peeling, and the welding disc is off.Copper foil from printed circuit board up, stripping, serious or even completely fracture, this phenomenon known as copper foil uplift, peeling.
The reason that the copper foil is raised and dissected is due to the failure to master the operational essentials in manual welding, and the overheating or part of the central heating circuit during welding.Or use a soldering iron head to pry the solder.The damage of copper foil uplift and stripping is a short circuit phenomenon.The measures to solve the peeling of copper foil, peeling off and welding disc are to strengthen training, repeat practice and master welding essentials.
6. After welding, when the welding spot is inspected (visually or with low magnification), there is a hole in the solder joint, which is called a pinhole.The reason for producing pinholes is mainly caused by the large gap between the hole and the lead.The damage of the needle hole is that the joint strength of the solder joints is low and the solder joints are vulnerable to corrosion.The measures to solve the pinhole are caused by the printed circuit board, and the hole should not be too large.
7, rosin welding, the needle between material and welding components lead form a layer of flux film and the dissolution of oxide or pollutants, formation of solder joint shape of bean curd, this phenomenon is called rosin welding, causes of rosin welding is a welding head move too early, the soldering flux failed to float to the surface.The hazard of rosin welding is the insufficient connection strength between the solder joints, and the failure of the circuit leads to the failure of the time.The measures to prevent rosin welding are not to add too much flux and the welding time should be appropriate.