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Problems And Solutions Of Substrate In PCBA Machining
Sep 28, 2017

Problems and Solutions of Substrate in PCBA Machining

PCBA processing in the process of the substrate may have the following problems:

First, a variety of soldering problems Symptom: cold solder joints or solder joints have blasting holes.

Inspection method: before welding and dip welding after the hole is often analyzed to find the place where the stress by copper, in addition, the raw materials for feed inspection.

possible reason:

Blasting holes or cold solder joints are seen after soldering operations. In many cases, poor copper plating followed by expansion during the soldering operation, resulting in holes or blasting holes in the metallized hole walls. If this is generated during the wet process, the absorbed volatiles are covered by the coating and then driven out of the brazing heating, which creates a spout or blasting hole.

Solution:

Try to eliminate copper stress. The expansion of the laminate in the z-axis or in the thickness direction is usually related to the material. It can cause the metal hole to break. Discuss with laminates manufacturers to get the z-axis expansion of smaller materials.

Second, the bond strength problem Symptom: In the dip welding operation process, the pad and wire detachment.

Inspection method: In the feed inspection, the full test, and carefully control all the wet process.

possible reason:

1. The wiping or wire separation during processing may be due to electroplating solution, solvent erosion, or copper stress during electroplating operations.

2. Punching, drilling, or perforation will cause the pad portion to be disengaged, which will become apparent in the hole metallization operation.

3. During wave soldering or manual soldering operations, wipes or wires are usually disengaged due to improper soldering or excessive temperature. Sometimes because the original bonding plate is not good or thermal stripping strength is not high, resulting in pad or wire from.

4. Sometimes the printed wiring of the printed circuit board causes the pad or wire to be disengaged in the same place.

5. During the soldering operation, the retention heat of the retention of the component causes the pad to disengage.

Solution:

1, to the laminate manufacturer a complete list of solvents and solutions used, including the processing time and temperature for each step. Analyze whether the plating process has occurred with copper stress and excessive thermal shock.

2, and earnestly follow the push of the mechanical processing methods. The metal hole is often analyzed, can control this problem.

3, most of the pad or wire disengagement is due to the entire operator due to strict requirements. The temperature check of the solder bath fails or prolongs the residence time in the solder bath. In the manual soldering operation, the pad disengagement is due to the use of improper electroplating of ferrochrome, and the failure to carry out professional training. Now some laminates manufacturers, used for rigorous soldering, have created laminates with high peel strength levels at high temperatures.

4, if the printed circuit board caused by the design of the detachment, occurred in the same place on each board; then the PCB must be redesigned. Often, this does happen at thick corners of thick copper foil or wires. Sometimes, long wires will also occur this phenomenon; this is because the thermal expansion coefficient of different reasons.

5, PCBA processing time. Under normal conditions, remove the heavy components from the entire printed circuit board or after the dip welding operation. Usually with a low wattage of the soldering iron carefully soldering, which compared with the component dip solder, the substrate material heat duration is shorter.

Third, the size of the excessive changes in the phenomenon of signs: after processing or soldering the substrate size beyond the tolerance or can not be aligned.

Inspection method: in the process of full quality control.

possible reason:

1. The texture direction of the paper-based material is not noticed, and the forward expansion is about half that of the transverse direction. And the substrate can not be restored to its original size after cooling.

2. If the local stress in the laminate is not released, it may cause irregular dimensional changes during processing.

Solution:

1, asked all the production staff often according to the same texture of the texture of the board material. If the size changes beyond the allowable range, consider changing the substrate.

2. Contact the manufacturer of the laminate to obtain advice on how to release the material stress before processing.