Causes of pcb pad shedding
Causes of pcb pad shedding
The solderability of PCBA in the production process is poor, and sometimes the phenomenon of PCBA pad shedding will occur. We may think directly about the problem of PCB production, but in fact the reason is not so simple. Next, the reason of PCBA pad fall off is analyzed.
1.When the temperature is too high, it is easy for the double panel or single panel to fall off the pad, and the multilayer board has a large area of floor covering, the heat dissipation is fast, the temperature needed for welding is also high, so it is not so easy to fall off.
2. A point of repeated welding will weld the pad off;
3. When manual welding, soldering iron temperature is too high to weld the pad;
4. Too much pressure on the pad and too long welding time will weld the pad out of the soldering iron head;
5. PCB board quality is too poor. In order to improve the solderability of PCBA pad and prevent the pad from falling off, it is necessary to improve the welding process and raise the welding level of employees.
PCB board and resistance film do not match, too many times of hot air straightening over tin, too high temperature of tin solution or preheating, too many times of welding will cause PCB pad to fall off. The temperature is too high. The general double panel or the single side board is easier to break off the pad, the multilayer board has the large area to spread the floor, dissipates the heat quickly, the welding need temperature is also high, also is not so easy to fall off. Also has the relation with the board quality.
Analysis of the reason why the pad is easy to fall off when the circuit board is welded
In the process of using circuit board, solder pad shedding often occurs, especially when the circuit board is repaired, when using electric iron, it is very easy to appear the phenomenon of solder pad falling off. In this paper, the circuit board factory makes some analysis on the reason of the solder pad falling off. Also take the corresponding countermeasures for the reasons.
Analysis of the reasons for the easily falling out of the pad during the welding of the circuit board:
1. Board quality problem. Because of the poor adhesion between copper foil and epoxy resin, even if the copper foil of large area copper foil is slightly heated or under mechanical external force, It is very easy to separate from epoxy resin, resulting in pad shedding and copper foil shedding.
2, The influence of storage conditions of PCB. Affected by weather or stored in wet place for a long time, the moisture absorption of PCB is too high. In order to achieve the ideal welding effect, the patch welding should compensate for the heat taken away by moisture volatilization. Welding temperature and time to be prolonged. Such welding conditions easily lead to copper foil and epoxy resin lamination.
3, Electric soldering iron, general circuit board adhesion can satisfy the welding pad, not falling, but the electronic products are generally possible to repair, repair is generally used electric iron welding repair, due to the local high temperature electric iron often reaches 300-400 degrees temperature, resulting in pad partial high temperature resin below the pad foil by high temperature drop, pad off. When the electric iron is easy to remove with electric iron head pad physical force, but also lead to pad off.
According to the condition that the pads are easy to fall off under the use condition, XinDa company will take the following aspects as far as possible to increase the number of solder joints to withstand welding times, so as to meet the needs of customers.
1: the copper clad laminate selects the base material from the manufacturer with the quality assurance. The glass fiber cloth selection and the pressing process of the common authentic copper clad laminate can ensure the welding resistance of the fabricated circuit board meets the customer's requirements.
2: the circuit board is packaged in vacuum before it leaves factory, and desiccant is placed to keep the circuit board in a dry state all the time. It creates conditions for reducing virtual welding and improving solderability.
3: in view of the thermal shock of the butt pad when the electric soldering iron is repaired, we try our best to increase the thickness of the pad copper foil by electroplating, so that when the soldering iron heats the pad, the thermal conductivity of the thick copper foil pad is obviously enhanced. Effective reduction of the local high temperature of the pad, at the same time, heat conduction makes the pad easier to remove, to achieve solderability of the pad.
FR4 94V0 Printed Circuit Board PCB，Multilayer PCB Design