With the increasing complexity of electronic products, particularly in critical communication and technology applications, the demand for component reliability has risen significantly. The challenges of handling Moisture-Sensitive Devices (MSD) in electronic manufacturing are also becoming more prominent. The rapid development of packaging technologies, such as BGA (Ball Grid Array) and CSP (Chip-Scale Packaging), has further increased the sensitivity of components to moisture and reflow. As a result, effectively managing the moisture levels of these components to ensure their reliability during production and assembly has become a key challenge in the electronics manufacturing industry.
1. Dry Storage
During the production process, an adequate quantity of components is typically removed for surface-mount assembly. However, there are often leftover components, which are stored, along with trays and reels, until the next use after production halts. To ensure that the components remain dry, storage spaces are typically equipped with drying rooms or sealed bags containing desiccants.
A critical mistake that many manufacturers make is assuming that once components are placed in a dry environment, the “clock stops” for exposure time. In fact, this is contrary to the standards. The exposure time should continue to be tracked because once the components are exposed to the external environment for an extended period (e.g., one hour), they will absorb moisture, which gradually diffuses inside the packaging.
According to a study, PLCC components classified as level 5 (typically with a 48-hour production lifetime) were found to still exceed critical moisture levels after 16 hours of exposure, even when placed in dry storage and subjected to 70 hours of drying. Thus, even when stored in a dry environment, moisture absorption could still impact the components.
Nonetheless, placing components in dry storage is still an effective practice. In dry environments, the rate of moisture absorption slows down, and if stored long enough, the moisture can be eliminated. According to IPC/JEDEC standards, if the exposure time does not exceed 8 hours, storing the components in a dry environment for five times the original exposure time can reset the exposure time to zero.
2. Accurate Material Preparation
As mentioned earlier, one of the main causes of MSD failure is the removal of excess components during production. To avoid this, manufacturers should adhere to the principle of “minimum exposure time” by preparing only the number of components needed for the time required for assembly. If unused components remain, they should be returned to dry storage to restore them to dry conditions. This requires precise calculation, including considering the scrap factor for each MSD.
Another major benefit of accurate material preparation is avoiding the risks of mechanical damage or electrostatic discharge (ESD) caused by excessive handling. These factors can negatively impact product quality, yield rates, and costs. For example, when handling expensive and delicate ICs, they often need to be manually removed from plastic trays, increasing the likelihood of damage. Additionally, the length of tape reels must be accurately cut, which requires high technical skill and additional slitting operations to fit the feeders and transfer all component information from the original packaging to the new trays or reels.
3. Systematic Baking
Another method is systematically baking all remaining trays and reels after production. Although this is a relatively simple management process, it can lead to issues, especially with the latest IPC/JEDEC standards, which impose stricter requirements for baking conditions.
For instance, components packed in high-temperature trays need to be baked at 125°C for 48 hours, while components on reels and low-temperature trays require 68 days of baking at 40°C. However, this requirement is nearly impossible to meet for most companies.
According to the standards, unless otherwise specified, the baking cycle applies to components that have already been completed. If multiple baking cycles are needed, it is advisable to consult the supplier to ensure compliance.
4. Manual Time Recording
Many manufacturers require operators to manually record the date and time when components are removed from drying bags. While this is a good starting point, several issues still exist. Since these records rely on the calculation of dates and times, especially when dealing with large volumes of data, even well-trained operators may spend excessive time calculating and are prone to human errors. This not only increases the workload but can also affect the efficiency of the production line and the utilization of equipment.
Most MSDs are packaged in trays or reels, so exposure time is typically indicated on the labels. However, in the case of trays, it is not possible to attach these data directly to the container, making it difficult to ensure consistency between components and their corresponding records, especially when trays and reels are moved between pick-and-place machines and drying rooms.
Moreover, the record sheets must not only include the component number and sensitivity level but also ensure that this information remains traceable even after the packaging bags are discarded. The record sheet should indicate the date and time when the packaging bag was opened, as well as the times the components entered and exited the drying room or drying bags (potentially multiple times). These dynamic data add to the complexity of record-keeping and management.
Ending
In conclusion, the management of Moisture-Sensitive Devices (MSDs) is a critical aspect of electronics manufacturing that cannot be overlooked. From dry storage and material preparation to baking and exposure time recording, each step must be executed precisely to ensure the reliability of components. With the continued advancement of electronic component packaging technologies, MSD management will become increasingly complex. Therefore, adopting scientific and standardized management methods will help improve production efficiency and reduce failure rates.
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