I. Various soldering problems
Phenomenon signs: cold solder joint or tin solder joint has blasting holes.
Inspection methods: Before and after immersion welding, the holes are often dissected to find out where the copper is under stress. In addition, the raw materials are inspected by feeding.
Blasting holes or cold solder joints are seen after soldering operation. In many cases, poor copper plating and subsequent expansion occur during soldering operations, resulting in voids or blasting holes on the wall of metallized holes. If this is produced in the wet process, the absorbed volatile matter is covered up by the coating, and then driven out under the heating effect of dipping welding, this will produce nozzles or blasting holes.
Terms of settlement:
Eliminate copper stress as much as possible. The expansion of laminates in the z-axis or thickness direction is usually related to the material. It can cause fracture of metallization hole. Work with laminate manufacturers to obtain recommendations for materials with smaller z-axis expansion.
2. Adhesion Strength
Phenomenological Signs: During the dipping operation, the pad and wire are separated.
Inspection method: When the material is inspected, the full test is carried out and all wet processing processes are carefully controlled.
1. Disengagement of pad or wire during processing may be caused by stress of copper in electroplating solution, solvent immersion or during electroplating operation.
2. Punching, drilling or piercing will detach the pad part, which will become obvious in the hole metallization operation.
3. In the process of wave soldering or manual soldering, the disengagement of pad or wire is usually caused by improper soldering technology or excessive temperature. Sometimes, the bonding of the laminates is not good or the thermal peeling strength is not high, resulting in the detachment of the pads or wires.
4. Sometimes the design and wiring of PCB will cause the disengagement of pad or wire in the same place.
5. In the process of soldering operation, the heat absorbed by the elements will cause the disc to detach.
Terms of settlement:
- Give the laminate manufacturer a complete list of the solvents and solutions used, including the processing time and temperature at each step. The copper stress and excessive thermal shock in electroplating process were analyzed.
- Conscientiously abide by the method of mechanical processing that has been put aside. This problem can be controlled by the frequent analysis of metallized holes.
- Most disengagement of pads or wires is due to improper requirements for all operators. Failure of temperature inspection of solder tank or prolongation of residence time in solder tank will also lead to detachment. In manual tin soldering repair operation, pad detachment is probably due to improper use of wattage of ferrochromium and failure to carry out professional process training. Now some laminate manufacturers, for strict soldering use, have made laminates with high peeling strength at high temperatures.
- If the deviation caused by PCB design wiring occurs in the same place on each board, the PCB must be redesigned. Usually, this does happen at the right corner of a thick copper foil or wire. Sometimes, such a phenomenon occurs in long conductors; this is due to different thermal expansion coefficients.
- When designing PCB, remove the heavy components from the whole PCB, or install them after dip-welding operation, if possible. Usually a low wattage soldering iron is used to solder carefully. Compared with component dipping soldering, the heating duration of the substrate material is shorter.
3. The problem of excessive size change
Phenomenological Signs: After processing or soldering, the substrate size exceeds tolerance or cannot be aligned.
Inspection method: Quality control should be fully carried out in the process of processing.
1. The texture direction of paper-based materials is neglected, and the forward expansion is about half of the transverse direction. And the base material cannot be restored to its original size after cooling.
2. If the local stress in the laminate is not released, irregular size changes will sometimes occur in the process of processing.
Terms of settlement:
1. Encourage all production personnel to cut sheets in the same direction of texture. If the size change exceeds the allowable range, the substrates can be considered.
2. Contact the laminate manufacturer for advice on how to release material stress before processing.