PCBA Tech - smt chip processing plant: ways to reduce the failure of PBGA　

One, PBGA acceptance and storage

PBGA is a moisture-sensitive component. It is vacuum-packed when leaving the smt factory, but it is easy to damage its vacuum packaging during the transportation and turnover process, resulting in moisture and solder joint oxidation. Therefore, the packaging state of the component must be checked when the component is accepted in the factory. As an inspection item, strictly separate vacuum and non-vacuum-packaged components. Vacuum-packaged components should be stored in accordance with their storage requirements and used within the warranty period. Non-vacuum components should be stored in a low humidity cabinet as required to prevent PBGA Moisture absorption and oxidation of the pins. At the same time, it is controlled according to the principle of "first in, first out" to minimize the storage risk of components.

Second, the choice of PBGA dehumidification method smt chip processing plant

The damp PBGA must be dehumidified before production. BGA dehumidification usually has two types: low temperature dehumidification and high temperature dehumidification. Low temperature dehumidification uses low humidity cabinet dehumidification. Dehumidification is relatively time-consuming. It usually takes 192 hours under 5% humidity conditions. High temperature dehumidification uses oven dehumidification, and the dehumidification time is relatively short. It usually takes 4 hours at 125 degrees Celsius.

In actual production, the non-vacuum packaged components are dehumidified at high temperature and stored in a low-humidity cabinet to shorten the dehumidification cycle. For the PBGA whose humidity card shows that the humidity exceeds the standard, it is recommended to use low temperature dehumidification instead of high temperature dehumidification. Because high temperature dehumidification has a high temperature (greater than 100 degrees Celsius) and a fast speed, if the humidity of the component is high, it will be caused by the rapid vaporization of moisture. Cause component failure.

3. PBGA control at the production site

When PBGA is used at the production site, after unpacking the vacuum-packed components, the humidity card of the package must be cross-checked. When the humidity indicator on the humidity card exceeds the standard, it must not be used directly, and it must be dehumidified before use. When using non-vacuum packaged components at the production site, the humidity tracking card of the material must be checked to confirm the humidity status of the material. Non-vacuum packaged components without a humidity tracking card must not be used. At the same time, strictly control the use time and use environment of PBGA on site. The use environment should be controlled at about 25 degrees Celsius, and the humidity should be controlled within 40-60%. The use time of PBGA on site should be controlled within 24 hours, and PBGA beyond 24 hours must Perform dehumidification again.

4. Rework of PBGA

BGA rework station usually uses BGA rework station. The PCBA with PBGA attached to the production site is repaired. If it is placed for a long time, the PBGA is easy to absorb moisture, and the humidity state of the PBGA is difficult to judge. Therefore, before the PBGA is removed, the PCBA with the PBGA must be dehumidified to prevent the components from being removed. In the middle of failure and scrapping, the placement and reassembly of the BGA becomes futile.

Of course, there are many process links and reasons that cause BGA failure in the SMT process, such as ESD, reflow soldering, etc. To reduce the BGA failure in the SMT process, comprehensive control is required in many aspects. For PBGA, the process links related to the moisture absorption of components are often ignored in actual production, and the problems are relatively hidden, which often creates many obstacles for us to improve the process and improve the quality of the process. Therefore, the shortcomings of PBGA are sensitive to moisture. In the production process, starting from the above aspects and taking targeted effective countermeasures, it can better reduce the failure of PBGA, improve the quality of the PBGA process, and reduce production costs.